In the coming weeks, a mathematician from the Middle Ages could vie for traders attention along with the latest data on their Bloomberg terminals and the breaking economic news on CNBC. No, traders won t be boning up on Jeopardy trivia, or ruing the academic road not taken.

Instead, traders will be eagerly watching if the Standard & Poor s 500 index hits 1120. That level will mark what s known as a Fibonacci retracement, named after an Italian mathematician who, back around the turn of the 13th century, studied how patterns tend to repeat themselves in such seemingly random things such as flower petals and the reproductive patterns of rabbits. But even though Fibonacci was dead centuries before Wall Street was even conceived, many traders believe his findings apply to financial markets. A Fibonacci retracement level is achieved when the index -- or an individual stock -- gets 38%, 50%, 62%, and a couple of other obscure percentage levels between a major peak and trough. Why traders are keen on these particular percentages is a topic math aficionados can read about here.

Suffice it to say, at 1120 the S&P 500 will be midway -- give or take a few rounded-off fractions of a point -- between its peak of 1565 in October 2007 and its low of 677 this past March (It closed on Wednesday at 1096.)

The real question, though, is why some traders get transfixed on Fibnoacci. To a large degree, it s a case of crowd psychology, says James Angel, associate professor of finance at Georgetown University s McDonough School of Business. Traders pay attention to these ratios because they know their peers are paying attention to them, too. What makes it even stranger this time around is that a 50% ratio has no significance in Fibonacci s work. But some traders care about it, anyway. Historically, the market gets its mojo when you go through a retracement of 50%, says John Lynch, chief equity strategist for Evergreen Investments.

For the past month, the S&P 500 has traded in a narrow range. Last Friday, the index had an intraday high of 1119.3 before retreating. It seems as if the market is anticipating this level as a technical resistance point, says Richard Sparks, senior equities analyst at Schaeffer s Investment Research. That is, 1120 seems to be acting as a psychological ceiling of sorts for traders. Nevertheless, many market watchers seem to be leaning toward the S&P going significantly higher if it could only get past 1120. If the market breaks through, sellers could become less likely to sell and buyers will become more aggressive, Sparks says. Then, 1120 will become the new support, or floor, for a new trading range.

Don t believe in Fibonacci retracements? If you are a market bull, you can fall back on another mysterious thing some traders believe in seasonality. December tends to be a good month for stocks, says Justin Walters, co-founder of Bespoke Investment Group.