Comets Can't Explain Weird 'Alien Megastructure' Star After All (newscientist.com)

schwit1 sends the latest news about KIC 8462852, the star that that led many to learn what a Dyson Sphere is. New Scientist reports: "The weirdest star in the cosmos just got a lot weirder. And yes, it might be aliens. Known as KIC 8462852, or Tabby's star, it has been baffling astronomers for the past few months after a team of researchers noticed its light seemed to be dipping in brightness in bizarre ways. Proposed explanations ranged from a cloud of comets to orbiting 'alien megastructures'. Now an analysis of historical observations reveals the star has been gradually dimming for over a century, leaving everyone scratching their heads as to the cause. Bradley Schaefer of Louisiana State University saw the same century-long dimming in his manual readings, and calculated that it would require 648,000 comets, each 200 kilometres wide, to have passed by the star — completely implausible, he says. 'The comet-family idea was reasonably put forth as the best of the proposals, even while acknowledging that they all were a poor lot,' he says. 'But now we have a refutation of the idea, and indeed, of all published ideas.' 'This presents some trouble for the comet hypothesis,' says Boyajian. 'We need more data through continuous monitoring to figure out what is going on.' What about those alien megastructures? Schafer is unconvinced. 'The alien-megastructure idea runs wrong with my new observations,' he says, as he thinks even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century. What's more, such an object should radiate light absorbed from the star as heat, but the infrared signal from Tabby's star appears normal, he says."

Comments

Now...

[Anonymous Coward]

I'm not saying it's aliens but it's aliens!

Re:Now...

[Applehu Akbar]

I would check other stars close to this object for evidence of large defensive structures.

Re:Now...

[Anonymous Coward]

Schaefer makes two VERY large assumptions in discounting the alien megastructure theory. The first being that the energy storage inefficiency would be large enough to create large amounts of infrared light, and the second being that the megastructures in question would have been initially constructed around the star, instead of being moved into place afterwards.

Re:Now...

[Anonymous Coward]

other stars close prob already been dyson'd

i think the prudent thing to do would be to send nukes now before it's too late

Re: Now...

[guruevi]

That and that if you're capable of doing this you can't do 20% of a star in 100y time. Look at the advances we've made in computer and building technology, even space tech in the last century and we as a species are just starting. Give us a thousand years at the current rate of progress and if we haven't killed ourselves we can probably strip mine a planet like Mars to build our energy structures.

Re: Now...

[gl4ss]

but you would need to mine 100 planets like mars in the time, kind of.

Re: Now...

[tysonedwards]

Our star loses one billion kilograms per second... While that may sound like a lot... It's still only an earth mass every 150 million years. The math doesn't work out. Additional matter would need to come from somewhere.

Re:Now...

[Z00L00K]

If you exclude all other possible reasons it may be something there.

But what about a cloud obscuring the vision?

Re: Now...

[WarJolt]

It's been excluded too. Clearly it's far more likely that it's a alien megastructure.

Re: Now...

[ShanghaiBill]

but you would need to mine 100 planets like mars in the time, kind of.

Nope. Just one is enough. To build a Dyson sphere at one AU (the distance of the earth from the sun), or about 150,000,000 km, the sphere would have an area of 4 * pi * r^2 = 9e23 m^2. The mass of Mars is 6.39 × 10^23 kg. So if you build the sphere with a mass of about 1 kg / meter squared, you could do it with just a little over one Mars sized planet.

Re: Now...

[Chrontius]

If we're strip-mining Jupiter, that's peanuts. Why Jupiter? We might want some fusion reactors for localized or pulsed power, or rocket fuel, and solar panels are lousy at providing both.

Re:Now...

[wierd_w]

There's another possibility that's just as far out, and would explain the missing IR.

It's a traffic hub for small FTL ships.

If they use something like an alcubierre metric based warp drive, then the gravitational fields around the craft will scatter the star's light into vectors that are no longer straight lines away from the star. This will result in the star's effective brightness being reduced.

Get enough of them going in and out of the system routinely, and you will get the observed phenomenon.

To me, the obvious thing to do is look for gravitational waves coming from the system. If you can't catch their broadcasts (because they use something other than open channel radio), then look for the propwash.

Re: Now...

[jpatters]

The solar wind is going out at all directions. You would have to first build a Dyson Sphere of solar wind harvesters in order to implement that idea.

Re:Now...

[Anonymous Coward]

Or... A massive asteroid belt.

Re: Now...

[Anonymous Coward]

A "cloud" is not really excluded.
A cloud near the dimming star is excluded, because it'd mean more IR (just like a Dyson sphere would).

However, a cloud might be drifting in midway between earth and this star. The result of that could very well be 20% dimming over 100 years - and no extra IR. No IR because the in-between cloud is too far away from the star to be heated up.

As for the faster irregular variations, it might be 2 or more darker companions stars close to one bright star. The three-body problem is unsolved, and simulations show irregular unpredictable orbits when 3 (or more) stars orbit all with about the same distance from a common center. You could get irregular blinking as the bright star sometimes pass behind one darker companion, and sometimes behind two others.

Re: Now...

[Anonymous Coward]

I see you've reinvented scrith.

Re: Now...

[TheRaven64]

That doesn't really follow. If you wanted to collect solar wind, you'd need to condense it, which you'd do by large magnetic fields to funnel it into a collector. A relatively small collector would collect the hydrogen from a very large area. Of course, if you're able to create strong and structured magnetic fields over such an area, you could probably also skim hydrogen from the sun a bit more aggressively.

Re: Now...

[Anonymous Coward]

Um, while our information processing technology has improved, we don't even have the Concorde anymore. So I'd really like to know why people conflate the two. Our cars and planes certainly don't fly hundreds of times faster on a teaspoon of kerosene, do they?

In a thousand years, we'll all be right here. And it will look as different as a thousand years *ago*. In other words, we'll be right here, with most of the same problems, same people, same religions, same politics, same (in)justice.

Get over it. Our great technological progress era is coming to a close.

Re: Now...

[maeka]

If you had direct energy to matter conversion you'd have the easier matter to energy conversion down pat and converting Mars to energy would be a more efficient use than using it to build a Dyson sphere.

Re: Now...

[Anonymous Coward]

Ah, I see you're grasping at some way to refute my argument with word play. "We", of course, is the human species. A thousand years is not enough for evolution to make much of a dent, "we" means if we could travel in time we'd fit right in. Now a million years ago there was no human race, and in another million there won't be one either. Evolution is still happening.

It's just funny to read people charting out the future of the human species in space based on a few year's progress of our computers while everything else stands still.

Re: Now...

[Anonymous Coward]

Fair enough, but building the Dyson sphere may generate more pork for your home state.

Re:Now...

[dreamchaser]

I know you're joking, but sending nukes to attack a civilization with engineering advanced enough to build a Dyson Sphere or other mega-structures would probably be like ants developing the technology to throw grains of sand at relatively low velocities at us.

Re:Now...

[gtall]

Yep, cue the Greek guy with the electric hair, he'd have no problems explaining this.

Re: Now...

[tburkhol]

So if you build the sphere with a mass of about 1 kg / meter squared, you could do it with just a little over one Mars sized planet.

You describe a paper globe about 4mm thick, or maybe more practically (since much of a rocky planet is silicates), a glass sphere 400 um thick. I can't imagine what one could do with that structure. (of course, I can't imagine how one would construct a Dyson sphere, so perhaps criticizing the structural integrity of that sphere is irrelevant.)

Re: Now...

[pscottdv]

You should make contact with the astronomers that wrote the paper and tell them your great ideas. I'm sure they haven't thought of them.

Re: Now...

[Phics]

If you had matter to energy conversion down pat, I doubt the locals on Mars would approve of you converting their home into a Dyson sphere.

Re: Now...

[Phics]

Err... an energy source.

That corrected, I wonder how hard it would be for a civilization that advanced to manipulate existing structures into a Dyson sphere.... I.E., collecting "nearby" debris such as asteroids, moons, or even planets, and assembling them like LEGOs to build an infrastructure of some kind around a star in some sort of grid or lattice.

Re: Now...

[wierd_w]

Oh my, I have been insulted by an anonymous coward. Whatever shall I do? /s

go invent conspiracy theories about "space nutters" somewhere else, dumbass. The argument that there are no aliens out there loses steam daily as missions like Kepler give statistical samplings of planetary system compositions. The suggestion of it being from FTL use is less convoluted than the suggestion that it is a Dyson swarm, because FTL is going to be an essential technology to construct a dyson swarm. I threw it out there, not because I believed it was true, but because it was a similarly improbable reasoning for the observed phenomenon, and suggested a means to disprove it.

That's significantly better than jumping whole horse on the ad hominem fun ride, like you just did.

Catch you later AC.

Re: Now...

[arth1]

Ah, I see you're grasping at some way to refute my argument with word play. "We", of course, is the human species. A thousand years is not enough for evolution to make much of a dent, "we" means if we could travel in time we'd fit right in. Now a million years ago there was no human race, and in another million there won't be one either. Evolution is still happening.

Is it, though? Haven't we largely thwarted evolution, and replaced it with survival of everyone we like? We do our utmost to remove any evolutionary pressure, and save people who would have died if it weren't for our own direct intervention. We spend resources on fertility treatments. We do as much as we can to level the playing field and avoid evolutionary competition.

A thousand years of devolution is more than enough to make a rather large difference.

Re: Now...

[Anonymous Coward]

Idiocrazy was not a movie but documentary about the future - sadly.

Re:Now...

[Culture20]

I would like to see ants do that and might try to offer them tips on improvement in weapon design and other areas. But if they shot sand in my eyes, I might accidentally step on them while stumbling blindly.

Re:Now...

[silentcoder]

Considering that even if we could launch nukes at light-speed (Which we can't - nothing remotely close) they wouldn't get there for a millenium and a half - it's already too late.

Whatever it is we're witnessing now, actually happened around 600AD - when we were busy trying to invent a better horse-collar.

Re: Now...

[silentcoder]

> A thousand years is not enough for evolution to make much of a dent

Cultures evolve much, much faster than human bodies do - and even they are several orders of magnitude slower than the rate of evolution of a neural network - like the ones we get born with between our ears.
Also - you massively underestimate just how different our world really is compared to the one from a thousand years ago.

For starters, a thousand years ago you would probably be dead - seeing as child mortality rates were so much higher, and even if you survived childhood, you would probably die young.
The current population of earth could literally not have existed a thousand years ago - the vast majority would have been wiped out by a mass famine, the farming techniques and technologies needed to feed 7 billion people simply did not exist, hell we couldn't have fed 2 billion back then.

Re:Now...

[silentcoder]

Except of course we don't actually have a confirmed way to detect gravitational waves yet. Now there are hopeful rumbles that we may have a confirmation published in the near future but it could just as easily be a "sorry, we failed" at this stage, the scientists are being very hush hush about the data while they are busy checking it.

Re: Now...

[radiumsoup]

that's assuming 100% coverage. Since we're seeing variability, it follows that the structure of any presumed Dyson object at this location either hasn't reached "sphere" stage or isn't designed to. If the latter, then a "ring" or "swarm" style structure would be much thicker and more useful as a substrate. While I don't think Dyson structures are necessarily feasible in practical terms, in theoretical terms the heat management of a structure that can turn panels away from the star would be more efficient, so I tend to fall on the side of "spheres are impractical, rings make more sense"

Re: Now...

[ShanghaiBill]

I see you've reinvented scrith.

A Dyson Sphere is NOT a sphere with a continuous surface. It is a swarm of independently orbiting satellites. No special scrith-like materials are needed.

Re: Now...

[Impy the Impiuos Imp]

Well, this is less about super nano robot tech than about the energy required itself. As with fears of a grey goo problem, the energy simply isn't there for a quick rollover.

That much molecular change should make it glow in the IR pretty brightly.

Re: Now...

[Impy the Impiuos Imp]

I feel certain some people, be it in cryo, or frozen up a mountain or in Antarctica, will remain so long afted the nanotech exists to repair individual cells.

So, yes. Some probably will.

Re: Now...

[LynnwoodRooster]

Doesn't that depend upon how thick the construction is? For example, you could cover all of Manhattan Island with a heat-reflecting Mylar film (2 microns thick), and it would require the mass equivalent to about 850 barrels of crude oil. Or about 1/12,000th of Saudi Arabia's daily average petroleum output. Not much at all, relatively speaking, to cover 86 square kilometers with a film that would reflect ~80% of the radiated energy it encounters. To cover a sphere all the way around the sun, at a distance of the Earth (93 million kilometers) would take only about 30 years of the world's total oil production. And you'd have a film that would make our sun dim - to distant observers - by about 80%.

Re: Now...

[vivian]

My current favourite crack-pot theory is Its a star encompassing solar farm being built to power a galactic wide AI. About 90% of start have been covered now - we call all those ones 'dark matter'

Re:Now...

[Immerman]

Except a nuke would probably still be pretty destructive unless they had defensive systems in place. So more like if ants started throwing firecrackers. Not a serious threat under most circumstances, but annoying enough that you might decide to eliminate the problem by some means.

Re: Now...

[Anonymous Cow Ward]

Let's build a Dyson sphere so we can build another, slightly better Dyson sphere around that one!

Re: Now...

[Anonymous Cow Ward]

Interesting, I didn't know a swarm was also considered a Dyson sphere. However, the Wikipedia article you cited does say that a continuous surface sphere is still a Dyson sphere, just the most implausible form.

Re: Now...

[Immerman]

Yeah, but Jupiter is kinda short on building materials unless you've mastered matter conversion. I mean there's *probably* rocky minerals in its core, but they'd be a *lot* more difficult to access than on one of the rocky planets. So mine its atmosphere for fusionables and save the rocky core until you run out of more convenient mineral sources.

On the other hand, if you like living on planets then maybe it would be worth mining Jupiter, just to save the more hospitable worlds for terraforming. Its not like asteroids offer much material, only about 5% of an Earth-mass.

Re: Now...

[Anonymous Cow Ward]

You think it'll only be as different in 3016 as 2016 is from 1016? I disagree. Much of the low-hanging fruit has been picked, but materials science is moving along pretty well, and fuel economy - while not what you wanted - is getting better. Furthermore, we're advancing faster and faster all the time - that trend may not continue, but there's no reason to think it'll slow considerably. Hell, even 20 years ago, having widespread wireless internet that you could access through your phone was pretty out there. We're getting better at medical advances too - new and better vaccines (although not as fast as I would like), understanding intelligence, gene modification... Humanity will change considerably within the next 1,000 years, and I'm pretty confident it'll be a bigger difference than it was from 1016 to 2016.

Re:Now...

[tnk1]

It is 1,480 light years away. That means that at that rate, they probably finished the Dyson Sphere 800-900 years ago. Their fleet has been on the way to Earth since then, for sure.

That gives us maybe 500 years to build a fleet of starships with wave motion guns, and an army of humongous mecha.

Re:Now...

[Theaetetus]

There's another possibility that's just as far out, and would explain the missing IR.

It's a traffic hub for small FTL ships.

