Science: Astronomy:


The Expansion of the Earth

and the Extinction of the Dinosaurs


by Dr. Kiril P. Panov, Astronomer

Sofia, Bulgaria


Why did the dinosaurs disappear? That is a question that is most popular not only with the scientific community, but also with the general public. Dinosaurs appeared during the Triassic period, some 230 million years ago. They dominated terrestrial life for more than130 million years, especially during the Jurassic period. Then, by the end of the Cretaceous period (about 65 million years ago) dinosaurs suddenly disappeared.


Suddenly means very fast with respect to geological timing. Nobody knows how fast, it could be several years, or may be several decades. What happened on Earth? Obviously, some terrible global catastrophic event occurred. Could it be a major asteroid impact? During the history of Earth catastrophic impacts by asteroids or comets could have happened repeatedly, although big asteroid encounters are quite rare. In 1980 Walter Alvarez and collaborators [1] came up with the hypothesis about a major impact event by the end of the Cretaceous era, some 65 million years ago. This hypothesis is supported by the detection of a global-wide enhanced layer of iridium, dated at about the same time. This element is rare in the Earth’s crust, but is often found in meteorites. In addition, traces of a giant crater (the Chicxulub crater) with a diameter of 180 km were found on the Yucatan Peninsula (Mexico) that could be dated at about the same time – 65 million years ago.


Such a major impact could indeed cause a mass-extinction of life on a global scale. It is not so much the direct hit that killed terrestrial species (~ 70% of all species on Earth!) but the global cooling, caused by the enormous amount of dust and ashes ejected by the impact in the atmosphere. This layer of dust in the atmosphere shielded solar irradiance during many years. The effect of cooling for animals was that the chain of food was broken, and most affected by the insufficient food were the largest animals – the dinosaurs. It was not possible for them to adapt to the sudden cooled global environment and so they had to disappear. Smaller animals that needed less food and birds that learned to brood their eggs themselves and could partly survive the impact, starting a new era of life on Earth. The birds of today, and a few species of reptiles, are the only descendants from Jurassic life.


So, it seems that the big dinosaurs turned out to be the most vulnerable in time of catastrophic event. But why should Nature create such large animals in the Jurassic era, since an excess of muscles needs an excess of food, and that makes them vulnerable? This is a very interesting question. Animals find their food by moving. The capability to move (on the solid ground or in the air) is of primary importance for the animals’ survival. What would happen, if we would live in an environment of stronger gravity? Then the animals would have to “struggle” against a stronger gravitational force in order to move around.  Since Nature always tends to adapt to the ambience, we could expect that in a stronger gravity environment animals will gradually develop by evolution large strong muscles, and large strong bones to support these muscles. Does this remind you of the Jurassic era? But why should the gravitational force have been stronger in the dinosaur era, and why should the gravitational force decrease afterwards?  At this point, we may be touching a most fundamental problem, a problem that concerns the origin and evolution of galaxies, stars, and planets. The orthodox theory most popular now believes that structures in the universe originated in events of gravitational collapse on different scales – to build structures such as galaxies, stars, and planets. In the framework of this theory it would be impossible to comprehend how gravity could have been stronger on Earth in the Jurassic era, and how the gravitational force could have decreased afterwards to reach its present day value. However, some 70 years ago, Victor Ambartsumian [2] came up with a radically new concept of origin of stars - the disintegration of some primordial dense matter of unknown origin and properties. The introduction of some “obscure” dense matter was not accepted by the astronomical community. People always prefer to stick to ideas that don’t deal with the “unknown”. Well, everything that is unknown is “obscure”.


But later, when discovered and explored, the “obscure” becomes “usual”. This is shown by the whole history of science. If the concept of Ambartsumian is accepted, it leads to a very different picture of the evolution of structures in the Universe. There is a common trend in the evolution of galaxies, stars, and planets – a trend of decreasing densities by increasing dimensions of structures. If this concept is applied to the Earth, it should be that the Earth in the past was smaller but with the same mass, which means the density of Earth was higher. Higher density means stronger gravitational force, and this is how we could explain why dinosaurs had to be big and strong. The evolution of Earth since the Jurassic time increased the Earth’s dimensions by preserving the Earth’s mass, therefore, the mean density of the planet decreased.  This is how we came to the present day lower gravity value. Presently, there are no such giant animals on the surface, neither in the air, as in the Jurassic era (except for the oceans, but this is a different story). Animals are generally smaller because they can now move reasonably well with smaller muscles. This line of argument leads to an interesting question:  what would have happened if there were no catastrophic impact 65 million years ago? My answer to that is: dinosaurs would have had to disappear anyway. They would have become obsolete in the later low-gravity environment.  They did not fit in this environment because they needed too much food, which was no longer necessary – moving could be sustained by less food. The principal “survival of the fittest” would give priority to smaller animals and dinosaurs would have had to disappear anyway.


