What is the main idea of this passage?
Many scientists, including Albert Einstein, have come up with theories about gravity, and scientists are still trying to figure out how gravity works in atoms and other structures.
Gravity is a force that makes pieces of matter form into planets, moons, and stars.
Albert Einstein was a scientific genius, and his theories about gravity from the 20th century are still very important today.
The NASA Fundamental Physics program is a unique opportunity for scientists to study the effects of gravity in space.