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bold, wikify, remove redundancy and familiar language
A logarithm of a number is the exponential power to which you raise the base to obtain the number.
A '''logarithm''' of a [[number]] is the [[exponential]] power to which you raise the base to obtain the number.
For high school algebra, the most common base is "10". For base 10, the definition becomes as follows: A logarithm of a number is the power to which you raise 10 to obtain the number.
For high school [[algebra]], the most common base is "10".
For example, the logarithm of 100 is the power to which you raise 10 to obtain 100. Because 10 to the power of 2 equals 100, the logarithm of 100 is 2:
For example, the logarithm base 10 of 100 is the power to which you raise 10 to obtain 100. Because 10 to the power of 2 equals 100, the logarithm of 100 is 2:
log 100 = 2 because 10<sup>2</sup> = 100
log 100 = 2 because 10<sup>2</sup> = 100
==History==
==History==
Logarithms were used for centuries as a computing tool by [[scientist]]s making pencil-and-paper [[computation]]s.
Logarithms were invented or discovered by [[John Napier]] in 1614 AD, and quickly revolutionized astronomy. Johannes Kepler said that Napier "tripled the life of an astronomer."
Logarithms were invented or discovered by [[John Napier]] in 1614 AD, and quickly revolutionized astronomy. Johannes Kepler said that Napier "tripled the life of an astronomer."
For centuries, tables of logarithms were working tools of the scientist and engineer. Students and people doing rough calculations typically used a "table of four-place logarithms," which would fit on one or two pages. Such tables were printed in the back of virtually every physics book. For more precise work, longer tables with more places of precision were used, or entire volumes.
For centuries, tables of logarithms were working tools of the scientist and engineer. Students and people doing rough calculations typically used a "table of four-place logarithms," which would fit on one or two pages. Such tables were printed in the back of virtually every [[physics]] book. For more precise work, longer tables with more places of precision were used, or entire volumes.
Closely associated with logarithms was a tool called the ''slide rule.'' A slide rule consists of ruled logarithmic scales. By manipulating the slide rule, one can graphically add together the logarithm of two numbers, which is equivalent to multiplying them. From about 1870 AD to 1970 AD, slide rules were used by virtually every scientist and engineer. They were regarded as a symbol of engineering. Engineering students were identifiable by the ten-inch slide rules attached to their belts. Learning to use a slide rule was a fundamental skill taught in high-school mathematics classes.
Closely associated with logarithms was a tool called the ''slide rule.'' A slide rule consists of ruled logarithmic scales. By manipulating the slide rule, one can graphically add together the logarithm of two numbers, which is equivalent to multiplying them. From about 1870 AD to 1970 AD, slide rules were used by virtually every scientist and engineer. They were regarded as a symbol of engineering. Engineering students were identifiable by the ten-inch slide rules attached to their belts. Learning to use a slide rule was a fundamental skill taught in high-school mathematics classes.