Is there any anti-gravity material?

Question

I want to know if there is any anti-gravity material. I am thinking of making flying vehicles which are made up of anti-gravity material so that they will not experience any gravity on them and can easily take off and be more fuel efficient. Is there any such thing? Or any workaround?

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Surjya Narayana Padhi

Comments

isn't helium anti-gravity material? it does make balloons define gravity, just because it's gas don't mean it's not material?

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Val

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This is not an answer, just stating that what someone asks about is nonsense does not answer the question.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Dilaton

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Hm.. this makes me remember a video of Feynman where some audience member asked him if there was any way to make an anti-gravity machine, to which he replied: your butt's one such machine.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user nervxxx

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@FrankH, Vineet Menon: Calling something fringe science is worse than calling it garbage in my opinion. However, please elaborate on your answer. Why is it fringe science/gargbage. See for example, Dilaton's answer.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Dimensio1n0

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OP -- have you tried putting dark energy underneath the wings?

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Johannes

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It is not fringe science. It is garbage.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user FrankH

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@FrankH...Let's not say something as pure garbage unless its disproven. In the wiki article, I saw some particle physics stuff something related to graviphotons and fifth force, which I couldn't understand so I'm not commenting...

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Vineet Menon

Answer 1

A from a theoretical physics point of view not completely off the mark approach to anti-gravity effects comes from certain versions of supergravity described in wikipedia, which is a unified supersymmetric point-particle quantum field theory.

Some particular versions of this theory not only contain the "usual" atractive graviton, a spin-2 particle, but in addition a so-called graviphoton is predicted (1). This graviphoton is a spin-1 vector field, interacts with mattar at the normal gravitational strength, and behaves generally like a massive photon. The fun thing about it is that it can give rise to attractive and repulsive forces. The repulsive forces feature can in principle give rise to anti-gravity effects, however the real-world / everyday usefulness of this has not yet been tested ... ;-)

For more see this blog article on Uduality (2).

References:

(1) A model for a light graviphoton, R. Barbiery and S. Cecotti, Zeitschrift für Physik C Particles and Fields, 33(2), 1986, 255-261

(2) Antigravity from Supergravity, Physics blog post on: U.Duality thoughts on the new mathematics and physics, posted 24. November 2012

Comments

I dont know why people have to downvote (again without saying what is technically or physically wrong!) my answer here; supergravity is an accepted mainstream high energy physics theory. Must be non physics reasons then ... -> Not cool, this takes away the fun of posting anything here on this site :-/

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Dilaton

Answer 2

When you say "anti-gravity material", the closest thing I can think of is the hypothetical concept of negative mass:

In theoretical physics, negative mass is a hypothetical concept of matter whose mass is of opposite sign to the mass of the normal matter. Such matter would violate one or more energy conditions and show some strange properties such as being repelled rather than attracted by gravity. It is used in certain speculative theories, such as on the construction of wormholes. The closest known real representative of such exotic matter is a region of pseudo-negative pressure density produced by the Casimir effect.

But it gets more complicated because there are actually three different kinds of mass: gravitational mass, passive grativational mass, and inertial mass:

Thus objects with negative passive gravitational mass, but with positive inertial mass, would be expected to be repelled by positive active masses, and attracted to negative active masses. However, any difference between inertial and gravitational mass would violate the equivalence principle of general relativity. For an object where both the inertial and gravitational masses were negative and equal, we could cancel out mi and mp from the equation, and conclude that its acceleration a in the gravitational field from a body with positive active gravitational mass (say, the planet Earth) would be no different from the acceleration of an object with positive passive gravitational and inertial mass (so a small negative mass object would fall towards the Earth at the same rate as any other object).

In any case, there does not exist any such thing, to the extent of human knowledge.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Graham

Comments

Which is precisely why this is a good question! Why is gravity attractive?? Granted this is more philosophical than physics, it is still on the minds of us theorists.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Chris Gerig

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@ChrisGerig: I have often heard it stated that the attractiveness of gravity is a feature of all spin 2 gauge theories.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Jerry Schirmer

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@JerrySchirmer Why is this so?

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user namehere

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@namehere: I've never seen it adequately proven. But I have heard that statement many times.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Jerry Schirmer

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@JerrySchirmer Oh. That sucks. It would be a very interesting question. Let me post that as a question!

