⁴ Of course, this isn’t very helpful if you don’t remember what a “natural logarithm” is. A logarithm (the symbol for which is log) is the “opposite” of raising something to a power. So if 10³ = 1000, log₁₀1000 = 3 (this is usually referred to as the logarithm “to the base 10”). The “natural logarithm” is the logarithm taken to the base of the rather odd-looking number e = 2.71828182845904523536…. We’ll defer the mystery of why this particular number is so “natural” to the next chapter.