Issuu on Google+

The moon

By: Zack Ellis and Michael Golden In this magazine I will be telling you who the first people to the moon were and I will be filling your young minds with lots and lots of interesting facts about the moon…… How the moon was formed Several mechanisms have been proposed for the Moon's formation 4.527 ± 0.010 billion years ago, some 30– 50 million years after the origin of the Solar System. These included the fission of the Moon from the Earth's crust through centrifugal force, which would require too great an initial spin of the Earth, the gravitational capture of a pre-formed Moon, which would require an unfeasibly extended atmosphere of the Earth to dissipate the energy of the passing Moon, and the co-formation of the Earth and the Moon together in the primordial accretion disk, which does not explain the depletion of metallic iron in the Moon. These hypotheses also cannot account for the high angular momentum of the Earth–Moon system.


The moon The prevailing hypothesis today is that the Earth–Moon system formed as a result of a giant impact: a Mars-sized body hitting the newly formed proto-Earth, blasting material into orbit around it, which accreted to form the Moon. Giant impacts are thought to have been common in the early Solar System. Computer simulations modeling a giant impact are consistent with measurements of the angular momentum of the Earth–Moon system, and the small size of the lunar core; they also show that most of the Moon came from the impact, not from the proto-Earth. More recent tests suggest more of the Moon coalesced from the Earth and not the impact. Meteorites show that other inner Solar System bodies such as Mars and Vesta have very different oxygen and tungsten isotopic compositions to the Earth, while the Earth and Moon have near-identical isotopic compositions. Post-impact mixing of the vaporized material between the forming Earth and Moon could have equalized their isotopic compositions, although this is debated. The large amount of energy released in the giant impact event and the subsequent recreation of material in Earth orbit would have melted the outer shell of the Earth, forming a magma ocean. The newly formed Moon would also have had its own lunar magma ocean; estimates for its depth range from about 500 km to the entire radius of the Moon.

1

The distance from the earth to the moon The average distance between the Moon and the Earth is 384,403 kilometers (238,857 miles). This distance fluctuates between 363,104 kilometers and 405,696 kilometers (225,622 to 252,088 miles) due to the eccentricity of the Moon's orbit. Other sources may list a perigee of 356,375 to 356,567 km and an apogee of 406,660 to 406,720 km.


The moon Due to tidal friction, the moon recedes at a rate of roughly 3.8 cm (1.5 inches) per year, though when there was only one continent the recession rate was less.

The size of the moon is 10,921 km

The moons Elemental composition Elements known to be present on the lunar surface include, among others, oxygen (O), silicon (Si), iron (Fe), magnesium (Mg), calcium (Ca), aluminum (Al), manganese (Mn) and titanium (Ti). Among the more abundant are oxygen, iron and silicon. The oxygen content is estimated at 45%. Carbon (C) and nitrogen (N) appear to be present only in trace quantities from deposition by solar wind.

Phases of the moon

Although this cycle is a continuous process, there are eight distinct, traditionally recognized stages, called phases. The phases designate both the degree to which the Moon is illuminated and the geometric appearance of the illuminated part. These phases of the Moon, in the sequence of their occurrence (starting from New Moon), are listed below

(1) New Moon - When the Moon is roughly in the same direction as the Sun, its illuminated half is facing away from the Earth, and therefore the part that faces us is all dark: we have the new moon. When in this phase, the Moon and the Sun rise and set at about the same time. (2) Waxing Crescent Moon - As the Moon moves around the Earth, we get to see more and more of the illuminated half, and we say the Moon is waxing. At first we get a sliver of it, which grows