The scenario of an expanding Earth has already been considered by S.W. Hurrell in his book: “Dinosaurs and the Expanding Earth – Solving the Mystery of the Dinosaurs Gigantic Size” (2004). In Hurrell’s scenario, the Earth should have expanded because of an accumulation of additional mass. The evolution of Earth in his view proceeded with increasing mass and increasing density. He attributes the large sizes of dinosaurs to the lower gravity in the past, quite the opposite to the scenario presented here. From the astronomical point of view, even in the concept of gravitational collapse, there would be not that much mass to be accreted during the past 300 million years. This is not possible.


Besides, if the mass of the Earth increased as much as he believes, the orbit of the Earth would have changed with severe consequences for life. But the idea of expanding Earth is correct – only, it is for a different reason, which was described above.


It seems that the scenario with Earth’s expansion with decreasing density and gravity fits to the story of dinosaurs, but it is essential whether or not this scenario fits also to the geological history. A brief comment should be given below.


In 1912 Alfred Wegener suggested a new theory of “moving continents”. Although this theory seems to account for the obvious shapes of some continents (e.g. the shapes of Africa and South America), his theory was much debated and criticized, because Wegener could not provide the driving force for such movements of the continents.


Without this driving force his theory remained unfounded. Clearly, the driving force that moves continents has to be huge. Recently, precise GPS measurements confirmed that displacements of continents really exist, but the driving force is still missing. The only possible driving force on this extent, in my view, could be the expansion of the Earth. This takes us back to the disintegration scenario. The Earth like all the other planets and satellites was molten in the distant past and this is how all planets and satellites took spherical shape. What was this huge source of heat that could melt an entire planet? It could only be inside the planet (or satellite) itself.  An outside source of heat could really be excluded. The melting could only be provided by processes of disintegration in the early Earth. Obviously, in the distant past activity in the Earth was much more powerful and volcanic activity must have been enormous. By now, volcanic activity and earthquakes seem to have diminished substantially, being the last manifestations of the previously active Earth.  We could be sure that early life was confronted with a very hostile environment and it is a real wonder that life could survive. The real and ever present danger came, however, not from space, but from the inside. Impacts like the one that killed dinosaurs were rare events.


At the end of this short notice, what could be the predictions for the future? Dangers from space (asteroids, comets) are hazardous and therefore unpredictable. What we could try to predict is the activity of the Earth and the sun. Activity of the Earth will continue to decrease and therefore we could live with it. Not so with the activity of the sun. Both the orthodox and the disintegration scenario predict an increase of solar luminosity, when the transition of the sun to the stage of red giant star begins. The orthodox theory believes that this event will not come soon – the Earth may have several billion years more before it will be burned by the expanding sun. The disintegration scenario at present could not predict when this fatal day will come. What is sure is that the Earth will be burned, and there is no escape. It is a “disaster postponed”, no doubt about it. Life will have to move or perish. Maybe, at that time, humans could have moved to another planet (or satellite), farther away from the sun.  I hope so.



[1] Alvarez LW, Alvarez W, et al. Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science 1980; 208 (4448): 1095-1108. 

[2] Ambartsumian VA. La structure et l’evolution de l’univers. 11th Conseil de   Physic Solvay, 1958, Bruxelles.


About the Author:

Dr. Kiril Panteleev Panov graduated from the University of Sofia in Astronomy in 1968, and then furthered his education by earning a Ph.D. degree at the Astrophysical Institute Potsdam in 1974. The following year he joined the Bulgarian Academy of Sciences as a Researcher, and by 1985 he had been promoted to Senior Researcher, a post he still holds today. He is also the Director of the Institute of Astronomy. Dr. Panov has written 75 papers on Astronomy and is the co-author of “Participation in Building the National Astronomy Observatory”.  He was awarded a Certificate of Honor for his numerous contributions to Astronomy and is a member of the International Astronomy Union and the New York Academy of Sciences.


Dr. Panov was born on September 1, 1943 in the Bulgarian town of Belogradchick, the son of Pantaleij Kirov and Nadezhda Vasileva Christova. In 1972 he married Kostadinka Tzvetanova Bakalova, and the couple has been blessed with two children, Nadezhda Kirilova and Marianna Kirilova. In his leisure time Dr. Panov enjoys skiing.


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