Thread: Do atoms lose mass as they slow down?

1. When atoms are cooled down to near absolute temperatures do they lose mass? Seeing as they are losing energy?

2.

3. Originally Posted by Quantime
When atoms are cooled down to near absolute temperatures do they lose mass? Seeing as they are losing energy?
Yes, but the amount is so small as to be almost immeasurable.

4. They actually do? Why? Do they loose elctrons or protons or neutrons? What does it have to do with the temperture ?

5. Originally Posted by Wise Man
They actually do? Why? Do they loose elctrons or protons or neutrons? What does it have to do with the temperture ?
Temperature is a measure of the kinetic energy of the system. As it cools there is less energy. Energy is equivalent to mass (e=mc2).

6. That's why you need an infinite amount of energy to accelerate something massive to c.

7. Well the impossibility lies in Einstine's mass formula. It increases when we get close to light speed.

8. Originally Posted by Wise Man
Well the impossibility lies in Einstine's mass formula. It increases when we get close to light speed.
Where is the impossibility?

9. Another bizarre result of E=mc^2 is that shining light insight a mirrored box (so that the light is trapped inside) increases the mass of the box.

10. ... Ok so the photons add kinetic energy to the electrons ( photo electric effect), but what does this have to do with the mass?

11. Originally Posted by Wise Man
... Ok so the photons add kinetic energy to the electrons ( photo electric effect), but what does this have to do with the mass?
It is the energy of the photons themselves that add mass. It has nothing to do with electrons.

Mass and energy are equivalent / the same / interchangeable (E=Mc2).

12. Originally Posted by Quantime
When atoms are cooled down to near absolute temperatures do they lose mass? Seeing as they are losing energy?
Atoms themselves don't cool down. Atoms belong to a collection of stuff which makes up matter. E.g. carbon atoms are what composes coal. When the coal is cooled down then the atoms of the material loose kinetic energy. The loss in kinetic energy is due to a loss in speed. Since mass is a function of speed the individual atoms loose mass as well. That mass loss is not due to a change in the structure of the atom but is a result of the properties of spacetime.

13. Originally Posted by pmb
Atoms themselves don't cool down.
Technically you are right since 'temperature' is defined statistically and so holds little meaning on the scale of single atoms. But this is pedantry.

Originally Posted by pmb
That mass loss is not due to a change in the structure of the atom but is a result of the properties of spacetime.
Since we're not talking about nuclear physics, the 'structure' of the atom refers to the electronic structure which does change when the temperature is varied.

14. A question to nano's response. Is it true that light has no mass?

15. Originally Posted by ampwitch
A question to nano's response. Is it true that light has no mass?
Semantics make this a somewhat dubious question to answer. Light does not have mass (i.e. invariant mass) but it does have relativistic mass.
To a physicist, however, relativistic mass and energy are the same thing

16. Thank You Then is it safe to "assume" the reference was to the work of Max Plank?

17. What reference are you talking about?

18. What I was thinking about, and I apologize if thinking incorrectly, Planck's work that discusses "blackbodies". Given that inference may be way way off. But for learning and inquiry, if you will, please allow the question as a point of reference and departure. Thanks.

19. No, this is quite different to Planck's work on black body radiation.

20. [QUOTE=nano;335697]
Originally Posted by ampwitch
To a physicist, however, relativistic mass and energy are the same thing
Not to me. There are cases where the relativistic mass of an object is not related to its energy by . One such example is when the body under stress where the force of the stress is paralel to the motion of the body. The derivation can be found in my paper on mass at http://arxiv.org/ftp/arxiv/papers/0709/0709.0687.pdf See Eq. (8) and (9)

21. In my question regarding mass of light I referenced Max Planck. To give an example I put my hands very close together. As I moved my left to my right the amount of heat, energy increases and so does it's "mass". You are welcome to try it for yourself. However your conclusions and inferences will be different...obviously. It occurred to me to ask the question of mass of light and as such I might well begin to better understand the mass of energy too???Thanks nano! I haven't read the complete article but will. Again, Thanks!

