Is Relativistic Mass Still Relevant in Modern Physics Discussions?

[JesseM]

If it supported your claim, then the mass of the deutron should be LARGER than the mass of the proton and neutron combined. Because it not only contains your proton and neutron, but also binding energy - which adds to the total energy.

No, the potential energy is greater when you pull the proton and neutron apart than when they are bound together--that's why they naturally tend to stick together! As it says in the wikipedia entry on binding energy, "A bound system has a lower potential energy than its constituent parts; this is what keeps the system together; it corresponds to a positive binding energy." In other words, binding energy is defined in a funny way, so that more positive binding energy is equivalent to less potential energy, and it's potential energy that you must use when calculating the total energy of different states.

 

[Aer]

No, the potential energy is greater when you pull the proton and neutron apart than when they are bound together--that's why they naturally tend to stick together! As it says in the wikipedia entry on binding energy, "A bound system has a lower potential energy than its constituent parts; this is what keeps the system together; it corresponds to a positive binding energy." In other words, binding energy is defined in a funny way, so that more positive binding energy is equivalent to less potential energy, and it's potential energy that you must use when calculating the total energy of different states.

I looked up the definition of binding energy, got:
"the energy that holds a nucleus together; the difference between the sum of the masses of the individual nucleons and the actual mass of the nucleus."

is this definition wrong?

 

[Aer]

Is the binding energy apart of the deutron or not?

 

[JesseM]

I looked up the definition of binding energy, got:
"the energy that holds a nucleus together; the difference between the sum of the masses of the individual nucleons and the actual mass of the nucleus."

is this definition wrong?

It's not wrong, but it could be misleading if you interpreted it to mean that there was some form of energy that increased in the bound state rather than decreased. It is the decrease in potential energy that holds a bound system together, and the fact that you have to climb a potential hill to separate the parts that makes it difficult to do so--do you disagree with this?

 

[Aer]

It's not wrong, but it could be misleading if you interpreted it to mean that there was some form of energy that increased in the bound state rather than decreased. It is the decrease in potential energy that holds a bound system together, and the fact that you have to climb a potential hill to separate the parts that makes it difficult to do so--do you disagree with this?

All this says is that the proton and neutron lose rest mass when they are bound together. This rest mass is referred to as the potential energy since all mass is essentially a form of energy. But this doesn't imply that kinetic energy or gravitational potential energy will become the potential energy that is considered mass. At least, there is nothing to assume that. What is needed is experimental evidence, not this endlessly pointless discussion.

 

[Aer]

Can we at least agree to disagree for now?

 

[Aer]

I guess at least I'll have to agree to disagree - going to bed, goodnight!

 

[JesseM]

Is the binding energy apart of the deutron or not?

I'm not sure what you mean by "a part of it". The potential energy of the bound and unbound state (which the binding energy is based on) must be taken into account when calculating the total energy of each state, but then the kinetic energy of each particle must be taken into account as well. The inertial mass of a compound object is proportional to the sum of potential, kinetic and rest mass energies of all its parts.

 

[JesseM]

All this says is that the proton and neutron lose rest mass when they are bound together.

No they don't! The rest mass of a proton in a deuteron nucleus is the same as the rest mass of a free proton, the rest mass of a given type of particle never changes, it's a constant of nature.

This rest mass is referred to as the potential energy since all mass is essentially a form of energy.

Not by any physicists, no.

But this doesn't imply that kinetic energy or gravitational potential energy will become the potential energy that is considered mass.

So electromagnetic potential energy (responsible for chemical binding between atoms) and strong-force potential energy (responsible for nuclear binding between protons and neutrons) can contribute to inertial mass, but somehow gravitational potential energy can't? And again, there is no existing theory of physics that explains changing potential energy between particles in terms of the particle's rest mass changing when the distance between them changes, you're just making stuff up off the top of your head now.

 

[JesseM]

I guess at least I'll have to agree to disagree - going to bed, goodnight!

OK, goodnight...

 

[Aer]

No they don't! The rest mass of a proton in a deuteron nucleus is the same as the rest mass of a free proton, the rest mass of a given type of particle never changes, it's a constant of nature. Not by any physicists, no. So electromagnetic potential energy (responsible for chemical binding between atoms) and strong-force potential energy (responsible for nuclear binding between protons and neutrons) can contribute to inertial mass, but somehow gravitational potential energy can't? And again, there is no existing theory of physics that explains changing potential energy between particles in terms of the particle's rest mass changing when the distance between them changes, you're just making stuff up off the top of your head now.

