|≈||approximately equal to|
|digits||indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …)|
The speed of light in vacuum, commonly denoted c, is a universal physical constant important in many areas of physics. Its exact value is 299,792,458 metres per second (approximately 3.00×108 m/s, or 186,282 mi/s); it is exact because the unit of length, the metre, is defined from this constant and the international standard for time.
The knot (/nɒt/) is a unit of speed equal to one nautical mile (1.852 km) per hour, approximately 1.15078 mph. The ISO Standard symbol for the knot is kn. The same symbol is preferred by the Institute of Electrical and Electronics Engineers (IEEE); kt is also common.