Fraser just issued a post regarding the diffuse x-ray background. Apparently a prolonged Chandra view of a tiny region revealed ~ 600 discrete sources, ...most likely black holes, they concluded.
I'd like to see each of those discrete sources checked to see if they're RRAT's. RRATS(Rotating Radio Transients) were discovered serendipitously by Maura A. McLaughlin et al...University of Manchester, England...Sky&Tel, March 2006,p. 18. Neutron stars can emit short bursts of radio waves...typically summing to 0.1 to 1.0 second per day..in bursts of 2-30 milliseconds each. Intervals bewteen bursts are ~ 4 minutes to 3 hours. Good stuff, Maura...kudos. Pete.

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A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

I'd like to see the development of an antimatter-wave interferometer, initially proposed by T. J. Phillip (1997), (using ortho-positronium) for use in determining the gravitational acceleration of anti-matter, the experimental determination which has yet to be achieved.

Gsquare

I have often thought it would be really cool to find some way to discover whethr anti-matter experiences gravity the same way that normal matter does. My guess is that science has guessed right, and there is no difference between electrons and positrons gravitationally, but it has never been tested.

An alternate test might be to look at where the neutral anti-Hydrogen atoms get annihilated after they form in the traps that create them. If they rise, perhaps they are being repelled by gravity. I'm not sure how you could set up the experiment to measure acceleration.

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Forming opinions as we speak

Why do these have to be off of the Earth?

How about getting two metals, of the type they use in a wet cell battery, and see which fruits are best at generating electricity. (I once saw a kit where the managed to power a clock by sticking electrodes in a potato)

How about putting a huge dollop of vanilla ice cream in coffee instead of cream, to see how yummy that tastes.

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Moderations in purple

Fame, glory adventure, a cyber warrior craves not these things.

I think they used a Penning trap to measure properties of the anti-proton during the years 1990-92...showing it identical to the proton except in charge. I'll check references on it. (more homework). Pete.

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A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

You're correct...not yet resolved experimentally....(that's why I think it would be exciting).
Thanks for the response Anton.

The problem with the strength of 'stray' charges being so much greater than gravitational coupling was what initially threw too much uncertainty into any 'free fall' experimental set-up. Neutral antimatter would resolve that problem, but other hindrances appear to have remained.

Great idea. I hadn't thought of that since I was unaware of the recent developments in antihydrogen trapping. Apparently, there has been recent ability to trap using magnetic field interaction with the Antihydrogen's dipole field.
However, what is the lifetime of AH ?...It seems to me that would be one determinant of success. I know that low energy AH has been produced to have sufficiently cold antiH. But my only other concern is the trajectory in the trap. Does the trappng mechanism cause circular oscillation like in a Penning trap.? Can it stabilize the AH sufficiently to analyse the 'free fall'?. It seems to me the strength of that behavior would preclude gravitational measurement with any accuracy just as it has with other particles. Another question is isolation from the electronic 'side effects' from other charges, as I mentioned before...IOW, aren't there Anti-protons in the same trap?

However, semms to be a good idea that may simply require futher refinement.
I will get to the advantages of using atomic (anti)matter wave interferometry in another post which circumvent these issues.

G^2

BTW. Here's the AH trap. http://physicsweb.org/article/world/...pro5%5F10%2D05
Depending on the strength of the field and the trajectory in the trap, it seems as if you ought to be able to simply rotate the trap from horizontal to vertical and test your idea. However, that's probably only wishful thinking.

I'm not certain I like this. Maybe (probably, in fact) I just have a poor understanding of helicity, but I don't see why passing a neutrino in motion would make it appear different. After all, moving past the particle doesn't change your axes, nor should it change the angular momentum measured along an axis. Could you explain this for me (or point me in the direction of something that does)?


As to experiments, there are two I've often wanted to see done.

The first is a bit silly, but it's perhaps easy enough. I really wanted to do it in high school, and I guess it's never lost its appeal You take two big masses (say, 1000 kg each), hang them by strings really close together, remove air, and eliminate electrical charges and magnetic attraction. Measure their deflection, and if you've designed the apparatus well, it will now mostly be due to gravitational attraction. Try to calculate G accurately.
F * d^2 / (m1 * m2) = G
If d is around 0.001 m, m1 and m2 are around 1000 kg, then we get
F * 10^-6 * 10^-6 ~ 10^-10
F ~ 10^2 N
Fg on a single one of those masses is about 10^4 N, so it's quite possible you'd be able to observe some deflection. I think longer strings makes it easier... anyway, I did the math once in high school, and it seemed to me then that there'd be enough of a deviation that one could get a pretty accurate measurement of G.


The second experiment I'd like to see is one to determine if gravitational attraction occurs via mass, or via number of particles. This hopefully isn't as silly as it sounds. Usually when we measure gravity, it's on a cosmic scale, and the bodies are more or less neutral. But would 10^30 electrons actually cause less of a gravitational force (or space-time deflection or whatever) than 10^30 protons? Does the mass really matter, or is it more about the number of particles?

Maybe this one has been done, or maybe the answer is known indirectly. I don't know. I just know that all I've ever seen is the assumption that mass means gravity (including in relativistic treatments), and never an actual experiment to show it.

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"It's turtles all the way down."

Wonderful idea! And it should be relatively easy to perform: doing the Cavendish Experiment, using balls of frozen hydrogen first and balls of frozen deuterium next, for example.

