Feynman thought his diagrams reflected an actual reality. So what are the particles that travel backwards in time? Are they not tachyons? Is that not what Relativity implies? The faster a particles goes, the slower it goes in time. So going faster than light means going backwards in time. And now we see in String Theory that the structure of D-branes of dimension 24 are made of tachyons.
[I would imagine that eventually there will be found a dimension in which entropy also goes backwards because for some reason or other the equations of motion with just backwards time do not reveal anything of interest as Feynman noticed in his 1948 paper. But putting negative entropy along with time going backwards does result in very interesting things.
[I would imagine that eventually there will be found a dimension in which entropy also goes backwards because for some reason or other the equations of motion with just backwards time do not reveal anything of interest as Feynman noticed in his 1948 paper. But putting negative entropy along with time going backwards does result in very interesting things.
