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Author Topic:   Size of the universe
Iblis
Member (Idle past 4005 days)
Posts: 663
Joined: 11-17-2005


Message 71 of 248 (598529)
12-31-2010 9:14 PM
Reply to: Message 69 by cavediver
12-30-2010 11:12 AM


Re: Young or old universe
quote:
The Observable Universe ended up with a radius of about *10cm* following inflation
Can you give more info on this, or point me to some? The last time I walked through this, the earliest figure after inflation I have for the OU is 3-5 billion light years. This ten centimeters is making me horny for some book larnin again.
Phillip's still profoundly wrong, regardless. But that shouldn't keep us from getting something out of this conv should it?

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 Message 69 by cavediver, posted 12-30-2010 11:12 AM cavediver has replied

Replies to this message:
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Iblis
Member (Idle past 4005 days)
Posts: 663
Joined: 11-17-2005


(1)
Message 76 of 248 (598670)
01-01-2011 6:37 PM
Reply to: Message 75 by Philip Johnson
01-01-2011 6:26 PM


Re: Young or old universe
Are you of the opinion that nothing can go faster than the speed of light? Is the radius of the universe increasing by at most 1 light year every year since nothing can go faster than the speed of light?
This is a fairly common misperception. The expansion of space, both the current version including "dark energy" and the inflation version, is not limited by C because it is a change in the nature of spacetime and not a movement of objects inside spacetime. The most distant objects are not receding faster than the speed of light because they are in motion, but rather because the space between us and them is increasing relatively uniformly.
You may imagine a rubber band if you like. When we stretch it to twice its size, marks on it which were two inches apart are now 4 inches apart. But marks which were a foot apart are now two feet apart. Thus the further away an object is, the faster it is receding. But its not moving relative to spacetime at all. So C doesn't apply.
One easy way to think of it is to understand that space literally is nothing. And thus we see that nothing can move faster than light!

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Iblis
Member (Idle past 4005 days)
Posts: 663
Joined: 11-17-2005


Message 84 of 248 (599349)
01-06-2011 4:09 PM
Reply to: Message 82 by Dogmafood
01-05-2011 8:43 PM


Re: Young or old universe
Is the nature of the universe, on a universal scale, fundamentally different from what I see around me?
Yep, that's it.
Spacetime, as it turns out, is a "field", or better yet, an arrangement or "manifold" of "fields". What we call matter and energy, and some other stuff, are actually just "waves" or "disturbances" or "indentations" of these "fields".
I'm putting all these words in quotes in order to emphasize that they don't even mean what they normally mean in spoken language, they are just chosen as the most useful exemplifications of the stuff the math seems to be saying. To be overly dull, the "fields" aren't meadows, the "waves" are very little like water or even sound, even the "particles" aren't little parts at all, at all.
For this same reason, I may have some portion of this explanation "wrong", but I am not overly concerned about that, because even the best explanation that cavediver coughs over here in a bit will only be "more representative", not really truly "right".
We are abusing English, in other words; the proper language is mathematics.

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Iblis
Member (Idle past 4005 days)
Posts: 663
Joined: 11-17-2005


Message 92 of 248 (600078)
01-12-2011 11:03 AM
Reply to: Message 89 by john6zx
01-12-2011 12:17 AM


begging the question
So what are the physical properities of space?
The capacity to act as a medium for matter and energy; curvature, as in expansion and gravitation; and vacuum energy in particular is purely a physical property of spacetime itself.
The fact that this stuff doesn't make sense to you, or fit into your philosophy, has no bearing on its accuracy. Relativity is one of the most thoroughly tested bodies of theory in all of science. If the terms of the mathematical model were less accurate than the piddly bit of "common sense" your brain can produce, any number of those experiments would have failed miserably. The only point where relativity seems to need some work is in describing the very, very small.

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