Slashdot Mirror
The Disappearing Universe
StartsWithABang writes: "If everything began with the Big Bang — from a hot, dense, expanding state — and things have been cooling, spreading out, but slowing down ever since, you might think that means that given enough time (and a powerful enough space ship), we'll eventually be able to reach any other galaxy. But thanks to dark energy, not only is that not the case at all, but most of the galaxies in our Universe are already completely unreachable by us, with more leaving our potential reach all the time. Fascinating, terrifying stuff."
one of the allures for me (and i think a lot of people intrigued with cosmology) is how we can interpret the findings as a macrocosm for our own personal microcosm of awareness and being.
the fact that seemingly inherent in our physical universe is a doctrine of the futility of outward movement (vis a vis reaching a sense of completion or boundary), to me, points to the individual quest for seeking oneself by focusing internally.
Ignored as even a remote possibility as the author labels it sci-fi fantasy.
We can always hope that some type of controlled wormhole, or spacetime-bending faster-than-light travel can save us, but there’s no evidence that such an innovation—despite our best science fiction dreams—can ever be practically realized.
How open-minded and hopeful the author is...
Really, folks, you need to stop being terrified by everything.
Physics graduate student here, and I'd just like to bring something into context before any ./ readers begin an existential crisis.
We don't *KNOW* anything about the dark matter/energy hypothesis yet. They are not well accepted theories like (classical) gravity or electromagnetism, but rather the best answer to questions we don't have any other way of approaching.
Warning: if you subscribe too heavily to these ideas now, you'll be way, way off base later when science starts finding better answers to the accelerating universe and other open questions. This stuff is great for discussion about philosophy and science fiction, but it is far from well accepted science.
Nothing can travel through space faster than light. But space can travel as fast as it likes. This is the idea behind warp drive.
What a fool believes, he sees, no wise man has the power to reason away.
How can that be? I thought nothing could go faster than the speed of light.
Or does the universe not have to obey it's own rule?
We're talking about expansion of space itself, not about a body traveling in that space.
no, I don't have a sig
Much of the idea of wormholes came from the idea that universe might be spherical in topography --- like a hypersphere --- and a wormhole could poke through the hypersphere to create a shorter distance than even a line segment from Point A to Point B.
http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question35.html
http://en.wikipedia.org/wiki/Shape_of_the_universe
But measurements are looking like the universe is flat.
You never know what scientific discoveries the distant future could hold, but at the moment it looks bleak for the concept of wormholes since the universe doesn't seem to be a hypersphere at all.
Priest: "Universe from nothing, no laws of physics, sped up time"+ huge discrepancies. Creationism? No. Big Bang Theory
This. They're already unreachable now. And until someone comes along and proves Einstein wrong, they're going to remain that way too.
SJW's don't eliminate discrimination. They just expropriate it for themselves.
Well, space is a whole mess of nothing. If nothing can travel faster than the speed of light, no reason it can't expand faster than the speed of light. Also, that's faster than light where "faster" is measured in spacetime. Stretch the spacetime and light travels differently than it did.
This is less "News" and more "for nerds"
Though not particularly well read nerds on the topic of the expansion of the universe...
So he thinks that using the hypothetical limits of current technology with no hypothetical constraints wouldn't be good enough. Only 200 years ago we only had horses for transport, this fella wouldn't make an imaginative writer.
Yup. At "worst" in an accelerating universe the galaxies would be receding from us at speeds that would tend asymptotically to 'c', but never at 'c' nor above.
Maybe we deserve this world ?
"I'm thinking wormholes, warp drives, hyper space."
All of which are are unproven theories. And could be proven to be impracticable (needing an energy the size of a star E stills equals MC^2) or impossible, or dangerous aka destroying the universe.
It may be the Speed of Light is the Speed limit that we cannot break.
In a world where Science Fiction is still fiction, and these wormholes, warp drives, and hyper space are meant as plot devices to move your characters into the story conflict of dealing with something alien. You find that these plot devices are made especially for weekly serial TV or movies with Sequels as you want to keep the same characters time and time again.
Now that said, it doesn't mean we should stop space exploration or trying to break the limits. Even if we could get a fraction of the speed of light say 1/10th the speed of light. We could travel our own solar system as well the sailors of old traveled the oceans. Generational ships can bring us to stars that are within 10 light years of year, and come back to earth without too much diversion of evolution.
Even without having to jump galaxies there is so much in our little neighborhod that we haven't explored.
As per Douglas Adams:
Space is big, I mean really big, you won't believe how mind boggling huge it is. You think it is a far way to the chemist? That is just peanuts to space, listen!
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
It's not that the thing itself is flying away from us at c, it's that all the space in between us and that thing is expanding. Naturally the further away it gets, the more expanding space there is between us and the thing, the faster the thing appears to be receding from us.
In this system nothing is moving faster than the speed of light but the effect is the same: a spacecraft trying to reach that galaxy would need to overcome all the expanding space between, and that would require a speed greater than c. In fact, at that point even light from that galaxy would not reach us anymore, putting it outside our cosmological horizon.
Disclaimer: I may not know what I'm talking about. This should really be in my sig.
Murphey's fighting Occam, and we're in the stands.
Honest question here, I thought the expansion was still accelerating. Is it or it's really slowing down as the summary says?
