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What happens to light at the end of the universe?
- Thread starter Smoblikat
- Start date
videogames101
Diamond Member
It's my understanding that the universe is expanding at c, so light would never reach "the edge".
Also, I'm not quite sure what you mean by saying gravity is "faster" than light, because changes in gravitational fields propagate at c.
Also, I'm not quite sure what you mean by saying gravity is "faster" than light, because changes in gravitational fields propagate at c.
Let's assume that you could travel infinitely fast... This means that you COULD go fast enough to reach the edge of the universe. You would eventually wind up back where you started. It is similar of you leave your house and go due north. Eventually, you would hit the north pole and start heading south - to the south pole, and then right back where you started.
The universe is believed to be "isotropic" which means that it looks pretty much the same everywhere. No center, no edge.
Yes, it hurts your head if you think about it too hard, but you eventually get over it and just accept it.
The universe is believed to be "isotropic" which means that it looks pretty much the same everywhere. No center, no edge.
Yes, it hurts your head if you think about it too hard, but you eventually get over it and just accept it.
pandemonium
Golden Member
I do need to point out that gravity does not move faster than light; it simply overpowers it, when in large enough quantities.
The "edge of the universe" is much like that of the "edge of the earth", it doesn't exist in our traditional terms. It's simply the limits of our understanding and instruments on how to perceive the concept.
This paragraph on wiki fairly accurately describes what I'm saying:
The inherent issue discussing the observable edge of the universe, is that it can't be done without a little philosophical angle as well as scientific. Within our most widely accepted theory of cosmology, space-time basically overlaps in on itself at the edge, forming a large "bubble". The problem here is describing how to define 4 (or more) dimensions, and it's been done by many, far more intelligent than I. I'd recommend reading anything or watching anything from a prominent astrophysicist or theoretical astrophysicist. Brian Cox, for one, is pretty good for describing things at a level most people can grasp, as well as going into the fine details.
The main thing to remember is that observable is the key word.
To directly answer your question about what happens to light at the edge of the observable universe, is quite simply, that it doesn't happen. The universe is expanding and light is following right along with it, as well as everything else. There is no "border" or "edge" that anything is bouncing off of, per se. All of existence, light included, is expanding. And that is, for all intents and purposes, the universe.
The "edge of the universe" is much like that of the "edge of the earth", it doesn't exist in our traditional terms. It's simply the limits of our understanding and instruments on how to perceive the concept.
This paragraph on wiki fairly accurately describes what I'm saying:
The inherent issue discussing the observable edge of the universe, is that it can't be done without a little philosophical angle as well as scientific. Within our most widely accepted theory of cosmology, space-time basically overlaps in on itself at the edge, forming a large "bubble". The problem here is describing how to define 4 (or more) dimensions, and it's been done by many, far more intelligent than I. I'd recommend reading anything or watching anything from a prominent astrophysicist or theoretical astrophysicist. Brian Cox, for one, is pretty good for describing things at a level most people can grasp, as well as going into the fine details.
The main thing to remember is that observable is the key word.
To directly answer your question about what happens to light at the edge of the observable universe, is quite simply, that it doesn't happen. The universe is expanding and light is following right along with it, as well as everything else. There is no "border" or "edge" that anything is bouncing off of, per se. All of existence, light included, is expanding. And that is, for all intents and purposes, the universe.
Sunny129
Diamond Member
as other have mentioned already, the force of gravity does not propagate faster than the speed of light c. while Newtons laws of motion/mechanics provide an excellent approximation of Einstein's field equations in our non-relativistic setting here on earth and around the solar system in general, he was actually incorrect to assume that gravity was "instantaneous." according to Newton, if the sun were to suddenly vanish, the earth would instantaneously trail off tangentially. but this is not what would happen in reality - in reality, the earth would continue to orbit the location where the sun was for approx. 8.5 minutes, and then it would trail off tangentially. why? b/c it takes ~8.5 minutes for the sun's gravitational affects to reach earth at the speed of light from a distance of 93 million miles.
