# How long is one meter?

Classical Mechanics Level 1

The metre (International spelling as used by the International Bureau of Weights and Measures), or meter (American spelling), (SI unit symbol: m), is the fundamental unit of length (SI dimension symbol: L) in the International System of Units (SI). What has been the definition of the meter since $$1983$$ by the International System of Units?

a) The length of the path traveled by light in a vacuum for $$\frac{1}{299,792,458}$$ of a second

b) One ten-millionth of the distance between the earth's equator and the North Pole (at the sea level)

c) The length of a pendulum with a half-period of one second

d) $$1,650,763.73$$ wavelengths of the orange-red emission line in the electromagnetic spectrum of the krypton-$$86$$ atom in a vacuum

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