Fred Best is the director of the NASA Center for Space Power at Texas A&M University and a professor of nuclear engineering at the university. He has spent years conducting engineering research on NASA's KC-135 microgravity airplane (known to some as the "Vomit Comet"). He offers this firsthand account:

"The feeling is completely different from being on a roller coaster. It is more like motionlessness than movement. I feel great in zero gravity either floating in place or flying through space. As long as you are in rational control of your movements, zero gravity is the realization of a dream. A little push sends you gliding, just like the characters in science fiction stories.

"Beware losing your orientation, however. If your instincts take over, your brain starts telling you, 'You're falling, reach out and catch yourself.' Your arms and legs flail until you regain rational control and convince your brain you are okay.

"Some background that might interest your readers: Students and I are studying flowing fluids in zero gravity. We use the KC-135 aircraft (which was also used for the weightlessness scenes in the movie Apollo 13) as our laboratory. Since 1986, I have made about 120 KC-135 flights, resulting in about 5,000 'zero gravity' periods lasting 20 seconds each. I have also made some flights which simulated lunar and Martian gravity. We last flew in May and expect to fly again in January. We also fly simple experiments for primary and secondary school science classes, which they analyze to understand zero gravity effects.

"Overall, zero gravity is a treat not to be missed."

George M. Pantalos is a research assistant professor in the departments of surgery and bioengineering, and artificial heart clinical coordinator at the University of Utah. He has collaborated on a "Hearts in Space" experiment, during which he too flew on (and operated aboard) NASA's KC-135 aircraft; the artificial heart will fly on the space shuttle next year.

"Weightlessness is not like endlessly falling, although in reality, that is what it is. Nor is it like a roller coaster, although being in an airplane flying the path of a roller coaster is one way to create weightlessness for about 20 seconds at a time.

"In weightlessness, you are effortlessly floating, because all of the acceleration forces on you add to zero. The most comparable feeling is floating in water without the sensation of water on your skin. Because you feel so light, you can move about with the slightest amount of effort. Pushing off a surface too hard, which is the common mistake of all first-time free-floaters, results in you zinging around like a Ping-Pong ball. Nice and easy does the trick. And there is no up or down in weightlessness, so you need to figure out which orientation visually works best for you.

"Peter Pan never had it so good and Michael Jordan only gets a few seconds of hang time. In weightlessness, you have all the hang time you need.