The speed of light in a vacuum is 299 792 458 meters per second or 983,571,056.43045 feet per second or 186,282.397 miles per second or 670,616,629.2 miles per hour.
Chat with our AI personalities
Yes. No experimental evidence has ever been found that would suggest that any wavelength of light travels at a different speed than any other. We speak, of course, only about electromagnetic radiation in a vacuum.
The speed of light in vacuum, usually denoted by c, is a universal physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time.[1] In imperial units this speed is approximately 186,282 miles per second.
The speed of light can be both calculated and measured. Light waves are formed by mutually interacting orthogonal electric and magnetic fields. Using properties of these electric and magnetic fields, you can arrange the equations of physics into a partial differential equation, called the "wave equation". This equation contains a constant in it, which is the wave-speed of light. It's value is found from other physical constants, and is about 3 106 km/sec. This value was measured in a vacuum and found to be within excellent agreement. James Clerk Maxwell first theoretically found the speed of light from what is now called the Maxwell equations.
It means the same as in everyday use. It means unchanging, unvarying. Fixed. So for example the speed of light in a vacuum is called a universal constant because it is a fixed value. It is the opposite of a variable (something that changes).
A great question. First--It isn't always constant. Light can travel slower than "c" ("the speed of light"). In a perfect vacuum light travels at "c". It's slower in glass, air, water, etc., light can even stop! But "c" is the upper speed limit. Second--Not only light but ANY disturbance in the universe has a speed limit of "c". Even the influence of gravity travels at the speed of light. Third--Einstein didn't just wake up one day with a good idea. The constancy of the speed of light (and relativity in general) explained many curious observations that had been made, and solved many physics problems. Fourth--There have been competing theories that allow a variable "c" but all the experiments indicate that it is indeed a constant value.