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Q & A: space vacuum

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Most recent answer: 03/25/2020
Q:
we were taught that the vacuum simply means the absence of any atoms/particles/molecules. the space, which is a vacuum, consist of the solar system, which consists of stars, planets and many more. but isn’t the planets and stars also made up of particles, molecules, just like every living and non living things on earth are made up of particles/atoms/molecules. so why do we refer to the space as vacuum?
- authum (age 15)
commonwealth sec, singapore
A:
When people say that space is a vacuum, they mean that the parts of space that are far away from planets, stars, etc. are nearly a vacuum. That means that the concentration of particles in those regions is very tiny compared to the concentration in our atmosphere.

Mike W.

(published on 10/22/2007)

Follow-Up #1: vacuum particles

Q:
I heard somehwere that space vacuums or areas between atoms are actually full of very tiny particles (not including photons from light) is this true and hwat are these particles?
- Zac (age 17)
New Zealand, Hamilton
A:
There are several true ideas that the people who said that might have been getting at. However, the picture of little tiny dot-like particles fitting in empty spaces is definitely not even close to being a correct way to describe things.

All small-scale things (and maybe large scale things too) are quantum objects. They don't have definite values of position, velocity, sometimes energy, or even number of particles. So 'empty' space has the possibility of acting as if it has particles in it, if something pokes it the right way. That's true for any sort of particles, but the ones that show up most easily are the one with lowest rest mass. The electron/positron pair is particularly important. Neutrinos have even lower rest mass, but they don't interact much with anything. (We're not counting the particles with zero rest mass, the photons, at your request.)


Perhaps what you heard referred to the wave nature of particles, particularly electrons. The electron state is spread out, and a weak tail of it extends far out from each atom. In ordinary materials, there's no region between the atoms where the chance of finding an electron is really zero.

Mike W.

(published on 08/19/2009)

Follow-Up #2: does gravity occur in space?

Q:
does gravity occurs in space??
- hajer (age 15)
A:

Yes, it accounts for the large-scale patterns of motion of galaxies, etc.

Mike W.


(published on 07/05/2018)

Follow-Up #3: space and Big Bang

Q:
This is so frustrating. I am finding science minds all over the map about space is a vacuum and space is not a vacuumThe Big Bang happened but is not the beginning and the Big Bang is the beginningWill this ever be resolved?
- Ronnie D Akins (age 47)
Phoenix
A:

The issues you mentionn about  space are mostly just matters of people using words like "vacuum" and "space" in a sloppy way. Our answer above should help. 

QUestions about Big Bang really are still open. In principle, there are ways of trying to answer them, or at least narrow down the possible answers. For example, looking at patterns in the cosmic microwave background radiation should help sort out some the the theories.

Mike W.


(published on 03/25/2020)

Follow-up on this answer.