you're statement only holds true in a closed universe, or one with positive curvature. in this scenario, the approximate shape of the universe is spherical, which is why your analogy to the earth works. the problem w/ this is that its only an assumption - we don't know if the universe is closed (has positive curvature), flat (has zero curvature), or open (has negative curvature, in which case the approximate shape of the universe would be hyperbolic, or saddle-like). in a flat or open universe, one would never end up back where he/she started by following a geodesic.
jimmybgood9
Member
I think the most direct answer to the OPs question is that the edge of the universe is defined by the light emitted after the Big Bang. That light is at the edge of the universe and so the universe (at least that portion of the universe that is perceivable) just gets bigger as the light propagates.
If something is out there beyond, we would have no way of knowing about it, since there hasn't been enough time since the creation of the universe for the light (information about it) to get back to us.
This is not to be confused with the expansion of the universe, which is a space-time thing that I won't even pretend to understand.
If something is out there beyond, we would have no way of knowing about it, since there hasn't been enough time since the creation of the universe for the light (information about it) to get back to us.
This is not to be confused with the expansion of the universe, which is a space-time thing that I won't even pretend to understand.
trainman2001
Junior Member
Why isn't gravity instantaneous? If we assume gravity is a wave or particle, then it's not difficult to jump to the conclusion that it's held by the same speed limits of all other radiation...C. But, if it's simply the warping affect that mass has on space-time, why can it be instantaneous. The instant the mass exists, the warpage of space-time exists. It's part and parcel of mass. We really don't have a good grip on gravity at all. It defies the inverse square law and forces cosmologists to devise all kinds of weird contrivances such as multi-verses, membranes where gravitons can pass out of this universe into others where electromagnetic radiation cannot. The near impossibility of finding "gravitational waves" isn't helping matters either.
I am simply not intelligent enough to conceive of a Big Bang expanding basically nothing into an infinite something. My son guided me to this forum after I posed the question about light rays extending outward from the farthest things we can observe in this universe. The Hubble Deep Sky images showed that the farther we see the more aged are the galaxies and quasars. They become more amorphous and clearly less developed. The light from these objects extends out it all directions including directly away from our point of view. My question was "where's it going?" I don't know... that's why I asked it. It's nice to see that others ask the same question.
That it simply loops back on itself, doesn't ring true to me. As we look outward we're not seeing backwards, we see different objects. When the Webb telescope goes up, it too will take remarkable pictures showing even greater distances, but it won't show the end either. No end, no middle... hard to imagine.
I am simply not intelligent enough to conceive of a Big Bang expanding basically nothing into an infinite something. My son guided me to this forum after I posed the question about light rays extending outward from the farthest things we can observe in this universe. The Hubble Deep Sky images showed that the farther we see the more aged are the galaxies and quasars. They become more amorphous and clearly less developed. The light from these objects extends out it all directions including directly away from our point of view. My question was "where's it going?" I don't know... that's why I asked it. It's nice to see that others ask the same question.
That it simply loops back on itself, doesn't ring true to me. As we look outward we're not seeing backwards, we see different objects. When the Webb telescope goes up, it too will take remarkable pictures showing even greater distances, but it won't show the end either. No end, no middle... hard to imagine.
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I guess we'll know if it ever gets there ...
pandemonium
Golden Member
To directly explain how it works that we can't see the edge is due to the fact that it's expanding faster than light can travel. Thus the light from said event can't possibly reach our instruments from the edge. Light is our primary medium for all things observable. Since it has limits, we can't rely on it entirely to explain everything.
This is one area where quantum physics steps in to attempt an explanation as to why/how. (I'm not going to elaborate here; there's plenty of material all over regarding that subject around the net should anyone care to read up on it. A lot of it is more pseudo than science, but there are some definitive experiments leading us to believe there's a lot more to the universe than what Newton's modeling suggests, and even Einstein's).
