What they want to do is curb panic selling and volatility .... when the exchange drops a certain percent, they shut it down...then reopen and if it starts to drop rapidly again... circuit breakers kick in again....they had always done it with individual stocks but Black Monday made them pass regs to shut down entire exchanges...In other words no one can sell anything even if they wanted to....another major concern when the markets move down fast are margin calls which can cause additional selling pressure

Creators of music have a responsibility to their craft. When they have finished using all the notes and words, they must pass them down to the next generation with a simple request. “Use these to create new music.”...Steven McDonald