Where EXACTLY is the Mass of an Atom? Proton? Quark? Hadron? Gluon?

  • Thread starter NoVA101
  • Start date
  • #1
26
2
Where EXACTLY is the "Mass" of an Atom? Proton? Quark? Hadron? Gluon??

Just look at the simplest Hydrogen atom -- one Proton. The question is *where* exactly is the mass of this thing? Or *what* makes up the mass of this thing? Is it just Quarks? So where is the *mass* of those things? Where is the difference between mass and energy. Is there any? Is there really such a thing as mass, or is it all just energy appearing in different forms? Does anyone know? Is this the end of Physics and the beginning of Philosophy, again meaning no one really knows???

No one seems to have made this clear on Wikipedia either...
http://en.wikipedia.org/wiki/Mass
http://en.wikipedia.org/wiki/Quark#Mass

In a hadron most of the mass comes from the gluons that bind the constituent quarks together, rather than from the individual quarks; the mass of the quarks is almost negligible compared to the mass derived from the gluons' energy.​

Really? Mass comes from gluon energy? If so is there really such a thing as mass, or is there only energy? Why do we think a rock has "mass"? Is a rock really a bunch of energy, but at our scale we perceive it as this so-called "mass" stuff?
 
Last edited:

Answers and Replies

  • #4
DavidSnider
Gold Member
500
141


Matter is a form of energy. It's kind of like asking where the water in an ice cube is.
 
  • #5
26
2


Matter is a form of energy. It's kind of like asking where the water in an ice cube is.
Well I guess the question is -- is there any such thing as matter at all, or is there ONLY energy? What is the distinction? When you look closely into a proton, where is the "matter", or is there no such thing, there is only energy that just appears to be matter but only at a certain scale?
 
  • #6
malawi_glenn
Science Advisor
Homework Helper
4,786
22


We had that discussion in several other threads this week regarding "mass - energy"

I mean we can always go further down in scale, til we encounter strings or whatever is the building block for the gluons and quarks.

But speaking in terms of standard model, the mass of hydrogen is proton + electron - bidning energy (13.6eV). The mass of the proton is mass of valence quarks + quark/gluon sea (the binding energy of the proton, which is positive in this case)
 
  • #7
Vanadium 50
Staff Emeritus
Science Advisor
Education Advisor
26,150
9,541


I think it's a mistake to try and say the energy (or mass) is in one place. Energy (and mass) is a property of configurations of objects.

Consider two photons flying away from each other. Neither has mass. But the system does.
 
  • #8
malawi_glenn
Science Advisor
Homework Helper
4,786
22


One can ask what makes up the mass, but not "where is the mass located"
 
  • #9
816
1


The answer to this requires years of physics studies:

Things get more heavy in different reference frames, mass defect, mass hyperboloid, inertial or gravitational mass... First you should probably know what mass you are referring to.

Then we have the problem that "where" doesn't work anymore in quantum mechanics, if you have any information about the speed/the energy.

Then we can dissolve massive particles into electromagnetic energy and back, which happens like mad in the calculations for tiny time differences.

But for most purposes we just say the atom has mass and that's it.
On the next level we say the proton and the electrons have mass but these objects don't exist in a place anymore, but they just appear there when we measure. The proton can be broken down further, but it changes its apearence depending on the speed of our probe.

"The everything is energy approach" which many "new age"y people seem to fantasize, fails pretty badly for electrons, which have 0 size, so no known substructure and carry a mass.
 
  • #10
2,425
7


Then we have the problem that "where" doesn't work anymore in quantum mechanics, if you have any information about the speed/the energy.
That is a bit simplistic, so I would like to specify that energy distributions still exist in the quantum world.
Then we can dissolve massive particles into electromagnetic energy and back, which happens like mad in the calculations for tiny time differences.
Talking about the proton mass, the strong interaction is more relevant than the electromagnetic one, which is a small (albeit important) correction.
The proton can be broken down further, but it changes its apearence depending on the speed of our probe.
I think it would be more appropriate to talk about scale dependence. In particular, the concept of "speed" (as a spatial derivative) is not very well suited to virtual particle. At best, let's talk about momentum transfer.
 
  • #11
179
0


What is the distinction
I think the distinction occurs when talking about inertia.

A photon does not have inertia, but does have mass. And so energy on its own does not have inertia.
 
  • #12
2,425
7


A photon [...] does have mass.
How do I measure the mass of a photon ?
And so energy on its own does not have inertia.
What would be an instance of "energy on its own" ? Where can I find that ?
 
  • #13
179
0


How do I measure the mass of a photon ?
What would be an instance of "energy on its own" ? Where can I find that ?
I should have been more clear, what I meant was: A photon has a gravitational pull, but no inertia. So they are not exactly the same thing. The way you could measure it is by watching how much light bends when it passes large stars. And then treat it as a particle and find the mass that it would have if it was a particle.

