A bioreactor is a facility used for growing living cells. Using the bioreactor in microgravity should enhance this three-dimensional growth. The first sample to be grown in the bioreactor on Mir will be cartilage tissue. This experiment will help scientists discover ways to grow tissue for replacement of damaged cartilage in humans. The force of Earth's gravity extends far into space.
Weight is the force with which a body is attracted to the Earth.
Any object in a state of freefall experiences microgravity, or near weightlessness. An orbiting spacecraft is actually falling around the Earth. The spacecraft's altitude and speed cause its fall to match the curvature of the Earth, so that it never hits the Earth but continually orbits the planet. All objects carried by an orbiting spacecraft are also in a state of freefall.