NASA and other space agencies are conducting studies offering $19,000 to each participant who stays in bed for 60 days, Smithsonian Magazine reports. Scientists hope to study the effects that zero-gravity environments have on bone and muscle mass, among other effects. What do we already know about the effects of space flight upon the human body?
Earning $19,000 to stay in bed for two months may sound like a dream job, but NASA, the European Space Agency, and the German Aerospace Center are offering that role to 24 people in efforts to better understand the effects of weightlessness on the human body. Bone and muscle density, bodily fluids, psychological states, and more will be studied as subjects spend 24 hours a day lying prone in bed. This study adds to a wealth of information we currently have about space travel and gravity—or lack thereof.
How Many Objects in Geosynchronous Orbit?
It may surprise you to learn that concepts of prime real estate already exist in outer space, but they do. Satellites that orbit Earth do so at varying speeds and intervals based on their distance from the planet. “The Moon, which is about one quarter of a million miles away, orbits once a month, roughly,” said Dr. Richard Wolfson, the Benjamin F. Wissler Professor of Physics at Middlebury College. “Satellites in near-Earth orbit are roughly 90 minutes.” Somewhere between these distances, since orbital periods increase with distance from Earth, is a point at which the standard orbital period is 24 hours.
“One of the most important, expensive pieces of real estate in space is called ‘geosynchronous orbit,'” Dr. Wolfson said. “If you put a satellite above the equator at that place, which turns out to be about 22,000 miles above the equator, the satellite will go around once in 24 hours, and since the Earth is rotating once in 24 hours, the satellite will appear to stay fixed over a point on Earth.” The commercial possibilities for a fixed satellite constantly covering a specific territory of Earth are considerable, hence the figuratively lucrative real estate.
Geosynchronous orbit is similar to another point in space called the L1 Lagrangian Point. At the L1 Lagrangian Point, the gravitational pull of Earth and the Sun cancel each other out, offering an infinite orbital period. “If you put a satellite there, it and the Earth would happily go around each other, or happily around the Sun, keeping always in step,” Dr. Wolfson said. “That’s where we put some of our satellites—particularly satellites that are used to observe the Sun—because they’re never eclipsed by having to go around the Earth.”
The Zero-Gravity Fallacy
When we say that astronauts in space are “weightless” because there is “no gravity” in space, we’re actually wrong. If there were no gravity in space, then space shuttles and the astronauts within would continue to travel along a straight line forever. In reality, they’re constantly falling downwards towards Earth or another celestial body while maintaining a trajectory along it. This is why we see the circular-shaped orbital flight pattern. Objects orbiting the Earth have found a balance of trajectory and gravity that keeps them at a nearly constant distance from Earth.
“If you really understand gravity then, and you understand it from a Newtonian perspective, you will not make the mistake of thinking there’s no gravity in space and that that’s why astronauts are weightless,” Dr. Wolfson said. “Because if there were no gravity in space, again, Newton’s first law says that straight-line motion—constant speed—would mean ‘bye-bye astronauts, bye-bye spacecraft.’ [A] satellite is falling toward Earth; it doesn’t have to fall to Earth.”
Muscular atrophy and changes in bone mass as well as the position of bodily fluids in astronauts’ bodies are just some of the myriad components in understanding how humans are affected by the radically different states of gravity and perceived weightlessness in space. NASA’s weightlessness study could lead to countermeasures against the tolls taken on the human body by such radical conditions. Being conscientious of factors such as geosynchronous orbit and the misnamed “zero-gravity” state will surely aid their research.
Dr. Richard Wolfson contributed to this article.
Dr. Wolfson is the Benjamin F. Wissler Professor of Physics at Middlebury College. He graduated from Swarthmore College with a double major in Physics and Philosophy. He holds a master’s degree in Environmental Studies from the University of Michigan and a Ph.D. in Physics from Dartmouth.