Reference Values

Speed of Light & other Electromagnetic waves: 2.998 x 10⁸ m/s
Avogadro's Constant: 6.02 x 10²³ - the number of particles (atoms or molecules) in one mole of any pure substance.
Speed of Sound: 340.29 m/s at "Standard temperature and pressure"
Gravity (acceleration due to,): 9.80665 m/s² (Average) on Earth. Lowest gravity is in Mexico City (9.779 m/s²) and highest in Oslo (Norway) and Helsinki (Finland) (9.819 m/s²).; 1.622 m/s² on Earth's Moon. See also: Planetary Fact Sheet from NASA.; 274.1 m/s² on the surface of the Sun.