Exponential growth

Exponential growth: "Take a sheet of paper of the ordinary variety - letter size for the Americans, A4 for the rest of the world - and fold it into half. Fold it a second time, and a third time. It's about as thick as your finger nail. Continue folding if you can. At 7 folds it is as thick as a notebook. If you would have been able to fold it 10 times, it would be as thick as the width of your hand. Unfortunately, it isn't possible to do so more than about 7 times. Try it for yourself. At seventeen folds it would be taller than your average house. Three more folds and that sheet of paper is a quarter way up the Sears tower. Ten more folds and it has crossed the outer limits of the atmosphere. Another twenty and it has reached the sun from the earth. At sixty folds it has the diameter of the solar system. At 100 folds it has the radius of the universe."

Amazing...

There's a story further down the page about rice and exponential growth that my dad told me a variation of when I was younger. We calculated that placing one grain of rice on the first square of the chessboard, 2 on the second, 4 on the third, and so on, would produce enough rice by the 64th square to cover the whole of the UK in 8 inches of rice! (I forget if that was the total on the board, or just the last square. (We assumed perfect packing of the rice, too; with gaps where it didn't fit exactly, we'd be even deeper in rice.))