Posted by: T. Boyd | May 17, 2009

As the world turns slower

His eternal power and divine nature have been clearly perceived ever since the creation of the world, in the things that have been made.” (Romans 1:20 ESV)

The spinning of the earth is very gradually decreasing.  The length of a day, which was exactly 24 hours in 1820 will be one second longer in about 50000 years.  So the slowing is real, but I don’t think it will affect your beach time very much!

A granddaughter at the beach

A granddaughter at the beach

What is causing the slow down?  Our “giant” moon is the culprit.  Our moon is about 1/4 the diameter of its host, earth – much larger than other moons compared to their hosts.  This causes the ocean and land tides to be much higher than they would be with a smaller moon.  The tides create friction, so the energy taken away by this process causes the earth to gradually spin more slowly.

There is an interesting consequence of the slowdown.  It causes the moon to move away from the earth about 1.5 inches per year. Since man landed on the moon forty years ago, it is about 5 feet further away from the earth.  This change in distance has been verified with laser light bounced off the moon (the astronauts left a special reflector on the moon’s surface for this experiment).

There is an extension of Newton’s laws of motion and gravity called the law of conservation of angular momentum.  Since the angular momentum for the earth is decreasing, then that of the moon orbiting the earth has to increase to keep the total angular momentum constant.  Moving away from the earth preserves that balance.

As one of my less serious students at Caroline High asked during class, “Who made these laws, and why do we have to obey them?”  After the laughter quieted down, I explained that the laws of nature are used to describe the motion of the universe and they never have been violated as far as we knew.

Maybe next time I am at the beach along the Atlantic coast line, and notice the tide coming in or receding, I will be able to say, “Just think – that tide is making the moon move away from us about 0.004 inches every day.”  And along with praising the Lord for the beauty along the coastline, I can thank Him for helping us use our minds for discovering these scientific principles which help us understand the creation.

Most of these articles are also at a much faster-loading site:

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