Consider an E. coli … measuring 0.000002 m. It would be easy to say log (0.000001) = −6 … but E. coli are bigger than that. Not big enough to get to a log scale number of −5, but between − 6 and − 5. In fact,
log (0.000002) = −5.7 (E. coli)
Likewise, red blood cells have a diameter of 0.000007 m, so they are also between – 6 and – 5 on a log scale:
log (0.000007) = −5.2 (red blood cell)
Using the log scale, you can tell that E. coli are smaller than red blood cells, because −5.7 is less than −5.2.
Now that we know that normal red blood cells are approximately −5.2 on a log scale, we can also guess that a blood cell that has diameter with log of −4 is going to be very problematic for the poor creature whose capillaries get exploded by it. And a red blood cell that has a diameter with log of −6 will be too tiny to do any good.
A red blood cell diameter is −5.2 on the log scale, while a typical pollen grain is a −4.5. Which is smaller?