3: The curvy line turned into a straight line!

You probably noticed the curvy line on the original graph turned into a straight line on the
log transformed graph

no transformation with transformation

Why does this happen? Consider the following 2 facts:

1. As you increase a log by 1, you’re increasing the magnitude of the original measurement by a factor of 10.
2. When you allow an additional unit of time to go by (in this case, half a day), you’re allowing the bacteria to increase by a factor of 10.

Taking the log accounts for the multiplying nature of bacterial growth and all you’re left with on the
graph is a straight line, pointing upwards.

"germs are everywhere
When growth happens by multiplying the population by a constant number each timestep, we call that
exponential growth
. Any time you have exponential growth, taking the log of the population size will turn
the graph into a straight line
. This is true even if the constant multiplier is not 10 — in that case, your straight line will
have a different slope, but it will still be straight.