In the weightlessness of orbit, an astronaut’s heart can become more spherical as it no longer works against gravity in the usual way, while their spine stretches enough to make them measurably taller before they return to Earth.

In the weightlessness of orbit, an astronaut’s heart can become more spherical as it no longer works against gravity in the usual way, while their spine stretches enough to make them measurably taller before they return to Earth.

Spend long enough in orbit and your own body starts to change shape. With gravity no longer pulling on it in the usual way, an astronaut’s heart can grow slightly more spherical, and their spine can stretch enough that they return to Earth measurably taller than when they left. Both changes are real, both are temporary, and both come down to the same thing: a body built for gravity, briefly relieved of it. Neither is dramatic on its own. Togethe…