# In the twin paradox without acceleration, how is the symmetry broken? [closed]

In the twin paradox without acceleration, where $$A$$ is "stationary", and $$B$$ makes a journey and then turns back, we can just as easily suppose $$B$$ is stationary and $$A$$ is the one who makes the journey in the opposite direction and then turns back.

If the situation is really symmetrical, then any argument that can be made saying that $$B$$ will be of a different age when they meet, can obviously be reversed to argue the same for $$A$$.

So please, without explaining why the asymmetry leads to an age difference, why is the situation actually asymmetrical?

• You say "without acceleration" but whichever twin moves has to accelerate to reverse their direction of travel. So what you are describing is the twin paradox with acceleration. Sep 25, 2022 at 10:00
• As John says, the asymmetry is that one twin changes direction (aka accelerating) and the other doesn't. Whichever twin coasts throughout the experiment will age more than the twin who has to turn around. Sep 25, 2022 at 10:55
• Have tried here: @ physics.stackexchange.com/q/123106, and here: @ en.wikipedia.org/wiki/Twin_paradox ? Sep 25, 2022 at 10:59