Microgravity (noun, “MY-crow-GRA-vih-tee”)
Microgravity is the experience of gravity that is only a fraction of the force we experience on Earth. Gravity is a force that attracts anything with mass to anything else that also has mass. The more mass, the greater the gravity. You stay on the surface of the Earth because the Earth’s mass is attracting your own mass to it and holding you here.
“Micro” means something small. So microgravity is what happens when the experience of gravity seems very small. Though we may say that astronauts are weightless in space, what they’re actually experiencing is microgravity.
Microgravity isn’t the absence of gravity. There is gravity, even in space. It just becomes weaker with distance from the object exerting the gravitational force. So when people go into space, they experience weaker gravity. So do the objects around them.
Astronauts study microgravity while in space to find out what it does to organisms over time. For example, our bones and muscles develop the strength to keep our bodies upright against the force of Earth’s gravity. It’s like strength training you’re not even aware of. After too long in microgravity, our muscles and bones become weak. They no longer need to keep the same level of strength. Plants also grow differently in microgravity. That’s important for scientists learning how to grow crops in space for long-term space travel.
In a sentence
Scientists studied Scott Kelly as he spent a year in space, comparing his life in microgravity to that of his Earth-bound twin, Mark Kelly.