The most sensitive comparison would be between tritium and helium-3 (which has one electron more), but unfortunately tritium is radioactive, and helium won't solidify under normal pressure, so one would have to use containers.

In the late nineteeth century, C V Boys made
accurate determinations of G using quite
small apparatus. But yes, its good to see the
effect itself which is why I floated the idea
of a small particle Quincunx being used if
one can be constructed to produce an exact,
repeatable normal curve before the gravity of
a large body is put beside it. BTW I think
more than string is needed to hang 1000Kg
balls!

John Walker did a similar experiment for gravity here

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"What you think you thought you saw you did not see." Agent J, MiB - Manhatten Bureau

Hello, Peteshimmon. I meant to get back to you earlier about the Quincunx idea.

Your idea may very probably be workable.
However, it reminded me of a fellow some years ago who had thought he had found evidence of a 'fifth' force,( a close range 'repulsive' gravity force), by experimentally placing a container of water next to a large mass (a mountain side cliff). He place a hollow sphere in the water just below the surface and, keeping the temperature perfectly contsant (along with various other controls), monitored its movement in the water over a period of time.

He had worked out all the calculation so brilliantly and controlled the water so precisely, etc. so that no outside influences or thermal currents could affect it, and walla! The sphere actually showed a slow but consistant drift at a certain drift velocity in the direction AWAY FROM the mountain mass! Obviously, a repulsive gravitational force!

I hated to have to write him a letter explaining his obvious omission from the standpoint of basic physics and annihilating his hope of changing physics for ever, but I did ! A classic case of not seeing the forest for the trees!

Would you (or anyone here) care to guess what physics principle which WAS ACTUALLY RESPONSIBLE for the movement away from the mountain??

G^2

You haven't told me enough about the experimental setup, or pointed me to a description of it, but, assuming that the hollow sphere was held underwater by a wire, but was otherwise less dense than water, then the force could have been gravity, pulling the water. This is analogous to what happens to helium balloons in a car when it goes around a corner.

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Forming opinions as we speak

You raise an interesting point. I thought that instrument sensitivity might be a limiting factor, and isolating the instrument from terrestrial effects, EM, etc, might help, making putting the device in orbit advisable. Using your suggestion, though, it may be able to make a Casimir device with much larger plates than we could put in orbit, and perhaps achieve a higher S/N ratio than would feasible with an orbiting experiment.

Sakharov raised this possibility in the 60's (gravitation arises from matter's interaction with the vacuum) and I think the only way that this could be true is if there is a dynamical interaction allowing vacuum to be polarized by the presence of embedded matter. If such an experiment could demonstrate vacuum polarization, it would be a watershed in cosmology.

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The ether of general relativity therefore differs from that of classical mechanics or the special theory of relativity respectively, in so far as it is not 'absolute', but is determined in its locally variable properties by ponderable matter.

Albert Einstein, "On the Ether", 1924

Google on "CERN" and "ATRAP" and you will see that a critical test of the Weak Equivalence Principle is planned, using cold neutral antihydrogen - a critical improvement over the use of positronium, although there are many hurdles to overcome.

Edit: gsquare, I just read through post #36 and see that you have already addressed this. Dumb turbo! aways read the entire thread first!

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The ether of general relativity therefore differs from that of classical mechanics or the special theory of relativity respectively, in so far as it is not 'absolute', but is determined in its locally variable properties by ponderable matter.

Albert Einstein, "On the Ether", 1924

Exactly;
simply a case of bouyancy applied from the horizontal direction.
The hollow sphere had a 'density' such that it stayed perfectly balanced (afloat) just beneath the surface (no need for strings).

The cliff gravity created a density gradiant in the water toward the mountain and so the hollow sphere experienced 'horizontal bouyancy' away from the mountain. Archimedes rules again! No need for repulsive gravity.
He, he.

Amazingly, it was published in a pier reviewed journal; and the author, even after having been informed of his omission, still didn't 'get it'!

G^2

Hello Turbo-1;
Thanks for the reply.
In actuality, it seems to me that putting it in orbit in this case would not be advisable, not for sensitivity reasons but because of the nature of the quantum vacuum.

Any device that is in orbit is, in effect, in free fall;...meaning it is essentially in an inertial frame. The zero point vacuum has been shown to be Lorentz invariant (see T. Boyer); thus in orbit we would expect to see no directional difference in energy between the plates in any direction.

However, upon the surface of the earth, the Casimir plates are in an accelerated frame (non-inertial) and thus would be expected to reveal a directional dependency if in fact Casimir is gravitationally (or mass) related.

However, a comparison of a (possibly null) orbital result with that of earth based could be revealing.

I see you are well read. I agree that is a good starting point.

Gsquare

Yes I did follow the work 20 years ago looking
again at the Eotvos null result. I was always
puzzled as I had old articles by Dicke et al
who were proud of improving the accuracy by
two orders of magnitude at Princeton in the
early sixties. The Experiment you mention was
at some place called the Palisades was it not?
It was good that old classical stuff was
looked at very carefully in case something
was missed. BTW two lovebirds on a perch in
a cage is a good way of seeing the verical
shift going round a corner

I have a reason for requesting the orbiting experiment. I have a reason to believe that vacuum polarization is not dependent on the inertial frame in which it is measured. This is an ATM idea, so I will go no further in explaining it.

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The ether of general relativity therefore differs from that of classical mechanics or the special theory of relativity respectively, in so far as it is not 'absolute', but is determined in its locally variable properties by ponderable matter.

Albert Einstein, "On the Ether", 1924