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In 1905 Albert Einstein explained the constancy of the
(link popup window: speed_of_light.html) *speed of light*
with his theory of . Einstein proposed that ether does not exist and that light has the same speed (3 x 10^8 m/s)
in all inertial reference frames.
In other words, the speed of light is the same for all observers,
regardless of the motion of the observer or the light source.
The speed of light is calculated as the distance travelled by light divided by the time taken to travel that distance. In order to make a consistent theory, Einstein had to modify the basic concepts of "length" and "time" that are contained within the definition of velocity. One consequence of these changes in our understanding of space and time was the realization that nothing could go faster than the speed of light. One way to understand this is to note that in Special Relativity the mass of an object increases with its velocity. When an object moves at the speed of light its mass becomes infinite. Therefore, to make it move faster would require infinite energy. This increase in mass with velocity has now been verified many times in particle physics experiments. Photons of light can move at the speed of light as they have no mass. The consequence of Special Relativity for objects whose escape velocity is equal to, or greater than, the speed of light is profound. Since the speed of light is the maximum speed of any object, an object with an escape velocity that great can emit no radiation of any kind. Indeed, no information of any kind can be transmitted from such an object to the outside world. Thus such an object is in a philosophical sense not part of our Universe, in that no event that occurs on or inside it can be seen or in any way detected in any way by any conceivable experiment that can be conducted in our Universe. |
(link popup window: http://archive.ncsa.uiuc.edu/Cyberia/NumRel/NumRelHome.html) *Spacetime Wrinkles*: a page on Special Relativity.
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