### The Doomsday Calculation

How an Equation that Predicts the Future Is Transforming Everything We Know About Life and the Universe

An impulse checkout from the Portsmouth Public Library. And it turned out to be a lot of fun, William Poundstone's latest exploration into the deep dark woods of fringe science, contemplating some of the ultimate questions of physics and probability.

It begins with a description of the "Copernican method" invented and popularized by J. Richard Gott III, a respected physicist; its purpose is to estimate the lifetime of something, when the only thing you know about something is how long it has been around so far. Called "Copernican" because it assumes that there's nothing particularly "special" about your observation in either time or space. But especially, here, time.

The argument is: you're unlikely to be observing this something either at the beginning or the very end of its lifetime. The most likely scenario is: you've come across it sometime in its middle age. And that gives you a shot at predicting how long it's going to last.

Gott came up with this in 1969, viewing the Berlin Wall, it being 8 years old at the time. He predicted with 50% confidence that it would not be there in 1993.

And (ahem) it was not.

Poundstone explores Gott's Copernican method, where it applies and where it doesn't. And then goes on to visit related and unrelated weirder areas of scientific/mathematical speculation. For example, Zipf's Law, which states that the Nth most-common word in English text has a frequency proportional to 1/N. So, for example, the 50th most common word will occur about twice as frequently as the 100th most common word.

And the math behind this is similar to the math behind the Copernican method. Hm.

Poundstone covers a lot of area. The Fermi Paradox ("Where are all the space aliens?"); Are we living in a simulation created by others? Why are there three macroscopic spatial dimensions? That fine-structure constant, a dimensionless value approximately 1/137: a little bigger, or smaller, and atoms would not be able to exist. The possible menace of Artificial Intelligence (Poundstone is less sanguine about such menace than Steven Pinker). The implication of the many-worlds interpretation of quantum theory. The possibility that our universe is simply a "bubble", one of many created out of a high-energy vacuum.

And more. I suggest you read this book in relatively small doses; there's so much mind-blowing theorizing herein, you might walk around in a daze for days.