A Short History of Nearly Everything: Chapter 9 Summary & Analysis

Everything is made of atoms—tables, walls, the air between us, and even human beings ourselves. Atoms combine to make molecules (he way letters combine to make words. When we die, our atoms disassemble and go off to make other molecules. Every atom in a person’s body was once part of a star and of many other creatures. Bryson notes that up to a billion of every individual’s atoms came from Shakespeare, another billion from Beethoven, and another billion from Genghis Khan. Atoms are so small that the number of atoms per millimeter is like the number of sheets of paper in a stack as tall as the Empire State Building. 

The modern conception of atoms as tiny, numerous, and indestructible is formulated in 1808 by a British schoolteacher named John Dalton, who speculates that elementary particles can’t be destroyed. Einstein touches on this issue in a 1905 paper but abandons it to pursue relativity theory. Instead, it’s taken up by Rutherford (the same farm-boy-turned-scientist who discovers radioactive half-life and dates Earth’s age to over 700 million years). At the time, scientists assume atoms are solid positively-charged objects studded with smaller negatively-charged components (like raisin buns). However, Rutherford shoots ionized particles at a sheet of gold foil, and he’s shocked when some sail through (meaning there is empty space in gold atoms) while others bounce back (meaning the atoms have small and dense centers).

Bryson explains that every atom contains a dense nucleus packed with protons (positive charge) and neutrons (no charge), that electrons (negative charge) circle around. Bryson illustrate this idea with the idea of a cathedral with a fly inside: if the fly represents the nucleus, the electrons are as far away as the cathedral’s walls (but since protons are heavier, the fly would be heavier than the cathedral). An atom, therefore, is mostly empty space. The ability of atoms to stay intact seems puzzling: electrons should be falling into nuclei, but they don’t; nuclei should blow up, but they don’t. The discovery of neutrons in 1932 explains why, since neutrons stabilize the atom’s nucleus.

In 1913, Rutherford’s Danish colleague Niels Bohr realizes that electrons appear and disappear—they can jump between different orbits around the nucleus without occupying the space between, a phenomenon he dubs “quantum leap.” Scientists also puzzle over why electrons sometimes act like particles and sometimes act like waves. In 1926, Werner Heisenberg proposes—with his famous “uncertainty principle”— that we can know where an electron is or the path it will take as it moves, but not both. In simpler terms, Heisenberg shows that we can’t predict where an electron will show up around an atom’s nucleus. This means that, bizarrely, an atom’s nucleus is like a dense cloud of protons and neutrons, surrounded by a field in which the electron will most probably occur.

Even more strangely, scientists realize that atomic particles have twins, and they act in unison regardless of the distance between them. In order to understand this concept, Bryson asks the reader to imagine a pair of balls: if Bryson spins one clockwise in Ohio, its twin in Fiji will simultaneously spin anticlockwise at the same speed. Further, it seems that physicists need one set of laws for motion in the external world (centering on gravity), and another set of laws for motion in the subatomic world (for which strong and weak nuclear forces are posited). Einstein, in particular, is bothered by how messy this solution is. It doesn’t sit well with him to think that God didn’t tie the picture together, and Einstein “wastes” half his life trying unsuccessfully to tidy it up.