I'm making things up? I don't think so, the least I've done is inquire. You are the one making things up saying that kinetic and gravitational potential energy can be considered the same as the energy form of mass, consider this answer from Dr. Ken Mellendorf"

The mass of an atom is not the sum of the
masses of its individual parts. The mass of an atom is in fact less than
the mass of its parts.
The mass of an atom is the sum of the masses of its parts, minus (binding
energy)/c^2. Each proton and each neutron still have their original masses.
The loss of energy to the outside world results in a decrease of atomic
mass. At the level of particles and atoms, mass is NOT conserved. After an
event, you may end up with more or less mass than you started with. Total
energy, including E=mc^2, is conserved. Mass behaves like just another location
of energy. A negative potential energy can make the total energy less than
the sum of the other energies. At the atomic level, a negative potential
energy can make the total mass less than the sum of the individual masses.

Dr. Ken Mellendorf
Physics Professor
Illinois Central College

He uses total energy as the rest energy equation, E=mc^2.

Total energy in your situation (taking into account kinetic energies) is E=γ mc^2

 

[JesseM]

I'm making things up? I don't think so, the least I've done is inquire.

You're making stuff up when you say changes in potential energy are "really" changes in the rest masses of the particles (except in the case of gravitational potential, for some reason). There is no theory of physics that says this.

You are the one making things up saying that kinetic and gravitational potential energy can be considered the same as the energy form of mass

What does "the energy form of mass" mean? Do you mean inertial mass?

consider this answer from Dr. Ken Mellendorf"

The mass of an atom is not the sum of the
masses of its individual parts. The mass of an atom is in fact less than
the mass of its parts.
The mass of an atom is the sum of the masses of its parts, minus (binding
energy)/c^2. Each proton and each neutron still have their original masses.
The loss of energy to the outside world results in a decrease of atomic
mass. At the level of particles and atoms, mass is NOT conserved. After an
event, you may end up with more or less mass than you started with. Total
energy, including E=mc^2, is conserved. Mass behaves like just another location
of energy. A negative potential energy can make the total energy less than
the sum of the other energies. At the atomic level, a negative potential
energy can make the total mass less than the sum of the individual masses.

Dr. Ken Mellendorf
Physics Professor
Illinois Central College

He uses total energy as the rest energy equation, E=mc^2.

That sentence is ambiguous--when he says that total energy including E=mc^2 is conserved that could mean that "total energy" includes other things beyond E=mc^2 for each part--for example, the potential energy. Or, the "m" there may refer to the rest mass of the whole system, and as I've been saying, the rest mass of a composite system is defined to be equal to the total energy (which includes potential energy) divided by c^2. He also says that "the mass of an atom is in fact less than the mass of its parts", because you have to include the potential energy to get the total mass, and as he says, the potential energy is negative in the bound state (when compared to the unbound state). This is exactly what I've been saying! And it contradicts your claim that the mass of the atom is still equal to the sum of the mass of its parts, but that the mass of the proton and neutron have somehow decreased.

 

[Ich]

I don´t want to interfere, but I want to comment Mellendorf´s sentence "At the level of particles and atoms, mass is NOT conserved."
Mass is always conserved, as is Energy. After an an event (like n+p -> np + hf) the mass of the system still is the same. The photon contributes to the mass of the system, even though it has no mass itself.
Mass will change only when you change the system you´re considering, e.g. by neglecting the photon in the example.

 

[Aer]

He also says that "the mass of an atom is in fact less than the mass of its parts", because you have to include the potential energy to get the total mass, and as he says, the potential energy is negative in the bound state (when compared to the unbound state). This is exactly what I've been saying! And it contradicts your claim that the mass of the atom is still equal to the sum of the mass of its parts, but that the mass of the proton and neutron have somehow decreased.

That is not my claim when dealing with masses at the quantum level! If I said anything similar to that, it was because you were confusing the issue of whether we are talking about the quantum level or macroscopic level.

Just to be clear - this example is on the quantum level, in which energy and mass -do- lose distinction. Taking this to the next level - that is, putting macroscropic objects in a box with relative velocity to the box and claiming the kinetic energy -adds- to the mass at the macroscopic level, just like a negative energy -subtracts- from the mass at the microscoptic level is not sufficient.

You must show that this kinetic energy -adds- to the mass at the macroscopic level and not just state it to be so. THIS, and only this is the only point I am contending. Whether you believe physics is the same at the microscopic level and the macroscopic level is your prerogative. However - I know there is a difference as there is a thing called quantum physics! So unless you are willing to talk about your macroscopic level example, then you'll have to excuse me if I do not respond to your BS!

