The Size of It – Despite the exaggerated size of the Moon in movies, books, and art, the Moon's apparent size is relatively small in the sky. Most other animal behaviors relating to the Moon are because the tides change the coastal environment. Corals time their mating events by the light of the Moon. Studies have documented changes in the success rates of predators and foraging patterns of prey animals due to this added nighttime illumination. While careful statistical studies have shown no correlation between the full Moon and strange behavior, the full Moon's light does make it easier for humans and other animals to see - and be seen. It "shines" because it reflects the Sun's light. Shining Light – Just like the planets, our Moon does not produce its own light. These minerals may have been essential for life to evolve as quickly as it did. The tides eroded the coastal areas, adding minerals to the oceans. Scientists believe that these extreme tides occurred once every three hours because the Earth was spinning more rapidly. Billions of years ago, the Moon was 10 times closer and tides were 1000 times higher. Earth's oceans are pulled toward the Sun, but the difference between Sun's gravitational pull on Earth’s near side and far side is much less the Sun’s gravity contributes only about a third of the tides’ height.Įarly in Earth's history, the Moon was even closer to Earth. The Sun, of course, also exerts a powerful gravitational pull on Earth - that's what keeps Earth in a steady orbit. The Moon's contribution to Earth's tides is significant because it is so close. On the side of Earth opposite the Moon, the gravitational pull is less than on any other part of the Earth and the oceans are "left behind" in another bulge. As the Moon orbits the Earth, it drags along behind it a "bulge" in the oceans. Earth's oceans (and atmosphere), however, are free to lift many feet in response this tug. Ponds and lakes - such as the Great Lakes - experience small tides, as well. Earth's crust rises slightly (several centimeters) due to this force. Tides – The Moon's gravitational pull tugs on Earth - especially the portion that is nearest to the Moon. Without the Moon, the Earth's stately progression through spring, summer, fall, and winter would have fluctuated widely over eons. It keeps Earth’s axis pointed at a consistent angle. The very presence of the Moon helps to keep this tilt relatively stable The Moon's gravitational pull acts like training wheels for Earth on its journey around the Sun. (For more information about seasons, see SkyTellers About Our Seasons.) Stable Seasons – The giant impact that formed the Moon may have tipped the Earth a little and contributed to the 23.5° tilt of our North Pole away from "straight up." This tilt gives us our seasons. (Right) Farside view ofĮarth's Moon as seen by the Clementine spacecraft. (Left): Nearside view of Earth's Moon as seen by the Galileo spacecraft. The side we do not see from Earth (the farside) has been mapped during lunar missions. This means that Earth observers always see the same side of the Moon (the nearside). The Moon takes the same amount of time to spin around once as it does to orbit completely around Earth. Our Moon's day and night cycles are longer than Earth's - the Moon spins on its axis once every 27.3 days. Just like Earth, our Moon rotates on its own axis and experiences daylight and dark cycles. Today’s more distant Moon takes over 27 days to complete one full orbit around Earth. The distance between Earth and Moon increased and the spins of both decreased. Over time, the Moon's gravitational pull on the Earth "stole" some of Earth's spin energy, launching the Moon slowly into higher and higher orbits. Fossil corals from 400 million years were living on an Earth with 22-hour days. Stromatolites living 850 million years ago record a day length that was about 21 hours long. Evidence includes growth rings in fossil corals and shells and ancient photosynthetic bacteria layers, called stromatolites. Length of Day – Early Earth was spinning at a much faster rate: according to computer models, Earth had a six-hour day 4.5 billion years ago! Since then, with the help of our Moon, Earth has been slowing down and our days have been getting longer. (Apollo astronauts were able to leap across the lunar surface because of this weaker pull.) Yet, the Moon's gravitational pull is responsible for Earth's current length of day, stable seasons, and tides. The Moon's gravitational pull is relatively weak compared to Earth's. They shaped each other through the invisible connection of their gravitational pull. Throughout this long history, the Moon has been Earth's companion in space.
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