Likely the more correct statement is the maximum speed of light is the speed of gravity. So there are quite few particles that travel faster than the speed of light. Now when it comes to reaching other galaxies, seriously who really cares, there is just so much of this galaxy to explore, even living to really ripe old age of 10,000 earth orbits and travelling really fast from sun to sun, there are so many places, likely so many species and societies to explore, even allowing only 1 luna orbit at each location, let alone travel time, likely you won run out of 'interesting' places, just like our own, to explore just in this galaxy. All you need to do is slip on by gravity.
Chaos - everything, everywhere, everywhen
It's not really that fascinating or terrifying, though. "Based on our current understanding, we will never be able to reach certain galaxies." Ok, that's cool. We can't even reach another star system within our own galaxy at the moment, so traveling to other galaxies is a bit moot as is. We also know our understanding isn't complete, so it's entirely possible that something we don't know will allow us to travel to those galaxies.
Seriously, this doesn't feel like news. We've been working at the whole science and technology thing for what...ten thousand years or so? I say give it a million more and see where we are then, instead of cranking out sensationalist doom and gloom articles. Of course, all the doom and gloom articles tell you that we're not going to make it another decade, let alone a hundred thousand decades, so if you really feed into such things, then I'd say your outlook on the universe is far more terrifying than the article at hand.
it's running away from Windows 8
Odds are pretty high that we will never reach the next star, worrying about the next galaxy is a bit too much
Now I'll never find the missing socks
The problems are a bit deeper than "we don't have the technology to do it". If we would be able to break these theoretical speed limits, this would automatically imply we would also be able to travel through time or at the very least send messages into the past. That would create a whole bunch of problems for concepts like causality, free will, grandfather paradox, etcetera. Not entirely impossible, I agree, but unlikely nonetheless.
Is anyone else tired of Slashdot constantly posting the submissions of people promoting their own websites?
The sub-headline is enough "Even at the speed of light, you’ll never reach these galaxies." Say you wanted to go to Andromeda, not the closest galaxy but not exactly far on a galactic scale, At the speed of light that's still going to take 2.5 million years to get there, not really what most people would define as achievable, If we want to reach any other galaxy we're going to have to be going a hell of a lot faster than the speed of light.
Wanna buy a shirt?
https://www.redbubble.com/people/stealthfinger/shop?asc=u
For Andromeda, just wait (very long term stasis recommended) it's comming at us, not sure it's a good thing.
Likely the more correct statement is the maximum speed of light is the speed of gravity. So there are quite few particles that travel faster than the speed of light.
I think you missed a few logical steps out there. Also, the names of these faster-than-light particles would be good to know.
systemd is Roko's Basilisk.
Nope. Distances between objects can increase faster than c because space is expanding.
systemd is Roko's Basilisk.
I understand your reasoning, but I question the math. The time for light to travel from Earth to Andromeda is, essentially, zero (0) seconds. The time for humans to WATCH it do that is 2.5 million years. Recall the Twin Paradox where a person leaves Earth at near light speed, returns, and is way younger. The stay-at-home twin thinks the traveling twin has been gone a long time and the traveling twin says, "Hey. I just left!"
It little behooves the best of us to comment on the rest of us.
Wormholes ok, they at least have a theoretical framework in modern science. Warp drives...well if you're talking about moving a space bubble relative to space itself. But since when did "hyperspace" become even a remotely scientific theory?
"But not if our Universe is accelerating. If something is receding from us right now at more than 299,792.458 km/s—faster than light speed—and it’s accelerating too, how could anything reach it?"
Isn't c the upper bound of speed in our universe?
is the upper bound of acceleration through space. Think of it this way. acceleration of a point through the 3d graph of space IS limited to C. But the lines of the graph itself that define the 3d location of things in space are accelerating from each other... the farther they are from each other the farther they recede. There is no limit to that recessional velocity. You will get to a point where acceleration being fixed simply can't keep up with the recession, so you'll never reach those parts., nor will light from those parts reach your position. Vice versa applies here. We're receding at a speed greater than light from those areas. We're not feeling relativity effects because we're moving WITH OUR SPACE
I'm surprised that no one has yet mentioned the ultimate consequence of this recessional acceleration. Eventually the regions where this shows as an effect become smaller and smaller. Galaxy super clusters, then clusters, then galaxies fly apart, and that's when the effect really accelerates, shortly there after, solar systems, stars, planets, and ultimately even the atoms that once composed you and I fly apart as even as the recessional lines of space, accelerated by dark energy rip our observable universe down to a literal NOTHING. So the other end of the Big Bang becomes a Big Rip. Look it up.
Although perhaps under such circumstances concepts like "receding" and "moving" become a bit more ambiguous than we're used to.
systemd is Roko's Basilisk.
Yup. At "worst" in an accelerating universe the galaxies would be receding from us at speeds that would tend asymptotically to 'c', but never at 'c' nor above.
You haven't begun to imagine the worst. see my post above.
Space itself is expanding and there is no limit to how fast that can happen. It can be at 1000 times the value of c if necessary.
Also, the names of these faster-than-light particles would be good to know.
They are called "tachyons".
If Pandora's box is destined to be opened, *I* want to be the one to open it.
The problem is that even with FTL speeds things are still too far apart. Assume you could do 10*C it would still take 3000 years to the center of the galaxy or 10,000 years to the outskirts of Andromeda. 100*C and you are still into many multiple lifetimes of travel just to get there. The distances are so great as to be unapproachable.
Unreachable with current technology perhaps, but who knows about the future?
The future, Conan?
#DeleteChrome
> Unreachable with current technology perhaps, but who knows about the future?
