# Mass have volume ?

1. Aug 18, 2011

### dailydc

Hi
Question is
Mass have volume ?

Another question is
Photons have mass "m=E/(c^2)" or "m = h*f/c^2" so
Photons have volume ?

2. Aug 18, 2011

### Staff: Mentor

There is no physical size to a particle the way you think of it in your daily life. MATTER, not mass, has volume because electron orbitals in atoms have a finite radius from the nucleus and the repulsion of electrons vs electrons keeps other atoms at a distance, even when bound into molecules.

Light does not have mass in the sense of stationary rest mass, but it does have momentum. Usually momentum is a product of mass x velocity, but photons have no mass. Also, photons are Bosons, and as such they can occupy the same spot as other photons. In effect, they have no real volume like you would imagine it.

3. Aug 18, 2011

### dailydc

You say , W bosons and Charm quarks and electrons have no volume and do not Occupy space ?!

if we have plank volume ( 1.616252×10^−35 m ) ^ 3 , is it possible in the volume there are one million electron ?

Last edited: Aug 18, 2011
4. Aug 18, 2011

### Staff: Mentor

No, I am saying the concept of "volume" is not the same at the quantum level. Classically a particle can have a volume, but when you get into quantum mechanics it gets more complicated. For example, the probability of finding two electrons at the exact same spot at the exact same time in the exact same state is 0. You could say that the "volume" of the electron could be found by measuring the electric field it emits, but you would be ignoring other issues. Conversely, a photon or other particle that does not obey the Pauli Exclusion Principle can easily occupy the same state as any number of other bosons. Meaning that it can occupy the same spot in space at the same time with any number of other bosons. This seems wierd to most people, as our everyday experiences tell us differently. After all, when I stack cups in my cabinets they don't merge into one cup!

Then you would need to get into wavefunctions. An electron has a wavefunction that determines its position and momentum. But where exactly is the electron? We don't know! Does it occupy the entire region that the wavefunction describes, or does it roam around the area? See what I'm getting at?