 

[learningphysics]

Just to be clear - this example is on the quantum level, in which energy and mass -do- lose distinction. Taking this to the next level - that is, putting macroscropic objects in a box with relative velocity to the box and claiming the kinetic energy -adds- to the mass at the macroscopic level, just like a negative energy -subtracts- from the mass at the microscoptic level is not sufficient.

The special theory of relativity predicts a change in mass whether or not the changes are quantum or macroscopic. Read Einstein's paper on mass-energy equivalence here:

http://www.ams.org/bull/2000-37-01/S0273-0979-99-00805-8/S0273-0979-99-00805-8.pdf

Note: "(6) The rest-energy changes, therefore, in an inelastic collision (additively) like the
mass. "

By mass, Einstein's referring to rest-mass.

His example uses a simple inelastic collision of two bodies. The lost kinetic energy goes into the rest energy of the two bodies and therefore their rest masses... he says nothing about the form of the energy... it could be heat or it could be nuclear binding energy... whatever. The case is general for any inelastic collision.

That's what the theory predicts. If two identical macroscopic baseballs collided in a symmetric inelastic collision losing some of their kinetic energy to heat, then each baseball would increase its rest energy, and therefore change its "rest mass". The increased "rest mass" is due to heat (which is the kinetic energy of the constituent particles that form the baseball).

I got this quote of Einstein's from this website:
http://www.cox-internet.com/hermital/book/holoprt3-1.htm

"In his 1938 book, The Evolution of Physics, 1 Einstein writes:

Energy, at any rate kinetic energy, resists motion in the same way as ponderable masses. Is this also true of all kinds of energy?
The theory of [special] relativity deduces, from its fundamental assumption, a clear and convincing answer to this question, an answer again of a quantitative character: all energy resists change of motion; all energy behaves like matter; a piece of iron weighs more when red-hot than when cool; radiation traveling through space and emitted from the sun contains energy and therefore has mass, the sun and all radiating stars lose mass by emitting radiation. This conclusion, quite general in character, is an important achievement of the theory of relativity and fits all facts upon which it has been tested.
Classical physics introduced two substances: matter and energy. The first had weight, but the second was weightless. In classical physics we had two conservation laws: one for matter, the other for energy.7 "

I cannot verify the accuracy of the quote as I don't have this book.

Note what he says... all energy resists change in motion. Therefore all energy has inertia... heat, kinetic energy, potential energy etc...

Also note that he says that a piece of iron weighs more red-hot... No nuclear changes need be involved.

 

[Aer]

Note: "(6) The rest-energy changes, therefore, in an inelastic collision (additively) like the
mass. "

By mass, Einstein's referring to rest-mass.

His example uses a simple inelastic collision of two bodies. The lost kinetic energy goes into the rest energy of the two bodies and therefore their rest masses... he says nothing about the form of the energy... it could be heat or it could be nuclear binding energy... whatever. The case is general for any inelastic collision.

You may have wanted to give the entire quote:

"(6) E0_bar - E0 = m_bar - m:
The rest-energy changes, therefore, in an inelastic collision (additively) like the
mass. As the former, from the nature of the concept, is determined only to within
an additive constant, one can stipulate that E0 should vanish together with m.
Then we have simply
E0 = m;"

That's what the theory predicts. If two identical macroscopic baseballs collided in a symmetric inelastic collision losing some of their kinetic energy to heat, then each baseball would increase its rest energy, and therefore change its "rest mass". The increased "rest mass" is due to heat (which is the kinetic energy of the constituent particles that form the baseball).

I would love to see you try to make two baseballs collide to become "one" - what you are referring to only happens on the quantum level, not the macroscopic level. All the kinetic energy will be given off as energy in another form in actuality.

I cannot verify the accuracy of the quote as I don't have this book.

You might want to verify it as it is in direct contradiction to the quote by Albert I gave.

 

[jtbell]

I don´t want to interfere, but I want to comment Mellendorf´s sentence "At the level of particles and atoms, mass is NOT conserved."
Mass is always conserved, as is Energy. After an an event (like n+p -> np + hf) the mass of the system still is the same. The photon contributes to the mass of the system, even though it has no mass itself.

Mellendorf's statement would have been phrased better as follows: "At the level of particles and atoms, (invariant) mass is not additive." The (invariant) mass of a system does not equal the sum of the (invariant) masses of the particles that it is composed of."

I put (invariant) in parentheses because many physicists (the ones who don't use the concept of "relativistic mass") would omit it. In this context, since we're discussing both kinds of mass, we need to be explicit about which one we're talking about.