22. I believe photon doesn't have mass because it was said that Higgs-field doesn't react on photon to create mass. Reference: Inquiring Minds - Questions About Physics

Also people tried measuring photon mass experimentally by measuring inertia/lag in EM wave but not found it.... however they only established the possible upper limit for photon mass . Reference: What is the mass of a photon?

And pmb (post #19) said that inertia-mass is not same with passive/active-mass. Because passive/active-mass can react with gravity, while inertia-mass can only resist momentum change. Reference: http://arxiv.org/ftp/arxiv/papers/0709/0709.0687.pdf
----

So I guess cooled atoms doesn't loose mass. Instead they only loose inertial-mass. -Therefore they have the same rest mass.

23. I have a question: Should we reguard light as a wave or particle? I know that it's actually both and neither, but in problems involving, say, the mass of light, which should we use?

24. Originally Posted by Wise Man
I have a question: Should we reguard light as a wave or particle? I know that it's actually both and neither, but in problems involving, say, the mass of light, which should we use?
Light is massless... therefore it become easy: light is a wave, and a wave obeyed quantum law, and quantum law cause them to behave like particle

25. Originally Posted by Wise Man
I have a question: Should we reguard light as a wave or particle? I know that it's actually both and neither, but in problems involving, say, the mass of light, which should we use?
Neither. (Or both.) It doesn't matter. For example, even in classical (pre quantum physics) light has momentum and energy. Einstein's mass-energy equivalence shows that that energy is equivalent to mass. The only difference that the quantum view makes is that you can calculate the energy (and equivalent mass) of a single photon.

26. Originally Posted by Strange
Originally Posted by Wise Man
I have a question: Should we reguard light as a wave or particle? I know that it's actually both and neither, but in problems involving, say, the mass of light, which should we use?
Neither. (Or both.) It doesn't matter. For example, even in classical (pre quantum physics) light has momentum and energy. Einstein's mass-energy equivalence shows that that energy is equivalent to mass. The only difference that the quantum view makes is that you can calculate the energy (and equivalent mass) of a single photon.
Wave on a rope has momentum too. So the momentum of light is not inherent properties of light but exist solely because of its wave property. -Wave on rope has a momentum and therefore *light* wave in space has a momentum too... this is direct behaviour of wave everywhere anywhere (but this doesn't imply wave has mass).

ie: Phyx 103-0, Waves "All waves carry energy and momentum, just like particles."

27. Originally Posted by pmb
Originally Posted by nano
To a physicist, however, relativistic mass and energy are the same thing
Not to me. There are cases where the relativistic mass of an object is not related to its emergy by . One such example is when the body under stress where the force of the stress is paralel to the motion of the body. The derivation can be found in my paper on mass at http://arxiv.org/ftp/arxiv/papers/0709/0709.0687.pdf See Eq. (8) and (9)

28. Originally Posted by msafwan
I believe photon doesn't have mass because it was said that Higgs-field doesn't react on photon to create mass. Reference: Inquiring Minds - Questions About Physics

Also people tried measuring photon mass experimentally by measuring inertia/lag in EM wave but not found it.... however they only established the possible upper limit for photon mass . Reference: What is the mass of a photon?

And pmb (post #19) said that inertia-mass is not same with passive/active-mass. Because passive/active-mass can react with gravity, while inertia-mass can only resist momentum change. Reference: http://arxiv.org/ftp/arxiv/papers/0709/0709.0687.pdf
----

So I guess cooled atoms doesn't loose mass. Instead they only loose inertial-mass. -Therefore they have the same rest mass.
There is a book out which can explain some of this. Its called Gravity From the Ground Up by Bernard F./ Schutz. In it the author shows why inertial mass density is a function of pressure. Its for a student who knows the basics of algebra.

