Gravitation
Gravitation is the scientific statement that all objects having masses try to move toward each other. In everyday life, gravitation is commonly thought of as the weight of an object.
Gravitation keeps the Earth and the other planets in their orbits around the Sun. It keeps the Moon in its orbit around the Earth. It causes tides, convection and many other things that happen. Gravitation is also the reason that the Earth, the Sun, and most other objects in space exist. Without it, matter would not have come together into these big masses. Without gravitation, life as we know it would not exist.
Physics describes gravitation using the theory of general relativity. Newton's law of universal gravitation is very similar to the theory of relativity but much more simple.
The term "gravity" is often used to mean "gravitation". In science, the terms "gravitation" and "gravity" are used differently. "Gravitation" is the theory about the attraction. "Gravity" is the force that pulls objects towards each other.
History of gravitational theory [change]
In the late 17th century, Galileo did a famous experiment about gravity where he dropped balls from the Tower of Pisa. He later rolled balls down inclines. With these experiments, Galileo showed that gravitation accelerates all objects at the same rate regardless of weight.
In 1687, English mathematician Sir Isaac Newton wrote the book Principia. In this book, he wrote about the inverse-square law of gravitation. Newton said that the closer two objects are to each other, the more gravity will affect them. His theory about gravitation was used to predict the existence of the planet Neptune based on changes in the orbit of Uranus.
Newton's theory was later used to predict the existence of another planet closer to the Sun than Mercury. When this was done, it was learned that his theory was not entirely correct. These mistakes in his theory were corrected by Albert Einstein's theory of General Relativity. Newton's theory is still commonly used for many things because it is much more simple to work with than the theory of General Relativity and is usually accurate enough for many uses.
Other pages [change]
- Escape velocity, the minimum velocity needed to fly away from a massive space object
- General relativity
- Gravity
- Newton's laws of motion
- Weight
Other websites [change]
- Gravity Probe B Experiment The Official Einstein website from Stanford University
- Gravity for kids (flash)
- How stuff works: How does gravity work?
