We're still here.

There must be some people in the world with access to the Internet or mass media who didn't hear the stories about how the world was possibly going to end on December 21, 2012. The usual reason for picking this date was that a calendar made by the Mayans several centuries ago ran out then.

Predictions of the end of the world are not new, there have been thousands of them over the centuries, and they fall roughly into two classes – religious prophecy and weirdness, with the latter including psychics, UFO believers and the truly insane.

It is easy to ridicule people from the past who knew less that we know now, but there have been a few real scientists who devoted at least some of their time to trying to calculate when Jesus would return. John Napier and Jakob Bernoulli both predicted times that were contemporary, Isaac Newton made the safe prediction of 2000. Another I put in the scientist category is Bishop James Ussher, often ridiculed for his estimate of 4004BC for the creation but he based this on matching Bible stories with independent folk histories and produced the best estimate from the available data. Science is always a work in progress, and it is not fair to judge people harshly for doing the best with what they had at the time.

The crazies and the psychics are the most fun, although they raise a serious question about science education that I will revisit later. Nostradamus is there, of course, predicting July 1999. Sheldan Nidle had sixteen million spaceships coming in 1996 and Nancy Lieder had the twelfth planet, Nibiru, crashing into Earth in 2003 (both dates since revised to December 21, 2012). Ronald Reagan's psychic adviser Jeane Dixon predicted February 4, 1962, later updated to "2020-2037". Assorted people worried about the Large Hadron Collider in 2010 and Comet Elenin in 2011, with the Earth being sucked into a black hole or shattered into a million pieces.

Not all the crazies were fun. Charles Manson convinced his followers to murder strangers because the end was coming, and Jim Jones predicted the end in 1967. Fortunately nobody took any notice of him then, unlike eleven years later when he was able to convince people to kill their children and then themselves.

There are dangers in failed prophecies. Believers have sold their houses and property, jeft their jobs and families and harmed themselves and others. In Uganda in 2000 almost 800 people died because the world hadn't ended, we remember Marshall Applewhite and Heaven's Gate in 1997 when a group of intelligent young people committed suicide, the Aum Shinriko cult released sarin gas into the Tokyo subway in 1995 to hasten the end of the world.

There is also the danger of time and resources being spent to assure people that the next prediction is unlikely or even impossible. NASA received a large number of enquiries from fearful people and had to waste time that would have been better spent exploring the cosmos to produce web sites and literature explaining why things just weren't going to happen.

Here are the five most common disaster predictions:

• The planet Nibiru, larger than the Earth, would crash into the Earth or pass close enough by to cause destruction.
• The Earth's rotation would change, either stopping completely, reversing spin or changing its axis.
• All the planets would be in a straight line and the resulting gravity would cause devastating tides.
• The Earth's magnetic field would reverse, with the poles swapping position.
• Time would just stop when the Mayan calendar runs out of days – the Mayan calendar was cyclic, just as ours is, and this was just as likely as there being no January 1, 2013, because 2012 wall calendars only went to December 31. This was probably the silliest fear of all.

I mentioned science education before, and that is what really concerned me about the fears of December 21. A knowledge of basic science, the stuff I was taught in primary school and the first years of high school, is enough to know that these predictions were not just unlikely but actually impossible. No huge planet can wander through the solar system unnoticed. A spinning body with the mass of the Earth can not suddenly change its axis of rotation or direction of spin. Major shifts in the magnetic field of the Earth can't happen suddenly. The gravitational effects of the Sun and Moon obliterate any tidal effects from the planets. You can laugh at these silly predictions, but the laughing should stop when you realise that the fact that some people aren't laughing is a sign that they are lacking a basic education in how to tell fantasy and fiction from fact. And there be dragons in that unknown land.

This article was published as the Naked Skeptic column in the March 2013 edition of Australasian Science