Anti-gravity facts for kids
Anti-gravity is a super cool idea about creating a place or object that is completely free from the pull of gravity. It's not about floating in space because you're in free fall or orbit, and it's not about using magnets or air to lift something. Anti-gravity is a popular concept you often see in science fiction stories. Think of "Cavorite" in H. G. Wells's The First Men in the Moon or the "Spindizzy" machines in James Blish's Cities in Flight.
Sometimes, people use "anti-gravity" to describe devices that look like they're reversing gravity, even if they work in different ways. For example, "lifters" fly by pushing air using electromagnetic fields.
Contents
Understanding Gravity: A Quick Look Back
The idea of creating anti-gravity depends on truly understanding gravity and how it works with other physics theories, like general relativity and quantum mechanics. As of 2021, scientists are still trying to figure out a quantum theory of gravity.
Back in 1666, Isaac Newton watched an apple fall from a tree. This simple event helped him realize the principle of universal gravitation, which explains how everything pulls on everything else. Later, in 1915, Albert Einstein came up with a new idea. He thought that gravity isn't a force, but rather what happens when matter bends or warps the space around it. Imagine putting a heavy ball on a stretched rubber sheet; it creates a dip. That dip is like how matter affects space. Einstein also tried to combine his theory of gravity with electromagnetism.
Some quantum physicists believe there might be a tiny particle called a graviton that carries gravity, similar to how photons carry light. Many theories about quantum gravity have been created, like superstring theory and loop quantum gravity.
Could Anti-Gravity Be Real?
In Newton's law of universal gravitation, gravity was seen as an outside force. But in the 20th century, Einstein's general relativity changed this view. It says gravity is not a force, but a result of the shape of spacetime. Under general relativity, true anti-gravity is very hard to imagine, except in very specific situations.
Gravity Shields: Can We Block Gravity?
In 1948, a businessman named Roger Babson started the Gravity Research Foundation. He wanted to find ways to reduce gravity's effects. At first, their ideas were a bit unusual, but they held meetings that attracted famous people like Clarence Birdseye (who invented frozen foods) and Igor Sikorsky (a helicopter pioneer). Over time, the Foundation focused more on just understanding gravity better. It still gives out essay awards today. Some winners, like George F. Smoot and Gerard 't Hooft, even went on to win the Nobel Prize.
General Relativity Research in the 1950s
The US Air Force also reportedly looked into gravity control in the 1950s and 60s. Some newspaper articles claimed that big aviation companies were researching this. However, there isn't much proof outside of these stories.
Companies like the Glenn L. Martin Company and the Institute for Field Physics at the University of North Carolina at Chapel Hill also worked on understanding gravity. Military support for these kinds of projects ended in 1973 with the Mansfield Amendment, which limited defense spending to scientific research with clear military uses. This amendment was passed to stop projects that weren't showing much progress.
Under general relativity, gravity comes from how mass and energy change the normal shape of space. This theory says that the altered shape of space, bent by heavy objects, causes gravity. It's like gravity is a feature of this bent space, not a separate force. While the equations usually don't allow for "negative geometry," it might be possible with "negative mass." The equations themselves don't say negative mass can't exist.
Both general relativity and Newton's ideas suggest that negative mass would create a repulsive gravitational field. This means it would push things away. In 1957, Sir Hermann Bondi suggested that if negative gravitational mass combined with negative inertial mass, it would fit with Einstein's theory and Newton's laws. Bondi showed that negative mass would actually fall towards normal matter, even though the force is repulsive. This is because negative mass would accelerate in the opposite direction of the force. Normal mass, however, would fall away from negative matter.
The Standard Model of particle physics, which describes all known types of matter, doesn't include negative mass. While dark matter is a mystery, its mass is thought to be positive. Dark energy is more complex, as its energy density and negative pressure both affect gravity.
A Unique Force: The Fifth Force?
For a long time, scientists wondered if Einstein's equations applied to antimatter. By 1960, it was understood that antimatter follows the same physics rules as "normal" matter. This means it has positive energy and causes (and reacts to) gravity just like normal matter.
For much of the late 20th century, physicists tried to create a unified field theory. This would be a single theory explaining the four basic forces: gravity, electromagnetism, and the strong and weak nuclear forces. Scientists have made progress in combining the three quantum forces, but gravity has always been the hardest to fit in.
These attempts often tried to explain gravity with a particle called a graviton, similar to how photons carry electromagnetism. Simple attempts failed, leading to more complex ideas. Two of these, supersymmetry and supergravity, suggested a very weak "fifth force" carried by a graviphoton. As a side effect, these theories almost required that antimatter would be affected by this fifth force in a way similar to anti-gravity, meaning it would be pushed away from normal mass. Several experiments in the 1990s tried to measure this effect, but none found clear results.