 

[Aer]

Mellendorf's statement would have been phrased better as follows: "At the level of particles and atoms, (invariant) mass is not additive." The (invariant) mass of a system does not equal the sum of the (invariant) masses of the particles that it is composed of."

I put (invariant) in parentheses because many physicists (the ones who don't use the concept of "relativistic mass") would omit it. In this context, since we're discussing both kinds of mass, we need to be explicit about which one we're talking about.

Yes, and it is true only at "the level of particles and atoms" (i.e. quantum physics).

 

[pervect]

Here's another link addressing the topic - I'm not sure whether I've posted it to this particular thread before or not.

http://arxiv.org/abs/gr-qc/9909014

From the abstract

According to the general theory of relativity, kinetic energy contributes
to gravitational mass. Surprisingly, the observational evidence for this
prediction does not seem to be discussed in the literature. I reanalyze
existing experimental data to test the equivalence principle for the
kinetic energy of atomic electrons, and show that fairly strong limits
on possible violations can be obtained. I discuss the relationship
of this result to the occasional claim that “light falls with twice the
acceleration of ordinary matter.”
email: carlip@dirac.ucdavis.edu

and the introduction to the paper

The principle of equivalence—the exact equality of inertial and gravitational
mass—is a cornerstone of general relativity, and experimental tests of the universality
of free fall provide a large set of data that must be explained by any theory
of gravitation. But the implication that energy contributes to gravitational mass
can be rather counterintuitive. Students are often willing to accept the idea that
potential energy has weight—after all, potential energy is a rather mysterious
quantity to begin with—but many balk at the application to kinetic energy. Can
it really be true that a hot brick weighs more than a cold brick?
General relativity offers a definite answer to this question, but the matter is
ultimately one for experiment. Surprisingly, while observational evidence for the
equivalence principle has been discussed for a variety of potential energies, the
literature appears to contain no analysis of kinetic energy. The purpose of this
paper is to rectify this omission, by reanalyzing existing experimental data to look
for the “weight” of the kinetic energy of electrons in atoms.

 

[Aer]

Here's another link addressing the topic - I'm not sure whether I've posted it to this particular thread before or not.

http://arxiv.org/abs/gr-qc/9909014

From the abstract


and the introduction to the paper

So all you are saying is what I've said - the evidence is inconclusive. Or do you wish to offer some other analysis.

 

[learningphysics]

You may have wanted to give the entire quote:

"(6) E0_bar - E0 = m_bar - m:
The rest-energy changes, therefore, in an inelastic collision (additively) like the
mass. As the former, from the nature of the concept, is determined only to within
an additive constant, one can stipulate that E0 should vanish together with m.
Then we have simply
E0 = m;"

What is your point?

I would love to see you try to make two baseballs collide to become "one" - what you are referring to only happens on the quantum level, not the macroscopic level. All the kinetic energy will be given off as energy in another form in actuality.

So you're saying Einstein was wrong? He used simple conservation of energy, and conservation of momentum... and he makes no mention of this "other form" of energy you're talking about? What exactly are you talking about here?

And who talked about two baseballs becoming one? The paper is about an inelastic collision. I mentioned a simple inelastic collision between two baseballs... nothing about two baseballs becoming one.

Einstein's derivation is general... it makes no mention of being at the quantum level... it applies to any two material bodies.

You might want to verify it as it is in direct contradiction to the quote by Albert I gave.

Which quote is that?

 

[pmb_phy]

Aer - I've explained that I will not participate in this discussion since anything you could possible ask has been addressed in the material I've linked to. If you have chosen to ignore my response to all of your questions (my response is in the material since I've pretty much knew what you were going to ask - and you did) then I will be ignoring your questions as well. It appears to me that even with my answers you are misquoting me, i.e.

Then we have people like pmb_phy claiming a contained gas's weight is a measure of the rest mass of the particles PLUS the kinetic energy they possess. UMMM - NO! That's wrong, the weight is only a measure of the rest mass of the particles and nothing more.

You've got this quite wrong. There is a mass corresponding to the kinetic energy. Problem with the "mass = rest mass" definition is that people make mistakes like the one you've made here. Proof is not only given in my paper but these types of things have been done in the American Journal of Physics and I've posted those articles on my website and posted the link here as I recall. If you don't have the drive to look for the answer to your question in the paper given to you then here - m = p/v where p is the magniture of the momentum of the particle and v is the speed of the particle. I'm sure you'll object to this and as such your objections are in all probability addressed in the material I gave you.

