Fotticelli wrote:

It was the Grandfather Normality then. A grandfather hops into a rocket and zips around at speeds close to light for a year. In the meantime 60 years had passed on Earth and his and his grandson is older than he is. He kills his grandson and gets caught while trying to build a time machine that travels back in time. (John did say that the assassin travels back in time to escape the law)

But no paradox.

Lovely Day Media wrote:

That's something I didn't think of in this way before. It was/is possible to go to other planets or even other galaxies ... we just have to figure out how to fly fast enough because there wouldn't be enough time to get there at currently possible speeds.  When/if that happens, it'll then be "easy" and some will wonder why it took so long to figure out.

It's possible now. Just because we can't travel at FTL doesn't mean we can't do it. We just have to be willing to build mufti-generation ships to make the journey.