In the twin paradox situation, a fellow student objects to the argument that Anna's acceleration is the root of the asymmetry. "All motion is relative! Anna is accelerating relativetoBob, but Bob is accelerating relative to Anna" Answer this objection.

Relative acceleration (also or) is the acceleration of an object or observer B in the rest frame of another object or observer A.

While the males who stayed behind did appear to have accelerated to the ladies who went out and returned to Earth, this was only a false impression because acceleration requires the application of force.

The man can claim that he wasn't accelerating because there was no net force exerted on him while the woman was away. The women must exert four different forces: an acceleration force to move away from Earth, a deceleration force near the end, an acceleration force to move back toward Earth, and a third force to move backwards towards Earth. In contrast to acceleration, motion is therefore not relative.