While an interesting idea, you'd have the same problem as the comets - half a million "small" FTL ships that are 200 kilometers wide, except that's a huge-ass ship, so you're really talking about many billions of reasonably sized ships. It takes a lot of such ships to block an appreciable amount of the solar output.

Re: Now...

[Immerman]

I think there's a slight error in your calculations - I'm getting 2.8e23 m^2, so you'd have almost 2kg/m^2.

Of course that's probably *way* more than you'd need, assuming the vast majority of the structure would be ultra-thin reflective film concentrating the light onto some kind of energy converters. You don't even need much in the way of super-structure - as Dyson originally suggested, the thing could be swarms of orbiting satellites instead of a single rigid structure. Assuming they didn't just put the energy converters close enough to the sun that concentrators were unnecessary, and at that point you're probably talking hundreds or thousands of kg/m^2.

Re: Now...

[tnk1]

Not entirely true. Child mortality rates were definitely an issue before the 20th Century, but if you made it into your twenties, you'd probably live into your 50s or 60s. Not super old, but not exactly dying "young".

Now, you're probably right about not being able to feed seven billion people, but certain cultures like the Chinese had significant population densities for the period based on their agricultural techniques.

I do agree with you about the amount of change, one thing that strikes me is a quote that I remember seeing about art. Art changes faster in ten years in the modern West than it did in five thousand years of Egyptian history. People think of Egypt as being really old, which is true, but they forget that as a distinct civilized entity, it was really long lasting too. And if you look not just at art, but at their technological advancement, you can see it had a similar slow pace.

So, I do think that things are accelerating. There are some hard barriers like the speed of light and energy generation limits, so we may end up hitting a brick wall after some point, but in a few billion years of Earth's history, this is a very unique period. Its just that I think the human animal really hasn't seriously changed or evolved biologically yet, although it certainly could, if we keep finding ways to allow certain people to breed who wouldn't normally do so due to disadvantage or disinclination.

Re: Now...

[doctorfaustus]

If you look at the proper sources, you'll see that future history contains either a "Jackpot" or a singularity, either of which will assure that 3016 will be a far greater advance(?) from 2016 than 2016 is from 1016.

Re: Now...

[TangoMargarine]

For the record, I have no problem with the universe being filled with life. I suspect it's rather common, but given what we know about the reality of physics, chemistry, biology and engineering, these aliens won't have any better technology than we do.

given what we know

Who's the "space nutter" now?

So sorry, no magical materials, no magical energy sources, no force fields, no tractor beams, no transporters, no Dyson spheres.

Just because we don't currently know how to do it doesn't make it impossible, no matter how much you whine about "space nutters" (A.K.A. optimists). Scientists have already figured out how to transmit information via quantum entanglement. Is it really so hard to believe that in another few hundred years that could maybe be developed into a transporter?

"Any sufficiently advanced technology is indistinguishable from magic." - Arthur C. Clarke

Re: Now...

[Immerman]

Think graphene sheets a couple dozen atoms thick - immensely strong, and absorbs almost 100% of the light that hits it, The remaining 99.9...% of the mass can be dedicated to hardware for converting and transmitting the energy. Graphene collectors are even light enough that they only consume a fraction of the much lighter mass budget available if you want them to be supported by photon pressure rather than needing to orbit or have a rigid super-structure to keep them from falling into the star.

And in reality you probably wouldn't build the "structure" out at 1AU, you'd want to be much closer where the sunlight is more concentrated, power density and mass density will both increase as the inverse of surface area. You might also have most of the "structure" being ultra-thin reflective material to further concentrate sunlight onto the energy converters.

Re:Now...

[ewibble]

A nuke would not be very destructive at all, our sun is 1,300,000 times larger than the earth (so about 11911 times the surface area) a dyson sphere is larger than the star. When they say we have enough nukes to destroy the earth many times over they don't mean blow it into tiny pieces just destroy all life on earth.

Also a structure that size would have to withstand large astronomical objects hitting it from time to time.
if a large 16km asteroid it the earth it would be equivalent to a 200 Million megaton impact(http://www.astronomycafe.net/qadir/q975.html) the biggest nuke ever made is only 50 megatons, that is 4 million times more. Even a 75 meter asteroid has a 100 Megaton impact. Basically if we could send a nuke that far into space the kinetic energy would probably be more than the explosion. And an object that size would be already dealing with things much bigger than a nuke on a regular basis.

also from here http://www.space.com/51-astero... asteroids can reach up to 940 km across, not 16km.

Re: Now...

[Immerman]

Nope. Evolution can't be stopped. Eliminate untimely death, and it simply selects for those who reproduce the most. Mandate exactly N children per person and you could maybe slow it down for a while.

Re: Now...

[silentcoder]

Well thats also debateable. Out of dozens of homo species only 2 survived the last ice age. And only one survived to the present day (almost certainly unless one of those scientiffic yeti expeditions actually find something). The other ice age survivor was confined to one tiny tropical island (and an example if island dwarfism). They survived the ice age by not experiencing it.
Thats evolution right there.
New DNA evidence proves that almost 20% of the human genome is neanderthal (though any given person averages only 2% neanderthal dna - we just have different 2%s). That is evolution too.
Inside our dna, broken into pieces so it cant infect us is the complete dna for an extinct virus. Once it must have been a great plague because it is almost perfectly invisible to the immune system. We hijacked that ability and now depend on it to survive. Fetusses hide their foreign dna from moms immune system with the leftovers of an ancient plague.
We are impressively evolved. Of course a cockroach and an amoeba is exactly as evolved as we are but so is every non extinct living organism. Until we find something older than earth that is not going to be something that varies.

Re: Now...

[ewibble]

Why not? building the infrastructure to build a large project seems a logical step. You need to collect the matter somehow. I possible solution would be place self replicating machines around that the star, that collected energy. Once enough energy was collected, replicate disperse repeat. So your initial build is effectively a holly Dyson sphere. This solution would also deal with impacts asteroids and stuff since it could be essentially self healing.

Note: I did fail Dyson Sphere construction 101 at Uni so what would I know.

Re: Now...

[amRadioHed]

What exactly is a "Jackpot"? And what future sources are you using to get this information?

Re: Now...

[ewibble]

Knowledge is built on knowledge, you could not have the plane without the engine, you could not have the engine without metallurgy. Yes we no longer have the concord, basically because it wasn't useful enough for enough people, We don't have really efficient cars because oil was cheap enough, and we do lose some knowledge over time as well. But in general our knowledge is growing, and that growth is likely to be exponential. Baring that we are close to knowing everything we can possibly know, which seems unlikely give the relative youth of our civilization. How many hundreds of thousands of years did it take us to move from using sticks like monkeys to the bows and arrows? With the internet we entering a phase in which we can now share knowledge with the entire world, and if we can overcome our greed, and stop claiming ideas as private possessions, we can start come up with inventions, that can harness the potential of billions of people not just a few people chatting in an office somewhere.

Re:Now...

[amRadioHed]

Feel free to write a science fiction book with the premise, but in science you have to work with what you've got. As far as we can say, there is no way to just make a stars tremendous heat output just go away.

Re: Now...

[Zumbs]

Biological evolution is still alive and well. Go back a few centuries and survival to adulthood was as much a question of luck as it was a question of hardiness and wealth (of your parents). Furthermore, the traits needed to survive and prosper a few centuries or a few millennia ago are not necessarily the same as are needed today. There is a short article on it on wikipedia.

We also need to realize that evolution is not just biological. It is also sociological. Different cultures are not necessarily equally adept at making the most of their situation. Naturally, as the situation change, the desirable cultural traits change, but the culture does not always manage to adapt before it collapses on itself or another culture becomes dominant.

Re:Now...

[Immerman]

And a tornado releases a tiny fraction of the energy that hits the US every day as sunlight - the difference being that it's an extremely concentrated energy release, which is thus very destructive to the specific things it hits. Maybe a nuke takes out only one solar collector, or point defense system, that's still effort they have to spend to rebuild. And nukes pack far more destructive potential into a much tinier and harder-to-spot package, especially if designed specifically to be difficult for a space-fairing

And why would you expect the sphere to get hit by debris? The inner solar system would probably be swept clean for resources by the time you have a significant fraction of the sun captured, and longer-period orbital debris would probably be mapped and deflected long before it came anywhere near the sphere. After all you've got energy to spare, and it's likely a lot easier to slightly modify orbits than it is to repair your structure.

There's also no reason to assume it's particularly strong - picture swarms of orbiting ultra-light reflective "umbrellas" focusing sunlight on their photovoltaic "handles". Ribs and shaft could be extremely spindly, especially if using spin-stabilization for the parabaloid. Why waste material on durability of stuff that is in a clean orbit? This is stuff that's already within reach of our own technology, at least in crude form.

Re: Now...

[TangoMargarine]

I know we have limited understanding of science.

Well, at least I do. Apparently you and Tenebrousedge know everything there is to know about the universe. Obviously I defer to your omniscience.

Re: Now...

[ShanghaiBill]

Its not like asteroids offer much material, only about 5% of an Earth-mass.

If converted to O'Neill Cylinders, the asteroids contain enough mass to create a several million times as much surface living space as an intact earth sized planet.

The surface of a planet is a terrible place for a civilization.

Re: Now...

[Jarik C-Bol]

Ok, so here's the plan:
We strip mine the entire asteroid belt, Oort cloud, and half the outer gas giants for materials, we use those materials to bulk up the smallish inner planets closer to earth size and mass, thus adjusting the gravity nearer to earth-normal. While we're doing that, we're gonna need to burrow down into Mars and re-melt its core and spin it up to restart its magnetic field. Then we actually MOVE Mercury, Venus and Mars into orbits closer to Earths, so they are better positioned in the goldilocks zone, and terraform them all. We keep the other half of the outer gas giants to serve their purpose, to sweep up debris from the solar system and reduce impacts to the inner solar system. Any remaining raw materials we have left after that, we build *sections* of Dyson sphere near our new habitable Mercury Venus and Mars, as well as Earth, and use them to scoop up as much power from the sun as we can, but without the hassle of egshelling the actual sun, which physics says you cant do because orbital mechanics don't work that way, and there is no material strong enough to do it. So the net result is we get 4 habitable planets orbiting the sun, with giant solar collectors parked ahead and aft of each of them, with general solar system defense still provided by your favorite gas giants.
After that, we find a HARD project.

Re:Now...

[ewibble]

first an asteroid is a concentrated impact not a spread out one. Are you suggesting we are aiming these nukes? all we see is some funny light readings we have absolutely no idea what to shoot at, in a very large target.

Where there is a way of clearing the incoming object or absorbing the impact is irrelevant, since the nukes wouldn't even get close.

I really can't picture anything, however if it it could be a swam of self repairing replicating object, that may just move out of the way if an object gets near enough. If they get hit they just get replaced, with negligible effort. Even if the sphere was just out side the star it would be dealing with much more from just the star regularly. Further out it would have to deal with more incoming objects. Even if you assume that someone how this swam couldn't trivially deal with a nuke, The missiles sent to a star 1,500 light years away would have to have some pretty serious kinetic energy built up. The actual nuclear payload would be irrelevant.

Re: Now...

[Locke2005]

Whoa... but then, wouldn't these "dark matter" stars be emitting the same infrared radiation? I like the random dust cloud hypothesis better. Orbiting alien megastructures would exhibit periodic dimming, not random dimming.

Re:Now...

[Locke2005]

No, any alien capable of building a Dyson sphere would have eliminated all asteroids capable of causing problems long before the megastructure got big enough to cause detectable variations in starlight. Natural phenomena is still a better explanation than aliens, but the actual explanation might still involve some interesting science. I still like the dust cloud passing in front of it theory.

Re: Now...

[Locke2005]

Human evolutionary pressure now favors larger breasts and butts, not smarter brains...

Re: Now...

[Locke2005]

Technological progress is growing at a geometric rate, but that is mostly because population is also increasing at a geometric rate. The rate of change will likely be slowed at some point by a massive die off. In general, should the rate of progress be proportional to the number of scientists working on progress?

Re: Now...

[Locke2005]

Any "future history" is indistinguishable from "bullshit"...

Re: Now...

[Locke2005]

Any aliens foolish enough to make their presence easily detectable would have been wiped out by aliens smart enough to be incredibly stealthy a long time ago, so the argument that there are no detectable aliens out there is a sound one. Smart species don't advertise their position.

Re:Now...

[Locke2005]

No, the ships themselves aren't blocking light like a comet, the gravitational distortion caused by warp drives is causing gravitational lensing that refracts the light off in strange directions. Without knowing exactly how the warp drive works, it is impossible to calculate how many ships are necessary mess with the light to this massive degree... although a randomly distributed dust cloud between us and them still sounds like a much simpler explanation.

Re: Now...

[TangoMargarine]

Assuming that species advanced enough in inter-system space travel are still interested in war...

One would kind of hope not.

Re:Now...

[Vitriol Angst]

However, even us bumpkins on earth know to throttle down our engines when entering a dock.

The gravitational distortion used to propel the crafts FTL are not likely going to be used -- or at least not at full strength in a confined area as they'd be shifting other ships around as well. Of course any gravity distortion field is likely to have a VERY large area of distortion (like one wave peak to peak the length of a planet) and it would take an order of magnitude less ships to diffuse the light.

HOWEVER, any analysis of the light passing through such a distortion would probably create a very wide gamut of light -- any analysis with a interferometer would show such an anomaly. Since we haven't heard of one - likely no gravity distorting drives.

MY GUESS is that it isn't the star getting dimmer, but an astronomical event that made the star brighter has passed. I'm thinking like the exhaust at the pole of a black hole pointing at the star causing a huge flare. As the orbits of the star to the black hole have passed - it's energetic activity has passed.

I'd look for a black hole above or below the galactic plane of orbit to the West or East of the star for about 20 light years.

Re:Now...

[Vitriol Angst]

Ants throwing sand grain sized nukes at us would definitely destroy us and all of humanity as well. There are more termites by weight than humans by weight (unless the McRib sandwich is available year round). If the ants ally with the termites, we'd have no cover from their many-nuke assault.

Your strategy sounds viable, we just send rockets with ants and their nuke sand at the aliens -- they'll never know what hit them. Bonus; if it fails, we got a patsy. No more of those damn red ants biting you at your picknick in Central Florida!

Re:Now...

[Vitriol Angst]

The OP proposed ants with Nukes -- you can't change the proposed scenario and then claim its a mere nuisance! That's just no fair or worthy of a Slashdotter. ;-)

Re:Now...

[Vitriol Angst]

The attack would not be after the Dyson Sphere, it would be after the ships, the aliens and then after that, the picnic baskets.

You are just not thinking strategically.

Re: Now...

[Immerman]

Ambitious. But I don't think I'd bother leaving the gas giants - they mostly do their job over the course of millions of years, not fast enough to be useful for protecting the inner system - that long-period comet needs to be stopped on the first pass that would hit your sphere, not "eventually"

Actually, the original Dyson Sphere concept calls for swarms of orbital satellites - even unbroken rings cause no orbital issues, and you can create many "concentric" rings with different orbital planes - each satellite will obviously be shaded by inner rings, but it need only be for a tiny fraction of it's orbit. You'd start having diminishing returns, but not enough to be a major issue until you're capturing a sizable fraction of the sun's entire output.

