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If there was no moon


Anyone thinking that the moon has no influence on the earth and everything on the earth, which includes the air, would benefit from a view of the larger picture. The orientation of the Earth's tilt is locked into its present value (varying 1.3 degrees from the mean value of 23.3 degrees over 41,000 years) by the gravity of the Moon.  Variations in tilt are thought by geologists (so not only astrologers and other shunned parties) to cause planetary ice ages and warm spells.  The moon may be our climate regulator.  If there were no moon, or if it were much smaller, the Earth's tilt would reach values as high as 85 degrees, with disastrous consequences for any life forms trying to weather the resulting climate oscillations.


4.5bn years ago when the Earth was formed, the day was about 7 hours per day/night cycle. It is thought that the moon was created when a rock the size of Mars slammed into Earth. A billion years ago, the moon's tighter orbit than now meant it took just 20 days to go around us to make a lunar month. A day on Earth back then was 18 hours long. At 100 million years ago Earth's rotation period had slowed to 23.6 hrs, not much different than today. In 5-10 billion years, a year will be a day shorter.


The moon has the same effect on the Earth whether it is day or night. One of the most ramifications of not having the moon as a companion would be changes in the tides. There would still be tides because of the Sun's influence, but they would only be about 1/3 as high as today's tides, and  without the moon, the range between high tide and low tide would be fairly constant throughout the year. The tidal range is affected by the moon's phases. Lower tides would shrink the intertidal beach zone, which is usually teeming with life. The narrower intertidal zone would make it more difficult for the species living there to maintain their niche, and diversity would be diminished.


Another consequence of a moonless Earth would be a faster rotation rate. Without the moon’s constant tugging, Earth would spin more rapidly than it does now. The length of a day would be considerably shorter. Our moon is much bigger in comparison to its parent planet than is any other satellite in our solar system (it's not the largest satellite though, Ganymede and Callisto, which orbit Jupiter and Titan, which orbits Saturn, are larger). The relatively large size and mass of the moon exerts a considerable gravitational effect on the Earth, so that the Earth rotates once every 24 hours.


Without the moon, the Sun would only be up for several hours a day in the mid latitudes, depending upon the season. The primary weather effect of a faster spinning Earth would be higher winds in the atmosphere and on the surface. Winds arise as a result of the planet's rotation and differential heating and cooling of air, land and water. On a moonless Earth, winds would be stronger and always move in the direction that the Earth rotates. On Earth today, the winds in the upper atmosphere (at the mid latitudes) move west to east, but sometimes air flow takes on a north to south or a south to north trajectory. On an Earth with no moon, surface winds would be stronger and more persistent than they are today. The increased windspeeds would generate greater ocean waves.


The moon is gradually drifting away from the Earth due to an ever-widening orbit of 1.6 inches a year. The Sun attracts the moon twice as strongly as does the Earth, and millions of years from now the moon may orbit the Sun between Venus and Earth. Does the moon affect weather now? Back in the 1970s I had noticed that the biggest tides happened at around the same times as the extreme weather events. The 13th of December this year has been a good example. That was the day of the biggest tides of the month and also the day the moon was closest to Earth since 1993. It won't be as close again until 2016. The 13th was also the day of full moon and northernmost point for December(northern declination). Unusual things happen on summer full moon days. In Ashburton the wind swung around to briefly come from due north at 1pm, when the moon was exactly on the opposite side of the earth to NZ. Christchurch received the highest barometric reading so far this month on 1014mbs. On the 13th, Sydney had a drenching of 38mm of rain. Their maximum briefly shot to 32C and reversed the next day to 27C. Brisbane registered the hottest day of the month so far. Canberra received a whopping 52mm. Perth, which received rain the day before, and the hottest temperature so far of the month, 38C, a day later. Police call-outs in NZ were a record high on the weekend of 14th/15th. Rome was flooded. Storms lashed the UK. In Michigan, USA, 8 inches of snow fell on the morning of December 14th which continued into the early morning of December 15th.  The temperature then plummeted from 2C to -14C degrees in about three hours which turned all highways into skating rinks.  Schools were cancelled across the entire Upper Peninsula of Michigan. 


Perhaps the above were all coincidences. Coincidence is only high unexplained correlation, and does not disprove anything. It is a subjective expression of doubt but could just as easily be a statement of cause and effect. One can only imagine the effects of a far closer moon a few million years ago. As time wears on and the moon moves further away from earth, moon influence on earth's rotation will presumably diminish. With earth's regulator no longer there perhaps more extreme weather will ensue from a wilder sea and air, or more extreme seasons due to a greater earth tilt, meaning volcanoes may increase and true global warming may begin. But this is 13 billion years away, and we will be long gone.

Predict Weather 2009 ©