This news story talks about new theories behind the mass extinctions that have occurred in Earth’s past. Very interesting reading.
The mass extinction that most people are familiar with is the Cretaceous-Tertiary extinction, which is when the dinosaurs were wiped out. But there have been others, some of them much worse.
The new theories propose the idea that these extinctions could have been caused by vast clouds of interstellar matter. These clouds might have blocked some of the sunlight reaching the Earth, causing an ice age. Or they could have stripped some of the ozone from the upper atmosphere, increasing the amount of ultraviolet radiation that would reach the surface.
Deus ex machina.
I am not a scientist, but I found When Life Nearly Died: The Greatest Mass Extinction of All Time to be a fascinating read that is very accessible to the lay reader with lots of background information on the historical development of geology, with an Anglosphere angle, as it relates to mass extinctions. There is the obligatory conclusion about the next great extinction that you-know-who is responsible for, but you don’t have to read that chapter.
Hmmm, I remember this interstellar-cloud thing as a popular science fiction theme in the Fifties…
We know that in the distant past there were actual catastrophes that wiped the earth nearly clean of life. We have several interesting candidates for those extinction events, none proven completely.
Contrast those bona fide catastrophes with the pathetic pseudo-catastrophe of human-caused climate change, and you begin to understand how far climatology has to go before it deserves to be a respected science.
Our sun, along with the rest of the solar system, orbits the center of the galaxy once every 220 million years. So its possible that the Earth passed through such an interstellar cloud. It’s more likely, however, that a passing star disturbed objects in the Oort Cloud, sending them toward the inner solar system on a collision course with Earth. Oort Cloud objects are susceptible to such effects because the sun’s gravitational influence over them is very weak.