Preface of The Moon

The face of our serene and dependable Moon conceals two of the most important and difficult riddles in science. One is the cause of the Moon's craters, first seen by Galileo in the 1500s, a mystery that took scientists 400 years to solve. The other is the origin of the Moon herself, an enigma that has persisted all the way into this century, despite the $288 billion (in today's dollars) spent on the Apollo program.

Great questions like the origin of the Moon and how scientists work to solve them have always fascinated me. Perhaps it stems from my time as a professor at Oberlin College, where I learned that bright students were more interested in the unanswered questions than in the answered ones.

The first of the great puzzles I wrote about was the cause of dinosaur extinction. Then came the origin of the Grand Canyon, which in turn led me to the story of why the U.S. had built its two giant dams on the Colorado River, Hoover and Glen Canyon. That got me interested in the future of water in the Southwest, which took me to global warming and the effect it would have on river flow and human civilization. That led me to the denialist conspiracy and The Inquisition of Climate Science. Then came one of the largest questions of all: why did it take scientists 50 years to accept each of the four greatest theories in the earth sciences: the age of the earth, continental drift, meteorite impact cratering, and anthropogenic global warming? In the book that resulted, Four Revolutions in the Earth Sciences: From Heresy to Truth, I cover some of the same ground as in this book, but now I dig into the origin of lunar craters and of the Moon herself in the greater depth they deserve.

I have done my best to make this book understandable to the general reader. It has only one mathematical formula: the energy of an object equals its mass divided by its velocity squared. There are many illustrations. I provide endnotes for those who want to go to the sources as well as to show that the book is grounded in peer-reviewed scientific research.

I began writing during the 50th anniversary of the first Moon landing. Even today, nations continue to send unmanned spacecraft — and perhaps soon, ones with astronauts aboard — to the Moon, sometimes successfully, sometimes not. She remains as irresistible and as scientifically important as ever. But scientists have picked the lock that guards the Moon's secrets and the door is swinging open. Behind it lies an event of indescribable horror.