Anti-gravity

Related Topics:
Anti-Gravity_Boy

Anti-gravity is a hypothetical means of countering or otherwise modifying the effects of gravity, typically in the context of spacecraft propulsion. Such systems are limited to the realm of science fiction given the current understanding of the way gravity works, but this has not stopped legions of hopefuls from making various spinning disks and magnets in hopes of perfecting such a device.

Anti-gravity in the context of mainstream physics

Newton's Law of Gravitation considered gravity to be a force between two objects, causing attraction in proportion to the objects' mass. Under this interpretation, an object with negative mass would repel ordinary matter, and could be used to produce an anti-gravity effect. Alternatively, depending on the mechanism assumed to underlie the gravitational force, it may seem reasonable to postulate a material that shields against gravity or otherwise interferes with the force. An example of such a material, cavorite, is a major element in H. G. Wells' famous book, The First Men in the Moon, although cavorite isn't consistent with even a Newtonian view of the universe (it causes violations of conservation laws). Neither negative-mass exotic matter nor a gravity-screening material have been observed experimentally. While the potential existence of exotic matter is still debated, general relativity presents persuasive arguments against the existence of screening materials.

Einstein's theory of general relativity, published in 1915, supplanted Newton's model of gravity with an entirely different mechanism - one based entirely on the geometry of the universe. Gravity was no longer a force at all, but simply the consequence of the local slope of the universe in a direction the human eye cannot see: a fourth spatial dimension. Under this model, gravity in a universe containing only matter with positive mass is purely attractive. No arrangement of ordinary matter can produce an anti-gravity effect. Spacetime geometries corresponding to true anti-gravity in general relativity require negative mass.

Some models of anti-gravity claim to derive from general relativity.

The model of gravity proposed by the theory of general relativity breaks down under extreme conditions (too far inside a black hole, and in the very early life of the universe under the big bang model). The rapid expansion of the early universe (cosmic inflation) has been verified by the WMAP result, however no satisfactory explanations have been found as of 2006. Galaxy rotation problem is a case where the Spiral galaxy rotation observations do not fit well with traditional gravitation theory. Most physicists believe that at extremely high energies, gravity and the other fundamental forces unify, which would allow gravity to be manipulated in ways that are not readily apparent now. Candidate models for this regime are theories of everything, which attempt to model all four forces (example: string theory), and theories of quantum gravity, which attempt to produce a model of gravity that is consistent with quantum mechanics, though not necessarily unified with the other forces.

Some models of anti-gravity claim to be based on quantum gravity models, though the connection of these to mainstream quantum gravity models is often tenuous.

Conventional effects that look like anti-gravity

Magnetic levitation suspends an object against gravity by use of electromagnetic effects. While visually impressive, this is not an anti-gravity effect.

Critics of various alleged anti-gravity devices often suggest that unusual effects observed around them are due to electromagnetism.

A tidal force causes objects to move along diverging paths near a massive body (such as a planet or star), producing effects that seem like repulsion or disruptive forces when observed locally. This is not anti-gravity. In Newtonian mechanics, the tidal force is the effect of the larger object's gravitational force being different at the differing locations of the diverging bodies. In Einsteinian gravity, the tidal force is the effect of the diverging bodies following different paths in the negatively curved spacetime around the larger body.

Large amounts of normal matter can be used to produce a gravitational field that compensates for the effects of another gravitational field, though the entire assembly will still be attracted to the source of the larger field. Physicist Robert L. Forward proposed using lumps of degenerate matter to locally compensate for the tidal forces near a neutron star.

The accelerating expansion of the universe due to dark energy is an effect that causes a large-scale repulsive force. However, this is not gravitational in nature, and so is not anti-gravity.

Anti-gravity in the context of non-mainstream physics

The United States government and aerospace contractors publicly announced ambitious Manhattan project-style goals to crack the anti-gravity problem during the mid-1950s while the atomic airplane was on the drawing board, but by the end of 1957 no more information was flowing into the newspapers and magazines.

