Dark Matter and the Dinosaurs summary

So, Zwicky was the first to theorize about dark matter; but since then, a lot more research has been invested in figuring out what exactly it is. Some of the strongest data has been drawn from the cosmic microwave background, ancient radiation that originated during the formation of the universe.

By analyzing this information, scientists can figure out the amount of radiation, matter and energy that were present a mere 380,000 years after the big bang, when the universe was in its infancy. In fact, this data lines up with the research conducted by Zwicky and other scientists, in that it confirms a significant quantity of dark matter, containing five times the energy of all visible matter.

You now know how dark matter was essential to the formation of the Sun and other planets. But the solar system contains so much more. In fact, craters on Earth’s neighbors, the Moon and Mercury, show that when the solar system was still settling into place, Earth was regularly being struck by meteoroids.

What are those?

Throughout its long history, Earth has experienced intense periods of meteoroid bombardment. But unlike these past events, most space debris that enters the planet's atmosphere today doesn’t make much of an impact. In fact, millions of tiny meteoroids, adding up to 50 tons, burn up in Earth’s atmosphere on a daily basis.

So, on a clear night, away from the light pollution of a big city, it’s not hard to spot a streak racing across the sky, evidence of a meteoroid burning up. But these astrological events shouldn’t be confused with comets.

So, the role that meteoroids played in the development of life on Earth is based largely on speculation. But the destructive power of a meteoroid striking our planet is much better understood. For a perfect example of this, you need look no further than a single event in Tunguska, Russia, in 1908.

Back then, a 50-meter-wide meteoroid exploded in Earth’s atmosphere over Russia, letting loose the equivalent power of a ten to 15 megaton bomb. For reference, that’s 1,000 times stronger than the atomic bomb dropped on Hiroshima.

There have been five mass extinctions in Earth’s history, transitions with significant consequences for life on the planet.

The first two extinction events delineated the transition between the Ordovician and Silurian periods some 440 million years ago, and the end of the Devonian period, 380 million years ago.

As you can imagine, a 10 to 15-km-wide meteoroid could do some serious damage if it were it to hit Earth. Assuming the object that hit our planet 66 million years ago was traveling at a velocity of at least 20 km per second, it would have the power of 100 trillion tons of TNT – that’s more than one billion times the explosive force of the Hiroshima bomb.

Such an event would cause devastating winds, tsunamis, tidal waves and an earthquake so powerful it would be felt all over the world. But it would also result in trillions of tons of material being launched into the atmosphere. That, in turn, would result in the heat caused by the impact to become trapped in the planet, causing Earth’s surface to cook.

Figuring out where the K-Pg meteoroid landed took some serious investigation. But one clue was especially helpful: given the predicted size of the meteor, the crater it caused should have been about 200 km wide. This knowledge, along with two major leads, led scientists to the impact crater.

First, geologists who were working for the Mexican oil company Pemex found odd magnetic disturbances off the Yucatan peninsula in the Gulf of Mexico. In the 1970s, a magnetic survey was carried out, showing that the disturbances were caused by a circular region about 180 km in diameter.

While the Chicxulub crater was a major discovery, it’s by no means the only such crater that scientists have found on Earth. In fact, scientists have been gathering all the data they can on Earth’s impact craters, and the results suggest that there might be some regularity to comet strikes.

For instance, research on fossil records points to a regular extinction every 30 to 35 million years.

So, why do these potentially cataclysmic comets leave the Oort cloud?

Well, one of the best explanations has to do with how our solar system moves through the galaxy. As the solar system orbits the center of the Milky Way on a 240-million-year journey, it can experience what’s known as a galactic tide caused by the gravitational force of the Milky Way.

Okay, so you’re probably wondering just how dark matter relates to comets hitting Earth, and the facts are all about to come together. As the author suggests, in addition to galactic tides, dark matter might explain massive meteorites striking the planet.

In fact, it’s possible that more than one type of dark matter exists. After all, there are plenty of types of other known particles like quarks and neutrinos, so it’s not unreasonable that there could be multiple forms of dark matter. One such type might be self-interacting dark matter, dark matter that’s attracted to itself and which therefore clumps into a higher density.