Complex Life May Be Possible In Only 10% of All Galaxies

sciencehabit writes The universe may be a lonelier place than previously thought. Of the estimated 100 billion galaxies in the observable universe, only one in 10 can support complex life like that on Earth, a pair of astrophysicists argues. Everywhere else, stellar explosions known as gamma ray bursts would regularly wipe out any life forms more elaborate than microbes. The detonations also kept the universe lifeless for billions of years after the big bang, the researchers say.

Comments

Let's do the math

[cat_jesus]

10% of infinity is...... hmmm, carry the one...

Um 7?

Re:Let's do the math

[i kan reed]

I think you'll find that the density of life is indeed important to our chances of ever discovering any.

Re:Let's do the math

[Skarjak]

As far as we know, the Universe is finite.

Re:Let's do the math

[Kjella]

Not really, space may be infinite but as far as we know there's a finite amount of energy which by E=mc^2 means a finite amount of mass and since there's a lower bound on the mass of a star and stars to form a galaxy the number of galaxies must be finite.

Re:Let's do the math

[JWW]

Ummm I think you've confused ridiculously large number with infinity. They are not the same thing.

Re:Let's do the math

[jeffmflanagan]

We don't get to the point of galaxy hopping. Our machine descendants might, but the human race would be long dead by the time a ship crossed into another galaxy.

Re:Let's do the math

[kuzb]

There is no real evidence to support an infinite amount of mass. So your "math" has no relevance.

Of course, when dealing with 100 billion galaxies, 1 in 10 is still really good odds.

Re:Let's do the math

[king neckbeard]

To anyone currently alive, an infinite universe and one with 100 billion galaxies are indistinguishable. We were previously weighing a practically infinite universe with a practically infinitesimal chance of life, but the numbers seem to have been getting better overall, and the conditions in which life can exist have also expanded considerably.

Re:Let's do the math

[ColdWetDog]

More like 34.

Re:Let's do the math

[gameboyhippo]

Space is not infinite. It is expanding.

Re:Let's do the math

[Ravaldy]

That's just your opinion built on limited knowledge of physics. Our progression in the last 100 years is more than 1000 fold all previous years combined so imagine what we can do in the next 1000 years.

Re:Let's do the math

[buchner.johannes]

While the Universe may be infinite, the Observable Universe is not infinite (limited by the speed of light).
The Universe within a radius of a certain number of light-years (and thus of age comparable to our location) is also finite. So considering the galaxies younger than 5 billion years, the number of those galaxies that can be observed (and can contain life that could communicate/meet with us) is finite.

A quick calculation gives me that the number of galaxies is 170 million. Neglecting very small, dwarf galaxies, which are more numerous but have drastically fewer stars, I multiplied the stellar mass density by the comoving volume up to z=0.5.

Re:Let's do the math

[Shatrat]

If that's what you're worried about, we already know that this particular galaxy supports life. Our chances of finding it in one of the others was astronomically smaller anyway.

Re:Let's do the math

[CreatureComfort]

Maybe invent a flying car?

Re:Let's do the math

[khallow]

Our progression in the last 100 years is more than 1000 fold all previous years combined so imagine what we can do in the next 1000 years.

Will there even be an organism recognizable as human in another 1000 years? There's more than one way for humanity to cease to exist.

Re:Let's do the math

[boristhespider]

No, it's definitely false. Current data strong favours a universe that is flat (ie infinite), while it only narrowly supports a universe that is open (ie infinite and shaped like a foliation of saddles), and only slightly better favours a universe that is closed (ie finite and shaped like a foliation of spheres.) More carefully speaking, I believe the constraints at the minute are something like \Omega = 1.02 +- 0.03 (at one sigma, or aroudn 67% confidence). Meaning that while it is possible the universe is open or closed our best evidence at the minute is that it is entirely consistent with flat, and that this consistency linked with Occam's razor suggests that we may as well take it as flat.

Meaning that the universe is probably infinite.

These considerations do not take into account the universe's topology, of course. The universe can be flat but finite if it is, for instance, on a torus. It could also be on any number of absurdly-shaped topological structures. This is because cosmology is based on general relativity which is, by definition, a local theory. Topology is, by definition, a global theory, and unless the characteristic length-scale of the topology of the universe happens to be within the characteristic length scale of the universe itself (ie if the "radius" of the torus is roughly of the order of the horizon), we're not realistically going to tell the difference between an infinite, flat universe and a flat, toroidal universe.

Occam's razor can again come into play here and suggest that the universe is, as a result, flat but we should probably begin wondering whether that razor's getting a bit blunt.

Re:Let's do the math

[kilfarsnar]

lol. "Interesting".

Slashdot was never mighty but, God, how low it's fallen.

Yeah, wondering at what might be possible. Pssh! Who needs that? This is a serious site, after all!

Re:Let's do the math

[boristhespider]

Both statements are so arguable as to be nearly meaningless.

Re:Let's do the math

[MightyMartian]

Only by those who have no fucking idea what they're talking about.

Re:Let's do the math

[cat_jesus]

There's no real evidence to support a finite amount of mass.

Re:Let's do the math

[vivian]

for values of infinity that approach 420.

Re:Let's do the math

[Saysys]

Ummm I think you've confused ridiculously large number with infinity. They are not the same thing.

Clearly you do not understand how calculus works.

Re:Let's do the math

[mark-t]

Experimental evidence suggests that the universe had a beginning. and that based on observation, this appears to have been about 13.8 billion years ago.

13.8 billion years ago is not an infinite amount of time. The universe is not infinite.

Re:Let's do the math

[nine-times]

We don't know what will be possible in the next 1000 years, but it's entirely possible that out inability to travel faster than light is not a technological problem. That is, as our knowledge of physics becomes deeper, we might only confirm that FTL travel is simply impossible, no matter what technology we bring to bear. It's impossible for us to say with certainty, at least at this point in our development, but there is no reason to think that we can actually develop technology for FTL travel, time travel, teleportation, or a lot of other scifi technologies.

Now you might bring up flight, as many people do. "200 years ago, you would have said that there's no reason to think that we would develop the technology for manned flight, but we have!" True, but at least there was a precedent. We knew that flight was possible, because we'd seen birds do it. Even in traveling through space, there has been a precedent in that we've known for a while that meteors fell from "the heavens" for quite a while, and people may have suspected that it was the case even before that, so we knew that material could traverse the sky. And anyway, there didn't seem to be physical laws that prevented it, other than that we're heavy, and there didn't seem to be any way to get up there. There was the potential to build a staircase as high as your architecture skills would allow.

But FTL travel? All indications at this point are that it's simply impossible. If we were to posit that mankind will someday achieve inter-galactic travel, I would guess that it would be by developing suspended-animation and AI capable of piloting a ship over that kind of time frame. The logistics of planning that kind of trip are pretty unimaginable, but I still suspect it's more realistic than FTL travel.

Re:Let's do the math

[thedonger]

Hoverboards, goddammit.

Re:Let's do the math

[vivian]

How about inventing a planetary wide gamma ray shield instead?
Surely in a gamma ray prone galaxy there would have to be at least a few systems that had an atmosphere or oceans that would shield from gamma rays? In as little as 100 to 200 years I think we would easily have the technology to sustain a colony deep in the ocean, if it were necessary.

Re:Let's do the math

[physicsphairy]

Depends on who you're asking. I've known physicists to take expressions where infinity is mentioned and substitute 10 because it was "big enough." The frustrating part of course is that they got the right answer. . . .

Re:Let's do the math

[budgenator]

I don't know about your universe, in mine it's, I'm the center and it's H0/C in every direction!

Re:Let's do the math

[neorush]

http://www.hendohover.com/

Re:Let's do the math

[chmod a x mojo]

And if you read TFS they are only talking about life similar to ours; there is nothing saying that in other regions life hasn't evolved to be able to handle those kinds of environments.

This is exactly why it is impossible to predict the finding of "life" in non-earth environments, there are just too many variables that we don't even know to look for. I.E. life based on something other than carbon, life than can flourish in extremes we could never dream of surviving... be it temperature, pressure, or even radiation bombardment. And that is only a tiny fraction of differences, any one of which could be overlooked, and the probability is there would be multiples of these differences all at once.

Re:Let's do the math

[schlachter]

I get your sentiment, but your time line is orders of magnitude off....

In 1K years we will be almost exactly the same.
In 10K years we *might be slightly different but probably no one will notice.
In 100K years we may be a different species, but still easily recognizable as "human"
In 500K years we might be very different from our current form.

Re:Let's do the math

[xaotikdesigns]

That's one of the things I always wondered. We came from asingularity that held our entire "universe". This singularity exploded and created everything that we know and call the universe. The universe is supposed to be 150 Billion Light Years wide. What if 400 Billion Light Years away, another singularity exploded, and another universe is expanding out from it's Big Bang, and in a few billion years, our two universes will wind up colliding into each other?

What if our universe isn't expanding due to dark energy, but because there is another universe sized black hole providing a huge amount of gravity that is pulling things towards it? What if there are billions of these, with billions of Big Bangs, pulling galaxies and matter from each other into themselves, and possibly collapsing back into these giant singularities in a cycle that takes trillions of billions of years?

Re:Let's do the math

[turbidostato]

"All indications at this point are that it's simply impossible. If we were to posit that mankind will someday achieve inter-galactic travel, I would guess that it would be by developing suspended-animation and AI capable of piloting a ship over that kind of time frame. The logistics of planning that kind of trip are pretty unimaginable"

Perusing you own argument, I'd say it is not pretty unimaginable but, on the contrary, quite easy to imagine: we've been flying around in a Noah-ark type of spaceship for as long as we know.

What I find troublesome is not the logistics but the intent. A 'Songs of Distant Earth'-style endevour is purposeless by any practical meaning once you start thinking about it minimally seriously, so I don't see it happen unless there's a chance for the people sent into deep space to communicate and interact among them, which without FTL devices seems pretty doubtful.

Re:Let's do the math

[Fwipp]

haha, blaze it

Re:Let's do the math

[Grog6]

If we create those Machine Descendants Incorrectly, we Automatically make them our Descendants. :)

Remember, Weight that SkyNet() Function really high, to minimize this outcome in Your Code!

Re:Let's do the math

[MMC Monster]

Maybe not FTL, but what about worm holes or other forms that can cause information to travel without going between two points.

Quantum teleportation and subsequent "real" teleportation. Transporters that use entangled particles to create a new body for us at the destination. Rips in the universe.

All science fiction, true. But can we say with 100% certainty that none of them will ever be possible?

Re:Let's do the math

[OS2toMAC]

Personally, I follow the theories if Zager and Evans. http://www.metrolyrics.com/in-...

Re:Let's do the math

[Artifakt]

Even though he's probably right, it's unimportant - let's assume you're right, there really is some way to move at at least a high fraction of c, and even that it can open the stars themselves to humans. - WE certainly won't be looking for life in other galaxies before we have even looked around our own. We won't be looking for life closer to our own galactic core before we have looked at the immediate neighborhood in our own spiral arm. We won't even be looking as close as Tau Ceti until after we have checked our own solar system in such places as Titan and Europa, if we even get that far. Most probably, we won't be looking at Europa at all until we have proven the technology to tell absolutely and for sure if Mars has life. This whole discussion is like a young person speculating about what they would do after they have more money than Warren Buffett, before they have actually made their first million. The time to start speculating is after you've made a few hundred million or even a full billion or so.

