Biefeld–Brown effect

The Biefeld–Brown effect is an electrical phenomenon, first noticed by inventor Thomas Townsend Brown in the 1920s, where high voltage applied to the electrodes of an asymmetric capacitor causes a net propulsive force toward the smaller electrode. Brown believed this effect was an anti-gravity force, and referred to as "electrogravitics" based on it being an electricity/gravity phenomenon. Later researchers suspect that the poor vacuum of Brown's apparatus created an ionic wind or ion drift that produced thrust by transferring its momentum to surrounding neutral particles.