In 1665, Newton's apple took exactly one second to fall. Today the apple takes longer. Why?
In the 1930's when astronomers checked back in time over observations made over several centuries, they were overly surprised when they discovered that Earth's Day had been growing steadily longer at about a fifth of a second every century.
Confirmation came through the branch of geology concerned with the study of the fossil remains of animal and plants life of past geological periods (paleontology). Paleontologists found that patterns of coral growth about 400 million years ago pointed out that a year in that distant "time" was some 400 days long. The Earth used to spin faster, making each day slightly shorter.
Corals occur as polyps only and usually are colonial, living in shallow ocean waters. They emit a secretion colored in a hard red or white. The reason they do that is to protect and support the polyps. Coral reefs and those in the shape of a ring or horseshoe enclosing a shallow stretch of water separated from the sea, are formed from broken "coral skeletons."
In 1938, Paul Dirac, a physicist, pointed out that "the laws of the universe" led to some odd predictions concerning "the behavior of gravity" specifically, "gravity would grow weaker as the universe aged."
The prediction was given as a result of the observation of the Earth's gravity 400 millions years ago, when the whole universe was settling or begin to cool off.
Dirac's observation remained as no more than a interesting footnote, given the fact that many theories related to the formation of the world were dormant in those years.
In the 1970s, mounting geological evidence suggested that the Earth was originally only about 80 per cent of its present size, scientists were force to accept an inescapable conclusion :
"Since it is GRAVITY that HOLDS the Earth TOGETHER, WEAKENING GRAVITY must be the reason that the globe expanded. This expansion slowed down the ROTATION of the Earth."
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