Comment by titanomachy

The time dilation aspect of it is cool, but doesn’t discuss how far we are from a propulsion system that could credibly pull this off. Even if we solved fusion it wouldn’t get us remotely close. Maybe if you could somehow produce 50 tonnes of antimatter you could do it. But we have no idea how to produce antimatter efficiently or at scale, and even if we could do it with 100% efficiency, it would take many years of humanity’s current energy budget just to make the antimatter fuel for a single manned trip.

To me it seems like we’d need new physics (not just new technology) to have any chance of pulling this stuff off.

The book dodges these inconvenient numbers with a bit of a deus ex machina plot device that I won’t spoil here :)