Chapter  13

It is a known fact that the rotation of the Earth is gradually slowing. For four and one half billion years, its entire life, it has been slowing down. As the Earth loses its kinetic energy due to all forms of friction acting on it (tides, galactic space dust, etc.) like any other flywheel, it will slow down. From time to time our timekeepers must adjust their super accurate atomic clocks to synchronize them with the Earth's slowing rotation whose day/night cycles we base our lives on.

As the planet's rotation slows, the time it takes for one rotation increases at an extremely slow rate (milliseconds per century). Over billions of years these milliseconds have added up to become seconds and then to minutes and finally to hours. As the day/night cycles become longer the action causes the planet's shape to slowly change from an oblate to a more perfect sphere shape.

While we know the Earth's rotation is slowing, that is NOT the reason why the extra "Leap Second" is added by our official time keepers every so often. The reason for adding a leap second is that the planet does not rotate exactly once every 24 hours (86,400 seconds). The rotation actually takes 86,400.002 seconds so that each day this little difference builds up between the atomic clock and the earth's rotation.

The Earth's rotation is slowing but at a much slower rate than 1 leap second every so many years. The length of time it takes the Earth, at the present time, to rotate once is 86,400.002 seconds compared to 86,400 seconds back in 1820. The rotation has slowed roughly only by 2 milliseconds since 1820. That seems like an insignificant amount of time BUT over the course of the planet's entire lifetime, it has had very profound effects on the geophysics of the planet.

It has caused mountains to rise, earthquakes, etc. to occur as we will see. This article is about, factoring in the tremendous geophysical activity that was caused, by the Earth's slowing rotation; in the interior of the planet, its crust, oceans and atmosphere over its entire lifetime.

The Sub-bureau for Rapid Service and Predictions of Earth Orientation Parameters of the International Earth Rotation Service (IERS), located at the US Naval Observatory, monitors the Earth's rotation. Part of its mission involves the determination of a time scale based on the current rate of the rotation of the Earth.

They estimate that the Earth's rotation is slowing at about 1.4 milliseconds per solar day per century which roughly agrees with the rate of rotation of the Earth has actually slowed down since 1820. Tracing these tiny milliseconds back for 4.5 billion years adds up to a very significant amount of time for a solar day. I have determined that the day/night rotation was 63,000 seconds shorter than the present 86,400 seconds it is today. This would put the Earth's rotation at about 6.5 hours per day/night cycle, when it was created, 4.5 billion years ago. (This is a much faster rate of rotation than the Cassini-Huygens mission (2003 to 2004) determined Saturn's present 10.5 hours rotation period to be.)

This rate of rotation would have exerted tremendous stress throughout the newly formed planet. If the rate of rotation has been slowing fairly constantly, over the ages, we can see that the earth was rotating very fast originally for it to slow down to the present 24 hour rate it is today. What ever it was - its angular momentum was much faster and therefore its "centrifugal force" was much stronger when the planet was very young. This caused the young, faster spinning Earth to have a much more pronounced oblate shape, possibly even having a "Saturn type ring" orbiting around it.

In the past, when the Earth was younger and spinning faster, the stronger angular momentum caused the Earth to assume a more pronounced oblate spheroid shape much greater than the twenty-seven miles it is today. A 10% increase in the equatorial circumference of the faster rotating young planet, relative to its present rotation, could produce approximately 2500 more miles of surface around the young planet's equatorial zone (waistline).

This was a lot of surface to crunch into the ever changing shape of the planet as its rotation gradually slowed over the ages. Since the ratio of strength of gravity and angular momentum (centrifugal force) is always changing, the shape of the planet never reaches equalibrium - it is always changing.

(The fast spinning star, Vega, makes a full rotation about its axis once every 12.5 hours, (compared to the Earth's early rate) which causes it to assume a 23% ellipical bulge at its equator, so a 10% greater bulge for the faster spinning Earth is not out of the question.)

The constant struggle between gravitational force and the weakening angular momentum caused by the slowing of the Earth's rotation, has had a profound effect on the Earth's geophysical activity throughout the ages. This constant struggle between these two gigantic forces has caused a continual adjusting of the Earth's shape as the ratio of the strengths of angular momentum and gravity have changed. The earth's shrinking waistline was causing tremendous stress on the planet.

