Reminds me of the question: "Which would you rather have, a million dollars RIGHT NOW, or a penny which I will give you double each day for a month (tomorrow 2 pennies, the day after 4 pennies, etc.) Now consider some examples of the principle in biology: * Bacteria in a culture dish will grow exponentially until the available food is exhausted. * A new virus (SARS, West Nile, smallpox) will spread exponentially. Each infected person can infect multiple new people. * Human population.
Fold an ordinary sheet of paper in half 100 times and it is a thick as the approximate radius of the known universe.