freakin aperture science.. they make this amazing tech and then use it to what..? make a hapless person perform stupid tests with it and that's all. also everyone knows that you can only teleport a short distance. if you want to go to the north pole, you have to rapid-fire teleport; which would solve the problem of momentum. and going into space wouldn't be a problem either, since you are technically warping in and out of a higher dimension instantly when you teleport, rather than moving through reality really fast. the REAL problem is not teleporting into the earth or some other object when you're coming back.,(reply>), No one 'knows' anything about teleportation. It isn't real. Also, some fictions have teleportation occur by mass exchanges or magic, and have nothing to do with crossing between dimensions.