talkorigins.org proposed article on Milankovitch-cycle confirmation of radiometric dating
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Loren Petrich
Jul 14, 2026, 7:04:58 PM (8 days ago) Jul 14
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Radiometric dating is the main technique for geological dating, but there is a completely independent physical effect that corroborates radiometric dating: climate variations that are caused by varying amounts of sunlight, the Milankovitch astronomical cycles, in turn caused by precessions of the Earth's spin and the Earth's orbit.
-- The Cycles --
The Earth's spin is well-known for its precession. The Earth's north pole makes a circle around its orbit's north pole with an angle of around 23d and a period of around 25,700 years. But its orbit also precesses, from the gravity of the other planets, and those planets' orbits also precess in the same fashion, also from that gravity.
The Earth's orbit pole makes multiple overlapping cycles, a Spirograph pattern, 1 or 2 degrees in size, around the Solar System's angular-momentum vector. Its orbit eccentricity and perihelion direction can be multiplied to make the "eccentricity vector", and that vector also makes multiple overlapping cycles. The cycle periods are from around 50,000 years to around 100,000 - 200,000 years to 2 million years.
These precessions have three main effects that cause variations of incoming sunlight (insolation). They are approximately cyclic: the Milankovitch astronomical cycles.
1. Precession: is the Earth closest to the Sun (perihelion) in spring, summer, fall, or winter? It is farthest from the Sun (aphelion) in the opposite season. This cycle has a period of roughly 21,000 years. It combines the precessions of the Earth's spin axis and of the Earth's perihelion direction.
2. Obliquity: The Earth's axial tilt, presently 23.45d, varies between as low as 22.1d and as high as 24.5d in a cycle of roughly 41,000 years. It results from the Earth's orbit precession. The higher the tilt, the hotter the summers and the colder the winters in both the Northern and the Southern Hemispheres.
3. Eccentricity: the higher the eccentricity, the closer to the Sun at perihelion and the farther from the Sun at aphelion. Currently 0.0167, it varies from near 0 to 0.05 and greater, with periods of roughly 100,000 years and of 405,000 years. It results from multiple cycles combining. Higher eccentricity means hotter at perihelion and cooler at aphelion.
These effects make glaciers come and go. To a first approximation, when the effects combine to make hot summers, glaciers tend to melt, and when they combine to make mild summers, glaciers tend to accumulate. It is summers that are important, because it is summers that make glaciers melt.
-- What We Observe --
Over the last 2.58 million years, in the Pleistocene and Holocene, continental glaciers have repeatedly advanced and receded in more-or-less periodic fashion. James Croll in the 1860's and Milutin Milanković in the 1920's speculated on astronomical effects causing these comings and goings, but they were hampered by inadequate knowledge of these variations. In the 1960's and 1970's, detailed records of these comings and goings were discovered in oxygen-18 variations in sediment cores from deep-sea drilling. In 1976, JD Hays, John Imbrie, and NJ Shackleton demonstrated a correlation between these O-18 variations and these astronomical cycles. Nevertheless, it has been somewhat difficult to model cause and effect, like the "100,000-year problem" of glacial-cycle length.
Geologists have found evidence of astronomically-induced climate cycles much further back in time, and this has enabled dating the base of the Miocene to the remarkable precision of 23.04 million years, and also checking a precise radiometric age of the Cretaceous-Paleogene disaster, 66.0 million years. This improved precision is related to something that detecting these cycles can do: improving dating of strata between radiometrically-dated strata.
An "astronomical timescale" is almost complete for the entire Phanerozoic, with some gaps remaining. There are some scattered observations of cyclicity in the Ediacaran and late Cryogenian, to 650 million years ago, and some more scattered observations the rest of the way to the base of the Proterozoic, 2.5 billion years ago.
Comparing past cyclicity to recent cyclicity reveals that the past orbital cycles have the same periods as the recent ones, meaning that the Solar System has not had much overall change for half of its existence. Doing that comparison also reveals that the Earth did faster spin precession in the past, meaning that it rotated faster, and rotated faster in approximate agreement with other sources. For instance, the Earth's rotation period at the base of the Proterozoic, 2.5 billion years ago, was around 17 hours.
It must be pointed out that uncertainties in our knowledge of the Earth's past spin precession, and also of the planets' past orbit parameters, are uncertainties that limit the precision of ages much before the base of the Miocene.
Nevertheless, the agreement of radiometric and astronomical dating is confirmation of the great age of our home planet.
