Mass and Matter

[Collision]

What is the difference between mass and matter?

[MolecularMan14]

Mass-

noun: the property of a body that causes it to have weight in a gravitational field

Matter-

noun: that which has mass and occupies space

 

Matter has the property of mass, by occupying (sp??) space. Matter is the property of that matter to hold "weight"

[Severian]

In particle physics, matter is usually defined as the fundamental representation of symmetry groups. So an electron is matter (since it is a fundamental representation of the U(1) symmetry) but the photon is not (since it is an adjoint representation). In practice this means everything is matter except for the particles which transmit the forces (photon, gluon, etc).

 

The definition of mass given my MolecularMan14 is 'gravitational mass' (eg in Newtonian gravity it is the m's in F=Gm₁m₂/r²). 'Inertial mass' is a quantity which governs how the body accelerates when a force is applied (so in Newtonian mechanics it is the m in F=ma). In 1900 or so Eotvos showed that they were the same (to the accuracy he measured) and Einstein used this idea to construct general relativity.

[Collision]

Severian said: "In practice this means everything is matter except for the particles which transmit the forces (photon, gluon, etc)."

 

So, this must be true: I cannot sense particals that don't transmit force, because I only sense things that can transmit force. I sense the photon or gluon type particals, because they transmit force, which then I do feel, see or hear.

[Severian]

So' date=' this must be true: I cannot sense particals that don't transmit force, because I only sense things that can transmit force. I sense the photon or gluon type particals, because they transmit force, which then I do feel, see or hear.[/quote']

 

Yes.

 

Sort of. One has some difficulty with the definition of 'you'. I get the impression that you are thinking of yourself as purely matter, in which case you are correct - your matter particles can only feel a force if it is transmitted by a gauge boson (such as a photon). But on the other hand, you could consider the photons in your body which are being transmitted back and forth to keep molecules in your body together as part of 'you'. In this case, as electron could also interact with 'you' since it can interact with these photons.

 

In QED for example, there is basically only one possible interaction and that is between an electron and a photon. So two electrons for example cannot interact without a photon being involved.