This is a timeline that attempts to show the best scientific estimates of the age of past events and predictions of the approximate timing of hypothetical future events with cosmological significance. Some locally significant events of interest to members of Homo sapiens are also included. See estimates of the date of Creation for alternative views based on religious tradition. (Note: in this context, billion means 1,000,000,000).
The distant past
- 13.7 ą 0.2 billion years ago: Universe begins with Big Bang
Note: the Big Bang is dated according to NASA’s Wilkinson
Microwave Anisotropy Probe (WMAP) data - for details of what is believed to have happened immediately after
the Big Bang, see timeline of the Big Bang - 300 thousand years after the Big Bang, hydrogen nuclei capture
electrons, forming the first atoms - 600 million years after the Big Bang: formation of first galaxies, see
Galaxy formation and evolution - 5 billion years ago: formation of the Sun
- 4.5 billion years ago: formation of the Earth — start of geologic
timescale - 3.5 billion years ago: first signs of single-celled life on Earth
- 600 to 500 million years ago: multicellular life evolves
The Human Era
- 2.5 to 2 million years ago: evolution of Homo sapiens
- for the past and present of mankind, see centuries
12 to 10 thousand years ago: Homo sapiens invents agriculture;
start of human civilization
1961: men first orbit the Earth in spacecraft
The Far Future
- 3 billion years from now: Milky Way and Andromeda collide
- 5 billion years from now: the Sun becomes a red giant
Problems with estimating the age of the universe
Since human observations cover a very short time interval and relatively short distance, making detailed predictions about the distant future or distant past is difficult. Humans can only observe a fraction of the total universe, and the observations cover a very short time interval. It is possible that our current understanding of physics contains errors that are only noticable on a very large time scale or very large astronomical scale.