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Does Antimatter Fall Up Or Down?
KentuckyFC writes "There are enough loopholes in the general theory of relativity to allow antimatter to fall up rather than down in a gravitational field. We've never been able to make enough of the stuff to do the experiment. But at the European particle physics laboratory at CERN, where scientists have been refining the technique for making antihydrogen, researchers are designing an experiment called AEGIS that will finally settle the matter. The idea is simple — fire a beam of antihydrogen atoms and watch which way they fall — but the details are fiendish (abstract). The answer should help solve a number of important conundrums such as why there is so little antimatter in our part of the universe and what the value of the cosmological constant is."
Or will it settle (or unsettle) the anti-matter?
According to GR, gravity is the curvature of Space-Time. As the anti-matter moves through space it has to follow this curvature. If it does not, that means GR is wrong (which may be the case, but I doubt this experiment will disprove GR).
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Professor: And the microwave radiation, combined with the gravitons and graviolis from the supernova, blasted us through time itself.
It doesn't-matter.
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Maybe from the Millitary - "A beam of Antimatter you say... no known armour would stop it you say..."
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my relativity teacher told his class, is a function of time: At first, it was non-zero, then people said it was zero, then it might be non-zero after all.
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And science is all about the difference between "I think..." and "I've tested..."
If it behaves exactly as predicted, you can make another mark and continue. If not, you've found something potentially very important.
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Antimatter *could* be different because the mathematics of GR allow it, and we haven't actually done the experiment before. I wouldn't put much faith in human intuition in these matters, considering how counter-intuitive entire GR is...
;-)
I mean, we see water falling off edges of waterfalls etc. Why should the edge of the world be any different?
Shouldn't that mean that matter-antimatter annihilation would result in no energy being emitted? If antimatter had negative mass, the net mass converted to energy would be zero.
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Antimatter falls strange.
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Gravitons are like photons: simply distortions in the underlying field. When two masses move relative to each other, the change in position corresponds to a change in the force between the two, but this change isn't communicated instantaneously. Instead the change travels as a distortion in the force-field - ie. a graviton (or several, as the case might be). This is what it means, intuitively at least, when they say that "the graviton mediates the force of gravitation"; and the same goes for the other mediators of force: photon, gluon and W- and Z boson. The perceived conflict is an artifact of limitations in the viewpoint of quantum mechanics.
The gravitational field as a scalar field surperposed on a flat space-time is just another way of describing gravitation - the curved geometry of general relativity is a better model, although it is more difficult to get a handle on. Perhaps it would be worth trying to tackle the other forces in the same way, as geometry in some sort of space-time. Perhaps we can even derive quantum mechanics as a special case of such a model; mathematics has certainly come a long way since the time of Einstein and Bohr, and it isn't unreasonable to hope that we are now approaching a situation where we can solve those old problems, that neither had the tools for.
If that were true, while it would have no practical use in the near future
Not necessarily - Merely opening that particular conceptual door would lead to a massive influx of funding and revisited anomalous past results.
Interesting thing about experimentation, even the most honest of researchers tends to throw away "bad" results (in the sense of not publishing them, not in the academically-dishonest sense of omitting them from the data). If the scientific community suddenly accepted the possibility of spooky-effect-X, you can bet that dozens or even hundreds of research groups would dredge up their past efforts to see if effect-X explains their results.
Case in point, l'Acedemie des Sciences and meteorites. Up to the turn of the 19th century, only idiots would dare claim that rocks could fall from space... Until the scientific community decided they could, at which point a huge body of past evidence appeared practically overnight supporting the existance of such falling objects.
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Just a few technical details to sort out, first :-)
...and, of course, if your antimatter-powered airship crashes, the phrase "Oh, the Humanity!" is going to be even more applicable. Maybe without the "the".
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As I rememeber, this has already been tested by drifting positrons down the length of the SLAC accelerator tube and measuring the beam deflection due to gravity (at least 20+ years ago).
Yes, anti-matter does fall down just like matter.
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It is my distinct impression that what they mostly do is start from a classical physical model, which is then "quantified" by putting it through the magical transformation, where the classical Hamiltonian is turned into a differntial equation. I have no idea why this is done, nor have I ever met anybody who could explain it convincingly; but it seems to work. It is of course by no means a intellectually satifying method, which is what makes me wonder why nobody seems to seriously do anything about it. It is also, in my opinion, one of the reasons why quantum mechanics has always been plagued by quasi-religious mumbo jumbo like the Copenhagen interpretation.
