This isn't exactly the same, but...

I read a short story not long ago by George R. R. Martin that was about a guy who makes a machine with which he give his current mind to himself when he was younger (a sort of time travel).

Not only is this the basis for a post I just made on this website...

But the other day while on the bus I zoned out (had no recognition of the world around me) for approximately half an hour because I was so absorbed considering the dynamics of such an invention and how it would effect time and reality.