I've had this idea kicking around in my head for a couple years.
Ok, time travel is invented. It's actually easy to do, but what all those guys forget is that the universe is in motion With combined velocities of the world, planets, stars, and galaxies, a 5-minute trip takes you to when, but you're way out in space somewhere.
Someone creates a 'belt and suspenders' (overly protective) time machine, and figures this out. He only goes into low-Earth orbit, but radios back, and suddenly people realize that you can do interstellar travel; you just have to figure out the combined velocities and vectors, and you can travel back (there), and forward (to where you started).
If you want to try it, be my guest.