E=mc^2
Energy and mass are just different measures of the same thing. The transporters job is to take mass and turn it into something that it can more easily move around (a wave? Particle stream?) and back. So as long as the transporter is connected to the ship's energy supply it should theoretically be able to use that energy (instead of the energy from your body) to reassemble any pattern it wants without breaking the law of conservation of mass.
Riker is 6'4 let's say 200lbs, which is 8,153,369 terajoules.
DATA: Imagination is not necessary. The scale is readily quantifiable. We are presently generating twelve point seven five billion gigawatts per (an alarm goes off)
One watt is one Joule per second, there is some debate out there about the "per" part of the quote since watts already implies per second, but we probably assume the ship is capable of generating 12,750,000 terawatts, or 12,750,000 terajoules per second.
8,153,369/12,750,000 gets us about 0.64 seconds of the ships output to create our duplicate Riker.
However the quote above was when the ship was basically idling, (not actually at warp) so the actual output of the ship is likely exponentially larger.
Basically they have so much power available, that they can just rearrange it into whatever mass they want.












