Getting Answers to My Problem With Einstein’s Theory of Relativity

You probably don’t know it but I’ve got a background in engineering. Actually a high tech, very specialised niche area of materials engineering. I also like to keep my scientific mind well nourished and devour science blogs and the like.

An area of interest is theoretical physics and some aspects of Einstein’s theory of relativity haven’t been sitting well with me for a few years. So I’ve upped the ante and have started seeking out answers. First question has gone straight to the top. Prof Sir Roger Penrose is a world leader in relativity and cosmology. I have asked Sir Roger the following:

“Considering space travel at high speeds, particularly velocities close to the speed of light, I understand that relative to those persons on the home planet, time for people on the space ship slows and they age less which may allow them to explore the universe in future.

My dilemma concerns any return journey. Surely for a return journey the opposite occurs. Time speeds up, they age faster.

Is time analogous to work? I can take a brick off the floor, lift it above my head (giving it potential energy), but if I then put it back on the floor it has no potential energy and relatively no work has been done. Similarly, I can put someone in a rocket, fire them into space at almost the speed of light (giving them a time potential), but if they return to Earth, that time potential returns to zero and no work has been done?”

Part of me wants this to be a ground breaking question. Another part of me wants it to be insignificantly trivial. Right now, I just hope Sir Roger replies.