What is Wrong with the Solution?

To solve this puzzle, no real effort is needed. E and T are always of the same age, no matter T is traveling or not.

It makes sense that our lifespan is decided by our environment, not by some high-tech aliens traveling in light speed vehicles. The lifespan of aliens is not affected by us either, whether we are moving or not.

So how did we get the twin paradox? Where did our reasoning process go wrong?

I can only think of two possibilities. One is that Special Relativity does not apply to our everyday life scenarios. Another is that the principle of relativity is wrong.

When Einstein invented this theory, he was motivated to use it on electromagnetic waves. Is it safe to extend it to our everyday life scenarios?

While the laws governing electromagnetic waves and everyday objects may be quite different, time itself is the same. In the twin paradox, the real broken piece is time. If a slower clock does not work in our everyday life, it certainly won't work anywhere else.

As for the principle of relativity, nothing seems wrong. The idea of relative motion was first brought up by Galileo, and then got fully utilized in Newtonian mechanics. Extending the principle of relativity beyond Newtonian mechanics is a big step, but it is not suspicious to me.

As no evident error can be found in our reasoning, our next step is to go to Special Relativity itself, and see if we can find anything wrong.