[Seany (OP)]

Is space a vacuum?
Then what about all the planets and stars..?

What about the gases in space?

Definition of Vacuum in Dictionary.com

1. a space entirely devoid of matter.

And as suns burn off, what happens to the gas that's made?

[another_someone]

Space is only a partial vacuum.  In the real universe, a true vacuum is an impossibility, so vacuums are inevitably only relative.  Relative to anything we experience on Earth, Space is a vacuum.

[Seany (OP)]

So is space only a vacuum because the stuff it has in it, is so small in relative to the amount of planets etc in there?

[DoctorBeaver]

Forget virtual particles for a moment as they don't really count. In space - real, deep intergalactic space (more remote even than Texas), there are only a few atoms per zillion cubic parsecs (OK, that's a slight exaggeration). What about in between those atoms? Surely, that is vacuum in the true sense of the word.

[Seany (OP)]

I see []
Still.. The dictionary doesn't lie []

LOL just kidding

[another_someone]

Forget virtual particles for a moment as they don't really count. In space - real, deep intergalactic space (more remote even than Texas), there are only a few atoms per zillion cubic parsecs (OK, that's a slight exaggeration). What about in between those atoms? Surely, that is vacuum in the true sense of the word.

The argument is no different from asking what about the space between atoms that are 1nm apart - the space between atoms is still the space between atoms.

[DoctorBeaver]

But is it vacuum?

[another_someone]

But is it vacuum?

We probably start getting too far into semantics here, but I would think the definition of a true vacuum is a place where there is a zero probability of encountering an atom (or other particle - ofcourse, this latter qualification may also question whether you can have radiation in a true vacuum).  Clearly, even if you only have one particle every 200 miles, if those particles are not contained in some way, then the probability of you encountering said particle, while very very small, is still non-zero.

[Seany (OP)]

But in the gaps between the atons.. That's a vacuum right?
But Space itself isn't..

[DoctorBeaver]

We probably start getting too far into semantics here, but I would think the definition of a true vacuum is a place where there is a zero probability of encountering an atom

Is that a QM definition?

[Soul Surfer]

The definition of a vacuum in scientific terms is NOT absolute.  It is a space where the pressure of gas is vey significantly less than atmospheric  and there are various sorts of guages that will tell you how low the pressure is so the original postulate is incorrect.

The pressure of gas in most laboratory vacuum systems is considerably higher than the pressure of the gas in the outer solar system whic is in turn considerably higher than the pressure of the gas in remote intergalactic space.

As for planets star and other lumps and the atmospheres that ther have close to them.  they just dont count.

[lyner]

On average, there is about one proton per cubic metre of of the Universe. To make up for the dense bits (like Earth) some regions must have less than this.