The evacuation raises a question worth exploring: how do astronauts stay healthy in space, and why is this early evacuation so unusual?
There are many reasons why Earth is habitable. One of them is that it's in a delicately balanced radiation struggle with the Sun and the larger cosmos. The Sun emits a powerful solar wind that would strip away the planet's atmosphere, except it's deflected by Earth's protective shield, the magnetosphere. Cosmic rays, dangerous high-energy particles that can damage living tissue, stream in from elsewhere in the cosmos, and they're likewise deflected by the magnetosphere.

