Astronomical dating system
The pink zone is the actual obliquity, while the black curve is the averaged value of the obliquity over 0.5 Myr time intervals.
(Graphic courtesy of Journal Astronomy & Astrophysics)Evolution of the obliquity of the Earth in degrees, from -250 to 250 Myr.
(Graphic courtesy of Journal Astronomy & Astrophysics) A team led by Jacques Laskar from the Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE) and the Paris Observatory has released new computational results for the long-term evolution of the orbital and rotational motion of the Earth.
Following Milankovitch’s theory of the paleoclimate that describes how major climatic changes on Earth are affected by astronomical events, these results have been employed to provide a new calibration of the sedimentary records over the 0 – 23.03 Myr geological period (the so-called Neogen period).
For several decades, paleoclimatologists have used computational results obtained by the Paris Observatory’s astronomers to calibrate the geological time scale.
This need has now been fulfilled since the new computational results obtained by Jacques Laskar and his team  precisely reproduce the Earth’s past and future orbits for a period of 40 – 50 Myr.
For the first time, astronomical computations of the Earth’s past orbit have been used to calibrate a whole geological period, the so-called Neogene geological period, that began 23.03 Myr ago.
In addition to providing tools for the understanding of the Earth's major climatic changes, computations of planetary orbits make it possible to refine the geological time scale used by geologists.
A fundamental step to understanding the Earth’s past chronology is the establishment of a complete, precise time scale for geological records.