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| | [[image:Moon2.jpg|right|thumb|350px|The Moon, age 21 days]] | | [[image:Moon2.jpg|right|thumb|350px|The Moon, age 21 days]] |
| | The '''Moon''' is a natural [[satellite]] orbiting the [[Earth]] at an average distance of about 238,000 miles (380,000 km). | | The '''Moon''' is a natural [[satellite]] orbiting the [[Earth]] at an average distance of about 238,000 miles (380,000 km). |
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| | + | ==Design attributes of the Moon== |
| | + | Unlike most planets in the solar system, Earth has only one moon, and it has several striking characteristics: |
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| | + | {| |
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| | + | |1. |
| | + | |The Moon has the same size as the [[Sun]] when viewed from Earth. This creates a situation which permits phenomenal solar eclipses to occur. The odds of this symmetry occurring by chance are very small. |
| | + | |-valign="top" |
| | + | |2. |
| | + | |The Moon presents the same side to Earth at all times. That means that the rotation of the Earth offsets the separate effects of the revolution of the Moon. Secular physicists explain this phenomenon by [[tidal locking]]; tidal forces on Earth caused a bulge on the Moon, thereby creating a drag on the rotation of the Moon until its same face always presents to the Earth. It was once believed that the planet [[Mercury]] had a similar locked rotation due to gravitational forces from the sun, such that the same side of Mercury always faces the sun. In fact, Mercury's tidal locking is incomplete; it does not always present the same face to the sun. |
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| | + | Current tidal forces exerted by the Earth on the Moon cannot account fully for its bulge or egg shape, though accounting for greater tidal forces in the past may explain this discrepancy.<ref>http://physics.fortlewis.edu/Astronomy/astronomy%20today/CHAISSON/AT308/HTML/AT30803.HTM</ref> |
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| | + | |3. |
| | + | |[[Atheistic]] theories of the [[Moon theories|origin]] of the Moon, widely taught for decades, have been proven false.<ref>Planetary Science Institute: [http://www.psi.edu/projects/moon/moon.html The Origin of the Moon]</ref> Lacking any other [[atheistic]] alternatives, some scientists assert that the Moon originated from a collision early in Earth's history which created an orbiting ring of debris from the iron-poor surface of the planet which eventually coalesced into the moon.<ref>http://www.astronomy.com/asy/default.aspx?c=a&id=2198</ref> This theory, however, is contrary to key observations of the Moon, such as the relatively low levels of iron in the moon's crust. Additionally, tests have been suggested, but the results neither supported or disproved the theory.<ref>J. H. Jones: [http://www.lpi.usra.edu/meetings/origin98/pdf/4045.pdf Tests of the Giant Impact Hypothesis]</ref> |
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| | + | Biblical history records the Moon being created on the fourth day of [[Creation Week|creation week]], along with the Sun. |
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| | + | |4. |
| | + | |The Moon currently recedes from the Earth at a rate of 1.5 inches (3.8 cm) per year<ref>NASA [http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html]</ref>. The Moon could never have been closer than about 11,000 miles or it would have been broken up by tidal forces. If the rate of recession stayed constant at 3.8 cm per year, it would take 9.6 billion years for the lunar distance to migrate from 11,000 miles to the present distance of about 240,000 miles. However, the tidal torque between Earth and the Moon would not be constant if the [[continental drift|continents drift]], and it also depends on the distance between the Earth and Moon and other factors, so a simple linear extrapolation is not valid.{{fact}} |
| | + | |} |
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| | + | == Background == |
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| | Although the Moon is often described as revolving around the Earth, this is slightly inaccurate: the Earth and the Moon ''both'' revolve around their ''barycenter'', their common [[centroid|center of mass]]. The combined motion is like an athlete performing an [[Olympics| Olympic]] hammer throw: one object swings in a large circle, the other almost pivots around a fixed point but actually performs a small opposing circle of its own. <ref>The Earth and the Moon orbit each other around a gravitational midpoint called the ''barycenter.'' This point is, however, actually inside the Earth, about 3/4 of its radius from its center. It is not the Earth, but the barycenter of the Earth-Moon system, that orbits the [[Sun]] in a near-perfect ellipse. Relative to this ellipse, Earth is 3,000 miles closer to the Sun at full moon and 3,000 miles further from the Sun at new moon.</ref> | | Although the Moon is often described as revolving around the Earth, this is slightly inaccurate: the Earth and the Moon ''both'' revolve around their ''barycenter'', their common [[centroid|center of mass]]. The combined motion is like an athlete performing an [[Olympics| Olympic]] hammer throw: one object swings in a large circle, the other almost pivots around a fixed point but actually performs a small opposing circle of its own. <ref>The Earth and the Moon orbit each other around a gravitational midpoint called the ''barycenter.'' This point is, however, actually inside the Earth, about 3/4 of its radius from its center. It is not the Earth, but the barycenter of the Earth-Moon system, that orbits the [[Sun]] in a near-perfect ellipse. Relative to this ellipse, Earth is 3,000 miles closer to the Sun at full moon and 3,000 miles further from the Sun at new moon.</ref> |