There's also another option if your material science is advanced enough - non-orbiting statites supported by photon pressure. I forget the weight limit, I think it's something like a fraction of a gram per square meter (independent of distance from the sun, since both photon pressure and gravity fall off at the same rate) , but something like a dozen layers of graphene could conceivably capture most of the energy that hits it, while still leaving most of the mass budget available for power transmission, etc. If you can pull it off then you could "eggshell" the entire sun with stationary collectors without the need for any supporting structure.

Re: Now...

[Immerman]

That's great, but still not nearly enough to tackle a Dyson-sphere scale project.

Re:Now...

[Immerman]

Presumably they're guided, we're going to have a hard time hitting anything around another star otherwise. And the guidance system would probably be programmed to home in on whatever seems like the "highest value" target.

And yes, asteroid impacts are dangerous as well, but generally also fairly visible - a nuke is going to do a lot more damage than an asteroid that's as easy to see, especially if we assume the nuke has been "stealthed" to be as near to invisible black as possible. As for kinetic energy... you're absolutely right, at least assuming we want it to reach them any time "soon", and are okay with announcing where we live, as opposed to letting it sail harmlessly past their solar system and then decelerate and attack from another vector. Then again, on a ballistic trajectory we're not going to be able to hit anything except the sphere itself, which is probably a relatively low-value target.

Re: Now...

[Immerman]

Does it though? Do such individuals actually have more (and more prolific) children over the course of their life, or just more admirers? I think actually carelessness and stupidity are probably being selected for more strongly.

Re:Now...

[Immerman]

Read again - it was ants with low-velocity sand grains.

Re: Now...

[doctorfaustus]

It's where everything goes to hell slowly because of greed, complexity, creeping rot... See "The Peripheral" William Gibson

Re: Now...

[Anonymous Cow Ward]

I dunno, the population of first-world countries (the ones doing the most technological progress) isn't growing by much, and sometimes it's declining. In general, rate of progress should be proportional to the number of people working on it, yeah. I think that as we become more and more efficient at producing food, etc. that we could afford to employ more and more people to do that; whether or not we will is another story.

Re: Now...

[ChrisMaple]

Four planets in earth-like orbits is unstable and would require occasional adjustment -- ringworlds and Dyson Dyson spheres are also unstable.

Re: Now...

[ChrisMaple]

Difficult to tell. The further we progress, the more that has to be learned before an individual can use that learning to contribute something new. On the other hand, as knowledge is systematized and clarified, many things become easier to learn. Learning technology itself may improve. If machine intelligence ever gets very effective, computers may do scientific functions and the number of (human) scientists becomes irrelevant.

Re:Now...

[BoogieChile]

Yeah, they might decide to send us a little Gift of Mercy

Re: Now...

[ChrisMaple]

Adequate genetic technology makes the concept of human evolution antique. Why wait for a mutation, or go through the difficult process of finding a mate who can compensate for your genetic faults, when direct genetic manipulation could fix flaws or introduce new features?

Re:Now...

[Your.Master]

So we need to develop an AI that is able to tactically analyze a Dyson sphere to find high-value targets (along with detector equipment to find them), despite having no notion of what's there? Or do we just have a kamikaze population in cryosleep or generation ships to steer the nuclear missiles?

If we're assuming we have sci-fi technology, why not just assume we send self-replicating nanobots to disassemble the Dyson sphere?

a nuke is going to do a lot more damage than an asteroid that's as easy to see

What makes you think that?

You can add velocity at the same mass and it will increase the impact while also giving the opponent less time to detect it. Note that you'll have an entire star's gravity pulling you into the Dyson Sphere, and the cite ewibble made above about 75m asteroids doing 100 megatons was based on Earth impact so it significantly overstates how big the asteroid needs to be. The escape velocity of the sun is about 60 times that of Earth, so assuming the Dyson sphere's properties are similar to our sun's, the impact is 3600 times as much at the same mass (because kinetic energy is proportional to the square of velocity and 60^2 = 3600). Kinetic energy is directly propertional to mass, which is proportional to the cube of the radius, so the radius is about 1/15th the size. That means your 100 megaton asteroid is really just 6m in diameter. Tsar Bomba, which was only 50 megatons, was 8 meters long and 2.1 meters in diameter. They have comparable dimensions and comparable payload. If these are serious threats to the Dyson sphere, then the Dyson sphere must already be defending agaisnt threats of this scale in some manner.

especially if we assume the nuke has been "stealthed" to be as near to invisible black as possible.

How do you stealth a nuke beyond the capabilities of a Dyson-Sphere wielding civilization with unknown other technologies to detect? Again, the premise was launching nukes today "just in case". If there's a way to stealth these things better than silent asteroids, we don't know it.

and are okay with announcing where we live, as opposed to letting it sail harmlessly past their solar system and then decelerate and attack from another vector

How much fuel are you going to load into this thing???? Fuel that has to last millennia in space, mind you (much longer if you're going past and then revectoring). If it's going to re-vector such that it scrubs out its previous trajectory, then it needs to significantly nudge its orbit even if you take liberal advantage of slingshotting. Mind you though, if you're already thinking of adding fuel to re-vector in flight, it doesn't need to go past the target solar system. Just aim a little to the right or left of the star and have it course-correct in 1000 years and then securely delete the information on the computer that did the course correction (so that the computer's function can't be reverse-engineered). Even a relatively slight angle would effectively wipe out information about its trajectory.

Presumably if these things were stealthed and undetected until impact, they can't really find us anyway. Except in the same sense that we found the Dyson Sphere in the first place with early 21st century technology, in which case, maybe they watch us launch the nukes in the first place with their superior exoscale optics looking at all the planets likely to harbour dangerous lifeforms :).

Then again, on a ballistic trajectory we're not going to be able to hit anything except the sphere itself, which is probably a relatively low-value target.

The point isn't to hit them with mass drivers, the point was that they are being constantly slammed by mass drivers from the ambient environment. If they can survive that, and if those ambient mass drivers are more destructive than what we can put out, that implies they can survive what we send against them unless

Re:Now...

[Your.Master]

That's the point. If they can eliminate all asteroids -- which must include incoming asteroids, because they haven't eliminated all asteroids everywhere -- why can't they eliminate incoming nukes? The best nukes we have have a payload that is similar scale to the absolute minimum damage they'd possibly do purely as a mass driver.

Re:Now...

[cathector]

hm, that's intersting.

but I hadn't realized this star is only 1500 light years away.
if we assume a major FTL traffic hub at that distance I'd sort of expect more visitors here on earth.

there's no radio signals for them to have received yet,
but if they're that fancy I'd expect them to have pretty good telescopes,
and with FTL who knows how short the trip is out to us.

Re:Now...

[brantondaveperson]

it could be a swam of self repairing replicating objects

Sounds like it could be Mantrid's drone arms, in which case we might be in trouble.

Re: Now...

[arth1]

Human evolutionary pressure now favors larger breasts and butts, not smarter brains...

Looking around me at my cow-orkers, that does not seem to be true. Yes, they all have large breasts and butts, but few of them have become fathers.

Re:Now...

[whipnet]

Are you saying that this alien race are beings 1000's of ft tall? *

Re:Now...

[Marxist Hacker 42]

A megastructure need not be inanimate matter. A very large biological organism may well absorb more heat than it would emit as light.

Re: Now...

[painandgreed]

Is it, though? Haven't we largely thwarted evolution, and replaced it with survival of everyone we like?

No, we're now merely adapting to our new environment.

Re:Now...

[Immerman]

Why would it attack the Dyson sphere? If we're stupid enough to attack such a civilization then we're probably going to want to attack something interesting, not just put a nick in their probably ridiculously cheap to repair power source. Naively, aim for the largest energy-emitting source in the system. Or the source of the most complexly-structured emissions (communications). Either is likely to be a high value target.

Beyond that... you make good points. And honestly the sheer ridiculousness of attacking a star 1500 years away with anything less than planet-sized flotillas or some sort of star-killer has robbed me of the desire to further play the game.

Just a couple final quibbles - in free fall it should be relatively easy to analyze the debris after the fact to determine the original momentum vector of any sort of kinetic-energy weapon even if it is undetected until the moment of impact. There's also no re

Re: Now...

[Immerman]

Nah, you can almost certainly design the electronics around it. Keep 'em simple, maybe use transistors the size of your fist, lots of shielding, we could almost certainly figure something out. And your nuclear material wouldn't decay much. U235 (the explodey one) has a half life of over 700 million years. The heavy elements were created in the heart of supernovas long before the Earth was born 4.5 billion years ago. They're not going to evaporate over the course of a few thousand years. You're thinking of nuclear "waste" and other unstable mid-table elements - those will decay substantially in mere thousands of years

Re:Now...

[lucien86]

A relativistic vehicle would have far more destructive potential as a simple mass driver then any nuclear warhead it carried.. Let alone that building something on the scale of a Dyson sphere..
In comparison in the Star Wars universe the Death Star was 120 km across, and they had one. (ok two) It would take millions or billions of machines bigger than that first Death Star to build a Dyson sphere.
And a single machine 100 km across would need engines that would put out the power of billions of nuclear bombs exploding continuously.. A nuclear explosion wouldn't even scratch them..
If all that is not enough a civilization with FTL capacity would be able to build sensors that could detect future incoming threat potentials, and proactively react to them. (in effect machine precognition) They would also regard relativistic impactors as a primary threat and would no doubt have specific defences to deal with them.
Might as well use bows and arrows as nuclear weapons...

Re:Now...

[cwsumner]

I think any nukes sent there would be far past their half-life, and duds, before they ever got there. Even at a large percentage of lightspeed...
  It would sort of be like throwing rocks at an aircraft carrier!

Re: Now...

[Jarik C-Bol]

If we develop the tech to move a planet to a new orbit on purpose and accurately, clearly we can adjust and stabilize from time to time.

Re: Now...

[Jarik C-Bol]

Planets have this nice feature called "A Mostly self sustaining breathable environment at 1g" which is what Humans work best in. Less day to day maintenance, and i've never had anyone I know die to explosive decompression into the void. Also, many of us like wide open spaces.

Re:Now...

[RockDoctor]

When they say we have enough nukes to destroy the earth many times over they don't mean blow it into tiny pieces just destroy all life on earth.

Hmmm. "Destroy all life on Earth" ... tricky. Even with our whole arsenal, we're pretty unlikely to get everything even on the surface of the Earth. Unless you count the surface of the oceans as "the surface", which neglects the whole bottom several kilometres of the oceans. There's representatives of every phylum other than land plants there, and you're going to have to work hard to annihilate all stored/ buried seeds on land.

You could probably wipe the land clean pretty fast, but to actually destroy all marine life (and all life in thicker soils) is a much harder task.

I've always been suspicious of the "deep biosphere" idea, but there certainly is life in rocks down to several kilometres depth (I've bagged the samples myself). So that's another excavation target you'd need.

Re:Now...

[RockDoctor]

No, any alien capable of building a Dyson sphere would have eliminated all asteroids capable of causing problems long before the megastructure got big enough

This is a trope that has appeared in SF. To demonstrate "would have" you'd need to deal with both in-system debris - material in orbit around the star that you're encapsulating - and have an infallible system for dealing with random incoming debris from outside the star's orbit. The one is a big deal to achieve ; the second is something that would require detailed continuous observation with infallible hair-trigger responses. Which is going to cost a lot.

How would we, today detect an incoming extra-solar asteroid? Well, we could rely on a ring of telescopes in the Kuiper Belt - except that our hypothetical megastructure has cleared out their Kuiper Belt, because it's part of the problem. Plus there's nothing to prevent the incoming projectile from coming in from any direction. But you can build your big telescopes in the Kuiper Belt and have them look towards the poles ; you'd need interception hardware to be pre-placed in a range of high-angle orbits, but that's small beer to a Dyson-building civilisation. Now, you complete your Dyson - be it Sphere or Swarm - and all of a sudden you've trapped 90% plus of the light leaving your star, so it's suddenly a LOT harder to see anything out there that's coming in.

Of course, all that hardware will need maintenance. Or, if it goes off-line, it'll become a uncontrolled debris itself, adding to the threat.

I don't see Dyson spheres being any great use for anything other than getting thermonuclear power without having to build your own fusion reactor.

Re:Now...

[RockDoctor]

have it course-correct in 1000 years and then securely delete the information on the computer that did the course correction (so that the computer's function can't be reverse-engineered)

I think that impacting a surface at dozens of kilometres per second counts as "secure delete." Your computer is going to be vapourised on impact.

Re: Now...

[RockDoctor]

You're thinking of nuclear "waste" and other unstable mid-table elements - those will decay substantially in mere thousands of years

Even eka-Manganese (as Mendeleev named it's placeholder in the periodic table ; technetium otherwise ; the lowest mass element with no naturally occurring stable isotopes) has isotopes with half-lives in the 200,000 to 4,000,000 year range, which would survive a 100,000 year journey without problems.

Actually, you'd want to be careful what isotopes you used. The presence of short-lived isotopes (say 150,000 years) would constrain the time of flight of the attack.

Re: Now...

[RockDoctor]

[W]hat if a star were bombarded with large inert bodies consisting of iron or other materials that would create inconsistent light output as those semisolid bodies materials moved about within the mixture?

A couple of years ago analysis of a star's light showed that it had recently had a large amount of debris similar to asteroids. I'm struggling to find the reference, I'm getting interference from the story that we're discussing at the moment. Can't find it. There's lots of reports of detecting silicates in the atmosphere of white dwarfs (e.g. http://arxiv.org/pdf/1007.2252... ; tracing forwards from that should get you a lot of stuff) But, no matter ; the spectral patterns caused by solid (silicate, asteroidal) bodies impacting stars is not a new topic, and there's plenty of evidence that the process is fairly well understood. Unless you're going to call the original researchers incompetent (which is not a good idea, unless you're actually working full time in that field yourself), it's safe to assume that they've covered this possibility, otherwise one or other of the people listed in the references of that 2010 review article would have raised the question.

We need to think outside the box,

Think outside the box as much as you like. But you are constrained by the evidence. In this case, TFP start it's abstract with "The star KIC 8462852 is a completely-ordinary F3 main sequence star," so your scenario doesn't fit the reality. It might be interesting for some other star, but not this one.

Re: Now...

[RockDoctor]

And what future sources are you using to get this information?

The sources that give him the answers he wants.

Re:Now...

[RockDoctor]

If they use something like an alcubierre metric based warp drive, then the gravitational fields around the craft will scatter the star's light into vectors that are no longer straight lines away from the star. This will result in the star's effective brightness being reduced.

... and in other directions, the light will be enhanced.

Actually, the maths for such space distortions was done - decades ago. For the MACHO project.

Get enough of them going in and out of the system routinely, and you will get the observed phenomenon.

