# heres a stumper...Question

Discussion in 'Physics & Math' started by HEXiT, Dec 11, 2011.

1. ### HEXiTRegistered Member

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most scientists agree that the universe is expanding at an accelerating rate,
and the general consensus is the speed of light is constant.
given that the universe may be infinite in space and time.
so to my mind it stands to reason that sooner or later universal expansion will reach the speed of light.
my question is what will happen? will this create another expansion?, creating a new big bang and universe to which our universe was the seed

3. ### EnmosValued Senior Member

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It's my understanding that the universe is already expanding faster than the speed of light, measured between two points in space.
But that does not require anything traveling faster than the speed of light though.
At each point in space, between say two galaxies, new space is being created.

5. ### HEXiTRegistered Member

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but nothing can move faster than the speed of light including the space light was traveling through...
or is that wrong...

7. ### Aqueous Idflat Earth skepticValued Senior Member

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Related questions:

What do you assume is infinite about space or time?

What is happening at the edge of the universe? What lies beyond the edge? What lies just inside?

One view is that the universe is enclosed by a spherical boundary which is the event horizon of the Big Bang. Then there is no "outside" and the "inside" is a region of convergence, an asymptote.

It would seem that an event horizon could recede at any rate, because it has already left the realm of reality where the laws of physics apply.

Now we are left to ponder whether there is a limit to the rate at which time and space can be created. That seems to take care of itself since there is no time at the moment spacetime is created. So there would not seem to be and restriction on rate, because there is no rate when there is no spacetime to measure it by.

8. ### EnmosValued Senior Member

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If you read carefully what I wrote you'll see that nothing needs to travel faster than the speed of light to have two galaxies drift apart with a speed greater than the speed of light.

Say the rule is that nothing can move faster than 100 mph.
Now two cars drive away from each other each at a speed of 80 mph.
How fast are they moving apart? Did the rule get violated?
Now imagine that the cars 'move' by the space expanding between them.

Last edited: Dec 11, 2011
9. ### HEXiTRegistered Member

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was the part i was refering to....

10. ### EnmosValued Senior Member

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Yes, the two points in space being the cars in my previous post.

11. ### Jim SRegistered Senior Member

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It might not be exactly true that nothing can move faster than light - tachyons are particles that can only move faster than light, never slower. The trouble with them is that they haven't found any yet, but they could exist. There are a lot of good science books that try to expain this stuff - it seems like the physics that work on the extremely small and the extremely large parts of our universe aren't the same as the laws that govern our everyday lives so just applying "common sense" to these things don't always work.
I'm reading "Journey to the Center of Our Galaxy" by Joel Davis now, and I would recommend it.
Actually, all us kids growing up in the 50's knew of something that go go faster than light - it was Silver!
(The Lone Ranger's horse)

12. ### Fudge MuffinFudge MuffinRegistered Senior Member

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Oh. So the universe could never expand faster than twice the speed of light?

13. ### prometheusviva voce!Registered Senior Member

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This is not quite the way it works. Lets take Enmos' example that the maximum possible speed c is 100 mph, and you have two cars travelling away from each other at 80mph relative to the ground. Special relativity tells us that if an observer in on of the cars was able to measure the speed of the other car he would see it travelling away from him at $v_{\mathrm{obs} }= \frac{u+ v}{1+\frac{uv}{c^2}}$ which in this example is $\frac{160}{1+\frac{640}{1000}} \approx 97.6 \mathrm{mph}$.

This is of course what happens in flat space, which is not what is being talked about here, but the point is still that an observer cannot move faster than the speed of light, but what we are calling "space" is not an observer. Let's think of another example: suppose I have a long pair of scissors, and I close them quickly. The blades of the scissors I could envisage sticking a little camera on, so they behave like observers and cannot move faster than c. The intersection point where one blade meets the other has no such restriction on it so it can move faster than c. This isn't problematic though, because nothing physical is going faster than c.

It is possible that the universe will expand at an ever increasing rate, and one may ask what that means for the "edge of the universe," but really that is something of a meaningless question to ask because it's not something we can observe. At the moment we are confined within the Hubble volume, which is effectively a sphere of radius the age of the universe times the speed of light. If the expansion of the universe accelerates, the Hubble volume will actually shrink, and eventually will be so small that matter will be blown apart by the expansion. This is called the big rip.

14. ### originHeading towards oblivionValued Senior Member

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Special relativity addressed objects moving through space, not space itself. Space can and is expanding faster than the speed of light (as measured by 2 points that are far enough apart). Anything that is farther than ~14 billion light years from earth will never be seen by us because it is receding from us at speed faster than c.

15. ### wlminexBannedBanned

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At each point in space, between say two galaxies, new space is being created.[/QUOTE]

I agree . . . . please re-read my explanation for this . . . . @ earlier Sciforum posts and also Google "EEMU Hypothesis" . . . for AlexG's and Prometheus's sake, I won't reiterate my explanation here!

16. ### HEXiTRegistered Member

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thanx for the input so far...
but i dont think you guys are understanding me.
by the time all the matter whether it be atoms or something smaller in the universe has been pushed to the speed of light by space itself pushing everything apart faster and faster...
basically all the matter thats left is forced to accelerate to the speed of light and basically come to a stop in relation to an adjacent photon not that theres likely to be 1 anywhere near it.

the big rip is an interesting idea.

17. ### AlexGLike nailing Jello to a treeValued Senior Member

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I think you've missed the distinction between matter traveling through space, and distance increasing because of the creation of new space. Nothing material is moving at the speed of light. Distance is being created faster than light can cross it.

18. ### EnmosValued Senior Member

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Thanks Prometheus, I know I wasn't being quite correct but I was keeping it simple so he could visualize what was going on. Also, I don't know a whole lot about this

The main point was that two points in space moving away from each other faster than the speed of light does not require any of the points to move faster then the speed of light. It seemed he was having trouble understanding that in particular.

19. ### Aqueous Idflat Earth skepticValued Senior Member

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For me the following questions remain:

(1) Where is space being created?

(2) When is it being created?

(3) What is "the end of space", which, even now, is extended -- by filling in some more space?

(4) Reconsider each of the above with the "concurrent" creation of time. What then?

20. ### OnlyMeValued Senior Member

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Prometheus, would not the two cars, whose individual velocities are each relative to the road, rather than each other, be the same as a closing speed, except opposite.

Closing speeds or velocities can exceed the speed of light while the objects both have velocities less the c. The same should be true for separating speeds or velocities.

You don't normally see discussions of separation velocities exceeding c, because as soon as the velocity of separation exceeds c, no information could be transmitted between the two objects. Where the situation involves closing speeds, there is no break in the transfer of information.

This has nothing to do with the expanding universe issue. Just a point of clarification, involving closing speeds.

21. ### Crunchy CatF-in' *meow* baby!!!Valued Senior Member

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^^^^ ding ding ding, correct :3.

22. ### Crunchy CatF-in' *meow* baby!!!Valued Senior Member

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In theory, everywhere (it's supposedly a symmetric expansion).

Right now.

I am not sure where you found the phrase. It may refer to the hubble volume, which is the maximim distance that humans are able to presently observe.

I am not sure what point you are trying to make, so reconsidering your questions within the context of time doesn't seem to matter.

23. ### HEXiTRegistered Member

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so no1 thinks that spacetime will become flat and collapse in on itself because all matter has become stationary in relation to all other matter even though they are moving relative to space.

ah well i guess i got some deep thoughts and muttering to do.