Anti-gravity is the idea of a force that would exactly oppose the force of gravity. According to current physics laws, anti-gravity is not possible. Tests have shown that antihydrogen does not repel Earth's mass.
Anti-gravity is not the same as feeling weightless during free fall or orbit, nor is it the same as balancing gravity's force with other forces, such as electromagnetism, aerodynamic lift, or ion-propelled "lifiers," which move air using electromagnetic fields to fly.
After scientists discovered antimatter, some thought anti-gravity might be possible. However, once scientists better understood antimatter, they found that gravity affects both matter and antimatter in the same way. Anti-gravity is a common idea in science fiction.
Theoretical probability
According to the laws of general relativity, anti-gravity is not possible except in special situations. Under this theory and particle physics, gravity is a result of mass and energy, a value that is always positive. Gravity is always attractive and never repulsive.
In the late 20th century, NASA funded the Breakthrough Propulsion Physics Program (BPP) from 1996 to 2002. This program looked into many unusual ideas for space propulsion that were not getting support from regular university or business sources. Anti-gravity-like concepts were listed as ideas that were not considered useful because the study found no proof of anti-gravity-like forces. Because so many unsuitable proposals were submitted, NASA created a guide to help reviewers evaluate ideas more effectively.
History
Attempts to understand why gravity only pulls things together, and never pushes them apart, began at least as early as the late 1800s with James Clerk Maxwell. He observed that electromagnetism has both positive and negative charges, which makes it different from gravity. In the 1900s, with the development of general relativity and particle physics, this difference became even more clear. In gravity, the "charge" is mass-energy, a value that is always positive. This made gravity seem always attractive and never repulsive. However, two possible exceptions were found later: in quantum physics and at very large scales in the universe.
In 1928, Paul Dirac created a theory that combined Einstein’s relativity with quantum mechanics. This theory correctly predicted the properties of electrons but also had a second solution. In 1931, Robert Oppenheimer showed that Dirac’s original explanation of this second solution was wrong. Dirac then proposed that the second solution was a positively charged "anti-electron." He also suggested that every particle has an opposite-charged version. These ideas were later supported by discoveries of the positron in 1932 and the antiproton in 1955, proving the existence of antimatter.
Dirac’s theory did not include gravity, and no complete theory has yet combined quantum mechanics with general relativity. A hypothetical negative mass in Newton’s or Einstein’s equations is mathematically possible, but no evidence supports this idea. Since antimatter is rare, some scientists wondered if matter and antimatter might repel each other, creating a form of antigravity.
By 1956, scientists began studying whether antigravity could exist. Three major arguments against it were published in the following years. In 1958, Philip Morrison showed that repulsion by mass would break the rule that energy is always conserved in Earth’s gravity. In 1959, Leonard I. Schiff argued that in quantum field theory, antimatter’s effect on gravity would contradict results from the Eötvös experiment, which tested whether all objects fall the same way in gravity. In 1961, Myron L. Good noted that a long-lived K meson, which is a mix of a particle and its antiparticle, would decay if they reacted differently to gravity. Despite these arguments, new theories from cosmology and particle physics have suggested that gravity between matter and antimatter might be repulsive.
Testing gravity’s effect on antimatter is very difficult. For regular matter, experiments have shown that inertial and gravitational mass are equal, a rule called the weak equivalence principle, with a precision of 10 to the power of -15. These experiments used electrostatic accelerometers on two test masses made of titanium and platinum in a satellite. Creating antimatter hydrogen requires antiprotons from a particle accelerator and positrons, making such experiments impractical in space. In 2023, scientists at CERN compared how much antihydrogen escaped from the top and bottom of a vacuum chamber. This experiment ruled out the possibility that antihydrogen and Earth’s mass repel each other through gravity.
Studies, empirical claims and commercial efforts
There have been many studies, attempts to create anti-gravity devices, and some reports about anti-gravity-like effects in both popular and scientific writings. However, none of the examples described are considered proven or repeatable examples of anti-gravity.
In 1921, while still in high school, Thomas Townsend Brown noticed that a high-voltage Coolidge tube seemed to change mass depending on how it was placed on a balance scale. Over the next decade, Brown developed devices that combined high voltages with materials that can store electrical energy (similar to large capacitors). He called these devices "gravitators." Brown told others and the media that his experiments showed anti-gravity effects. He continued his work, creating high-voltage devices to sell to aircraft companies and the military. He named the effect seen in his devices the "Biefeld–Brown effect" and the field of study "electrogravitics." Brown tested his asymmetrical capacitor devices in a vacuum, claiming this showed the effect was not caused by ion movement in air.
