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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."
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
... why should antimatter be any different? In fact every particle with mass yet measured behaves the same way in gravity. I can't see any reason why antimatter should be any different.
An experiment that reduces doubt. Does that work for you?
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.
The original theory did not need it, but it predicted the universe was expanding, and conventional wisdom at the time said this was not the case... so Einstein add the constant to get a steady state universe ...
....
... so it was put back ...
...
Then Hubble found the universe was expanding so Einstein took it out again
Then the inflational big bang model and observations that the current expansion of the universe was accelerating seemed to require it again
This is why experiments need to be done
Puteulanus fenestra mortis
There's an anti-photon ... it's the photon. There's anti-versions of several other particles (antineutrino, antiquarks, antineutron, etc).
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)
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.
http://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter
Holes are a virtual particle with no mass, whereas anti-matter has mass. Electrons actually exist, but holes are simply a place where an electron can fit. Take the example of a helium balloon in a car: if you slam on the breaks, it flies to the back of the car because all the air is rushing forward, and the balloon's relative vacuum gets pushed backward. A hole behaves similarly. Antimatter, on the other hand, has mass just like its matter counterpart and therefore isn't directly comparable to a hole.
Uh, no, actually, they don't. Because F=Gmm'/r (m being the mass of one object, and m' the other, G being the gravitational constant and r being the distance between them), and a=F/m (acceleration equals force divided by mass). When you substitute one for the other, you get a=Gm'/r - which is completely independent of the mass of the object being observed. Now, you could argue that (as you seem to) that the earth is also accelerating towards the other mass, leading to what seems to be a higher rate of falling - but (contrary beliefs about relativity aside), you can't really treat all of the acceleration as relative in that manner - that simplification of relativity only works for uniform motion - it is possible to detect acceleration (although you can also replace it with a gravitational field, but that would then invalidate our original formulas - can't change horses in mid-stream like that).
"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.
Why did you bother posting this? Honestly. "Here's why I, a non-physicist, think is wrong with this plan." What hubris. If you want to know how the experiment is going to be performed, read the abstract! It's quite readable, and even has pretty pictures and diagrams.
Those who advocate genocide deserve every protection afforded by law, and none afforded by common human decency.
the experiment only shows that, under a certain set of conditions, antimatter behaves a certain way.
You've only removed all doubt if you expect every single possible type of antimatter to behave the same as antihydrogen.
You can extrapolate from the observed behavior, but as we've seen time and time again, there are plenty of edge cases & fringe behaviors that are completely unanticipated.
[Fuck Beta]
o0t!
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.
You've got gravitation wrong I'm afraid. The feather and the moon pull on each other and both accelerate towards the common center of mass (which obviously is almost exactly the center of the moon, since it is far more massive). The force of the moon's pull on the feather is small, but since the feather is also not very massive, it accelerates at 1.62 m/s2 towards the moon. A dropped rock will experience many times more FORCE, since the gravitational attraction between the moon and rock are (comparatively) larger. However, this force has to overcome the rock's equally greater inertia, meaning that the rock also accelerates at 1.62 m/s2 towards the moon. The only real difference is that the rock-moon gravitational center is slightly closer to the rock, than to the feather.
Make sense?
Jeremy