Re:Let's do the math

[minstrelmike]

There appears to be an infinity of possible things that could happen evolutionarily.
But if you look merely at the number of stars in the entire universe, approximately 300 billion billion, that's essentially 10 to the 20th power. That means in order for life to be unique in the universe, all we need are 20 one out of ten possibilities in a row.

Re:Let's do the math

[giorgist]

Standard argument from ignorance ... "hey look you don't know what you don't know so we might invent long enough ladders to be able to climb to the next galaxy". Well in fact you are wrong, we are fast advancing to knowing a fair bit or what can be known. I know it may sound familiar. What is well know is the cost of pushing the boundary of knowledge is growing fairly consistently. So in a century we will need half the worlds resources to learn 1% more where as now we need 10% of the worlds knowledge and a century ago we needed .1% of the worlds knowledge. Ultimately it might not be possible to cross into another galaxy much like it might not be possible to travel back in time to make two planets occupy the same spot with no ill effect ... but you don't know, there are still people working in garages.

Re:Let's do the math

[Applehu Akbar]

A thousand years? We may even have a stable, well-liked version of Windows by then.

Re:Let's do the math

[mark-t]

What evidence is there of an infinite universe that had no beginning?

Bear in mind also that if an infinite universe exists, which had no beginning, then light would also have had infinite amount of time to travel to here from absolutely everywhere else, and although the intensity of radiation that reaches a point is inversely proportional to the square of the distance to that point. the volume of space that is an average of some given distance away from a point is greater than an amount proportional to the square of the distance from that point, and so the number of things in that volume which produce radiation at that distance would be be correspondingly greater, more than cancelling out the inverse square relationship to the intensity of radiation reaching a point some fixed distance apart. Every point in the universe would be perpetually saturated in radiation that is reaching it from every other point in the universe, infinitely far away, and certainly things like life bearing planets could not exist.

Critical observation suggests that the universe is finite.

Re:Let's do the math

[Sardaukar86]

Only by those who have no fucking idea what they're talking about.

I'm confused, your response to boristhespider seems a bit harsh as his posts are usually very high quality, in particular his comprehension of advanced astrophysics (from my layman POV). Am I missing something here?

Re:Let's do the math

[quenda]

physics. Our progression in the last 100 years is more than 1000 fold all previous years combined

You think!? In 1914 we already had quantum mechanics and relativity (which limited speed to 'c' ).
Since then ... a bit of refinement. General relativity was published in 1916, but I would not call that a thousand-fold increment.
Now the greatest minds of our generation bang their heads against the brick wall of string theory.

Re:Let's do the math

[DavenH]

Galaxy hopping is not as improbable as you would think. It's a matter of developing better propulsion systems, something I'm sure we'll do. You might have heard it said that at 1g constant acceleration, you could reach Andromeda in under 40 years, ship-time. Man would need to master antimatter and suspended animation, but even today that doesn't seem like magic.

Re:Let's do the math

[dnavid]

What evidence is there of an infinite universe that had no beginning?

Bear in mind also that if an infinite universe exists, which had no beginning, then light would also have had infinite amount of time to travel to here from absolutely everywhere else, and although the intensity of radiation that reaches a point is inversely proportional to the square of the distance to that point. the volume of space that is an average of some given distance away from a point is greater than an amount proportional to the square of the distance from that point, and so the number of things in that volume which produce radiation at that distance would be be correspondingly greater, more than cancelling out the inverse square relationship to the intensity of radiation reaching a point some fixed distance apart. Every point in the universe would be perpetually saturated in radiation that is reaching it from every other point in the universe, infinitely far away, and certainly things like life bearing planets could not exist.

Critical observation suggests that the universe is finite.

This is known as Olber's paradox, and it is not valid for expanding universes where red shift reduces the wavelength of light from distant sources until it drops below visible wavelengths and there ends up being an observable horizon, even in an otherwise infinite space and unbounded lifetime.

Although your point about distance and volume is wrong for other mathematical reasons. The number of light sources expands as the square of radius, not volume. The *total* number of sources is proportional to the cube of radius, but that's double counting. The volume includes close sources previously counted, plus the new sources being added as radius increases. Olber's paradox doesn't rely on that error in math.

Re:Let's do the math

[Tablizer]

The laws of probability suggest humanity is doomed, at least in our current form. We as human ponderers are roughly a sampling of the average human pondering their existence. About 60 billion humans have come before us, which suggests roughly just 60 billion will come after us since we are most likely to be in the middle of the pack rather than near the beginning or the end of the pack. (Roughly the Copernican principle as applied to human population density and time.)

If most of our future is to be Borg-like, then we'd more likely be Borgs contemplating our existence, not humans. But us (here now) being at such a coincidental position would be violating the Copernican principle. Either way, we are either doomed to end soon or become Borg-like, neither is a pleasant thought.

Of course coincidences do happen and we may indeed coincidentally be at the start of the human expansion curve; but if I were in Vegas, I wouldn't bet on it. We're doomed, guys.

Re:Let's do the math

[RabidReindeer]

I dunno. Are gamma rays the ones that they try and capture down at the bottoms of mine shafts?

Re:Let's do the math

[Brenda-B]

What evidence is there of an infinite universe that had no beginning?

Bear in mind also that if an infinite universe exists, which had no beginning, then light would also have had infinite amount of time to travel to here from absolutely everywhere else, and although the intensity of radiation that reaches a point is inversely proportional to the square of the distance to that point. the volume of space that is an average of some given distance away from a point is greater than an amount proportional to the square of the distance from that point, and so the number of things in that volume which produce radiation at that distance would be be correspondingly greater, more than cancelling out the inverse square relationship to the intensity of radiation reaching a point some fixed distance apart. Every point in the universe would be perpetually saturated in radiation that is reaching it from every other point in the universe, infinitely far away, and certainly things like life bearing planets could not exist.

Critical observation suggests that the universe is finite.

This is known as Olber's paradox, and it is not valid for expanding universes where red shift reduces the wavelength of light from distant sources until it drops below visible wavelengths and there ends up being an observable horizon, even in an otherwise infinite space and unbounded lifetime.

Although your point about distance and volume is wrong for other mathematical reasons. The number of light sources expands as the square of radius, not volume. The *total* number of sources is proportional to the cube of radius, but that's double counting. The volume includes close sources previously counted, plus the new sources being added as radius increases. Olber's paradox doesn't rely on that error in math.

Agreed. In the end - even if they are off by a factor of ten - it still gets us plenty of life in a finite universe. There may be infinite space but we have a start and finite velocities so we don't have an infinite universe as that volume is finite.

Re:Let's do the math

[Algan]

No, those are neutrinos. Gammas would never reach Earth's surface, they would just destroy the ozone layer, allowing Sun's UVs to sterilize the planet.

Re:Let's do the math

[Anonymous Coward]

As GP said, FTL is different.

Yes, people said that breaking the sound barrier was "impossible," but what they really meant was that it was infeasible. We knew it was possible because we saw meteors break the sound barrier. Even man-made objects such as bullets could break the sound barrier. So the debate wasn't about whether it was physically possible to break the sound barrier; it was about whether a plane that was sturdy enough to resist the shock waves would be light enough to fly. This is an engineering problem -- an issue of feasibility -- and such problems get easier to solve as technology advances.

But again, FTL is different. We have never once observed an object travel faster than the speed of light. Not a star, not an asteroid, not even a photon. Physical equations (equations which have been verified empirically time and time again) tell us that FTL is impossible. Yes, it is possible that these equations are incorrect or incomplete, but at the moment there is little reason to doubt them and thousands of reasons to believe them, and no amount of new technology is going to change the math and the science.

Re:Let's do the math

[fafalone]

Yes because we know everything now and anything that hasn't been discovered or disagrees with our current understanding simply will not ever exist. We haven't even had electricity for half a millennium... who are we to presume that our understanding and ability is absolute and won't change in the next 10,000 years or 100,000 years. Of course we wouldn't ever see it barring something extraordinary, but to say our primitive baby civilization has all the answers.. how sad it must be to think like that.

Re:Let's do the math

[rubycodez]

being able to travel at near light speeds would allow humans to go anywhere without limit. time dilation brings any galaxy close

Re:Let's do the math

[davester666]

Considering that they are actively hiding from us, yes, our chances of finding them are very small.

Re:Let's do the math

[mark-t]

For what it's worth, Olber's paradox uses the wrong formula for the volume of a shell some distance R from earth... The formul as I remember it from Olber's paradox is 4*Pi*R^2*dr, where dr is the thickness of the shell. However, this value only approaches accuracy as R approaches infinity. It is wrong for all finite values of R.

And I was not double counting anything. The actual volume of such a shell is: 4/3*Pi*(r+dr)^3-4/3*Pi*r^3. This is a value that is admittedly less than proportional to R^3, but more than proportional to R^2 for any finite value of R greater than zero. This volume is actually even greater than the value that Olber was utilizing, and dividing it by R^2 to calculate the expected intensity of radiation in that entire shell that reaches a point at distance R does not approach 0 as the distance approaches infinity.

But the real problem with Olber's paradox is not the miscalculation of the volume of the shell at some distance from earth,and in turn the number of elements within that volume which will emit radiation,but rather with the assumption that the universe is somehow actually infinite in the first place.

Olber's paradox revealed that trying to make an assumption that the universe might be infinite is flawed, and by my understanding helped to serve as an impetus at the term to find alternative explanations for what we observed, eventually leading to the widely accepted big bang hypothesis.

And observed red shift means that objects are moving away from each other, which means that at some point they were much closer together, and rewinding the clock even further suggests that the universe began at a single point, and has been expanding outward ever since (although you can no more find a point in space that is the center of it than you can find the center of an inflated balloon anywhere on the surface of the balloon).

Bottom line: the universe is finite. Even if it were ever found to be expanding into an infinite unbounded space.

Re:Let's do the math

[Your.Master]

Yes, he can. The only sense in which we can travel 28000 light years away in 1000 years requires that we invent time travel, at which point the phrase "in 1000 years" no longer makes sense.

It's a well-known result: FTL travel implies time travel.

Re:Let's do the math

[AchilleTalon]

I believe you are having a limited knowledge of the physics and how discoveries work.

First of all, the physics in the next 1000 years will not be that much different from the physics known today. The Newtonian mechanics is still a pretty good approximation of the macroscopic world and nobody declared it is over and replaced by quantum mechanics all the way. In the next thousand years and beyond, the physics will have to take into account for everything we already discovered so far.

Second, each discovery has an energy cost. That cost has increased at a tremendous rate since Einstein wrote his paper on special relativity. The LHC is consuming very large amounts of energy to keep working. The computers required to analyze the data are consuming very large amounts of energy. There is a limit on the amount of energy we can consume overall and we can dedicate to research. This is a limiting factor that will slow down the pace at which new discoveries are possible. There is a trade-off to maintain between research and sustain life here. We cannot dedicate all the resources to research because we will eventually deplet the pool of genius needed to perform this research. So, we need to sustain life at a scale sufficiently large to keep genetically and intellectually gifted people coming.

Third, in case you haven't notice, it is now more than a century we haven't discovered something that revolutionized the physics like relativity and quantum mechanics. Scientists these days are working on decimals and number of significant digits trying to discriminate between two equally valuable models.