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| | The months of the [[Islam|Muslim]] [[calendar]] are determined by observations of the [[hilal]], the moment at which the thin crescent moon first becomes visible. This marks the start of a month. Traditionally, and today in [[Pakistan]] and [[Jordan]], hilal is determined by actual observation and can be affected by weather and other factors. When following the traditional method, it is not actually possible to be certain precisely when future months will begin. In most Muslim countries, actual observation has been replaced by [[astronomy}|astronomical]] rules. | | The months of the [[Islam|Muslim]] [[calendar]] are determined by observations of the [[hilal]], the moment at which the thin crescent moon first becomes visible. This marks the start of a month. Traditionally, and today in [[Pakistan]] and [[Jordan]], hilal is determined by actual observation and can be affected by weather and other factors. When following the traditional method, it is not actually possible to be certain precisely when future months will begin. In most Muslim countries, actual observation has been replaced by [[astronomy}|astronomical]] rules. |
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| − | ==Unusual characteristics of the Moon==
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| − | Unlike most planets in the solar system, Earth has only one moon, and it has several striking characteristics:
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| − | {|
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| − | |-valign="top"
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| − | |1.
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| − | |During recent history the Moon has had roughly same size as the [[Sun]] when viewed from Earth. This creates a situation which permits phenomenal solar eclipses to occur. The odds of this symmetry occurring by chance are very small. The symmetry will not last forever.
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| − | |-valign="top"
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| − | |2.
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| − | |The Moon presents the same side to Earth at all times. That means that the rotation of the Earth offsets the separate effects of the revolution of the Moon. Secular physicists explain this phenomenon by [[tidal locking]]; tidal forces on Earth caused a bulge on the Moon, thereby creating a drag on the rotation of the Moon until its same face always presents to the Earth. It was once believed that the planet [[Mercury]] had a similar locked rotation due to gravitational forces from the sun, such that the same side of Mercury always faces the sun. In fact, Mercury's tidal locking is incomplete; it does not always present the same face to the sun.
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| − | Current tidal forces exerted by the Earth on the Moon cannot account fully for its bulge or egg shape, though accounting for greater tidal forces in the past may explain this discrepancy.<ref>http://physics.fortlewis.edu/Astronomy/astronomy%20today/CHAISSON/AT308/HTML/AT30803.HTM</ref>
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| − | |3.
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| − | |There were several [[Moon Theories|theories]] about the origin of the Moon. Most of the older theories had been discarded in the face of observations (for example based on lunar samples).<ref>Planetary Science Institute: [http://www.psi.edu/projects/moon/moon.html The Origin of the Moon]</ref> The theory currently accepted by mainstream scientists is that the Moon originated from a collision early in Earth's history which created an orbiting ring of debris from the iron-poor surface of the planet which eventually coalesced into the moon.<ref>http://www.astronomy.com/asy/default.aspx?c=a&id=2198</ref> This theory explains many things that spoke against the older theories, but others have pointed out that the theory currently doesn't explain all observations of the Moon. Additionally, tests have been suggested, but the results neither supported or disproved the theory.<ref>J. H. Jones: [http://www.lpi.usra.edu/meetings/origin98/pdf/4045.pdf Tests of the Giant Impact Hypothesis]</ref>
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| − | Biblical history records the Moon being created on the fourth day of [[Creation Week|creation week]], along with the Sun.
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| − | |4.
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| − | |The Moon currently recedes from the Earth at a rate of 1.5 inches (3.8 cm) per year<ref>NASA [http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html]</ref>. The Moon could never have been closer than about 11,000 miles or it would have been broken up by tidal forces. If the rate of recession stayed constant at 3.8 cm per year, it would take 9.6 billion years for the lunar distance to migrate from 11,000 miles to the present distance of about 240,000 miles. However, the tidal torque between Earth and the Moon would not be constant if the [[continental drift|continents drift]], and it also depends on the distance between the Earth and Moon and other factors, so a simple linear extrapolation is not valid.{{fact}}
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| | == See also == | | == See also == |