When JWST goes up, it won't "see" much further than what Hubble or [more notably] WMAP or anything else has seen, because we're already reaching the limits of what optical observational data can provide for us. Light only travels so fast, so the only real way we're going to get accurate information on the "edge of the universe" is to be on the event horizon.
FTL technologies are our next major goal and will answer more questions than we can possibly fathom.
Biftheunderstudy
Senior member
There are number of correct things already stated in this thread, but a worrying number of incorrect or inaccurate statements as well. Allow me to try to collect some of the "correct as we know it" statements together:
1) Sunny129 has the way of it with the positive/flat/negative curvature statement. With a simple caveat, we think we know the answer. COBE, WMAP and recently Planck have confirmed that the universe is flat to very high precision. This means that space doesn't wrap around or anything like that.
2) Space is expanding at a rate which is faster than the speed of light. We can see this by observing distant galaxies "moving" away from us faster and faster. For clarification on what I mean by "moving" see the post about the expanding universe.
3) Our *observable* universe is defined by how far/distant we can see according to the speed of light. The universe in its entirety is unknown to us, possible forever. It's properties don't have to be anything like our observable one.
So, to answer the OP:
Gravity isn't faster than light, light can't reach the true border of the universe since it expanding away faster than the light can get there. More and more of the universe is being "uncovered" as time goes on.
1) Sunny129 has the way of it with the positive/flat/negative curvature statement. With a simple caveat, we think we know the answer. COBE, WMAP and recently Planck have confirmed that the universe is flat to very high precision. This means that space doesn't wrap around or anything like that.
2) Space is expanding at a rate which is faster than the speed of light. We can see this by observing distant galaxies "moving" away from us faster and faster. For clarification on what I mean by "moving" see the post about the expanding universe.
3) Our *observable* universe is defined by how far/distant we can see according to the speed of light. The universe in its entirety is unknown to us, possible forever. It's properties don't have to be anything like our observable one.
So, to answer the OP:
Gravity isn't faster than light, light can't reach the true border of the universe since it expanding away faster than the light can get there. More and more of the universe is being "uncovered" as time goes on.
disappoint
Lifer
As long as we're correcting things, I know you didn't mean to say: "Space is expanding at a rate which is faster than the speed of light." but rather: Space beyond the edge of our observable universe is expanding at >c.
SecurityTheatre
Senior member
Wait, what?
silverpig
Lifer
Yeah no the other guy was more correct.
We can see things that are "moving" away from us faster than c. It's not proper motion through space though, it's just that the space between us and though objects is growing faster than the speed of light.
Biftheunderstudy
Senior member
I suppose I probably could have been a bit more clear there.
Let me try that sentence again:
Space is expanding at a uniformly accelerated rate (in places where things aren't gravitationally bound, like our solar system or galaxy). The implications are that, relative to us, things move faster the farther away they are to us. The point is that things can be "carried away" faster than the speed of light. Relative to us.
A poor man's analogy is the dots on a baloon, or raisins in a loaf of bread.
Let me try that sentence again:
Space is expanding at a uniformly accelerated rate (in places where things aren't gravitationally bound, like our solar system or galaxy). The implications are that, relative to us, things move faster the farther away they are to us. The point is that things can be "carried away" faster than the speed of light. Relative to us.
A poor man's analogy is the dots on a baloon, or raisins in a loaf of bread.
The OP has a Good Question and is very Inquisitive.
Light in my Rehlem say instances between collisions of Matter denote Time. When there are no more collisions the candle simply burns out.
As Photons mark instances in time recording collisions of matter mapping what we we see as "Conscious Beings" will END.
GOD is Vane and His Horseman will weed it out.
Light in my Rehlem say instances between collisions of Matter denote Time. When there are no more collisions the candle simply burns out.
As Photons mark instances in time recording collisions of matter mapping what we we see as "Conscious Beings" will END.