Having just been looking at the data, I see 24 dips in the time period, and 10 spikes. So ... something must be aimed pretty close to directly at us (or away, or in a cone of directions about our location). There would need to be some sort of unidirectional flow to produce that discrepancy in deviations from the norm. >{?and your model accounts for the secular (long-term, century scale) dimming just how ... ?

Re:Now...

[RockDoctor]

Thermodynamics doesn't work like that. If your organism doesn't absorb or emit electromagnetic radiation between 350 and 750 nm wavelength ("light") - at that point you're not talking about this star. This star DOES have something absorbing electromagnetic radiation between 350 and 750 nm wavelength ("light") - and does absorb between (say) 750 and 1500 nm wavelength ("heat"), then it will also be emitting at wavelengths greater than 1500nm.

Actually, strictly, any body at a temperature greater than absolute zero (which is unattainable), emits at all wavelengths, though the flux varies greatly with wavelength.

Re: Now...

[RockDoctor]

if a large mass of iron or other inert material were in a star, it would be much heavier than the gases so would sink into the core,

This is precisely what happens in the cores of stars as they go through the various stages of nucleosynthesis to produce heat. Initially, hydrogen goes to helium (which accumulates into an relatively inert core) ; then eventually the helium starts to "burn" to produce carbon (the Sun will probably go this far, but not much further ; not enough mass) which will accumulate in the core leaving a "shell" of helium burning. Eventually, given enough mass, the carbon will start to go to form neon, then the neon to produce oxygen, then sulphur, then silicon then iron. This is the standard story of stellar evolution, which is why Fred Hoyle was in the running for a Nobel in the 1950s. When you get to iron-56, the energy release essentially stops and your star has hours to a day or so left to live.

making it hard to have any effect on its light patterns.

The convection patterns inside stars are a bit hard to observe, and hard to model, but there is some material that gets up to the surface where we can see it. And blowing the star up in a supernova tends to release material from the core, which can be seen too. "Hard" to measure, but not impossible to estimate, and justify.

Also, if it was there for very long, the metals would probably vaporize eventually and disappear.

Metals don't disappear. They may disperse, and become a bit harder to see, but they're still there.

You know, I think you could benefit from, and enjoy, a MOOC on stellar evolution.

Re: Now...

[RockDoctor]

Yes, I'm a geologist.

To me, it's vitally important that you - whichever country you live in - get back to buying and burning "foreign" oil as soon as possible. Until we get this damned surplus of oil cleared up, we're hurting economically and may otherwise have to engineer a major war to bring prices back up.

Alien Megastructures:

[ZecretZquirrel]

Tonight on the History Channel.

Re:Alien Megastructures:

[Applehu Akbar]

"Tonight on the History Channel."

But where does Hitler come into it?

Re:Alien Megastructures:

[lord_mike]

It's a secret weapon of the Luftwaffe... tonight at 8pm.

Re:Alien Megastructures:

[PolygamousRanchKid]

Accually, the Luftwaffe did build an airbase on the Moon: https://en.wikipedia.org/wiki/...

However, the whole project got derailed, when the astronauts discovered the nudist colony on the Moon: https://en.wikipedia.org/wiki/...

They had the choice of fighting for the master race, or playing naked volleyball with chicks who had 60's style Russ Meyer breasts.

They "did the right thing . . . "

Re: Alien Megastructures:

[93 Escort Wagon]

May is springtime for History Channel Hitler.

and Germany?

Re: Alien Megastructures:

[MonoSynth]

They're still hunting the dude on the European History Channel. I don't really understand why they keep going to Argentina and do the exact same thing there three times a week.

Re:Alien Megastructures:

[Z00L00K]

All the Nazis went to that star and started all over again.

Re:Alien Megastructures:

[rasmusbr]

"Tonight on the History Channel."

But where does Hitler come into it?

Did Hitler attend a secret meeting with alien representatives in an underground meeting room under Washington DC in 1929?

Re: Alien Megastructures:

[zippthorne]

Is the AC referencing a song from a fictional musical in a movie about a fraudulent musical, the musical made from that movie, or the movie version of the musical made from the movie about musical fraud?

Re:Alien Megastructures:

[Hognoxious]

Wasn't the History Channel good (or at least, sort of OK) a few years back?

By a few I probably mean about ten.

Re:Alien Megastructures:

[pslytely psycho]

"They had the choice of fighting for the master race, or playing naked volleyball with chicks who had 60's style Russ Meyer breasts. "

In low gravity no less!

Re:Alien Megastructures:

[smallfries]

It's been a long time since there were any history shows on the History Channel. Alien Megastructures: the reality show where rival alien groups compete to transport large structures around the galaxy in short time frames. If they break it they buy it...

Re:Alien Megastructures:

[PopeRatzo]

60's style Russ Meyer breasts

In low-gravity no less!

Re:Alien Megastructures:

[Hognoxious]

If it's "Clash of Warriors" I was thinking of (among all the unsorted random stuff on my HD) then yes, you're closer.

It's Primes

[justin12345]

Send quantuum busters, we won't get a Second Chance.

Re:It's Primes

[TheRaven64]

With all of the good things that he's written, I think that we can forgive the author one deus ex machina. And never speak of that trilogy again. Ever.

Re:It's Primes

[TheRaven64]

The Nights Dawn trilogy. It's about 3,000 pages long, and goes rapidly downhill in the last 300. Aside from Misspent Youth, everything else Peter F. Hamilton has written has been worth reading, but Nights Dawn put off a lot of people by having a truly bad ending.

Re:It's Primes

[The-Ixian]

I thought it was good enough to pick up his sequel to the series.

He is an imaginative guy but more than a little sexist and a huge meat eater apparently... Also, all of his domestic scenes are about as sappy as an episode of the Brady Bunch.

Re:It's Primes

[The-Ixian]

Yeah, I did like the Great North Road too.

Overall, I like him. He is Greg Bear caliber when it comes to wildly imaginative sci-fi and his tech is well researched and believable.

Re:It's Primes

[TangoMargarine]

and a huge meat eater apparently

I can't figure out why either interpretation of that would necessarily be a bad thing. Elaborate?

Re:It's Primes

[mukinrestak]

He is an imaginative guy but more than a little sexist and a huge meat eater apparently

How is that relevant? Orson Scott card is a fuckin nutter, and that doesn't make Ender's Game any more or less good. Even L Ron wrote some good shit, and it's not made better or worse by the blight he left upon the world via Scientology.

Maybe they're not building it...

[Etherwalk]

even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century. --Summary

So maybe the aliens aren't building it. Maybe they're just moving it... towards us...

Re:Maybe they're not building it...

[cdsparrow]

I love it when people make judgements on the capabilities of an alien race. By definition, they are alien, so we can make no generalizations. But ostensibly since we can't conceive of a method of building a dyson sphere in 100 years, that means nobody else can either... Personally I bet someone screwed up and dropped a heavy element into the star with an errant stargate and now the star is going through death convulsions.

Re:Maybe they're not building it...

[silentcoder]

But you are also assuming that our understanding of those laws is absolute and final.

You don't think a race whose technology was at the building-a-Dyson-sphere level would have science far beyond ours ?

That assumption may hold true if, tomorrow, we found a theory of everything which was, in fact, the absolute truth (though of course, we would then spend forever looking for the next leap forward so even if we found it we would never know it - after all it took 2000 years to move beyond 4 elements and almost 500 to move beyond Newton).
But the fact is, even if we came up with a theory of everything tomorrow, it almost certainly would *not* be the very last word in physics (and may well lead to some modifications to the laws of thermodynamics).
As it stands thermodynamics is just a model, a very simplified model (in which molecules are modeled as hard perfect spheres). It's extraordinarily useful as such but it would be incredibly surprising if that simplification did *not* mean there are things it doesn't account for which in extreme conditions would change the outcome.
That "coarse-graining" effect is one likely explanation for why the universe is clumpy and seems to have gotten more clumpy over time (the exact opposite of what the entropy law predicts - it's Hawking's preferred explanation, and Roger Penrose made much the same argument in the Emperor's new Mind.).

You never even considered that by the time building a dyson sphere is possible, we may have somewhat more fine-grained laws of thermodynamics ? That we may be able to advantage of what we've since learned ?

Now, this is not a scientific post - there is no way for us to scientifically test of this idea (since we have no concept of what the idea would look like - we don't yet have anything remotely resembling a viable alternative to or improvement upon thermodynamics) - but it is utterly unscientific to assume there isn't one. I promise you there is.

Re:Maybe they're not building it...

[TangoMargarine]

As opposed to what? "If it's aliens we can't even speculate." *throws up hands*

Granted the whole line of reasoning isn't particularly productive from a scientific standpoint, perhaps.

Re:Maybe they're not building it...

[RockDoctor]

I love it when people make judgements on the capabilities of an alien race. By definition, they are alien, so we can make no generalizations.

No?

They're 454 parsecs away. If they're exposed to different laws of physics to us, then we really don't understand the universe, and our technology is going to fall apart no £$^%$&%*$£ NO CARRIER

Oh, that hasn't happened. So, they have the same physics as us. Actually, the same chemistry as us (both are closely coupled by the spectroscopy of the star - same physics and same chemistry as us). So we've got a good knowledge of what their environment was 1500 years ago.

We've no reason to believe there is anything spectacularly different to our environment there. So the same general limits as apply to our environment apply to this environment. We're not seeing bucket-loads of magnetic monopole in our environment, so we're not going to see them naturally in that environment. While we do see these weird short-term spikes in the light pattern, the rest of the spectrum is fairly normal (though there is an intriguing and unusual secular dimming on a century-scale). More weirdly, the spikes are (by my count) 24 dips and only about 10 rises - which doesn't look like a MACHO transit light profile from an intermediate object (which wouldn't explain the secular variation anyway.

It's very peculiar. It's also tea time for me!

"just a century"?

[jeffb (2.718)]

If you're willing to believe in a civilization capable of building a Dyson sphere, how much more of a stretch is it to believe they could do it in a few centuries? (We've just been seeing a dimming signal over that period, not complete extinction of the star's light.)

I mean, yeah, I have some idea of the energies involved, and I'm not sure I can envision a process that would run at that pace producing anything other than streams of plasma at gamma-ray temperatures. But then again, I'm not sure I can envision a process that would digest entire planets worth of material and cast it into a shell at any pace. Good thing I didn't accept that particular process-design gig, I guess.

Re: "just a century"?

[bill_mcgonigle]

The surprise would be if a Class-whatever civilization that's building a Dyson Sphere hadn't already mastered self-assembling, self-replicating construction processes. There should be an exponential increase in the rate over time, if we haven't already missed that window. As the buildbots consume the planets, you just get more buildbots until the number is sufficient. Or if the sphere is to be made of the bots themselves then there's no need for a tail-off. Clarke called 'em monoliths when he had them eat Jupiter, but same idea.

Re:"just a century"?

[93 Escort Wagon]

If you're willing to believe in a civilization capable of building a Dyson sphere, how much more of a stretch is it to believe they could do it in a few centuries?

Nah, they probably built replicators to accomplish the task. But then those replicators destroyed their civilization and are gradually surrounding the star with a Dyson sphere... made completely out of replicators.

Re:"just a century"?

[zippthorne]

What are the odds that not only can they build it in a span of a few centuries, but also that human civilization would exist and be able to observe the specific few centuries they build it over?

Re:"just a century"?

[Chrontius]

If they seeded our planet with life using FTL drives, the light of their civilization's dawn could just be reaching us now. If we accept the given of rare garden worlds, and cosmic gardening, the odds of seeing this are actually quite good.

Re:"just a century"?

[SuricouRaven]

Who knows how many pre-megastructure civilisations there are in the galaxy? There could be millions, each one thinking they are alone.

Re:"just a century"?

[gl4ss]

and just do it at one star?

doing it in span of 100 years makes no sense from energy use perspective.

Re: "just a century"?

[zmooc]

Buildbots probably wouldn't consume planets; escaping from their gravity well would be much too costly compared to the alternatives. They probably would use asteroids instead, taking their time to tweak their orbits so they arrive at their destination processing plant with a minimum amount of energy. This would almost certainly not happen at an exponential rate. As with all mining, they would start with the low hanging fruit, causing production to become increasingly more difficult as time passes, prohibiting durable exponential growth.

Also, while I'm typing a comment anyway, the Dyson sphere would probably reflect raditation to several power stations within it. These might very well redistribute it by simply reflecting it back out, for example to stations in the outer star system, from where it can be redistributed to their mining sites (perhaps even simply blasting asteroids with radiation in order to control their orbits). This would cause the radiation from the Dyson sphere that Schafer expects to come from somewhere else entirely and probably not in a uniform way at all; we might very well not even be able to detect it or would perhaps discount short bursts of radiation reflected from asteroids as being noise. I can imagine their entire star system to look like a giant beautiful collection of laser scanners ;)

Re: "just a century"?

[Viol8]

Thats all very well, but these buildbots still have to obey the laws of physics and self replication of complex objects simply can't happen that fast. It requires time and a boatload of energy and complex chemicals and material resources. You can't make something complex out of hydrogen unless each little bot has a mini fusion reactor on board which is pretty unlikely. Evolution has had 4 billion years to fine tune self replication on this planet with huge resources and sunlight, and yet even the fastest growing bacteria still grow slower than the human eye can resolve. There's no reason to assume an artificial system could manage it much faster given similar constraints.

Re:"just a century"?

[Carewolf]

I guess it could have been build over thousands of years, but most of the time when we haven't been recording it and when we did photograph the star 100 years ago covering parts of the star we couldn't see, and now the structure is rotating into our line of sight (possibly again) covering it a bit, until it rotates out of sight again. Or it could be a gas cloud that we are now seeing through at the worst angle. In both case it should slowly go away again as they rotate and or out viewing angle subtle changes.

Re:"just a century"?

[Anonymous Coward]

von-Neumman proposed an idea where you send out self-replicating mining robot machines into an asteroid belt. These generate the prefabricated construction tiles for the Dyson sphere which are then sent to the target orbit and assembled automatically.

Re:"just a century"?

[arth1]

Who knows how many pre-megastructure civilisations there are in the galaxy? There could be millions, each one thinking they are alone.

Increase that imaginary number by a few orders of magnitude, and there might be an explanation for dark matter there...
But the question then becomes "why don't we see this happening every way we look?"

Re: "just a century"?

[Viol8]

"There have been a bunch of mass extinctions that have killed off billions, if not more, branches of life."

And none of them killed off bacteria.

Re: "just a century"?

[Viol8]

We might not know all the laws of physics, but if the was one that allowed life to group exponentially faster than currently then there's a good chance evolution would have "discovered" it by now. Assuming of course it could be used with the kinds of conditions and resources found on earth I grant you.

Re: "just a century"?

[chihowa]

One of the largest mass extinction events of all killed off only bacteria (obligate anaerobic bacteria). Of course, it was caused by other bacteria.

Re: "just a century"?

