What is antigravity? How would it possibly work?

  • #1
What is antigravity? How would it possibly work?
 

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  • #2
Danger
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Welcome to PF, Quantumnumber.
Short answer: It doesn't exist, and it can't possibly work.
 
  • #3
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What is antigravity?

Well, you know what gravity is, no ? Think of THAt and then imagine "the opposite"...

How would it possibly work?
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 ?


marlon
 
  • #4
russ_watters
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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.
 
  • #5
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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".

marlon
 
  • #6
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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.
 
  • #7
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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.

marlon
 
  • #8
Danger
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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?
 
  • #9
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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 ?


marlon

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?
 
  • #10
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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.
 
  • #11
Danger
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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.
 
  • #12
Ivan Seeking
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You need to invest energy to "beat" gravity, which is ofcourse always the case. Anti gravity does NOT exhibit this "property".

marlon

Doesn't that depend on which way one wishes to go? :biggrin:

Negative mass propulsion

It has been shown that is theoretically possible to create a continuously propulsive effect by the juxtaposition of negative and positive mass and that such a scheme does not violate conservation of momentum or energy. A crucial assumption to the success of this concept is that negative mass has negative inertia. Their combined interactions result in a sustained acceleration of both masses in the same direction. This concept dates back to at least 1957 with an analysis of the properties of hypothetical negative mass by Bondi, and has been revisited in the context of propulsion by Winterberg and Forward in the 1980’s.

Regarding the physics of negative mass, it is not known whether negative mass exists or if it is even theoretically allowed, but methods have been suggested to search for evidence of negative mass in the context of searching for astronomical evidence of wormholes.
http://www.nasa.gov/centers/glenn/research/warp/ideachev.html#neg [Broken]
 
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  • #13
Rade
What is antigravity? How would it possibly work?
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:
https://www.physicsforums.com/showthread.php?t=33239&highlight=antigravity
https://www.physicsforums.com/showthread.php?t=126823&highlight=antigravity
https://www.physicsforums.com/showthread.php?t=118641&highlight=antigravity
https://www.physicsforums.com/showthread.php?t=107722&highlight=antigravity
https://www.physicsforums.com/showthread.php?t=31245&highlight=antigravity
In a few years experiments at CERN may provide experimental evidence on topic.
 
  • #14
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Yes but i see no need to go all the way up to GR, the same fact is valid in classical physics as well.

marlon

I thought in classical physics anti gravity was possible.
 
  • #15
Might I ask why you are wondering about this ? What triggered this line of questioning
Someone asked me about it!

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.
I am not sure, or what would that be?

http://www.space.com/businesstechnology/060215_technovel_antigravity.html

Moreover, we don't know yet how quantum gravity would work. It might hold such bizzare concepts like antigravity or even negative mass.


http://www.nexusmagazine.com/articles/antigravity.html
 
  • #16
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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.
you are not negating gravity, you are overcoming it. theres a difference.
 
  • #17
vanesch
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I thought in classical physics anti gravity was possible.

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.
 
  • #18
taylaron
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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!
 
  • #19
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.
 
  • #20
Rade
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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  • #21
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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.

that came out wrong. what I was trying to say is it all depends on what you would call antigravity. last sentence should be anti-gravity not anti-matter.

If you think about gravities effects as the balls sinking into the trampoline, antigrav would be a ball under the trampoline pushing upwards and forcing all the other balls to roll away.

If the theory of gravitons zipping back and forth between two objects is true, what would an anti- gravity version of a graviton do? fly away and disappear? cancel out gravitons? fly in the opposite direction of its normal counterparts?

If somebody on earth were to create 'anti-gravity', wouldn't it immediately fly out into space and seek a point of 'zero-gravity'?

i dont think its possible
 
  • #22
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We can't assert that it is impossible, as modern theories have not yet concluded the chapter of gravity.
 
  • #23
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I read somewhere the US military invest about $1million per year into antigravity research just so no one else finds it first. I personally think they're wasting their money.
 
  • #24
disregardthat
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Haha, that's USA for ya!

They invested 100 million dollars on researh of training a cat to spy on the russians. The cat went and fetched mice as it saw them. The US scientists removed a part in it's brain so it wouldn't feel hunger, therefore not catching mice. They put it out for testing in Russia, guess what? The 100 million dollar cat was run over by a truck X|

If antigravity excist, it is far more excotic than we are to discover it on earth, or in near space...
 
  • #25
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Right after the atomic bomb, anti-gravity was supposedly the germans second development goal in world war 2
 

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