What is antigravity? How would it possibly work?
Welcome to PF, Quantumnumber.
Short answer: It doesn't exist, and it can't possibly work.
Well, you know what gravity is, no ? Think of THAt and then imagine "the opposite"...
Nope, this concept violates all fundamental (and other) principles of "physics".
Might I ask why you are wondering about this ? What triggered this line of questioning ?
Since "antigravity" isn't really a scientific terrm, it is tough to really say what it is. Depending on how you read the term, an airplane could be an anti-gravity machine.
How is that ?
I would say "anti gravity" has a quite straightforeward definition, no ?
You need to invest energy to "beat" gravity, which is ofcourse always the case. Anti gravity does NOT exhibit this "property".
According to General relativity in order to have something with "Anti gravity" it has to have negative mass and that breaks the laws of physics.
Yes but i see no need to go all the way up to GR, the same fact is valid in classical physics as well.
I have to agree with Russ in that any aircraft is something that overcomes gravity. So is a person, if he jumps up in the air.
The OP seems to be referring to something that negates gravity, which is an entirely different animal. How do you 'uncurve' space?
The gravitational force is a vector with a specific direction. By opposite do you mean a vector of opposite direction? That would simply be called gravity in a different direction.
Anti-gravity could hardly be an opposite of gravity. It would have as an effect the obsolescence of gravity, but that gives you no information as to how it would work. You would need data to support your belief it is the 'opposite' of gravity. Of course, to get such data you would need first to acknowledge some things escape the human mind - even yours - and humbly consider all potential answers.
Arrogance has no place in Science. And I though Inquisition was a dead method of Religion. Why try to ressurrect it in Science?
if i jump into the air, i am creating a force that temporarily negates gravity. by defenition am i creating anti-gravitational energy? possibly, but anti-matter as an energy wave does not exist and is impossible.
Well... antimatter does in fact have the same DeBrogie matter wave signatures as regular matter... just reversed. It still does not generate antigravity. 'Negative mass' would be required for that.
Doesn't that depend on which way one wishes to go?
There are a large number of threads on topic of antigravity--many different views presented (and many differ models on how it would work)--here are links not locked:
In a few years experiments at CERN may provide experimental evidence on topic.
I thought in classical physics anti gravity was possible.
Someone asked me about it!
I am not sure, or what would that be?
Moreover, we don't know yet how quantum gravity would work. It might hold such bizzare concepts like antigravity or even negative mass.
you are not negating gravity, you are overcoming it. theres a difference.
In Newtonian physics, anti-gravity is a theoretical possibility: after all, in Newtonian physics, not much distinguishes the gravitational interaction from the Coulomb interaction. It is sufficient that there's a sign flip in one of the two "Newtonian" masses: the gravitational active or passive mass. That said, one must still find some "stuff" that does this.
However, the principle of equivalence in "Newtonian speak", which states essentially that the inertial, gravitational passive and active masses are identical, makes this harder to realise. It is still possible to consider negative masses in principle, unless you introduce a principle where this is not possible. But negative inertial masses are strange things: they also invert all other forces and lead to paradoxial situations.
Finally, in classical general relativity, anti-gravity is not really possible, because it would allow you to distinguish between "gravitational" and "anti-gravitational" reference frames, something which is disallowed for in GR. Unless you relax that condition in GR (which destroys its entire buildup), such a thing cannot happen. There have been attempts at such a construction, recently one of which it was shown that it failed, in Phys. Let. B 639 (2006) 667–669...
Of course, you can still have "exotic states of matter" with funny energy-momentum tensors in which gravity could be seen as kind of "repulsive", but I wouldn't call that "anti-gravity". And, again, one still has to show that such stuff exists.
so Basically, we need to disprove some fundemental laws of physics in order to create "negitive mass" thus anti-gravity.
we all must remember, laws have been disproven.
but which one of us will disprove it!?!? HAH!
Well when a person jumps gravity is still acting apon that person. So in that case that object or peson has not got rid of gravity. Its just caused a net counter acting force on gravity.
There is a prediction that anti-gravity effects will be seen when experiments are conducted to unite mass asymmetrical matter + antimatter isotopes (with electrons removed)--such as the situation of matter helium-3 + antimatter deuteron. This is a hypothesis that is open to experimental falsification and mathematical analysis. Perhaps such experiment will be conducted in future at CERN, until such time, existence of anti-gravity is an open question. I have never seen a mathematical attempt to falsify this prediction--if one is known--please provide reference.
Edit: replaced anti-matter with anti-gravity
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