Notes on Gravity

Gravity: A Fundamental Force

Gravity is one of the four fundamental forces of nature.
It is the force by which a planet or other body draws objects toward its center.
On Earth, gravity gives weight to physical objects and causes things to fall.

Isaac Newton: Formulated the law of universal gravitation in the seventeenth century.
- Every mass attracts every other mass.
- The force is proportional to the product of their masses.
- Inversely proportional to the square of the distance between them.
- Expressed mathematically as: F = G \frac{m1 m2}{r^2}, where:
  - F is the gravitational force.
  - G is the gravitational constant.
  - m1 and m2 are the masses of the two objects.
  - r is the distance between the centers of the masses.
Albert Einstein: Expanded on Newton's law with the theory of general relativity.
- Describes gravity not as a force, but as the warping of spacetime caused by mass and energy.
- Explains phenomena that Newtonian gravity couldn't:
  - Bending of light around massive objects.
  - Precise motion of Mercury's orbit.

Celestial Orbits: Gravity keeps celestial bodies in orbit.
- The Moon orbits Earth.
- Planets orbit the Sun.
Galactic Structures: Gravity influences the structure of galaxies.
Cosmic Existence: Without gravity, the universe as we know it wouldn't exist.