If everyone on Earth owned a copy of A Short History of Nearly Everything, and they stacked their copies one on top of the other, then that stack would touch the Moon1.
That's the sort of thought experiment you'll find in Bill Bryson's popular science book, A Short History of Nearly Everything, in which Bryson (BB for short) tackles all of the Big Questions that might occur to a curious resident of our planet. Questions like "What's the Universe?", "Where Did We Come From?", and "How Do Scientists Know That the Earth Weighs 6 Million Yottagrams?".
There's a lot to cover in a history of the Universe. BB's story begins with the Big Bang and ends with the plight of modern humans, but along the way, he makes forays into such varied topics as quantum mechanics, cell biology and species extinction. He manages to arrange these large subject areas into a somewhat coherent narrative, never getting too bogged down by details. And, unlike a dry textbook, each victory of science is presented as a story: the dumb theories that came first, the scientists, the breakthrough, what we still don't understand, and so on.
BB cherishes any opportunity to diverge from the main thread of the story and write about scientists. While he panders a bit to the mad genius stereotype, it makes for fun reading. Isaac Newton is the prototypical eccentric scientist. His vision experiments included poking a metal needle around his eye socket and staring at the sun. By BB's account, Newton was also surprisingly coy with his research. It took an incidental encounter with Edmund Halley, one of his peers, before he launched into writing the famous Principia Mathematica and introduced the world to gravity and calculus.
Henry Cavendish is another curious character mentioned in the book. He was the first person to accurately measure the Earth's mass, using a contraption that looked a bit like a Rube Goldberg machine. BB writes:
[...] he was particularly devoted to the weekly scientific soirées of the great naturalist Sir Joseph Banks. It was always made clear to the other guests that Cavendish was on no account to be approached or even looked at. Those who sought his views were advised to wander into his vicinity as if by accident and to talk as it were into vacancy. If their remarks were scientifically worthy they might receive a mumbled reply, but more often than not they would hear a peeved squeak (his voice appears to have been high pitched) and turn to find an actual vacancy and the sight of Cavendish fleeing for a more peaceful corner.
My favourite eccentric described in the book is J.B.S. Haldane, who conducted experiments on the dangers of deep-sea exploration. His test subjects, who ranged from himself and his wife to a former prime minister of Spain, underwent rather perilous experiments in a decompression chamber that Haldane referred to as "the pressure pot":
Sent on a simulated descent, his wife once had a fit that lasted thirteen minutes. When at last she stopped bouncing across the floor, she was helped to her feet and sent home to cook dinner.
Oxygen poisoning, collapsed lungs and burst eardrums were among the risks undertaken by his test subjects. But, on the topic of burst eardrums, Haldane hedged that...
...the drum generally heals up; and if a hole remains in it, although one is somewhat deaf, one can blow tobacco smoke out of the ear in question, which is a social accomplishment.
BB makes frequent use of analogy to convey scales that are outside the realm of human experience, like the volume of an atom. There are no figures like "6 million yottagrams" here, thank you very much. BB says that an atom lying next to a line of 1 millimeter is comparable to an A4 sheet of paper lying next to the Empire State Building. This is one of at least 4 analogies based on the Empire State Building. Then, to demonstrate that an atom is mostly empty space, he asks the reader to imagine inflating its nucleus to the size of a pea; to keep the scale consistent, you'd have to inflate the atom's shell to the size of a football stadium.
Another example, which you'll recognise if you've seen Carl Sagan's Cosmos, is the Cosmic Calendar. The idea is to imagine the entire history of the Universe as a 365-day calendar. On that calendar, modern humans exist for only the last 10 minutes of December 31st. Way more evocative than saying "humans have existed for only 0.002% of the history of the Universe".
Even science types might discover some gaps in their knowledge. As for me, I was surprised at the number of possible events that could wipe humanity from existence, including but not limited to meteor collisions, supervolcanoes and gamma rays. These catastrophic processes happen on a regular basis. The catch, however, is that they're regular on a planetary or universal timescale. BB relates a further analogy that might illustrate what I mean: lift your arms until they're horizontal to the ground and consider their span to be the entire history of the Universe. If someone now scrapes a file against one of your fingernails, it's equivalent to wiping humanity from existence. Even if civilisation-ending events happen at tiny intervals along your arm span, they're unlikely to happen during a single human lifetime. Extinction is unlikely to threaten contemporary humans, unless we manufacture it ourselves.
Science has advanced since A Short History of Everything was published in 2003, outdating some of its information. Pluto has been demoted to the rank of dwarf planet, the existence of the Higgs Boson particle has been confirmed experimentally, and what BB referred to as "junk DNA" is now believed to serve a purpose after all. The book also contains information that's just plain wrong, like the myth that church windows are thicker at the bottom due to the gradual flow of glass - they were just built like that. BB also gives credence to the popular myth that Albert Einstein was in any way an "average" student, when by Einstein's own account, he had mastered integral and differential calculus by the age of 14. There's obviously something seductive about the notion that there's a little Einstein buried deep inside all of us, if only we applied ourselves.
Most disgracefully, BB buys into the old sailor myth of divers literally being sucked up and squished into the helmet of their diving suits, a phenomenon known as The Squeeze. Of course, this is a ridiculous flight of fancy, probably fabricated by J.B.S. Haldane after a rough session in the pressure pot. I don't understand how BB could ever be taken in by such an obviously fake story2.
Anyone who fixates on these minor inaccuracies is missing the Universe for the atoms, however. I happily recommend A Short History of Everything to anyone with even a passing interest in science. It's packed with entertaining anecdotes and eye-opening analogies.
The Moon is 384,400,000-ish metres from Earth; a page is roughly 0.00012 metres thick; there are 544 pages in A Short History of Nearly Everything (including many pages of references); 384,400,000/(0.00012x544)=~6 billion copies would be required to touch the moon; and there are 7-8 billion people on Earth. The stack would overshoot by tens of thousands of kilometres, but that's the best Bill Bryson-esque analogy I could come up with. ↩
This phenomenon was proved in an episode of Mythbusters. They created a "meat man" out of dead animal parts, sent him deep underwater in an old-fashioned diving suit, and cut off his air supply. The resulting pressure differential in the suit caused his entire body to be sucked up into his helmet. Yuck. (For reference, it's season 7, episode 19, "Dumpster Diving". Here's a copy of the episode that might disappear by the time you read this). ↩
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