If everything is made up of atoms, what is vacuum made up of? [duplicate]

Do empty space in our universe exist or it is all filled with dark matter or some other unknown matter?

• Not everything is made up of atoms. Pions and muons, for example, are not made of atoms, and yet they are tangible things that can interact with matter in well-defined and well-studied ways. – probably_someone Jun 7 '19 at 10:52

“Vacuum” is often loosely defined as the absence of matter.

Interstellar and intergalactic space has a very low density of atoms, so it can be considered a vacuum to a good approximation. However, every cubic centimeter of the universe actually contains about 400 photons left over from the Big Bang, so radiation fills the universe. There are also believed to be lots of leftover neutrinos everywhere, a kind of lightweight matter. Physicists also think dark energy (not dark matter) is everywhere. Dark matter is believed to mainly clump around galaxies, so there is probably not much of it between galaxies.

An ideal vacuum would have no matter (including no atoms, no neutrinos, and no dark matter) and no radiation (such as photons) either. But it could still have dark energy, which is sometimes called “vacuum energy”.

Physicists think of the ideal vacuum state as the state in which there are no field quanta but there can nevertheless be field energy.

• How do we explain the nothingness – P-S-S Jun 6 '19 at 5:40
• @pss Why do you think nothingness needs an explanation? Most people think it is non-nothingness that needs to be explained. – G. Smith Jun 6 '19 at 5:41
• See ....imagine when you say nothing is present in this universe ....should we think of blank space.....or what .... – P-S-S Jun 6 '19 at 5:44
• @pss Have you studied quantum mechanics and the harmonic oscillator? Does the $n=0$ state need an explanation? – G. Smith Jun 6 '19 at 5:45
• What nothingness is ....is it blank space or nothing....we can’t imagine I hope right? – P-S-S Jun 6 '19 at 5:45