Unreachable with current physics known to man kind. Not just current technology.
Hivemind harvest in progress..
They are called "tachyons".
And that almost certainly don't exist, which was my point.
systemd is Roko's Basilisk.
"Warning: if you subscribe too heavily to these ideas now, you'll be way, way off base later when science starts finding better answers to the accelerating universe and other open questions. "
Every damn hypothesis we have are only good as long as we do not find any better answer. Even the one you call better supported. Heck, 150 years ago you would probably have put newton in your list.
It is the basic reality in physic that we use what we have as hypothesis until a better theory or falsifying data come up and disprove that theory. By *specially* asking us to hold off for dark matter/ dark energy you are specially pleading against those, which is a nono, or you misunderstood science in general which is worst.
Even classical gravity or electromagnetism are a temporary hold on until something better come up. Something better MAY never come up. Or it could next month. This is the beauty of science. Adapting.
C. Sagan : A demon haunted world:
http://www.amazon.com/gp/product/0345409469/
visit randi.org
I am not saying we will find FTL travel method - but they are assuming we won't which is foolish.
There's a lot of evidence we won't. We would have found it by now if someone has discovered it in the future.
Who ordered that?
There are no limits to how fast you can travel. Physics allows you to go to the centre of the Milky Way and back in a day (well, as long as you avoid the black hole that is probably there). Of course the Earth will be somewhat older when you return, but for you only a day has passed.
Finally! A year of moderation! Ready for 2019?
I've read that it's only 30 years, ship time, at one gee acceleration all the way, longer if you want to slow down and stop once there. Even the edge of the visible universe is achievable in a human lifetime (80 years IIRC) at one gee, of course by the time you get there the edge will be much further away.
Just need close to infinite free energy.
https://en.wikipedia.org/wiki/Inverted_totalitarianism
That's not right; only from the light's perspective maybe.. it's still "only" traveling at 186kmph a second, it's not truly instantaneous. And I've never heard of the theory that suggests that if a person leaves earth and travels near light speed he'll be younger when he returns. He might not have aged, but not younger... unless he actually exceeds light speed.
Look back up at my post, now look back down, you're on the Internet. Now look back up. I'm a signature.
Yes, but this is a physics article and not a science fiction one so there is both a speed limit and no Wookies available.
Assume you could do 10*C it would still take 3000 years to the center of the galaxy
Nope. At 0.9999999c it will only take you 11.6 years to get to the center of the galaxy (plus, say, a year or two for acceleration).
Now, admittedly, this doesn't mean you'll be able to make it back in time to see how the world copes with the 2038 problem - or even the events of Dune - but travel time is not an issue.
systemd is Roko's Basilisk.
but I think it's interesting how well it lines up with observation.
I think your example is tautological. It doesn't really imply anything about the shape of our universe. The only observation it lines up with is "space is expanding" which would be the same if the universe were on the surface of any other hyper-shape, wouldn't it?
systemd is Roko's Basilisk.
At least in astronomy beyond naked-eye observation.
The universe is so vast that it boggles my mind. Just the distance between star systems in our galaxy is huge, then when you start thinking about the distance between galaxies, and then that there are clusters of galaxies... and the distance between clusters of galaxies. It's too much.
Not to mention that it pretty much puts the kibosh on things like intergalactic travel, probably even interstellar travel too.
Say you wanted to go to Andromeda, not the closest galaxy but not exactly far on a galactic scale, At the speed of light that's still going to take 2.5 million years to get there, not really what most people would define as achievable, If we want to reach any other galaxy we're going to have to be going a hell of a lot faster than the speed of light.
Note that it is 2.5 million years from perspective of Earth. From perspective of the traveller, at speed of light the trip would be instantaneous.
I'll leave it as exercise for someone a bit more fresh with related math (or more motivation to Google) to calculate a more realistic figure: how much time it would be take to travel to Andromeda at constant 1G acceleration/deceleration, both Earth and ship time.
The movement away from the timeline is expected in alternate universes. The other universes are what could have been, but in a different timeline.
Obviously I'm no astrophysicist, but how many galaxies could we potentially have already lost sight of? How many could be just beyond this horizon already?
No. That would be assuming you can go faster than the speed of light, without limits, which isn't the case.
Even if you were a massless particle, you would reach the speed of light in less than 1 year of accelerating at 1G, and then, you wouldn't be able to go faster.
http://space.stackexchange.com/a/841
Doesn't that require the appearance of an event horizon between these objects ?
Maybe we deserve this world ?
You're forgetting the Space Nutters. You know, those people who think a TV show from the '60s with bad actors in polyester shirts was somehow a "promise" about the future.
They'll kick and scream and fight and reply nonsense if you ever tell them no one's going anywhere.
The sky will slowly go black until it's as depicted in Greg Egan's "Quarantine" ? Well, except for our own galaxy being still visible and reachable... that's a consolation prize alright.
Maybe we deserve this world ?
Math allows you to go to the centre of the Milky Way and back in a day....
Corrected that for you.
That's not right; only from the light's perspective maybe.. it's still "only" traveling at 186kmph a second, it's not truly instantaneous. And I've never heard of the theory that suggests that if a person leaves earth and travels near light speed he'll be younger when he returns. He might not have aged, but not younger... unless he actually exceeds light speed.
Probably it was some type of a typo where he meant the returning brother is way younger than the brother that stayed (as opposed to just being "way younger" as stated in the OP's poorly worded response.)