29. [QUOTE=nano;335829][QUOTE=pmb;335749]
Originally Posted by nano
A troll is defined as follows
Troll (Internet) - Wikipedia, the free encyclopedia)
In Internet slang, a troll is someone who posts inflammatory,extraneous, or off-topic messages in an online community, such as an online discussion forum, chat room, or blog, with the primary intent of provoking readers into an emotional responseor of otherwise disrupting normal on-topic discussion.
That is nothing like my post. My post is about basic relativity. In fact its a homework exercise in Basic Relativity by Richard A. Mould,. 1994. The homework problem reads as follows. From page 296
10.1 A long straight rod of cross section area A and mass per unit length M is at restalong the x'-axis of the inertial system S'. The rod is under tension along is length with aforce F.
(a)...
(b) Relative to the S system, the rod moves along the x-axis with velocioty $\beta$. Show that the value of E in S is equal to . Chek units! Does this reduce correctly when F = 0?
(c)...
The value of E is not related to the relativistic mass by which I calculated in the paper. This is straight textbook physics and its in direct response to the assertion that relativistic mass being the same as energy, it is not as I have just demonstrated with a counter example. Therefore there is no reasoin for calling it a troll.

30. There is every reason to and I stand by it.

31. Originally Posted by ampwitch
A question to nano's response. Is it true that light has no mass?
This question comes up alot. Let me summarize

1) Inertial Mass of Light - Non-zero
2) Rest Mass of Light - Zero
3) Rest Mass Density of Disordered Radiation - Non-zero
4) Passive Gravitational Mass of light - Non-zero
5) Active Gravitational Mass of light - Non-zero

Since this question comes up so often the powers that be decided to make a Physics FAQ about it. Its online at What is the mass of a photon?

32. Originally Posted by pmb
1) Inertial Mass of Light - Non-zero
2) Rest Mass of Light - Zero
3) Rest Mass Density of Disordered Radiation - Non-zero
4) Passive Gravitational Mass of light - Non-zero
5) Active Gravitational Mass of light - Non-zero
I challenge you to find the concepts 1), 4), or 5) applied to photons in any peer-reviewed literature.
Point 2) is correct.
And 3) is a whole new concept that you have made up. Go ahead and give it a Google - the only references to such a concept are forum posts all by pmb.

33. Originally Posted by nano
Originally Posted by pmb
1) Inertial Mass of Light - Non-zero
2) Rest Mass of Light - Zero
3) Rest Mass Density of Disordered Radiation - Non-zero
4) Passive Gravitational Mass of light - Non-zero
5) Active Gravitational Mass of light - Non-zero
I challenge you to find the concepts 1), 4), or 5) applied to photons in any peer-reviewed literature.
Point 2) is correct.
And 3) is a whole new concept that you have made up. Go ahead and give it a Google - the only references to such a concept are forum posts all by pmb.
The term "active/passive gravitational mass" seems to exist. Here I googled it using Google Scholar: [1]

I think "Rest Mass Density of Disordered Radiation" actually meant "vacuum friction" (a real concept: [2]). You know... it is that popular concept of zero-point-energy & "casimir forces" which was observed between 2 metal plate, and also the one about "there exist a minimum wavelenght [of photon] that permeate all space. Virtual photon/virtual-particle popping-up randomly in empty space due to vacuum energy [zero-point-energy]" causing photon pressure. -One can also derive an idea that all this photon actually create another 'mass' for all matter, which is caused by virtual photon pressure: [3]

I think "mass" has many different sources so we can no longer use word "mass" or we going to confuse what mass is really is. (in fundamental sense: mass is measured by its inertia and therefore can be ambiguous. No one can really sure if inertia is == mass)

Reference:
[2] Vacuum has friction after all - space - 11 February 2011 - New Scientist

34. Originally Posted by msafwan
The term "active/passive gravitational mass" seems to exist. Here I googled it using Google Scholar: [1]
Yes, I know that the terms exist (albeit rarely used). I asked for a peer-reviewed article in which those concepts are applied specifically to photons.

Originally Posted by msafwan
I also think "Rest Mass Density of Disordered Radiation" actually meant "vacuum friction" (a real concept: [2]).
Having looked through some of the nonsense pmb has spouted on the subject he does not appear to be talking about vacuum friction (and if he is, why invent an obscure term for it?).

My troll threat level remains at critical.

