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.

>>2
That last sentence is a common misconception; special relativity can handle accelerated reference frames perfectly fine.  The algebra can get messy, but it's still possible.  With regards to the paradox, the twins make identical predictions, as consistency would require.

Food for thought: a constantly accelerating object, if given a large enough head start, can outrun a photon, though it never actually reaches the speed of light (~ Achilles vs turtle on steroids).

>>2
From the frame of reference of the spaceship, wouldn't the spaceship be standing still, and the earth slow down and turn around? Not the other way around, or is there a way to distinguish this? If so, please enlighten me.

>>4
Guy in spaceship drops a ball.  The ball is now an inertial reference frame, and from the guy's perspective, will accelerate in the direction opposite to which he (and the spaceship) is accelerating.