GOD is Vane and His Horseman will weed it out.
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pauldun170
Diamond Member
Do not confuse the known, or observable universe with the "Universe"
The known universe is defined by what we can observe. The big bang is not the origin of the universe or a stage of some sort universal life cycle, it is the origin of what we have observed
There is no border to the universe. Light, or any other particle will travel until something puts some force on it.
Placed in the context of the known universe, where all boundaries are defined by our intellect a light particle will be observed traveling until we cannot prove its traveling. Then we say that..
Wait...too deep a conversation.
Leaving thread for alcohol
The known universe is defined by what we can observe. The big bang is not the origin of the universe or a stage of some sort universal life cycle, it is the origin of what we have observed
There is no border to the universe. Light, or any other particle will travel until something puts some force on it.
Placed in the context of the known universe, where all boundaries are defined by our intellect a light particle will be observed traveling until we cannot prove its traveling. Then we say that..
Wait...too deep a conversation.
Leaving thread for alcohol
Ventanni
Golden Member
I don't think there's a "boundary" to the universe much in the same way there's really any boundary to a star or galaxy. If we ever were to hypothetically make it to the absolute far reaches of the known, observable universe, we'd probably just see a drop-off in density of surrounding matter and galaxies until there was nothing left to see.
Which makes me wonder, if the big bang was the starting point of the creation of the currently known universe, would there be an enormous gap of nothing where the flashpoint started? Or are we just riding an enormous shockwave of matter so large it looks like a bubble from our perspective?
Either way, it's interesting that nothing can travel through spacetime faster than the speed of light, except for the expansion of spacetime itself. If that's the case, I wonder how long it'll take for us to figure out how to corkscrew ourselves through spacetime, and bam, we have our first FTL drive.
Which makes me wonder, if the big bang was the starting point of the creation of the currently known universe, would there be an enormous gap of nothing where the flashpoint started? Or are we just riding an enormous shockwave of matter so large it looks like a bubble from our perspective?
Either way, it's interesting that nothing can travel through spacetime faster than the speed of light, except for the expansion of spacetime itself. If that's the case, I wonder how long it'll take for us to figure out how to corkscrew ourselves through spacetime, and bam, we have our first FTL drive.
I agree with all your hypothesis but eventually the clock may just STOP and Conscious Life which observes is no longer existent. What's the purpose of a Universe with nothing to See It.
Our life is nothing but a spark in comparison to the age of our Solar System and insignificant within Space and Time - Unless we save this planet and ourselves, we can not even begin.
God with his Universe is looking for Praise - Let's Do It and journey to the End of Time.
Sish! Think I could do with another beer and tend my own - LOL
Our life is nothing but a spark in comparison to the age of our Solar System and insignificant within Space and Time - Unless we save this planet and ourselves, we can not even begin.
God with his Universe is looking for Praise - Let's Do It and journey to the End of Time.
Sish! Think I could do with another beer and tend my own - LOL
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actually wasnt it theorized if u could do what u stated, you would run into another identical earth in a different location of the universe... because the universe is so large that statistics works in you finding a exact duplicate of the earth in the entire universe.
So instead of going around... like a globe as u said... u would notice repeats, in which the things u saw were just repeats of where u were at, but not at the same location.
Here's a explanation of what makes sense to me...
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Very interesting discussion.
Without mixing philosophy with materialistic world and science, I did a back-of-the-envelop-calculation a while back to estimate the size (width) of that spark.
If I draw a line across many computer monitors kept side by side for about 7 miles or so, then each pixel represents 100 years. Total number of pixels in all those monitors would be the age of the universe. (not sure if my math was correct)
Without mixing philosophy with materialistic world and science, I did a back-of-the-envelop-calculation a while back to estimate the size (width) of that spark.
If I draw a line across many computer monitors kept side by side for about 7 miles or so, then each pixel represents 100 years. Total number of pixels in all those monitors would be the age of the universe. (not sure if my math was correct)
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