What is weightlessness?

Weightlessness, or microgravity, occurs when an object is in free fall, explains the U.S. National Aeronautic and Space Association. Gravity pulls the object in free fall at a faster rate due to the equivalence of the force of gravity to acceleration.

Within free fall, the mass of an object remains the same, but the weight of the object is 0. Objects on Earth fall toward the surface, and objects in an orbit fall around that gravitational source. Even astronauts in outer space are in a state of free fall around the Earth’s orbit. Some people in microgravity experience feelings of confusion, headaches, nausea, anemia and muscle cramps.