The moon as days go by. This phase is called the crescent moon. (3) Quarter Moon - A week after the new moon, when the Moon has completed about a quarter of its turn around the Earth, we can see half of the illuminated part; that is, a quarter of the Moon. This is the first quarter phase. (4) Waxing Gibbous Moon - During the next week, we keep seeing more and more of the illuminated part of the Moon, and it is now called waxing gibbous (gibbous means "humped"). (5) Full Moon - Two weeks after the new moon, the moon is now halfway through its revolution, and now the illuminated half coincides with the one facing the Earth, so that we can see a full disk: we have a full moon. As mentioned above, at this time the Moon rises at the time the Sun sets, and it sets when the Sun rises. If the Moon happens to align exactly with the Earth and Sun, then we get a lunar eclipse. (6) Waning Gibbous Moon - From now on, until it becomes new again, the illuminated part of the Moon that we can see decreases, and we say it's waning. The first week after full, it is called waning gibbous. (7) Last Quarter Moon - Three weeks after new, we again can see half of the illuminated part. This is usually called last quarter. (8) Waning Crescent Moon - Finally, during the fourth week, the Moon is reduced to a thin sliver from us, sometimes called waning crescent. A while after four weeks (29.5 days, more precisely) the illuminated half of the Moon again faces away from us, and we come back to the beginning of the cycle: a new moon. Sometimes, when the Moon is almost new, it is possible to dimly see its darkened disk. The light from the Sun cannot reach this part of the Moon directly; but at this time the Earth (as viewed from the Moon) is at its full and very bright, and what we see is light reflected from the Earth, that then bounces back at us from the Moon. It's a long trip for this light: from the Sun to the Earth, to the Moon, and back to the Earth. 3

the moon’s orbit is The Earth's Moon is the fifth largest in the whole solar system, and is bigger than the planet Pluto. The Moon has a nearly circular orbit (e=0.05) which is tilted about 5° to the plane of the Earth's orbit. Its average distance from the Earth is 384,400 km. The combination of the


The moon Moon's size and its distance from the Earth causes the Moon to appear the same size in the sky as the Sun, which is one reason we can have total solar eclipses.

It takes the Moon 27.322 days to go around the Earth once. Because of this motion, the Moon appears to move about 13° against the stars each day, or about one-half degree per hour. If you watch the Moon over the course of several hours one night, you will notice that its position among the stars will change by a few degrees. The changing position of the Moon with respect to the Sun leads to lunar phases. Have you ever heard the term the 'far-side' of the Moon? Because of the effect on the Moon of tidal forces due to the Earth, the same side of the moon always faces the Earth. In other words, it takes the Moon the same amount of time to rotate around once as it does for the Moon to go around the Earth once. Therefore, Earth-bound observers can never see the 'far-side' of the Moon.

The moon affects the earth in many ways and here is some of the ways it affects the earth.

The angular diameters of the Moon and the Sun as seen from Earth overlap in their variation, so that both total and annular solar eclipses are possible. In a total eclipse, the Moon completely covers the disc of the Sun and the solar corona becomes visible to the naked eye. Since the distance between the Moon and the Earth is very slightly increasing over time, the angular diameter of the Moon is decreasing. This means that several million years ago the Moon always completely covered the Sun on solar eclipses so that no annular eclipses occurred. Likewise, in several million years the Moon will no longer cover the Sun completely and no total eclipses will occur. Eclipses happen only if Sun, Earth and Moon are lined up. Solar eclipses can only occur at new moon; lunar eclipses can only occur at full moon. The Moon is most clear at night, but can sometimes be seen during the day. The Moon (and also the Sun) appear larger when close to the horizon. This is a purely psychological effect. The angular diameter of the Moon from Earth is about one half of one degree. During the brightest full moons, the Moon can have an apparent magnitude (the amount of light received from the object) of about −12.6. For comparison, the Sun has an apparent magnitude of −26.8. For any location on Earth, the highest altitude of the Moon on a day varies between the same limits as the Sun, and depends on season and lunar phase. For example, in winter the Moon comes highest when it is full, and the full moon comes highest in winter. Like the Sun, the Moon can also give rise to an optical effect known as a halo (an optical phenomenon that appears near or around a light source).


The moon The event known as a blue moon is related to the western calendar system. A blue moon is the second of two full moons to occur in the same calendar month. Blue moons occur infrequently (thus the saying once in a blue moon to denote a rare event), because the length of the calendar month in this system is close to the length of the period of the moon's phases. They are not impossible, because every month except February is longer than this period by 1 or 2 days. Blue moons occur every 2.72 years. The next blue moons will be on June 30, 2007; and December 31, 2009.* *Visibly blue moons are rare events. They can be caused by smoke or dust particles in the atmosphere, such as happened after forest fires in Sweden in 1950 and Canada in 1951 and, notably, after the eruption of Krakatoa in 1883, which caused blue moons for nearly two years.

Missions to the moon - Time line


4TH / MOON / GOLDEN / ELLIS