Umm,, vox, that makes you go back in time. (I think..? O.o)
I'll try to explain what I think..
BWOOM! You fly away from the earth in the speed of light, and you're no longer an event in the dimension of spacetime.
But the time on earth goes on..
When you then turn back, still travelling in the speed of light, and you eventually reach the earth, you're back in the exact same second as you left.
Wich, kinda makes you travel back, but, infact doesn't make you travell anyway at all.
But are you sure about that if you travell in the speed of light, time will stop?
I didn't know that.
Edit:
The theory holds that, relative to a stationary observer, time appears to pass more slowly for faster-moving bodies: for example, a moving clock will appear to run slow; as a clock approaches the speed of light its hands will appear to nearly stop moving
Wikipedia.
it doesn't stop, it's just, much slower.
Close enough.
And I was wrong:
These effects are to some degree similar to hibernation or hypothetical suspended animation (which slow down the rates of chemical processes in the subject), and only allow "time travel" only toward the future: never backward.
Edit2:
Oh, I get it now!
If time is moving slow for you, but fast for the others, and you return, you will return to the future, not to the same time as you left.
Amazing..