Re:Let's do the math

[AchilleTalon]

Quantum teleportation is not matter teleportation at all. You have to transport the entangled particle with all the limiting factors (speed of light) to destination before performing the second part of the experiment. It is abusive to use quantum teleportation as a gateway to state the "real" teleportation may exists. This is purely speculative and totally unrelated.

Re:Let's do the math

[nine-times]

Maybe not FTL, but what about worm holes...

Using a worm hole to travel between two points faster than light can pass between those points would be an example of faster-than-light travel. There's speculation that we possibly might someday figure out how to do it, but it's still at the point of being "really wild speculation that we have no real reason to think is possible."

Re:Let's do the math

[wierd_w]

Why is time dialation so frigging hard for people to comprehend?

Here's the thing kids-- TIME IS NOT A CONSTANT. It is tied inexorably with accelleration. Want to get to another star system in YOUR lifetime? Just travel some significant fraction of C! Time FOR YOU will slow down, while the rest of the universe will be unaffected. This is proven science-- You just need to measure the muon count at earth's surface to prove it is so.

Now, you CAN state that doing that is going to be very energy prohibitive, and thus very costly. What you CANT say is that this is not possible.

Seriously, the argument of the parent is trotted out every time a topic like this comes up, and every single time it gets bitch slapped for the erroneous crapfest that it is. Time is NOT constant. It is different everywhere in the universe, and hell-- is not even consistent on the surface of the damned earth!

A person shot at a distant star system with enough energy will arrive within THEIR lifetime-- but everyone they ever knew or loved on earth will die of old age long before they get there. Of course, people moving to another star system probably wont be too particular about that, since they are going on a one-way trip.

Do try to keep up. Relativity and time dialation have been around for the better part of a century now. How you feel about it has no bearing whatsoever on it being true. Experiment after experiment has shown that it is. The GP is correct-- AC *CANT* say that, and neither can you.

Re:Let's do the math

[wierd_w]

You dont NEED FTL to be an interstellar species. You just cant be an interstellar society. Time dialation traveling at sublight speeds at a significant fraction of C is more than sufficient to colonize the entire galaxy.

Re:Let's do the math

[Smauler]

But again, FTL is different. We have never once observed an object travel faster than the speed of light.

We have, in some ways. Light was slowed to 17 metres per second in 1998, and below 10 metres per second in 2004. People can run that fast.

I know, the speed of light in a vacuum is what was being referenced.

Re:Let's do the math

[Ryanrule]

why wouldnt the machines keep some humans around?
you could play real life god games. sounds fun.

Re:Let's do the math

[wierd_w]

This is untrue. "Empty Vacuum" has mass. (or rather, energy)

The vacuum is expanding at an alarming rate. The universe's total energy (Over all time) must therefor be infinite.

Dark energy does not go away from hand waving.

Re:Let's do the math

[Smauler]

Third, in case you haven't notice, it is now more than a century we haven't discovered something that revolutionized the physics like relativity and quantum mechanics.

To be fair, quantum field theory was more recent. Also, relativity and quantum mechanics did _not_ revolutionise physics when they were first posited. They revolutionised physics when they became more accepted within the field. There could be a crucial major discovery that somebody made in 1995 that we'll only actually really notice and be able to prove in five years time. A year later, we'll be saying that there hasn't been a significant discovery in physics in the last quarter of a century.

Re:Let's do the math

[holmstar]

You presume that we won't actively modify ourselves.

Re:Let's do the math

[nine-times]

No, you don't need FTL to be an interstellar species, but it seems like you would need it to reach another galaxy in the next 1000 years.

Actually, I'm not 100% sure that's what the guy I was responding to was saying, but he was certainly saying that our understanding of physics would have improved to the point of allowing FTL travel.

Re:Let's do the math

[LongearedBat]

10% of infinity is...... hmmm, carry the one... Um 7?

42

Re: Let's do the math

[Anonymous Coward]

So people have thought for thousands of years. "The end is nigh!" is an ever popular refrain in civilization.
But humans are resilient and resourceful as hell. Only a global cataclysm could remove us all by now. And once we get off this rock, not even that is a sure thing.

Re: Let's do the math

[jovius]

So called Big Bang happened everywhere. The observable universe is finite, the universe infinite.

Re:Let's do the math

[Artifakt]

Now you're out of SF and just spewing outright fantasy! ;-)

Re:Let's do the math

[boristhespider]

Dude, I'm a cosmologist, and a general relativist. I'm very well aware of how the universe can be spatially infinite, and have a finite age. Making pithy (and erroneous) statements such as "13.8 billion years ago is not an infinite amount of time. The universe is not infinite" does not change this.

Re:Let's do the math

[Tom]

Why so focussed on human life? By the time a ship entered another galaxy, we wouldn't be humans anymore anyway. It's called evolution. What you and me consider human would be somewhere in the biology text books under "primitive ancestors of our race".

Re:Let's do the math

[boristhespider]

Yeah well I'm not going to go into a protracted lecture on parameter estimation here. The point is that the data is consistent with the universe being flat, and the theoretical bias is towards the universe being flat rather than a tiny bit away from it. These taken together explain why so many cosmologists - myself included - simplify the calculations by making the universe exactly flat. Sure, we might be wrong in doing so, because the theoretical bias is just that, but in most contexts the error is genuinely tiny given just how flat it seems to be.

Re:Let's do the math

[boristhespider]

Fancy adding a bit of weight to the random abuse? I don't know where Kjella got the idea that as far as we know there's a finite amount of energy around, for one thing. While there may be a finite amount within our horizon, that's a very different thing, since all we need to do is move a few megaparsecs and we've got a slightly different horizon. The statement that there is a finite number of galaxies within our horizon is completely uncontroversial (and indeed obvious, not least since our horizon extends back before the formation of galaxies at all...), while the statement that there is a finite number of galaxies *outside* our horizon is unsubstantiated and unlikely to be substantiated from that starting point.

On the other hand, gameboyhippo's statement that space is not infinite because it is expanding is also very much arguable. In this case we're on firmer ground, since we can look at the models actually employed in cosmology. If we restrict ourselves to the (Friedman-Lemaitre-)Robertson-Walker models, which are far and away the most widely used, then we've got three of them. One of them is formed of a three-dimensional spherical surface (so not a sphere you'd recognise, but the same in 4d), which is evolving. This is a "closed" universe, and in this model, indeed, space is not infinite but is expanding. But there are two other models. One of them, the universe is composed of a foliation of saddle-shapes (in 4d). This is an "open" universe, and here space is infinite and expanding. Or the universe can be composed of flat sheets. This is (unsurprisingly enough) the "flat" universe, and is *also* infinite and expanding.

It can certainly be argued that the data currently prefers a closed universe, but it does so at a statistically meaningless level (it covers both other cases, well within one standard deviation); the data cannot currently tell us anything. At this point theoretical bias comes in and we have to ask ourselves if there's any good reason that the universe would be almost, but not exactly, flat? The answer is sure, we can come up with reasons, but justifying the actual numbers involved is a posterior exercise. Instead, the preference is for the simpler model, flatness, until the data improves.

Do you see why I might have stated that both statements are so arguable that they're close to meaningless? I could have phrased it better, and I apologise for sounding brusque, but I stand by it.

Re:Let's do the math

[Hognoxious]

XP classic - millenium edition.

Re:Let's do the math

[Carewolf]

No, it's definitely false. Current data strong favours a universe that is flat (ie infinite), while it only narrowly supports a universe that is open (ie infinite and shaped like a foliation of saddles), and only slightly better favours a universe that is closed (ie finite and shaped like a foliation of spheres.)

You are talking about the potential size of the universe, a flat universe would continue to expand into infinitity, but like any number on the line of numbers going to infinite, and the current universe is finite.

Re:Let's do the math

[gl4ss]

why? are the genes degenerating or something?

Re:Let's do the math

[tofarr]

Technology is the evolution of evolution - OP may be more correct than you realize

Re:Let's do the math

[meta-monkey]

The problem with that is all evidence points to space (and time) itself beginning at the Big Bang, and expanding from there out. So there was no such thing as "400 billion light years away" at the time of the Big Bang. Space didn't exist.

Re:Let's do the math

[mark-t]

Even if the universe were expanding into some hypothesized infinite space, the fact remains that it has only been doing so for a finite amount of time, and so therefore is not infinite in size.

Re:Let's do the math

[gameboyhippo]

For the record, I agree that "MightyMartian" was a bit harsh, and I did enjoy reading your rebuttal. But with that said, I have a question. My understanding of the "big bang" is that the singularity began to exist and was all of space. And that it began to expand and continues to expand today. And that the expansion has not reached the point where we can no longer observe the beginning of space/time. Is this inaccurate?

Re:Let's do the math

[tommeke100]

The closest spiral galaxy to us is Andromeda, 2.2 million light years away.
Andromeda is approaching our galaxy at a rate of 670,000 miles per hour.
Five billion years from now it will probably collide with us.
So, we'll just have to be patient if we want to hop onto another galaxy :-)

Re:Let's do the math

[Ravaldy]

Who said you had to get there quickly?

I see 1000 obstacles preventing us from travelling outside our solar system but that doesn't mean it's impossible to eventually overcome all 1000 of these obstacles.

Re:Let's do the math

[boristhespider]

Ah, but here you're falling into one of the common misconceptions about cosmology. The universe isn't expanding *into* anything -- if it were, the universe would have a centre. While observationally we (obviously) can't prove that the universe doesn't have a centre, it's a fundamental principle that if it did we almost certainly aren't in there. This is dubbed the Copernican principle and is one of the key tenets of cosmology. You can build cosmological models that violate the Copernican principle but they all leave you feeling a bit soiled - and even then you end up with cosmologies that typically (but not always) are composed of spatial surfaces of infinite extent.

The key to this is that if we're going to build a model of cosmology we have to employ a theory of gravity. The only serious theories we have are all "metric-based", in that they treat gravity as a geometry theory. (There are very firm reasons for doing so, including the observation that gravity is almost certainly a fictional force, given that it imparts the same acceleration to all objects regardless of mass. To do so implies that either the gravitational and inertial masses must be identical (down to changes of units) or else that the force is fictional, and on the same basis as the likes of centrifugal and Coriolis forces -- very real in the reference frame they're measured in, and zero in a different frame.) In any metric-based theory, if you impose that the universe is isotropic, as it is to a high degree if one observes the microwave background, and then additionally impose that the Earth is not at the exact centre, you're lead basically to Robertson-Walker models. In these models, the universe is composed of a "foliation" of sheets; basically, a lot of three-dimensional surfaces stacked one on the other and filling the whole of the 4-d spacetime. Two of the three RW models are composed of *infinitely extended* spatial slices. Only one of them is composed of finite surfaces. Observation can't tell between them, but there is no more reason to assume we live in a finite universe than an infinite -- and indeed there's a mild hint towards the opposite, in that something so close to flat is most likely flat (and if it isn't could well be open - both are infinitely extended). It's true that this is a theoretical bias, but when observation fails we don't have much to fall back on, and observation leaves the distinct probability that the universe is spatially extended to infinity.

It's all a bit academic, of course, since we can never observe, let alone travel to, that infinite extent - we can only see back within our own light cone and that *is* of finite volume, both spatially and hyperspatially.

Re:Let's do the math

[boristhespider]

No, I'm talking about the spatial extent of the universe. I'm not sure how you're defining "universe" but it doesn't appear to coincide with the definitions used by cosmologists.

