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Beaufort scale. A ship in a force 12 (" hurricane -force") storm at sea, the highest rated on the Beaufort scale. The Beaufort scale / ˈboʊfərt / is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale .
0.44704. Miles per hour ( mph, m.p.h., MPH, or mi/h) is a British imperial and United States customary unit of speed expressing the number of miles travelled in one hour. It is used in the United Kingdom, the United States, and a number of smaller countries, most of which are UK or US territories, or have close historical ties with the UK or US.
The kilometre, a unit of length, first appeared in English in 1810, [ 9] and the compound unit of speed "kilometers per hour" was in use in the US by 1866. [ 10] ". Kilometres per hour" did not begin to be abbreviated in print until many years later, with several different abbreviations existing near-contemporaneously. 1903: "KMph."
≈ 1 hour walk, Currently defined in US as 3 Statute miles, [3] but historically varied from 2 to 9 km ≈ 4828 m: light-day ≡ 24 light-hours ≡ 2.590 206 837 12 × 10 13 m: light-hour ≡ 60 light-minutes ≡ 1.079 252 8488 × 10 12 m: light-minute ≡ 60 light-seconds ≡ 1.798 754 748 × 10 10 m: light-second
The knot ( / nɒt /) is a unit of speed equal to one nautical mile per hour, exactly 1.852 km/h (approximately 1.151 mph or 0.514 m/s ). [ 1][ 2] The ISO standard symbol for the knot is kn. [ 3] The same symbol is preferred by the Institute of Electrical and Electronics Engineers ( IEEE ), while kt is also common, especially in aviation, where ...
A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute ( 1 / 60 of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).
The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour). [Note 3] According to the special theory of relativity, c is the upper limit for the speed at which ...
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 ...