Timeline of the Universe

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).

Table of contents

1 The distant past
2 The human era
3 The far future
4 Problems with estimating the age of the universe

The distant past

13.7 ± 0.2 billion years ago: Universe, which includes time and space, 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: appearance of the genus Homo (see evolution of Homo sapiens)
about 150,000 years ago: appearance of Homo sapiens
for the past and present of mankind, see centuries
- 12 to 10 thousand years ago (the Holocene epoch): Homo sapiens invents agriculture; start of human civilization
- 1961: men first orbit the Earth in spacecraft
- January 15, 2001: Wikipedia project started

The far future

3 billion years from now: Milky Way and Andromeda collide
5 billion years from now: the Sun becomes a red giant

See also 10¹⁷ seconds for times further than 3 billion years into the future.

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 noticeable on a very large time scale or very large astronomical scale.