I'm also talking from a position that can be backed up by a large amount of both theory and data. The data cannot show that the universe is infinitely extended, but it very definitely does not say that it *isn't* infinitely extended, and the theory actually favours infinitely extended over finite. You're free to disagree but frankly if you can't disagree backed up by a theoretical model that fits both the background cosmological evolution and, more importantly, both the perturbations on the CMB, the shape of hte matter power spectrum, the *oscillations* on the matter power spectrum, *and* the dimming of distant Type 1a supernovae, then you're on a hiding to nothing. You have to fit this data.

I don't like Lambda CDM. Very few people who've examined the fundamentals of cosmology do. It's wrong. It has to be wrong. It's wrong on principle, and it can be proven to be wrong extremely quickly, to those who have been trained. It goes like this: cosmology is a theory built on averages, but those averages are implicit. No-one has a clear idea of how to take an average in general relativity (or any geometric theory of gravity) and end up with another covariant theory. The averages we do have rely on spacetime being globally hyperbolic. This means that there are no geodesic crossings, and this condition is necessary because every current way of averaging tensor fields, including Zalaletdinov's, little though he'd want to admit it, involves taking your tensor field, casting it along null geodesics to the centre of your averaging domain, taking the average, and then casting it back out again. If we have geodesic crossings, then that process is not one-to-one -- the average is ambiguous and is therefore not covariant. Since cosmology is (implicitly, and ham-fistedly) based on averaging a locally-covariant theory, phrased as a globally-covariant theory, cosmology is dead in the water.

The problem is that Lambda CDM works extraordinarily well. Anything that replaces it *has* to fit all the data that Lambda CDM does, at least as well as Lambda CDM, and with fewer of its problems. And that doesn't exist. There is nothing on the horizon that can do that, and I don't see much hope for something to come up. Cosmologists who do examine the fundamentals are aware of this and are trying to find exactly why LCDM emerges as such an astonishingly successful phenomenology - it may well be a thermodynamic theory, in many ways - while everyone else just gets on with it, knowing that it works. Because it does, amazingly well.

And Robertson-Walker cosmology, and the Lambda CDM cosmology that is based on it, do not agree with the strength of your statement. The current universe may be finite. True. Our past light cone is finite. True. Our future lightcone is finite. Probably not true. The universe has a finite spatial extent. No-one has the slightest clue.

Re:Let's do the math

[boristhespider]

On a practical level, yes it is -- the microwave background stands in our way. As the universe expands it cools down (same as if you pump up a tyre both the pump and the tyre get hot, but in reverse) -- which means that tracking it back, in the past it was seriously fucking hot. The universe is also, even at the present day, composed of more or less 75% hydrogen and 25% helium. The ground state of the lowest energy level of helium isn't really very high, while hydrogen's is high but not *that* high. And if you start working it out, it turns out that if you look back to when the universe was very roughly 300,000 years old, you suddenly find a universe that was at the temperature where every single photon was energetic enough to ionise hydrogen (let alone helium). That then immediately implies that any photon would propagate a short distance (and a very short distance - the universe was vastly smaller then than it is now) before it was absorbed by a hydrogen atom which then spat out its electron. That electron would propagate a short distance before it fell into a proton and emitted another photon, which would almost immediately slam into another hydrogen atom, and so on.

That means that the universe was totally opaque. Using light, and we have no other probe right now (though a direct observation of a gravitational wave background would ease this somewhat, as would a brutally unfeasible detection of a cosmic neutrino background), we therefore have a hard limit back at the CMB.

Even if the CMB somehow wasn't there, yes, looking back we run eventually and inevitably into the beginning of the universe. The distinction is born entirely of the theory we're couching cosmology in -- general relativity or, at least, a geometric theory of gravity very similar to general relativity. In these theories the universe is actually described as a whacking great four-dimensional blob which we've sliced for convenience into spatial surfaces along some time direction. (Those choices aren't arbitrary; there are conditions on what you can choose as a time coordinate, and on what you can choose as a spatial coordinate.) It's those spatial surfaces that seem likely to be infinite in extent.

However, since we're working in something like GR we also have the restriction that we can't see outside of our past light cone. Nothing can propagate faster than the speed of light, and in GR that is actually described by the type of paths that things can propagate along, with light propagating along "null" paths, normal matter along "timelike" paths and either nothing or "tachyons" propagating along "spacelike" paths. These paths, intrinsically, *cannot* overlap. A timelike path will never be a null path and cannot cross one to become a spacelike path. That would be geometrically nonsensical. Spacetime is then mapped out by these "null geodesics", and if you map them back into the past you get what's known as a light cone -- formed of all the light that could possibly have reached us. What we can possibly observe has to come from within, or on the boundaries of, that light cone.

Now, that light cone *is* finite, and if we extend it all the way back to the singularity then we'll obviously run into problems. At a singularity everything genuinely dies, and our theory doesn't even begin to work. Even geometry doesn't. All this tells us is that our dynamical theory is missing something (which many - including myself - believe is a quantum theory of gravity that smooths out that singularity, quite possibly by enforcing a maximum density within a minimum volume, or some similar process). If we decide we're not going to wilfully put a load of infinities in our denominators and instead cut out light cone shortly after this singularity -- let's say when the universe was less than a femtosecond old; I'm sure that's young enough to satisfy everyone -- then we can even calculate the 4-volume of that light cone. And it is finite.

I think this might be one of the causes of the confusion on this point.

I'd also like to apologise again if I cam across as a bit curt.

Re:Let's do the math

[boristhespider]

Thank you for this comment, by the way. I think adding it up I've probably spent quite a lot of time trying to do my best to explain and discuss cosmology on here, so it's nice to know it's appreciated.

Re:Let's do the math

[boristhespider]

So I guess the short answer is no it isn't, but yes it is, and there's a bit more to it than that. In my time on Earth, during which I've studied history and physics and worked professionally at cosmology for quite some years, I've learned that "there's a bit more to it than that" is a valid answer to practically anything anyone has ever said. There are always more depths at which one can examine something...

Re:Let's do the math

[Ravaldy]

We have looked the way we do for about 200 000 years. 1000 years is a drop in the bucket. Just saying!

Re:Let's do the math

[Ravaldy]

We have been this way for 200 000 years.

Re:Let's do the math

[Ravaldy]

I think we are past flying cars. Everybody knows it's about flying anything. Forget the car parts.

Re:Let's do the math

[Ravaldy]

I'm not wrong or right because nobody on this earth can prove me right or wrong. As an example, fact is that we still haven't concluded how gravity works. We have theories, constants and mathematical solutions around gravity but we don't understand it. As another example, it's only recently (in 2000) that the existence of neutrinos was confirmed. It took 70 years to get from theory to conclusion. Since then with new technology many more experiments surrounding neutrinos have been made and offered more insight on their behavior.

We just don't know what we don't know and you claiming to know is BS.

.

Re:Let's do the math

[Ravaldy]

Tangent!

Re:Let's do the math

[mark-t]

Ah, but here you're falling into one of the common misconceptions about cosmology. The universe isn't expanding *into* anything -- if it were, the universe would have a centre

First of all, I never suggested that the universe actually *was* expanding into anything... I only offered the notion that even if it *were*, the fact that it has only been doing so for a finite amount of time still makes the universe finite, even if the space it were expanding into were infinite.

Second of all, if it were expanding into an infinite space, there is no reason to conjecture that this space would be limited to three dimensions, so no "center" to our expanding universe can necessarily be found - any more than you could find the center of a soccer ball on the surface of the soccer ball. A center definitely exists, but it's not going to be found on the restricted topology of the soccer ball, and the center of the universe exists, but you can't find it at a point in space... it would therefore be most correct to say that the center of the universe is actually the instant in time of the big bang.

Re:Let's do the math

[Ravaldy]

It's relative to a field obviously. Since 1900:
Our ability to process data alone is probably 1 000 000 000 fold (I think I'm underestimating this one).
Our ability to communicate is at least 1 000 000 fold (Probably underestimating this one too)
Our ability to travel is at least 100 000 fold
Our life span is at least 1.5 fold

Question is here, how does one put a number on the progression of science?

Re:Let's do the math

[Ravaldy]

Third, in case you haven't notice, it is now more than a century we haven't discovered something that revolutionized the physics like relativity and quantum mechanics. Scientists these days are working on decimals and number of significant digits trying to discriminate between two equally valuable models.

Many theories in the last decade have been concluded and research extended. The one that comes to mind is neutrinos. Although we knew about them 74 years ago we didn't have the ability to prove it. I'm sure plenty of people felt it would never be proven and that it would require too much energy to prove but yet in year 2000 they did it. Do you think our ability to harness power isn't going to evolve as well? Our science is slow moving but this same science enables many inventions which eventually enables further research whether it be physics or biology.

Fact is that not as many life changing discoveries will be made but there will be more BIG FINDINGS such as the higgs boson. Will they take longer to be discovered but their value to science will big larger and larger.

Re:Let's do the math

[boristhespider]

OK, I think we've probably run into the same ambiguity that I mentioned in a different comment in this thread. There are basically two definitions that we might have of this "infinite" business. I'm working from the viewpoint of general relativity -- or some other metric-based theory of gravity -- since I'm wanting to be work with a theory capable of quantifying statements. Given this, I have (at least) two definitions of "infinite" here:

1) The model we are driven to employ, the Friedman-Lemaitre-Robertson-Walker model (or some mildly inhomogeneous or mildly anisotropic generalisation of this) says that the universe extends spatially to an extent that is infinite (in two of the three subcases) and is finite (in the other), and our data is only good enough to state that none of these is preferred over the other (but that given the level of non-flatness, the flat case is *theoretically* preferred, as a theoretical, non-observational, bias.)
2) The past light cone is finite-volumed, as it obviously is, pending some revolution in our understanding.

So far as I understand your point, you're stating that the past light cone is finite-volumed. If that's what you're saying, excellent, we're in agreement. The problem is you used the word "space", which I interpret to mean "space", and the spatial extent of the universe is basically untestable except by reference to the density of the universe; if it is at the critical density, then it is flat (and infinite), and if it is at less than the critical density then it is hyperboloidal (and infinite). If it is greater than the critical density, then it is spherical (and finite).

If we're not talking about spatial extent but instead talking about the 4-volume of the past light cone then we agree.

(I might also add that in GR the entire manifold is basically set -- the "future" of an event (mapped out by the future light cone), the "present" which are regions connected by spacelike geodesics, and then the "past" which is mapped out by the past light cone. From this point of view, which is one that GR forces us to (although it may very well be in contradiction of quantum mechanics), we can't tell if the universe is finite or not temporally. We do know that the past light-cone appears to be finite, but we cannot know what the future light-cone is since we do not have backwards-propagating photons to bring us information along them. The future light-cone could be finite, which would imply that the universe recollapses in the future. The likeliehood right now is that the future lightcone is infinite. That would mean that if we're going to generalise what we mean by "infinite" to four dimensions, we still end up with an infinite 4-volume. However, that's ultimately supposition and extrapolation.

(It can also be commented that actually we don't know that the past light cone itself is finite, since the theory cannot be used to propagate the light cone to, let alone beyond, the singularity. This doesn't actually mean that the universe formed at the singularity; it means that our theory cannot be used to propagate light that near to it - or anything else, for that matter. It may very well be that in a quantum theory of cosmology, there is no singularity, and that we have a bouncing universe. In that event, the past light cone is *not* finite and may very well, in fact, be infinite.

