At http://phys.org/print303391880.html … this is about past observations of comets. For some reason the journalist that wrote the piece said, 'first observations' of comets were in the 3rd millennium BC – when he should have said written records of comets are known from as early as the 3rd millennium BC. People obviously observed comets from the year yonk – and even before that. A lot is made of the fact that comets were regarded as harbingers of disaster and bad omens but Aristotle, 384-322BC, wasn't so impressed, saying they were emanations of the atmosphere. After all, most comets are harmless as far as people on the surface of the Earth are concerned. A little bit of repeating a meme too often to create an exaggerated impression.
In medieval western Europe comets had a more robust reputation – a portent of terrible natural phenomena such as floods and earthquakes. In the 15 century a poem associates comets with 'fever, illness, pestilence and death, shortages and times of famine' – which we may note is about a hundred years after the Black Death. Mike Baillie's book, 'New Light on the Black Death: The Cosmic Connection' (Tempus: 2006) made the claim the Black Death was in part due to a cloud of cometary gas that was either poisonous or viral. All we know is that in the 15th century people did not view comets as entirely harmless – even though most of them must have been. That is no reason why historians or scientists of today should regard them as entirely superstitious, and irrational. In the 16th and 17th centuries comets were again the subject of popular concern, stirred up by political pamphlets and broadsheets. We may note this was the height of the Little Ice Age. It was also a period of witch persecution.
Modern space missions to observe comets always show craters carved out of what looked like 'space potatoes' – with surface material being ejected. In general, comets are nowadays regarded as colourful light shows as they approach the Sun. There is no fear in the general populace of danger – from pestilence, or ruined crops. Astronomers appear to be clearing the decks ready for comet ISON, and the others (this year and next).