The key ideas

A Short History of Nearly Everything

Bill Bryson, 2003

The journalist Bill Bryson felt embarrassed that he knew almost nothing about the planet he lived on. He set out to learn how people ever worked out the mass of the Earth, its age and the beginning of the universe. The answer turned out to be a story of eccentrics, stubborn minds and forgotten scientists. And it led to one conclusion: we are very lucky to be here at all.

Who it is for

For anyone who once looked at a diagram in a school textbook and thought: "How do they actually know that?" And for anyone who likes their science told through the lives of real people.

Welcome. And congratulations. I am delighted that you could make it. Getting here wasn't easy, I know. In fact, I suspect it was a little tougher than you realize.

What this book is about

As a schoolboy, Bill Bryson was leafing through a heavy, dull textbook from the 1950s when he came across a picture: the Earth cut open, as if someone had sliced out a quarter of it with a big knife. Crust, mantle, a glowing hot core. But something else caught him: how do they know this? Nobody has ever been down there. The textbook said nothing about it.

Bryson is not a scientist. He is a journalist and the author of funny travel books. As an adult he realized he knew almost nothing about his own planet, and he spent several years questioning scientists. This book came out in 2003.

Its main question is not "what do we know" but "how did we find out". And Bryson's answer nearly always has a human name: an eccentric, a stubborn mind, a forgotten researcher who spent years measuring what seemed impossible to measure. Ahead of you: a recluse who weighed the Earth, a chemist who went looking for the planet's age and found poison in the air, and two radio astronomers who had to evict pigeons from their antenna.

The book is more than twenty years old. Where science has moved on, you will find a note.

Idea 1. How to weigh a planet

Can you weigh the Earth? There are no scales that big. But there is Newton's law of gravitation: any two bodies pull on each other. If you measure precisely how strongly two balls of known mass attract each other, you can calculate the mass of the Earth.

The device for this experiment was designed by an English clergyman and scientist, John Michell, but he died before he could use it. The crates of parts went to Henry Cavendish, a brilliant scientist and one of the shyest people of his age: he went to painful lengths to avoid company, especially the company of women. As Bryson puts it, the assembled device looked like an eighteenth century version of a weight training machine.

In the summer of 1797, Cavendish, then sixty-seven, settled into the next room so that nothing would disturb the experiment, and for almost a year he watched the balls through a telescope aimed through a hole in the wall. The result: the Earth weighs about six billion trillion tons.

This was not a guess but a measurement: today's figure for the mass of the Earth is very close to the number Cavendish arrived at.

The device was so sensitive that Cavendish watched it through a telescope from the next room: the warmth of a human body would have nudged the pointer and ruined the reading.

Sometimes the unmeasurable is measured by a roundabout route: instead of giant scales, you need a few balls and enormous patience. In Bryson's telling, a discovery often looks less like a flash of insight and more like a year of very precise, very tedious work.

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About the author

Bill Bryson is an American writer who lived in Britain for many years. Before this book he was known for his funny travel books. A Short History of Nearly Everything won him the Aventis Prize for science books.

All books by this author: Bill Bryson

Terms from the book

  • Wilson
  • Princeton
  • Newton
  • plate tectonics
  • Bell Labs
  • Dodo
  • Mauritius
  • Polio
  • Mantle
  • Midgley
  • Patterson
  • Big Bang
  • Penzias
  • Cosmic microwave background
  • Michell: John Michell, an eighteenth century English clergyman and scientist. He designed a device to measure the pull between metal balls and so weigh the Earth, but died before he could run the experiment.
  • Cavendish: Henry Cavendish, an eighteenth century English physicist and chemist and a famous recluse. Using Michell's device, he ran the experiment that gave the first calculation of the Earth's mass.
  • Uranium: A radioactive metal. Its atoms decay very slowly and at a steady rate, and at the end of the chain they become lead.
  • Isotope: One of several forms of the same element whose atoms differ in mass. Lead, for example, has several isotopes.
  • Radiometric dating: A way to find the age of a sample from how many of its radioactive atoms have already decayed. This is how Patterson measured the age of the Earth.
  • Canyon Diablo: A meteorite that fell in Arizona about 50,000 years ago and left a huge crater. Patterson used its fragments to find out the age of the Earth.
  • Tetraethyl lead: A lead compound added to gasoline from the 1920s on to make engines run smoothly. In time it was banned because of the harm it does to health.
  • Chlorofluorocarbons: Gases, also known as CFCs or freons, once widely used in refrigerators and aerosol cans. They turned out to destroy the ozone layer, and an international agreement banned their production.
  • Ozone layer: A layer of ozone gas high in the atmosphere. It blocks most of the Sun's dangerous ultraviolet radiation.
  • Leaded gasoline: Gasoline with tetraethyl lead added. When it burned in an engine, the lead went into the air.
  • Horn antenna: An antenna shaped like a huge flaring horn. One was built in New Jersey for communicating via satellites.
  • Dicke: Robert Dicke, an American physicist at Princeton. His team was getting ready to search for the radiation left over from the Big Bang, but Penzias and Wilson found it first.
  • Wegener: Alfred Wegener, a German meteorologist and polar explorer. He proposed that the continents move, but convinced almost no one in his lifetime.
  • Fossils: The remains or traces of ancient plants and animals preserved in rock.
  • Continental drift: Alfred Wegener's hypothesis that the continents slowly move. Plate tectonics later developed and explained it.

All terms

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