Chapter 9: Mechanism of gravity change

There are three possible causes. The first lies in the possibility that the physical gravitational constant may have changed.

In 1938, the scientific world was shaken by the paper "A new basis for cosmology" by the English physicist Paul Dirac in which he stated that the gravitational constant was declining. In this theory, the age of the universe = electrical force/gravity. Therefore, as the universe ages, the gravitational force becomes less and less. This theory has yet to be proven true, and if it were true, it still would not account for sudden changes. Furthermore, if gravity did change, it would affect the planets and the stars and eventually the whole universe, and the consequences would have been much more than the extinction of the dinosaurs.

The second possibility is that the mass of the Earth has increased and consequently its gravity has also grown. And the only way for that to happen would be through the addition of an extraterrestrial mass.

There is a theory that at the end of the Cretaceous an unimaginable amount of meteorites fell on the Earth and added to its size. But the historical record of the Earth--the geological strata--shows no such sudden growth. What if the objects that hit the Earth were not meteorites but a small black hole captured by the Earth's gravity and trapped within, even to this day? A fascinating idea, isn't it? Whether such an occurrence is possible is unknown, and even if it were, once again the effects would be much more than dinosaurs dying off.

So we now come to the last possibility. Let us think of a case where the gravitational constant remains unchanged while a third force acts to cancel out the effects of gravity. We tend to think of gravity as unchanging and constant, but we must forget the centrifugal force that always acts on rotating objects. People on twisting roller coasters do not fall out even when upside down because the centrifugal force is greater than the gravity of the Earth. In physics, centrifugal and gravitational forces are indistinguishable, so the gravity acting on an object on the surface of the Earth can be expressed as the vector sum of the gravitational force and the centrifugal force that results from the Earth's rotation. Therefore, if the Earth's rotational velocity changes, the gravity will of course also change.

The centrifugal power acting on an object that weighs (m) is calculated as follows:

(m) x (distance from the center: r) x (rotation angle speed ½)2

therefore the centrifugal force acting on an object weighing 1 kilogram lying at the equator is:

1kg x 6378140m (earth's radius) x 5.3110 x 10-9 rad/s (rotation angle speed squared) = 0.0339N, which is 1/289 of its mass and is such a small number that it can be ignored.

If the Earth's rotation increased by 5 times the calculations would go:

1 x 6378140 x 1.329310-7 = 0.8478N that is 1/11.5 of its mass, which means it becomes 10% lighter. If the velocity becomes 10 times as fast, it would become 1 x 6378140 x 5.317310-7 = 3.391N that is 1/2.9 of its mass, and the weight decreased to two-thirds. When rotational velocity is 15 times as fast, it would calculate 1 x 6378140 x 1.196410-6 = 7.631N and the weight decreases to about 1/4. When the velocity grows to 17 times, the Earth's gravity is completely cancelled out.

I hope the above explanation helps to understand how great the influence of centrifugal force has on gravity.

That's right! During the age of the dinosaurs, the Earth was rotating at a much greater speed than today. In fact, the rotational velocity immediately after the creation of the Earth was far higher, and one of the theories of the formation of the Moon has it been flung out because of the strong centrifugal forces.

If centrifugal forces counteract terrestrial gravity and lessens its effect, then it would be natural for the centrifugal force to decrease and gravity increase in high latitudes since it much closer to the center of rotation.

Dinosaur fossils are presently being found in the polar regions, but they are all relatively small. Fossils of dinosaurs related to Allosaurus, a large carnivore, have been found in Dinosaur Cove in Australia which was near the pole at the time, though they were only about 2 meters in length. Although no one knew the reasons for that at the time of their discovery, it would make sense if the gravity in the polar regions were much greater than nearer the equator.

Translated by Rie Ishida