Is a Disc of Dark Matter Behind Earth’s Mass Extinctions?

January 8, 2016 | Joanne Kennell

Composite image showing distribution of dark matter through a galaxy
Photo credit: NASA

It may be purely coincidence, but the evidence is shocking.

In a book titled Dark Matter and the Dinosaurs, Harvard theoretical physicist Lisa Randall describes her theory on how humans came to exist.  She hypothesizes that the extinction of the dinosaurs — necessary for the emergence of humans — is linked to dark matter. 

Around 65 million years ago, a large asteroid or comet impacted Earth — wiping out 75 percent of all species on the planet — including most of the dinosaurs.  Thanks to this event, humans were able to evolve.  But was this collision purely by chance?  

Randall does not think so.

In her book, she describes a dark, pancake-like disc of densely packed dark matter within our galaxy, and this disc is responsible for our evolution.  

SEE ALSO: For the First Time, Scientists May Detect Dark Matter in Nearby Galaxy

Dark matter is an invisible substance that makes up 27 percent of all matter and energy in the universe while normal matter — everything that has ever been observed by humans — makes up only five percent.  The rest is made up of dark energy.

Scientists know dark matter exists because they are able to measure its gravitational pull on other objects in the universe, although it has never been directly detected. Because dark matter has this strong, gravitational influence on objects, including those in our solar system, it is not unreasonable to imagine that this force could affect the path of comets and asteroids.

The key to Randall’s theory is that our solar system is not always near the disk, because just as Earth revolves around the sun, the solar system orbits the center of the Milky Way.  Now you may be wondering how often we pass near this disk.  This is where it gets interesting.

A team of astronomers estimated that our solar system completes an oscillation around the Milky Way about every 32 million years.  A logical assumption is that we would pass this disc at the same rate.  What is fascinating about that number is that mass extinctions on Earth have occurred about once every 25 to 35 million years.

SEE ALSO: Are We Witnessing the Sixth Mass Extinction?

According to Randall, when our solar system passes near this disc, the gravity of dark matter influences material in the Oort cloud — the outer regions of our solar system.  It is located about two light-years from the sun and contains billions of frozen objects at least 12 miles (19 kilometers) wide.  Let’s just say if something that big were to hit Earth today… we would not be around to find out what happened next.  And this is exactly what Randall believes happened to the dinosaurs.

How can this ever be proven?  So far Randall has looked at the speed and direction of stars in our galaxy to see if they move in unexplained ways — suggesting the presence of a dark disc.  However, considering there are over 100 billion stars in the Milky Way, this will not be an easy task.

In her concluding remarks, Randall writes:

“In some global sense, we are all descendants of Chicxulub [the town where the dinosaur-killing meteor impacted]. It’s a part of our history that we should want to understand. If true, the additional wrinkle presented in this book would mean that not only was dark matter responsible for irrevocably changing our world, but also that some of it played a crucial role in allowing our existence.”

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