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The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour). [Note 3] According to the special theory of relativity, c is the upper limit for the speed at which ...
Time dilation. Time dilation is the difference in elapsed time as measured by two clocks, either because of a relative velocity between them ( special relativity ), or a difference in gravitational potential between their locations ( general relativity ). When unspecified, "time dilation" usually refers to the effect due to velocity.
Cherenkov radiation glowing in the core of the Advanced Test Reactor at Idaho National Laboratory. Cherenkov radiation (/ tʃ ə ˈ r ɛ ŋ k ɒ f / [1]) (also known as Čerenkov or Cerenkov radiation [2]) is electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium (such as distilled water) at a speed greater than the phase velocity ...
Faster-than-light ( superluminal or supercausal) travel and communication are the conjectural propagation of matter or information faster than the speed of light ( c ). The special theory of relativity implies that only particles with zero rest mass (i.e., photons) may travel at the speed of light, and that nothing may travel faster.
Theorized. 1967. A tachyon ( / ˈtækiɒn /) or tachyonic particle is a hypothetical particle that always travels faster than light. Physicists believe that faster-than-light particles cannot exist because they are inconsistent with the known laws of physics. [ 1][ 2] If such particles did exist they could be used to send signals faster than light.
Subsonic. Mach 1. Supersonic. Shock wave. The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first approached the speed of sound, these effects were seen as constituting a barrier, making faster ...
Superluminal communication is a hypothetical process in which information is conveyed at faster-than-light speeds. The current scientific consensus is that faster-than-light communication is not possible, and to date it has not been achieved in any experiment. Superluminal communication other than possibly through wormholes is likely impossible ...
Lighthouse paradox. Observed distance traveled by light (from left to right) as light source rotates. At a sufficient distance, the speed at which the beam "moves" may exceed the speed of light. The lighthouse paradox is a thought experiment in which the speed of light is apparently exceeded. The rotating beam of light from a lighthouse is ...