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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 ...
Because light travels about 300 000 kilometres (186 000 miles) in one second, these measurements of small fractions of a second must be very precise. The Lunar Laser Ranging experiment , radar astronomy and the Deep Space Network determine distances to the Moon, [ 90 ] planets [ 91 ] and spacecraft, [ 92 ] respectively, by measuring round-trip ...
186 282 mi 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 ).
The largest unit for expressing distances across space at that time was the astronomical unit, equal to the radius of the Earth's orbit at 150 million kilometres (93 million miles). In those terms, trigonometric calculations based on 61 Cygni's parallax of 0.314 arcseconds, showed the distance to the star to be 660 000 astronomical units (9.9 ...
Although most contemporary accounts used an Arabic mile of 6 444 feet (1,964 metres), which gave a Spanish league of the degree of 25,776 feet (7,857 metres or 4.242 modern nautical miles) others defined an Arabic mile as just 6,000 feet making a Spanish league of the degree 24,000 feet (or 7,315 metres, almost exactly 3.95 modern nautical miles).
kilometre (km) or kilometer is a metric unit used, outside the US, to measure the length of a journey; the international statute mile (mi) is used in the US; 1 mi = 1.609344 km; nautical mile is rarely used to derive units of transportation quantity.
Posidonius calculated the Earth's circumference by reference to the position of the star Canopus.As explained by Cleomedes, Posidonius observed Canopus on but never above the horizon at Rhodes, while at Alexandria he saw it ascend as far as 7 + 1 ⁄ 2 degrees above the horizon (the meridian arc between the latitude of the two locales is actually 5 degrees 14 minutes).
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 scope of the Solar System and is about 3.26 light-years: 1 pc = 1 au/tan(1″) [6] [61] Proxima ...