35. I think you are angry at him for some obscure reason...

36. I'm not at all angry, just bemused.

Science trolls

37. Originally Posted by msafwan
I think "Rest Mass Density of Disordered Radiation" actually meant "vacuum friction"

That wasn't what I had in mind. Thing about the CMBR. It consists of photons which are moving in random directions. Therefore if you were to transform to the frame of reference where the average momentum density of the radiation was zero and select out an imaginary cube then find the energy inside the cube then divide that energy by the forum of the cube then you'd get the energy density of radiation where the momentum was zero. In this sense you can say that the radiation has rest energy. In the sameseens you can say that it has rest mass, although the rest mass would depend on the pressure of the radiation since mass density is a function of pressure.

38. Originally Posted by nano
I'm not at all angry, just bemused.

Science trolls

That is a link to a page in which you speak of non-scientists. That doesn't apply to me because I am a physicist. Besides, that thread wasn't recieved that well. First off you don't know what peoples credentials are here. Just because you don't understand why people research what they do it doesn't mean that there isn't good reason for it. There is a very good reason I researched my article and wrote it. You just didn't ask me.

And I am a trained and educated physicist. If I did have family illness/emergency I would have been able to complete my MS in physics. I used to work as one thiugh. Right not I'm just disabled due to spinal cord damage. And yoiur use of the term troll is incorrect.

You don't know me from a hole in the wall so I ask you not to pass judgement on me.

Note: While I was disabled I helped proof read Edwin F. Taylor's text on black holes and I wrote the glossary to it.

39. Originally Posted by pmb
Originally Posted by Quantime
When atoms are cooled down to near absolute temperatures do they lose mass? Seeing as they are losing energy?
Atoms themselves don't cool down. Atoms belong to a collection of stuff which makes up matter. E.g. carbon atoms are what composes coal. When the coal is cooled down then the atoms of the material loose kinetic energy. The loss in kinetic energy is due to a loss in speed. Since mass is a function of speed the individual atoms loose mass as well. That mass loss is not due to a change in the structure of the atom but is a result of the properties of spacetime.
I am aware of that, thank you for your input.

PS Lets stick to the topic at hand please gentlemen lets not let this become a battle of the egos. However easy, or tempting that it can be

40. Originally Posted by nano
Originally Posted by msafwan
The term "active/passive gravitational mass" seems to exist. Here I googled it using Google Scholar: [1]
Yes, I know that the terms exist (albeit rarely used). I asked for a peer-reviewed article in which those concepts are applied specifically to photons.
I don't know of any off hand. I don't exacty choose articles to read for the terms they contain and the articles I do read I don't take note of certain terms like that.

However I do have a GR text by Hans C. Ohanian where he speaks of the mass density of radiation. Alan Guth gave me a set of his lecture notes for the his Early Universe course. He explains in those notes that light has mass density according to its energy density. The Feynam lectures explains the bending of light in a g-field due to the light having mass according to its energy. Tolman's text speaks of it too. Section 110 of his text reads [The gravitational mass of disordered radiation.. I don't worry myself about things as trivial as whether I know off hand or usages where those terms apply to light or not. A world renown expert set me straight a few years back and explained to me what those terms mean and told me when they apply. Now I'm careful of them and I notice them in my travels. Eg. the mass of radiation as a source is found in Peacock's Cosmology text and how it depends on both the energy denbsity and pressure of the radiation.

41. Originally Posted by Quantime
I am aware of that, thank you for your input.
You are very welcome.

Originally Posted by Quantime
PS Lets stick to the topic at hand please gentlemen lets not let this become a battle of the egos. However easy, or tempting that it can be
You're quite right. I'm human so when someone claims I'm trolling I tend to defend myself. Its only the natural thing to do. But we're all very different people so we don't all react in the same way. I've said my peace.

42. Edit: Delete

43. An example of an ad hominem argument would be to say that you've spouted nonsense because it's you who said it. Whereas I'm actually calling it nonsense because it is intrinsically nonsensical; it makes no difference who wrote it.

I'm not going to get into a slanging match about it though. I will duck out, content in knowing that those with any real knowledge of physics will recognise that I'm right.

44. MODERATOR WARNING

Let's keep the personal arguments out of this discussion. This is the physics forum.