[jeffb (2.718)]

Evolution has had 4 billion years to fine tune self replication on this planet with huge resources and sunlight, and yet even the fastest growing bacteria still grow slower than the human eye can resolve. There's no reason to assume an artificial system could manage it much faster given similar constraints.

Evolution isn't goal-driven. Well, I guess it is now, if you (quite sensibly) consider human activity as part of the evolutionary process.

I don't think there's something magical about self-replication that makes it immune to technological improvement. Look at the rate of increase in human population over the last couple of centuries.

Re: "just a century"?

[tnk1]

That makes me wonder if, perhaps, what we are seeing is *not* a Dyson sphere, but instead, the material that might be used to build *something* is being moved into place. Presumably it will be easier to move the asteroids and such to the required locations/orbits and then disassemble them on site.

Of course, this probably is not a Dyson sphere, or even something built by intelligent life, but certainly the process of even starting to build one, or any megastructure for that matter, would look quite odd.

Re: "just a century"?

[tnk1]

Well, I do agree with you that we aren't the supreme arbiters of what is possible in regard to physics.

In the defense of our primitive scientists, however, I would say that the models we currently have work so well that ditching them at the first sign of "unexpected behavior" is not really a good idea.

Additionally, given the age of the galaxy, there's really only two states that are overwhelmingly likely to be found in regard to Dyson Spheres: stars with completed Dyson Spheres and stars with no Dyson Sphere activity at all. The fact that we have found zero evidence for completed Dyson Spheres makes it significantly less likely that this is one in the process of being built, because even if it takes ages to build a sphere, it is unlikely to be constructed in the first place if it wasn't stable for some multiple of the build time. Otherwise, why build it?

None of that makes it impossible for this to be a sphere project in progress, but it would be a gigantic coincidence to find such a thing *first*.

Re:"just a century"?

[Bruha]

If they are capable of constructing such a structure, they've obviously mastered the process of turning energy into matter. Planets are not enough to build what's required to create a structure of this size. First 8 light minutes away means you're talking orders of magnitude larger surface area than the star itself just for our star. The first 4 planets don't have enough metals to construct a basic shell big enough to create something to dim our star by 20%.

The most difficult part is to ensure the parts remain in place. The simplest way is thrusters, there you have a system that would be converting the solar output at 100% efficiency to eliminate the pressure, or providing a thruster for counter balance. It would make sense to start as a ring around the star and keep growing it equally towards the poles. Which if the light has steadily been decreasing, that makes perfect sense as the growth of the surface are of the sphere grows so should the dimming of the star happen.

I'd love to know how they deal with CME's.

Another alternative is a floating artificial planet that can move between systems that just drains the star of it's hydrogen and they convert that into what they need and/or they use that process as part of building the dyson sphere so when it's complete they have a dwarf type star left inside that's tame enough for them to deal with.

Re: "just a century"?

[HiThere]

You don't understand how much matter is required for a Dyson Sphere. (Not that I think a real Dyson Sphere is a realistic plausibility...it's dynamicly unstable. Nearly as bad as the RingWorld.)

What I consider much more likely is a Topopolis (sometimes called Cosmic Spaghetti). Loops of mile diameter tubes that are flexible enough to spin for gravity. You don't make a complete orbit with any one strand, but you have LOTS of them a very slightly different orbital distances and at slightly different angles. And it would still take so much matter to cause the star to dim that you'd probably need to eat the planets. (First you scavenge any atmosphere and then you build a catapult on the surface.) But doing this in only centuries boggles the mind...even with nano-machinery. (Which isn't the kind of magic most people seem to imagine. Remember, life is nano-machinery. We might be able to do a bit better with careful design using a wider palette of minerals, but there turn out to be LOTS of problems with things like friction and surface tension, so don't expect multiple orders of magnitude of improvement in most things. Computation, though, may be an exception.)

Re: "just a century"?

[HiThere]

If all they needed to do was reproduce than exponential growth would make a few centuries a quite reasonable estimate. Unfortunately, they need to acquire the material out of which to grow, and that's going to slow things down A LOT. After the low hanging fruit is picked, then they need to go to distant locations to get materials, and probably expend a lot of energy (and radiate it away) to get it back to the building site. I expect that this would necessitate disassembling any planets for materials...if that would suffice.

Alternatively, if you assume that these aliens can somehow conjure matter out of nothing, then it's a reasonable time frame. I, however, find that too tough a bite to swallow.

Re:"just a century"?

[HiThere]

If they had an FTL drive, they'd be unlikely to build a Dyson Sphere, or anything that could be mistaken for one. (Unless they're all so addicted to video games that nobody want to have the lag of moving further from the server.)

Re:"just a century"?

[Beck_Neard]

I would be surprised if they _didn't_ build in a few centuries, and I think the guy in the article is being woefully reluctant to think about it a tiny bit.

A Dyson sphere in the form of a solid shell around a star is probably physically impossible, but a Dyson sphere in the form of billions of tiny orbiting satellites (which this anomaly could possibly be) is very possible and could be constructed in a distributed way. If there is some incentive for a person or company to build a solar satellite - say, to rent out its real estate - and this becomes profitable, the market will drive the exponential growth to make it happen. If it's a good investment opportunity, they'll start popping up all over the place and soon there will have to be regulations to keep people from building new ones.

Re:"just a century"?

[Chrontius]

Well, if we stick with the assumption that garden worlds - places where ecosystems evolve naturally - are somewhat scarce, but that it's easy to build places people like to live (but are ultimately designed places), having FTL, a Dyson sphere, and seeding those precious garden worlds so that they develop new ecosystems (us) is internally consistent.

This isn't even close implying my suggestion is correct, just that it's possible to produce an internally consistent narrative explaining such behavior to refute claims of impossibility.

Re:"just a century"?

[HiThere]

You won't get enough mass that way to build a Dyson Sphere, or anything even approximately similar. You could build several kinds of "starter sets", but you probably couldn't even get enough mass for a real Dyson Sphere even by disassembling the planets. (You might be able to build something as thin as a light sail, but how would you hold it in place. Besides, that would emit infrared radiation that wasn't detected. So you need something substantial enough to support nano-scale heat scavengers that reduce the frequency to down below the range that we were observing in. And those take mass too, because each one needs a cold radiator.)

Now somewhere I read that this was a trinary system, so perhaps if you disassembled the mass of all planets around 3 stars you'd have enough mass.

Re:"just a century"?

[HiThere]

You don't build habitable shells, you build cellular tubes. The suggestion I saw was a mile in diameter, rotating for gravity, and long. The cells connect into strands, but can be sealed off separately so that, among other reasons, you can have vacuum physics labs. You build lots and lots of strands at slightly different orbital heights and slightly different angles, so they interfere minimally with each other's solar panel wings. Each cell would effectively be a city. Or town with fields, or game preserve, or agricultural land. Etc. Each cell would have independent motive power, though not much. Probably ion rockets, because mass would be precious. And each cell could, in principle, attach itself to any other selected strand, though orbital energetic requirements would make doing that frequently, or to distant strands, problematic.

Re:"just a century"?

[RockDoctor]

If you're willing to believe in a civilization capable of building a Dyson sphere, how much more of a stretch is it to believe they could do it in a few centuries?
...

I mean, yeah, I have some idea of the energies involved, and I'm not sure I can envision a process that would run at that pace producing anything other than streams of plasma at gamma-ray temperatures.

You cast the problem clearly for yourself. Assembling some megastructure far smaller than a Dyson S(-phere/ -warm) would involve moving considerable masses of material from point A to point B, and changing it's momentum somewhere along that path. This is called "doing work".

Doing work produces heat. We don't see that heat. Problem.

Re:"just a century"?

[RockDoctor]

So, these magnificent engineers who can design and build two things that we can't do ("replicators" ; Dyson "things"), haven't grasped the importance of designing in safety in their tools - which is something that we at least try.

Hmm, there's a contradiction in there somewhere.

Re:"just a century"?

[RockDoctor]

(Unless they're all so addicted to video games that nobody want to have the lag of moving further from the server.)

For a Dyson thing the size of the Earth's orbit (actually, it's need to be a bit bigger, because this star is a bit brighter than the Sun), the server could be up to 16 light minutes away, if you did most of your signal travel by laser/ microwave. If you went round the outside, up to 25 light minutes.

Lag is not an appropriate explanation.

Inconceivable!

[Anonymous Coward]

... he thinks even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century.

Clarke's first law: "When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong."

Re:Inconceivable!

[Crowd Computing]

... he thinks even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century.

Clarke's first law: "When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong."

Clarke's third law would also be appropriate: "Any sufficiently advanced technology is indistinguishable from magic."

Re:Inconceivable!

[Aristos Mazer]

On any given day, 10000 people are encountering the concept for the very first time. The important memes warrant repetition or they are lost to the next generation. https://xkcd.com/1053/

From the wisdom of Sherlock Holmes...

[zorro-z]

"We must fall back upon the old axiom that when all other contingencies fail, whatever remains, however improbable, must be the truth." – The Adventure of the Bruce-Partington Plans

Translation: if no other explanations work, then "weird alien megastructure" could well be the last standing contingency, and therefore, the truth.

Discuss.

Re:From the wisdom of Sherlock Holmes...

[Jeremi]

"Sherlock Holmes observed that once you have eliminated the impossible then whatever remains, however improbable, must be the answer. I, however, do not like to eliminate the impossible."
- Douglas Adams, Dirk Gently's Holistic Detective Agency

Re:From the wisdom of Sherlock Holmes...

[AHuxley]

Re "weird alien megastructure":
What aliens would let their food supply or spare parts herd ie Earth get to see anything other than deep empty space to keep them calm and tender?
https://en.wikipedia.org/wiki/...

Re:From the wisdom of Sherlock Holmes...

[zippthorne]

You and Doyle make the same mistake. Assuming that one can enumerate a list of all explanations and then go about crossing off the wrong ones one by one, and further, that even assuming we can enumerate all of the explanations, possible and impossible, the subset of possible explanations numbers exactly one.

Re:From the wisdom of Sherlock Holmes...

[gtall]

Enumerating the explanations...how would that work? There isn't a recursive procedure to enumerate all and only the explanations. So we are left with picking a language, say English, and enumerating all the sentences in English. That's a bit tricky. We'd have to generate all strings in the alphabet in English (including spaces and punctuation) and then test each one for whether it is a valid or meaningful English sentence. I'll chose valid because meaningful is ill-defined. So we'd have to consider that "The two-headed rat with faces like Putin killed all those entities collected together under the roof of the mansion." We'd probably need paragraphs but we'll settle for run-on English sentences. We can throw out the ones that fail to meet the facts.

The ones that do meet the facts is infinite. Still, we must endeavor to accept the infinite, so we'll be at this for quite a while. Just before the heat death of the Universe, we'll stop and see what we have. Except that we live in an information limited environment, so we don't know about information that we don't know (cue Rumsfeld, or better Ross Perot, "That makes as much sense as two-headed rat choosing his favorite brand of cheese"). We are left with a possibly infinite set of explanations, some probably involving two-headed rats with heads that look like Putin.

Conclusion: stop reading fiction as though it were truth.

Re:From the wisdom of Sherlock Holmes...

[david_thornley]

Isn't that how science works? We observe something strange, and people start coming up with possible explanations based on the available data. Then they try to break the potential explanations by finding something they'd predict that is contrary to observation (sometimes going to great lengths to set up these observations). Given two potential explanations, we find where they differ in predictions of other things, and observe that. Unless the two are just one explanation expressed in different terms, and we can indeed observe what we want, Therefore, we should be able to figure out how many explanations are still possible, and it's entirely possible that the number is zero, in which case we need more potential explanations.

Re:From the wisdom of Sherlock Holmes...

[zippthorne]

Given two potential explanations, it is possible that the truth is neither one.

Its a tholian web

[Anonymous Coward]

Centuries ago the Tholians completed a sticky web around the entire star. After hundreds of years of collecting dust, rocks, ice the star is starting to dim due to accumulation of crap stuck in the web. There are also huge globs of rocks in one area where some of the stars planets and all of a nearby orbiting stars planets got stuck.

What about the "hot pole" theory?

[Anonymous Coward]

This star is larger than our Sun, yet it rotates thirty times faster. Its poles are significantly flatter, hotter, and brighter than the rest of the star. Thus a large object could block 22% of the star's light while covering a much smaller percentage of its disk. This also explains why the dips in the light curve are pointed on the bottom, not flat.

There could also be a large unseen planet (i.e. one that does not transit the star from our point of view) pulling on the star's tidal bulge and causing its visible pole to slowly precess away from us. That would explain the gradual dimming.

Re:What about the "hot pole" theory?

[minkowski76]

If only I had mod points. Good comment. Sad when the smartest comments come from ACs.

Re:What about the "hot pole" theory?

[Anonymous Coward]

Thanks, it was my first Slashdot comment in over a decade. The "hot pole" theory wasn't my idea of course:
http://gizmodo.com/that-so-called-alien-megastructure-could-just-be-a-dist-1738979646

Re:What about the "hot pole" theory?

[wonkey_monkey]

... hot pole ... bottom ... bulge ...

That is all.

Re:What about the "hot pole" theory?

[D'Eyncourt]

There are a couple of problems with your ideas.

Basically the most any planet in any star system could cover is approximately 2% of a star during a transit (as a comparison a transiting Jupiter seen from another star system would cover about 1% of the Sun). This is despite our estimate of when a planetary body would become massive enough to become a brown dwarf is about 80 times the mass of Jupiter because the mostly hydrogen gas in any gas giant is highly compressible. A planet with twice the mass as Jupiter would have a diameter only slightly larger than that of Jupiter, very much less than the 1.26 (= 2^[1/3]) growth that would be expected by simple linear growth.

If a body instead were large enough to become a brown dwarf, then the interplay of the light being generated by fusion at its core becomes more important and its size would balloon out to many times that of Jupiter. And, of course, a brown dwarf would be easily detectable spectroscopically.

Thus ANY planet in orbit around Tabby's Star that was transiting in front of it simply could not cause the brightness of the star to dip by as much as 22% as was once seen. There is the FAINT possibility that somehow what was observed was a planet within our own Kuiper Belt that happened to transit Tabby's Star during Kepler's observations, and that being MUCH closer to Earth than Tabby's Star's distance of about 1500 light years would allow it to cover more of that star, but there is the problem that a Kuiper Belt gas-/ice-giant should have been glaring obvious to our Spitzer Space Telescope which specializes in the infra-red range.

Your idea of the dimmer poles precessing towards us contains contradictory ideas: the planet causing this somehow has to be massive AND close enough to cause this, and yet has to have an orbit that is at least a couple of hundred Earth-years in length. This "newly" detected dimming was determined from photographic plates taken at different times from 1890 to around 1990.

My suspicion is that what we may be watching is a relatively short-lived (meaning less than tens of thousands of years) phase of Tabby's Star evolving from a main sequence star at the very earliest stage of becoming a (super-)giant. There is just barely enough helium accumulated at its core that its fusion only fitfully begins only to sputter out when the additional heat generated by that hotter fusion diffuses that core to below helium-fusion levels. Of course this "current" sputtering was generated tens to hundreds of thousands of years ago at the core (taking that long for the scattered light to reach the star's photosphere and thus become visible to us), but when helium fusion actually takes hold then the star ballooning out to become a (super-)giant will overtake that sputtering.

