Gravity

Gravity is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward (or gravitate toward) one another. On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides. The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing, forming stars – and for the stars to group together into galaxies – so gravity is responsible for many of the large scale structures in the Universe. Gravity has an infinite range, although its effects become increasingly weaker on farther objects.

History

The ancient Greeks noticed that certain objects always fell straight down and that the stars and planets moved in a predictable fashion. This led to the development of the concept of natural motion. Aristotle believed that there was a natural place for each substance and that objects would move to reach their natural place.

Modern understanding

The modern understanding of gravity is based on Albert Einstein's general theory of relativity. According to this theory, gravity is not a force but is a consequence of the curvature of spacetime caused by mass and energy.

Effects of gravity

Gravity has a number of effects on the Earth and the universe. It is responsible for the formation of tides, the shape of the Earth, and the trajectories of comets, asteroids, and interplanetary spacecraft.

See also

• General relativity
• Gravitational wave
• Gravitational constant
• Gravitational field
• Gravitational force
• Gravitational potential
• Gravitational singularity
• Gravitational time dilation
• Gravitational wave
• Gravity of Earth
• Gravity well
• Theory of relativity

References

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