Pete

 

[jtbell]

If two identical macroscopic baseballs collided in a symmetric inelastic collision losing some of their kinetic energy to heat, then each baseball would increase its rest energy, and therefore change its "rest mass". The increased "rest mass" is due to heat (which is the kinetic energy of the constituent particles that form the baseball)

I would love to see you try to make two baseballs collide to become "one" - what you are referring to only happens on the quantum level, not the macroscopic level. All the kinetic energy will be given off as energy in another form in actuality.

Actually, both of you are right, but you're looking at different stages in the compete sequence of events. To make the analysis simpler, instead of baseballs, consider two lumps of putty with equal (invariant) masses. They are both at room temperature. They move towards each other, with equal speeds in opposite directions. They collide and smush together. The result is a single stationary lump of putty.

The gross kinetic energy of the two original lumps is converted to thermal energy, i.e. random kinetic energy of the individual atoms in the putty (many people loosely and incorrectly call this "heat"). Therefore, immediately after the collision, the single lump is slightly warmer than room temperature. The (invariant) mass of this single lump is also slightly larger than the sum of the (invariant) masses of the two original lumps.

As time passes, the warm lump of putty cools to room temperature and loses its "extra" thermal energy to its surroundings via some combination of radiation, convection in the surrounding air (if it's not in a vacuum) and conduction (if it happens to be resting on a tabletop or something). As the putty cools and loses energy, its (invariant) mass also decreases.

 

[Aer]

What is your point?

The conclusion was that mass is proportional to rest energy.

Which quote is that?

"It is not good to introduce the concept of the mass of a moving body for which no clear definition can be given. It is better to introduce no other mass concept than the 'rest mass' m. Instead of introducing M it is better to mention the expression for the momentum and energy of a body in motion."

 

[pmb_phy]

You really shouldn't insult someone who took the time to respond to your post despite the fact that he was tired of the topic.

Thanks. Please note that I'm not ignoring all this because I'm lazy. I've had horrible back pain when I sit for more than a few minutes. It took a long time to figure out what it was. Turns out that I have a stone in my gall-bladder. It will be comming out when I have surgery in the near future. But for now I'm spending very little time on the internet. Especially on this topic and especially since this person is insulting me and ignoring the answers given to him by me that he asked for.

Why should he bother? He's not trying to make any argument here... You asked for his input and he gave it to you. Then you turn around and insult him for it.

Thanks. Its true that I'm not arguing here - a question was asked of me and I answered it. The insults are unwelcome. This seems odd for a moderated forum. What's happened since I've been absent?

Here is a point I rarely make - If I was a particle physicist then in all likelyhood I'd use the term "mass" to mean proper mass and I'd use no subscript. People in a field understand the meaning of a term. The meaning changes between fields. Their definion would fail if they can't treat their objects as having no extent into space. But then again they ignore that stuff. I've never seen a particle physicist try to anayze systems like a dipole in a field. Einstein did and then published it. People always ignore this since they only look at the 1905 paper and never at his later work where he gets more general. The topic of his paper in 1907 was posted and addressed in my website and has been ignored as I see.

Pete

 

[Aer]

Let's start with a simple question. Does a photon have energy?

It is very simple really. Either a photon has energy or it does not. Either all energy in a system contributes to it's mass or it does not. Awaiting answers.

 

[learningphysics]

The conclusion was that mass is proportional to rest energy.

All this while I've only been taking about mass as rest mass... I get the feeling you're not reading my posts.

In an inelastic collision the rest energy of constituent bodies change! And as a result of a change in the rest energy, the rest mass changes. This is a basic consequence of special relativity, as Einstein shows in the paper I showed you! Do you agree with this or not?

If you think Einstein's derivation does not apply to macroscopic bodies, please explain why.

 

[Aer]

All this while I've only been taking about mass as rest mass... I get the feeling you're not reading my posts.

In an inelastic collision the rest energy of constituent bodies change! And as a result of a change in the rest energy, the rest mass changes. This is a basic consequence of special relativity, as Einstein shows in the paper I showed you! Do you agree with this or not?

If you think Einstein's derivation does not apply to macroscopic bodies, please explain why.

A system can have multiple energies. As you've said, it can have kinetic energy and thermal energy to name a few. One of the energies a system has is mass. That is, mass is a form of energy. So when we add all the energies together of this puddy, we get total energy = mass energy + kinetic energy + thermal energy. In this case, the kinetic energy has been converted to thermal energy - notice that the mass energy is still there. Now answer my question: Does a photon have energy?