-- References --
Long Periodic Terms in the Solar System - NASA Technical Reports Server (NTRS)
P. Bretagnon
https://ntrs.nasa.gov/citations/19830009163
Milankovitch cycles - Wikipedia
https://en.wikipedia.org/wiki/Milankovitch_cycles
Variations in the Earth's Orbit: Pacemaker of the Ice Ages | Science
JD Hays, John Imbrie, NJ Shackleton
Science, Vol 194, Issue 4270, pp. 1121-1132, 10 Dec 1976
https://www.science.org/doi/10.1126/science.194.4270.1121
Mid-Pleistocene Transition - Wikipedia
https://en.wikipedia.org/wiki/Mid-Pleistocene_Transition
100,000-year problem - Wikipedia
https://en.wikipedia.org/wiki/100,000-year_problem
Astronomical calibration age for the Oligocene-Miocene boundary | Geology | GeoScienceWorld
Nicholas J. Shackleton; Michael A. Hall; Isabella Raffi; Lisa Tauxe; James Zachos
https://pubs.geoscienceworld.org/gsa/geology/article-abstract/28/5/447/188532/Astronomical-calibration-age-for-the-Oligocene
Geology (2000) 28 (5): 447–450.
Cyclostratigraphy and the Astronomical Time Scale | MicroAccess
Linda A. Hinnov and James G. Ogg
https://www.micropress.org/microaccess/stratigraphy/issue-239/article-1523
Stratigraphy Volume 4, No. 2-3 pp. 239-251
Direct high-precision U–Pb geochronology of the end-Cretaceous extinction and calibration of Paleocene astronomical timescales - ScienceDirect
William C. Clyde, Jahandar Ramezani, Kirk R. Johnson, Samuel A. Bowring, Matthew M. Jones
https://www.sciencedirect.com/science/article/abs/pii/S0012821X16303971
Earth and Planetary Science Letters, Volume 452, 15 October 2016, Pages 272-280
Astronomical Time Scale for the Mesozoic - Astrophysics Data System
Huang, C.
https://ui.adsabs.harvard.edu/abs/2018AGUFMPP53C1216H/abstract
Astronomical time scale for the Paleozoic Era - ScienceDirect
Huaichun Wu, Qiang Fang, Linda A. Hinnov, Shihong Zhang, Tianshui Yang
https://www.sciencedirect.com/science/article/abs/pii/S001282522300199X
Earth-Science Reviews, Volume 244, September 2023, 104510
Pre-Cenozoic cyclostratigraphy and palaeoclimate responses to astronomical forcing | Nature Reviews Earth & Environment
David De Vleeschouwer, Lawrence Percival, Nina M. A. Wichern, and Sietske J. Batenburg
https://www.nature.com/articles/s43017-023-00505-x
A 650-Myr history of Earth’s axial precession frequency and the evolution of the Earth-Moon system derived from cyclostratigraphy | Science Advances
Yujing Wu, Alberto Malinverno, Stephen R. Meyers, Linda A. Hinnov
https://www.science.org/doi/10.1126/sciadv.ado2412
Science Advances, 16 Oct 2024, Vol 10, Issue 42
Geological evidence confirms the staircase patterns of Earth’s rotation deceleration from the Neoproterozoic to the Mesozoic Era
He Huang, Chao Ma, Matthias Sinnesael, Mohammad Farhat, Nam H. Hoang, Yuan Gao, Christian Zeeden, Hanting Zhong, Mingcai Hou, Chengshan Wang, Jacques Laskar
https://eartharxiv.org/repository/view/6024/
https://www.pnas.org/doi/abs/10.1073/pnas.2317051121
August 6, 2024, 121 (33) e2317051121
Earth-Moon dynamics from cyclostratigraphy reveals possible ocean tide resonance in the Mesoproterozoic era | Science Advances
Maoyang Zhou, Huaichun Wu, Linda A. Hinnov, Qiang Fang, Shihong Zhang, Tianshui Yang, Meinan Shi
https://www.science.org/doi/10.1126/sciadv.adn7674
Science Advances, 2 Aug 2024, Vol 10, Issue 31
Empirical Reconstruction of Earth‐Moon and Solar System Dynamical Parameters for the Past 2.5 Billion Years From Cyclostratigraphy - Zhou - 2022 - Geophysical Research Letters - Wiley Online Library
Maoyang Zhou, Huaichun Wu, Linda A. Hinnov, Qiang Fang, Shihong Zhang, Tianshui Yang, and Meinan Shi
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL098304
Geophysical Research Letters, Volume 49, Issue 16, 28 August 2022
-- The Cycles --
The Earth's spin is well-known for its precession. The Earth's north pole makes a circle around its orbit's north pole with an angle of around 23d and a period of around 25,700 years. But its orbit also precesses, from the gravity of the other planets, and those planets' orbits also precess in the same fashion, also from that gravity.
