As an experiment let's ask a different question. Did Osama time the 9/11 attact to do the maximum damage to the stock market?
Looking at the monthly S&P chart linked again here
http://futures.tradingcharts.com/chart/SW/M(Note you can click on a line to see the date and data for each month in the box above the chart)
A case can be made that he did. As I said the market was very near the spring lows in early September. Violating those lows brought the likelyhood of a steeper decline. Sure enough, that is what happend.
The post 9/11 low however only got down to the next obvious support level, the sub 1000 of Oct. 98. Damaging yes, but not the market apocalypse. Osama the market timer should have waited perhaps till we were down to those levels to strike.
In July of 02 when those Oct 98 lows were violated we had a sell off as bad as Sept 01.
I guess I don't make much of a case for Osama the market timer. A silly experiment in any case. The chart however is very instructive. Showing clearly how 'support' seems to develop at old lows. (Just as resistance, resistance to rising prices that is, often forms at previous highs)
The idea of technical analysis is to sweep away any ideas of why the market may move. Why on a fundamental basis that is. Fundamental meaning rising 'earnings' or Fed policy or the employment number or those millions of reasons always given as to why the market moves and instead just look at the patterns of price itself and how they seem to repeat.
Of course the mind ends up asking why those numbers seem to follow such patterns. Beyond the one fundamental that matters, that being the amount of excess money floating around the economy for speculation which defines the trend of the market, the patterns of support and resistance end up working because of behaviour of crowds.
Included in that are those areas of support and resistance are points where speculators, (and all stock buyers are speculators) are areas where large numbers of trades are at a profit or loss. Old highs are places were people tend to think it's a good time to take profit and old lows are areas where people tend to think it might be a good time to buy more since the price is 'low'.
One has to understand that there is an upward bias to stocks based upon the relentless increase in money that the modern credit based economy generates. In other words stocks tend to inflate. Certainly that is the trend over the last 100 years.