Where is the universe expanding away from?

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Offline Cameron Watts

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Where is the universe expanding away from?
« on: 12/02/2011 11:30:03 »
Cameron Watts  asked the Naked Scientists:
Hello Chris and team

I have a question for either the Naked Scientist or Naked Astronomy
team that I would love to have an insight into.

Bearing in mind that since Hubble, we have been aware that the universe is expanding and that it seems to be expanding from one
particular point of space. Firstly, do we know where this point in the
universe is and secondly, can we see it? If so, what can we see at
this point now or is it too far away?

Thanks so much - newbielink:http://www.thenakedscientists.com/HTML/podcasts/ [nonactive], newbielink:http://www.thenakedscientists.com/HTML/podcasts/ [nonactive] when you fill in for the "up all night" show as well as the Naked Scientist podcasts.


Perth, Western Australia

What do you think?
« Last Edit: 12/02/2011 11:30:03 by _system »


Offline bardman

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Where is the universe expanding away from?
« Reply #1 on: 16/02/2011 21:49:08 »
It is true that since Hubble we have known the universe is expanding. The expansion is equal in all directions away from us, meaning that there is not one direction in the universe we can see that is expanding faster than the rest. The rate of expansion is proportional to the distance away from us, meaning that something twice as far is moving twice as fast away from us. This at first seems to make us the center of the universe. However, if you go to another point in space, the same effect would be observed. Thus, there is no known exact "center" of the universe, even if there is such a thing.

There are theories on possible shapes of the universe (having to do with the curvature of space). These suggest that there is no center, or spatially preferred point in space.


Offline Soul Surfer

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Where is the universe expanding away from?
« Reply #2 on: 23/02/2011 11:48:35 »
It is very true that although there is no specific point from which the universe expanded,  a fact that we are continually having to explain here,  however there is a "fixed" frame of reference within our universe (at this epoch) that we (and everyone else) can measure their velocity with respect to.  That is the cosmic microwave background.  Our sun is currently moving at about 350Km/second with respect to this.  This is a true measure of velocity with respect to a general frame of reference and provides a rest frame throughout the universe.  Most other stars and galaxies would measure themselves as moving at similar speeds say 0 to 1000 km/s with respect to this background.  This is well below the velocity of light at 300,000 Km/s

This can be considered as our "true" velocity through space and is independent of the expansion of space itself.
« Last Edit: 23/02/2011 11:50:19 by Soul Surfer »
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Offline wolfekeeper

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Where is the universe expanding away from?
« Reply #3 on: 23/02/2011 15:43:47 »
It's a bit like inflating a balloon.

If you lived trapped in the rubbery surface of the balloon, and could only move and look through the rubber, and not into the air, you would see every bit of the balloon getting bigger over time, and wonder which bit of the rubber was the centre of the rubber!

But of course, the centre isn't in the rubber.

It's thought that the universe is like that, except the universe is not only the 2 dimensions of the thin rubber of the balloon, the universe is expanding with its 3 dimensions, with the centre of the expansion in a fourth dimension; so that the universe is presumably what's called a 'hypersphere'.


Offline yor_on

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Where is the universe expanding away from?
« Reply #4 on: 27/02/2011 13:23:35 »
You could also think of it as SpaceTime 'expanding' as a concept, an idea with its own internal logic and definitions, into a mind sphere of possibilities. Like what really is is substance without structure, for us SpaceTime becomes our structure and with it we are introduced to a whole lot of definitions, like 'distance' and 'speed', matter and 'space'.

When we try to understand SpaceTime that is what we measure from. But SpaceTime as such is very much like a certain 'density' mixed in all other 'densities' existing. And what we find 'stretching out' and 'expanding' may very well just be a local expression, not fitting anywhere except inside SpaceTime. Just like your 'distances' shrinks with 'speed' and your 'time' changes according to your friends observing you.

It's a tricky subject SpaceTime, and somehow we seem like something floating at some level inside a larger solution of possibilities, with 'virtual particles' under us and the 'speed of light in a vacuum' over us, if you see my drift :)

All what we think true is local expressions, found through observation and experience. We can't do anything less than we do, trying to fit them to the universe we see. They change though, from Aristotle to Newton to Einstein to ..

And we change with them.
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