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  2. Light-second - Wikipedia

    en.wikipedia.org/wiki/Light-second

    The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. 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 ).

  3. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    The Jiffy is the amount of time light takes to travel one femtometre (about the diameter of a nucleon). The Planck time is the time that light takes to travel one Planck length. The TU (for time unit) is a unit of time defined as 1024 μs for use in engineering. The svedberg is a time unit used for sedimentation rates (usually

  4. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    The astronomical unit is used primarily for measuring distances within the Solar System or around other stars. It is also a fundamental component in the definition of another unit of astronomical length, the parsec. [6] One au is equivalent to 499 light-seconds to within 10 parts per million.

  5. Conversion of units - Wikipedia

    en.wikipedia.org/wiki/Conversion_of_units

    Conversion of units is the conversion of the unit of measurement in which a quantity is expressed, typically through a multiplicative conversion factor that changes the unit without changing the quantity. This is also often loosely taken to include replacement of a quantity with a corresponding quantity that describes the same physical property.

  6. Planck units - Wikipedia

    en.wikipedia.org/wiki/Planck_units

    One example is represented by the conditions in the first 10 −43 seconds of our universe after the Big Bang, approximately 13.8 billion years ago. The four universal constants that, by definition, have a numeric value 1 when expressed in these units are: c, the speed of light in vacuum, G, the gravitational constant, ħ, the reduced Planck ...

  7. Orders of magnitude (time) - Wikipedia

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

    The smallest meaningful increment of time is the Planck time―the time light takes to traverse the Planck distance, many decimal orders of magnitude smaller than a second. [ 1 ] The largest realized amount of time, based on known scientific data, is the age of the universe , about 13.8 billion years—the time since the Big Bang as measured in ...

  8. Solar radius - Wikipedia

    en.wikipedia.org/wiki/Solar_radius

    light-seconds Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun . The solar radius is usually defined as the radius to the layer in the Sun 's photosphere where the optical depth equals 2/3: [ 1 ]

  9. Lumen second - Wikipedia

    en.wikipedia.org/wiki/Lumen_second

    The use of the symbol T for talbots conflicts with T as the symbol for the tesla, the SI unit of magnetic flux density. The photometric unit lumerg [ 1 ] or lumberg , [ 2 ] proposed by the Committee on Colorimetry in 1937, correlates with the old CGS unit erg in the same way that the lumen second correlates with the radiometric unit joule , so ...