1.   And even if they try to recline, the absence of normal gravity means that the body does not interpret the posture as lying down.

2.   Blood and body fluids, which pool in the head in space, are pulled toward the lower torso in normal gravity.

3.   In normal gravity, hot air rises during convection and cools off a wire, helping to block overheating.

4.   It is like being encased in unbaked pumpernickel dough in a world with twice the normal gravity.

5.   The data are measured in Gs, with one G representing normal gravity.

6.   These changes make it harder for astronauts to re-adapt to normal Earth gravity, and can cause lightheadedness or fainting when an astronaut first stands up after landing.

7.   They were then yanked upward toward the ceiling with almost as much force as normal gravity pulls people to the floor.