Gravity is a force that governs motion throughout the universe. It holds us to the ground, and it keeps the moon in orbit around Earth and Earth in orbit around the sun.
Many people mistakenly think that gravity does not exist in space. However, typical orbital altitudes for human spaceflight vary between 120 - 360 miles above Earth's surface. The gravitational field is still quite strong in these regions, since this is only about 1.8 percent the distance to the moon. Earth's gravitational field at about 250 miles above the surface is 88.8 percent of its strength at the surface. Therefore, orbiting spacecraft, like the space shuttle or space station, are kept in orbit around Earth by gravity.
1. Your head swells in microgravity. On Earth, gravity pulls fluids in the body down into the legs. In microgravity, however, blood and other fluids shift to be redistributed throughout the body, including astronauts’ heads, causing them to swell.
2. It doesn’t make people weightless. People aren’t weightless on the ISS. In fact, 90 per cent of Earth’s gravity still affects the ISS, so people weigh 90 per cent of what they would on Earth. The reason they float is because the ISS is in perpetual free-fall around the Earth, an orbit in which microgravity takes effect because people and objects inside fall at the same rate as the ISS itself.
3. There is gravity everywhere in space. The further you move away from an object with mass, the weaker its gravitational influence becomes. But there is gravity everywhere in space, whether it’s the Sun or the core of the Milky Way, it will always have some influence over you.
4. Microgravity makes you taller. In microgravity, the vertebrae in your spine are no longer compressed by Earth gravity, causing the discs between them to expand and the spinal column to lengthen, making you taller.
5. It makes water act strangely. Did you know that water boils into one big bubble in microgravity? On Earth, boiling water in a kettle creates tiny vapour bubbles that rise to the surface, but in the absence of convection and buoyancy – two terrestrial phenomena caused by gravity – they simply cling to the kettle’s element and merge to create a single bubble.
