Are we that much better today than yesterday?

Great news! The Federal Reserve met and announced that they will continue to keep down the interest rate.

This might be a great decision for the country; it might be horrible. I'm not looking to analyze this right now.

I'm scratching my head over the stock market's reaction to this announcement. It seems to forget that just yesterday, the entire market tanked, because it was concerned about the Goldman Sachs fraud deal and Greece almost certainly defaulting on its loans (with several European countries heading on the same path).

So the Feds keeping the interest rate low is more than enough to erase concerns about everything yesterday?

Why is the market moving upward? Are we really that much better today than we were yesterday? (Were we really that bad yesterday?)