# Vi Hart explains logarithms

**doctorow**#1

**AST30060**#4

Girls, I know you will understand this and feel the intrinsic, incredible emotion

You have just pulled over your head the worn, warm sweater belonging to a boy…

I always thought logarithms were what lumberjacks danced to.

Seriously, that explains why I punch “1000” into my calculator and press “log” and the answer comes back, “3”…guess my calculator thinks in base 10.

**Chentzilla**#8

This book was cooler:

Also, can anyone tell if those videos work not only as musings for the ones who already know what she’s talking about, but as actual learning videos as well?

**Boundegar**#9

Yes, log is usually base 10, ln is base e. Base 2 is useful too, but you have to figure it yourself.

**amadaden**#10

The calculator thinks in base 2 but it’s smart enough to know that if you need to use a calculator your probably human, and if your human you probably think in base 10.

**bobizumi**#11

Finally doing math using a slide rule makes some kind of sense. The magic is gone… truth is revealed. Thanks logarithms, Thanks Vi!

**enceladus**#12

Mathematicians reserve unadorned “log” for the natural logarithm, having little use for other bases. Scientists and engineers use “log” for base 10 and require “ln” for the natural log; “lg” is base 2, especially in computer science.

The decibel scale is logarithmic, defined as log base 10, but then multiplied by 10. Essentially this is base 10^(1/10) ~= 1.25892541179.

Suppose you have some calculator with a log key, but you don’t know what base it’s in – can you find the logarithm of *x* with respect to a particular base *b*? This is easy – just key in (log *x*)/(log *b*).

[/ log facts]

**LizColeman**#13

Well, for me, someone for whom “log” was just a button on a calculator, I learned a lot. When she crosses out the letters at the end and writes in “log,” something magical happened, and I understood.

**Boundegar**#14

I guess my engineering background shows. I have never seen “lg,” maybe it’s after my time.

**doctorow**closed #15

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