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A light-year, alternatively spelled light year (ly or lyr [3]), is a unit of length used to express astronomical distances and is equal to exactly 9 460 730 472 580.8 km, which is approximately 9.46 trillion km or 5.88 trillion mi.
Light-year: 63 241 — Distance light travels in one Julian year (365.25 days) — Oort cloud: 75 000: ± 25 000: 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 ...
where θ is the measured angle in arcseconds, Distance earth-sun is a constant (1 au or 1.5813 × 10 −5 ly). The calculated stellar distance will be in the same measurement unit as used in Distance earth-sun (e.g. if Distance earth-sun = 1 au , unit for Distance star is in astronomical units; if Distance earth-sun = 1.5813 × 10 −5 ly, unit ...
Earth radius R 🜨 ≈ 6,371 km [14] Lunar distance LD ≈ 384 402 km. [15] Average distance between the center of Earth and the center of the Moon. 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.
For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200 000 km/s (124 000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.
1.0 h (4 in; 10 cm) inch: in in Use of ′ and ″ symbols violates MOSNUM so is not provided. 1.0 in (25 mm) in cm; in mm; Maritime units: nautical mile: nmi nmi the international standard nautical mile 1.0 nmi (1.9 km; 1.2 mi) nautical mile: oldUKnmi (admiralty nmi) nmi 6080 ft the pre-1970 British nautical mile: 1.0 nmi (1.9 km; 1.2 mi ...
It would be exactly 1 km if the original definition of 1 metre = 1 ⁄ 10,000 quarter-meridian had been adhered to. One disadvantage is that common angles like 30° and 60° are expressed by fractional values ( 33 + 1 ⁄ 3 and 66 + 2 ⁄ 3 respectively) so this "decimal" unit failed to displace the "sexagesimal" units equilateral-vertex ...
Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe.They are often used to tie some observable quantity (such as the luminosity of a distant quasar, the redshift of a distant galaxy, or the angular size of the acoustic peaks in the cosmic microwave background (CMB) power spectrum) to another quantity that is ...