Does no-one else feel a tiny bit squeamish about NASA firing a 23,000mph missile the size of a washing machine at a comet 83 million miles away?

They say there’s no harm done – that it’s a bit like a fly hitting a car windscreen, since the comet is about half the size of Manhattan. But still, the whole point of the exercise is that the scientists know next to nothing about comets. They didn’t even know whether the surface of the comet would be hard, or soft just like a big cheese. So can they be certain that their actions might not trigger some kind of devastating chain reaction?

Might a shallow atmosphere around the comet be somehow disturbed by the pyrotechnics as the washing machine struck? Might the little green men who quite possibly live inside the big cheese be cowering under their little green beds or behind their little green sofas? And what about the theory that a butterfly flaps its wings in Chicago and a few days later there is a tornado in Milton Keynes? Surely NASA has heard of the butterfly effect?

OK, so it’s pretty unlikely that firing a washing machine at a chunk of rock half the size of Manhattan would do that much damage. It seems the surface of the comet was hard after all, and after a few plumes of debris the comet’s carrying on its own little journey to who-knows-where. Perhaps it’s a good job the missile did explode on landing, and not just sink into a big cheese. Because otherwise, there might just have been a gaggle of little green men standing around wondering how to put their little green shirts in the washing machine on a short-spin woollens cycle.