The Earth's orbit pole makes multiple overlapping cycles, a Spirograph pattern, 1 or 2 degrees in size, around the Solar System's angular-momentum vector. Its orbit eccentricity and perihelion direction can be multiplied to make the "eccentricity vector", and that vector also makes multiple overlapping cycles. The cycle periods are from around 50,000 years to around 100,000 - 200,000 years to 2 million years.
These precessions have three main effects that cause variations of incoming sunlight (insolation). They are approximately cyclic: the Milankovitch astronomical cycles.
1. Precession: is the Earth closest to the Sun (perihelion) in spring, summer, fall, or winter? It is farthest from the Sun (aphelion) in the opposite season. This cycle has a period of roughly 21,000 years. It combines the precessions of the Earth's spin axis and of the Earth's perihelion direction.
2. Obliquity: The Earth's axial tilt, presently 23.45d, varies between as low as 22.1d and as high as 24.5d in a cycle of roughly 41,000 years. It results from the Earth's orbit precession. The higher the tilt, the hotter the summers and the colder the winters in both the Northern and the Southern Hemispheres.
3. Eccentricity: the higher the eccentricity, the closer to the Sun at perihelion and the farther from the Sun at aphelion. Currently 0.0167, it varies from near 0 to 0.05 and greater, with periods of roughly 100,000 years and of 405,000 years. It results from multiple cycles combining. Higher eccentricity means hotter at perihelion and cooler at aphelion.
These effects make glaciers come and go. To a first approximation, when the effects combine to make hot summers, glaciers tend to melt, and when they combine to make mild summers, glaciers tend to accumulate. It is summers that are important, because it is summers that make glaciers melt.
-- What We Observe --
Over the last 2.58 million years, in the Pleistocene and Holocene, continental glaciers have repeatedly advanced and receded in more-or-less periodic fashion. James Croll in the 1860's and Milutin Milanković in the 1920's speculated on astronomical effects causing these comings and goings, but they were hampered by inadequate knowledge of these variations. In the 1960's and 1970's, detailed records of these comings and goings were discovered in oxygen-18 variations in sediment cores from deep-sea drilling. In 1976, JD Hays, John Imbrie, and NJ Shackleton demonstrated a correlation between these O-18 variations and these astronomical cycles. Nevertheless, it has been somewhat difficult to model cause and effect, like the "100,000-year problem" of glacial-cycle length.
Geologists have found evidence of astronomically-induced climate cycles much further back in time, and this has enabled dating the base of the Miocene to the remarkable precision of 23.04 million years, and also checking a precise radiometric age of the Cretaceous-Paleogene disaster, 66.0 million years. This improved precision is related to something that detecting these cycles can do: improving dating of strata between radiometrically-dated strata.
An "astronomical timescale" is almost complete for the entire Phanerozoic, with some gaps remaining. There are some scattered observations of cyclicity in the Ediacaran and late Cryogenian, to 650 million years ago, and some more scattered observations the rest of the way to the base of the Proterozoic, 2.5 billion years ago.
Comparing past cyclicity to recent cyclicity reveals that the past orbital cycles have the same periods as the recent ones, meaning that the Solar System has not had much overall change for half of its existence. Doing that comparison also reveals that the Earth did faster spin precession in the past, meaning that it rotated faster, and rotated faster in approximate agreement with other sources. For instance, the Earth's rotation period at the base of the Proterozoic, 2.5 billion years ago, was around 17 hours.
It must be pointed out that uncertainties in our knowledge of the Earth's past spin precession, and also of the planets' past orbit parameters, are uncertainties that limit the precision of ages much before the base of the Miocene.
Nevertheless, the agreement of radiometric and astronomical dating is confirmation of the great age of our home planet.