45. Originally Posted by MeteorWayne
MODERATOR WARNING

Let's keep the personal arguments out of this discussion. This is the physics forum.
Wayne, you forgot to mention that it's fine to get personal on this forum as long as you state that it's merely how someone 'comes across'. See below.

Originally Posted by nano
Originally Posted by MeteorWayne
Originally Posted by nano
Originally Posted by MeteorWayne
Originally Posted by nano
Originally Posted by MeteorWayne
I'd strongly suggest you cease attcking pmb personally, and stick to refuting the arguments. You come across as a stalker, whether that's true or not.

I'd also suggest you read the Forum Guidelines.

Moderator Meteor Wayne
I call him a troll (based on evidence) you call me a stalker (based on none). Remind me what the forum guidelines say on flaming?
I didn't call you a stalker, I merely stated how you come across, AND I did it in a private message. Please heed my advice

MW
To state that something is X is to say that that something comes across as X, since you cannot know anything beyond your own senses. So claiming that I'm 'a stalker' or that I 'come across as a stalker' is really equivalent. Furthermore, why does the fact that it's a private message make a difference? Does flaming not apply to PM'ing?

Until the above is resolved I decline the advice.
I'm sorry but stating that someone IS something is not the same as explaining how you come across.

You are absolutely right, I'm sorry. In the future then, on your command, I will prepend 'you come across as...' to anything I say that may be construed as being offensive. For instance, you come across as a pathetic, frightened, creep who has no power or significance in the real-world and so exercises an illusion of power on this rather illusory world wide web. That of course is not my opinion of you nor a statement of fact, merely a warning of how you come across.
Good day.

46. That was in a PM, which you should not have posted. Enjoy your vacation.

P means PRIVATE

47. Oooh you're buying me a holiday as a way of apology? There's really no need.

48. Have a great 'vacation' nano!

There's still one concept I do not comprehend: Atoms loose kinetic enery when they slow down, but how exacly does it affect the mass? Kinectic energy is a form of energy, it's not matter.

49. Originally Posted by Wise Man
Have a great 'vacation' nano!

There's still one concept I do not comprehend: Atoms loose kinetic enery when they slow down, but how exacly does it affect the mass? Kinectic energy is a form of energy, it's not matter.
The gain in mass as the speed changes is a result of the properties of spacetime. That is to say that it can be derived using the Lorentz transformation. Relativistic mass is what we're talking about here, not the mass that is intrinsic to the particle, i.e. not proper mass. Relativistic mass is defined as the m in p = mv = m0v/sqrt(1 - v^2/c^2). Since a change in velocity causes changes in velocity the result is an increase in m

The derivation is on my website at Inertial Mass

I wrote up an explaination on the mechanism for the change in mass. See Weight of a Moving Body

Einstein referred to matter as that which causes the stress-energy-momentum tensor to be non-zero. A body at rest has energy so that's matter. If the body increases its kinetic energy then the tensor becomes more and more non-negative with every increase in kinetic energy. The kinetic energy of light is what causes the light to have non-zero active gravitational mass.

50. Originally Posted by pmb
The kinetic energy of light is what causes the light to have non-zero active gravitational mass
And, presumably, why light has momentum, even though it has zero rest mass?

51. I hope that this question makes sense. If fusion is the end result of of a "slow down" of an atom then wouldn't the mass increase?
I hope the question isn't to out of context. Thanks!

52. If fusion is the end result of of a "slow down" of an atom then wouldn't the mass increase?
It's not.

53. Okay, Thanks

54. Originally Posted by KALSTER
Originally Posted by pmb
The kinetic energy of light is what causes the light to have non-zero active gravitational mass
And, presumably, why light has momentum, even though it has zero rest mass?
Inertial mass is what gives light momentum. Inertial mass m is related to velocity v and momentum p through the relation p = mv. For a photon v = c so p = mc or m = p/c. The relation between the energy is E = pc or p = E/c. Substiture into m = pc to get m = (E/c)/c or m = E/c2. For a photon E = hf so that the inertial mass of a photon is m = hf/c2.

