As children, many of us grow up wanting to be an astronaut. We've dreamed of traveling in space, floating in zero gravity, gazing down on the Earth. Sounds relaxing doesn't it? It's actually quite the contrary.

Space travel is incredibly stressful. While traveling for months at a time, you're cooped up inside a space capsule or station with other astronauts, constantly checking equipment to make sure everything works. All it takes is one false move and you're toast. Which is why scientists are developing a stress test for astronauts on long missions.

It's pretty simple--the test consists of a few questions about how the astronaut feels, how much sleep he or she got the night before, and so on. Then a light flashes on the screen and you push a button in response. The computer records your reaction time and compares it to the times of alert astronauts.

It's just giving you feedback to help evaluate your fitness to complete tasks that require lots of effort and concentration. If your test score indicates that you're overly tired or stressed, then you might decide to postpone the task and get more rest first.