Lisa Randall always discusses her speculative theories within the context of her science’s history. This is perfectly illustrated by Dark Matter and the Dinosaurs.

Lisa Randall is a highly respected physicist working with small teams at the cutting edge of particle physics. A Harvard professor of science she has published widely read books on cosmology, astronomy and quantum physics. Professor Randall has no fear of engaging with far-out ideas about “space, time and the universe”, including an indirect connection between “dark matter and the dinosaurs”. (Her earlier Warped Passages: Unravelling the Mysteries of the Universe explored the intriguing notion that our universe is only one of many.) However, she always discusses her speculative theories within the context of her science’s history. This is perfectly illustrated by Dark Matter and the Dinosaurs subtitled The Astounding Interconnectedness of the Universe. It is packed with information about cosmology, astronomy, and the earth’s deep history. In lucid prose Randall tours us through the universe from the misnamed Big Bang (infinitesimal and silent) to the hugely significant appearance of particles which made possible the birth of gigantic clusters of galaxies. These include the Milky Way galaxy in which our own Solar System was born. Whole chapters explore asteroids, meteoroids, comets, and the recently discovered, still mysterious Oort Cloud at the very edge of the Solar System from which comets derive. The Oort is so vast it encloses the entire Solar System in all directions. Professor Randall excites because she herself is excited, relishing that so much of what is known has only been discovered during the past century and much of it during the past 30 years. This is just as true for the Solar System in which we live. here we come to the problem of dark matter, which is dark because it neither emits nor absorbs light. Its only observable interaction with ordinary matter is gravity and here it is powerful indeed. Astronomers estimate dark matter composes 85 percent of all matter in the universe and huge masses of it had to exist early for galaxies to form, which in turn allowed stars, including our sun, to emerge. Dark matter reinforces the gravitational impact of ordinary matter in bending light, attracting galaxies together, holding them in clusters and determining the speed at which they rotate. Like others, the Milky Way galaxy travels within a cloud of invisible dark matter. It passes through our bodies daily with no observable effect. Professor Randall here suggests an interesting possibility. The unknown particles of dark matter might under gravitational pressures behave like ordinary matter and form structures and that a disk of this more structured dark matter could form within the observable disk of our galaxy. Our solar system as it travels around the galaxy may have come too close to that invisible disk and an object as big as Everest was hurled from the Oort toward the inner solar system. Sixty-six million years ago it smote the earth and wiped out 75 percent of living species including the dinosaurs. Happily for us, small burrowing mammals survived and evolution was at work. A disaster for the dinosaurs made possible 66 million years later the author of this lucid, totally engrossing book. Hurrah!

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