The aging of the two brothers in the “twins paradox” is analyzed through the space-time evolution of the densities that correspond to their internal complex structure. Taking into account their relative motion, it is shown that the traveling brother evolves over a shorter interval of time than his twin, which makes him younger than his brother.

ḥeleḳ 1. Pirḳe ʻiyun be-gidre mitsṿat ha-biṭaḥon be-mishnato shel Baʻal Ḥovot ha-levavot.

Takanat ha-shavim, Magen ṿa-shemesh. Ṿa-yaged Moshesh, hosafot ṿe-heʻarot ʻal sefer Takanat ha-shavim.