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  2. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    A light-year is the distance light travels in one Julian year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. In round figures, a light year is nearly 10 trillion kilometres or nearly 6 trillion miles. Proxima Centauri, the closest star to Earth after the Sun, is around 4.2 light-years away. [89]

  3. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    The Andromeda Galaxy is approximately 2.5 million light-years away. 3 × 10 6 ly: The Triangulum Galaxy , at about 3 million light-years away, is the most distant object visible to the naked eye. 5.9 × 10 7 ly: The nearest large galaxy cluster, the Virgo Cluster, is about 59 million light-years away. 1.5 × 10 8 – 2.5 × 10 8 ly

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

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

    [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 4.5% too high. [5] The correct value is 299,792,458 m/s.

  5. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    Distance of the outer limit of Oort cloud from the Sun (estimated, corresponds to 1.2 light-years) — Parsec: 206 265 — One parsec. The parsec is defined in terms of the astronomical unit, is used to measure distances beyond the scope of the Solar System and is about 3.26 light-years: 1 pc = 1 au/tan(1″) [6] [61] Proxima Centauri: 268 000 ...

  6. Orders of magnitude (speed) - Wikipedia

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

    To help compare different orders of magnitude, the following list describes various speed levels between approximately 2.2 × 10 −18 m/s and 3.0 × 10 8 m/s (the speed of light). Values in bold are exact.

  7. Speed of gravity - Wikipedia

    en.wikipedia.org/wiki/Speed_of_gravity

    kilometres per hour: 1 080 000 000: miles per second: 186 000: miles per hour [1] 671 000 000: astronomical units per day: 173 [Note 1] parsecs per year: 0.307 [Note 2] Approximate light signal travel times; Distance: Time: one foot: 1.0 ns: one metre: 3.3 ns: from geostationary orbit to Earth: 119 ms: the length of Earth's equator: 134 ms ...

  8. Foucault's measurements of the speed of light - Wikipedia

    en.wikipedia.org/wiki/Foucault's_measurements_of...

    He used carefully calibrated tuning forks to monitor the rotation rate of the air-turbine-powered mirror R, and he would typically measure displacements of the slit image on the order of 115 mm. [7] His 1879 figure for the speed of light, 299944±51 km/s, was within about 0.05% of the modern value. His 1926 repeat of the experiment incorporated ...

  9. List of unusual units of measurement - Wikipedia

    en.wikipedia.org/wiki/List_of_unusual_units_of...

    The light-nanosecond is defined as exactly 29.9792458 cm. It was popularized in information technology as a unit of distance by Grace Hopper as the distance which a photon could travel in one billionth of a second (roughly 30 cm or one foot): "The speed of light is one foot per nanosecond." [6] [7]