The moon has had a significant role in life on earth. The most obvious is that it serves as a calendar for planting and other agricultural activities as it goes through it's phases during the 29-day cycle. Aside from that, the gravity moon no doubt helps to keep the rotation of the earth more stable than it would be otherwise. Also, I have speculated in the posting "The Moon And Earth's Magnetic Field" on my physics and astronomy blog, www.markmeekphysics.blogspot.com , that the moon's gravity strengthens the magnetic field of the earth by churning it's iron core, thus helping to protect us from charged particles from space.
No planet, other than Pluto, has a moon so large in ratio to the planet as the earth and the moon. I think that I established in the posting "The Earth, The Moon And, The Sun", on the physics and astronomy blog, that the moon does not actually orbit the earth. Rather, the paths of the two interweave while both orbit the sun. This means that the moon really isn't even a moon, the earth and the moon are actually double planets.
My reason for coming to this conclusion is that from the moon, the gravity of the sun is more than twice as strong as that of the earth, so how could the moon orbit the earth, rather than the sun? "The Continental Asteroid Hypothesis" on my geology blog, www.markmeekearth.blogspot.com , gives my explanation for the origin of the moon.
I do not see why there should be surprise about the recent findings that indicate the presence of both ice and metals on the moon. If meteors and comets can strike the earth, then they can land on the moon also.
The question about water on the moon is not whether there was ever water there, a comet or a portion of one could have easily deposited ice on the moon. The question is whether the weak gravity of the moon, about one-sixth that of earth, could retain water. The answer for liquid water would be no, but ice or underground water from the impact of a comet could definitely still be present today, especially in the polar regions of the moon which are out of direct sunlight.
There have been very many meteorite impacts on earth ( It is a meteor before it lands, and a meteorite after it lands). But the impact craters are gradually erased by erosion. Also, since the surface of the earth is about 72% water we can assume that percentage of impacts have occurred there. Minerals on earth, such as metals, came from meteorite impacts and the water on earth seems virtually certain to have come from the impacts of one or more comets, which are basically collections of ice.
The same side of the moon always faces earth. This near side has the "seas" that we can see, but which are actually volcanic lava (See "The Lunar Balance Hypothesis" on my physics and astronomy blog for my explanation). However, the far side of the moon has many more craters than the near side.
The obvious reason is the presence of the earth, many meteors that would have hit the near side of the moon hit the earth instead. This gives us a good idea of how many meteors have hit the earth, but whose craters have since been erased by erosion or which have landed in the oceans.
The giant planet Jupiter serves as an excellent protective shield for the earth. In the past twenty years, two major comets have struck Jupiter, producing spectacular fireworks, that might have struck the earth. But there is a down side to Jupiter's position, it's powerful gravity prevents the asteroid belt from coalescing into a planet (See "The Mars Gap Hypothesis" on my physics and astronomy blog).
The gravity of Jupiter also destabilizes the orbits of these asteroids around the sun and causes them to fall inward. I am sure that the two small moons of Mars, Phobos and Deimos, are asteroids whose orbits were destabilized and which drifted toward Mars until they were captured by it's gravity. Many of these asteroids whose orbits were destabilized end up striking the earth or the moon.
One such impact, on what is now Mexico's Yucutan Peninsula, resulted in the extinction of the dinosaurs, about 65 million years ago. Clearly these impacts can have a tremendous effect on the earth's environment. There was the impact of what was most likely a small comet in 1908 in Siberia which felled vast number of trees (You can see "Tunguska Event" on www.wikipedia.org, if you wish).
I think that I established in "The Lunar Shield Zone Hypothesis" on my geology blog, www.markmeekearth.blogspot.com , that the earth would be richer in metals if not for the presence of the moon, because meteors carrying metals have struck the moon instead of the earth. But the question that I would like to ask today is whether there would be higher forms of life on earth at all without the moon to shield the earth. The shock waves of frequent asteroid impacts in water could wipe out most forms of life there and the extinction of the dinosaurs has clearly shown that such impacts can also wipe out life on land.
We know that the moon was once much closer to the earth than it is now, possibly only one-fifth as distant. The moon gradually moves further away due to the tidal bulge that it's gravity creates in the earth's oceans. Since the earth is rotating, this pulls the tidal bulge continuously forward and this imparts orbital energy to the moon, pulling it into a higher orbit.
The force that creates these tides is not simply gravity, but rather a difference in gravity. As the moon is overhead, the water at the surface of the ocean is closer to the moon than the water at the bottom of the ocean. Thus, there is more gravitational pull at the surface so that water is pulled upward by the moon's gravity.
If the moon can produce the tides in the earth's oceans that it does today, just imagine what the tides must have been like if the moon was only one-fifth as distant from earth. It's gravitational force on the oceans would have been 125 times as great.
This is because first, the gravitational pull is inversely proportional to the square of the distance. Also, with the moon at only one-fifth the distance from earth, the difference in distance between the surface and bottom of the ocean would be five times as great relative to the distance to the moon. So 5 squared is 25, and then that multiplied by 5 gives us 125. The tidal force can thus be said to operate by an inverse cube law, just as gravity operates by the inverse square law.
The influence of tides on the earth was also greater in those days of long-ago because it is known that the earth was rotating faster, so that days were shorter, than it is now. It is actually this same tidal force which has slowed the earth's rotation.
The earth must have been a far more amphibious world then than it is now. Coastlines were much less well-defined. There were wide tidal zones, maybe several kilometers wide, between the lines of high and low tides. There would be many permanent tidal pools in areas near the coast. The tides would have had much more impact on shorelines than they do today.
Now, here is something that I cannot see has been referred to previously. We know that life began in the oceans, and later moved onto land. The tremendous tides of the distant past must have been an important factor in bringing life from the sea onto land. Living things were continuously washed onto land by the extreme tides.
I am still certain that this would have required God's design, as I described on my creation blog, http://www.markmeekcreation.blogspot.com/ . It was necessary for life to get started in water because the fragile early forms of life required protection from UV. But the requirements for breathing, mobility, structural support and, reproduction are completely different on land than in water.
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