This quote introduced a paper I am just reading -- thought of your curriculum right now . . .
Certain measurements are crucial to our ordinary understanding of the universe.
What, for example, is the mean diameter of the Earth? It is 12,742 kilometers.
How many stars are there in the Milky Way? Approximately 1011. How many
genes are there in a small virus particle? There are 10 (in φX174 phage). What
is the mass of an electron? It is 9.1 x 10-28 grams. And how many species of
organisms are there on Earth? We do not know, not even to the nearest order of
magnitude.— E. O. Wilson, 1985, p. 21.