Why is Halley's Comet so funny?

I must admit I've nicked the idea for this post from one of may favourite TV shows, QI. If you're interested, it's in the XL edition of episode 6 ('Happiness') of series H.

By The Yerkes Observatory[see page for license], via Wikimedia Commons
Halley's Comet is a short-period comet, designated 1P/Halley, and comes close enough to Earth to be visible once every 75-76 years. It's predicted to make its next appearance in 2061, and the last was in 1986. The visit prior to that, which is the one I want to talk about, was in 1910.

The comet came into Earth's view on 20th April of that year, and made its closest (on record) approach to Earth, coming within 0.15AU (though that's still a fair bit further away than the Moon. On 18th May, the Earth actually passed through the comet's tail.

The approach is notable for being both the earliest of which photographs exist (see the photo on the right) and the first to have been analysed spectrographically. To cut a long story short, spectrographic analysis of an object allows discoveries to be made with regards to what that object is made up of.

So why is Halley's comet so funny?
The discovery of various gases in the comet's tail combined with the knowledge that the Earth was going to pass through it caused fairly widespread concern with isolated pockets of panic sparked off by highly sensationalised newspaper articles*. These stories apparently differed by area, but had a common theme running through them: one or other of the discovered gases would interact in some way with the Earth and cause large numbers of people to die, if not wiping the entire population out. Many quacks jumped on the bandwagon, selling gas masks, comet umbrellas and anti-comet pills** for protection against these alleged ills- cue yet another spate of panic-buying for disasters that won't ever happen.

One of the best dubious reasons for widespread panic was reported in the episode of QI mentioned at the beginning of this post. I can't find a lot of supporting evidence for it (everything else up until now is fairly widely documented), but I'm passing it on to you because I hope it is true:

In certain areas newspapers reported that the comets tail included a certain amount of nitrogen gas (this is true) and the story that this gas would react when it came into contact with the Earth's atmosphere, producing vast quantities of nitrous oxide that would envelope the Earth's population. Nitrous oxide is, of course, better known as laughing gas, so the story, apparently believed by many, was that the entire population of the Earth would - literally - die laughing.

Just to clear something up...
The gases in a comet's tail, whilst impressive and beautiful if observed close enough to the Sun, are too thinly spread to cause any problems by interacting with our atmosphere. If a comet were to come close enough for this to happen, we'd be in more danger from more solid bits of the comet breaking off, but even this, due to the loose structure of a comet, is unlikely to send large enough pieces our way.

* Sound familiar? Remember the 'millenium bug' back in 2000? A tiny problem inflated by media sensation and poor reporting. 2012? The same thing. It's been happening ever since newspapers were invented, so why do people still fall for it?

** Homeopathy, anyone?


  1. Yes.

    There is no other answer that can be made to that question!

    Of course, sense and reason don't often enter into such things. This may be because panicking about yet another End Of The World is such fun.


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