What Time Is It?
THE AGE OF THE EARTH has intrigued people for a long time. Aristotle thought that our planet had existed forever, while a careful reading of biblical accounts suggested to theologians that it was created in 4004 BCE. In modern times, radiometric dating makes it possible to determine the age of rocks and fossils, so we now know with confidence that Earth is 4.54 billion years old. Since a timespan so vast is difficult to contemplate, I find it useful to shrink it down to a single year, which starts with Earth’s formation on January 1. We can then look back on the events in this Earth Year from the vantage
