Cryogenics That Work
Let's say you have a deadly illness, and a cure is on its way but not close enough.
The science fiction of the past would suggest a world where people freeze their bodies to near absolute zero, only to be restored when a cure is at hand.
There are many biological problems with cryogenic "life extension". For example, water expands when it freezes.
The much better solution to this problem is jumping on a spacecraft and accelerating to near the speed of light. Time will pass more slowly for you relative to planet Earth.
Of course this approach has been the subject of science fiction as well. The thing that recently dawned on me is that you don't necessarily need a plan to slow down and return to Earth.
If you assume that the cost of propulsion drops over time, as it has so far in human history, all you need to do is accelerate to go very fast, and over time it will become cheaper and cheaper for someone from Earth to catch up to you, give you the cure, and slow you down.
There are a few coefficients in this equation, but it seems conceivable if (a) the cure isn't too far away, (b) you'd be of reasonable value to save, and (c) propulsion becomes sufficiently inexpensive.
Pretty cool! This seems far away, but the future is long. I wonder if it will ever be used.