In 2013, CERN looked for an anti-gravity effect while studying antihydrogen. This was just a side experiment, and the results were not clear.
NASA's Breakthrough Propulsion Physics Program
From 1996 to 2002, NASA funded the Breakthrough Propulsion Physics Program (BPP). This program explored unusual ideas for space travel that weren't getting funding elsewhere. Concepts similar to anti-gravity were studied under the name "diametric drive." This work continues today with the independent Tau Zero Foundation.
Claims and Efforts to Build Anti-Gravity Devices
Many people have tried to build anti-gravity devices, and a few reports of anti-gravity-like effects have appeared in scientific papers. However, none of these examples have been proven to work reliably under controlled conditions.
Gyroscopic Devices
Gyroscopes can create a force that seems to lift them against gravity when they are twisted. While this force is actually an illusion, it has led to many claims of anti-gravity devices. None of these devices have ever been shown to work in controlled tests. They often become part of conspiracy theories as a result.
Another example involves patents granted to Henry Wallace between 1968 and 1974. His devices used rapidly spinning disks made of brass. He claimed that spinning these disks created a "gravitomagnetic" field, similar to a magnetic field. No independent tests or public demonstrations of these devices are known.
Thomas Townsend Brown's "Gravitator"
In 1921, while still in high school, Thomas Townsend Brown noticed that a high-voltage tube seemed to change weight depending on how it was placed on a scale. Throughout the 1920s, Brown developed devices he called "gravitators," which combined high voltages with special materials. Brown claimed his experiments showed anti-gravity effects. He continued his work, trying to sell his ideas to aircraft companies and the military. He named the effects he saw the Biefeld–Brown effect and electrogravitics. Brown even tested his devices in a vacuum, trying to show they weren't just moving air with electric charges.
Electrogravitics is a popular topic among people who believe in ufology (the study of UFOs) and free energy. Some claim the technology was made secret in the 1960s and is used to power UFOs and the B-2 bomber. However, follow-up studies by scientists like R. L. Talley, Jonathan Campbell, and Martin Tajmar have found that these devices produce thrust by moving air, not by creating anti-gravity. They found no thrust in a vacuum.
Gravitoelectric Coupling
In 1992, Russian researcher Eugene Podkletnov claimed that a fast-spinning superconductor could reduce the effect of gravity. Many studies have tried to repeat Podkletnov's experiment, but they have always failed to get the same results.
Ning Li and Douglas Torr suggested that a changing magnetic field could make the atoms in a superconductor create detectable gravitomagnetic and gravitoelectric fields. In 1999, Li's team claimed to have built a working device to create "AC Gravity," but no further proof of this device has been shown.
Douglas Torr and Timir Datta were also involved in developing a "gravity generator" at the University of South Carolina. A leaked document claimed the device could create a "force beam." However, no more information about this project or device was ever made public.
The Göde Award
The Institute for Gravity Research of the Göde Scientific Foundation has tried to repeat many experiments that claim to show "anti-gravity" effects. So far, all their attempts to reproduce these effects have failed. The foundation has offered a reward of one million euros for a reproducible anti-gravity experiment.
Anti-Gravity in Fiction
The idea of anti-gravity is a common and exciting theme in fantasy and science fiction.
Apergy
Apergy is a made-up form of anti-gravitational energy. It first appeared in Percy Greg's 1880 novel Across the Zodiac.
It was also used by John Jacob Astor IV in his 1894 science fiction novel, A Journey in Other Worlds.
Apergy is also mentioned in an 1896 article by Clara Jessup Bloomfield-Moore. In it, apergy describes a hidden force that John Ernst Worrell Keely supposedly controlled using sound frequencies.
In an 1897 article in The San Francisco Call, a science writer claimed to have visited a man who invented a flying boat using an "apergent"—a rare metal called "radlum"—to create controlled apergic force. The inventor described apergy as "a force obtained by blending positive and negative electricity with ultheic, the third element or state of electric energy."
In S. P. Meek's short story "Cold Light" (1930), apergy is described as the opposite force of gravity.
In Chris Roberson's short story "Annus Mirabilis" (2006), Doctor Omega and Albert Einstein investigate apergy. Apergy is also mentioned in the Warren Ellis comic Aetheric Mechanics, where it's created by Cavorite technology.
Other Terms for Anti-Gravity
H. G. Wells's 1901 novel The First Men in the Moon features space travel using "Cavorite," a substance that blocks gravity.
Philip Francis Nowlan's 1928 story Armageddon 2419 A.D. describes "inertron," a substance that falls upwards! This story was the basis for the famous Buck Rogers comic strip.
Images for kids
-
A "kinemassic field" generator from a patent by H. W. Wallace.
See also
In Spanish: Antigravedad para niños