(This part of it though is academic in many ways too since as I commented in another post, we can't see back anything like to the singularity anyway. Our only probe is light, and the universe goes inconveniently opaque at the CMB, which is effectively a photo of the universe when it was a bouncing baby of 300,000 years or so. We simply cannot see beyond this, other than indirectly, unless we manage to observe the gravitational wave background or, even less plausibly, the neutrino background.)

Re:Let's do the math

[Carewolf]

I'm also talking from a position that can be backed up by a large amount of both theory and data. The data cannot show that the universe is infinitely extended, but it very definitely does not say that it *isn't* infinitely extended,

You are talking religion, I am talking science. The scientific universe, the universe we can observe and interact with is finite, anything beyond what can ever theorically be observed might be infinite, but it is also not scientific and pointless to discuss.

Re:Let's do the math

[Rakarra]

The amount of space that contains matter and energy is likely finite, but space itself is not. We do not, at the moment, have a way of outpacing the rate of expansion.

Re:Let's do the math

[Rakarra]

They didn't get the right answer, they got an answer with a very small variation of error.

Re:Let's do the math

[boristhespider]

....

OK, I think this part of this thread is done. If you ever fancy reading that post, and any others I've made on the topic, feel free, and you might see just how little I'm talking "religion", and what a self-important jackass you sound.

Re:Let's do the math

[RockDoctor]

This is exactly why it is impossible to predict the finding of "life" in non-earth environments

Pessimist!

I don't automatically assume that "hard" = "impossible".

We may not have many data points, and acquiring in situ measurements may be a long way off in the future (not less than decades, maybe not less than millennia). But that's still not "impossible". Just "harder than we can do at the moment".

Re:Let's do the math

[RockDoctor]

You must be new here.

Knowing what you're talking about is shockingly rude behaviour on Slashdot. Keep it up!

Re:Let's do the math

[gzuckier]

And if you read TFS they are only talking about life similar to ours; there is nothing saying that in other regions life hasn't evolved to be able to handle those kinds of environments.

This is exactly why it is impossible to predict the finding of "life" in non-earth environments, there are just too many variables that we don't even know to look for. I.E. life based on something other than carbon, life than can flourish in extremes we could never dream of surviving... be it temperature, pressure, or even radiation bombardment. And that is only a tiny fraction of differences, any one of which could be overlooked, and the probability is there would be multiples of these differences all at once.

Hard to define life; hard to define anything, when you only have one type of it. Something that can reverse entropy on a local spatial/temporal basis?

Re:Let's do the math

[gzuckier]

That's just your opinion built on limited knowledge of physics. Our progression in the last 100 years is more than 1000 fold all previous years combined so imagine what we can do in the next 1000 years.

Invent a rope that can be pushed?

Re:Let's do the math

[khallow]

So we've had the current high tech civilization for 200,000 years? There might be a reason why I think things are different now than they've been for the past 200,000 years.

Re:Let's do the math

[khallow]

In 1K years we will be almost exactly the same.

Unless we're either extinct through our own devices or so heavily modified that we are no longer biologically human.

Re:Let's do the math

[Ravaldy]

I was responding to:

Will there even be an organism recognizable as human in another 1000 years? There's more than one way for humanity to cease to exist.

Re:Let's do the math

[Bengie]

The average GRB converts about 166 Earth masses into pure energy and blasts it out as a laser beam in less than a second. Your best bet is just to keep your distance, not a "shield".

Re:Let's do the math

[mcswell]

I read an article based on this premise back around 1965 (give or take, it was before the Moon landings). The author modeled the maximum speed that people could travel, beginning perhaps 10,000 BC (running) and going up through Gagarin/ Glenn. By projecting that increasing rate of increase, he "proved" that man would break the speed of light in another 30 years or so.

In fact we reached a maximum of 7miles/sec ( 0.00004c) back in 1968, and have regressed since 1972.

It's sort of like Mark Twain remarks in Life on the Mississippi, extrapolating from how the Mississippi periodically cuts off bends, thereby shortening itself: "...in the Old Oolitic Silurian Period, just a million years ago next November, the Lower Mississippi River was upward of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-rod."

Re:Let's do the math

[mcswell]

No, they weren't thinking that. They knew bullets did it all the time. It was just that passing the sound barrier seemed a very hard thing for humans to do.

In contrast, we don't know of *anything* that goes FTL.

Re:Let's do the math

[mcswell]

Now that I've posted, I see that someone else had already said the same thing (#48454389, immediately below my post right now), and in greater detail.

Re:Let's do the math

[khallow]

Yes. My point though is that humanity is about to come up with all sorts of ways to radically change itself as well as incentive for doing so (namely, labor competition with sophisticated automation and strong AI).

Re:Let's do the math

[Truth_Quark]

We've got a galaxy passing through in about 4 billion years.

So if you're up to star hopping, it'll be a good opportunity to colonize a whole stack of systems getting flung in a whole stack of directions ... assuming we're not sterilized by Gamma Ray Bursts from Andromeda.

Re:Let's do the math

[Truth_Quark]

Apparently the collision has become more serious than when I was at school, and now it's not going to pass through, but whack together, merging the super-massive black holes into a doubly super-massive black hole.

So get your popcorn ready, it's going to be a show.

Re:Let's do the math

[khallow]

But not so radical that we won't be "recognizably" human.

[...]

Consider Google glass, and people with artificial limbs, hearing aids, etc. Stephen Hawking communicates trough a machine. Technically, we are already radically altering ourselves. Do we call those users not recognizably human? No, we call them glassholes ;p

Artificial limbs have been around for a long time, but the first using signals from nerves date from the mid 90s according to Wikipedia. Glancing at Wikipedia, Hawking's speech synthesizer was in use since around 1985. Google Glass entered the market this year. Technically, we are already radically altering ourselves over the past few decades.

Biologically, they may deserve a new scientific name (no longer homo sapiens), but they would still be considered human, and refer to themselves as humans in everyday conversations, while the rest of us may be the ones who get a new label in the variation of "old" humans.

Unless it doesn't happen that way, of course.

Actually, it was labor being too expensive that created the incentive for machines and automation and AI to be created in the first place. To compete with machines, labor doesn't need to augment themselves. They just need to lower their price.

Horse-drawn wagons and chariots created the need for roads, but they aren't on the roads now.

This is one of the great misconceptions many first worlders have. People only think about the cost, as opposed to getting value for their buck. For example, what good is going to a more expensive school when it lands you the same job as somebody with a degree from a less known but cheaper school, or no degree at all?

OTOH, if it's not that way, then your argument wouldn't hold.

To compete with machines, labor doesn't need to augment themselves. They just need to lower their price.

Many if not most people choose to work more than 40 hours of work a week. They could choose to work less and earn less. Just because someone could choose to be unaugmented, doesn't mean they will choose to do so due to the compromises involved.

Re:Let's do the math

[khallow]

That's why I said "may".

You don't say "may" till third paragraph.

Horse-drawn wagons and chariots are tools, not people.

Human bodies are tools as well.

If augments are invented in the free market capitalist way humanity has been doing since, like, forever, it's going to be costly at first. This means even if the writing is on the wall that it's in everybody's interest to get augmented, the shift will be gradual, which goes back to my point that people will still recognize each other as "human".

So what? So let's say it takes a century to get those costs down to the point where such augmentations are affordable for the average person. You still have 900 years left.

What is the practical and economical reason that humans abandon their old forms for a new non-human form? This implicitly assumes that this is a more economical solution than developing a tool to take on those non-human characteristics.

Because the new forms are better, practically and economically. The killer app here is health. If you have a body and mind that can last thousands of years, then that's a huge advantage over the current human body. And while the human body and mind aren't bad as tools, we probably can do a lot better than that in terms of pushing physical and mental limits, or in interfacing with our other tools.

Re:Let's do the math

[Ravaldy]

No matter what form we take, we will still call ourselves humans.

Practically alone...

[Anonymous Coward]

So there are only 10 billion galaxies out there that can support complex life like that on earth? We're practically alone!

Re:Practically alone...

[MrLogic17]

If you're stranded on a desert island, with no ability to reach another island- you are very much alone. Doesn't matter how many billions of other people there are out there, if you have no chance at reaching or talking to them.

If this math holds up, the next interstellar island is further away than we thought... and we are likely going to be a very lonely species.

Re:Practically alone...

[CrimsonAvenger]

If this math holds up, the next interstellar island is further away than we thought... and we are likely going to be a very lonely species.

This math says pretty much nothing about our neighborhood. Remember, one in ten can just as easily be 1, 1, 0, 0, 0, 0, 0, 0, 0, 0 as 1, 0, 0, 0, 0, 0, 0, 0, 0, 1.

Even more importantly, this say nothing about our galaxy's likelihood of having life (basically, 100% right now)....

Re:Practically alone...

[buchner.johannes]

Actually, it's only 17 million. A quick calculation gives me that the number of galaxies within 5 billion light-years is 170 million. Neglecting very small, dwarf galaxies, which are more numerous but have drastically fewer stars, I multiplied the stellar mass density by the comoving volume up to z=0.5.

Re:Practically alone...

[Firethorn]

This math says pretty much nothing about our neighborhood.

Yeah, this is the equivalent of using the presumed sterility of the moon to measure the number of people within 1 km of my house. ;)

Still, from what I've seen of the equations, odds are the median distance between tool-using civilizations is likely well over 100 ly. :(

Re:Practically alone...

[Pfhorrest]

In mathematics "almost" denotes an infinite set minus some finite subset, so if there are only 10 billion galaxies that can support life and the universe is infinite, then the universe is "almost lifeless": infinitely lifeless except some finite subset with potential life.

Re:Practically alone...

[Neil Boekend]

The next galaxy is insanely far away anyway. The next star is already insanely far away. This galaxy supports life, as is evident. This gives us ample alien races to talk to, if we ever manage to cross the massive distances involved even within our galaxy.

sooo....

[xaoslaad]

I didn't rtfa but if these explosions prevented life for billions of years, does this mean things are settling down? Over the many years will it be possible for life to develop in the other galaxies? Does this make us one of the elder races? If so I feel bad for the universe.

Re:sooo....

[i kan reed]

Well, eventually there won't be any fusion potential left in the universe, which isn't so grand for life's prospects either.

Re:sooo....

[Code Herder]

Bah, we have more than enough time to work out a fix for that one! Let's work on immortality for me and then maybe rising sea levels or something, we'll get to that one in a few million years.

Re:sooo....

[kruach aum]

We are only the initial stage of an elder race. Einstein didn't start off with general relativity, he started with addition and multiplication. Don't give up hope yet. The fact that the world is clogged with retards doesn't mean we can't aspire to become the Great Old Ones.

Re:sooo....

[Arancaytar]

In the time between these bursts, maybe a few species got lucky and made it almost to space colonization before getting scrubbed.

Maybe we're one of them.

Re:sooo....

[Sri Ramkrishna]

When will start putting together planets in the solar federation?

Re:sooo....

[pla]

"There is as yet insufficient data for a meaningful answer."

Re:sooo....

[jbolden]

Yes things are settling down. The universe was much more energetic 10b years ago and will be much less energetic 100b years hence.

Re:sooo....

[blackomegax]

90% of the human population gets off on shit like honey-booboo. We aren't going to space any time soon.

