#1 How do I manage my space/time emergence point vs. my starting point... What about the vector my kinetic presence is upon ... If I manage to emerge upon the correct side of the planet, not inside a wall... am I moving in the appropriate direction, considering revolutionary, planetary, solar, galactic, etc.vectors..? OK a computer can figure that out... even if it is possible to pass the kinetic vector forward? (OK that kills a lot of old SF films...)
#2 isn't the universe expanding? If I take matter from now & shove it into the past/future, will it react at all with atoms from the other age? If that matter is me & my heart is beating, will the size of the oxygen atoms of that time be recognized by my red corpuscles... Wow 2-5 minutes viewing the future/past before my conscious brain melts... That's an E-ticket for sure. I think figuring out a way to extend/strengthen telomeres might be a safer way of traveling into the future.
Yes, keeping these thoughts in mind can really mess with the enjoyment of some SF movies. Ohm how I suffer