55. Originally Posted by ampwitch
I hope that this question makes sense. If fusion is the end result of of a "slow down" of an atom then wouldn't the mass increase?
I hope the question isn't to out of context. Thanks!
Fussion is when the nuclei of two or more nuclei join together or "fuse" to make one nuclei. See Nuclear fusion - Wikipedia, the free encyclopedia

56. The fusion question was if/then only hypothetical. Yes, pmb your link was useful and as you know correct. So if I may reason it--using the inertial mass equation used by pmb, to the question to think of "how" "... atoms lose mass as they slow down"-
in physics is it just a question of acceptance?

57. Originally Posted by ampwitch
The fusion question was if/then only hypothetical. Yes, pmb your link was useful and as you know correct. So if I may reason it--using the inertial mass equation used by pmb, to the question to think of "how" "... atoms lose mass as they slow down"-
in physics is it just a question of acceptance?
In physics there is a debate on whether relativistic mass (RM) is useful or not and whether it ought to be taught. An examination of the latest versions of relativity texts show that there is a majority of texts which teach relativistic mass. The article stating this data is found online at [physics/0504111] On the Use of Relativistic Mass in Various Published Works

The author calculates the followng in the section labeled Quick Summary

Number of special/general relativity (SGR) texts examined = 100 (data set)
Number of SGR texts in data set which used RM = 63
Number of SGR texts in date set which don't use RM = 37

Number of relevant physics texts examined = 643 (data set)
Number of relevant physics texts in data set which use RM = 476
Number of relevant physics texts in data set which don't use RM = 158

So clearly its used a lot.

58. Originally Posted by Kerling
Ehm, no.
I don't understand. No what?

Originally Posted by Kerling
From statistical physics it becomes appearent that near zero temperature an ensemble of particles at zero temperature is all in it's ground state. Now this is dependent on whether it is bosonic or fermionic. But let's for now assume that at zero temperature it is in its lowest energy state. Then this is just an energy state. described by the hamiltonian of the system. And how does this hamiltonian look like? Well all hamiltonians are but assumptions. But what if we were to take into account all possible terms, and not care about the qualitatative effects of each term?
I don't understand .. again. What does this have to do with the mass of an atom?

Originally Posted by Kerling
Well then at zero temperature nothing really stand still. Effective mass is majorly different from it's normal mass.

Originally Posted by Kerling
But in the end, the 'weight' doesn't change. Signigicantly that is.
The OP didn't ask if the mass changed signigicantly, he just asked "do they lose mass?" and they do. The weight also changes since the weight of a body also depends on its velocity (speed to be precise). Here is the opening post
When atoms are cooled down to near absolute temperatures do they lose mass? Seeing as they are losing energy?
Originally Posted by Kerling
HE jku, he just asked it ihehThere is some energy taken away from the system to cool it down, and yes this could be seen as mass when it comes down to general relativity.
This subject is almost always spoken of in terms of special relativity. There is no need to bring general relativity into it.

Originally Posted by Kerling
But effectively this is unmeasurable, and hence non of our conceirn.
Actually it is measureable. There was an article in the American Journal of Physics on this subject and about measuring it at low speeds. The article is Relativistic mass increase at slow speeds, Gerald Gabrielse, Am. J. Phys. 63(6), June 1995

Einstein himself wrote an article on this matter. The article was called On a Method for determination of the transverse and the longitudinal mass of the electron, A. Einstein, Annalen der Physik 21 (1906B): 371-384

In the end this is confirmed everyday in cyclotrons since measuring relativistic mass is simply verifying the cyclotron formula p = mv = qBR where q is the charge on the particle, B is the magnetic field and R is the radius of the circle that the charged particles move in.

59. Originally Posted by Kerling
@pmb, With no I meant 'probably not so much' to the original question. Mass isn't as easily definable as you'd think. Mass is more or less a measure of how hard it is to accelerate a certain volume.
I disagree. As Newton defined mass it was the the ration of momentum to velocity, i.e. mass is defined so that momentum is conserved. The greater the mass of an objet the harder it is to accelerate it.

