The theory of special relativity is rife with counterintuitive and surprising effects, the most famous of which are length contraction and time dilation. If an object travels at a relative speed ...

In the realm of physics, the speed of light is considered one of the most fundamental constants in the universe, dictating ...

Discover how Einstein’s theory of special relativity reshaped physics by linking space, time, mass, and energy in a universe governed by the speed of light.

The speed of gravity not only equals the speed of light to an incredibly precise degree observationally, but these two constants must be exactly equal theoretically, or General Relativity would ...

Special relativity also affects many other things physicists measure—for example, the frequency and intensity of light and also the size of an object’s appearance.

Consider two clocks, one located at the North or South Pole, and the other at the equator. The clock at the equator would tick slower because of its relative speed due to Earth’s spin, but faster ...

Everyone knows that relativity plays hell with time, and that it can do a number on space, but what about mass? Why do objects get more or less mass depending on their relative speed?

In a vacuum, the speed of light is about 186,000 miles per second (300,000 kilometers per second). If it were orders of magnitude slower, humans would immediately take notice.

Hawking and Milner’s plan was to build thousands of tiny spacecraft the size of microchips and use light to accelerate them to a relativistic speed—one this close to the speed of light.