Zero gravity

Science World, Feb 7, 2005 by Jeanna Bryner

Last September, 16-year-old Seth Coleman sat cross-legged on the floor of a Boeing 727 as it climbed skyward. This wasn't a typical flight to visit relatives. Seth was aboard a Zero Gravity Corporation plane that lets space enthusiasts experience the weightlessness once reserved for astronauts.

And Seth didn't have to zoom to outer space for the floating feeling. Instead, the aircraft ascended to 7,300 meters (24,000 feet) above the Gulf of Mexico. The lofty altitude allowed the airplane to follow roller-coaster-like arcs without smashing into anything.

Then the plane lifted its nose and abruptly accelerated (changed velocity over time) up the first arc. As the craft neared the slope's top, it slowed down. That's when Seth's legs began rising to his chest. With the ease of an Olympic gymnast, he flipped in midair.

What gave Seth his "flying" powers? Dominic Delrosso, a NASA engineer explains: On Earth, you stay put because the downward pull of gravity (force that pulls two objects together) is balanced by the ground's upward push. But the plane's maneuvers sent Seth into free fall (the state when gravity isn't balanced by an equal and opposite force).

To create the unbalance, the plane dived toward Earth at the same rate as gravity was tugging on the passengers. That gave Seth a short 25-second float time. As the plane reached the arc's valley, Seth plopped back down and waited for the plane to motor upward again for another round.

Seth, an avid skate- and snowboarder, says, "If you've ever dreamed of floating, that's exactly what [the zero-gravity flight] is like."

Did You Know?

* While in space, astronauts can grow up to 5 cm (2 in.) taller. That's because the cartilage disks in the spine expand due to zero gravity.

* The Zero Gravity Corporation's flight also simulates Martian gravity, which is one third of the gravity felt on Earth. Zero Gravity's Alan M. Ladwig says that under this gravity, kids can make giant leaps like Michael Jordan.

* Scientists recommend that you eat lightly before a zero gravity flight. Since your body isn't used to the floating feeling, it's easy to get space-motion sickness.

Resources

* To learn more about zero-gravity flights, Visit: www.nogravity.com/

* This Web site is filled with answers to questions about gravity: http://amazing-space.stsci.edu/capture/gravity/