Originally Posted by Kerling
About the answer to the OP, let's keep it physical. 'Do they lose mass? ' yes, 'do the measurably lose mass?' No. And that is an important difference for the basis of science is for statements to be falsified by experiment. If it cannot be falsified it isn't scientific. And hence if an effect is known to be intrinsically unmeasurable the effect doesn't occur.
I disagree. It is an emperical fact that the atom weighs less withe decreaseing speed. Because its so small doesn't mean that its not measureable. Its just that nobody knows how to measure it today.

Originally Posted by Kerling
Special relativistic only have to do with the changes in speed. 'Weight' and hence 'gravity' are the domain of space-time curvature, and hence general relativity.
That's a common misconception. All that is required to weight a body is a gravitational field, not spacetime curvature. Spacetime curvature is just another term for tidal forces and one only needs a gravitational force and not gravitational tidal forces to measure something. In fact the equivalance principle states that a uniform gravitational field is equivalent to a uniformly accelerating frame of reference so all you realy need is an accelerating frame to measure weight. E.g. if you were in a rocket in interstellar space and the rocket engines were firing at the rate of 1g then you'd equivalently be in a uniform gravitational field and could weight the object.

60. Originally Posted by pmb
I disagree. As Newton defined mass it was the the ration of momentum to velocity, i.e. mass is defined so that momentum is conserved. The greater the mass of an objet the harder it is to accelerate it.
I don't see how our statements are different.

Originally Posted by pmb
I disagree. It is an emperical fact that the atom weighs less withe decreaseing speed. Because its so small doesn't mean that its not measureable. Its just that nobody knows how to measure it today.

misconception. All that is required to weight a body is a gravitational field, not spacetime curvature. Spacetime curvature is just another term for tidal forces and one only needs a gravitational force and not gravitational tidal forces to measure something. In fact the equivalance principle states that a uniform gravitational field is equivalent to a uniformly accelerating frame of reference so all you realy need is an accelerating frame to measure weight. E.g. if you were in a rocket in interstellar space and the rocket engines were firing at the rate of 1g then you'd equivalently be in a uniform gravitational field and could weight the object.
This is annoying my comments have been removed by accident.

Okay, in short look up the expression of mass for relative speeds. You'll see clear as day that for non relativistic speeds the difference in mass are of the order of a single quanta. Near zero temperature atoms move about ten orders of ten slower. At low temperature the speeds are so low that the quantum state uncertainties, or fluctuations are many many many orders of ten larger then relative mass. It doesn't matter how far we will advance in technology. it isn't measurable.

A gravitational field, requires a gravitational potential. This is the domain of general relativity, as far as I know because I haven't separated the two for years. However it isn't relevant at all for this problem. All Solid state theories and statistical theories can (easily) be made relative. And most actually already are.
In short the most important energy contribution are in the nucleis. Which are (unless they are excited) in the ground state, this energy and the vibrations and rotations of the nucleis is the main causer of 'mass' in the atom. 'Temperature' isn't at all affected by the behaviour of the nucleis.

Also the article you mention by Gabriels, has speeds of 0.03 times c. You need accelaration for that, or cosmic particles. Hardly near zero temperature...
Also using a synchrotron to define mass near zero is a bit, well, weird. Since they are essentially Ionized by high temperature.

Do they lose mass near zero temperature? Answer: Not measurably.

61. Originally Posted by Kerling
Originally Posted by pmb
I disagree. As Newton defined mass it was the the ration of momentum to velocity, i.e. mass is defined so that momentum is conserved. The greater the mass of an objet the harder it is to accelerate it.
I don't see how our statements are different.
Because your definition uses m = F/a which isn't valid whereas mine use m = p/v which is always valid. I really should have said "harder to change its momentum".

Do they lose mass near zero temperature? Answer: Not measurably.
You keep saying doesn't matter how far we will advance in technology. it isn't measurable. even after I showed you that it's already been done. I.e. Relativistic mass increase at slow speeds, Gerald Gabrielse, Am. J. Phys. 63(6), June 1995.

Besides, you assumed that the particles initial velocity wasn't relativistic to begin with. Had it been then your point would be moot. On what basis do you assert that the initial speed wasn't relativistic?

