binary number system

 

numeration system based on powers of 2, in contrast to the familiar decimal system, which is based on powers of 10. In the binary system, only the digits 0 and 1 are used. Thus, the first ten numbers in binary notation, corresponding to the numbers 0,1,2,3,4,5,6,7,8, and 9 in decimal notation, are 0,1,10,11,100,101,110,111,1000, and 1001. Since each position indicates a specific power of 2, just as the number 342 means (3 × 10²) + (4 × 10¹) + (2 × 10⁰), the decimal equivalent of a binary number can be calculated by adding together each digit multiplied by its power of 2; for example, the binary number 1011010 corresponds to (1 × 2⁶) + (0 × 2⁵) + (1 × 2⁴) + (1 × 2³) + (0 × 2²) + (1 × 2¹) + (0 × 2⁰) = 64 + 0 + 16 + 8 + 0 + 2 + 0 = 90 in the decimal system. Binary numbers are sometimes written with a subscript “b” to distinguish them from decimal numbers having the same digits. As with the decimal system, fractions can be represented by digits to the right of the binary point (analogous to the decimal point). A binary number is generally much longer than the decimal equivalent; e.g., the number above, 1011010_b, contains seven digits while its decimal counterpart, 90, contains only two. This is a disadvantage for most ordinary applications but is offset by the greater simplicity of the binary system in computer applications. Since only two digits are used, any binary digit, or bit, can be transmitted and recorded electronically simply by the presence or absence of an electrical pulse or current. The great speed of such devices more than compensates for the fact that a given number may contain a large number of digits.

A binary system is an astronomical term referring to two objects in space (usually stars, but also planets, galaxies or asteroids) which are so close that their gravitational interaction causes them to orbit about a common center of mass. Some definitions (e.g. that of double planet, but not that of binary star) require that this center of mass is not located within the interior of either object. A multiple system is like a binary system but consists of three or more objects.

In popular culture

Binary suns and star systems feature heavily in Star Wars, especially Revenge of the Sith and A New Hope.

In the Discovery program Alien Planet, the planet Darwin IV orbits a binary system.

References

• Astronomy: A Visual Guide by Mark A. Garlick

See also

• Binary asteroid
• Binary star
• Contact binary
• Contact binary (asteroid)
• Double planet

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