In several Trek episodes, transporter accidents did make copies of people. In an episode of Voyager, two people were combined by a transporter accident.
While I may provisionally accept the idea that transporters may seem to break the laws of thermodynamics, what of wormholes?
A wormhole could make an object disappear here and reappear over there, and the end result would be just like the teleportation of the transporter.
I am a professional science fiction author, so I had to chime in . . . although this discussion has made me wonder if backward time travel may be impossible because of the law of conservation of mass-energy.
If I traveled back in time, I believe that the Universe (back then) would increase its mass by the amount of mass that makes up my body, so maybe the First Law of Thermodynamics is what keeps this from being possible?
Conversely, backward time travel would subtract my mass from the Universe now, so we have the same issue?