 

[JesseM]

That is not my claim when dealing with masses at the quantum level!

Really? Then what did you mean when you said "All this says is that the proton and neutron lose rest mass when they are bound together. This rest mass is referred to as the potential energy since all mass is essentially a form of energy." Were you not saying here that the deuteron's rest mass is still the sum of the rest masses of the proton and neutron, but that the proton and neutron's rest masses had actually decreased and that this was the explanation for why the deuteron's mass is less than the sum of the rest masses of a free proton and a free neutron?

Just to be clear - this example is on the quantum level, in which energy and mass -do- lose distinction.

So now you are agreeing that potential energy must be included when finding the inertial mass of a compound object on the quantum level, and that potential energy is not just a change in the rest masses of the parts?

How does it make sense to distinguish between the quantum level and the macro-level here? Are you claiming that the inertial mass of a compound object whose parts are not interacting (so there's no potential energy between these parts, like with molecules in a gas) is not just the sum of each part's inertial mass individually?

Also, regardless of whether you think the experimental evidence justifies the claim that the inertial mass of a compound object is proportional to its total energy, do you still deny that this is what the theory of relativity predicts?

You must show that this kinetic energy -adds- to the mass at the macroscopic level and not just state it to be so. THIS, and only this is the only point I am contending. Whether you believe physics is the same at the microscopic level and the macroscopic level is your prerogative. However - I know there is a difference as there is a thing called quantum physics! So unless you are willing to talk about your macroscopic level example, then you'll have to excuse me if I do not respond to your BS!

Are you saying that the mainstream theory of quantum physics predicts that inertial mass is not proportional to total energy? If so, it's you who's talking BS. If you're just saying "quantum physics shows that weird stuff happens when you go from the micro level to the macro level, so maybe one new weird thing could be that inertial mass is no longer proportional to total energy on the macro level, even though the current theory says it would be" then sure, anything's possible I guess. But once again you've shifted the goalposts, since you were clearly arguing originally that learningphysics' understanding of the theory was wrong.

 

[Aer]

Really? Then what did you mean when you said "All this says is that the proton and neutron lose rest mass when they are bound together. This rest mass is referred to as the potential energy since all mass is essentially a form of energy."

You are obviously dense. You started talking about quantum physics while I still had in my mind that we were dealing with the macroscopic world, did you not read where I said right after that:

If I said anything similar to that, it was because you were confusing the issue of whether we are talking about the quantum level or macroscopic level.

 

[Aer]

How does it make sense to distinguish between the quantum level and the macro-level here?

Woah! Quantum physics doesn't behave like we see in the macro world. If we can't agree on even this, then there is no point in using the quantum level example!

 

[Aer]

Also, regardless of whether you think the experimental evidence justifies the claim that the inertial mass of a compound object is proportional to its total energy, do you still deny that this is what the theory of relativity predicts?

It is apparent now that there are differing views on what the theory of relatiivty predicts, even pmb_phy states that in his papers! How can I deny that -no one- thinks relativity predicts something specific when there is no agreement on what it does predict. Their personal belief is beyond my control.

 

[Aer]

quantum physics predicts that inertial mass is not proportional to total energy?

Quantum physics only deals with things in their rest frame - that is why Relativity and Quantum physics are not combined in any way. In the rest frame, at the quantum level - all energy is essentially mass energy as far as my knowledge of quantum physics goes because the distinction between mass and energy is lost at this level.

 

[JesseM]

The conclusion was that mass is proportional to rest energy.

Which quote is that?

"It is not good to introduce the concept of the mass of a moving body for which no clear definition can be given. It is better to introduce no other mass concept than the 'rest mass' m. Instead of introducing M it is better to mention the expression for the momentum and energy of a body in motion."

Yes, but as I've told you a million times, for a compound object the "rest mass" is defined as the total energy divided by c^2 in the compound object's rest frame, which of course includes the kinetic energy of individual components of the compound object in this frame. If this wasn't true, he wouldn't have said that an iron gains mass as it heats up. So this quote is not inconsistent with that one, provided you understand the definition of rest mass for a compound object.

 

[Aer]

Yes, but as I've told you a million times, for a compound object the "rest mass" is defined as the total energy divided by c^2 in the compound object's rest frame, which of course includes the kinetic energy of individual components of the compound object in this frame. If this wasn't true, he wouldn't have said that an iron gains mass as it heats up. So this quote is not inconsistent with that one, provided you understand the definition of rest mass for a compound object.