According to the aviation trade publication Interavia, solid progress in this area of research, referred to then as "electro-gravitic propulsion," was an established fact by 1956. "In this particular line of research, the weights of some materials have already been cut as much as 30 percent by 'energizing' them. Security prevents disclosure of what precisely is meant by 'energizing' or in which country this work is under way," the magazine reported. "A localized gravitic field used as a ponderamotive force has been created in the laboratory. Disc airfoils two feet in diameter and incorporating a variation of the simple two-plate electrical condenser charged with fifty kilovolts and a total continuous energy input of fifty watts have achieved a speed of seventeen feet per second in a circular air course twenty feet in diameter." The most successful research was said to have been conducted by Thomas Townsend Brown. Brown is known for his early interest in unidentified flying objects (UFOs).

In the 1990s, a Russian emigre scientist Eugene Podkletnov reported gravity shielding with spinning superconductors. Podkletnov claims he saw tobacco smoke rise over the spinning superconductor, so he measured the gravitational acceleration above the device and made the discovery. Podkletnov now claims to have created a force beam that is 200 times stronger than his first experiments.

NASA, Boeing, and BAE Systems have all funded Podkletnov reproduction experiments, with little to no results. According to 1, Boeing denies 2002 funding at the time of the 2002 Nick Cook article.

Another American scientist, Ning Li, independently predicted a gravity shielding effect with superconductors at nearly the same time as Podkletnov's announcements. In 1999, Li and her team appeared in Popular Mechanics, having constructed a working prototype to generate what she describes as "AC Gravity". The device is known as the high temperature superconducting disc. Li acknowledges that to 'release' the device before knowing that it is indeed functional and not an unexplained aberration could cause a situation similar to the now refuted cold fusion discoveries. http://www.popularmechanics.com/science/research/1281736.html

In November 2005, the United States Patent and Trademark Office (USPTO) granted Boris Volfson, an American inventor, for an anti-gravity device. According to Robert Park, Volfson's device amounts to a perpetual motion machine, defying the laws of physics.^*.

The implications of such a device are not often taken into account when its application is considered. For example, a perpetual motion machine would be capable of accelerating a small mass to relativistic speeds. This implies that a tennis ball sized payload could attain such a high velocity that it would be capable of destroying a planet given enough time to accelerate. Even if a sufficiently advanced civilisation was capable of creating the device, it would surely be limited by the laws of physics to subluminal speeds. A craft equiped with the device travelling at 0.9999999c could easily be destroyed by a microscopic dust particle. Although repulsion technology may be capable of removing the obstacle, it would still place a great force upon the craft generating the repulsion, otherwise it would violate the conservation of momentum.

References

"Anti-Gravity and the Unified Field", Edited by David Hatcher Childress, (1990) Adventures Unlimited Press, Stelle, Illinois ISBN 0-932813-10-0. (A collection of pseudoscientific essays, including The Vortex Arena by John Walker, How I Control Gravity by T. Townsend Brown and Anti-mass generators in UFO Propulsion by Kenneth W. Behrendt)
"Toward Flight without Stress or Strain...or Weight," Interavia, Vol. XI, No 5, 1956, pp. 373-374.
"Electro-gravitic propulsion," Interavia, Vol. XI, No. 12, 1956, p. 992.
Cook, Nick, The Hunt for Zero Point, New York: Broadway Books, 2001.

External links

Mainstream antigravity

Gyroscopic Antigravity on NASA's "Common Errors in propulsion" page
Gyroscopic Superconducting Antigravity news item on unverified tentative result of European Space Agency (esa) research on gravity and superconducting gyroscope

Non-mainstream antigravity

As the effects described by the following links haven't been unambiguously replicated or described in peer-reviewed journals by people other than the effects' proponents, they are often claimed to be pseudoscience. Proponents of these anti-gravity models in turn often claim that they are dismissed out of hand without attempts at replication by the mainstream scientific community.

Gravity | Science fiction themes | Warp drive theory

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