A light-second is a
unit of length. It is defined as the distance lighttravels in an absolute vacuumin one secondor 299,792,458 meters. Note that this value is considered exact, since the meter is actually (as of 1983) defined in terms of the light second. [ [http://inms-ienm.nrc-cnrc.gc.ca/research/optical_frequency_si_e.html] National Research Council of Canada: "Optical frequency - maintaining the SI metre"] It is just over 186,282 miles and almost 109 feet.
light-minuteis 60 light-seconds and a light-houris 60 light-minutes, or 3600 light-seconds. A light-yearis 31,557,600 light-seconds.
Some distances in light seconds:
* The mean diameter of the
Earthis about 0.0425 light-seconds.
* The mean distance, over land, between opposite sides of the planet
Earthis about 0.0668 light-seconds (which also means that communications between opposite sides of the planet, taking a circumferential path, can never travel faster than about 67 milliseconds).
Communications satellites are typically 0.001334s ( low earth orbit) to 0.1194s ( geostationary orbit)
* The average distance from the Earth to the
Moonis about 1.282 light-seconds.
* The diameter of the
Sunis about 4.643 light-seconds.
* The average distance from the Earth to the Sun (i.e. 1
astronomical unit) is 499.0 light-seconds, or 8.317 light-minutes.
It is also possible to add diminutive suffixes, such as the light-
nanosecond, equal to almost exactly 30 cm (11.8 in or nearly a foot).
Speed of light
1 E8 m
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light second — a unit of distance equal to the distance light travels in a vacuum in one second. In accordance with the official definition of the meter, this distance is exactly 299 792 458 meters (about 186 282.4 miles). Similarly, a light minute is 60… … Dictionary of units of measurement
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