[theptip]

> The atoms [in water] are 1 or 2×10−8 cm in radius. Now 10−8 cm is called an angstrom (just as another name), so we say they are 1 or 2 angstroms (Å) in radius. Another way to remember their size is this: if an apple is magnified to the size of the earth, then the atoms in the apple are approximately the size of the original apple.

This is one of my favourite Feynman analogies, right at the beginning of these lectures. He had such a remarkable ability to transpose concepts into more understandable forms.

[dekhn]

my chemistry teacher kept saying "a mole is just like a dozen of something. Except it's 6.023*10**23".