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**Kuciwalker** · August 12, 2005, 15:10

KrazyHorse pwns everyone else who replied to this thread

**Winston** · August 12, 2005, 15:19

Not me. And I wasn't even as longwinded about it as him.

**Al B. Sure!** · August 12, 2005, 20:59

KH:

but how can we be witnessing quasars at the edge of the universe as they were 14 billion years ago unless the matter in the universe expanded faster than light? I understand that this isn't the case of expansion like an object expands if it has more and more stuff entering it and filling it. I understand it's more like the inflation of a balloon. If one were to mark points on an un-inflated balloon then fill it with air, the points and the distance between them would stretch so the relative size of the points and the length of the distance between them would remain the same though the balloon (or the universe) would be quite bigger... so in that case, I understand that quasars 14 billion light years away can be 14 billion years old. but wouldn't the light that they reflected 14 billion years ago (when the absolute size of the universe was smaller, though the relative size remained the same) have reached us much sooner? either the universe inflated faster than light or light travelled more slowly in the past.

am i wrong?

**Odin** · August 12, 2005, 21:03

Most cosmologists beleive that the universe is flat (that is, it conforms to Euclidian geometry. A closed Universe is like the surface of a sphere, but in 3 dimensions; if you go straight in the same direction you will come back to where you started, like a Great Circle route on Earth. An open universe is usually called "saddle shaped," but in reality is hard to show. Closed universes are spherical, like the surface of the earth, finite but no having no "edge". Flat and open universes are infinite.

**reds4ever** · August 12, 2005, 21:05

Albert,

..or the light waves are stretched as the 'balloon' expands, and so take longer to reach us? Then we have red-shifted quasars.

..er, or not..?

**Al B. Sure!** · August 12, 2005, 21:06

Saras:

I only spent one year at Vilnius Uni Physics department, later changed my mind and transferred to the next building, business school. Real science to BS, really. I should go back some day.

no kidding. I'm a business student myself though I don't know what I want to do specifically (finance? marketing? accounting? management? economics? business law?)... sometimes I think i would make a better choice if i just chose some major in the social sciences, became a professor and try to be some sort of polymath... but there's not as much potential money in that as in business...

**Al B. Sure!** · August 12, 2005, 21:28

reds:

or the light waves are stretched as the 'balloon' expands, and so take longer to reach us? Then we have red-shifted quasars.

why would it take longer now? if it took less time in the past than the light would have reached us much sooner than today. light must have increased in speed.

i just don't understand how we could look at the edge of the universe and the light that reaches us reflected off the radiation 14 billion years ago at the dawn of the universe. If the universe expanded at the speed of light then it should take 28 billion years for us to see this radiation at the edge of the universe. 14 billion years to get out that far and 14 for the light to come back to us. there's a couple ways of looking at this but all seem to involve the speed of light changing or the universe expanding faster than light.

**reds4ever** · August 12, 2005, 22:44

Bear with me here Albert as I'm pretty much in the same boat as you, but if the 'universe' is expanding then light emitted from a source (say) 13 billion light years away will have to travel further than that to reach us, no matter how fast the expansion is.

I don't see how that needs the speed of light to change or for the universe to be expanding faster than light? It only needs the expansion of the universe to affect the light that is being emitted. The light is slowed down (or has to travel further) because of the expansion.

**Jon Shafer** · August 12, 2005, 23:22

Re: Re: Re: Re: Questions about astrophysics...

Originally posted by KrazyHorse
timeflow becomes imaginary

Okay, does this statement as a concrete scientific assertion freak anyone else out besides me?

**Joseph** · August 13, 2005, 01:26

Re: Re: Questions about astrophysics...

Originally posted by KrazyHorse

You can't go faster than the speed of light. Period. Any speculation on what would happen if you could is just so much silliness.

Then what about the partial that was shot at L. Livermore Lab a few years ago that did go faster then light speed?

So you are saying that Star Trek will never happen?

**KrazyHorse** · August 13, 2005, 01:51

Originally posted by Albert Speer
am i wrong?

Yes. There's no "simple" explanation for this. You need to simply learn GR and work out the geodesics (paths that light takes) on a robertson-walker metric (standard big bang metric)

These will demonstrate the needed properties without necessitating expansion at faster than the speed of light.

**KrazyHorse** · August 13, 2005, 01:54

Re: Re: Re: Re: Re: Questions about astrophysics...

Originally posted by Trip

Okay, does this statement as a concrete scientific assertion freak anyone else out besides me?

I deliberately stated that there is no suggestion that we can force objects to travel faster than the speed of light (there are very go0d phyiscal rasongs why we cannot). I was merely pointing out that a naive extrapolation of special relativity to this regime suggests imaginary timeflow (not negative timeflow).

**KrazyHorse** · August 13, 2005, 01:56

Re: Re: Re: Questions about astrophysics...

Originally posted by Joseph
Then what about the partial that was shot at L. Livermore Lab a few years ago that did go faster then light speed?

Never happened. You're completely wrong.

So you are saying that Star Trek will never happen?

No, I'm saying that given current physical theories we cannot exptrapolate what will happen. We have no data points. Also, guven current physical theorsies travelling faster than the speed of light is impossible. This doesn;t mean that it can never happen, simply that we dont; understand how to make it happen or the likely consequences if we did.

**Winston** · August 13, 2005, 02:05

KH, I have to hand it to you, your posts on this subject are even more impressive when you've assumed the Steady State for a late Friday night.

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Questions about astrophysics...

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