If aliens are able to detect earth and we can't detect them that automatically means they're far more intelligent than us. And true that we'd not be able to withstand traveling at that rate, there is a possibility of technology that can possibly nullify the effects. And, if we weren't to have help from aliens, we wouldn't have enough time to travel to the planets that we do know support life. They're just too far away. The only possibility of us moving planets is if we start doing it in this generation. Otherwise, it'd be too late in my opinion.
But hey, I'd like to hear the other theories. These topics really interest me.
@Ace True. Not necessarily.
But putting things into perspective. when a star explodes, we'd never know until hundreds of years later when light emitted from the explosion finally travels to us. Hypothetically speaking, that means it seems like time travel to us on earth, although it wouldn't for them. It is true that you're not surpassing time, however you do experience the effects of which you were to. If we could preserve a body in ice, to the human it wouldn't feel like any time has passed. But it reality, other people on earth do feel the time passing because they're not unconscious. It's a conceptual idea, in other words.