Gravitics [Gravity Studies]

Theories About Gravity.

Principia - 1687

Isaac Newton

[Newton is said to have discovered the force of gravity

when he saw an apple falling from a tree. However others such

as Galileo and Cavendish might have been conducting their own

experiments with gravity before Newton.]

- gravity as a force that obeys an inverse square law. >

General Theory of Relativity - 1915

Albert Einstein

This theory treats gravity as a consequence of the geometry of space.

A mathematical construct called "space-time" is used in this theory.

This theory tries to suggest that gravity is not a real force.

Newtons 1st law says that objects travel in straight lines or are at a rest.

[Newtons first law is sometimes described as: an object travelling under

its own inertia in a straight line, or an object remaining at rest because

of its inertia against motion. Newtons first law describes a "straight inertial path".]

Einstein's theory suggests that large masses create "curved inertial paths" in space.

So objects travel in curves, or travel in orbits under their own

inertia, when they are near a large mass.

Quantum Theories of Gravity - 1950s - present.

Various Scientists

These theories postulate that gravity might be associated with a

fundamental particle such as a "Graviton" . These theories are very

difficult to test because gravity is a very long range, very weak force,

compared to the other forces of nature. Quantum theories are on a

very small scale and they are trying to describe

a force that acts over very large distances.

[quantum theories of gravity are probably

often connected to "Unified field theories"

andn"String Theories".]

Theories before Newton/Cavendish.

1)Ptolemy - Geocentric solar system. This theory is wrong! But

it can predict planetary motions quite accurately. Epicycles

2)Aristotle - Heavier masses fall faster under gravity.This is wrong!

3)Copernicus - Heliocentric solar system.

4)Tycho Brahe - collected much information about planetary motion.

5)Johannes Kepler - 3 laws of planetary motion.

- Planets travel in ellipes not circles.

6)Galileo - Different masses fall at the same rate .Periodic motion of objects under gravity.

Gravitational Machines.

1. Inclined plane - reducing the gravitational force by

building an inclined plane.The plane provides a "normal" force.

The inclined plane is a way of moving a mass upward against a

reduced force of gravity. The reduced gravity acts

downward parallel to the plane.

2. Weights and Pulleys - masses changing elevation in a gravitational field.

3 Water Wheels. [They are a reverse of windmills.]- water flowing down rivers.

4. Hydroelectric Dams - water flowing water down rivers.

5. Tidal power stations - sea water changing elevation because of the moon's gravity.

Information

Gravitational Systems.

[Systems where there are significant gravitational Fields

and masses that can move under gravity.]

gravitational machines can be built where there exists a "gravitational system".

A gravitational system exists where there are one or more very large masses that

produce a significant gravitational field.

Examples of gravitational systems are:

- The solar system

. - The earth and the moon.

- The surface of the earth and small "weights" above the surface.

[This webpage is under construction.

More information will be added later.]