Re:What about the "hot pole" theory?

[drinkypoo]

People who post genuinely insightful comments as ACs do the rest of us a great disservice by not logging in, since we have to wade through the shitcakes to find the quality comments. You can have a slashdot login and remain anonymous, since Slashdot does not have a real name requirement.

If you have something meaningful to say, please log in. To do otherwise is to provide cover to trolls.

Re:What about the "hot pole" theory?

[drinkypoo]

As an AC you're at least somewhat immune against personal attacks and trolling.

Personal attacks and trolling are SOP for existence. Slashdot has helped me learn to not get discouraged by the pricks.

Re:What about the "hot pole" theory?

[Etherwalk]

If you have something meaningful to say, please log in. To do otherwise is to provide cover to trolls.

People have employers. Some employers require you to report online identities. (E.g. security clearances, major law firms, etc...) Others do not allow you to speak publicly on areas withing your purview without clearing it through PR.

I'd rather have the contributions of those people as ACs than not have them at all.

Re:What about the "hot pole" theory?

[Big Hairy Ian]

Nice point but how does that explain the increased dimming over a century

Re:What about the "hot pole" theory?

[drinkypoo]

But it seems to have helped you learn that who says something has some value attached to it over what they have to say.

Well, no. What it's helped me learn is that ACs are usually dumbshits. That there are a few great comments hidden among the dross does not change this. Most comments worth leaving are worth signing.

It's really a shame that ACs are taken less serious than other posters by you.

It's really a shame that Slashdot lets people post without logging in, because it produces far more shit than it does quality comments. Slashdot would be better off without the AC option.

I use to maintain a fairly low UID account here until I lost my mod points for not beating the open source drum.

I stopped getting mod points, so I set myself unwilling to moderate and stopped thinking about it. Moderation is broken here by design, notably because of the way karma is counted around the funny mod, and the very existence of the overrated mod.

Since them I refuse to bother with an account since Slashdot mods aren't based on rational ideas with good logical backing but instead it's a culture that loves and hates mostly on a whim and increasingly more so every year.

I loudly and proudly hold forth on numerous issues with a stance counter to the Slashdot groupthink, yet I maintain Excellent karma. Perhaps this place, while admittedly defective, is still broadly functional.

Re:What about the "hot pole" theory?

[drinkypoo]

As it is, if you have the "wrong" opinion, you're modded down, and if you have the "right" opinion, you're modded up. There is little exception to this and it's really quite embarrassing for a supposedly "intellectual" community.

Yes, you have to play political games of some sort. You can kiss editor asshole, you can suck up to the populace, you can speak as if you're an authority and hope everyone else agrees. I choose the middle path there most of the time. :)

However, this is how human society works. It's not like Slashdot is unique or even unusual in this regard. It can be depressing and discouraging, but I haven't failed to run into it anywhere.

Re:What about the "hot pole" theory?

[RockDoctor]

Thus a large object could block 22% of the star's light while covering a much smaller percentage of its disk. This also explains why the dips in the light curve are pointed on the bottom, not flat.

I don't think so. Unless the hot pole and the obscuring object are very closely similar in angular size, then you'll not get a tight peak, but a flat-bottom or complex-bottom profile. It depends very closely on the intensity profile of the "hot pole", and the sharpness of the edge of the shading object.

causing its visible pole to slowly precess away from us. That would explain the gradual dimming.

Hmmm, that might work. The pole would actually have to be on the limb at the moment ... and the progression wouldn't be linear with time.

Re: Shitty clickbait

[Anonymous Coward]

What's your explanation then?

It's not as if aliens are impossible, far from it.

fsck we're screwed.

[Anonymous Coward]

Maybe it's not an alien megastructure maybe it's an alien fleet heading straight to planet earth. As it gets closer and assuming they maintained their star being behind them so we all scratch our heads while it's getting closer.

Re: fsck we're screwed.

[Anonymous Coward]

And this is in fact even a tactic used in air fights in WWII. Pilots liked to have the sun in their back when they attacked because then the Enemy wouldn't see them.

Re: fsck we're screwed.

[pslytely psycho]

That tactic dates to the dawn of aireal warfare in WWI.

Re: fsck we're screwed.

[pslytely psycho]

Ok, I can't spell for shit after two bowls and a couple of beers......It's the weekend, but some asshole will feel it's his duty to point it out. Put your ruler away, you ain't my schoolmarm and you ain't whacking my knuckles.

Re: fsck we're screwed.

[amRadioHed]

Except in this case, the only reason we can observe them is because they have the star right behind them. Somehow I think super advanced space invaders would be smarter than that.

Multiple small stars close around a black hole?

[dsmatthews9379]

If it is not a group of objects shading a single star it could be multiple small luminous objects in a chaotic orbit close in around a black hole or some similar configuration that works if you reverse a few assumptions about what it could be. That would explain the absolute dimming effect without any infra-red getting past the shading object.

Planetary breakup?

[Anonymous Coward]

Roche limit reached about a century and a half ago, breakup continues. A super sized rocky planet which has migrated to within Mercury like distance of it's star and has subsequently been pulled apart. Put the planet in an orbit which is nearly edge on (which it would have to be to be detectable using these methods) and as the debris cloud increases in size the star is progressively dimmed (from our point of view) more and more.

Seems the most obvious explanation.

Interestingly, if you did want make a dyson sphere and you wanted a way to break up some planets to get access to the raw materials then causing them to shift orbits closer to the star might be a way to do it.

Planetary collision, leading to two planets breaking up? There really are all sorts of possible explanations without going straight to dyson sphere builders.

Re:Planetary breakup?

[Anonymous Coward]

Planetary collision would also be a good way to start the process of getting the materials of a Dyson sphere.

Captia: Harvest.

Re:ok.. Come on...

[Anonymous Coward]

> So right here, on planet Earth, the same types of people - scientists - are incapable of understanding how a large structure the size of the pyramids was built a couple thousand years ago..

There are lots of theories; there's no particular surprise that they were able to, but we don't know exactly how it was done because it was a long time ago and the Egyptian engineers didn't leave very good records. Nobody is going to be able to prove within a shadow of a doubt how it was done, but there are lots of plausible ways it could have been done.

https://en.wikipedia.org/wiki/Egyptian_pyramid_construction_techniques#Construction_method_hypotheses

This is old news

[Smiddi]

This happened over 1,400 years ago!!

Different perspective to the same problem

[OricAtmos48K]

What if the aliens are building a Dyson Sphere not around their star but into it ? Think about it ...

Re:"Old" news

[narcc]

I am expecting to read news here first, not after everyone has already published them.

You've been on this site for, I'd guess, around 14 or 15 years. What, in that time, lead you to believe that you'd ever see news published here in any sort of timely manner, let alone so quickly that you'd be likely to find it here first?

Slashdot has always had a reputation for bringing you yesterday's news tomorrow. If you're really still believe you should be able "to read news here first", the only way this site will meet your misplaced expectations is if you get your news here exclusively, never seeking out other sources.

I want some aliens

[caviare]

We can't explain it, therefore it must be aliens

Must be, must be!

I want some aliens

Now!

If the dinner won't come to us...

[MindPrison]

...then we'll come to dinner.

Why can't it be...

[thedarb]

a planet that's broken up, creating an asteroid belt?

Re: Why can't it be...

[Anonymous Coward]

Because that doesn't generate clicks

Re:Why can't it be...

[RockDoctor]

a planet that's broken up, creating an asteroid belt?

Because the dimmings are (1) too deep, (2) too irregular and (3) there's that pesky secular (century+) change too.

perhaps we should consider the obvious.

[Gravis Zero]

maybe the star isn't screwed in tightly enough. just give it a half twist and see if that stops the flickering. ;)

Re:perhaps we should consider the obvious.

[hoover]

I needed a good laugh just now, thanks for providing it ;-)

Re:perhaps we should consider the obvious.

[Agripa]

It is one of those new fangled compact fluorescent or LED stars.

Re: Night time?

[Anonymous Coward]

Well, I guess news according to toddlers might at least be better than Fox or CNN.

Lumpy Ring?

[Tablizer]

What if two large planets recently collided, creating a lumpy ring? The plane of the ring could have recently aligned in our direction more, due to relative star motion, accounting for the apparent change in magnitude. Or if the ring is recent enough, it could be "wavy" such that it doesn't always fully align with us.

Re:Lumpy Ring?

[RockDoctor]

What if two large planets recently collided, creating a lumpy ring?

The relaxation time is short - a few years at most. After which you get a relatively smooth ring. Plus you'd see a significant infrared excess from all the dust produced in the collision.

The plane of the ring could have recently aligned in our direction more, due to relative star motion, accounting for the apparent change in magnitude. Or if the ring is recent enough, it could be "wavy" such that it doesn't always fully align with us.

That requires a third body - a large planet or secondary star, neither of which are reported.

Alien stories

[Alsee]

I wish everyone would quit with the alien stories already.
It's obviously ghosts.

-

Kylo Ren

[Gumbercules!!]

So basically, Kylo Ren is sucking the energy out of the star to make a new StarKiller?

Re:Kylo Ren

[Jack Griffin]

Because if 3 destroyed Death Stars aren't enough, just try, try again...
Oh and thanks for reminding me of how shit that movie was. What the fuck was the Starkiller, a planet converted to a space station, or a space station built to look like a planet? I though it was a planet, but then it wouldn't have any propulsion which makes it pretty stupid. Oh man I better stop before I start a rant... Fucking stupid movie....

Re:Kylo Ren

[Gumbercules!!]

Starkiller wasn't even the worst thing... but I won't say anything because my biggest complaints are all spoilers.

Re:Kylo Ren

[dwillden]

Except that it appeared that shot number two would kill it's fuel/ammo supply. Maybe it could recharge from distant stars as well, but otherwise it was about to be obsolete. Unless it could move to another star system.

Re:Kylo Ren

[pseudorand]

Thank goodness I'm not the only one who thinks so. I hope Mr. Abrams made a boatload of money to compensate him for never being able to show his face in public again. I figured they couldn't possibly be worse than episodes 1-3 and might even be better with Abrams at the healm. But...wow. So sad. I think I'll go rent Die Hard XIV just to remind me that, by comparison, sometimes Hollywood sneaks in a bit of originality.

flush

[sociocapitalist]

"...he thinks even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century. What's more, such an object should radiate light absorbed from the star as heat, but the infrared signal from Tabby's star appears normal, he says."

Our grandparents couldn't imagine the technology that our children use today without thought.

How much hubris does it take to believe that we know what kind of technology 'advanced' aliens - or even the grandchildren of our grandchildren - will be able to achieve?

Re:flush

[CrimsonAvenger]

"A Logic Named Joe" by Murray Leinster (1946).

Mr. Leinster, at least, seems to have imagined some of the technology that our children use today. And he was a decade older than MY grandparents (and I'll be a grandfather soon).

But your point is still reasonable, if a longer timeline is used. Why should we expect that Charlemagne should have anticipated the modern world? And we should we think that we can anticipate the limits of the possible for our descendants in 1200 years (for those of you who are unaware of "Big Charlie", he was crowned Holy Roman Emperor in 800AD (and yes, it was neither Holy, nor Roman, nor an Empire, but that's what history likes to call it anyway - deal))?

Re:flush

[Aristos Mazer]

A fifth of the star in a century implies some numbers regarding minimum amount of mass necessary and the energy to move that mass. What I've seen elsewhere says that if there were going to be, say, a Dyson ring or Dyson sphere built that quick, the mass would have to be already in place, meaning the star would already be dimmed. Oh, there are some outside ways to compensate, which is why alien megastructure is still a possibility, but they're pretty extreme energy balances that we think we'd see being expended in such a system -- big increase in heat, for one thing. So alien megastructure is on the table, but considered unlikely, so other options are still being sought. Going direct to alien megastructure at this juncture is no different than going directly to "magic happened" or "some deity decided to change local physics". We must have more evidence to boost the probability of that option before it can be considered likely.

Re:flush

[Aristos Mazer]

Oh... and it might not be alien megastructures. It might be human megastructures after we invented time travel. Once we say "well, anything might be possible in the future", we open the door to all sorts of conjecture. There's brainstorming and then there's reasonable suspicion. At this time, alien megastructure is just brainstorming. Keep looking for data!

Re:flush

[ImprovOmega]

Let me offer a counter-theory. Let's assume that this is an alien mega-structure (work with me here). Now as you say engineering on that scale would require an energy expenditure that staggers the mind. So we have to assume they're using something that supplies ridiculous amounts of energy that can be rapidly produced. Our current problem with energy production is pollution as a by-product. But consider - if we had cheap access to functionally limitless (by our current usage patterns) clean energy then what would be the new issue? Heat pollution. All that expenditure of energy would be heating up the planet very directly and by large amounts even if we removed all polluting chemicals. Wouldn't it be reasonable then, if we assume an alien civilization advanced enough to be engaged in stellar engineering, that at some point in their development of energy production they figured out a way not to be radiating all of that excess heat as a by-product of energy expenditure? Because otherwise their home world would be a molten hellscape just from all the waste heat.

And yes, I know we have no concept or even a physical framework as to how that might even be theoretically possible, but then too we don't have the remotest idea about how to begin a stellar engineering project either - not without some major advances in physics at least - so I don't think we could rule out some kind of industrial heatsink model either.

What if it's not local to the star?

[Mal-2]

What if what we're seeing is not inherent dimming of the star from its own internal processes or by its own orbital objects and cloud, but by objects closer to home? In particular, is it possible that a particularly dense portion of the Oort cloud has slipped between the star and us? We're only starting to get a handle on Kuiper belt objects. We really have no idea what's in the Oort cloud or how it's distributed.

Re:What if it's not local to the star?

[abies]

Not sure about exact proportions, but Earth is rotating around the Sun. I have a feeling that anything in Oort cloud, big enough to dim that star regardless of position of Earth around a Sun, would also dim certain others stars nearby (in angle terms).

Re:What if it's not local to the star?

[Mal-2]

Fair enough, I'll sanity-check my figures and report accordingly -- whether they support my position or refute it.

The distance to the star is 1480 ly. The distance to the Oort cloud is 1.5-2 ly. Let's use the maximum since I'm trying to establish the minimum possible size of such an object. This is 0.14% of the way there, which would have very little effect on the required size of the object. It would have to be essentially two AU in size.

Two AU -- and that's the minimum necessary to explain the observations *right now*. This completely ignores the photographic evidence going back 200 years. 300 million km. That's a big fucking clump.

So while I'm not prepared to say it's impossible, I would agree it's pretty improbable.

Re:What if it's not local to the star?

[RockDoctor]

In particular, is it possible that a particularly dense portion of the Oort cloud has slipped between the star and us?

