ENCORE Here's to a long life - which, on average, is longer today than it was a century ago. How much farther can we extend that ultimate finish line? Scientists are in hot pursuit of the secret to longer life.
The latest in aging studies and why there's a silver lining for the silver-haired set: older people are happier. Also, what longevity means if you're a tree. Plus, why civilizations need to stick around if we're to make contact with E.T.
And, how our perception of time shifts as we age, and other tricks that clocks play on the mind.