# What is your understanding of "Matter"?

Simple question really. When you talk about “matter and energy”, what do you think “matter” is?

Anything that can be shown to have a mass?

What about massless particles such as photons and gluons?

They are force carrying particles, which are not matter but are the elementary building blocks of matter.
Do they have a mass?
Edit: Sorry, I missed the massless bit.

If matter is anything that can be shown to have a mass, then massless particles such as photons and gluons are not matter.
If force carrying particles such as (photons and gluons) are not matter, what about W and Z bosons which are also force carrying particles that have mass as well.

There does not appear to be a consistent understanding of matter from the above.
If there is not a consistent understanding of matter, it does not make sense to speak of “elementary building blocks of matter”.

Perhaps matter as "everything that can be shown to have a mass is a wrong conception of matter?

How about everything that can be shown to have physical and measureable dimensions and is able to take up space? This can the include strings and branes (length = 10^-33 cm)?

So a small vacuum chamber can house a small vacuum, and a large vacuum chamber can house a large vacuum? Vacuum therefore has a physical and measurable dimension and is able to take up space.

Matter as just something with a physical and measurable dimension does seem to include vacuums. Vacuums as matter as well then?

Maybe we should then agree to the usual “anything that has mass and occupies volume”?

When mass is measured in electronvolt things get a bit muddy for me. I still believe, probably wrongly but I’d like to be convinced, that mass–energy equivalence only counts for particles at rest.

No. They have a zero rest mass. That’s an important distinction ― E = mc² and all that.

No, it applies to all particles, even those with zero rest mass. A particle with zero rest mass in motion has energy and exhibits inertial behaviour exactly as it would if it had the mass calculated from Einstein’s famous equivalence. In any case, Einstein banished the Newtonian absolute frame of reference, so a particle at rest is only at rest relative to some arbitrary inertial frame of reference, but there are many others relative to which it is in motion. Acceleration complicates things further. In addition, spacetime is foaming with virtual particles popping in and out of existence as a result of Heisenberg uncertainty concerning mass-energy and its lifetime.

'Luthon64

So a photon at rest have a zero mass, but traveling through a vacuum at the speed of light it has an infinite mass?

Stuff.

What makes you think its mass is infinite?

The first point to understand here is that a photon has zero rest mass (mo = 0) and a velocity v = c which is the same in all inertial frames, regardless at what velocity the observer is travelling. This is a totally counterintuitive notion because it would be like saying that a bullet fired at a velocity of 200 m/s from a car moving at a velocity of 30 m/s, the bullet travels at a speed of 200 m/s relative to the ground. Now when we plug the values mo = 0 and v = c into Einstein’s mass increase formula, we get 0/0, the value of which is not defined. Another way of saying this is that the photon’s mass is completely unknown, yet it exists because it can interact measurably with other matter, e.g. knocking an electron into a higher-energy orbital.

The next point to note is that we can speak meaningfully of a photon’s energy, which is given by E = h·f where h is Planck’s constant and f is the photon’s frequency. In other words, a given photon has a precisely determined energy associated with it. We could now use E = m·c² to calculate an equivalent mass of the photon because the two energies are the same. The resulting formula is m = h·f/c² ― that is, the photon’s equivalent mass depends linearly on its frequency only because h and c are constants. Were it not for photons’ quantum nature, a photon would behave inertially as if it had that equivalent mass, i.e. if you tried to accelerate it or calculate its momentum. But, as said, photons are subject to quantum laws.

'Luthon64

So muffles, you explain the coming and going of virtual particles pretty well, what is your understanding of matter then?

“Matter = everything with mass” does not quite seem to cut it (or do you think it does).
“Matter = everything that has mass and occupies volume” does not cut it.
“Matter = Stuff”… well it is quite a mystery what stuff is in scientific terms so…

What do you say?

oh noes, the metaphysical raises it’s ugly head once more! :

Are we to assume the other 4 threads have been abandoned with questions addressed to you forever remaining… a mystery?

My understanding is that the more you accelerate the photon the more energy you need, and when you get to the speed of light you need infinite energy which will give the photon infinite mass.

Here’s another probably stupid question. To get the photon to transmit light, does it have to travel at the speed of light?

And you, what is your understanding of matter? Just asking, you know, you being the go to guy for straight answers and all.

Why the fuck should I bother, Mr Evasion?

Because you are better than that ;D:

Don’t worry, if you feel ignored, try the happy place for all unanswered questions. Tell the world about all your questions, maybe someone will answer them and then the world will be your happy place again >:D.

Also, don’t worry about me, I have faith that you will answer the question “What is your understanding of “Matter”?” since you seem to be a civil conversationalist that answers direct questions directly. Thank you in advance.