More like - provided you misunderstand the definition of rest mass for a compound object. I do not agree with the defintion you provide! All energy contributes to an objects mass? Perhaps a photon is not an object, but then - what really is an object? Does a photon have energy? Does it have mass?

 

[JesseM]

Really? Then what did you mean when you said "All this says is that the proton and neutron lose rest mass when they are bound together. This rest mass is referred to as the potential energy since all mass is essentially a form of energy."

You are obviously dense.

Don't be a jerk, Aer.

You started talking about quantum physics while I still had in my mind that we were dealing with the macroscopic world,

Uh, I was responding to your statement "That is not my claim when dealing with masses at the quantum level!" Sounds like you were talking about what is true of the quantum level there, not of the macroscopic world. And I was definitely talking about quantum physics rather than the macro-world--I was asking whether, in the domain of quantum physics, you agree that the inertial mass of a compound object is not just the sum of the rest masses of the parts. In the quote I provided above, it seemed you were still maintaining that at the quantum level the inertial mass of the compound object is the sum of the rest masses of its parts, but that the rest masses of the parts had actually changed. So once again, dealing only with the realm of quantum physics, do you or do you not think that the inertial mass of a compound object is equal to the sum of the rest masses of its parts? If you do, do you think that mainstream physics theories would agree with you on this?

Woah! Quantum physics doesn't behave like we see in the macro world. If we can't agree on even this, then there is no point in using the quantum level example!

You can't just use the fact that some things behave differently on the quantum level to handwave an "anything goes" approach to what happens on the macro-level--quantum physics makes definite predictions about the micro-macro transition, and in some cases it predicts that things do look the same on both levels. For example, it predicts the charge of a macroscopic compound object is just the sum of the charges of all the individual charged particles that make it up. Similarly, quantum physics does not in any way contradict the idea that the inertia of a compound macroscopic object is dependent on its total energy. If you just want to say that the theory could be wrong, fine, but if you're denying that the theory itself says this you're just being ignorant.

Quantum physics only deals with things in their rest frame - that is why Relativity and Quantum physics are not combined in any way.

Yes they are, special relativity and quantum physics were combined long ago by people like Dirac, all quantum field theories incorporate special relativity. It's only general relativity where they haven't been combined, but the question about the inertial mass of a compound object doesn't require general relativity.

 

[JesseM]

More like - provided you misunderstand the definition of rest mass for a compound object. I do not agree with the defintion you provide!

But it's the one Einstein was using, otherwise there's no way to make sense of his claim that an iron gains mass when it heats up.

All energy contributes to an objects mass? Perhaps a photon is not an object, but then - what really is an object? Does a photon have energy? Does it have mass?

Where are you going with this? Of course the energy of a photon contributes to the total energy and thus the inertial mass--if you have a box filled with radiation it will have more inertia than an empty box, that's what's predicted by the theory anyway.

 

[JesseM]

It is apparent now that there are differing views on what the theory of relatiivty predicts, even pmb_phy states that in his papers!

Which paper are you referring to, and what specific quotes are you talking about? I think you've likely just misunderstood something here.

 

[Aer]

Uh, I was responding to your statement "That is not my claim when dealing with masses at the quantum level!" Sounds like you were talking about what is true of the quantum level there, not of the macroscopic world. And I was definitely talking about quantum physics rather than the macro-world--I was asking whether, in the domain of quantum physics, you agree that the inertial mass of a compound object is not just the sum of the rest masses of the parts.

NO! In quantum physics, there is no distinction between mass and energy. As I said - I was talking with my foot in my mouth before as I failed to point out that your example was in the quantum world and not the macro world.

 

[Aer]

quantum physics makes definite predictions about the micro-macro transition

Does it make definite predictions about mass and energy? If so, why is it important to state in quantum physics that at the quantum level, there is no distinction between mass and energy. If this was true at the macro level, why is there this firm statement?

 

[Aer]

Where are you going with this? Of course the energy of a photon contributes to the total energy and thus the inertial mass--if you have a box filled with radiation it will have more inertia than an empty box, that's what's predicted by the theory anyway.

So you are claiming a photon has inertia and thus mass?

 

[Aer]

Which paper are you referring to, and what specific quotes are you talking about? I think you've likely just misunderstood something here.

From pmb_phy's paper:

There is currently an unfortunate trend to ban the concept of
relativistic mass from physics. Why such a trend is occurring is difficult to
say for sure but is probably related to the various usages in certain
branches of relativity. Generally speaking, the concept of proper mass
finds more usage with the particle physics community while the concept
of relativistic mass finds more usage within general relativity and
cosmology.

