People are talking buying force and selling force. 买卖心里为内力。看涨才买，越买越涨，涨到一定程度就会觉得贵了，多数人开卖，股价就会迭，越迭越卖。跌倒一定程度，有人就会觉得便宜了，开买，股价就会停迭，即而反弹。大家观望时就会出现Side way. 　看chart多了就会领悟股价波动的脉络。News release, geopolitical events, etc. 为外力。　外力的作用有两方面的。227的impact就是外力。That evening I checked the largest decliners, really scarry. Quite some stocks declined 20 - 60%!!! Luckily enough, on my account all of the stocks behaved just like a normal day. Look at today's index chart, it was so right that I sold all of the stocks on 228 only at about 1% down from 266. So, it is fun to play with the internal force. Every day's price is mostly influenced by the previous day's price (or previous several days') if there is no external force on action. To me the real risk is over night news or the day like 227.

In my work I have to deal with various scientific and engineering variables. They look very much like stock charts. For instance, it is a natural feature to have higher highs and higher lows for a fluctuating and upwarding variable. Please pull out a one year temperature chart from the internet. If you label it as ??.com's stock chart, those analysts would think so. In our research campus we have some high concret buildings. When it rains and the building walls are partly wetted, the wetted pattern is just like a stock chart.