Re:sooo....

[sconeu]

Mod parent up, +1 Asimov.

Re:sooo....

[Pope Hagbard]

LET THERE BE LIGHT.

Re:sooo....

[jeff4747]

The stars that are close enough to Earth for a GRB to be dangerous can't produce a GRB. So it's not so much "in between bursts" as being in the right place.

Re:sooo....

[americanpossum]

Read Stephen Baxter's book "Manifold: Space." The entire book is about the Fermi Paradox and what existing civilizations are doing to stop these mass extinctions from taking place in their own galaxies.

Re:sooo....

[h4x0t]

I would've been a bit nicer about it, but yeah. Mod up.

That's Life...

[RevWaldo]

...as we know it, screams every sci-fi fan.

.

Re:That's Life...

[__aaclcg7560]

"I dunno what the hell's [out] there, but it's weird and pissed off, whatever it is." The Thing, 1982.

Re:That's Life...

[h4x0t]

Imagine the wicked stuff that's evolved to survive gamma ray bursts. Terrifying...

Relativistic Species

[Scottingham]

I always like to think that any suitably advanced civilization eventually develops space-drives that can reach appreciable percentages of the speed of light. The time dilation effects would make traversing the galaxy relatively(heh) reasonable. The only hitch is that relative to all other lifeforms not moving at a such a speed would blink in and out of existence in the time it would take them to burp. Our current sliver of space-time is sooo tiny if you think about it like this.

What if there was a whole...dare I say...confederation of relativistic societies? In order to join you have to catch up. Otherwise you'll be gone in a blink.

Re:Relativistic Species

[HeckRuler]

What if there was a whole...dare I say...confederation of relativistic societies?

The question would be where are they and where are they going?

You could probably achieve some meaningful dilation if you orbited a black hole or something. But other than that, presumably the society that can hop around the galaxy still wants to have something to go to. And those locations would experience just as much time as the rest of us. Not that we all experience the same amount. Whole sections of the universe travel at different speeds and times. Like, you know how galaxies are accelerating away from the origin? Yeah, some are moving faster than others. And consequently experience different time dilatation. Dunno what sort of ranges we're talking about. Even at 90% lightspeed, you're only looking at a 1:7 ratio. A 142,000 years as opposed to a million years is still a society-crushing amount of time.

I'm not sure why you'd want to have a space-faring society that was rushing as fast as they could towards the heat-death of the universe. I guess some people would want to wait and see if anything interesting happened.

Re:Relativistic Species

[Anonymous Coward]

Like, you know how galaxies are accelerating away from the origin? Yeah, some are moving faster than others. And consequently experience different time dilatation. Dunno what sort of ranges we're talking about. Even at 90% lightspeed, you're only looking at a 1:7 ratio. A 142,000 years as opposed to a million years is still a society-crushing amount of time.

Hang on, what? That's not how universe expansion works. The further a galaxy is from us, the faster it appears to be moving away from us. However, we are not the center of the universe. There is no origin: everything is expanding everywhere.

Re:Relativistic Species

[drinkypoo]

I always like to think that any suitably advanced civilization eventually develops space-drives that can reach appreciable percentages of the speed of light. The time dilation effects would make traversing the galaxy relatively(heh) reasonable. The only hitch is that relative to all other lifeforms not moving at a such a speed would blink in and out of existence in the time it would take them to burp.

That's why it isn't useful. You can't use it for anything interesting to anyone but you. So why would anyone do that? There's no real point to moving at near-relativistic speeds because your civilization will be gone by the time you get home from anywhere worth going. After poking around your own solar system, you really need to be able to travel faster than light to achieve anything meaningful by going anyplace. Sending out probes to other places might still be worth it, but if everyone you ever knew will be dead by the time you get home, what's the point?

Now, if you could move a whole planet through the universe at those speeds, that might be useful. You could move your whole civilization, and everything it needed to survive (assuming you're not dependent on a star.) And if you are still dependent on a star, obviously by choice at that point, I suppose you'll need to take your whole system.

So, what would a star moving at near-C look like to the rest of us?

Re:Relativistic Species

[lgw]

That's why it isn't useful. You can't use it for anything interesting to anyone but you

And if the only problem remaining to you in life is boredom?

So, what would a star moving at near-C look like to the rest of us?

Get it going fast enough and it would look somewhat like a gamma ray burst, to those directly ahead of it, and be invisible from most directions. But there's probably not enough energy in a star to get it up to that sort of speed, at least with any sort of "stellar engine" anyone has yet imagined.

Re:Relativistic Species

[drinkypoo]

And if the only problem remaining to you in life is boredom?

You probably just take a several-billion-year nap.

But there's probably not enough energy in a star to get it up to that sort of speed, at least with any sort of "stellar engine" anyone has yet imagined.

The energy will have to come from elsewhere, then.

Re:Relativistic Species

[rubycodez]

Since mas dilates your ship would have the mass of a black hole
 
    that's a meaningless statement, a black hole can have any mass.
 
    You misunderstand time dilation, nothing inside the ship slows down for the passengers, everything inside the ship is normal in duration. Starlight is faint, protection from blue-shifted light seeming to be gammas is only a matter of shielding.

Re:Relativistic Species

[rubycodez]

Your claim of not being useful is rejected. Maybe a species wants to get their "eggs out of one galactic basket". Maybe they like to explore and catalog. Maybe they have friends back home with their minds preserved in a machine, that really can wait for signals for millions of years. Maybe they have a religious command to go and to spray planets with "black goo" as in Prometheus.

Re:Relativistic Species

[lgw]

You probably just take a several-billion-year nap.

While napping may indeed be popular in the retired community, travel is as well. And it seems likely the two passtimes could be combined, after all.

The energy will have to come from elsewhere, then.

This is even less practical than a stellar engine - you can hop between galaxies in only a few subjective centuries at 1g acceleration. Even with antimatter fuel the rocket equation becomes problematic after a while, but at least the physics makes sense. Try to send power to something moving past you near c, however, and you're sure to hear "I canna change the laws of physics, Captain!"

Re:Relativistic Species

[drinkypoo]

Try to send power to something moving past you near c, however, and you're sure to hear "I canna change the laws of physics, Captain!"

Physics as we know them, sure. But it's problematic to even carry enough fuel to accelerate to near-C with physics as we know them.

Re:Relativistic Species

[HeckRuler]

The big bang didn't have an origin? Doesn't the universe have a discreet edge that's approx 15 billion years * speed of light away from the origin point? I'd consider the mid-point between those two edges to be the origin of the big-bang. I mean, I know the big bang happened in all of the universe, kinda per it's definition. But a second after the boom, you've got this roughly spherical ball of a universe going and that sphere has a center-point.

I was under the impression that the galaxies that are nearer to that rim are going faster than we are, and they'd experience less time. The rim itself going at the speed of light, and the stuff near the center of mass going... some sort of universal zero velocity that experiences the least amount of speed-based time dilation possible.

Well, not really

[argStyopa]

"Gamma ray bursts would wipe out any live more complex than microbes".... ...that is, unless life evolved to use radiation as an energy source.

In other words, a couple of astrophysicists speculate to a degree that's only slightly and unquantifiably less than sheer "wild ass guessing", news at 11.

Re:Well, not really

[kaiser423]

Considering that's kind of like saying that maybe life will evolve to live on the surface of our sun (this is actually slightly more likely than an organism evolving to utilize as power utilize an event that takes place once every thousands of millions of years and is every bit as hostile as the surface of our sun).

Aka, they're not really talking out their asses.

Re:Well, not really

[jandrese]

Or the life lives deep in oceans where it would be protected from the gamma ray bursts.

The problem with all of these "how much life is in the Universe" answers is that we're trying to extrapolate from a single datapoint (our Solar System). The unknowns outweigh the knowns by a significant margin. In other words, it's mostly a lot of wild ass guesses.

I blame the Inhibitors and their devices

[enjar]

If only there hadn't been a Dawn War.

Light takes a long time to get here

[Streetlight]

Most of the galaxies are likely to be so far away that the light - including gamma rays which are made up of high energy photons - has been in transit for billions of years. What's the situation now in those billions of gamma ray emitting galaxies we are now observing in the intervening years since the light was produced? They may have settled down making life possible.

Re:Light takes a long time to get here

[Streetlight]

In some sense it doesn't actually matter. If light traveled a billion years to get here, then any life that's happening "now" (for a sane definition of now) won't be observable by us for another billion years.

I suppose being able to observe the life is important for us but I assumed these guys concluded life was impossible in these galaxies. Just because we can't now or ever observe life there doesn't mean it isn't there.

First 5 billion

[ZombieBraintrust]

Things are even bleaker in other galaxies, the researchers report. Compared with the Milky Way, most galaxies are small and low in metallicity. As a result, 90% of them should have too many long gamma ray bursts to sustain life, they argue. What’s more, for about 5 billion years after the big bang, all galaxies were like that, so long gamma ray bursts would have made life impossible anywhere.

Wouldn't that also imply that for the first 5 billion years planets in general would be low in metal? So you would have very few planets without iron cores and similer density as Earth. There would be a different chemical mix in most of the universe.

Re:First 5 billion

[HeckRuler]

Well for the first few hundred million years there's zero metal. Anything* other than hydrogen and helium are only made during a sun exploding. And the quickest dying, hottest stars last hundreds of millions of years. In general, as time goes on, more suns explode making more and more exotic elements like... you know.... carbon and gold.

*HEY, I'm getting some of that wrong. Turns out elements up to boron could be made by cosmic rays. And gold can only be made in a super-nova. Huh.
This wikipedia page about the origins of the elements is really nifty.

Re:First 5 billion

[DavenH]

Well for the first few hundred million years there's zero metal. Anything* other than hydrogen and helium are only made during a sun exploding.

Correction: anything elements above Iron are only made during a supernova.

Re:First 5 billion

[BarbaraHudson]

Their first visual impressions of us will be from "I Love Lucy", "The Honeymooners", "Car 54", etc. They'll think we're crazy, and hopefully give is a wide berth (no intelligent life).

Previously thought...

[king neckbeard]

'Previously thought' has varied quite a bit over time. Since it has been thought to be 1, it's going to be quite difficult for it to be lower than it has ever been previously thought, and 1 in 10 galaxies is higher than most estimates. Skimming TFA, it seems to suggest the problem is that it can't support life if you are too close to a giant explosion in space, and that our universe isn't even in one of the 10% mentioned.

So, to recap, 90% of galaxies have big explosions that could wipe out life as we know it except for the parts of that galaxy that aren't too close to the explosions. So, what we can really gather is that most of most galaxies isn't hospitable to us.

Total Bull

[gurps_npc]

I always despise these reports. They come up with something that life identical to our own - on our world could not stand up against and then say "No life is possible anywhere else".

No.

If we didn't have a Van Allen belt, some bright scientist would say no life could survive on earth, because of the radiation.

Life as we know it evolved to deal with earth. It evolved to live with at atmosphere, with a van allen belt protecting it, with limited meteors strikes (because Jupiter protected us), with our sun, with tides, etc. etc. etc. etc.

Just because we can't deal with a series of Gamma Ray burst does not mean living creatures living under an ice ocean, feeding on volcanic energy can't survive it.

Basically, what's going on here is some one asked a Physicist a question about biology. You get an answer that makes about as much sense as if you ask Stephen Hawking if the tumor in your kidney is benign or malignant.

