What is space?

If the glove that astronaut lost is still in orbit, yup, there's fabric up there alright.

 

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Who's 'we'?

Actually it would be objects moving relative to other objects.. and yes, they do move faster than light due to the 'expansion of space'. This has already been mentioned in this thread.

No new physics is needed to explain this.

Why?

 

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Do you want to change the definition of space?

 

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New Horizons is travelling towards the plutoids away from Earth but that doesn't mean space is expanding between it and the Earth. Are you suggesting we assume that space contracts when objects move together and expands when they move apart?

To explain what, God? I agree, we have religion for that.

Otherwise the total energy content within that hypothetical universe would decrease with time, as galaxies move to the Hubble horizon and vanish (where it is assumed nothing exists beyond the horizon).

 

Where you've assumed that "nothing exists beyond the horizon", unlike most cosmologists, then there is a problem conceptually with the decreasing density of matter and energy within the horizon (where we are, and can see that there are distant objects receding at nearly the speed of light).

If you simply assume that your assumption is incorrect (there is something beyond the visible horizon after all), the "problem" ceases to exist. Isn't logic a hoot?

 

If you would like to discuss the space between the Earth and 'New Horizons', then, if you'd like, you can say that the space is expanding... or you can say the distance is increasing. And I am not 'suggesting we assume' anything.

You know what I meant.

You sure like to assume things. Who has ever said that nothing exists beyond the 'hubble horizon'?

 

OK. The definition of the word space is changed. It's now some material object. Now we need a word for what space meant.
Marft - The infinite 3D area in which all matter exists.

 

Space...the distance between two divorced people!

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That was exactly my point (post 119, last paragraph - I'll edit it to make it more clear). I was not arguing that it is the case, I was stating that if that were the case (nothing exists beyond the horizon), then a problem would exist with energy conservation.

Which followed from my suggestion that if it were not space expanding then the objects beyond the horizon would violate the universal speed limit by moving away from us faster than light, through space (and the only way to fix that is to say they stop accelerating or they disappear - just to point out how 'strange' it would be).

Which was all started by losfomoT stating in response to one of my posts that

, because, IM2HIO - in my most humble and inexpert opinion - calling space "the distance between two objects" is simply too simplistic and leaves me spaced out.

 

My post about having to assume nothing exists beyond the horizon to fix the problem of speed limits (not energy conservation) should be edited now. That should make it more clear.

 

Is space unitary?

Is it fractal?

Seth Lloyd, a professor at MIT says (and he knows a bit of math, I guess), that unitarity implies a linear (monotonic?) norm-preserving transform.
Does space expand geometrically (spherically)? We can't detect an overall phase difference, but we can detect a local one (more distant galaxies are moving away faster than closer galaxies). Relative to the local group, say.

P.S. Another way to say 'implies a norm-preserving linear transform(ation)' is: 'implies a (probabilistic) time-evolution'.
If the universe really is a computer, then it's also a quantum computer.

 

How can the universe be expanding if the Earth is unchanging?

 

There's this gravity thing...

 

Gravity makes every part of the universe grow except the Earth?

 

Gravity keeps the earth together, and a lot of other things besides.
At large scales, objects are receding from each other.

That's high school science, dude.

 

So if "gravity keeps the earth together, and a lot of other things besides", how come it doesn't "keep the universe together"? If gravity keeps the Earth from expanding, how come it doesn't keep the sun from expanding, or the galaxy from expanding, or the universe from expanding? And if gravity keeps planets from expanding, how is it possible for planetary embryos to grow in the presence of gravity?

 

The galaxy is expanding?
The universe expands because "that's what universes do".

When you use the word "grow" you think that means "expand", don't you?

 

Alright... except there is no problem of speed limits in the case of the 'expansion of the universe'

The 'expansion of the universe' is special. That's right... special.

 

The idea is that space as in the distance between objects expands so they move apart, unless held together by local gravity. We have extremely remote objects held in our local cluster by gravity yet in the big bang idea, the whole universe was in the area of our solar system and continued expanding instead of becoming a black hole. Even a creationist could see that is wrong.

 

It does.

It does.

It doesn't because things are too far apart. Planets, planetary systems, and galaxies all have objects close enough for gravity to hold them together.

The universe is moving apart too fast for gravity to hold it together. Think 'escape velocity'.

I think you're getting mixed up a bit here.