# Time vs Light question

1. Jan 1, 2004

### What Do I Know?

alrighty brainiacs... I love all this stuff but I'm still a newbie. I was watching a show on the Science Channel which stated that our Universe is not only expanding, but accelerating infinitely. Old news, I know. So, a question popped into my head. Maybe this is simple and I just don't get it. Hope I can explain it.

okay.. here goes..

If the Universe (space-time) is accelerating infinitely, what happens when the speed of space-time itself reaches the speed of light, which is in theory the fastest thing going?

Does everything go haywire and start a new big bang? Or can the speed of accelerating space-time actually reach the speed of light at all?

- Joe

:: question also posted on general Physics Board

2. Jan 1, 2004

### UltanByrne

Quick maybe not totally right answer b/c I don't have time to check sources right now

I really hope that this isn't true... certainly modern astronomy has shown the universe to be accelerating, but if something's rate of acceleration is infinite, wouldn't that mean that they are travelling at an infinite speed?

When space is expanding at such a rate that light cannot propogate from one point to some other(ie: spacetime isn't moving faster than light but::: the distance between two objects is increasing too fast for light to travel between them) you basically have the exact same effect that is a major flaw of pre-inflation big bang theory. (The 'horizon problem' -> checkout this paper for some interesting reading: http://theory.ic.ac.uk/~magueijo/rev.pdf [Broken] )

So I don't think everything goes haywire or starts a new big bang or any of that, we can all remain calm knowing that the current expansion won't lead to any massive astronomical catastophes in the near future. The inflationary big bang model of Guth et al. used expansion of the type you are asking about to solve the horizon problem.

Sorry for any errors in this one, its past my bedtime [zz)]

Ultan

Last edited by a moderator: May 1, 2017
3. Jan 3, 2004

### The_Jayman

More food for thought; Did you know that the universe is now said to be "infinite and flat" due to recently accumulated data measuring the universe's CMB - or Cosmic Microwave Background (said to be the microwave "echo" of the Big Bang), the universe is said to be 13.7 billion years old, and is said to be comprised of %4 matter, %23 dark matter and %73 dark energy? Oh, and researchers now contend that the "Speed of Gravity" is roughly %95 of the "Speed of Light"? I found these facts to be quite interesting, I thought I'd share them.

4. Jan 3, 2004

### Stryker

I have forgotten where I have heard this information. And it may not be valid anymore, but for arguments sake, why not.

After calculating the universe size and expansion rate, it is estimated that at the edge of the universe it is expanding 40 million times faster than the speed of light.

5. Jan 5, 2004

### Kube

The expansion of the Universe leads to the seperation of galaxies. Like 2 dots on a sheet of rubber when you spread it out. What I can assume from this is that if hte Universe is expanding at 40 million times the speed of light, than the andromeda galaxy should be WAY off right about now...

Secondly, if the Universe were expanding at 40 million times the speed of light, light propogating from some distant star a few hundred billion light-years away would never reach us as the amount of space it has to travel to reach us is expanding faster.

6. Jan 11, 2004

### studentx

You are assuming the speed of light is constant evrywhere, but is it?

7. Jan 11, 2004

### fffbone

Ah, but it is.

8. Mar 9, 2004

### Grim

Time was created by man to quantify the change of matter around us

9. Mar 9, 2004

### modmans2ndcoming

universe is not flat

we can no more tell that the universe is flat or curved any more than a person from flat land can tell if the surface of a sphere is flat or curved.

10. Mar 18, 2004

### Hyperbolic

11. Mar 31, 2004

### Jimbroni

Which Researchers were these? Speed of Gravity? There is no such thing.
Gravity is aceleration/deceleration, a force which can cause objects to have speed.

12. Mar 31, 2004

### JesseBonin

this is an amusing thread, i see so far more than a few schools of thought and the common arguments between them.

lets start our OWN school of thought here. let give the speed of light (c) a value of 0 (zero) and lets move on from there. why 0? to make light speed a non-issue. AND we can measure light speed by our own frame of referance, but there is no proof that the photon activated at point a is the same photon that reaces point b. therefor light speed could simply be the result of forces acting on one end of a photon mass and producing results at the other end.

now, how does this apply to the original question? if light speed is 0 then we are already well beyond the speed of light, and therefor know the results of super-luminal expansion 8)