It's only 10%

[ArcadeMan]

It should be 100%, but the Anti-Spiral race keeps killing all other sentient races.

oh dear

[confused one]

Well then, it's a good thing we live in one of the safe ones. I'm going to take a nap, let me know when we can reach the next galaxy,

Um, can't life just evolve under water?

[Dr. Spork]

...the gamma rays would set off a chain of chemical reactions that would destroy the ozone layer in a planet's atmosphere. With that protective gas gone, deadly ultraviolet radiation from a planet’s sun would rain down for months or years

Yeah, because it's impossible that complex life could be protected by a different (better!) kind of UV shield like... water. From my understanding, it's not exactly rare in the universe.

Re:Um, can't life just evolve under water?

[Firethorn]

How likely is complex life to evolve under those circumstances? Besides, I got the idea that only microbes with their extremely high radiation resistance would survive even in the deep ocean, as enough would penetrate to kill even things like ocean vent crabs.

I am dubious

[mbone]

I am dubious that gamma ray bursts are invariably a sentence of doom. The actual mechanism is due to the destruction of the ozone layer due to nitrogen molecules formed in the upper atmosphere; these molecules would "eat" the ozone for maybe 4 - 5 years after a GRB event, but would not (in that sort of lifetime) go from one hemisphere to another. Questions I would have include

- How many civilizations might form on bodies with very thick atmospheres, far from their Suns? (Venus does not need a ozone layer to keep the UV out, and might be very habitable a few AU out.)
- How many planets might have very long rotation periods (years), so that the night hemisphere never is subjected to the daytime UV?
- Are there rotation axis directions and orbital precession constants for planets that would keep GRB radiation mostly in one hemisphere, leaving the other to develop?
- How many planets might have other special circumstances that protect their ozone (such as a lack of N2 in their atmosphere, or an ozone generating biology in their stratosphere, etc.)

I am sure that there are others, but even these I think show that, while GRB might be bad for habitability, they need not be fatal. Note, too, that if I was running a Kardashev Type III civilization, one of my action items would be to find any possible GRB progenitors and disarm them. So, in a KIII galaxy, GRB would likely no longer be a problem; maybe that would be a good way to determine the number of KIII galaxies in the universe.

Re:I am dubious

[buchner.johannes]

I can not answer about the deadliness of GRBs, but I think you will find those answers in Phil Plaits book "Death from the Skies!".

- How many civilizations might form on bodies with very thick atmospheres, far from their Suns? (Venus does not need a ozone layer to keep the UV out, and might be very habitable a few AU out.)

Yes, insulation is a good idea. But the planet will always radiate as a black body and loose energy, which has to be re-supplied by the suns radiation. The radiation drops with the square of the distance, so rather quickly. These considerations (make-up and size of planets) go into calculations for the habitable zone.

I can also imagine that a GRB comes with considerable photon pressure and might strip the entire atmosphere off a planet, or heat it to a point where it dissipates into space.

- How many planets might have very long rotation periods (years), so that the night hemisphere never is subjected to the daytime UV?

I think the rotation of planets around their own axis (spin) is not known outside the solar system. Generally, the spin is generated from formation of planets in the rotating protostellar disk, but interactions and changing orbits may modify the spin (Venus, Uranus).

- Are there rotation axis directions and orbital precession constants for planets that would keep GRB radiation mostly in one hemisphere, leaving the other to develop?

If you do not have the problem of heating and evaporation of the atmosphere I mentioned above, then yes, that is probably possible. For example if the GRB goes off from the direction of the spin axis ("below/above the solar system"). This may safe you from one GRB, but since GRBs come randomly from all directions it is not failsafe across many billion years.

- How many planets might have other special circumstances that protect their ozone (such as a lack of N2 in their atmosphere, or an ozone generating biology in their stratosphere, etc.)

Not sure. I think it is possible to come up with such scenarios as you stated, but it has to be shown that they are frequent occurrences to be relevant for changing the survival rate of complex life.

Re:I am dubious

[mbone]

The point is really that we don't nearly know enough to answer any of these questions. We can provide "best current thinking," but with only 1 actual sample (Earth) and no experience with GRBs, these are just guessitmates at best.

I can not answer about the deadliness of GRBs, but I think you will find those answers in Phil Plaits book "Death from the Skies!".

- How many civilizations might form on bodies with very thick atmospheres, far from their Suns? (Venus does not need a ozone layer to keep the UV out, and might be very habitable a few AU out.)

Yes, insulation is a good idea. But the planet will always radiate as a black body and loose energy, which has to be re-supplied by the suns radiation. The radiation drops with the square of the distance, so rather quickly. These considerations (make-up and size of planets) go into calculations for the habitable zone.

I can also imagine that a GRB comes with considerable photon pressure and might strip the entire atmosphere off a planet, or heat it to a point where it dissipates into space.

The threat model is ozone, not atmospheric stripping. With the hypothesized existence of Steppenwolf planets, I don't even think that the notion of a habitable zone is necessarily that useful, except as a guide as to where exobiologists should look first. The real question is, how many civilizations might arise on "Earth's" at 1 AU from their (G type) star, versus "warm Venus's" at, say, 2 AU. (Scale distances as necessary if you want to include other type stars, such as M dwarfs.) If this ratio is anywhere near unity, the "GRB==doom" hypothesis falls to the ground.

- How many planets might have very long rotation periods (years), so that the night hemisphere never is subjected to the daytime UV?

I think the rotation of planets around their own axis (spin) is not known outside the solar system. Generally, the spin is generated from formation of planets in the rotating protostellar disk, but interactions and changing orbits may modify the spin (Venus, Uranus).

Of course, but the real question is, how many life-bearing planets have a very long rotation period? My guess is, this is pretty rare, but pretty rare is still enough to invalidate the GRB==doom hypothesis.

- Are there rotation axis directions and orbital precession constants for planets that would keep GRB radiation mostly in one hemisphere, leaving the other to develop?

If you do not have the problem of heating and evaporation of the atmosphere I mentioned above, then yes, that is probably possible. For example if the GRB goes off from the direction of the spin axis ("below/above the solar system"). This may safe you from one GRB, but since GRBs come randomly from all directions it is not failsafe across many billion years.

- How many planets might have other special circumstances that protect their ozone (such as a lack of N2 in their atmosphere, or an ozone generating biology in their stratosphere, etc.)

Not sure. I think it is possible to come up with such scenarios as you stated, but it has to be shown that they are frequent occurrences to be relevant for changing the survival rate of complex life.

Exactly. To say that GRB==doom means that all of these possibilities must be very infrequent indeed, and I just don't see how we can say that at present. That makes me dubious about the hypothesis.

Re:I am dubious

[buchner.johannes]

The point is really that we don't nearly know enough to answer any of these questions. We can provide "best current thinking," but with only 1 actual sample (Earth) and no experience with GRBs, these are just guessitmates at best.

That's not true. We know the luminosity output of GRBs very well, as well as their spectrum across the electromagnetic spectrum. For a number of exoplanets (and the planets in the solar system) we know their main atmospheric content. For each composition of atmospheres you can predict the effects of a GRB for any chosen distance in terms of photo-dissociation, heating and radiation pressure. I don't see great unknowns there.

- How many planets might have other special circumstances that protect their ozone (such as a lack of N2 in their atmosphere, or an ozone generating biology in their stratosphere, etc.)

Not sure. I think it is possible to come up with such scenarios as you stated, but it has to be shown that they are frequent occurrences to be relevant for changing the survival rate of complex life.

Exactly. To say that GRB==doom means that all of these possibilities must be very infrequent indeed, and I just don't see how we can say that at present. That makes me dubious about the hypothesis.

I think it can be argued that due to the luminosity output of GRBs, that "GRB==doom" holds, within a certain radius and for typical orientations. That serves as a useful starting point. For special orientations, or special atmospheres that one could imagine, this may not hold. But then the burden is on the person dreaming up these scenarios to show that these can more happen frequently than expected due to random orientations and atmospheres representative of the gas make-up of observed stellar and star-forming systems (which is well-studied as well, the technical term is metallicity and (heavy) element abundance). Until then, I think "GRB==doom" is a suitable working hypothesis we can adopt.

Re:I am dubious

[mbone]

The point is really that we don't nearly know enough to answer any of these questions. We can provide "best current thinking," but with only 1 actual sample (Earth) and no experience with GRBs, these are just guessitmates at best.

That's not true. We know the luminosity output of GRBs very well, as well as their spectrum across the electromagnetic spectrum. For a number of exoplanets (and the planets in the solar system) we know their main atmospheric content. For each composition of atmospheres you can predict the effects of a GRB for any chosen distance in terms of photo-dissociation, heating and radiation pressure. I don't see great unknowns there.

- How many planets might have other special circumstances that protect their ozone (such as a lack of N2 in their atmosphere, or an ozone generating biology in their stratosphere, etc.)

Not sure. I think it is possible to come up with such scenarios as you stated, but it has to be shown that they are frequent occurrences to be relevant for changing the survival rate of complex life.

Exactly. To say that GRB==doom means that all of these possibilities must be very infrequent indeed, and I just don't see how we can say that at present. That makes me dubious about the hypothesis.

I think it can be argued that due to the luminosity output of GRBs, that "GRB==doom" holds, within a certain radius and for typical orientations. That serves as a useful starting point. For special orientations, or special atmospheres that one could imagine, this may not hold. But then the burden is on the person dreaming up these scenarios to show that these can more happen frequently than expected due to random orientations and atmospheres representative of the gas make-up of observed stellar and star-forming systems (which is well-studied as well, the technical term is metallicity and (heavy) element abundance). Until then, I think "GRB==doom" is a suitable working hypothesis we can adopt.

I do not. The trouble with GRB==doom is that you have to bring in statistics, and we don't know what they are, but we do know that they have to be pretty extreme. For example, a galaxy might have 100 billion "Earths." Suppose that there 1/1000th that number of "warm Venus's," (a Venus type planet, but far enough out from its star that there never was a run-away greenhouse), and that the chance of advanced life forming on such a body is 1/1000th of the typical "Earth," but none of the Venus's are wiped out due to GRBs. That still leaves 100,000 warm Venus's to form complex life. Now, are those numbers reasonable? Sure. Are they true? You guess is as good as mine. However, even if the Venus situation had a probability of one chance in a billion of occurring it would still leave 100 systems where complex life could arise, and that is a lot more than 0.

I think that there are a lot of these situations - I think the proponents of "GRB==doom" have to show that each one has probability 10^-11 or so, and I don't see how they can do that.

Re:Hire an H1B to write headlines and summaries

[xaotikdesigns]

Detonation: a loud explosion; combustion of a substance that is initiated suddenly and propagates extremely rapidly, giving rise to a shock wave.

Sounds kinda like what happens when a star goes nova and explodes. In fact, it looks like Explosion is listed as a synonym of Detonation.

What exactly is your problem here?

Our galaxy is one of those 10%

[djnanite]

On the plus side, it seems that our galaxy is one of the 10% capable of supporting life.

So at least we only have to start looking locally...

Re:Life existed before the Ozone layer

[K. S. Kyosuke]

There's also nitrogen oxide generation and direct lethal radiation to consider.

It's life Jim, but not as we know it...

[GrahamCox]

If the environment of such worlds has large amounts of gamma radiation, surely whatever life evolves there will naturally be able to cope with it? Maybe our namby-pamby DNA-based life couldn't survive under those circumstances, but it's probable that there are trillions of alternatives.