Also, and playing Devil's Advocate a bit more, when the OP wrote this:
The time for light to travel from Earth to Andromeda is, essentially, zero (0) seconds
I'm reading it as the time that light (or anything travel AT the speed of light) "experiences" traveling from Andromeda to the Earth (or pretty much from any point A to any point B) is zero because of time dilation. True, it will take 2.5 million years (when measured from the POV of an observer not traveling at relativistic speeds), and travel is not instantaneous, but the traveler itself will experience time at a complete stoppage when travelling at the speed of light (or falling down a singularity) regardless of having traveled one inch or the entire width of the observable universe.
It's not proving Einstein wrong that's going to happen. It's trying to find an exploit in the laws of physics that needs to discovered.
Life is not for the lazy.
I admit to being fuzzy about, "younger." The twin left behind would judge the traveler to be "younger," but my sentence structure doesn't actually reflect that. Both individuals, when reviewing their own experience, would insist that they have not noticed any unusual aging one way or the other. And, you're right ... the traveling twin would not be younger, from his perspective.
I stick by my statement that light travels from one end of the universe to the other instantaneously.
Run the numbers for length contraction and time dilation for a mass-less photon.
It takes no time to travel no distance.
It little behooves the best of us to comment on the rest of us.
No. That would be assuming you can go faster than the speed of light, without limits, which isn't the case.
Even if you were a massless particle, you would reach the speed of light in less than 1 year of accelerating at 1G, and then, you wouldn't be able to go faster.
Nope. GP was correct: note he said 30 years ship time You can accelerate at 1G indefinitely and you won't exceed the speed of light. You will asymptotically approach the speed of light, and time dilation will make the trip seem very short to the crew on board the ship.
Now calculate the reaction mass required.
If it recedes faster than c, you can count on it receding way faster than Java.
Hi bhagwad,
I think your post needs some clarification.
You wrote:
> After a while, space itself would expand meaning that the ruler will now be longer than what it was.
The expansion of space must be measured with respect to something. The usual idea is that space is expanding with respect to other properties of the physical world, e.g., the mean distance between electron and proton in a hydrogen atom. So, because your hypothetical ruler is made of atoms, the claim is that tomorrow it will take more of those rulers laid end to end to reach distant galaxies.
In contrast, one kind of "ruler" that _is_ changing when space expands is the wavelength of photons and other ultrarelativistic particles. If space expands by 1%, photon wavelengths increase by 1% (as measured w.r.t. your hypothetical 1 meter ruler made of ordinary material) and thus photon energies decrease by 1%. This change is the explanation for the redshift of light from distant galaxies.
> After a while, the space between the nucleus and electrons or within the nucleus itself will become too large, ultimately ripping apart for the fabric of reality itself.
I suspect you are referring to cosmological models that end with a "Big Rip". In these models, the amount of dark energy in a constant volume of space (as measured with an ordinary ruler) increases with time. Eventually, the density of dark energy becomes greater than the density of other kinds of energy, e.g., the binding energy of atoms. Then fluctuations in this dark energy will rip apart atoms.
Because the properties of dark energy are hard to measure, it is not yet clear how its density changes with time. The current so-called "standard model" of cosmology, Lambda-CDM, takes the density of dark energy as constant, and this assumption is consistent with our best current measurements. So, as far as we can now tell, we are not living in a "Big Rip" universe.
It's not proving Einstein wrong that's going to happen. It's trying to find an exploit in the laws of physics that needs to discovered.
Course, if you believe in alien visitation then the whole physics exploit thing is a given.
Admittedly, that's a rather large 'If'..
..Mullah or Pope, Preacher or Poet, who was it wrote: "Give any one species too much rope and they'll fuck it up"?
Responded on the wrong comment and wasn't logged in.
Let's ignore all relativity and use kinematic equations
vf= vi + a*t
vf^2 = vi^2 + 2*a*d
So assuming our inital velocity at earth is 0
vf = a*t
vf^2=2*a*d
(a*t)^2 = 2*a*d
a^2*t^2 = 2*a*d
t^2 = 2*d/a
Discarding negative time
t = sqrt(2*d/a)
So let's call the halfway point our final destination and double it in the end.
2*t = 2*(sqrt(2*(1.216*10^22 m)/(9.81 m/s^2)))
http://www.wolframalpha.com/in...
Now lets see how fast we'd have to be going
vf = vi + a*t
vf = 0 + (9.81 m/s^2)(2232 years)
http://www.wolframalpha.com/in...
So 1151 times the speed of light.
Good luck past the the speed of light, and all the of relativistic effects like Lorentz contraction...
With my current understanding or lack thereof, I have logical splinter in my eye with the whole space/time fabric itself expanding / "think surface of a balloon" thing meaning galaxies are flying apart.
Mind you, I'm an armchair cosmologist at best, so mine is more an interested layman's point of view; so I'm all ears (eyes) for an explanation. I'm not trying to refute the standard understanding here, or look smarter-than-thou, I just see what looks like a logical conundrum, what with my limited grasp of cosmology, and am asking where I'm riding off the rails.
Okay, space is expanding. All of space. The universe itself. That is, the space-time fabric is expanding. I have no problem with that. But this would mean, not only the space between galaxies, but the space within galaxies as well; and everything within their star systems, and then everything that comprises their stars, planets, asteroids, etc.. Meaning the galaxies themselves are expanding at the same rate the space between them is, isn't it? Everything, large or small, is expanding together as the space-time fabric swells/stretches/grows? Even the space between atoms should be expanding too, because space is space.
