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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?
It's a cool experiment, but it's news once you get the result, not "a few years" before.
Unless they're trying to drum up interest for funding...
Forget thrust, drag, lift and weight. Airplanes fly because of money.
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).
Government cannot make man richer, but it can make him poorer. - Ludwig von Mises
Professor: And the microwave radiation, combined with the gravitons and graviolis from the supernova, blasted us through time itself.
It doesn't-matter.
+1 IDisagreeSoHeMustBeATrollOrAnAstroturferOrAShill
I wish the results were that antimatter falls upwards. If that were true, while it would have no practical use in the near future, it would be a hole in physics that our far descendants could exploit.
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.
Swedish plasma phys. PhD student; MSc EE; knows maths, programming, electronics; finance interest; seeks opportunities
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.
Assorted stuff I do sometimes: Lemuria.org
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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.
He who lights his taper at mine, receives light without darkening me.
What like http://xkcd.com/417/ ?
I wank in the shower.
Antimatter falls strange.
Real Daleks don't climb stairs - they level the building.
One model for anti-matter is that it is a normal particle travelling backwards in time. The energy from a particle/anti-particle annihilation is the energy released by it changing direction under this model. As far as the particle is concerned, it is behaving normally in a gravitational field by falling downwards, but when we look at it from our usual time axis it appears to be falling up.
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.
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".
In a survey of 100 programmers, 111111 thought that duck-typing was a good idea.
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.
Dr. Frank J. Nagy Fermilab Computing Division Authentication and Directory Services Group
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.
Did it really take 65 physicists to decide that the best way to test gravitational effects was a particle beam deflection? I suppose simplicity is nice, but I honestly expected something more complicated with that many collaborators...
Because all the other properties of antimatter that have been tested so far are different unlike every type of normal matter ...
...
This is a Black Swan problem
Theory : All Swans are White
Proof : every swan I see is white, every swan
Problem : Australia was then discovered along with the black swan.....
Puteulanus fenestra mortis
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.
There's an anti-photon ... it's the photon. There's anti-versions of several other particles (antineutrino, antiquarks, antineutron, etc).
What? no. The matter would not follow, it would be repelled. Think of two magnets with north pointing at each other.
Quote:
The idea is to fire a beam of antihydogen atoms at a target and see how much they are deflected by gravity.
That's easier said than done. Creating a beam of this stuff turns out to be remarkably tricky. The problem is that it's easy enough to trap antiprotons and positrons in electromagnetic fields. It's even fairly straightforwad to put them together so that they form antihydrogen. The problem is that antihydrogen is neutral and simply falls out of the trap. So some way has to be found to collect and trap these antiatoms.
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Uh - can somebody explain to me why they need a beam and don`t just take a look if the antihydrogen falls out on the bottom or the top of the trap?
"we are all atheists about most of the gods that societies have ever believed in. Some of us just go one god further."
Um I think you are confused.
First of all they are using anti-hydrogen for two reasons. First of, gravity is proprotional to mass and positrons have a mass of 0.5MeV while protons have a mass of a GeV or so. Thats a difference in mass of a factor of 2000. The second reason is that the electromagnetism is many many many orders of magnitude stronger than gravity, the EM coupling constant is around 1/137 while gravities coupling constant is around 1/ (1.2x10^{19}). So unless the object is electrically neutral, the EM force will vastly dwarf the gravitation force making any measurement extremely difficult (ie impossible practically speaking). Positrons and anti-protons are of course charged, hence you need to combine them into anti-hydrogen.
Secondly it is only clear that the electrons and positrons have the same absolute mass. The formula you are refering is actually E^2 = (pc)^2 + (mc^2)^2 not E=mc^2. Hence you lose sign information.
I fail to follow the rest of your post.
Dr Grom, DPhil (Oxon), Particle Physicist working at CERN (although not on this experiment)
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.
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.
Don't think of it as anti-hydrogen hitting helium. Think of it as an anti-proton hitting a proton that just happens to have another proton nearby.
So, you end up with a bunch of energy and a left over proton (Hydrogen).
And, no, anti-particles only annihilate their partner particles, not just any particle.
...does this mean anti-hydrogen will fall to the ground Yes, because, as everyone knows, the Earth repels normal hydrogen. It all gets pushed out into space where it coalesces to form gas giants.This also explains why cats and babies act so weird. Down where they live they're practically swimming in a sea of anti-hydrogen.
You never really know how close to the edge you can go until you fall off.
http://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter
They missed one option. What if antimatter is not affected by gravity? I'll put my money on falling down.
"How does anti-hydrogen work on life thingies?"
On contact with organic tissues (or pretty much anything else), it will disapear in a burst of highly energetic photons (think gamma rays). So, depending on the dose (approx. ng to kg), it can range from totally harmess to skin burn to radiation poisonning to strategic-grade nuclear explosion.
"Does it have the potential for a destructive chain reaction?"
No, the reaction does not create new antimatter, and the potential energy of the created antimatter is only a very small proportion of the lab electricity bill, at worst, it will probably only blow up their building.
That it doesn't fall at all? Up, or down? That antimatter doesn't interact gravitationally with normal matter in any way. but only with other antimatter?
File under 'M' for 'Manic ranting'
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.
Yes, for practical purposes QM is fine - but it is not enough for understanding. It's like the difference between engineering and science; engineers are good and worthy people, but their focus is practical: the construction of things, the application of knowledge to a practical purpose. The focus of the scientist is on the unknown, the unanswered questions; the practicality of things is not foremost in their mind, they speculate and grope in the dark. These are of course wild generalisations, but the principle of what I just said is sound, at least
And thus I find that the proper scientific attitude to QM is not "Who cares, it works", but "Why does it work?" - there must be something better out there, a theory of which QM is just a special case, an approximation. Scientific method relies, after all, on theories being falsifiable - isn't that, more than anything, the very embodiment of "Why not"?