-- References --
Long Periodic Terms in the Solar System - NASA Technical Reports Server (NTRS)
P. Bretagnon
https://ntrs.nasa.gov/citations/19830009163
Milankovitch cycles - Wikipedia
https://en.wikipedia.org/wiki/Milankovitch_cycles
Variations in the Earth's Orbit: Pacemaker of the Ice Ages | Science
JD Hays, John Imbrie, NJ Shackleton
Science, Vol 194, Issue 4270, pp. 1121-1132, 10 Dec 1976
https://www.science.org/doi/10.1126/science.194.4270.1121
Mid-Pleistocene Transition - Wikipedia
https://en.wikipedia.org/wiki/Mid-Pleistocene_Transition
100,000-year problem - Wikipedia
https://en.wikipedia.org/wiki/100,000-year_problem
Astronomical calibration age for the Oligocene-Miocene boundary | Geology | GeoScienceWorld
Nicholas J. Shackleton; Michael A. Hall; Isabella Raffi; Lisa Tauxe; James Zachos
https://pubs.geoscienceworld.org/gsa/geology/article-abstract/28/5/447/188532/Astronomical-calibration-age-for-the-Oligocene
Geology (2000) 28 (5): 447–450.
Cyclostratigraphy and the Astronomical Time Scale | MicroAccess
Linda A. Hinnov and James G. Ogg
https://www.micropress.org/microaccess/stratigraphy/issue-239/article-1523
Stratigraphy Volume 4, No. 2-3 pp. 239-251
Direct high-precision U–Pb geochronology of the end-Cretaceous extinction and calibration of Paleocene astronomical timescales - ScienceDirect
William C. Clyde, Jahandar Ramezani, Kirk R. Johnson, Samuel A. Bowring, Matthew M. Jones
https://www.sciencedirect.com/science/article/abs/pii/S0012821X16303971
Earth and Planetary Science Letters, Volume 452, 15 October 2016, Pages 272-280
Astronomical Time Scale for the Mesozoic - Astrophysics Data System
Huang, C.
https://ui.adsabs.harvard.edu/abs/2018AGUFMPP53C1216H/abstract
Astronomical time scale for the Paleozoic Era - ScienceDirect
Huaichun Wu, Qiang Fang, Linda A. Hinnov, Shihong Zhang, Tianshui Yang
https://www.sciencedirect.com/science/article/abs/pii/S001282522300199X
Earth-Science Reviews, Volume 244, September 2023, 104510
Pre-Cenozoic cyclostratigraphy and palaeoclimate responses to astronomical forcing | Nature Reviews Earth & Environment
David De Vleeschouwer, Lawrence Percival, Nina M. A. Wichern, and Sietske J. Batenburg
https://www.nature.com/articles/s43017-023-00505-x
A 650-Myr history of Earth’s axial precession frequency and the evolution of the Earth-Moon system derived from cyclostratigraphy | Science Advances
Yujing Wu, Alberto Malinverno, Stephen R. Meyers, Linda A. Hinnov
https://www.science.org/doi/10.1126/sciadv.ado2412
Science Advances, 16 Oct 2024, Vol 10, Issue 42
Geological evidence confirms the staircase patterns of Earth’s rotation deceleration from the Neoproterozoic to the Mesozoic Era
He Huang, Chao Ma, Matthias Sinnesael, Mohammad Farhat, Nam H. Hoang, Yuan Gao, Christian Zeeden, Hanting Zhong, Mingcai Hou, Chengshan Wang, Jacques Laskar
https://eartharxiv.org/repository/view/6024/
https://www.pnas.org/doi/abs/10.1073/pnas.2317051121
August 6, 2024, 121 (33) e2317051121
Earth-Moon dynamics from cyclostratigraphy reveals possible ocean tide resonance in the Mesoproterozoic era | Science Advances
Maoyang Zhou, Huaichun Wu, Linda A. Hinnov, Qiang Fang, Shihong Zhang, Tianshui Yang, Meinan Shi
https://www.science.org/doi/10.1126/sciadv.adn7674
Science Advances, 2 Aug 2024, Vol 10, Issue 31
Empirical Reconstruction of Earth‐Moon and Solar System Dynamical Parameters for the Past 2.5 Billion Years From Cyclostratigraphy - Zhou - 2022 - Geophysical Research Letters - Wiley Online Library
Maoyang Zhou, Huaichun Wu, Linda A. Hinnov, Qiang Fang, Shihong Zhang, Tianshui Yang, and Meinan Shi
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL098304
Geophysical Research Letters, Volume 49, Issue 16, 28 August 2022
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