Meter

Definition

A meter is the base unit of length in the International System of Units (SI). It is defined as the distance light travels in a vacuum in 1/299,792,458 seconds.

5 Must Know Facts For Your Next Test

1. The meter was originally defined based on a fraction of the Earth's meridian but has since been redefined using the speed of light.
2. The symbol for meter is 'm'.
3. One meter is equivalent to 100 centimeters or 1,000 millimeters in the metric system.
4. Precise measurement techniques using lasers and atomic clocks are employed to ensure accuracy in defining the meter.
5. The definition of a meter is crucial for maintaining consistency across scientific research and engineering projects.

Review Questions

• How is a meter currently defined in terms of the speed of light?
• What are two smaller units derived from a meter?
• Why was it necessary to redefine the meter from its original Earth-based definition?

Related terms

Second:

The base unit of time in SI, defined by taking the fixed numerical value of the cesium frequency $\Delta \nu_{Cs}$, which corresponds to transitions between two hyperfine levels of the ground state of cesium-133.

Kilogram:

The base unit of mass in SI, defined by setting the Planck constant $h$ to exactly $6.62607015 \times 10^{-34}$ joule-seconds ($Js$).

Speed of Light: $c$, a fundamental physical constant representing how fast light travels in a vacuum; precisely $299,792,458$ meters per second.