Regarding gravity - I mentioned a gravitational field because you raised the subject of weight. And you don;t need a potential to mesure weight. One usually weighs a body at zero potential anyway. It doesn't really matter since I was countering your assertion that the weight doesn't change and to address that one needs to talk about gravity. So it was you who really brought it up.

BTW - How did all your posts get deleted?

62. The post deletions were my fault. A misapplied button, and too quick a trigger finger on the enter key.

Newbie Moderator!!

63. Originally Posted by Kerling
Okay, in short look up the expression of mass for relative speeds. You'll see clear as day that for non relativistic speeds the difference in mass are of the order of a single quanta. Near zero temperature atoms move about ten orders of ten slower. At low temperature the speeds are so low that the quantum state uncertainties, or fluctuations are many many many orders of ten larger then relative mass. It doesn't matter how far we will advance in technology. it isn't measurable.
Okay. I see the flaw in your arguement now. For some odd reason you have it in your mind that the speed change is from one near zero temperture speed to yet another one. That wasn't what the OP asked about. Recall the opening question again
When atoms are cooled down to near absolute temperatures do they lose mass?
This means that the initial speed was not near absolute zero temperature but was, perhaps in his mind, a temperature near ordinary temperatures, say room temperature. The final speed was then a speed according to near zero, That change certainly is measureable according to that paper.

64. I see the flaw in my own explanation. When I sought to explain temperature near absolute zero, I assumed the matter to be condensed. And all your reasonings are with (ionized) very dilute gases. And in my reasoning I haven't sought after the possiblity of dilute gases that are not in a condesed state. If that is indeed the matter then interatomical interactions are neglectable, and then yes the mass decrease due to speed is indeed measurable and noticable. This is in agreement with the article you proposed, considering the ion's coulomb repulsion of these, even in dilute gases this repulsion prevents any part of the gases to become of a quantum nature. In such cases yes you can state that mass is lost near zero temperature.
However these cases don't really occur in (biological) nature. (then again, neither do low temperatures :P)
In all other cases (in physics there is basically condensed and non condensed matter) the quantum effects are of importance. All solid and liquid matter has molecules or atoms that move with incredibly low speeds. Even in room temperature the speeds are at best correlated with the diffusion equation (since brownian motion). And they are minute. At least 10 orders of 10 lower then the speeds that are discussed in the paper.
Therefore my arguments mentioned above hold perfectly well. And the mass of condensed matter near zero Kelvin is unmeasurable changing.

Explaining the mass change by relativity speeds is about the same as explaining how cars break using air brakes. Sure, some use it, and it does indeed work. But only well at speeds which in normal life are never found. The purpose of the article is to show that mass changes in relativistic speeds can be found. About the same as proving that it is possible to break a car using an airbreak. It isn't a great example on explaining how cars break (or how mass behaves near zero temperature).

Also in the general tone, it isn't an odd reason to have such thinking in my mind working as a solid state theoretical physicist. Also your second remark would in most cases imply that speeds of particles change from high to low. This only happens during accumulation. And in most normal cases a drop in temperature from a 'fast' gaseous phase to a slow soild state passes a liquid phase. Judging from the full spectrum of possible temperatures (zero to the critical point) then yes, from critical to zero particles lose mass. For however all substances the loss of mass practically stops at the moment the substance reaches a state of condensed matter. :P

65. It's quite possible that the OP had no idea about what his question implied. He may simply have in mind that when atoms are cooled down then, on average, slow down and with that in mind he might simply wanted to know it the inertial mass of a particle descreases when the speed decreases.

It's always hard to tell what a person has in mind when they ask a question.

You and the OP might like to read the following article

Apparatus to measure relativistic mass increase, John W. Luetzelschwab, Am. J. Phys. 71(9), September 2003
An apparatus that uses readily available material to measure the relativistic mass increase of beta particles from 204T1 source is described. Although the most accurate analysis uses curve fitting or a Kurie plot, students may just use the raw data and a simple calculation to verify the relativistic mass increase.
Its interesting in that students can do this in a lab.