Re:It's life Jim, but not as we know it...

[Streetlight]

Silicon based life eating it's way through a planet might evolve.

Looking Down the Barrel

[AbsoluteXyro]

As I understand it in order to sustain catastrophic, life eradicating damage from a GRB you need to be looking directly down the "barrel of the gun" so to speak, or rather directly in the line of fire emanating from the star's poles. This forms a fairly narrow beam of intense energy that decreases with distance. It doesn't seem that likely to me that 90% of life supporting planets in the universe would find themselves in just this predicament.

Re:Looking Down the Barrel

[mbone]

As I understand it in order to sustain catastrophic, life eradicating damage from a GRB you need to be looking directly down the "barrel of the gun" so to speak, or rather directly in the line of fire emanating from the star's poles. This forms a fairly narrow beam of intense energy that decreases with distance. It doesn't seem that likely to me that 90% of life supporting planets in the universe would find themselves in just this predicament.

Yes, but all of the GRB we see are "looking down the barrel" and so the statistics already take that into account. (In other words, if each GRB irradiates 1% of the sky, and 100 go off "near" you, you are still likely to be in deep trouble.)

Even 10% is a big number

[HangingChad]

Of the estimated 100 billion galaxies in the observable universe, only one in 10 can support complex life like that on Earth

10 percent of 100 billion is still 10 billion galaxies. That's a lot of real estate. Even if you apply all the other characteristics that give rocky planets in the habitable zone of their star billions of years to evolve life. There are features like having a Jupiter in a circular orbit instead of an elliptical orbit or a moon that creates tide pools. That's a lot of habitable planets and a lot of potential for intelligent life.

Netflix has a really interesting series narrated by Laird Close called Life In Our Universe that covers the topic in great detail.

Re:Even 10% is a big number

[rahvin112]

Carl Sagan talked about it. Look at a planet like Titan. It's got oceans of hydrocarbons. It's far enough from the sun and cold enough to have not developed life, but we can't rule it out. There is simply so many organic molecules there that any life that did exist would be overwhelmed with food.

But more importantly, in both cosmos version they discuss this very point, even if life is a 1 in a billion or 1 in a trillion chance there are still going to be literally billions of life bearing planets out there because of the shear size of the universe. Humans have very difficult time with the size of numbers involved, even physicists do, we just have no real life experience with numbers that big. The universe is so big we've only roughly mapped about 30% of what we can see and we can't even see that far. Look at the Hubble deep field shot and ask yourself how many galaxies you can see, and that was shot on a a piece of sky that's miniscule from earths surface.

What Exactly is "Life" Anyway

[l0ungeb0y]

These "Astrophysicists" are incredibly short sighted if they think we have any idea as to the variety of life forms that exist throughout the universe from our limited view from our ecosystem on the Planet Earth. Sure -- we might have a pretty good understanding as to some of the life forms we might see in a yellow dwarf star system on a rocky planet with a nitrogen and oxygen based atmosphere -- but who's to say what life forms may exist in other galaxies, or what comprises an organic body or living entity? Why couldn't a nebula for instance, form some sort of organic neural network that allowed it to sense and convey information around itself? How could we say that a space dwelling life-form that subsists on radiation as we do on water is implausible? What type of life would we see in our own solar system on moons that have liquid methane oceans rather than liquid water?

Re:Lots of misconceptions here.

[PIBM]

I would disagree with that. Look at antibiotics. It`s not present in everyday's bacterial environment. A single event (high dosage of antibiotics) wipes out most of the population, yet some survive, and rare case some evolves to resiste them. And now we are getting stucks with bacterial agents that survive a lot of our antibiotics. why could not it work that way for those too ?

Aren't GRBs tightly focused?

[Solandri]

I only had time to skim TFA, but it sounded like they did a strict radial distribution from a GRB source to a potential life-harboring planet. i.e. if there's a GRB of x magnitude and it's within y parsecs of a planet, assume life on that planet is wiped out.

If I remember, GRBs are focused so most of their energy exits out the rotational poles. If you assume galaxies formed from a cloud of matter spiraling down and clumping together, then the stars and planets in a galaxy will tend to have the same angular momentum vector - that is, they rotate in pretty much the same plane as the galaxy. That means the rotational poles are oriented along the thin dimension of the galactic disk, and thus most of the energy from a GRB only impacts the star systems "above" and "below", not the huge bulk of systems "beside" the GRB star. That would drastically reduce the number of star systems "in the crosshairs" of a GRB. Obviously there are exceptions (Uranus' rotational axis is tilted 98 degrees), but without knowing the frequency of such exceptions it would seem impossible to accurately estimate how much life GRBs could potentially wipe out.

Re:Hire an H1B to write headlines and summaries

[wonkey_monkey]

The problem is it can be unclear what is meant, or if something is being implied, when people start throwing in synonyms for no real reason. We're not all experts in the field, so when a summary throws in two terms - especially one which, in common usage, often implies a deliberate act (a detonation being the initiation of an explosion) - it's not unexpected that some people might find it confusing - even if all it does is raise suspicion that there might be some extra meaning for the differentiation that's escaping the reader.

Which kind is the Milky Way?

[BenSchuarmer]

We may want to see about relocating...

Drake equation...

[morethanapapercert]

Of course, all of us here are familiar with the Drake equation, something this article certainly applies to.

But I wonder, has anyone made a serious attempt at coming up with real numbers for the various variables to see what the final number was? Every attempt I've seen thus far at solving the equation either uses very loose figures or doesn't enumerate the variables at all.

What I'd like to see is someone take the most rigorous numbers we can come up with, narrowing the estimated ranges as best as we can with current knowledge and then combine that with the stellar distributions we already have mapped. The idea being come up with our very best guess at the number of systems which harbour life (preferably intelligent life) and how big of a sphere of space would we have to explore before we are mathematically probable likely to encounter/discover alien life. I've seen the Seager Equation, which inherently implies the number of possible life bearing planets within a certain radius sphere {our detection range for biosignature gases} but still doesn't try to plug in the best numbers we can come up with.

There is the Texas U calculator, for anyone who has estimated values for the variables at Drake Calculator But I don't have the data to plug into it, nor do I have the skill needed to evaluate the usefulness of numbers I can search for on my own.

My take is tech makes radios sound like noise.

[Ungrounded Lightning]

I also subscribe to the "great filter" theory. About 25 years after the radio was invented, we were busy gassing each other in trenches, followed closely by a global pandemic, then mass genocide, then teetering on the edge of nuclear war. That's not a very wide window for aliens to notice our presence, if they rely on artificial radio waves to detect intelligent life.

My take is that technological improvements make radio sound like noise after a few decades. Early radios systems are very simple things which have signals (CW, AM, FM, ...) that are very distinct from electrical and thermal noise. Their signals were both drastically different from, and drastically stronger than, the background, enabling simple detectors to separate a signal's information from all that chaff.

Modern radios (such as spread spectrum systems, especially OFDM) squeeze nearly the Shannon Limit out of precious bandwidth (and also be frugal with transmit power) by using nearly all of it to carry information. This makes them virtually indistinguishable from a celestial object with a little extra heat (buried among things like stars, which have a LOT of heat).

It was only about 120 years from when Hertz and Tesla started making easily detectable radio waves to the Analog Television Shutdown, a significant milepost in the decommissioning of easily detectable radio signatures. I expect that, within anther few decades, the Earth will be emitting very little that might be recognizable as a radio signature of intelligent life, unless we expend a bunch of energy sending such a signature deliberately.

So my solution to the mystery expressed in the Drake Equation is that L (the length of time for which such civilizations release detectable signals into space) is short, not due to the falls of civilizations, but to economic incentives to use the aether only in ways that are no longer noticeable at a distance.

Re:My take is tech makes radios sound like noise.

[Anonymous Coward]

Even if it's not coherent, the earth will be putting out a _lot_ of radio noise. And as we divide the spectrum in bands, this will form a remarkable pattern. For instance, there's just an unexplainable lack of radio power in the GPS bandwidths. We need those bands to be rather quiet. ET won't understand why these bands exist; what natural phenomenon could cause them? That alone makes it interesting. The inability to decode the signal doesn't really matter. 21% oxygen in the atmosphere is the clue that explains how those strange radio transmissions are caused.

Ours?

[ISoldat53]

Does that include ours?

So, there are a lot more Republicans out there...

[cmeans]

It's the simplest life form, and so very, very plentiful.

Well, yes, back THEN....

[kenwd0elq]

We're pretty sure that most large galaxies have a supermassive black hole in the center. We know that some very-VERY-far away astronomical objects are very active in radio and X-ray output; we call these "quasi-stellar radio objects" or "quasars".

Is it not at least remotely possible that these facts are related? My physics degree is 30 years old and I have only sort-of kept up with the news, but it seems at least possible that those gamma ray bursts and quasars are symptoms of the formation or expansion of those black holes. Nearby galaxies seem quiescent by comparison, so since our observations of the very distant objects are also views back in time, I think it likely that those gamma ray bursts are more like childish temper tantrums, and that our own Milky Way has grown up and matured and is now ready to create new life of its own.

It's entirely possible that life on Earth arose about as early as it could have, and that we may be among the "senior" intelligent lifeforms around. Or, perhaps we're entirely alone, which carries with it its own philosophical baggage. It's interesting to speculate, but it's foolish to make definitive statements when we are 99.9% ignorant of what's actually out there.

Re:Rare Earth: Why Complex Life is Uncommon

[PPH]

simple life should be abundant in the universe.

Thankfully, only in reruns.

So that means...

[thunderclap]

If only 10% can support life can we strip mine the other 90%? Come on, you know some one will think of that in the future.

Brown Dwarfs

[BarbaraHudson]

The coolest brown dwarf known has a temperature between -27 and +127 degrees C. That is within the range of life, though it would be more like flatland, with the higher gravitation.

oh please....

[SuperDre]

They can't even find all the living organisms on this planet or in our own solar system, or even know how our own galaxy is even created, and they think they know only 10% of all galaxies have 'complex life' as on earth? Please get real.. We're not even a spec in our own galaxy, and I'm very confidend that in our own galaxy there are more 'complex life' out there than 10%.. let alone the much MUCH bigger galaxies...

HALO

[Saffaya]

"
Cortana _ You have no idea how this ring works, do you ?
HALO doesn't kill flood, it kills their food.
Humans, covenant, whatever. We're all equally edible.
You don't believe me ? ask him.

MasterChief _ Is it true ?

343 Guilty Spark _ More or less.
Technically, this installation's pulse as a maximum effective range of 25,000 light years.
But when the others follow suit, this galaxy will be quite devoid of life.
Or at least, any life with sufficicient biomass to sustain the flood.
"

Only bacteria left ? sounds about right :)

Re:The universe is not 13.8 billion light years wi

[mark-t]

I said it was 13.8 billion years old, I never once suggested it was 13.8 billion light years across, I am well aware that the observable universe is actually much larger than that... what I've always found interesting, however is that the ratio between the proposed estimate of 93 billion light years in diameter and the age of the universe at 13.8 billion years is within 8% of the value of 2pi. That could be a coincidence. of course, but hey.... maybe it's something to think about?

My point remains. The universe is finite.

But still

[kilodelta]

That's an awful lot of worlds with complex life on them. Now we just need to get working on FTL drive again.