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speed of light

The speed of light in free space (that is, in a vacuum) is a constant that has been measured to considerable accuracy. To nine significant figures, it is 299,792,458 meters per second (2.99792458 x 10 8 m/s). This is the speed with which all electromagnetic field s, including radio waves, infrared (IR), ultraviolet (UV), X rays, and gamma rays, propagate in a vacuum. The constant is symbolized c .

The speed of light seems, for most everyday purposes, infinite. But the true finiteness of its speed becomes apparent in satellite communications, particularly when geostationary satellites are used. These satellites orbit approximately 36,000 kilometers (km) above the Earth. The propagation delay can be noticed as increased latency when satellite Internet services are used. Electromagnetic waves, including visible light, take approximately 1.3 s to traverse the distance between the Earth and the moon, and about eight minutes (8 min) to get from the sun to the Earth. The EM waves from stars in our galaxy can take up to thousands of years to reach us; the EM waves from the most distant known objects in the Cosmos have spent billions of years on their way to us (where one billion defined as 1,000,000,000 or 10 9 ).

The speed of light in free space is independent of the relative velocity between the source and the observer. Some people find this counterintuitive, but it has been demonstrated by experiments. The most famous such experiment was conducted by two physicists, Albert Michelson and Edward Morley, in the late 1800s. They found that the speed of light is the same in all directions, despite the fact that the Earth moves through space.

Also see our Table of Physical Units and Constants.

This was last updated in December 2007

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Secrets of the Universe
In the beginning was infinite geometric space. This space became filled with Static Time at absolute rest and absolute cold. Static time is strictly quantitative, and does not differentiate between past, present and future. Being quantifiable and measurable, static time is a scientific concept. Static time of 0.0033 microseconds per meter will be measured regardless of the direction chosen.
Stars move through static time, which does not disrupt their motion. Static time exists but is imperceptible. Static time is the deepest secret of the universe.
Static time fills all infinite space, eliminating the possibility of a vacuum. Static Time Waves (STW) travel through static time. The speed of STW is 300,000 km/second.
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The Newtonian universe is based on matter and force.
The Einsteinian universe is based on matter and energy.
The Aetzbarian universe is based on static time and energy.
There is no gravity, and there is no gravity waves.
There is Static Time , and there is Static Time Waves. (STW)
There is a particles of Static Time.
Static Time is real and measured.
Everyone knows the Dynamic Time.
It is time to recognize the Static Time.
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