No, a Giant Comet is NOT going to Destroy us anytime soon.

I used to really enjoy the facebook page I Fucking Love Science, and to be quite honest I still follow that site. But every once in a while, and more often these days, they write headlines that betray a love of clickbait rather than science. I won’t spend time writing the reasons why IFLS is slowly turning from a legitimate science advocacy website to a clickbait site because Yvette d’Entremont, aka the SciBabe (who came about as a response to the popularity of anti-science terrorist Vani Hari) did a pretty good write up of the transformation.

Now I’m not on the full bandwagon of hating IFLS. They’re a good site but sometimes they let the desire to write a compelling headline get in the way of accurately representing the science.

Headlines are important. In college I worked on the school newspaper, and that coupled with my studies in Psychology has taught me that the title or headline is in fact the most important piece of information. You need a compelling headline to catch readers’ attention. Most people choose what they’ll read based on headline alone, and because of that bloggers, journalists and Facebook celebrities need to write compelling headlines to promote their media.

Which is fine, I’m not complaining about that. It’s just that when the article doesn’t back up the headline that I get upset. Especially when it comes from a science advocacy website.

IFLS recently posted an article under the headline Giant Comets Pose Threat To Life On Earth. Go ahead and read the article. I’ll wait.

A map of the Solar System, showing the orbits of several planets. In red are the orbits of 22 centaurs. In yellow are the orbits of 17 trans-Neptunian objects. Duncan Steel/Royal Astronomical Society

Done? Good. So since you read the article you know that giant comets don’t pose any real threat to the earth. Not today. Most likely not while you’re alive. Now the outcomes if a large comet, called a centaur, hits Earth could be devastating. From the article:

They estimate that a single centaur measuring 100 kilometers (60 miles) could contain about 100 times the mass of all the Earth-crossing asteroids detected to date. This translates to an awful lot of dust, leading the researchers to suggest that comets of this size could fill the Earth’s atmosphere with tiny particles, reducing the amount of sunlight that can pass through to roughly the level of moonlight, for up to 100,000 years. This, they say, would put an end to commercial agriculture.

That certainly is scary. But does it pose any real threat?

No, at least not with even a cursory understanding of probability.

Publishing a review of their research in Astronomy and Geophysics, the team estimates that centaurs are likely to cross the Earth’s orbit every 40,000 to 100,000 years.

The IFLS article stops there, but if you read the actual paper that was published, you’ll find that the authors state:

Chapman & Morrison (1994) considered that the arrival of a ~2km asteroid would result in the death of a large fraction of the human population, and that there is a probability of about 1% of such an event in the next 10000yr.

What that means is that, in the next 10,000 years there is a 1% likelihood of a ~2km asteroid impacting the earth. The results, of course, would be devastating. But the likelihood of that happening is so low as to be no real cause for alarm. It could happen tomorrow, but the odds are quite low. Sure, comets pose a threat to life on earth. So does climate change and the likelihood of that affecting our lives is far greater.

In short, you don’t need to spend your time worrying about comets. They don’t pose more than a 1% threat to life on earth for the next 10,000 years.