High Quality Content by WIKIPEDIA articles! A tachyonic field, or simply tachyon, is a quantum field with an imaginary mass that represents an instability. The term "tachyon" was coined by Gerald Feinberg in a 1967 paper that studied quantum fields with imaginary mass. Feinberg believed such fields permitted faster than light propagation, but it was soon realized that Feinberg`s model in fact did not allow for superluminal speeds, and instead that an imaginary mass causes an instability to a process known as tachyon condensation.