Paul Solman:

To swipe from "60 Minutes," the debt ceiling clock is ticking. But what would happen if the U.S. actually defaulted on its debt, the $31.4 trillion of Treasury IOUs out there?

That hasn't happened since the Treasury was established in 1789. Now, the debt ceiling is the cap on the total amount of money the federal government is authorized by Congress to borrow. Created in 1917, it made up about 10 percent of us GDP, compared to this year is projected 100-plus percent. So, at long last, a default?

Simon Johnson, MIT Sloan School of Management: That is a very big deal. That sends more than ripples. That sends shockwaves around the world throughout financial markets and massively disrupts U.S. government operations.

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