How does spacetime expand?

[mistermack]

According to the big bang theory, spacetime expanded from a tiny size, and is still expanding.

If spacetime comes in quantum parcels, how does it expand overall?
Are the quantum quantities expanding, or are new ones being added?

And am I expanding? Is the kilometre expanding? Is the light year expanding?

[Xamonas Chegwé]

Try doing some reading.

Brian Green - The Elegant Universe (if you want the string theory version)
Roger Penrose - The Road To Reality (if you really want ALL of the maths)
Brian Cox - Why Does E = MC2 (if you want to skip most of the hard stuff)

Or enroll in a cosmology course.

The short answer is that no-one knows and that there is no agreed version, just a lot of theories. The CMB (Cosmic Microwave Background) has shed some light on things, as have recent results in particle physics - but, they have only eliminated a few of the wilder guesses and thrown up more to replace them.

It's all good shit though - the universe is fucking big and very very fucking weird!

[Rum]

An image that helps me, even if it is an analogue rather than an exact model, is to think of an expanding balloon. In this image the universe is the surface of the balloon (not the interior). Imagine dots and circles drawn on the surface of the balloon which represent matter. Then inflate the balloon and visualise what happens on its surface. From the perspective of every 'dot' every other mark on the balloon is moving away from it. Your then have to translate that into three dimensions, plus time of course.

One thing I can't get my head around - well nobody seems to have yet - is the discovery recently that the expansion is accelerating.

[Atheist-Lite]

Space expands because there's more space being made by events accumulating. Because the average of all events is to cancel one another out only the newly formed space remains. And this is unevenly distrubuted over the cosmos(since events and the passage of time is always local, or close to local) thus the event called the 'space between between galaxies' is very large and so over time the space between galaxies shows a mathematical acceleration way faster than something like pouring milk into a cup of tea.

[JacksSmirkingRevenge]

So, what shape is the universe?
Blind intuition tells me that it should be spherical (don't ask why), but I've also heard that it's actually 'saddle' shaped. Has this view changed?

[Atheist-Lite]

So, what shape is the universe?
Blind intuition tells me that it should be spherical (don't ask why), but I've also heard that it's actually 'saddle' shaped. Has this view changed?

The universe doesn't get any larger than your imagination. It is shaped like that too. The only limitation is you will die.

[Pappa]

So, what shape is the universe?
Blind intuition tells me that it should be spherical (don't ask why), but I've also heard that it's actually 'saddle' shaped. Has this view changed?

That's not really to do with the shape of the universe, but the shape of the curvature of dimensions that we imagine to be flat. The view is changing all the time, mostly because cosmological theories are based on very incomplete evidence. Every new piece of evidence adds a very useful piece to the jigsaw though.

[Clinton Huxley]

I heard it was shaped like a horn

[Atheist-Lite]

I heard it was shaped like a horn

Doesn't modern econonmic theory posit the universe to be a tapered infinite pyramid made from greenbacks with a outer casing of gold and containing a infintie supply of oil within?

[Clinton Huxley]

Quoting Sean Carroll's From Here To Eternity...

When we say that space is expanding, we mean that more space is coming into existence between the galaxies. Galaxies themselves are not expanding, nor are you, nor are individual atoms; anything that is held together by some local forces will maintain its size, even in an expanding universe.......If the Universe is expanding, what is is expanding into? Nothing. When we're talking about the Universe, there's no need to invoke something for it to expand into, it'sthe Universe, it doesn't need to be ebedded in anything else.....Likewise, there doesn't need to be an edge, the Universe could just continue on infinitely far in space. Or for that matter it could be finite, by wrapping back on itself.....there is a good reason to believe we will never know....

[JacksSmirkingRevenge]

So, what shape is the universe?
Blind intuition tells me that it should be spherical (don't ask why), but I've also heard that it's actually 'saddle' shaped. Has this view changed?

That's not really to do with the shape of the universe, but the shape of the curvature of dimensions that we imagine to be flat. The view is changing all the time, mostly because cosmological theories are based on very incomplete evidence. Every new piece of evidence adds a very useful piece to the jigsaw though.

You mean due to gravity?
I looked all this up on Wikipedia earlier and couldn't understand a bloody word of it...I think I'll just have to concede defeat when it comes to understanding any of this stuff - I just can't get my head around it...ergo, GOD DID IT!!

[PsychoSerenity]

Quoting Sean Carroll's From Here To Eternity...

When we say that space is expanding, we mean that more space is coming into existence between the galaxies. Galaxies themselves are not expanding, nor are you, nor are individual atoms; anything that is held together by some local forces will maintain its size, even in an expanding universe.......If the Universe is expanding, what is is expanding into? Nothing. When we're talking about the Universe, there's no need to invoke something for it to expand into, it'sthe Universe, it doesn't need to be ebedded in anything else.....Likewise, there doesn't need to be an edge, the Universe could just continue on infinitely far in space. Or for that matter it could be finite, by wrapping back on itself.....there is a good reason to believe we will never know....

Well what the fuck does that mean?!

I've heard two different explanations concerning red-shift. One says that as the light is travelling through space, it actually gets stretched with the expansion of the universe. The other says that the galaxies are simply moving through space away from each other, and the ones further away are moving faster away, and the speed difference causes the shift.

Are either of these right or wrong? Or are they equivalent models?

[Clinton Huxley]

Quoting Sean Carroll's From Here To Eternity...

When we say that space is expanding, we mean that more space is coming into existence between the galaxies. Galaxies themselves are not expanding, nor are you, nor are individual atoms; anything that is held together by some local forces will maintain its size, even in an expanding universe.......If the Universe is expanding, what is is expanding into? Nothing. When we're talking about the Universe, there's no need to invoke something for it to expand into, it'sthe Universe, it doesn't need to be ebedded in anything else.....Likewise, there doesn't need to be an edge, the Universe could just continue on infinitely far in space. Or for that matter it could be finite, by wrapping back on itself.....there is a good reason to believe we will never know....

Well what the fuck does that mean?!

I've heard two different explanations concerning red-shift. One says that as the light is travelling through space, it actually gets stretched with the expansion of the universe. The other says that the galaxies are simply moving through space away from each other, and the ones further away are moving faster away, and the speed difference causes the shift.

Are either of these right or wrong? Or are they equivalent models?

I take it to mean that space itself, the space between galaxies, is inflating. Something to do with zero-point energy?

[PsychoSerenity]

I take it to mean that space itself, the space between galaxies, is inflating. Something to do with zero-point energy?

Ohh zero-point energy. I've heard of that off Stargate. Now it all makes sense.

[Clinton Huxley]

I take it to mean that space itself, the space between galaxies, is inflating. Something to do with zero-point energy?

Ohh zero-point energy. I've heard of that off Stargate. Now it all makes sense.

And I believe Dr Who might have explained something about inflation.....