As a twenty-something young man, Bob Lazar worked at a secret military installation in Nevada. He was given a half dome the size of a basketball that generated a powerful repulsive force — anti-gravity. His job was to figure out how it worked so we humans could build one.
According to the laws of physics as we know them currently, gravity only pulls, never pushes. Gravity passes through all known forms of matter as if it wasn’t there. You can add more mass that makes the gravity stronger. Perhaps you could make negative gravity if you had a negative mass, but human science doesn’t know how to produce a negative mass.
Lazar tells of his life turning to a living hell after he went public with (what little he knew of) the laboratory’s secrets.