Wouldn't that just mean that since everything is expanding together, from a relative viewpoint, nothing is really changing? Aren't we all growing in size along with the rest of the universe right now?
Go back to the balloon model a second: if I draw five 2cm diameter dots on a balloon that's 25% inflated, let's say those five dots represent galaxies: now, inflate the balloon to full size- 100%. The dots now measure ~ 8cm in diameter (actually I'm not sure it'd be 8cm, but the general principle holds) Not only did the blank space increase, but so did the size of the dots. Relative to the size of the dots/galaxies themselves, the distance between them is still the same relative percentage of what it was before.
So.. how is it that inter-galatic space is expanding, but relative to that, intra-galatic space isn't? Is it due to gravity? Or maybe the proposed dark matter that encircles galaxies?
Look back up at my post, now look back down, you're on the Internet. Now look back up. I'm a signature.
Do you realize that the whole point of the GP's "exercise" was that you can't ignore relativity? It is due to relativity that the time observed by the traveller would be so little. If you are travelling at a velocity very close to the speed of light, in your own frame time is essentially standing still. You would get to your destination before you could blink your eye.
Now redo the calculations taking time dilation into account.
There was a young lady named Bright,
Who could travel, faster than light.
She went out one day,
In a relative way,
And returned the previous night.
Red to red, black to black. Switch it on, but stand well back.
Scenario 1 where gravity wins is completely idiotic mathematical fantasy. It clearly shows the author has no idea what they're talking about. Mass farther away from each other results in less gravity attraction on each other. So if there was enough mass to cause a big crunch then right now, everything would be contracting. Otherwise what the hell do they think is slowing down the stars' outward momentum, wind resistance? So to review, gravity is getting weaker and the velocity is staying the same...and it's supposed to all come back together. Right.
Oh by the way, did you notice, that she said matter is moving away faster than the speed of light, which is bullshit. Then while they're moving away faster than the speed of light, we know they're doing it because they're sending light back our direction at the speed of light and it's getting here, which is bullshit. In case you didn't catch that, I'm driving away from you at 100MPH and I throw a baseball at 75MPH at you and it reaches you and from that baseball that allegedly got to you, you can tell that I'm accelerating...riiiiiight. And they fail to mention that they only way we're traveling through space is faster than light, some sort of weird quantum thing, by bending space, or via wormholes so saying we'll never reach them is bullshit.
What a complete and utter crock of shit.
It's actually science fiction since not a word of it is true or based on real science.
"We can always hope that some type of controlled wormhole, or spacetime-bending faster-than-light travel can save us, but there’s no evidence that such an innovation—despite our best science fiction dreams—can ever be practically realized"
Okay, let's break that down. Nobody can travel faster than the speed of light except for 30% of the universe that's already traveling faster than the speed of light, according to this idiot author. Then "no evidence?" Really, no evidence that we can bend space? We discovered this thing called gravity that bends space. There are mathematically sound theories of how black holes bend and compress space or fold it or punch through it. There's this other thing that bends space that we invented called "moving." If you do a lot of it, you dilate time and bend space. We've pretty much proven the existence of higher dimensions as well.
In fact, I already invented faster than light travel. Pretend we're on a planet on the opposite side of the universe. From their perspective, we're moving away faster than the speed of light. So I, right now as I sit here typing this, am violating the laws of physics and traveling faster than the speed of light. Maybe I'll get some kind of nobel prize! Yay! This moronic author certainly won't. Maybe a literary award for science fiction.
But you're forgetting that the author just said there stars and planets right now are flying around at faster than the speed of light so don't worry, apparently the speed of light is bullshit and you can go as fast as you want. Seriously, who approved this pile of uninformed science fantasy bullshit article?
We can bend space already dude. It's called mass, gravity, and movement. You know, gravity bends space itself and moving that mass at a high speed dilates time because of the bending of space? It's proven already.
Best description I have is that dark energy isn't the explanation, it's the description of the problem.
I thought hyperspace was supposed to be a fictional alternate dimension ala Asimov. What has that got to do with the bending of spacetime by objects?
We will still merge with Andromeda and perhaps the entire Virgo Cluster. http://en.wikipedia.org/wiki/M...
"Love heals scars love left." -- Henry Rollins
Not as far as the light is concerned. Photons do not experience time (due to time dilation). If you were able to travel at the speed of light (you can't), the entire future of the universe would pass by instantaneously (from your perspective).
We're Doomed. Dooooomed.
Space is nothing and nothing can go faster than the speed of light :-)
This was deep... I'm going to have to spend some time staring at the stars tonight and contemplate this. Thank you.
Here's to hot beer, cold women, and Glaswegian kisses for all.
At which point the rest of your post becomes pointless.
As you approach the speed of light, it takes more and more energy to go faster (actually this depends on the frame of reference). Regardless, you can continue to apply 1G of acceleration indefinitely, but not exceed the speed of light.
The 30 years or 80 years or whichever is ship time due to relativity, not observer time.
Depends on what you mean by "lost". We've seen the Cosmic Background Radiation in all directions. This predates the first star. Now if by "lost" you mean unable to communicate with, even if each relay has massive amounts of time inbetween, then yes, many galaxies are already lost. Some are expanding away from us faster than the speed of light (or will be right before any photon we send could hope to traverse the distance). Some are just close enough they could intercept a signal, but the reply back wouldn't make it due to expansion. There is also the possibility of younger galaxies that formed in a region of space that is expanding away from us too fast.
