Remember that we are using natural logarithms, where the base is e ≈ 2.71828. Logarithms may have other bases, for instance the decimal logarithm of base 10. (The base 10 logarithm is used in the definition of the Richter scale, for instance, measuring the intensity of earthquakes as Richter = log(intensity). This is why an earthquake of magnitude 9 is 100 times more powerful than an earthquake of magnitude 7: because 109/107 = 102 and log10(10 2) = 2.)