# Does the inertia of either a Bose-Einstein or Fermi-Dirac condensate

1. Sep 1, 2010

### Phrak

Does the inertia of either a Bose-Einstein or Fermi-Dirac condensate increase linearly with the number of particles?

2. Sep 26, 2010

### inflector

Re: Inertia

Seems like a good question. I'm surprised no one here has an answer.

3. Sep 26, 2010

### ZapperZ

Staff Emeritus
Re: Inertia

Maybe because one doesn't actually measure inertia?

Zz.

4. Sep 27, 2010

### Phrak

Re: Inertia

Zapper, This question is motivated by the work of Carver Meade. To make a long story short--I hope not too short--the collective behavior of coherent electrons obtains a momentum that is directly dependent upon both the induced magnetic potential, A and the charge of each electron-pair within a closed superconductive loop. Each unit of charge is subjected to the total field A generated by the sum of all charges in the system. qA, charge times the magnetic potential is a momentum. As the magnetic potential develops directly proportional to the charge, the momentum is proportional the square of the charge.

In similar fashion, one might speculate that the inertia of coherent atoms in a gravitational field is not proportional to the number of atoms but to their square.

5. Sep 27, 2010

### ZapperZ

Staff Emeritus
Re: Inertia

I still don't know how you propose that one measure inertia of anything. Momentum? Sure. Mass? I've seen those. But "inertia"??????

So you're asking not only a measurement of a quality that I haven't seen done, but a measurement of that quality on an exotic substance! Forget BE condensate. Can you show what is the measurement of "inertial" on a tennis ball?

Zz.

6. Sep 27, 2010

### Phrak

Re: Inertia

Interesting isn't it? Are you an experimental physicist? If so, how could one possibly measure the resistance to an applied force on a bunch of coherent atoms numbering something like 10,000 or so? If you publish, you owe me.

7. Sep 27, 2010

### ZapperZ

Staff Emeritus
Re: Inertia

What does "mass" or "momentum" have anything to do with a quantity of "inertia"? If you want to know "mass" of a BE condensate, then why not ask for mass, and not inertia? If you want to know "momentum" (which is a more well-defined quantity), then why not ask for momentum? Why are we playing with "inertia" in particular?

And how is it that I owe you if I "publish"?

What is annoying here is that I initially thought you had a particular and important angle to this question that I have never thought of. That's why I asked you to clarify what you mean by "inertia". Instead, what I think I'm seeing here is simply a play with words that you obviously haven't thought about. I obviously wasn't as smart as the other members who chose not to respond to your original question.

Zz.

8. Sep 27, 2010

### Phrak

Re: Inertia

I appreciate you animosity Zapper. I earned it.

I should drop the archaic term "inertia" and instead substitute inertial mass. The intent, here, is to make contact with classical force.

But this is all peripheral. Is there an experiment that can be set-up to measure the gravitational mass of a coherent system of particles?

And are you an experimental physicist?

9. Sep 27, 2010

### inflector

Re: Inertia

Well, the reason I thought the question was interesting is that I thought that perhaps there might be some difference between the mass of 10,000 coherent atoms in a BEC and 10,000 non-BEC atoms just like there are differences in the mass of differing combinations of nucleons in a nucleus due to changes in binding energy.

When I read "inertia", I thought this meant inertial mass. What else could it mean? Am I missing some other concept? [EDIT: I was writing my post and missed Phrak's reply above]

Isn't any test measuring force required to accelerate a particle or group of known-mass particles a test of "inertia?" or is there some specific reason that a direct test of inertia is complicated?

I understand why it might be extremely difficult to conduct such a test on a BEC, but what about a tennis ball? Couldn't one just weigh the tennis ball to get it's mass? Or fire it at an instrumented target in a vacuum measuring the velocity optically, and then determine the force the tennis ball exerts on the target over the time of the contact with the ball and then measure the velocity of the tennis ball's bounce optically to determine the energy that was transferred to the target in the elastic collision.

Knowing the velocity of the initial ball and the ball after the bounce, one knows the energy transferred to the target as a function of mass, which combined with the force over time measurement should allow one to compute the acceleration which, in turn, should allow one to compute the inertial mass since F and acceleration is another function of mass which would allow you to solve for mass algebraically. I understand there may be some difficulties getting an accurate measurement because of various factors but it seems like some measurement should be relatively easy to make. What am I missing?

Last edited: Sep 27, 2010
10. Sep 27, 2010

### Phrak

Re: Inertia

inflector, I'm not sure I understand you, however, I am proposing something a little different, I think. I suggest the gravitational mass of 10^n atoms of a tennis ball in a coherent state masses n times the mass of a tennis ball in noncoherence. This would be a really big difference for a tennis ball.

