The Earth is estimated to be between 4.51 to 4.55 billion years old (Dalrymple, 2001). This chart by the International Commission on Stratigraphy shows the units of time in which the geological time scale of our planet is divided and will be useful once we start dealing with past events.
Cohen, K.M., Finney, S.C., Gibbard, P.L. & Fan, J.-X. (2013; updated) The ICS International Chronostratigraphic Chart. Episodes 36: 199-204. |
However, to get a better understanding of the massive timescale we are talking about, this "Cosmic Calendar" is quite useful. On it, the Big Bang happened on the first second of January 1st. Considering the universe is around 13.8 billion years old, each month is about 1 billion years on this calendar. Our planet was formed in August (this would be beginning of the Precambrian eon on the stratigraphic chart). Dinosaurs roamed the Earth from about December 24 to 29, and it is only in the last few minutes of the year that we, humans, appear. This already tells us that a lot has happened on our planet before we appeared.
From: www.nobelprize.org (adapted from 'Cosmic Calendar' by Carl Sagan) |