Microgravity
It is like being inside a free-falling elevator whose cable snappedโyour feet gently float off the floor.
Definition Microgravity is an environment where gravity seems to disappear because an object and its surroundings are in continuous free fall together at the same rate, creating near-weightlessness. It is most commonly experienced in low Earth orbit, such as aboard the International Space Station.
Why Do Astronauts Float in the Space Station?
Have you ever felt your stomach drop and your body lift off the seat when a drop-tower ride suddenly plunges at an amusement park? If an elevator cable snapped and both the cabin and you fell downward together, your feet would not press against the floorโyou would simply float in midair.
That is exactly why astronauts float inside the space station. At an altitude of 250 miles (400 km) where the International Space Station orbits, Earth's gravity is still surprisingly strongโabout 90% of what we feel on the surface. Astronauts do not float because gravity has vanished; they float because the station and the crew are falling toward Earth together endlessly.
So why don't they crash into the ground? The station travels forward at such a blistering speed that as it falls, Earth's surface curves away beneath it at the exact same rate. In effect, it is locked in a perpetual fall around the planet without ever hitting the ground.
To Be More Precise: Why 'Micro'?
What people casually call 'zero gravity' is scientifically termed microgravity. The prefix 'micro' means one-millionth, indicating that gravity feels reduced to roughly one-millionth of what we experience on Earth's surface.
In reality, achieving absolute zero gravity on an orbital station is nearly impossible. Tiny vibrations from astronauts moving around or equipment running ripple through the hull, and faint atmospheric drag still tugs on the station.
Because these minute forces continuously add up, an infinitesimal amount of gravity remains rather than absolute zero. That is why the scientific community officially uses the term microgravity instead of zero gravity.
The Magic of Microgravity You Cannot See on Earth
In microgravity, physical laws that we take for granted on Earth behave in unexpected ways. On Earth, hot air rises due to buoyancy, giving a candle flame its teardrop shape. But without buoyancy-driven convection in orbit, a candle burns as a perfectly spherical, blue flame.
Liquids do not stay in a glass either; surface tension pulls water into floating spheres. This unique convection-free, sedimentation-free environment turns the space station into an extraordinary orbital laboratory.
Scientists use it to grow large, flawless protein crystals unwarped by Earth's gravity to develop new medications, and to study muscle and bone loss in astronauts to unlock secrets of human aging.
๐ค Common misconceptions
There is zero gravity on the space station.
At an altitude of 250 miles (400 km), roughly 90% of Earth's gravity is still active. Astronauts feel weightless only because they and the station are in continuous free fall together.
๐งบ Where you meet it
Gravity has not vanishedโyou feel weightless because you and your surroundings are falling together endlessly.