Hi, my first post on the forums. I've known about twin paradox for a while, so when we learned special relativity at school in September, it wasn't anything weird. Math is elegant, unlike quantum physics. But a few weeks ago, I started wondering something. It might be just an ordinary logical mistake, so go easy on me. Twin A is the one in the spaceship, and twin B stays with his wife and kids on Earth. We will take Earth as the reference point. In this system Twin A travels at relativistic speed v. Due to time dilatation he is aging slower, and after eg. 10 Earth years he will age eg. 6 years. Now here is a thing I can't wrap my mind around: To twin B, spaceship will be a reference point, and Earth will be moving away at -v. This means that time on Earth will be slower than his. So, when he returns from his voyage, people on Earth should be younger than him. I've tried formulating this in proper time equation, in order to find an error, but square doesn't make a difference between -v and v. Will I get a different result if I use coordinates?