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  2. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    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).

  3. Faster-than-light - Wikipedia

    en.wikipedia.org/wiki/Faster-than-light

    Main article: Superluminal motion. In the context of this article, "faster-than-light" means the transmission of information or matter faster than c, a constant equal to the speed of light in vacuum, which is 299,792,458 m/s (by definition of the metre) [ 3 ] or about 186,282.397 miles per second. This is not quite the same as traveling faster ...

  4. Orders of magnitude (speed) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(speed)

    Typical scanning speed of an audio compact disc; the speed of signals (action potentials) traveling along axons in the human cortex. 1–1.5. 3.6–5.4. 2.2–3.4. 3.3–5.0 × 10 −9. Average walking speed—below a speed of about 2 m/s, it is more efficient to walk than to run, but above that speed, it is more efficient to run.

  5. Speed - Wikipedia

    en.wikipedia.org/wiki/Speed

    The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in vacuum c = 299 792 458 metres per second (approximately 1 079 000 000 km/h or 671 000 000 mph). Matter cannot quite reach the speed of light

  6. Rømer's determination of the speed of light - Wikipedia

    en.wikipedia.org/wiki/Rømer's_determination_of...

    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. The discovery is usually attributed to Danish astronomer Ole Rømer, [ note 1 ] who was working at the Royal Observatory in Paris at the time.

  7. Michelson–Morley experiment - Wikipedia

    en.wikipedia.org/wiki/Michelson–Morley_experiment

    They set a limit on the anisotropy of the speed of light resulting from the Earth's motions of Δc/c ≈ 10 −15, where Δc is the difference between the speed of light in the x- and y-directions. [33] As of 2015, optical and microwave resonator experiments have improved this limit to Δc/c ≈ 10 −18.

  8. Light - Wikipedia

    en.wikipedia.org/wiki/Light

    The speed of light in vacuum is defined to be exactly 299 792 458 m/s (approx. 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light. All forms of electromagnetic radiation move at exactly this same speed in vacuum.

  9. Fizeau's measurement of the speed of light in air - Wikipedia

    en.wikipedia.org/wiki/Fizeau's_measurement_of_the...

    At 3 times the speed it was again eclipsed. [3] [4] Given the rotational speed of the wheel and the distance between the wheel and the mirror, Fizeau was able to calculate a value of 2 × 8633m × 720 × 25.2/s = 313,274,304 m/s for the speed of light. Fizeau's value for the speed of light was about 5% too high. [5] The correct value is ...