When considering what might cause us grief in 2012, few if any researchers consider the start of the Mayan Long Count calendar to have any importance. This is surprising, because the reason for the calendar beginning on August 11 3114BC might contain clues about 2012 itself. After all, the Mayan culture did not exist 5,000 years ago, so either they randomly chose an ancient date on a whim, or an earlier civilization was behind the calendar, and they knew something important occurred on that date.
What could happen in 3114BC, and also in 2012AD? No civilization has lasted that long, so they are unlikely to be man-made events. Any natural events that occur so infrequently on Earth are virtually impossible to predict (volcanic eruptions for example). So that leaves us with astronomical events. The astrology of the pair of dates has been well studied, so we can rule out alignments of the stars and planets. That leaves the Sun, which we barely understand today, and comets. Is there a comet with a periodicy of 5000 years, due to return in 2012? Without any evidence from 3114BC it is impossible to say. Given that we are now near the end of the Mayan 5th age, could their calendar be designed to cover five orbits of a comet? And end catastrophically in 2012?
Most people have not heard of Comet Caesar (it doesn't even have a Wikipedia entry), and hopefully this will remain so. However, if we are to suffer a terrible tragedy in 2012, it is currently my leading candidate, and the purpose of this article is to explain why.
Comet Caesar was the most famous comet of its day, and one of the brightest ever witnessed. It was visible during an annual Roman festival held in 44BC, shortly after Julius Caesar's death. The following quotes are from The Greatest Comets in History: Broom Stars and Celestial Scimitars by David Seargent:
This was the comet that blazed in the skies of Rome following the assassination of Julius Caesar and which became immortalized by the Romans on the reverse of a coin bearing a portrait of Augustus struck in honor of the great Julius.
...According to Pliny, Octavian wrote that "On the very days of my games, a comet was visible over the course of seven days, in the northern region of the heavens. It rose at about the eleventh hour of the day and was bright and plainly seen from all lands".
...In the fourth century of our era, Servius presented an account that had the comet visible for 3 days and visible at midday and during the daytime.
Comet Caesar is a parabolic comet - a comet that returns less frequently than every 200 years. Most parabolic comets have orbits significantly longer than 200 years, and very few have ever been observed to make a complete orbit. Astronomers expect 50 percent of parabolic comets will receive gravitational nudges that cause them to never orbit the Sun again. Those that remain in orbit should be slowed with each passage, eventually becoming intermediate or short-period comets. Therefore we either never see them again, or they take so long to return that we don't know which, if any, have historical records they match up with.
In my search for the most likely 2012 culprit, I have constantly asked myself, could the ancients have predicted this? Asteroids and comets are definitely predictable in a broad sense, and all that it takes is observation and mathematics. Such calculations are not easy. They require recalculating the orbit for every day of every year, according to where the object is then located, and how the planets are affecting its course. If ancient astronomers had considered the period of a comet or asteroid to be fixed, rather than varying due to the gravitational influences of planets, then there may have been inaccuracies in any 2012 prediction they made. However the daily recalculations were certainly not impossible in ancient times.