The time series for the Kepler observations is about 1400 days long. In that time the precession of the equinoxes will have moved the putative Oort clump 190 arcsec across the sky. Within that radius SIMBAD finds 6 other catalogued stars, including 2 other KICs (which were monitored for variations). These don't show such variations ... so, your hypothesis has to do some special pleading to repeatedly vary this star, and not others in the same field of view.

We really have no idea what's in the Oort cloud or how it's distributed.

We expect it to obey the laws of gravity (such clustering will either collapse or disperse rapidly, making them extremely unusual), and to closely follow the laws of statistics.

Re:What if it's not local to the star?

[Mal-2]

I've already shot down my own hypothesis simply by showing such an object would have to be nearly 2 AU in size to account for recent observations, even neglecting data gleaned from plates going back centuries.

Re:What if it's not local to the star?

[RockDoctor]

This completely ignores the photographic evidence going back 200 years.

From the recent paper :

The long-term trend in the DASCH [archived plates] light curve can be described in various ways. One way is simply to note that KIC8462852 faded from B=12.265 +/-0.028 in 1892.5 to B=12.458 +/- 0.012 in 1987.5, for a total fading of 0.193 +/- 0.030 mag in 95 years. This fade rate is +0.203 +/- 0.032 magnitudes per century (dashed line in Figure 1).

Which is nice and simple. But there is always a "but" :

This end-to-end trend line provides an excellent representation of all the Harvard data except for the decade from 1900-1909. The individual plates for this decade show a similar distribution of magnitudes as in adjacent decades, except that there are many more fainter magnitudes (from 12.6 - 13.0). This might be due to the star suffering many deep dips during the years 1900 - 1909

So that's a very interesting and suggestive set of results.

And unless someone has a secret stash of plates somewhere (with all the necessary attendant data), the photons have gone by and we'll never see them this side of the heat death of the universe.

If that suggestive dip in 1900-1909 was another outbreak of "dipping" such as we've been seeing in Kepler data, I think we can take your Oort cloud hypothesis round the back of the barn with a chopper.

It's an interesting one, this variable star.

Re:What if it's not local to the star?

[RockDoctor]

I saw that later. But it was a hypothesis worth addressing.

I spotted another issue since.

Given the 1905 (+/-5) and 2005 (+/-5) putative bouts of dimming, AND the 1890-1990 trend in dimming ..

If the long-term trend is due to construction of a mega-engineering project, then the bouts of dimming indicate that they hadn't got their construction debris under control ; this is not good.

Alternatively, if the 1905 (+/-5) and 2005 (+/-5) putative bouts of dimming are due to the mega-engineering project, then WTF are they doing to the start to DIM it fairly steadily?

One way or another, it doesn't look like engineering. (Not that I believed it was, for one second.)

Re:Shitty clickbait

[TheRaven64]

I stopped reading New Scientist about 20 years ago, and that summary doesn't sound too unlike my recollections of it. Did it improve for a bit in the middle?

Re:"Old" news

[stealth_finger]

I beg your pardon, but this is already old news. It has been relayed by other channels at least two days ago. If /. still want to pretend being news for nerds, they have to catch up and post news when they are news, not two days later.

This comment is old news. Seeing as slashdot isn't a news site it's always been like that, it has no writers or reporters. All it is, is some people that put up interesting articles from elsewhere and then we all bitch and moan about all kinds of things, sometimes the original article may get a mention or may not depending how it goes.

I will welcome the Dyson Sphere overlords

[freedom_surfer]

I for one will welcome our future Dyson Sphere building overlords.

Lipton Sphere

[itsdapead]

If you're willing to believe in a civilization capable of building a Dyson sphere, how much more of a stretch is it to believe they could do it in a few centuries?

You're all wrong - the star is clearly orbited by a huge swarm of teapots. After all, we can't hope to understand the thinking of a race capable of building such a "Lipton Sphere" so you can't prove its not teapots.

I'm not sure I can envision a process that would digest entire planets worth of material and cast it into a shell at any pace.

PS: I thought the original Dyson Sphere concept was a huge cloud of satellites that eventually grew to capture most of the star's energy.
PPS: The satellites could still be teapot-shaped.
PPPS: The tea-cosies are blocking the infra-red. Nothing worse than cold tea.

Re:Lipton Sphere

[itsdapead]

That would *take* entire planets worth of material.

Of course - but you don't have to transmute that material into scrith (a.k.a. unobtanium) to withstand the stresses in a rigid, non-orbiting, 1au shell, and if you're sentimentally attached to gravity you can easily spin parts of the individual satellites, whereas with a big sphere or ring you have to to plate it with neutronium, invent artificial gravity, or spin the whole shell up to ludicrous speed (ISTR when Larry Niven re-did the math for Ringworld Engineers it turned out that it would need a gas-giant's worth of hydrogen just to spin up). Plus, you can build them one by one over an aeon or two - the more you build, the more energy you have. Nobody is saying it has to capture every last photon...

Not saying its easy - just easier than a big solid shell...

Space is surprising

[danieldids]

After Kepler finding so many different planets and even here in the solar system where we have so much bizarre conditions (like life) in planets and moons, I wouldn't think that having so many comets around a star is an implausible idea after all. Or aliens. Space is big, all variations of conditions have a big chance to occur. We have life here on Earth (which is a incredible rare event, for sure), we have nitrogen or carbon dioxide blocks sliding down hills on Mars, we have geysers of ice on moons around jupiter, we have underground oceans on a moon of jupiter which surface look like a giant cheese cake with sugar on top of it , we have lakes of methane on titan, even Pluto has a Pluto face draw on it. The sun itself is a wonder, a ball of hydrogen emitting light for billions of years (i find this amazing). i know science has to prove things, but not believing something is not possible in such an enormous universe is silly.

Dyson Swarn

[rnmartinez]

Sure I am dreaming big here, and this is probably some kind of natural phenomena we have never observed before, but why a sphere and not a swarm? OK so if 22% is only covered, this thing looks to be moving, and their Sun is a lot larger than ours, than maybe it is just a Dyson swarm. I mean how much energy do you really need? Regardless, I feel that cool observations like these merit better observation. I know that this thing is ridiculously far away, but why aren't we building tech to launch small probes (maybe the size of baseballs) and communication satellites around other planets - I mean eventually we will need something like Internet access on Mars, Saturn, etc.., so can we have a network of tech to help us gather better data, and gather it quicker? We could be launching small probes at very high speeds, even if its just to the edge of our solar system, and probably be learning some very cool things. I just feel that even if this is some kind of alien megastructure, we won't be able to gather enough proof to make anyone happy. Sure its far away, but imagine that maybe it was only 5 or 10 light years away. Would we really be able to gather the data we need to make an informed decision?

Maybe the star is just depressed

[Aristos Mazer]

"I just don't feel like shining any more. I'm watching the sentients on my local planet, and they're just mean to each other. It's so sad to watch. I give up. I'm tired of burning hydrogen for these ungrateful whelps. All this fusion for them is giving me iron streaks! Not worth it. I'm going to go spend a few petaseconds focused on some other projects that are less work intensive for me."

Dim-witted assumptions

[geekmux]

"...he thinks even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century..."

So, alien megastructures are a possible theory here, but for some reason we want to sit back and believe that construction is the main reason the theory is bunk?

No wonder people on this planet still believe aliens built the pyramids. Seems rather stupid and ignorant to even theorize about limits of alien capability.

Speaking of construction, 100 years ago humans were still marveling at the internal combustion engine...not that we "dumb" humans have really done anything with that technology in the last century...

Re:Some Poles are totally hot...

[Aristos Mazer]

Sad truth: the messenger matters to how we get the message. We've seen a slew of stories along those lines -- physics tests lower if gender is known, violin auditions need to be anonymous to be judged on sound quality, insufficient peer review given to bad ideas of famous scientists such that death is the only thing that opens up the field to opponents (I can't find my citation on that one, but it was in the news last year), and just the fact that we reject ideas that come from political opponents, regardless of facts. But at the same time, true anonymity makes people behave in a much crueler way (much better cites exist, but this one will do for today). And all those "AC" labels make it hard to carry on a conversation -- I can't tell when the same person replies to me. Also, that name eventually develops a reputation for making good comments, which makes it possible to dredge out of the morass of people who just dump inanity, attacks, or lies -- those get recognized over time. The pseudonym of Slashdot seems to me to be a pretty good compromise. Pick a number to be your screen name, something large and random to avoid any connotations. But give me something to see you as a source of information.

seems conceited

[argStyopa]

Seems rather conceited for us to say "there's no way they could cover 1/5 of a star in a century" when little more than a century ago one could have found plenty of 'experts' who would poo-poo the idea of powered flight.
Hell, only 30 years ago, nearly every single civilian phone in the world was somehow attached to a wall.

And as far as his comments about black-body radiation from such a structure, it doesn't seem terribly unreasonable for a civilization capable of such engineering such a megastructure in the first place, to have figured out how to convert heat energy into something more usable/consumable.

Yes, I'll be honest: part of me would love there to be evidence of other life in the universe.
OTOH, part of that would be absolutely terrifying. (http://rithmomachia.blogspot.com/2010/04/why-we-should-quit-searching-for-alien.html)

Re:seems conceited

[Theaetetus]

And as far as his comments about black-body radiation from such a structure, it doesn't seem terribly unreasonable for a civilization capable of such engineering such a megastructure in the first place, to have figured out how to convert heat energy into something more usable/consumable.

I think the easiest explanation for that comes from the premise of the Dyson Sphere itself - you're building the thing because you want to capture the solar output energy, so simply putting an optical shell around it and having it radiate that energy in IR doesn't actually help you. Obviously, you're using solar panels and/or mirrors to capture the energy and then retransmitting it to your preferred processing site. Maybe you've got bunches of microwave transmitters on the surface beaming high power (but narrow and not visible from Earth) rays to orbiting factories that are running particle accelerators to make antimatter for your spaceships. Maybe they're even beaming it out beyond that solar system, but to another one that's not in line with the Earth.

The "sun generates X energy, so a Dyson Sphere should radiate X energy as IR" incorrectly assumes that you build the sphere for funsies and never attempt to use that energy.

Re:seems conceited

[Agripa]

And as far as his comments about black-body radiation from such a structure, it doesn't seem terribly unreasonable for a civilization capable of such engineering such a megastructure in the first place, to have figured out how to convert heat energy into something more usable/consumable.

Like more heat at a lower temperature?

Forget Dyson Spheres. When they reverse thermodynamics, *then* I will be impressed.

http://www.projectrho.com/publ...

We only have one rule....

[Dareth]

We only have one rule....is that you obey the laws of physics in the house. My kid is so bad about bouncing off the walls, literally.

Easy explanation!

[DarthVain]

Dark Matter. Or Black holes. Possibly something to do with string theory. Or any of the other astronomical whipping boys the physicists cart out when they can't explain something.

Stellar Husbandry

[Baldrson]

TFA says: even advanced aliens wouldn't be able to build something capable of covering a fifth of a star in just a century

According to a stellar husbandry proposal you could cover 1/5 of a star with more than 1/2 inch of material (water density) at 1 astronomical unit radius.

10e21kg/year;4*pi*au^2/5;1g/ml?cm/century
([{1E22 * (kilo*gramm)} / year] * [{(4 * pi) * (au^2)} / 5]^-1) * ([1 * gramm] / [milli*liter])^-1 ? (centi*meter) / century
= 1.7779051 cm/century

Comets Can't Explain Weird 'Alien Megastructure' .

[drolli]

Thats why comets should not be scientists.

Re:Spooky!

[abies]

Not long distance travel, enumerating all names of God...
https://en.wikipedia.org/wiki/...

Missing Infrared Signature

[ImprovOmega]

I just feel obliged to point out that if we are positing an alien civilization that can construct a Dyson Sphere/Cloud that blocks out fully 20% of a star's radiant energy in just under a century then why would we possibly assume that engineering that advanced would necessarily radiate excess infrared heat signatures from such a massive engineering project?

Re:simpler explanations

[abies]

It has to be pretty big rock, to occlude the star at every position of Earth around the Sun. If it is near 'them', it has to be at least in order of magnitude of star size. If it is near us, it has to be around size of 2AU, which is pretty big for 'rock'.

Star turning into a Black Hole?

[minogully]

I'm not an astrophysicist, so there's probably a huge hole in this theory. Please anyone with greater knowledge on the subject comment.

What would a extremely massive star turning into a black hole look like? And how quickly would the process take?

Let's say there's a extremely massive star on the brink of becoming a black hole. Then a comet or some other small object falls into this object and pushes the inner core of the star over the tipping point. The inner part of the star outside of the black hole core would still have strong enough gravity to generate fusion, but the star's output would be reduced.

Then as more objects fall into the star the event horizon's diameter increases and the star's output decreases.

Thoughts?

Re:Star turning into a Black Hole?

[RockDoctor]

What would a extremely massive star turning into a black hole look like? And how quickly would the process take?

This process is one of the prime contenders for what is going on when you produce a Gamma Ray Burst. Duration from under a second to a couple of hours.

different characteristics ; different processes.

Re:Maybe they're not building it...Wrong Direction

[HiThere]

If they were moving it, they would need to be moving it towards the star to explain the observations, not towards us.

OTOH, he already said that Infrared observations had eliminated that option. I believe he was a bit to glib there, however, as generally infrared observations are only done at a few wavelengths, and if they were building a macro-scale structure they probably have nano-scale heat scavengers, which would result in the radiation being emitted in the long infrared, which is not usually observed. (Observing ANY infrared at long distance is already quite difficult. Usually it requires something like liquid helium coolants.)

That said, alien megastructures would be an extremely unexpected finding, and would need stronger evidence to be accepted.

Re:ok.. Come on...

[khallow]

It's Wikipedia so it's hardly credible.

Look at the citations then.

Though what I'd say is that most of the far fetched notions found there don't come close to explaining all situations and scenarios played out in Egypt. Correction. Elsewhere in the world such as Peru or England, with Stonehenge recently. Or how they found the rest of the statues (i.e the rest of the body) for the giant heads at Easter island yet another huge feat. There are amazing structures being uncovered all the time; even ones below the earths surface and have very little plausible explanation behind them.

What's supposed to be hard to explain? For example, Egypt of the time had plenty of manpower, plenty of time, and some good engineers. The same goes for the other places you mentioned. The feats discussed are well within their capabilities.

Quantum Teleportation

[Tenebrousedge]

Scientists have already figured out how to transmit information via quantum entanglement. Is it really so hard to believe that in another few hundred years that could maybe be developed into a transporter?

Yes. You clearly worship at the altar of Science but have no idea what it is. We can expect many things in the future but wholesale violations of relativity is not one of them. On a quantum scale some effects do not obey the principle of locality, but this effect cannot be used to transmit information, and even if it could there's nothing to suggest that the transference of quantum state has anything to do with physically moving anything anywhere.

No matter what happens in any arbitrarily long span of scientific development, red will not become blue, down will not become up, and neither (classical) information nor human craft will exceed the speed of light. To believe otherwise is to believe not in science but in fairy stories.

