Prime Taradox

In the Twin Paradox, it's the twin that travels away from and back to earth that supposedly experience a shorter time for the journey, than the twin that remains on earth.

The though struck me; How do we know that it's the spaceship that travels away from and back to earth, and not the earth that travels, causing the spacetwin to appear older upon return?

That bit that always struck you IS the twin paradox, up till that part there is nothing resembling a paradox.

The solution is quite simple, the twin that travels away and back is not in an inertial frame of reference due to having to slow down and turn around. This means only the twin on Earth can make correct predictions based on special relativity.