For one, the spin of the earth. The earth spins at about 1000 miles an hour at the equator. Let's say I jumped from either pole to the equator.
I'd go from barely moving at all to going 1000 miles an hour! You know what would happen? I not only would be killed, I'd be nothing but a very long red streak.
Now if I was to jump from the equator to either pole, I'd appear at the pole and instantly be going 1000 miles an hour. I'd just shoot off into the air, and of course the inertia would squash my innards flat.
I could jump from either pole into space, and have no problem as long as my spacesuit went with me. But again, from the equator into space, and I'd materialize doing 1000 mph. The inertia would pancake me.
As best as I remember, the moon is doing about 60 miles a second, so I could jump from the earth to the trailing edge, and have no problem, except for the fact the moon would be zooming away from me. But if I appeared on the leading edge, I'd hit at 60 miles a second.
Now that I think about it, I was conned by “Star Trek.” That damn transporter would not work at all, unless the Enterprise was in a geosynchronous orbit. Otherwise, splat.
For that matter, whoever is operating the transporter would have to get it right down to the millimeter. Can you imagine appearing with your feet stuck inside the ground?
As for time travel, the same problems apply. The Earth moves around the Sun, the Sun moves around the galaxy and the galaxy moves, too. So if you time-traveled one hour into the future, you’d materialize in space.
If you jumped one million years into the future, who knows where you would end up? In the interior of a star?
Apparently the logistics of overcoming the problems of space and time are insurmountable. It’s fun to pretend they don’t, the way Alfred Bester did in The Stars my Destination or the way Mr. Wizard did with Tutor Turtle. But reality is a different story. Damn.