Re:Quantum Teleportation

[TangoMargarine]

Thanks, Nostradamus.

Re:Quantum Teleportation

[Tenebrousedge]

Most parts of relativity have been verified down to a stupefying level of precision. It is an accurate description of the universe from the cosmic scale to the atomic scale. You're proposing that there are unicorns somewhere past there. It may even be true, but science has put some hefty constraints on what kind of unicorns may exist. Also, breaking the laws of physics to allow for your preferred fantasy scenario tends to have serious negative consequences. For example, if FTL travel or information transmission exist, then you have to give up the idea of causality, since it would be trivial to arrange for events to precede their causes. Nonlocal quantum effects are bad enough, thank you.

It does not take Nostradamus to understand that gravity will still exist in the future. You seem to think that's up for debate.

Re:Quantum Teleportation

[TangoMargarine]

No of course not--don't be ridiculous. We are known to, however, find surprising loopholes from time to time, that lead to reconsidering theories formerly considered set in stone. Not to dismiss them*, but to revise and make them more accurate.

The very spirit of science is skepticism. And you're bashing me because I still think surprising discoveries might be made at some point in the future? Get real. One can be skeptical without diving into "the land of magical unicorns," as you put it.

I say good day, sir.

* Have we dismissed Newtonian physics already? Superseded by relativity? I'm not cozy with the terminology.

Re:Quantum Teleportation

[ErkDemon]

" No matter what happens in any arbitrarily long span of scientific development, red will not become blue, ... "

A signal viewed from an environment with a more intense gravitational field is seen to be shifted to the shorter-higher-energy end of the spectrum. It's called gravitational blueshift. Red emitted light, viewed from the bottom of a sufficiently deep gravity-well, can in theory be seen to be blue. Or you could have the source and viewer approaching each other at high speed, and use the conventional Doppler blueshift to turn red into blue.

" ... down will not become up, ..."

Gravitational fields can be intransitive. If two identical observers orbit the same fast-spinning star on opposite sides, then the star's rotation creates an associated gravitational effect that pulls matter preferentially in the direction of the star's rotation. When the two observers exchange signals, observer A can appear to be higher than B according to signals sent one way around the star, but lower than B according to signals sent the other way.

... and neither (classical) information nor human craft will exceed the speed of light.

That depends on which speed of light, whose speed of light, and whether we remember that in physics, we normally talk about velocities rather than speeds, except in situations where the averaged round-trip signal speed is used to define a coordinate grid (which tends to happen in relativity theory, because we find coordinate grids comforting and reassuring). If you want to travel faster than the "cartographic" background speed of light, it's easy – just freefall or dive into a black hole, and when you pass the r=2M radius, you should be moving faster than distant background lightspeed. Of course, you won't be travelling faster than your own local light, because that's infalling too, so no physical paradoxes. Admittedly, the interior of a black hole is probably not somewhere that most people would want to travel to at high speed ... but that's a different problem. Theorems that forbid super-fast travel tend to assume that lightspeeds have to be isotropic (because that was a simplifying assumption made by special relativity), whereas in reality, they're not. You can travel (in theory) as fast as you like, as long as there's a suitable gravitational gradient pointing in the right direction. Special relativity's geometry isn't necessarily valid in the presence of gravitational gradients, and/or lightspeed anisotropies.

" To believe otherwise is to believe not in science but in fairy stories. "

IMO, Science (when it's done properly) isn't supposed to be about beliefs, it's supposed to be about working hypotheses. When people start "believing" too much of what they're told, that's when science often goes bad.

Re:Quantum Teleportation

[Tenebrousedge]

We know that these theories are valid over a certain domain to an extreme degree of accuracy. Are you disputing those measurements? Are you skeptical of empiricism itself? No, I maintain that you have no idea of what you're even suggesting.

The difference between Newtonian physics and relativity is an exceedingly fine one; over the domain Newton observed it does not exist. Nothing will ever overturn Newton's theories in that sense. Similarly, Einstein's theories are empirical fact and will not stop being an accurate description of the geometry of the universe (over the scale to which it applies, i.e. just about everything) in any day of the future. That geometry tells us that things like antigravity and FTL are barely even expressible, and completely impossible even if there were some sensible reason to want them to exist. That will not stop being true at any day in the future. See also: thermodynamics.

You are not being skeptical. You are being stupid. If you were skeptical, the proper attitude would be to not believe in Star Wars without evidence. Having some idea what it is you're arguing about would be good too -- just because we don't know everything does not mean we know nothing, or that anything is possible.

Re:Quantum Teleportation

[Tenebrousedge]

Thank you for a collection of dressed-up semantic arguments. Next you'll tell me that white is black if you squint hard enough. As part of human-normal experiences go, red will not ever suddenly decide to change its spectrum, Earth's gravitational pull will not suddenly cease to exist, and special relativity will continue to be a thing. Which is to say, all future theories must predict all current and historical measurements, and what we've measured so far rules out most futuristic fantasy worlds and omnipotent aliens.

Re:Quantum Teleportation

[david_thornley]

You seem to assume that c is the local speed of light or something, which it isn't. Light goes slower than c under quite a few situations, and it's possible for things to move faster than light does depending on conditions, but they can't exceed the speed of light in a vacuum. Further, if we have Special Relativity and FTL travel (defined as faster than c, not faster than local lightspeed) and/or communications, we have time travel and/or the ability to send messages back in time.

Re:Quantum Teleportation

[ErkDemon]

Thank you for a collection of dressed-up semantic arguments.

I wasn't aware that they were dressed-up! :) Semantic analysis is often an important tool in the more abstract branches of theoretical physics. Think about how often Einstein demanded that we reexamine exactly what we really mean by, say, "distance" or "time" in a given situation.

Next you'll tell me that white is black if you squint hard enough.

That's you indulging in a fantasy future scenario. Scientific debate is usually more constructive when people spend more time addressing what each other have actually said, than what they can imagine each other saying.

... , all future theories must predict all current and historical measurements, ...

No, they have to predict most current and historical measurements, and an explanation should be available for any remaining mismatches (e.g. human fallibility, test theory limitations, peer pressure, etc.). The explanation for those mismatches can legitimately be social/psychological rather than based on fundamental physics (e.g. expectation bias).

People screw up, and physicists are people. The experimenter is part of the experiment.

If we always required perfect agreement with reported results, then special relativity woud have been dismissed, because the first peer-reviewed published experimental paper on testing SR concluded that the theory didn't make a great match to the experimental evidence. With hindsight, we now consider that first experimental paper to have been flawed.

Remember also that in the early days, Darwinian evolution was supposedly soundly disproved by thermodynamics applied to the available experimental data. Instead of killing the theory, we kept it, and later on our knowledge of physics changed in such a way that Darwin's idea turned out to be compatibe with the new calculations.

We can't (and shouldn't attempt to!) generate all peer-reviewed historical measurements from a physical theory, because many of those results are now known to be bad, and/or mutually contradictory. Consider all the early experiments that claimed to have either verified or disproved the existence of gravitational shift before around ~1959. With hindsight, all of those early g-shift experiments, including the ones that got the right answers, and the occasional prize-winner, are now considered to be junk science and not to be included in any proper scientific review of the evidence. We have to assume that the currently accepted dataset may include the occasional rogue element, which we may have overlooked because it agreed with our expectations.

While I understand the argument that agreeing with all currently-believed experimental data is a great test for a theory, I would suggest that an even more powerful theoretical success would be for a theory to disagree with the ocasional known result, so that when we go back and retest those results in the light of the new theory, we find that the original results are unsound. I'd suggest that a theory of this sort that is only 99% compatible with known results is actually more scientifically falsifiable, and has potentially greater predictive power han one that has been tailored to exactly correspond to all currently accepted results, as a retrospective curve-fitting exercise.

A "99%" theory (if validated) can reveal to us previously unrecognised problems and mistakes in the existing peer-reviewed record caused by human fallibility, whereas a "100%" theory is partly defined by any such fallibilities and helps to perpetuate them.

Re:Quantum Teleportation

[ErkDemon]

David: Try that black hole example. Your nominal terminal velocity at the horizon equals lightspeed, and deeper in, it's more than lightspeed. It can be entirely legal to travel faster than background speed of light, and even the local speed of light, as long as you aren't exceeding the local velocity of light, in the direction of motion. You just probably won't be able to report your success back to any observers outside the hole. :)

That's the basis of the Krasnikov tube idea. You activate the tube, ride the artificial gravitational gradient to your destination arbitrariy fast, then, if the tube polarity is reversed, ride it back again, arbitrarily fast. The way your signals get mangled means that round-trip SR-style definitions of dates and times go all to hell, but those definitions also break down in some pretty mundane everyday situations, and as long as you don't actually arrive before you left (and why would you), there's no underlying causality paradox. The optics get scrambled, but that's about it.

Certainly, the SR definitions go a bit mental in this scenario, but they also go a bit mental in the presence of conventional gravitational fields, and we don't say that therefore gravitational fields can't exist ... we say that SR doesn't claim validity in the presence of significant gravitaitonal fields, because the field gradients violate the basic geometrical assumptions that SR was built on.

So trying to disprove the existence of warp drives using special relativity is a bit crazy. Trying to disprove "metric engineering" solutions by using a theory that presupposes flat spacetime is like trying to disprove the viability of aerofoil-based heavier-than-air aircraft designs by presupposing the absence of air. One can certainly obtain a rigorous disproof, but the disproof is pretty much worthless, because it's based on the simplifying assumed absence of the very effects that are required to make the hypothetical mechanism work (in this case, gravitational distortion).

This doesn't necessarily mean that we really can build a practical warp drive – there may be other insuperable obstacles – but the usual reasons given for why we can't do it are ... let's say ... not especially intelligent.

Re:Quantum Teleportation

[wierd_w]

I realize this is an old topic now, and you are unlikely to respond, but all the same:

The alcubierre warp drive does not exactly violate c. The ship itself remains motionless inside its local spacetime. What happens instead, is that the spacetime just outside that which contains the ship is bent like hell, and causes contraction and expansion at faster than light speeds. This drags the local spacetime around with it.

So, the issue with "Hey, I can go backwards in time with it!" is avoided. The ship has normal causality inside its local spacetime. it does not have time dialation, because the ship does not move inside that curved spacial geometry. What happens instead is that an event shock forms around the ship, preventing information from entering or leaving the pocket of spacetime inside, and the whole bubble rips off like a bat out of hell. The event shock interacts with matter and virtual particles as normal space is compressed in front of the vehicle, and that energy builds up like bug splatter on a windshield.

When the vessel exits FTL mode travel, it will release that accumulated energy.

The equations for the alcubierre warp drive are sound in terms of theoretical physics. The devil is in the details. It requires an exotic material with negative mass, or requires exotic negative energy. The only contender for this exotic negative energy is the casimir effect, but the effects of that phenomenon are much too small to be useful to create a warp drive.

An alternative may however be possible. Spacetime is not "empty", even in an otherwise perfect vacuum. There is always some level of background energy/particle phenomena in the form of short lived virtual particles. If a means of modulating this energy density can be found, reducing the rate of virtual particle pair production will have similar consequences to having negative mass or negative energy present. That would satisfy that requirement for alcubierre's warp drive physics.

Is there a way to modulate/control the rate of virtual particle pair production? Hell if I know.

Re:Quantum Teleportation

[david_thornley]

Special Relativity doesn't apply unmodified in gravitational fields, and it is possible for spacetime to expand at a rate greater than c, yes. ISTM that the way you avoid time travel or paradoxes is that you aren't coming home again.

I'm aware of the Alcubierre warp drive and the problems, and I don't have a handy bar of something massing -10kg around, sorry. (I also don't get the math and physics, and probably never will, but I'll take the word of people who know a whole lot more about it than I do.) However, it travels FTL from our point of view, which means of course that it travels FTL from all points of view we can find.

Therefore, it seems to me that it contradicts Special Relativity or it enables time travel. Personally, I'm more willing to accept time travel than I am to give up Special Relativity. When I was a kid, time travel was a science fiction trope, that nobody took seriously (even if Asimov did write some papers on thiotimoline). Physics got weird a little over a century ago, and it's been getting weirder ever since.

Dyson Sphere can not exist!

[jraff2]

Attempting to build a entirely enclosed sphere around a star would result in MASSIVE support structure to hold the top and bottom away from the star, almost impossible! Yeah one could have a ring or partial sphere, but not the whole thing. It would collapse.

Von Neumann machine?

[seven of five]

In 2001 and sequels, A C Clarke postulated von Neumann-type universal constructor, the first job of which is to make more copies of itself before proceeding to the main task. Given that approach, the main constraints to speed would be the speed of delivery of energy and raw materials. Why would you need even a century?

Alien Structure

[PPH]

But not a Dyson sphere. It's called a Baf'cnar Sphere. Named after it's inventor, from the planet Gluk Erusha. Dyson is just some guy that sells weird vacuum cleaners which don't work worth a damn. Have you ever used one to get dirt out of a vacuum?

Occam's Razor

[14erCleaner]

Rather than assuming aliens, it's far simpler to assume it's a natural phenomenon, like a cloud of dust passing between us and the star.

You fools!

[sabt-pestnu]

When the star goes out in only a few thousand years, the weapon will be fully charged and ready to fire!

It has to be true! I saw it in a movie somewhere...

Starkiller base

[famebait]

It is clearly orbited by a starkiller base. Or at least that's about as likely as a Dyson sphere.

Probably already nuked....

[kev_at_monash]

Massive chunks of nuked planet orbiting the star.

Dyson

[jaq1an]

Sphere

Less than 1400 years and counting

[kwiecmmm]

If this is a Dyson Sphere we have less than 1400 years before they will see a transmission from us. And then we need to hope they are friendly or just don't care about primitive planets.

If they are building a Dyson Sphere they started this before 600 AD, and our technology is not going to be anywhere close to what they will have.

IR signal

[Keith Henson]

If we are looking at a giant alien version of the James Webb telescope, we would not see excess IR.

Russ Meyer had breasts?

[Latent Heat]

I guess that's what men get as they put on some pounds as they age?

Eclipsing planetary system

[u19925]

Could there be another planetary system eclipsing this? If there is a faint brown dwarf and few planets orbiting it at a distance of 100 ly, then eclipsing by such a s system can explain this anomaly.

Re:Eclipsing planetary system

[RockDoctor]

If this happened over a year or several, that would remain more or less in the realm of possibilities. But the recent publication shows there is also a semi-regular decline which has been happening for a century, and possibly (possibly!) another period of dimmings just over a century ago.

See my comments up-thread for references.

Re:So

[RockDoctor]

That's the question.

Re:simpler explanations

[RockDoctor]

2 AU diameter is ~150*10^6 km = 1.5*10^8 km = 1.5*10^11 m radius.

Volume is then 1.4*10^34 m^3.

Let's pick a number from http://www.lpi.usra.edu/books/... for the density. 2g/cc sounds a very convenient number (2000 kg/m^3). That makes the mass 2.8*10^37kg.

About 15,000 solar masses. I rather think we'd have noticed it.