by Rob Kingston
Sixty-six million years ago, a city-sized object from outer space slammed into what is now Mexico, with devastating results. Bad news for the dinosaurs, which perished along with 75% of life on Earth, but good news for us. The mass extinction caused by the Chicxulub impact ultimately paved the way for you to be reading this, rather than a highly evolved tyrannosaurus.
This much we already know, but in this intriguing book the Harvard physicist Lisa Randall puts forward the theory that the dinosaurs’ nemesis was a comet nudged from its orbit by dark matter. It’s now well established that this elusive stuff makes up 85% of the universe, yet we can’t see it or feel it. However, it does exert a gravitational pull and this is what Randall blames for the disaster.
The frequency of giant impacts on Earth appears to match the “wobble” of the solar system as it orbits the Milky Way. Randall proposes that every time we cross a think disc of dark matter, we run the risk of comets being flung our way. (Fortunately, we seem to have been spared on the last pass, so should be in the clear for another 30m years.) While she admits her theory is speculative, Randall also provides clear explanations of the more solid truths of the universe and the extinction of the dinosaurs. All this is admirable, but also leads to my only criticism: that in covering so much disparate ground, the book feels rather disjointed