It falls sideways, just to screw with those smarmy scientists.
There are enough loopholes in the general theory of relativity to allow antimatter to fall up rather than down in a gravitational field.
Uh, no there are not. Gravity (or geometry, same thing in the theory) depends on mass energy in General Relativity. Stuff (with mass energy) follows the metric (the local geodesic). Even photons (which are their own anti-particles) follow the geodesic - and that has certainly been tested. Equivalence principle tests also show that different sorts of nuclear matter (including neutrons) individually follow the geodesic. Anti-matter certainly has mass energy, and (with matter) can be converted to photons and is no different in the theory. In other words "there is only one type of geodesics and there are no antigeodesics for antimatter."
The original article talks about "flavors" of General Relativity. Ain't so such beasties. Period. If you go to the real original article, you find a proposal for a 1% test of the equivalence principle for antimatter, and no such claims of flavors. Now, the equivalence principle has been tested to better than parts per trillion, and part of the mass energy in ordinary matter is made up of antimatter (in virtual particle pairs), so (based on the experimental evidence) I would claim that this test will be negative and is not actually that interesting as new physics. (The articles say that these older tests are "model dependent," but they are not model dependent enough to matter for this.)
That doesn't mean that this shouldn't be done (everything should be tested in physics, and different tests are always useful), but the prediction of General Relativity is clear : if anti-matter has anti-gravity, then General Relativity is wrong. The experimental evidence is also clear : this isn't going to be accurate enough to matter. Will make for some good public relations, though.
You mean apart from all of the air in-between you and the target?
It's not science. Even doing a nice bunch of calculations and saying "Well this shows that anti-matter should do this," is not science, or at least not the important part. Science is testing beliefs by experiment. So regardless of what we think anti-matter will do, and regardless of how sure we think we are, we still need to test it. That's how science works. You come up with an idea, you test it. If the test falsifies it, you come up with a different idea and test it. If the test supports it, you come up with more tests to try and falsify it.
Through this process, we come to understand the natural world, and come to be fairly certain that our understanding is correct. Math and theoretical work is great, but actually testing those theories is what makes science what it is.
So even if we are 99.999999% certain that our calculations are solid and anti-matter does something, we still need to test it. There are plenty of things that we've been certain about that, when we tested it, turned out not to be the case.
Publicity is especially important in quantum physics because we don't know if they are working or not working until they are observed.
Layne
I think that the parent means that neutral bosons have no antiparticles. While neutron is a barion and thus has an antiparticle composed of (~u ~u ~d) quarks, neutral bosons (such as photon and Z0) do not have corresponding antiparticles.
Yeah, like that time this Jesus guy found an overflow in the kill process routine, and was able to resurrect himself after 3 days.
I heard God banned him for 3,000 years.
This discussion is rather academic, however, as one of the largest problems with antimatter is creating and containing enough of it to be useful for experimentation. Creating and storing enough antimatter to be useful in a weapon is probably reserved for science fiction exclusively. H-bombs are much more efficient to produce, and equally useful as weapons---which is to say, not very.
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Sorry, this is all silly.
"Anti-matter" is not the opposite of matter. It is matter with opposite charge or other opposite properties. Mass has no opposite. It is there, or it isn't. (Or it is and then it isn't and then it is and then it isn't, on the level of quantum fluctuations of the gravitational field.)
And no, a hole isn't "anti-matter". It's merely a void in the surrounding matter. It rises because of a principle known as "buoyancy" which is really the gross action of the matter surrounding it causing pressure differentials as a function of distance from the CM. As long as the surrounding matter can flow, it can fill any displacement of the void, and the mass will tend to move down rather than up, and the void will therefore appear to tend to move up rather than down.
And no, hot-air balloons don't rise because of the heat, they rise because they make the air in the balloon less dense than the air outside the balloon. How they do it is not relevant. A rigid balloon and a vacuum pump would work, too.
Are they? Ever seen evidence of one? Gravitons are a purely theoretical construction and, worse of all, one that does not work. While you can construct a quantum field theory of gravity it does not work to arbitrary energies. You have to impose a cut-off threshold and since there is no valid reason for doing so the theory is broken...hence all the theoretical activity trying to reconcile GR and Quantum mechanics.
The gravitational field as a scalar field surperposed on a flat space-time is just another way of describing gravitation
You mean a vector field since gravity has direction, rather than the Tensor field of GR.