What is the theory of relativity?

The theory of relativity is a physical theory of time and space established by Albert Einstein, and is largely divided into two: the special theory of relativity and the general theory of relativity[.

 

Special theory of relativity (published in 1905)

The laws of physics apply equally in all inertial frames (coordinate systems moving at a constant speed).

The speed of light is always constant for all observers.

 

As a result, time passes more slowly (time dilation) and lengths shorten (length contraction) for fast-moving objects.

Mass and energy can be converted into each other, and this can be expressed in the formula E=mc^2.

 

General theory of relativity (published in 1915)

Gravity is explained as the curvature of spacetime. In other words, a massive object warps the spacetime around it, and this curvature appears as gravity.

 

Time flows more slowly in places where gravity is stronger. It is used to explain various phenomena in the universe, such as black holes and gravitational lenses.

 

Key Summary

Time and space are not absolute, but change relatively depending on the movement of the observer and gravity.

The theory of relativity is an essential theory for modern science and technology, such as GPS and space exploration.

 

> “The theory of relativity was created to resolve serious and deep contradictions in old theories that seemed to have no breakthrough.”

> - Einstein, from Evolution of Physics