If you’ve ever stopped to peer with suspicion at the sky, wondering how that would go, a mammoth piece of space rock on its way in to bring ruin, the last two years have not been especially restful. In February 2013, a large asteroid ripped over the Chelyabinsk district of Russia, trailing cartoonish lines of smoke as it made its shallow entry, radiating so much light and heat that onlookers were left with reddened faces. Skin peel. When the asteroid exploded, 15 miles up, there was a terrible, prolonged bang – a noise that has rung on, in its way, ever since.

We now know that the explosion over Chelyabinsk occurred with a force equal to 500 kilotons of TNT, or a couple of dozen Nagasaki bombs. Had it come down a little steeper that February, directing the might of its detonation at rather than over Chelyabinsk, the asteroid would have killed thousands on the ground. A little later, it might have done for many more in Moscow, or Riga, or Gothenburg. Though nobody died at Chelyabinsk, it was an event of such calamitous potential that the asteroid was classified by certain astronomers a “city-killer”. Those astronomers have wondered, since, if we’re not being a little complacent.

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