Post : “Dark Matter and the Dinosaurs
Title : “Dark Matter and the Dinosaurs
“Dark Matter and the Dinosaurs
Dark Matter and the Dinosaur
Dark matter: The world’s brightest physicists know it’s there, but can’t say for sure what it is. It is invisible, mysterious, and to most people — irrelevant to everyday life. But what if it could reach out and touch us? What if it already has, and so deeply that it just might be responsible for putting us here? One Harvard physicist is exploring that idea, and pondering the possibility that dark matter may have triggered the most famous cosmic collision ever — the one that did in the dinosaurs and opened the way for mammals to take their place.
Theoretical physicist Lisa Randall, the Frank B. Baird Jr. Professor of Science, sees intriguing lines of evidence that tie dark matter to comets in the solar system’s distant Oort cloud, and from there to the 66-million-year-old impact crater on Mexico’s Yucatán coast.
Randall first explored the idea last year in an article, co-authored with Assistant Professor of Physics Matthew Reece, in the journal Physical Review Letters. Inspired by the intricate chain linking dark matter, Earth, dinosaurs, and modern life, Randall decided to take a deep dive into the subject for her new book, “Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe.”
“I was just fascinated by this story,” Randall said. “It was really nice for me to be able to communicate about dark matter through its potential connections to what we see today.”
The book, to be published Oct. 27, takes the reader on a tour of the universe, from the Big Bang to today, from the story of life to mass extinctions, from the distant galactic disk to Earth’s K-T boundary layer — a thin, globe-spanning blanket of dust that scientists believe is evidence of the cataclysmic impact that ended the dinosaurs’ reign.
The book suggests that a thin disk of dark matter could have influenced weakly bound comets in the outer regions of the solar system as it revolved around the center of the Milky Way, and may have been the ultimate cause of the impact. Randall admits that the disk hasn’t been found, but said that current data allows for it, and that instruments that might detect it aren’t far off.
Randall makes liberal use of anecdotes and analogies to explain complex scientific ideas. We learn something about Randall, too: She skis, has a robot that vacuums her floors, and was once taken not for a cosmologist — one who studies the universe’s broad structure — but a cosmetologist.
The dinosaurs’ demise is a dramatic example of connectedness. Scientists are reasonably sure the killer made an enormous impact, though there’s some question whether it was from a rocky asteroid that would have originated within the solar system or a comet originating at its far fringe, in a vast assemblage of icy bodies called the Oort cloud, far beyond the orbit of Pluto.
If the dinosaur killer was a comet, the next question is, what gave it the initial push toward Earth? Scientists confronting that question have an additional clue: The impact that caused the dinosaurs’ extinction wasn’t the only one in the planet’s history. There have been several, in fact, and there’s some evidence that they occur at regular — at least on a galactic scale — intervals of between 30 million and 35 million years.
The Oort cloud is so far away and the time scales involved so vast that investigators have sought answers outside the solar system, which circles the galactic center every 240 million years or so, moving up and down through the flattened plane of the galaxy as it does. Some researchers have explored whether that passage could possibly bump a comet onto a collision course with Earth, but the band of visible matter in the galactic disk is diffuse enough that the collisions it would trigger don’t match the timing of those on Earth.
This is where dark matter comes in.
While dark matter is invisible, it isn’t completely undetectable. All matter exerts a gravitational pull, and it is through dark matter’s gravitational effects on visible objects in the universe that scientists know it’s there. Unlike visible matter, however, dark matter isn’t concentrated in the galactic disk. It is thought to be spread in a sphere around the galactic center that extends well above and below the concentration of stars and other ordinary matter.
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