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.

The universe encompasses everything we know to exist. Time itself only has meaning within the universe. It’s impossible to imagine that the universe may have once not existed at all, and yet, that’s the current consensus among cosmologists. The Big Bang is the most widely accepted theory for how the universe began.