"Love heals scars love left." -- Henry Rollins
Okay, space is expanding. All of space. The universe itself. That is, the space-time fabric is expanding. I have no problem with that. But this would mean, not only the space between galaxies, but the space within galaxies as well; and everything within their star systems, and then everything that comprises their stars, planets, asteroids, etc.. Meaning the galaxies themselves are expanding at the same rate the space between them is, isn't it? Everything, large or small, is expanding together as the space-time fabric swells/stretches/grows? Even the space between atoms should be expanding too, because space is space.
Wouldn't that just mean that since everything is expanding together, from a relative viewpoint, nothing is really changing? Aren't we all growing in size along with the rest of the universe right now?
From WMAP observations expansion rate is very low on order of ~60km/s for any given ~3.3 million light year stretch of space. Gravitational forces overwhelm dark energy at scales of galaxies and clusters of galaxies. Result is only observable things that really change is distance between large gravitationally unbound objects.
Not only did the blank space increase, but so did the size of the dots. Relative to the size of the dots/galaxies themselves, the distance between them is still the same relative percentage of what it was before.
Only space between things get bigger not the things themselves however there should be local effects in form of very very subtle loss of relative energies.
So.. how is it that inter-galatic space is expanding, but relative to that, intra-galatic space isn't? Is it due to gravity? Or maybe the proposed dark matter that encircles galaxies?
Yep gravity. Dark matter is also very important as it provides most of the gravity.
At the speed of light, time dilation means that you experience zero elapsed time, not the 2.5 million years everyone else observes.
If we would be able to break these theoretical speed limits, this would automatically imply we would also be able to travel through time or at the very least send messages into the past.
But in our universe is there really a Time dimension to travel through to the past?
http://phys.org/news/2012-04-p...
http://discovermagazine.com/20...
I've never found it convincing that there is a past to go to, at least from the perspective entities in our universe bound by its laws (from the perspective of "someone outside" running the "simulation/VM of our universe" all bets are off ;) ),
Wrong on so many levels.
1) Yes, they are moving away from us at faster than the speed of light. This is well established.
2) As long as the photons reach a region of space receding at less than the speed of light, we can see these galaxies. Good info here
3) "And they fail to mention that they only way we're traveling through space is faster than light, some sort of weird quantum thing, by bending space, or via wormholes" None of which have been shown to exist. And there's some evidence that none of these options can exist.
The idea is not that things *cross* space at greater than the speed of light, but that space expands so that the distance increases faster than the speed of light.
(Admittedly I've never heard a good explanation why that would make any sense without bringing back the luminiferous aether or a universal stationary frame of reference.)
Yes. At least, I think so. Although "appearance" might be a slightly misleading term to use, event horizons being abstract.
systemd is Roko's Basilisk.
No, those places are accelerating away from us much faster than 1G. Well, depening on the coordinate system you use to calculate that acceleration, obviously. But with cosmological coordinates, yes, way more than 1G and faster than the speed of light. In any case, you will never reach their speed no matter how fast you accelerate, since you can't go faster than (local) light and even light will never catch up with them. Even if you shine a strong laser at them, that light will never get there.
(Assuming our current theories about the inflation of the universe are correct)
Rockets, the horse drawn carriage of interstellar space flight.
That's exactly why it would be unlikely that any technological breakthrough would allow us to get to those places. If we can do that, then you can set up a thought experiment sending things back in time by juggling coordinate systems.
We can bend space already dude. It's called mass, gravity, and movement. You know, gravity bends space itself and moving that mass at a high speed dilates time because of the bending of space? It's proven already.
That's not hyperspace. Hyperspace is where you leave our space (xyz coordinates) travel to a different space (ijk coordinates) where the physical laws are different, or the distance between to corresponding points in our universe are closer. Thus we either are allowed to travel faster than lightspeed or travel less distance in a universe that is not bound by our rules. Closest thing I can really think of in actual science would be string theory and their extra dimensions or some other possible evidence that other dimensions might exist (eg possibly through evidence of a non-isotropic universe), but I don't think there is anything that has really stated that the physical laws there would be different or what they would be if the were. That doesn't even begin to discuss how we would get there if it did exist.
As you approach the speed of light relativistic effects slow the passage of time.
At the speed of light, time cease to pass. Light in effect travels instantly from its perspective (in a vacuum, not sure what happens when its in a medium and slows down). We see the light move, but if you were a photon, your entire existence would be instantaneous from start to finish. Only an outside observer not moving at the speed of light would see light 'travel'.
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You have a whole planet you've barely explored. I guarantee that there are more places you could go and more things you could see than you'll ever get to in a lifetime.
I'll bet there are places within ten miles of where you live that could amaze you, if you were suitably prepared to be amazed. Unfortunately most people could go for a walk in the woods and not see trees, just green blobs on sticks. Well of course if you're so ignorant you can't even name the tree, you won't see how amazing that tree is, and how it connects to other plants and animals. How much could you really expect to get out of visiting an alien planet if you aren't interesting in exploring *this* one in person?
And as for alien cultures, what about those immigrant neighborhoods people are always griping about, the ones where the residents are "too lazy to learn English"? There's an alien culture right there for the exploration, practically on your doorstep. You could spend a few weeks learning a few foreign phrases and see whether you can navigate that Haitian neighborhood, or order dinner in Chinatown using Mandarin. If that doesn't strike you as an adventure, if it sounds like it's just too much trouble, what makes you think you'll find civilizations on *other* planets worth the bother?
