Where does the science end and the fiction begin?

[J Riff]

Aliens arrived, and explained it. No, really. I think the math is right innit..? You whiz off for a few weeks and when you get back it's a year later. Bob's yer uncle, nothing to it. No reason to not go light speed, is there? I mean... it works if you gun it long enough to get to lightspeed, dunnit? I'm pretty sure it does. Which is'nt timetravel in a true sense, but near as dammit. Marcus Welby, I say.