18 - Very Small Legos

Summary

The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom. It is not an attempt to violate any laws; it is something, in principle, that can be done; but in practice, it has not been done because we are too big.

Richard Feynman, “There's Plenty of Room at the Bottom,” a talk delivered in 1959

We all know that atoms are small. Avogadro's number describes just how small they are. Written out in full it is about 602,400,000,000,000,000,000,000. That is the ratio between grams, the units we use to measure the mass of small objects – a dime weighs slightly over two grams – and the units in which we measure the mass of atoms. An atom of hydrogen has an atomic weight of about one, so Avogadro's number is the number of atoms in a gram of hydrogen.

Looking at all those zeros, you can see that even very small objects have a lot of atoms in them. A human hair, for example, contains more than a million billion. The microscopic transistors in a computer chip are small compared to us but large compared to an atom. Everything humans construct, with the exception of some very recent experiments, is built out of enormous conglomerations of atoms.

We ourselves, on the other hand, like all living things, are engineered at the atomic scale.