The only people who'd really get much out of travel to an alien planet are the kind of people form whom *this* planet remains an inexhaustible source of fascination and adventure.
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For the benefit of others:
While special relativity constrains objects in the universe from moving faster than light with respect to each other when they are in a local, dynamical relationship, it places no theoretical constraint on the relative motion between two objects that are globally separated and out of causal contact.
systemd is Roko's Basilisk.
Nope, there are already physics that allow for FTL travel in the same way that the universe is expanding (at a large distance from us) faster than the speed of light.
You can't travel FTL in a local frame of reference, but theres nothing that says space can't be manipulated FTL and there are plenty of theories that it in fact does expand FTL. The big bang being a shining example of space expanding far FTL ... or its wrong, the big bang theory that is.
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Oh by the way, did you notice, that she said matter is moving away faster than the speed of light, which is bullshit.
Speed of light only applies to *propagation* thru space. Expansion of space itself or other "superluminal" activity such as waving a laser pointer around in the air are not constrained by the speed of light.
Then while they're moving away faster than the speed of light, we know they're doing it because they're sending light back our direction at the speed of light and it's getting here, which is bullshit.
All the while light is propagating to you space is expanding for all of that time. If it takes light billions of years to reach earth in that time the distance and relative velocities has increased dramatically. This is why we are able to make observations well outside of our hubble sphere.
Seriously? I stopped reading the article when I got to the following text:
If something is receding from us right now at more than 299,792.458 km/s—faster than light speed—and it’s accelerating too, how could anything reach it? Even a photon, moving at the speed of light, wouldn’t be able to reach such a galaxy. Instead, anything beyond that point will do something that cosmologists call red out, which means they’re sufficiently redshifted that anything we do today could never, ever reach them, and only the light they emitted in the past will ever reach us. We are already causally disconnected from them.
This author obviously lacks the knowledge ladled out daily by the SyFy channel and internet on faster-than-light (FTL) drives and wormhole technology!
If one planet is traveling at .51c and another planet is traveling the exact opposite direction at .51c then the two planets are separating at faster then the speed of light.
No dice, simple vector addition only provides useful answers for small relative velocities. At relativistic velocities you must include Lorentz transform or your answer will be uselessly wrong.
Of course they're unreachable now
They cancelled Stargate Universe.
The time for light might be zero in its own frame of reference, but of course no object with rest mass could ever reach the speed of light.
Some theories for the end of the universe say that if the expansion of the universe keeps accelerating, eventually the expansion even between subatomic particles will be greater than the speed of light and everything will be ripped apart. This is long long after the skies are black because all objects and space have moved too far away.
We would have found [FTL travel] by now if someone has discovered it in the future.
That assumes future sapient species would be willing to share their time travel tips. Would you let a chimpanzee be in charge of launching a Saturn V rocket?
I don't mean to pick nits, but if you were a massless particle, you would already be moving at the speed of light.
No, they aren't. Space is expanding at a rate greater than c. Objects are not moving "through" space at a space greater than c.
Imagine 2 dots on a balloon as you blow it up. Those dots increase in distance from each other. The faster you inflate it, the faster they "move" away from each other.
Same thing here, only in 3 dimensions, and the "balloon" is being inflated at a faster and faster rate.
On another note, this is your 3rd or 4th post describing the article and science as "bullshit". Why do you continue to belittle a subject that you obviously know very little about?
Dude, if we're ever in Denver together I would like to smoke weed with you.
More music, fewer hits
For some purposes, you need a lot less time than that. See for instance http://arxiv.org/abs/1011.2646
60000ly/day, or 0.7ly/s. That is the speed you're measuring inside the spaceship of course. On Earth it will be difficult to measure that you are not actually going at lightspeed.
If you only care about your own reference frame you can pretty much throw relativity out the window, everything works the way it would in Newtonian physics.
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Quick, somebody call The Doctor.
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From its perspective a photon doesn't even travel.
Time an distance are different facets of the same thing.
Also, reality travels no faster then the speed of light.
https://www.youtube.com/watch?...
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Whether math is a product of the physical world or exists independently is a topic for another time. Either way, math cannot stop you from doing anything, you can just pick appropriate axioms which allow you to do what you want. Physics is less forgiving.
Admittedly, the acceleration required to get to the Milky Way centre and back in a day is somewhere beyond 100 billion g, and the power required is more than the output of the Sun, under the assumption that fuel does not have to be carried on the trip. It is a bit optimistic.
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Even so, it's perfectly possible that a photon would never be able to catch up with a galaxy leaving at a speed asymptotically going to c, so you could account for this without having FTL space expansion. I don't know if this is completely compatible with the observations, but I've noticed that, with relativity, you can approach a problem in different ways, do different kinds of calculations, and get the same results.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
"Nope, there are already physics that allow for FTL travel in the same way that the universe is expanding (at a large distance from us) faster than the speed of light."
Nope, there is not.
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The poster belittles them because he knows so little about them.
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No, we can't. Gravity can.
Let me know when we can manipulate gravity. AT that point we STILL won't go faster then light.
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Yup. When we get to physics, we get into questions of how do you accelerate that fast. I make it about five billion Gs, but I could easily have moved a decimal point wrong.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
Ship time: Just calculate it like it was Newtonian physics. You'll get the right answer.
