Unless you're a short-term trader, what happens to the stock market in a single day rarely makes a big difference. But on a day like today, when the Dow Jones Industrials (INDEX: ^DJI) traded with extreme swings in both directions, paying attention can make a big difference. After rising nearly 95 points early in the session, the Dow gave up all its gains by mid-morning, and after treading water for much of the next few hours, it fell to as much as a 130-point loss before recovering somewhat to finish down 83 points.

With earnings season having started, part of the drop is likely due to nervousness about how the second quarter shaped up for Corporate America. Just in the past day, semiconductor stocks AMD (NYSE: AMD) and Applied Materials (Nasdaq: AMAT) both came out with warnings about revenue and net profit, with AMD pointing to falling demand for PCs and Applied Materials reporting weak foundry demand. Even worse, Cummins (NYSE: CMI), which has benefited from its foray with Westport Innovations (Nasdaq: WPRT) into the natural-gas engine market, plunged after saying it expects only flat sales this year rather than its previously projected 10% growth.

But other factors are also at play here. The U.S. dollar soared to a two-year high against the euro. A court in Germany charged with determining whether the country can participate in Europe's bailout fund said that it could take up to three months to issue a ruling, raising doubt about the Continent's ability to respond to the ongoing crisis there.

Commodities weren't beneficiaries of the dour mood, either. Both oil and gold suffered substantial losses, with oil down $2 to around $84 per barrel, while gold fell $22 to $1,567 per ounce, weighing on stocks in those respective sectors. Only bonds managed to eke out gains, with the yield on the 10-year Treasury falling back down to 1.5%.

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