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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).
One furlong per fortnight is a speed that would be barely noticeable to the naked ... 3.720 × 10 −4 mph, the speed of the tip of a 3 + 3 ... The speed of light is ...
The speed of light is 299,792,458 metres per second (983,571,056 ft/s), or about one foot per nanosecond. If it were exactly one foot per nanosecond, and a target was one data mile away, then the radar return from that target would arrive 12 microseconds after the transmission.
Speed; system unit code (alternative) symbol or abbrev. notes sample default conversion combinations SI: metre per second: m/s m/s US spelling: meter per second 1.0 m/s (3.3 ft/s)
Formally, c is a conversion factor for changing the unit of time to the unit of space. [4] This makes it the only speed which does not depend either on the motion of an observer or a source of light and / or gravity. Thus, the speed of "light" is also the speed of gravitational waves, and further the speed of any massless particle.
The speed of light in vacuum is defined to be exactly 299 792 458 m/s (approximately 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light. All forms of electromagnetic radiation move at exactly this same speed in vacuum.
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.
A value of 9.460 536 207 × 10 15 m found in some modern sources [15] [16] is the product of a mean Gregorian year (365.2425 days or 31 556 952 s) and the defined speed of light (299 792 458 m/s). Another value, 9.460 528 405 × 10 15 m, [17] is the product of the J1900.0 mean tropical year and the defined speed of light.