And what I meant by that was just because something has energy, it does not necessarily have "mass" (as in the kind of mass that has inertia).
 
  • #14
2,425
7


A photon has a gravitational pull
I thought photons always use the straightest spacetime trajectories (geodesics).
The way you could measure it is by watching how much light bends when it passes large stars. And then treat it as a particle and find the mass that it would have if it was a particle.
Do you mean, applying Newton's formulae and deducting the equivalent mass ?
 
  • #15
179
0


I thought photons always use the straightest spacetime trajectories (geodesics).
Yeah, and that means that they follow a curved path in our 3 dimensional world. And always curve towards massive objects. I think, but I am not sure at all, that the higher the frequency of an photon (and the higher energy) the more gravitational attraction it has and so the higher frequency photons curve round things more.


Do you mean, applying Newton's formulae and deducting the equivalent mass ?
Yes

btw; I am not an expert on this.

[edit] Can someone confirm if I am right or not please, I don't want incorrect things to be in this thread[edit]
 
Last edited:
  • #16
22
0


"All of the above" would be an accurate answer.

As for where these basic constituents derive their masses, well, we believe it's through interaction with the Higgs field. LHC experiments in the coming years will (hopefully) shed some light on that issue.
 
  • #17
26
2


"All of the above" would be an accurate answer.

As for where these basic constituents derive their masses, well, we believe it's through interaction with the Higgs field. LHC experiments in the coming years will (hopefully) shed some light on that issue.
So mass is the result of an interaction? With a field? The interaction of what with a field? And is an "interaction" another way of saying "energy", or not? And you mean we have to do more experiments because we really don't know? Is all of this to say that we really don't know what-the-heck mass actually is? How very strange!
 
  • #18
22
0


So mass is the result of an interaction? With a field? The interaction of what with a field? And is an "interaction" another way of saying "energy", or not? And you mean we have to do more experiments because we really don't know? Is all of this to say that we really don't know what-the-heck mass actually is? How very strange!

It is kind of strange. Truth is, it's still basically a mystery where the masses of fundamental particles come from. So far, they are just input parameters for the Standard Model.
 
  • #19
2,425
7


Is all of this to say that we really don't know what-the-heck mass actually is? How very strange!
Why ? I personally find quite impressive that we have even the perspective to answer such a question !
 
  • #20
26
2


Why ? I personally find quite impressive that we have even the perspective to answer such a question !

There just seems to be such a huge and obvious disconnect! Drop a rock on your foot = ouch! Whack a rock upside your head = really ouch! That thing has mass! It seems so obvious.

But apparently it is not. Where is the mass in that rock? Well, y'know, it just obviously, like, has mass, or something. You can, like, just see it and do experiments and see the results of this "mass" stuff. Right?

But probably the majority of a rock is the vacuum of space -- so that can't be it, right? Do the electrons swirling around the nucleus have mass? "Electrons have no known substructure and are believed to be point particles" -- that just sounds ridiculous! http://en.wikipedia.org/wiki/Electron Yet they supposedly "have mass" or something. And as you dig into Protons you never actually find that "stuff", that "mass" that makes up the rock, do you? You find more charges, or interactions, or energy, or bonds, or some cool cutting-edge, poorly-understood, we'll-get-that-someday-in-the-future theoretical thingamajobbie -- but nothing that has any apparent "substance" -- whatever that might mean!

When a rock whacks you upside the head, where/what is the mass?
 
  • #21
199
0


...Can someone confirm if I am right or not please, I don't want incorrect things to be in this thread...
Well, not too long ago I went through some effort on these boards to convince people that photons are indeed massless particles. Generally when people talk about "mass", I believe what's meant is "inertia", not general-relativistic gravitational interaction.

What you are saying looks correct, but I think it would avoid some potential confusion to phrase it differently, so that photons are massless particles with nonzero energy, and it is this energy that connects them to general relativity. After all, it is the stress-energy tensor that pops up in Einstein's equations.

That whole discussion is also pretty far removed from the original poster's dilemma. Getting back to that issue, I think gaining a deeper understanding of the special-relativistic relation between mass and energy is the best prescription.
 

Related Threads on Where EXACTLY is the Mass of an Atom? Proton? Quark? Hadron? Gluon?

  • Last Post
Replies
4
Views
823
  • Last Post
Replies
13
Views
2K
  • Last Post
Replies
15
Views
2K
Replies
8
Views
3K
  • Last Post
Replies
15
Views
4K
  • Last Post
Replies
4
Views
7K
Replies
30
Views
5K
  • Last Post
Replies
5
Views
1K
Replies
4
Views
4K
Replies
5
Views
2K
Top