11. Sep 27, 2010

### ZapperZ

Staff Emeritus
Re: Inertia

Please show me the physics that is the impetus for you to make such a proposal. I've worked with superconductors throughout my career, and none of what I've learned have many any proposal that the normal state of the material has a different mass than the superconducting state.

Better yet, show me the Hamiltonian of your system in which the condensate actually gain mass upon the transition into a coherent state.

I don't see why my being an experimentalist or not (and I am!) has anything to do with this. You are making the proposal. Why am *I* being the one under scrutiny? Should I ask if you are a theorist or not, and if you've worked with condensed matter systems, for coming up with this idea?

Zz.

12. Sep 27, 2010

### Pythagorean

13. Sep 27, 2010

### ZapperZ

Staff Emeritus
Re: Inertia

No I'm not, because this paper belongs in the same class as the Podkletnov effect!

Zz.

14. Sep 27, 2010

### inflector

Re: Inertia

Well, that's the opposite direction I was thinking. I was thinking there might perhaps be some tiny drop in mass in a manner similar to the mass decrease for elements up to Fe/Ni. Since physics has one example where combining particles results in reduced mass, I thought it might be possible that matter in a BCE might display a similar reduction in mass.

Since we don't have a non-empirical binding energy formula that can accurately predict nuclear binding energy, there is still much to be learned about the nucleus. If a similar effect were present in BCEs, that might point to new possibilities for theorists to mull over and we might get a less empirical and more accurate theory for nuclear binding energy.

So, despite the difficulties involved in making any such measurement, I still think it would be an interesting experiment.

15. Sep 27, 2010

### ZapperZ

Staff Emeritus
Re: Inertia

But such mass decrease or increase is due to the binding energy. There are no such thing in a BE condensate, especially when it involves neutral bosons.

Zz.

16. Sep 27, 2010

### inflector

Re: Inertia

I should have been more clear. I know that the mass increase is due to the binding energy in the case of nucleons in the atom's nucleus.

And if, as you say, "there are no such thing in a BE condensate," then this implies that the measurement of inertial mass was performed by someone. If that has been done, then it is correct to say that "there is no such thing," within the detectable limits of the experiment. Fair enough, this should not be a surprise to anyone as no theory predicts any such thing.

At the same time, I don't think anyone was expecting that the mass of atoms would not correspond to the simple summation of the mass of the constituent nucleons (and electrons) when this was first discovered. It took a while before this was understood.

If the inertial mass measurement has not been done, then I think it is fair to say that while we have no theoretical basis to believe there would be any such effect, we do not know because it has not yet been measured.

17. Sep 27, 2010

### ZapperZ

Staff Emeritus
Re: Inertia

You made way too big of an assumption. What I said was that in a BE condensation, there are no binding energy. The conglomeration is due purely to quantum statistics, not some physical attraction.

Zz.

18. Sep 27, 2010

### Pythagorean

I was asking inflector. So this paper is pretty much BS?

19. Sep 27, 2010

### inflector

Re: Inertia

Of course, there is no binding energy in a BE condensate, I never thought there was, so I'm sorry to have led you to believe otherwise. I will try to be more precise. I didn't mean to waste your time by confusing things.

If there were binding energy then a reduction in mass would be an expected result of any measurement of inertial mass.

It is precisely because it would be unexpected, i.e. precisely because there is no current theoretical prediction that there would be a difference in mass, that I think the measurement would be an interesting one. Like the vast majority of measurements of this type, it is very likely that no change would be measured.

But it is precisely because there is no binding energy involved that a change in mass would be interesting in the very unlikely event that one was detected.

20. Sep 27, 2010

### inflector

Re: Inertia

ZapperZ is in a much better position to judge that paper. It seems handwavy to me but I'm in no position to judge it on the merits.

I certainly wasn't talking about any effect known, postulated, or otherwise and I am sorry if I implied that I did.

I don't personally think there would be an actual change in mass. I consider this unlikely. So I don't think there would be any effect to measure.

I just think it would be an interesting test to run and then see. In the unlikely event that someone did find something, it would represent new physics and might even earn the experimenters a trip to Sweden. That's why I deemed it an interesting question.

Part of the impetus to the advance of science is when people run experiments and then notice what they didn't expect. So most of the time, you just have boring confirmations of existing theory. But in order to find the unexpected, you need to be confirming the expected on a regular basis.

Making a new type of measurement is more interesting than repeating measurements that have already been done, IMHO, because you are much more likely to find something unexpected when you measure something for the first time.