universe , empty space , vacuum, what is expanding ?

Question

When astronomes are talking about the universe that expands, exactly what is expanding then ? Is it the space that is expanding ? do they mean that as matter / energy travels through empty space this fill the empty space and this is what is called the expanding ?

I had the idea that it was space that is expanding, just plain empty space. but when i read this :

http://answers.yahoo.com/question/index;_ylt=AmJ6fC0JHEotKoe0uozPmSMjzKIX?qid=20060815214242AAr3NuL

i have the impresssion that it is not because there is an infinite vacuum that is not expanding, and it are the traveling particles that is called the expanding.

So what is it expanding, what expands ?

Answer 1

According to general relativity, it is space itself that expands. Unfortunately, generalrelativity and quantum mechanics have not be reconciled into one overarching theory. In quantum mechanics, a pure vacuum is a high energy state that could 'decay' into a state with matter than would form the basis of the big bang. But when I say 'could', it depends on exactly how gravity and quantum mechanics are brought together. In some versions,the singularity at the Big Bang is 'rounded out' because of quantum effects and there actually is a time before the Big Bang. In others, the singularity remains and there is not time before the Big Bang.

In any scenario, space itself is expanding. It is not simply particles moving through space like a conventional explosion.

Answer 2

You are right,expanding space as such makes no sense. Space is a quantum entity of minimum size and can't be divided or enlarged. If you take a highly compressed space it could expand to a degree,but only so far. After the first thirty-billionths of a second after the universe began,the density of space was unimaginable,it expanded radially becoming less dense. Matter emerged,then stars and us. The universe has the capacity to expand only so far then it must go out of existence. The farthest galaxies we see don't exist to-day,maybe 90% of them do not exist. They have retreated beyond the minimum density of space. Our galaxy will eventually meet the same fate. The reasoning beyond this is extensive but I'm sure it has some merit.

Answer 3

It is one of those things that is hard to wrap ones head around and makes a lot of people think that physics and cosmology is a lot of hooey.

The idea is tha space itself is expanding, but beyond the space in which the Universe exists is nothing, not even space.

One idea is that we can not see across the Universe completely because space is expanding faster than the speed of light at the outer edges, since space is not matter, it is not limited to the speed limit, so those objects that are on the edge are not actually moving. But if they are not moving, what about the Doppler effect.

It is weird.

Answer 4

Think of the universe as a balloon that is being blown up and the matter of our universe is the rubber of the balloon. What makes it expand? well that is the big question that physicists are trying to answer. Personally I think it is the gravitational pull from super massive black holes that are so far away that our technology hasn't been able to sense them yet. Also if something is very far away we won't be able to see them at all because of the inverse square law of light.

Answer 5

It's the other way round, they are collapsing, experts got it all wrong from the earth view.

Updates:
Remember the Physics RULE! by E=mc2.
Any matters that are compress, will tend to compress at comfort zone but it will expand when the compression beyond the comfort zone of the compression.
HA! ExpertS LOL!
Not happy, fine another e.g.
When water is compressed, the water will form the shape of compression but it will not tolerate when the compression of water goes beyond the limit of toleration. That's y we say that water cannot be compressed, Remember? LOL!
HAHAHAHAH thumb down no need to think lah...MUSt be from those world high pay yet useless people from Singapore!
LOL!
HAHAHA Expert just get your mthly high pay lah and stop making nonsense theory!
No happy there are many more e.g. too! to show off by me.

So what does bigbang theory mean to you?

Answer 6

Space-time itself is expanding. The vacuum is irrelevant.

Answer 7

it is not relevant what the universe is made of, or what is or is not in between starsystems.

because their moving, all stars have a shift in their spectrum (the color of the star.) If a star is moving towards us, it will be blueer if a star is moving away from us its redder.

when we look around us with telescopes, we only see red stars, conclusion, everything we see is moving away from us. if everything we see is moving away from us, that means the distance between stars is increasing. this we call the expanding

there is however a large portion of the universe we cannot see. so theres no accounting for that portion of the universe.
for all we know, the universe is a constant size, and everything we see just happens to move away from us. for all we know, the universe is finite, and everything we see is movign away from us because that finite line is expanding.

the truth is we dont know for sure, all we know is that everything around us, is moving away from us.

Answer 8

The solar systems and galaxies are all moving away from all other parts. That is why when we look at the light spectrum it is shifted toward the red end.

Answer 9

I'll be back