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by
Stephen W. Hurrell
Abstract
Measuring the Earth’s surface gravity today (1g) is a simple scientific procedure. Only two measurements are required: weight and mass. Palaeogravity can therefore be calculated by calculating the weight of a mass that existed in the past. An extinct animal can be used to calculate palaeogravity using the weight-mass method if both its weight and mass are known.
Palaeogravity can be calculated from:
ga = wa / m
where ga is palaeogravity at some predefined age, wa is the weight at that age and m is the mass. Since mass never varies it does not need a subscript to denote its age.
For weight: the weight of extant land-based animals can be compared to the dimensions of their leg bones to derive a formula for weight based on leg bone dimensions. This formula can also be used to calculate the weight of extinct land-based animals. For mass: palaeontologists have produced accurate reconstructions of a large number of extinct animals. These reconstructions allow the mass of land-based animals to be calculated from their body volumes and tissue density.
The weight-mass technique can be used to calculate palaeogravity for a range of time periods based on a number of animals. Coelophysis predicts 0.42g and 0.44g at 210 million years ago (Ma), Megalosaurus: 0.51g at 167 Ma, Giraffatitan: 0.54g at 152 Ma, Acrocanthosaurus: 0.54g at 113 Ma, Gigantoraptor: 0.61g at 80 Ma, Euoplocephalus: 0.65g at 76 Ma, Tyrannosaurus rex: 0.67g, 0.66g, 0.61g, and 0.64g at 67 Ma, Ankylosaurus: 0.69g at 67Ma and Paraceratherium: 0.73g, 0.81g and 0.85g at 29 Ma. These calculations can be examined in more detail at https://dinox.org/pub.
The results indicate that, far from being the constant assumed, the Earth’s surface gravity was substantially less in the past and has slowly increased towards our present day surface gravity.
Also see - Rg
This presentation was prepared for the Polish Geological Congress due to be held from 16 - 18 June 2020 at Poznań, Poland. Unfortunately, the Coronavirus Pandemic meant the congress did not take place, so I have placed a homemade version here and a YouTube version at: https://youtu.be/qGO16O4PLJs
See also article: Can we calculate palaeogravity?
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Page updated 14 Jul 2026
Comments
From YouTube - @anthonylucas7351 Hi Stephen, Great to see your work pulling together into one cohesive argument.
From YouTube - @dehilster Stephen: could you present this during one of our Saturday Morning live video conference?
@DinoxOrg2 Sure.
From YouTube - @0U8123MTA3 Great presentation. Just bought your book. I tried to determine the femur thickness of an Argentinosaurus if it were to be walking around today at a weight of 90 metric tons and came up with 37cm femur thickness assuming the same bone strength of an African elephant. I understand the fossils show Argentinosaurus only had a 25cm femur thickness. Do you have similar calculations? I know there are a lot of variables like bone density that are hard to account and calculations are only estimates but your research seems very reasonable and would like to know if you have estimates similar to mine. Thanks.
@DinoxOrg2 It's great to hear you are trying to calculate palaeogravity for yourself! The femur circumference of Argentinosaurus is 1114 mm but there are no fossils of the humerus. Calculations can't be as accurate (since we don't know the weight distribution between the front and rear legs) so I haven't looked at that dinosaur in great detail - but the results are similar. I find that theropod dinosaurs seem to give the most accurate results. Check out my papers for details: https://www.dinox.org/publications.html
@0U8123MTA3 Thanks for the guidance on that. It's nice to have actual data for my equations. I've seen how the ocean floors seem to have spread the continents apart. Lately I looked at elevation maps and can see that the contours around 250 meters fit together like a puzzle on every continent. To me it is proof the continents were stretched over the low elevations and compressed in the mountainous zones. It is most evident to me looking at this map: http://serc.carleton.edu/images/eyesinthesky2/installgis/word_elevation_proj ect.jpg
From YouTube - @eugeneellis6762 Reduced gravity on a smaller earth permits larger life sizes. The biggest recorded land creature today is a 12 ton elephant killed in 1955. Accordingly, the largest Mesozoic life size possible with a 50% reduction in gravity would be a dinosaur weighing 24 tons (12 t / 0.50 g). The Giraffatitan data (31.59 tonnes = w) producing 54% gravity at 152 Ma would be limited to a maximum size of 22.22 tons (12 t / 0.54 g) or 20.16 tonnes. This test (12 tons ÷ x % g) indicates when the estimated weight (w) exceeds the maximum survivable weight in such reduced gravity.
Oversized fossils reveal the minerals replacing the organic bone substances are compatibly growing with the embedding earth. Geologically dating “the surroundings” can adequately (within 20%) predict the corresponding surface gravity and earth size as indicated on this Past Gravity Comparison chart: https://ionic-expanding-earth.weebly.com/past-gravity-comparison.html.
From YouTube - @Clovislast But dinosaurs get larger and larger as time progresses toward the present. 150 million years ago the dinosaurs were smaller than 65 million years ago. The biggest sauropods were all in the late cretaceous, at least that is my recollection. I'd be open to hearing this is not the case. But if gravity is getting stronger, we should see a steady trend of dinosaurs becoming smaller. We don't see this disruption in size increase until the 5th extinction event.
From YouTube - @AlekseySobyanin The dinosaurs weren't shrinking! The largest dinosaurs (Dreadnoughts and tyrannosaurs) lived at the end of the Cretaceous period, before the extinction. Why were dinosaurs very small in the Permian and Triassic periods? If you understand paleontology, you will see that the size of the animals is only growing. Your hypothesis is wrong. I was comparing two animals of the same size - a modern elephant and a centrosaurus from the Cretaceous period. Centrosaurus has supporting bones ( femur ) thicker by 2 times with the same length as an elephant. The bone walls are also twice as thick. If gravity had been less, then the bones of an ancient "elephant" should have been thinner, but in reality the bones are thinner than those of a modern one. This shows that the load on the bones of ancient animals was much greater. the hypothesis that the force of gravity is decreasing. The earth grows and decompresses. The high gravity was the reason why the animals came ashore so late. Modern animals have very thin bones, which is also a consequence of low gravity.
From Facebook - Ray McCrea More proof of the expanding Earth. There is no way that those giant animals could have even supported themselves, let alone chase other giant animals around.