Angstrom- Unit of measurement used to indicate specific points of wavelengths within the electromagnetic spectrum; aunit of length equal to 0.1 nm, or 104 m.

Are- A unit of surface area equal to 100 square meters.

Astronomical Unit- A standard unit of measure to represent the distances of objects within our solar system from the Sun.

ATM- Abbreviation for a standard atmosphere, a hypothetical vertical distribution of atmospheric temperature, pressure, and density that, by international agreement, is taken to be representative of the atmosphere for purposes of pressure altimeter calibrations, aircraft performance calculations, aircraft and missile design, and ballistic tables (Sea level values for: temperature 288.15 K (15°C), pressure 101325 Pa (1013.25 mb, 760 mm of Hg, or 29.92 in. of Hg), density 1225 g m (1.225 g L1), mean molar mass).

Atomic mass unit- A mass equivalent to one twelfth of the mass of on atom of carbon-12 or approximately 1.66 x 10 27 kg.