Search results
Results from the WOW.Com Content Network
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 imagined to be swept from one object to shine on a second object. The farther the two objects are away ...
For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200 000 km/s (124 000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.
The measurements of speed of light are also mentioned only to the minimum extent, i.e. when they proved for the first time that c is finite and invariant. Innovations like the use of Foucault's rotating mirror or the Fizeau wheel are not listed here – see the article about speed of light. This timeline also ignores, for reasons of volume and ...
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.
For premium support please call: 800-290-4726 more ways to reach us
Einstein's special theory is not the only theory that combines a form of light speed constancy with the relativity principle. A theory along the lines of that proposed by Heinrich Hertz (in 1890) [ 17 ] allows for light to be fully dragged by all objects, giving local c-constancy for all physical observers.
Ole Rømer (1644–1710) became a government official in his native Denmark after his discovery of the speed of light (1676). The engraving is probably posthumous. Rømer's determination of the speed of light was the demonstration in 1676 that light has an apprehensible, measurable speed and so does not travel instantaneously.
In 1992, John Moffat proposed that the speed of light was much larger in the early universe, in which the speed of light had a value of more than 10 30 km/s. [2] He published his " variable speed of light " (VSL) theory in two places—on the Los Alamos National Laboratory's (LANL) online archive, 16 Nov. 1992, [ 4 ] and in a 1993 edition of ...