[nyrikki]

The twin paradox holds in a Pacman universe where there is no change in direction.

The main issue with the twin paradox is that it demonstrates where our euclidian intuition fails us.

There are several interpretations on how to resolve it, but they are all just flawed lenses, intended to help you along a curriculum until you understand the math, and also understand the limitations of intuition.

The 'turn around' explanation is part of that and unfortunately often sold as the ultimate resolution.

[floxy]

>The twin paradox holds in a Pacman universe where there is no change in direction.

That is awesome, I've always wondered about special relativity in a flat torus world. Do you have a recommendation for reading more about this?

[Osmium]

Can you expand on this? I was only ever taught the "turn around" explanation.

[nyrikki]

All I can offer without going into the weeds is that it is not the shape of the paths, but mearly the relative length of two paths though spacetime that matters.

Proper time and proper acceleration is possibly a pathway in flat spacetime?

Learning that the order, timing, and sometimes causality of events is also relative tends to be a barrier, thus some of these didactic half truths are useful.

The "Einstein train paradox" is the classic intro to the relativity of simultaneity if you aren't familiar.

In the SR case, proper acceleration is possibly the better option.