WHY DOES THE Energizer Bunny keep going? Well, first of all, it doesn't. Everything in the universe, including you, me and the stars above, eventually goes kaput. That's entropy. But before that doleful death sentence is served, what keeps the rabbit running is the battery, which was born around 1800 when Alessandro Volta took disks of copper, zinc and cardboard soaked in salt water, stacked them in alternating layers and measured an electronic current coming off what he modestly called the Voltaic pile.
Today's batteries last longer, generate more energy and work the same way. A negatively charged anode and a positively charged cathode exchange electrons through an electrolyte. Eventually entropy steps in, electrochemical changes degrade the system and the battery dies. The car won't start; the flashlight flickers; the laptop winks off.
Commercial claims to the contrary, no one can predict how long a battery will last. When the day comes that we connect to the internet through our wristwatches and buy candy bars with our cell phones, we will still see some man on the street swearing at his pocket PC because Volta's battery -- be it lithium-ion, nickel-cadmium or kryptonite -- has just gone belly-up. It's nice to know that some things will never change.