Classical Relativity:

Galileo Galilei first proposed relativity in Inertial Frames (motion is relative).

The Galilean Transform is used to switch between Inertial Frames.

Isaac Newton's Laws of Motion always apply in Inertial Frames.

​ - Assumes Absolute Time and Space (Meaning an absolute frame of reference)

Newton's Laws of Motion also apply in other frames, but cannot use the Galilean Transform for non-inertial frames (accelerating frames).

Classical Gravity:

Newton proposed that gravity is a force that acts at a distance that is inversely proportional to the square of the distance, and proportional to the objects' mass.

Electromagnetism-Light Theory:

Thomas Young proved light exhibited wave-like properties using the Double-Slit Experiment in 1801.

James Clerk Maxwell used Electric and Magnetic equations of his time and synthesized calculations for 3D space using Calculus.

Using these equations, Maxwell proved the speed of light is constant.

Newtonian Relativity predicts that light should be faster if the object emitting it is moving, contrary to Maxwell's discovery.

Luminiferous Ether and Lorentz:

Albert A. Michelson and Edward W. Morley experimentally determined the speed of light doesn't change with motion, confirming Maxwell's solution.

Hendrik Lorentz proposed a medium for light that isn't dragged by mass, opposed to Augustin Fresnel's Ether Drag theory, but is fixed to space instead.

Lorentz formulated that velocity should result in time dilation and length contraction (That objects moving fast would experience time slower and would be squished in the direction of motion).

The Theory of Special Relativity:

Einstein proposed a new way of looking at Galileo's Relativity.

Instead of the Galilean Transform, frames are transformed by the Lorentz Factor.

- The Lorentz Factor keeps the speed of light constant.

As mentioned before, objects moving through space experience time slower to an observer at rest, as well as contract in the direction of their velocity.

Simultaneity in space no longer is assumed, but rather all events are constant but will be observed by differing frames as occurring at a different time.

Massive objects cannot travel at the speed of light.

Massless object have to travel at the speed of light.

The conservation of Energy and Momentum are approximations of a larger fundamental conservation of Energy-Momentum.

General Relativity:

Einstein proposed the Equivalence principle (that acceleration in free space is no different than a gravitational field).

Since both frames are the same, light is bent in a gravitational field, even without mass to apply a force.

A new idea formed that Gravity is actually the curvature of space-time, meaning that light travels in a straight line to itself, but on a curves surface appears to change direction.

Solutions to General Relativity:

Einstein-Rosen Bridge (aka Wormholes) that could warp space so much as to travel vast distances without going far.

Blackholes were one of the first things synthesized, but wasn't proven to exist until 2019 with the picture taken by the New Horizons Telescope.

Mercury's precession around the sun was explained by GR, which baffled people under Newton's interpretation of gravity.

Gravitational waves as the result of space-time itself creating waves was theorized by Einstein, but was only observed by LIGO and Virgo in 2015 and 2017.