Among the fundamental forces of nature, gravity is the most intuitively familiar. It silently plants us in our seats, or sends us hurtling when we stumble. It holds together the planets and marshals the stars. But what is gravity, exactly? And does antigravity-- a longstanding trope of science fiction --exist? We can seek answers within the nuances of known physics.
In the 17th-century, English polymath Isaac Newton theorized gravity as an attractive force rooted in mass. His theory works perfectly under everyday circumstances; however, it falters at the cosmic scale. In the 20th-century, German physicist Albert Einstein revised Newtonian gravity through General Relativity, describing it as the curvature of four-dimensional spacetime by mass. Though difficult to visualize, decades of rigorous experimentation have attested to the reality of spacetime curvature.
But General Relativity does not mesh well with quantum mechanics, which requires forces to have a carrier particle (like the photon of electromagnetism). Gravity’s speculative carrier particle, the graviton, eludes physicists. An experimentally confirmed quantum description of spacetime curvature is also elusive. Unifying these concepts remains arguably the most highly coveted brass ring of theoretical physics and cosmology.
These limitations complicate the notion of true antigravity. Without a graviton, an equal but opposite antigraviton is untenable. In principle, antigravity could arise from localized negative spacetime curvature; but it would require the existence of negative mass, with causality-violating consequences physicists dismiss. What about antimatter? Though opposite in charge, both antimatter and regular matter exert normal gravitational influence; thus, antimatter cannot produce antigravity.
None of this has impeded the dream of inventing of an antigravity device, albeit the history is storied and checkered. In the 1920s, Thomas T. Brown alleged a capacitor-driven antigravity device that actually relied on ion flow for its effect. Brown’s eclectic contemporary Nikola Tesla proposed a spacecraft drive powered by putative “aether currents”, but never realized a working model.
In the late 1960s, Henry Wallace claimed invention of an antigravitational “kinemassic field generator”, but never submitted it to independent testing and verification. The same holds for the rotating superconductor experiments of Evgeny Podkletnov, Douglas Torr, and Ning Li in the 1990s, inspired by the unverified work of John R. R. Searl in the 1940s. And so, the quest goes on.
The antigravitationally ambitious should know that the Göde Scientific Foundation of Germany offers a €1,000,000 award to the first to truly succeed-- of course, under strongly controlled observational conditions. Whoever pulls it off will join Newton and Einstein in revolutionizing our understanding of the physical universe.