Search results
Results From The WOW.Com Content Network
The light-year unit appeared in 1851 in a German popular astronomical article by Otto Ule. [24] Ule explained the oddity of a distance unit name ending in "year" by comparing it to a walking hour (Wegstunde). A contemporary German popular astronomical book also noticed that light-year is an odd name. [25]
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.
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
The astronomical unit of length is now defined as exactly 149 597 870 700 meters. [4] It is approximately equal to the mean Earth–Sun distance. It was formerly defined as that length for which the Gaussian gravitational constant (k) takes the value 0.017 202 098 95 when the units of measurement are the astronomical units of length, mass and ...
To help compare different distances this section lists lengths starting at 10 15 m (1 Pm or 1 trillion km or 6685 astronomical units (AU) or 0.11 light-years).
astronomical unit au. Defined as 149 597 870 700 m. [16] Approximately the distance between the Earth and Sun. light-year ly ≈ 9 460 730 472 580.8 km. The distance that light travels in a vacuum in one Julian year. [17] parsec pc ≈ 30 856 775 814 671.9 km or about 3.261 56 ly; Hubble length 14.4 billion light-years or 4.55 gigaparsecs
light-year (ly) A unit of length used to express astronomical distances that is equivalent to the distance that an object moving at the speed of light in vacuum would travel in one Julian year: approximately 9.46 trillion kilometres (9.46 × 10 12 km) or 5.88 trillion miles (5.88 × 10 12 mi).
The unit was introduced to simplify the calculation of astronomical distances from raw observational data. Partly for this reason, it is the unit preferred in astronomy and astrophysics, though in popular science texts and common usage the light-year remains prominent.