Earth time: The ship will spend most of its 2.5 million light-years traveling so close to light speed that it really makes no difference for an Earth observer, so figure 2.5 million years. You'll have to supply a lot more decimal places to distinguish the travel time from speed-of-light time.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
I agree with you except I would quibble a small point. "As you approach the speed of light ..." time would not slow for YOU. It would (apparently) slow for those in another reference frame.
My references (I admit I don't have first-hand expertise in this area) suggest that photons become phonons in a medium and, upon exit from the medium, turn back into photons.
Regarding that idea, baseball bin beddy beddy gudt to me.
It little behooves the best of us to comment on the rest of us.
Also, incidentally, dots that start out on the balloon further apart from each other will move apart faster than dots that started out closer to each other, regardless of inflation rate.
File under 'M' for 'Manic ranting'
Yes, obviously while traveling the 13+ billion light years space is gong to stretch and even without expansion the visible edge of the universe will be much further away and unreachable. I guess I should have been clearer that it is possible to travel the distance without going faster then c.
https://en.wikipedia.org/wiki/Inverted_totalitarianism
A show-stopper is the amount of energy required to get a ship to move at any relativistic speed. Look at the hardware the LHC has to have in order to accelerate protons to near light speed. A proton, because it has mass, cannot reach the speed of light. There just isn't enough energy in the universe to do the job. A caveat: That limitation is based on the theories we have now.
It little behooves the best of us to comment on the rest of us.
Actually, wormholes break the Bianchi identities that are inherent in geometry. Wormholes are also mathematically equivalent to the existence of exotic matter - which would violate conservation laws.
Michael J. Burns
I propose building an engine which sucks in another universe from another dimension to burn as fuel. Though there may be ethical implications when using inhabited universes.
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We don't know. The universe could even be infinitely large. But it is almost certainly much bigger than what we can see. Estimates range from 250x bigger to 10^23 times bigger.
http://www.technologyreview.co...
Most of that stuff disappeared from sight almost right away, right after the big bang, long before galaxies even formed.
It's just like saying "the speed of a shadow is infinite"
As I envision it, it will take the form of a gradual redshift down to absolute zero. Stars and galaxies' lives and deaths and rebirths will be coming to us in an indefinitely- slowing-to-a-crawl slow-motion display of unbearable length... and it'll never quite go 'black' as much as fade away asymptotically forever in slowness and cold. Much like an avatar of the universe's entropic death, converging in on us from everywhere at once.
Man, this *is* depressing.
Maybe we deserve this world ?
You can travel the distance, but by the time you get there, that galaxy will be much further away. You'll never catch up with it.
Man, this *is* depressing.
Cheer up. It's Friday tomorrow.
systemd is Roko's Basilisk.
Either way, if you went there, I'd have to wait 5 million years for you to get back.
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Yes, but this is a physics article and not a science fiction one so there is both a speed limit and no Wookies available.
That's not to say the speed of light could not be exceeded by a hitherto unknown method. No Wookies required, but I don't think they are known as masters of FTL or anything anyway so that does not make sense.
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Only space between things get bigger not the things themselves
Rutherford's gold foil experiment showed that things ARE space between things. At least as far as getting bigger is concerned.
Bingo Dictionary - Pragmatist, n. A myopic idealist.
we didnt even leave our spec of dust (in a sustained way), let alone our solar system or universe.
That could be a bad thing. Conservation laws (all of them) tell us that, essentially, we would be importing one universe into another. Besides, we'd need an environmental impact study.
It little behooves the best of us to comment on the rest of us.
If there is a convenient nearby conservation law/premise/nightmare,
we can assume/deduce/panic -- the few remaining terrors are getting much more terrifying.
Nighty night, and pleasant dreams.
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If we limit ourselves to present technology yes its impossible. To say "even if we go at c" is silly too... because if we travel at c, we essentially will die from relativistic effects. But using simple general relativity, FTL travel and time travel seem very likely if not certain to a future civilization and I am sure more technologies will be discovered that will let us travel instantly to other galaxies in new and innovative ways. To say they are out of reach, is good in a way, as it will force thinkers to develop these essential technologies. We already have the equations and physical laws for wormholes... they are far from imaginary for any serious student of relatvistic fluid mechanics. What interests me is what happens when we time travel not if it is possible.
http://www.daviddarling.info/e... or http://en.wikipedia.org/wiki/A...
as well as the old standby Einstein-Rosen bridge: http://en.wikipedia.org/wiki/W...
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To be fair, there really are solid scientific hypotheses that are consistent with known physical laws that allow time travel -- it's just we have no reason to believe these physics are more real than the simpler alternatives which don't allow time travel, other than wishful thinking.
Examples:
http://physics.about.com/od/ti...
http://en.wikipedia.org/wiki/W...
From the Wikipedia article:
The theory of general relativity predicts that if traversable wormholes exist, they could allow time travel.
The two keys here are:
1. Traversible wormholes are not proven to exist or be possible (this requires matter with a negative energy density, also not proven to exist).
2. The assumption that general relativity remains a sufficient description of reality in the close vicinity of something so exotic as a traversable wormhole. Wikipedia mentions this by going on to mention quantum effects ruining the wormhole a couple paragraphs later.
Send a bunch of entangled matter out by slow ship every direction. Fix openssl. Then since the entangled matter will have by then reached everywhere just step across instantly. There are scientifically meaningless questions about soul data density though.
Impact the environment hard enough and there'll be nothing left large enough to bother looking at.
EIS complete ; attached above.
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