U.S. investors got a serious jolt today when the Dow Jones industrial average tumbled 1,000 points minutes after the market opened in a wave of selling that circled the globe after a historic plunge in Chinese stocks.Though the declines eased significantly as the morning went on, the market plunge sent a shiver of fear through Americans with retirement accounts or saving to buy a home that the bull market is over.The Dow was down 282 points, or 1.7 percent, to 16,176 points as of 12:54 p.m. Central time. The S&P 500 …