Cosmic Perspectives from Amid the Stars:
Astronomy Blog

According to our best estimates, the universe is 13.8 billion years old. It goes without saying that that’s extremely old. But just how long of a time is 14 billion years? The human mind has a way of underestimating massive numbers. So, to truly understand the implications of a nearly 14-billion-year-old universe, we need a scale model. Famous astronomer and science communicator Carl Sagan introduced the concept of the cosmic calendar for exactly this reason.