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Author Topic: How did the finite Universe expand to become infinite?  (Read 2690 times)

Offline thedoc

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Peggy Hughes asked the Naked Scientists:
   
If I understand the big bang theory and inflation, the universe started out smaller than an atom. Then, during inflation, in a tiny fraction of a second, it expanded wildly to the size of a grapefruit. (That doesn't sound impressive to me but I think I cannot appreciate the order of magnitudes involved here!) These sizes seem finite to me yet the universe is infinite. When did it go from one to the other? Or can something so "small" still be infinite?

What do you think?
« Last Edit: 13/04/2014 22:30:01 by _system »


 

Offline JP

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Re: How did the finite Universe expand to become infinite?
« Reply #1 on: 14/04/2014 17:33:29 »
I think you've been misinformed on this one, Peggy.  If the universe is infinite, then the tiny patch, smaller than an atom, was the observable universe--meaning the bit we could see if we were at the center of that patch, due to the finite speed of light.  There was still stuff (an infinite amount of it) outside that patch, but the light from it hadn't reached us yet. 

As the universe expands, it is the size of this region that changes, but whatever's beyond it could be finite or it could be infinite--we're not sure.
 

Offline yor_on

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Re: How did the finite Universe expand to become infinite?
« Reply #2 on: 17/04/2014 19:55:22 »
I don't know. Depends on how you define it. There is no center to this universe, that we know of at least. Turn it around and every point is a center for this 'inflation' and subsequent 'expansion'. Thinking of it this way it's still going on, in every point.
 

Offline yor_on

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Re: How did the finite Universe expand to become infinite?
« Reply #3 on: 28/04/2014 18:39:36 »
There might be another thing. Think of how water becomes ice over a sea, it's not defined to a center of this sea, but to a 'nucleation' happening over its whole sea surface, dependent on temperature. You can also think of it as a result of a infinite amount of 'nuclear centers' connecting to each other creating a ice covering that sea.

If we ignore whatever limits to this 'sea', instead focusing on the idea of something happening, creating a definable volume, then this 'nucleation' has no center. And that is consistent with the idea of the accelerating expansion too.
=

the real problem with inflation, and expansion, isn't why it doesn't have a 'center' though. The real question is where it gets the allowance for doing it. Is it 'energy'? From where, if so? Our four 'dimensions' define a SpaceTime, and SpaceTime is defined as only existing, as being measurable, from a inside. So, where does this 'energy' come from? And the idea of a 'energy' is also relative the ideas you have/define of a vacuum, as consisting of 'energy', or not?
« Last Edit: 28/04/2014 18:48:25 by yor_on »
 

Offline yor_on

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Re: How did the finite Universe expand to become infinite?
« Reply #4 on: 28/04/2014 18:58:10 »
One way to define it would be from an idea of 'energy' being what exist. Also define it such as energy by itself have no dimensions. Dimensions won't come into play until we get nucleations, them connecting into measurable (as defined inside) dimensions. That way we can use the idea of sea ice, and what we find to be our limits astronomically. And then it should not matter how you want to define that universe from a thought up 'energy-outside'. Meaning that whatever geometry we give it, or find it to be, only will be valid inside it, depending on constants.
=

Defining it this way the question still is open whether a perfect vacuum is 'energy', or not as I think. The nucleation is what counts, and that is dependent on both a vacuum and 'rest mass'. Measuring something can never be a vacuum measuring on itself, it needs rest mass to measure with. And so defining it as a universe being able to be of any 'geometrical size and form' from a thought up outside, as measurable dimensions then should be a result from the nucleation, only definable from this inside we exist in.
==

You can also ask yourself whether a vacuum is gravity. Can a vacuum exist measurably without gravity? If you define gravity as not being a force, but just as a effect of SpaceTime orienting itself around matter, then, what is a vacuum? That one depends on many things, but the most important is how you look at it as a 'force' I think? Also about if you think a 'flat space' is a patch of vacuum, without the property of gravity existent in it
« Last Edit: 28/04/2014 19:35:12 by yor_on »
 

Offline AndyJohnDOU

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Re: How did the finite Universe expand to become infinite?
« Reply #5 on: 07/05/2014 14:57:49 »
one of the previous responses stated that there was no center of the universe
but is there a point about which it rotates?
like the earth rotates about the center of our solar system (sun)
our solar system rotates about center of the milky way etc...
 

Offline Bill S

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Re: How did the finite Universe expand to become infinite?
« Reply #6 on: 07/05/2014 21:05:26 »
Relativity maintains that there is no “special” place in the Universe, and if it rotates, there must be a very special place.  However, Gould, Mazur and Chapline, had a lot to say about the “Spinning Cosmos” a few decades ago, and made a good case for it.  I think very few people take it very seriously, possibly because it means coming to terms with the idea that the cosmos might be a superfluid; or that we might be on the inside of a “gravastar”. 

A while ago I read that someone was investigating a suspected directionality in the CMB temperature variations, which could be significant, but I don’t remember where I read it.
 

Offline AndyJohnDOU

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Re: How did the finite Universe expand to become infinite?
« Reply #7 on: 07/05/2014 23:23:54 »
thanks for your reply
I had watched Richard Feynman - The Character of Physical Law - 1 - The Law of Gravitation on youtube
I think I will go away and try and understand what you said
 

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Re: How did the finite Universe expand to become infinite?
« Reply #7 on: 07/05/2014 23:23:54 »

 

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