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user namehere

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@JerrySchirmer The proof is in Zee's QFT book in one of the early chapters. It's due to a simple pattern: spin-0 exchange -> universal attraction, spin-1 exhange -> attraction&repulsion, spin-2 exchange -> universal attraction, spin-3 exchange -> attraction&repulsion etc. Then there is a theorem that rules out interacting spin > 2 particles so all that's left is spin-0 (Higgs/pions), spin-1 (gauge bosons) and a single spin-2 (graviton).

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Michael Brown

Answer 3

In the spirit of conspiracies and dubious theories, take a look at the so called Biefeld Brown effect.Some have claimed that Penney's 1965 paper as a possible source of rationalizing their beliefs. I don't know enough to offer an opinion either way. However, Mythbusters et al have obtained negative results in all their experiments.Take it for what its worth.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Antillar Maximus

Answer 4

Instead of going into more recent developments, which others, such as Dilaton already have, I will discuss the general relativistic perspective on this. So, start with the Raychaudhuri Equation:

$$\frac{\mbox{d}\theta}{\mbox{d}\tau}=-\left(\theta^2+\sigma^2\right)-R_{\mu\nu}v^{\mu}v^\nu$$

With $\theta^2$ and $\sigma^2$ are appropriately defined as $\theta^2=\left(\frac{\theta_\mu^\mu}{3}\right)^2$ and $\sigma^2=\sigma_{\mu\nu}\sigma^{\mu\nu}$ and also, under the assumption that the worldline of the centre of energy is completely time-like. Just for the time being, forget about $\sigma^2$.i.e. say that the object is not under any shearat all. $$\frac{\mbox{d}\theta}{\mbox{d}\tau}=-\theta^2-R_{\mu\nu}v^\mu v^{\nu}$$

Now, for there to be any anti-gravitational effect, $R_{\mu\nu}v^\mu v^{\nu}$ must be positive. Whether or not the worldlines go forward in time, or backwards, $v^\mu v^\nu$ must be negative since it is completely time-like, and thus, $R_{\mu\nu}$ must be negative. Now apply the Einstein Field Equation: $$G_{\mu\nu}=\kappa T_{\mu\nu}$$ $$R_{\mu\nu}=\kappa\left({T_{\mu\nu}-\frac{T}{2}g_{\mu\nu}}\right)$$

Thus, the anti-gravity condition imposes the following constraint: $$T_{\mu\nu}<\frac{T}{2}g_{\mu\nu}$$

Taking the trace of the inequation with respect to the Minkowski metric tensor (for fun, or maybe not really), letting $g=g_\mu^\mu$: $$T<\frac{T}{2}g$$ $$g>2$$

A negative time-time component of the SEM tensor is necessary, which isn't permitted in GR.

Answer 5

Forget anti-gravity material. As far as we know, there is none--gravity is always an attractive force. But there is a workaround: Use something with the appropriate properties, i.e. something that does have repelling force. Electromagnetism! All you need to do is separate enough charge, say a few grams of electrons, place half of them at the airport and attach the other half to your flying machine. Off they go with a mighty force that can lift Mount-Everest sized objects to the moon. Simple as that. (Calculation of the force between two 1g clouds of electrons left as an exercise--it's immense!).

Of course, the hard part is getting at a gram of electrons (without any positive charge nearby).

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Jens

Comments

And hey! We have mag-lev trains already!

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Jerry Schirmer

Answer 6

Anti-gravity can be achieved by telekinesis (don't know about anti gravity material)

https://en.wikipedia.org/wiki/Psychokinesis

Comments

This is nonsense, PO deals with graduate-level+ physics. Voting to hide...

Answer 7

Anti-gravity is impossible, as it would let you build a perpetual motion system, as follows.

Assume we have a system in which we can capture the kinetic energy of a falling mass. For example, a ball that falls onto a scooped wheel to drive it. Take the ball and move a sheet of anti-grav material under it. As the ball now no longer feels the earth's gravity, we can push it up above the wheel without using any energy. Now remove the anti-grav sheet. The ball will fall onto the wheel and thus generate energy.

This violates the law of conservation of energy, i.e. the first law of thermodynamics. Hence it is impossible, and hence anti-gavity cannot exist.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user hdhondt

Comments

It doesn't have to violate conservation of energy if moving the sheet needs appropriate amounts of energy. You simply assume it doesn't.

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user Jens

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This is wrong for three reasons. First, you need energy to move the object because it still has inertial mass. Second, the sheet will move. Third, the sheet (planar) will not homogenously shield the gravitational field of the earth (sphere).

This post imported from StackExchange Physics at 2014-03-17 03:59 (UCT), posted by SE-user WIMP