Electrogravitics is a topic often discussed in books, websites, and theories about UFOs, anti-gravity, and free energy. Some people claim this technology became highly classified in the 1960s and is used to power UFOs and the B-2 bomber. There are also online videos and research that claim to show lifter-style capacitor devices working in a vacuum, meaning they are not powered by ion wind or ion drift in air.
Later studies on Brown’s work and similar claims were done by R. L. Talley in a 1990 US Air Force study, NASA scientist Jonathan Campbell in a 2003 experiment, and Martin Tajmar in a 2004 paper. Talley tested the effect in a vacuum using up to 19,000 volts but found no force greater than 2 × 10 N. Tajmar and his team found no evidence of effects in a vacuum with steady electric fields. These experiments concluded that Brown’s observations were likely due to "ion wind," and no experiments showed thrust in a vacuum.
In 1948, businessman Roger Babson started the Gravity Research Foundation to study ways to reduce gravity’s effects. Early efforts were sometimes seen as unusual, but the Foundation held conferences with scientists like Clarence Birdseye and Igor Sikorsky. Over time, the Foundation shifted focus to better understanding gravity instead of controlling it. After Babson’s death in 1967, the Foundation nearly stopped working but continues to run an essay contest with prizes up to $4,000. As of 2017, it is still managed in Wellesley, Massachusetts, by George Rideout Jr. Past winners include George F. Smoot (1993), who later won a Nobel Prize in Physics, and Gerard 't Hooft (2015), who also won a Nobel Prize.
Gyroscopes can produce a force when twisted that seems to lift them against gravity. Although scientists know this force is not real, it has led to many claims about anti-gravity devices and patents. None of these devices have been proven to work under controlled conditions, and they often become the subject of conspiracy theories.
Another example is a series of patents granted to Henry Wallace between 1968 and 1974. His devices used rapidly spinning brass disks, a material with certain nuclear properties. Wallace claimed that spinning the disks aligned their nuclear spins, creating a "gravitomagnetic" field similar to the magnetic field in the Barnett effect. No independent testing or public demonstrations of these devices are known.
In 1989, it was reported that a spinning gyroscope’s weight decreased along its axis. A test the next year found no evidence of this effect. Scientists recommended further testing at a 1999 AIP conference.
In 1992, Russian researcher Eugene Podkletnov claimed that a fast-spinning superconductor reduced gravity’s effects. Many studies tried to repeat his experiment, but all failed.
Douglas Torr, from the University of Alabama in Huntsville, proposed that a changing magnetic field could create detectable gravitomagnetic and gravitoelectric fields in superconductors. In 1999, a woman named Miss Li claimed in Popular Mechanics that she built a working prototype to generate "AC Gravity." No further proof of this device was provided.
Douglas Torr and Timir Datta were involved in creating a "gravity generator" at the University of South Carolina. A leaked document from the university’s Office of Technology Transfer, confirmed by a reporter in 1998, stated the device could create a "force beam" in any direction and would be patented. No further details about this project or the "Gravity Generator" were ever made public.
Göde Award
The Institute for Gravity Research, part of the Göde Scientific Foundation, has attempted to repeat many experiments that claim to show anti-gravity effects. So far, all of the institute's efforts to observe anti-gravity by copying these experiments have not been successful. The foundation has announced a reward of one million euros for anyone who can create an experiment that reliably demonstrates anti-gravity.
In fiction
Anti-gravity is a popular idea in science fiction stories. The Encyclopedia of Science Fiction notes that Francis Godwin's novel The Man in the Moone, published in 1638 after his death, includes a "semi-magical" stone that can increase or decrease gravity. This story is considered the earliest example of the anti-gravity theme. The first story to use anti-gravity for space travel and to explain the idea using science instead of magic was George Tucker's 1827 novel A Voyage to the Moon.
The term "Apergy" was created by Percy Greg to describe an imaginary anti-gravitational force in his 1880 novel Across the Zodiac. Later, other writers, such as John Jacob Astor IV in his 1894 novel A Journey in Other Worlds, used the term in their stories.