Cosmic Calendar Human Existence. Explore the history of the universe and imagine it as taking place in a calendar year to illustrate the brevity of human existence. Each day on that calendar would last around 38 million years, and a single human lifetime would last just about 0.2 seconds, on average.

Humanity for the longest time has been considered the rulers of the world, but we’ve only been rulers for less than one minute. The astonomer carl sagan proposed a simple device to help us comprehend.