Gravity is a centripetal force, it exerts its tremendous force inward, toward the center of gravity, always trying to form the Earth into a perfect sphere while the angular momentum is a centrifugal force that causes the oblate shape of the Earth. The angular momentum of the spinning planet tends to adjust the bulge to fit the changing conditions. A stronger angular momentum due to a faster rotation would increase the Earth's bulge while a weaker angular momentum due to a slowing rotation would allow gravity to form the planet into a more perfect sphere. Evidence indicates the rotation is constantly slowing however so that its centrifugal force is growing weaker.

The decrease in the size of the equitorial bulge may also had some effect on the Earth's angular momentum but the bulge does not decrease fast enough to actually increase the rotation of the Earth by any significant amount. Plus the fact all the leap seconds have been positive, indicating that the Earth is constantly slowing.

Gravity (a centripetal force) and the centrifugal force caused by the Earth's rotation has had a profound effect on the Earth's geophysical activity throughout the ages. These are the two basic forces that caused the Earth to assume its spheroid shape. Throughout the life of the Earth there has been a relentless struggle between these two forces. Gravity is a centripetal force, it exerts its tremendous force inward toward the center of gravity, always trying to form the Earth into a perfect sphere. Centrifugal force on the other hand, exerts an outward tangential force on the Earth. The strengths of these two forces working against each other is the determining factor that causes the Earth to assume its shape.

In the past, when the Earth was younger and spinning faster, the stronger centrifugal force acting on the Earth caused it to assume a more pronounced oblate spheroid shape. (At the present time the planet Saturn is spinning much faster then the Earth and displays this more pronounced oblate spheroid shape.) When the Earth was spinning faster the bulge was much greater then the twenty-seven miles it is today. A 5% increase in the equatorial circumference of the Earth due to greater centrifugal force would produce approximately 1200 more miles of surface around the equatorial zone.

If the Earth's rotation was not slowing its shape would have remained constant throughout the ages. Its rotation is gradually slowing however, (even taking the conservation of momentum into consideration), causing the centrifugal force to become progressively weaker. The centripetal force of gravity remains just as strong as ever and continues to exert the same amount of pressure. This continuous weakening of centrifugal force in comparison with the stable gravitational force causes a continuing imbalance between these forces. This ongoing struggle causes tremendous dynamic movement within the Earth as it adjusts shape, to balance these opposing forces. It is gradually changing its shape from that of an oblate spheroid with a bulging equator and flatter pole regions to that of a more perfect sphere to conform with the current strengths of these forces. Throughout the ages, since its birth, the Earth has been going through this constant gradual change.

The surface of the Earth's mantle, especially in the tropical and subtropical regions of the Earth is becoming smaller while the pole regions have uplifted and become rounder. The fact that the Earth is getting rounder, even today, has been confirmed by the satellite "Lageos" which is being monitored by scientists at the University of Texas Center for Space Research and at the Jet Propulsion Laboratory.

This slow continual change of the Earth's interior has set up tremendous dynamic pressures and stress within the Earth's crust as it endeavors to conform with the ever changing mantle upon which it floats. It is the imbalance between these forces that cause the dynamic movements of the continental crustal plates as the crusts shifts and crunches to fit into the ever changing area. These are the forces that cause earthquakes to occur, volcanoes to erupt and the Earth's vast mountain ranges to rise. As the equatorial oblate shape of the Earth shrinks the immense resulting pressure within the mantle causes it to gradually ooze upward creating the Atlantic and Pacific ridges.

The Earth's slowing rotation also had a profound effect on its climate over the ages. In the past, the stronger centrifugal force caused the Earth's ocean waters to concentrate more in the tropical and subtropical regions. The Earth's tidal bulges, due to this concentration, were greater also. This left the oceans in the pole regions very shallow.

Even today the Arctic Ocean's average depth is more shallow then the oceans in the equatorial regions. Also the continent of Antarctica's plateau has greater average height above sea level then the other continents, even though burdened with heavy glaciers. This is probably due to the lower sea level in the pole regions rather then a higher continent. The concentration of ocean water over a much larger area, due to its more oblate shape in the warmer regions of the Earth, must have had a profound effect on the Earth's climate in past geological times.

The faster rotation also had an enormous effect on the Earth's dynamic atmosphere creating more energetic global winds and greater evaporation. The blanket of atmosphere may also have been thicker in the equatorial regions. The final result of all these effects created a vastly different climate then our present climate. These effects where greatest in the Pre-Cambrian age of geological time. They have become more subdued, but still evident, in the later geological ages as our planet's rotation continues to gradually slow.

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