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Astronaut Scott Kelly came back from 340 days in space two inches taller. Along with height, many aspects of the body change because of the weightlessness environment of space. The body loses muscle, heart and bone mass because it no longer has to support itself as it does on Earth. There is also no feeling of “down” in space. The brain uses this signal for balance, so it has to change how it processes sensory information. While Kelly went to space to study the health impacts, scientists can investigate the effects without leaving the planet. Here are some of the ways scientists recreate weightlessness on Earth. Most of the studies are done for several days to several weeks.

Long-Duration Bed Rest

Study participants lie in bed 24 hours a day. In some studies, the bed tilts towards the head (referred to as head-down tilt, or HDT) to mimic the blood and fluid flow towards the head that happens in space.

Dry Immersion

Study participants sit in a tub of water. This method takes advantage of water’s buoyancy to suspend participants similar to how they would float in space. Participants are wrapped in a waterproof cloth to keep them dry.

Unilateral Limb Suspension

Study participants wear a platform shoe on one foot to keep the other foot off the ground. They balance and get around with crutches. This method focuses on how the muscles change in the hovering leg.

Parabolic Flight

The airplane recreates the weightlessness of space by flying up and down in a wave pattern. Unlike the other methods, the suspended period is very short. Participants float in the air and feel weightless for about 20 seconds when the plane is changing directions to return towards the ground.

Findings from these studies on the health effects of the space environment will help astronauts prepare for long space missions such as going to Mars. For updates on space research, tune in to the National Academies’ Space Science Week March 29 through 31. Experts will share information about ongoing research programs and discuss issues and advances in their fields.

Maggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.