It’s well known that when you get a DeLorean up to 88mph there better be a road built on the other side, or you’ll end up in that farmer’s barn…  right?   WRONG!   The Earth is spinning at 1,000mph.  Even if you went back in time for one hour you might end up in the ocean.  Not to mention that the Earth spins around the sun, which spins around the Milky Way, which flies away from the big bang, which (according to Men In Black) sits at the bottom of some alien’s marble bag!  …I hope Marty packed a spacesuit with that hover-board.