Earth’s Gravitational Attraction to the Moon and the Resulting Tides The revolution and rotation of the Moon are well understood and there is little debate as to their mechanisms in the present day. However, it is g enerally unknown to the public that the Moon is responsible for the curr ent length of our day. Research in the early part of the 20 th century found that the Moon was much closer in the past and is getting farther everyday (Street, 1917). More current investigations found the Moon to have a drag effect on the Earth, causing our days to go from 18 hours long to the current 24 hours. While the Moon orbits the Earth, it will continue to lengthen our days (Brosche, 1984). There is also evidence that if it were not for the Moon, the Earth’s tilt would be much more variable (one model suggests it would change from eleven to forty degrees) (Peterson, 1993). This would have had a tremendous impact f or life on Earth. With the Earth’s tilt varying, the Earth’s climate would be much more erratic, making it difficult for more complex life forms to develop. The biggest influence that the Moon has on the Earth on a daily basis is the tides. This interaction has been understood on a gross scale according to Newton’s laws for a very long time (Schneider, 1880). The Sun also plays a role in the Earth’s tides. Although the Sun is much larger than t he Moon, it is also much f urther away. The importance of distance becomes obvious when you examine N ewton’s law of univer sal gravitation. The strength of gravity decreases with the square of the distance proportional to the product of the two masses. A more sophisticated description of how the Moon influences the tides involves a gravitational gradient. (Trujillo, Thurman, Essentials of Oceanography, Pearson Prentice Hall, 2005) Because the Moon is much closer the gravitational gradient between the far and near side of the moon is more s ignificant than the gradient between the near and far side of the sun. This results in the lunar force being inversely proportional to the cube of the distance, thereby causing the Moon to have a greater influence on the tides on Earth. The Sun’s influence is felt as constructi ve or destructive to the Moon’s influence based on the geometrical relationship between the forces of the Earth, Moon, Sun system. When the geometrical relationship is parallel, as in the Full Moon and New Moon, the forces are additative and the Earth has the highest tides. When
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Earth’s Gravitational Attraction to the Moon and the Resulting Tides
The revolution and rotation of the Moon are well understood and there is little debate as
to their mechanisms in the present day. However, it is generally unknown to the public
that the Moon is responsible for the current length of our day. Research in the early part
of the 20th
century found that the Moon was much closer in the past and is getting farther
everyday (Street, 1917). More current investigations found the Moon to have a drag
effect on the Earth, causing our days to go from 18 hours long to the current 24 hours.
While the Moon orbits the Earth, it will continue to lengthen our days (Brosche, 1984).
There is also evidence that if it were not for the Moon, the Earth’s tilt would be much
more variable (one model suggests it would change from eleven to forty degrees)
(Peterson, 1993). This would have had a tremendous impact for life on Earth. With the
Earth’s tilt varying, the Earth’s climate would be much more erratic, making it difficult
for more complex life forms to develop.
The biggest influence that the Moon has on the Earth on a daily basis is the tides. This
interaction has been understood on a gross scale according to Newton’s laws for a very
long time (Schneider, 1880). The Sun also plays a role in the Earth’s tides. Although the
Sun is much larger than the Moon, it is also much further away. The importance ofdistance becomes obvious when you examine Newton’s law of universal gravitation. The
strength of gravity decreases with the square of the distance proportional to the product of
the two masses. A more sophisticated description of how the Moon influences the tides
involves a gravitational gradient. (Trujillo, Thurman, Essentials of Oceanography,
Pearson Prentice Hall, 2005) Because the Moon is much closer the gravitational gradient
between the far and near side of the moon is more significant than the gradient between
the near and far side of the sun. This results in the lunar force being inversely
proportional to the cube of the distance, thereby causing the Moon to have a greater
influence on the tides on Earth. The Sun’s influence is felt as constructive or destructive
to the Moon’s influence based on the geometrical relationship between the forces of the
Earth, Moon, Sun system. When the geometrical relationship is parallel, as in the Full
Moon and New Moon, the forces are additative and the Earth has the highest tides. When