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  2. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    The product of Simon Newcomb's J1900.0 mean tropical year of 31 556 925.9747 ephemeris seconds and a speed of light of 299 792.5 km/s produced a light-year of 9.460 530 × 10 15 m (rounded to the seven significant digits in the speed of light) found in several modern sources [10] [11] [12] was probably derived from an old source such as C. W ...

  3. 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).

  4. Light-second - Wikipedia

    en.wikipedia.org/wiki/Light-second

    It is defined as the distance that light travels in free space in one second, and is equal to exactly 299 792 458 m (approximately 983 571 055 ft or 186 282 miles). Just as the second forms the basis for other units of time, the light-second can form the basis for other units of length, ranging from the light-nanosecond (299.8 mm or just under ...

  5. Speed of gravity - Wikipedia

    en.wikipedia.org/wiki/Speed_of_gravity

    metres per second: 299 792 458: Approximate values (to three significant digits) 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 ...

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

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

    By timing the eclipses of Jupiter's moon Io, Rømer estimated that light would take about 22 minutes to travel a distance equal to the diameter of Earth's orbit around the Sun. [1] Using modern orbits, this would imply a speed of light of 226,663 kilometres per second, [2] 24.4% lower than the true value of 299,792 km/s. [3]

  7. List of spaceflight records - Wikipedia

    en.wikipedia.org/wiki/List_of_spaceflight_records

    The Apollo 10 crew (Thomas Stafford, John W. Young and Eugene Cernan) achieved the highest speed relative to Earth ever attained by humans: 39,897 kilometers per hour (11,082 meters per second or 24,791 miles per hour, about 32 times the speed of sound and 0.0037% of the speed of light). [14] The record was set 26 May 1969. [14]

  8. Astronomers Found the Ancient Light Source That Literally ...

    www.aol.com/astronomers-found-ancient-light...

    This is the first time that these galaxies have been imaged in such detail, and the first time scientists were able to confirm that they produced enough radiation to end the light-less tyranny of ...

  9. Metre per second - Wikipedia

    en.wikipedia.org/wiki/Metre_per_second

    The metre per second is the unit of both speed ... of the speed of light. The SI unit symbols are m/s, m·s −1, m s −1, or ... ≈ 2.2369 miles per hour ...