Interactive Timeline
The Cosmic Calendar
The universe is about 13.8 billion years old. Squeeze all of that history into a single calendar year, with the Big Bang at the first tick of January 1st and this exact moment at the last tick of December 31st, and everything humans have ever done fits into the final few seconds. This is Carl Sagan's "Cosmic Calendar," rebuilt here so you can scrub through it yourself instead of just reading about it.
13.8 billion years, one year long
Drag the slider to move through cosmic history, or jump to one of the zoomed-in views below, since almost nothing happens until the very end of December.
Video: The Royal Society, CC BY 3.0, via Wikimedia Commons.
Cosmic date
Real time
Every catalogued event in this view
Everything in this section is theoretical. These are real ideas discussed in published physics and cosmology research, not settled facts or forecasts. Some are strongly favored by current data, others are genuinely speculative and actively debated among cosmologists. Each scenario below is labeled with how solid its footing actually is, and links to where it comes from, so you can go read the real source yourself.
Why the calendar has to change shape here
Curious about the physics behind any of this? Ask an expert.