 A Cal-Tech physicist invited to observe Brown's disk device in the early 50s noted during the demonstration that its motivation force was the well known phenomenon of "electric wind", and not anti-gravity, saying “I’m afraid these gentlemen played hooky from their high school physics classes….” Research in the phenomenon was popular in the mid-1950s, at one point the Glenn L. Martin Company placed advertisements looking for scientists who were "interested in gravity", but rapidly declined in popularity thereafter.Since this effect could not be explained by known physics at the time, the effect has been believed to be caused by ionized particles that produces a type of ion drift or ionic wind that transfers its momentum to surrounding neutral particles, an electrokinetic phenomena or more widely referred to as "electrohydrodynamics" (EHD).Electrogravitics has become popular with UFO, anti-gravity, and government conspiracy theorists where it is seen as an example of something much more exotic than electrokinetics, i.e.