Bone and muscle deterioration, radiation exposure, vision impairment — these are just a few of the challenges space travelers ...

If so, they could be heading back to Earth ... body, possibly contributing to heart disease and other conditions. Bones thin by about 1.5 percent a month. Spinal discs harden. In the head, parts ...

Traveling through the interior of the Earth, body waves arrive before the surface waves emitted by an earthquake. These waves are higher frequency than surface waves. P waves are also known as ...