"If atoms are really to explain the origin of color and smell of visible material bodies, then they cannot possess properties like color and smell." So, although it is not an original thought, it is useful to bear in mind that greeness disintegrates.

Does this imply that there's no bottom level, just layer after layer of explanations with each layer being very different from the ones above? If there is a bottom level below which no further explanation is possible, can you tell whether you've reached it?

Write down your own Fermi estimation attempts here. One Fermi estimate per comment, please!