What do we regard as the universe....

[NiftyNiblick]

...just the measurably expanding distribution of known matter,
or do we include the vacuum of space in which it resides?

I personally include the latter
which is why I believe the universe to be infinite.

 

[Cypress]

...just the measurably expanding distribution of known matter,
or do we include the vacuum of space in which it resides?

I personally include the latter
which is why I believe the universe to be infinite.

Technically it's not matter that is expanding or flying apart.

It's the space itself between the galaxies which is stretching, and carrying the galaxies along with it.

Space has an inherent vacuum energy and is permeated by quantum fields, so even seemingly empty space really doesn't count as 'nothing'.

 

[NiftyNiblick]

Technically it's not matter that is expanding or flying apart.

It's the space itself between the galaxies which is stretching, and carrying the galaxies along with it.

Space has an inherent vacuum energy and is permeated by quantum fields, so even seemingly empty space really doesn't count as 'nothing'.

So you believe that space is finite as well, right?
I can't imagine that for some reason.
Something, even if it's virtually nothing,
has to exist beyond any boundary the way my mind works.

I don't know what actual IS,
but I know what I can and can't imagine.

 

[Margot]

Technically it's not matter that is expanding or flying apart.

It's the space itself between the galaxies which is stretching, and carrying the galaxies along with it.

Space has an inherent vacuum energy and is permeated by quantum fields, so even seemingly empty space really doesn't count as 'nothing'.

Wow! That empty space between Trump's ears,isn't nothing

 

[Cypress]

So you believe that space is finite as well, right?
I can't imagine that for some reason.
Something, even if it's virtually nothing,
has to exist beyond any boundary the way my mind works.

I don't know what actual IS,
but I know what I can and can't imagine.

If I had to bet, I would say spacetime is finite. That makes more sense to me than infinite spacetime. I can conceptually make spacetime finite simply by applying the concepts of geometry and topology.

I don't think the universe is like a box, with a boundary condition between what is in the box, and what's outside it.

I don't think the universe is 'expanding' in the way we think of a ballon or baking bread expanding.

It's spacetime that is stretching. It's not that conventional atomic matter is flying apart in a violent explosion.
You aren't expanding, the Earth isn't expanding, the Moon isn't expanding. It's just spacetime that's stretching. I imagine its somewhat like how radiation and visible light can 'stretch' to lower wavelengths, without actually being conventionally stretchable or expandable in the manner our minds think about those words.