It is expressed by the evolution of an angle: the sidereal time. The motion of the Earth around its axis of rotation is obviously the most important that will define the notion of day. The motion of the axis of rotation of the Earth relative to the Earth itself (polar motion): it is very small since the pole remains in a circle of about twenty meters, but this motion is unpredictable The motion of the axis of the Earth referred to the "outside" (that is to say with respect to an inertial reference frame): it is this motion that defines the motion of the celestial equator and the modification of the coordinates ( precession ![]() To fully define the motion of the Earth, we need to know: The rotation of the Earth around its axis defines the day and the revolution of the Earth around the Sun defines the year. Their policies may differ from this site.Understanding > Fundamental concepts > Time I ROTATION AND REVOLUTION OF THE EARTH : TIME SCALES Some links on this page may take you to non-federal websites. Some full text articles may not yet be available without a charge during the embargo (administrative interval). When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH This project fulfills an ongoing global community initiative to develop a continuous, astronomical-calibrated, International Geologic Time Scale for the past quarter billion years of Earth history. All data and tools will be documented and accessible through multiple NSF public database systems, including GEON, CHRONOS, PaleoStrat, PBDB, and others. Numerical ages from the reconstructed ATS will be inter-calibrated with other dating techniques in conjunction with NSF's EARTHTIME Project. To aid in the science, a universally accessible signal processing toolbox will be created to modernize and unite leading statistical time series techniques used in cyclostratigraphic research, as well as in many other geoscience fields. Emphasis will be placed on the goodness of fit of stratigraphic signals to astronomical models, duplication of records from different regions, and high-resolution calibration to geomagnetic polarity signatures and integrated bio- and chemostratigraphy. The methods that underpin the Cenozoic ATS will be applied to the Mesozoic. The grand "team" goal is to extend the ATS, now virtually complete for the Cenozoic Era (0 to 65 million years ago), to encompass the past 250 million years. Project activities will be coordinated with more than a dozen international partners and will utilize the expertise of the Cretaceous, Jurassic, and Triassic subcommissions of the International Commission on Stratigraphy. The results should improve estimates of rates and timings of a wide range of Earth system processes by at least an order of magnitude. ![]() This collaborative project will assemble a continuous Astronomical Time Scale (ATS) for the Mesozoic Era (65 to 251 million years ago) from orbitally forced paleoclimate cycles recorded in stratigraphic data. Primary Place of Performance Congressional District:Ġ1000809DB NSF RESEARCH & RELATED ACTIVIT 01000910DB NSF RESEARCH & RELATED ACTIVIT ![]() Linda Hinnov (Principal Investigator) Sponsored Research Office:.Collaborative Research: An Astronomical-Calibrated Time Scale for the Mesozoic Era NSF Org:
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