Robert Krulwich

Check out this graph of America's "Growing Season" — it measures the number of continuous days and nights when it never gets below 32 degrees. You could call this our "frost-free" time of year. In many places, the frost-free season begins in the spring and ends somewhere in October.

As you can see, over the 20th century, it's been staying frost-free longer...and longer...and longer...

This is one of those fun-to-think-about questions. A brain isn't much to look at, after all. It's about the size of your two fists put together, three pounds to hold, but oh my, what it can do.

With our brains, we can think backwards, imagine forwards, conjure, create things that don't exist, leap vast distances. For example, suppose I say to you, close your eyes and imagine this:

It's hot today. Really, really, hot; over a 100 degrees Fahrenheit hot, and so I'm sweating.

Sweating is what we people do to cool off, which is good. But sweating is also what makes me ... what's the word? Odoriferous. (Latinate for stinky, which is not so good.)

Think of a giraffe lying on the Serengeti plain. He has just died, maybe of disease, maybe he was killed by a pride of lions, but now he's a 19-foot-long, 4,000-pound mound of meat, which very soon is going to stink and rot and muck up the neighborhood.

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