# Does something like anti-gravity exist, in theory?

1. Oct 16, 2004

### JV

Does something like anti-gravity exist, in theory? I mean two masses repeling each other. Or in terms of space-time: an upward curving.
And if so, does that result in anti-mass?

2. Oct 16, 2004

### pervect

Staff Emeritus
The idea of negative mass certainly exists, and is sometimes known by the name "exotic matter". It's physical existence is somewhat uncertain at this point, though there are regions of negative energy density due to a quantum mechanical effect known as the Casimir force.

Regions with a negative energy density would have a negative space-time curvature and repel any matter near them, just as regions of postive energy attract matter.

Note that near a large mass of matter, both positive and negative mass objects would fall "down". Near a large quantity of negative-mass (exotic matter), objects would fall "up".

The reason that negative matter would fall "down" near the earth can be described in a couple of ways. One way is this - the principle of equivalence says that a negative mass object would have both a negative inertial and gravitational mass. So it would be repelled by a nearby massive object, but it would move towards the repulsive force, because of it's negative mass.

The other way of explaining why a negative mass would fall down is the prpinciple of equivalence. Heavy objects fall at the same rate as light objects, they both follow geodesics. The situation with negative mass objects would be no different - they'd fall at the same rate as anything else.

3. Oct 17, 2004

### Wave's_Hand_Particle

QUOTE=JV]Does something like anti-gravity exist, in theory? I mean two masses repeling each other. Or in terms of space-time: an upward curving.
And if so, does that result in anti-mass?[/QUOTE]

Lets take some simple examples:
Yes, if one does some simplistic calculations for Black Holes, one can see that for certain quantifiable products near the Local Horizon there exists a segment where one can cross into the inner Horizon or one can be deemed to be "hovering" at a location just outside, this can be deemed as "anti-gravity" by another observer at a far away location who is looking in the direction of the Blackhole.

All speculation of course, but there is evidence from Relativity, just being inderstood.

Then there is the product which Einstein spen many days pondering, the REPULSIVE GRAVITY, products known as Gravity Repulsion. The Einstein Field equations state that the Stress Energy Tensor can evolve into actions that are opposite to normal Gravity, 'positive attractive MASSES '.

The simplistic view is that there are Negative regions where the fabric of Space (NOT SPACETIME), expand and contract in response to the Vacuum Field, Quantumly these are bits of Energy that are Electro-Magnetic, or FLUX. Now at a certain limits portions of Flux resonate in phase, this is what Einstein introduced as the Cosmologic Constant, and matter and Gravity are attracted in a positive manner via regeons of Spacetimes. But external to Spacetimes there is just Space, or Vacuum, this area can be very unstable, as the Positive energy and Negative energies flit in and out of existence, mostly as <-> and <+> which cancel each other out, which gives stable Flux, or background to Space.

Now when the products expand further by the location of two <-> <-> negative bits of space they deviate out of equilibrium, and are exponential greater in size so <-> becomes <-->..next evolving into expanding regeons
<---->....<-------->, this is the Negative Repulsive Force know to be causing the Accelerated Expansion of intervening Space of the Universe.

One can almost state that Universe has stopped creating matter, and as matter is condensing less, space is expanding greater, eventually the expansion will surround the remnant 'Universe' matter, crushing matter out of existence,(from the outside in, contraction) and will invoke a Gravitational reversal..or Big-Bang, where the Universe is turned around 'inside-out'(expansion) and the whole process cycles on...

P.S if one asserts a NEGATIVE region of space to be a Blackhole, then one piece of Positive matter will allways be attracted to this region, and thus a small black hole just out side the Earths Atmosphere will surely attract the Earth, and not the other way around, things on the Earths surface would catagorically Fall up!..towards the Blackhole, or negative region.

4. Oct 19, 2004

### JV

This seems a strange statement to me. I would expect that all the objects (both BH and earth) will fall toward the center of gravity. The earth also has an attractive force on the BH.

This would be a way for us to simulate anti-gravity. Take a BH near the earth and objects will fallup. So will this in formulas mean that there is a negative region on earth?

5. Oct 19, 2004

### garytse86

is dark energy causing some sort of antigravity effect, thats why the rate of expansion of our universe is getting much faster.

6. Oct 19, 2004

### pervect

Staff Emeritus
I don't think it's at all correct to view a black hole as having negative mass. It has a positive mass.

I belive it's true that the space-time region outside a black hole can have a negative mass density (energy density) due to quantum effects.

However, the net mass of a black hole is still positive.

A similar situation exists with the Casimir effect I mentioned. The region between two conducting plates has a negative energy density. The plates themselves, being made out of matter, have a positive energy density.

7. Oct 19, 2004

### ZapperZ

Staff Emeritus
Y'know, it warms the cockles of my heart that in this thread, and a couple of other previous threads on "anti-gravity" that were eventually moved into the TD section, no one, including the quacks, mentioned anything about the Podkletnov effect. The thought that this thing is finally on its way into oblivion that even cranks don't remember it, well, it just leaves me feeling all warm and fuzzy.

:)

Zz.

[Drat! Of course, now *I* had to spoil it by mentioning about the damn thing!] :)