And:

This is surely due, in part, to a debate regarding the
concept of mass in relativity that has lasted for several decades. 2-12 This debate
concerns the use of relativistic mass versus proper mass as being “the” mass in
relativity.

 

[JesseM]

NO! In quantum physics, there is no distinction between mass and energy.

That certainly isn't true, quantum physicists talk about the rest masses of particles all the time, and they don't talk about the rest mass of binding energy (which again, is just a type of potential energy) or of kinetic energy. It is true that in quantum field theory it is easy for kinetic/potential energy to be converted into mass or vice versa in reactions that create or destroy particles, but if we're talking about chemical reactions or the binding of a proton and a neutron into a deuteron, there is no creation or destruction of particles involved.

 

[Aer]

That certainly isn't true

So now you claim that the mass of a system is not the total energy divided by c^2? Make up your mind!

 

[JesseM]

From pmb_phy's paper:

There is currently an unfortunate trend to ban the concept of
relativistic mass from physics. Why such a trend is occurring is difficult to
say for sure but is probably related to the various usages in certain
branches of relativity. Generally speaking, the concept of proper mass
finds more usage with the particle physics community while the concept
of relativistic mass finds more usage within general relativity and
cosmology.

And:

This is surely due, in part, to a debate regarding the
concept of mass in relativity that has lasted for several decades. 2-12 This debate
concerns the use of relativistic mass versus proper mass as being “the” mass in
relativity.

As I thought, this is just your misunderstanding. The debate over whether to use the concept of relativistic mass is purely an aesthetic one, it's not like people who use relativistic mass will make any different physical predictions than people who don't, any statement involving relativistic mass can be translated into an equivalent one involving only concepts like rest mass, momentum and energy. Since everyone agrees on what relativity actually predicts physically, everyone agrees on the prediction about the resistance to acceleration of a compound object (ie the object's inertia)--no physicist would dispute the fact that relativity predicts the inertia of a compound object is proportional to its total energy.

 

[JesseM]

So now you claim that the mass of a system is not the total energy divided by c^2? Make up your mind!

No, I dispute the claim that "there is no distinction between mass and energy"--by "mass" I meant rest mass, as I made clear in my post. If you mean there is no distinction between the inertial mass of a compound object and its total rest energy, then I agree with that, but I'd say that all mainstream theories predict this is just as true of the macro-world as the micro-world.

 

[learningphysics]

A system can have multiple energies. As you've said, it can have kinetic energy and thermal energy to name a few. One of the energies a system has is mass. That is, mass is a form of energy. So when we add all the energies together of this puddy, we get total energy = mass energy + kinetic energy + thermal energy. In this case, the kinetic energy has been converted to thermal energy - notice that the mass energy is still there. Now answer my question: Does a photon have energy?

In the paper I referred you to... Einstein is defining rest energy of the body as total energy of the body in the center of mass frame. There are only two energies... the translation kinetic energy and the rest energy (this includes thermal energy...nuclear binding energy and anything that is not translation kinetic energy)

His paper shows that a change in rest energy is proportional to a change in rest mass.

Yes a photon has energy.

 

[learningphysics]

Thanks. Please note that I'm not ignoring all this because I'm lazy. I've had horrible back pain when I sit for more than a few minutes. It took a long time to figure out what it was. Turns out that I have a stone in my gall-bladder. It will be comming out when I have surgery in the near future.

I'm really sorry to hear about this Pete. Hope everything turns out well. Take care of yourself. Best wishes!

 

[Aer]

As I thought, this is just your misunderstanding. The debate over whether to use the concept of relativistic mass is purely an aesthetic one, it's not like people who use relativistic mass will make any different physical predictions than people who don't,

Just like I thought, you'd come up with another BS answer.

You can't even keep your arguments consistent! Pick a theory and stick with it. Either all energy contributes to an objects mass or it does not (and I am referring to the macroscropic world here). If you claim that quantum physics is the same regarding mass and energy as is on the macroscopic world, then the mass of an object in quanutm physics would be the total energy / c^2. I don't dispute the latter, it is the former that I dispute. That is - on the macroscopic level, other forms of energy exist other than mass energy.

 

[JesseM]

So you are claiming a photon has inertia and thus mass?

Physicists generally define "inertial mass" in terms of resistance to acceleration in the object's own rest frame, and you can't do this for a photon, although you can do it for a compound system which contains a photon. If you want to define the inertial mass of an object in a frame other than its rest frame, this is the same thing as using relativistic mass, and as you've pointed out many times, most physicists prefer to avoid using this concept.