T. rex and the crater of doom

What a satisfying, scientific tale. [a:Walter Alvarez|48103|Walter Alvarez|https://s.gr-assets.com/assets/nophoto/user/u_50x66-632230dc9882b4352d753eedf9396530.png] of the eponymous "Alvarez Hypothesis," the hypothesis that a large impact caused the mass dinosaur extinction could have written many different types of books about his work. This is a deeply humble book that seems to be equally about How To Do Good Science as it is about the deeply fascinating scientific work that Alvarez has done.

The story is just so freaking cool -- both the human and geologic aspects. How could we possible understand what happened to the planet 65 million years ago? Alvarez, as a postdoc, sets out to Italy looking for evidence of plate tectonics by measuring magnetic drift, as anticipated if a plate shifted rotationally. Instead, he finds that the magnetic data from his region is too poor to pick up such subtle changes and he can only detect magnetic reversals. Then he realizes that the particular region he picked happens to have other clues in the rock bed (forams) that can be used to date magnetic reversal events, which has never been done before. However, forams were living organisms, and in the process of using them for dating, they noticed an abrupt boundary of absence of large forams, consistent with a mass extinction. Each step along the way is so nicely laid out -- not the way the lay public views science: hypothesis, easy test, confirm results, new hypothesis, the end!. But the real way: totally different hypothesis, interesting observation, new hypothesis, accidental discovery, new hypothesis, need to invent a brand new assay, and endless repeats. To do their work they ended up inventing new ways of performing neutron activation analysis, blowing up the conventional geologic belief in uniformism, rather than catastrophic events and discovering potentially periodic impacts on the earth (the downside to an old book -- the 1997 view of the Nemesis star has largely been discredited, but the discrediting was nearly a decade of work for the astronomy community and has led to new interesting hypotheses about the solar system)

Alvarez is deeply humble about his role in all of this, instead highlighting the many multidisciplinary collaborations he was engaged in with his work. That's another great facet to the book, to hear about all of the geologists, astronomers, paleontologists, archeologists and oceanologists involved. He also discusses the false roads they go down (they only discovered extraterrestrial material in the first place because they had a hypothesis that a nearby supernova was responsible for the mass extinction, a theory they nearly published due to bad data) and circles back when the evidence that pointed them one way later gets solved by something else -- like the shocked quartz that suggested an oceanic impact, which were later explained by secondary impact from debris. Finally, in what turns out to be a prescient move, instead of criticizing his main rival, who believed in a volcanic theory of extinction, Alvarez confirms that there is evidence to support the involvement of volcanic activity at the Declan traps in the extinction event, which would not become part of the mainstream wisdom until 18 years after the book was published.

There are only two major downsides to this book: one is the first 33 pages of front matter about the story as we know it and how science works is relatively dry -- Alvarez should have jumped in with his personal story and then circled back. The second is that 19 years have passed since publication and new discoveries have been made -- read with google handy!