Cosmic Timeline

Every date in the game comes from a measurement or a published model, and each card names its source. The age of the universe, 13.787 billion years with an uncertainty of 20 million, comes from the Planck 2018 cosmological parameters. Earth’s story is dated by radioactive clocks in meteorites, Moon rocks and ancient minerals, and by boundaries in rock layers from the International Chronostratigraphic Chart. The early universe comes from the Particle Data Group reviews and the far future from Adams and Laughlin (1997), the same scheme of five eras used in our Deep Time explorer.

Some dates are uncertain, so the game treats them as ranges: a guess anywhere inside the range counts as exact. The Moon-forming impact is placed between 4.36 and 4.51 billion years ago, the first stars between 100 and 200 million years after the Big Bang (from simulations, since nobody has seen them yet), and the timing of inflation depends on the model. Far-future events rest on physics that has never been observed, such as proton decay and Hawking radiation, and a 2025 study by Sawala and colleagues found only about even odds that the Milky Way and Andromeda merge within 10 billion years.

Rounds 3 and 5 use a logarithmic axis in “cosmological decades”: one step is a factor of ten in time since the Big Bang, and your score is how many powers of ten you were off. Round 4 is Carl Sagan’s cosmic calendar from The Dragons of Eden (1977), with the 13.787 billion years mapped onto 365 days, so one day is about 38 million years and one second about 440 years.