Saturday, May 17, 2008
More About the Moon
The moon has always held a significant place in human culture. The earliest men and women were aware of its waxing and waning. This second brightest object in the sky (next to the sun) shows up in every culture’s mythology. The Romans called it “Luna;” the Greeks called it “Selene.” In more recent time, we have studied the moon intently. Here are some facts about the moon that I find interesting. They may or may not be new to you.
The moon is the only natural satellite of Earth. It orbits our planet from a distance of 384,400 km. It is 3476 km in diameter (compared with ?# of earth – so it’s nealry –fraction—Earth’s size). Its weight is calculated to be 7.35e22 kg (compare with earth).
The moon orbits around the earth in cycles of 709 hours (29.5 days). We see the moon in different phases because as it makes this orbit, its location in relationship to the sun and the earth changes.
Our ocean’s tides are caused by the gravitational forces between the moon and the Earth (like magnets – the moon tries to pull at the earth – everything on earth resists except water, which is always moving). The side of the Earth that is closer to the moon will feel its gravitational attraction more strongly. Because the earth’s rotation is so much faster than the rate at which the moon moves in orbit, we have two high tides each day. – 12 hours and 25 minutes apart.
The same side of the moon is always visible from Earth (to varying degrees, depending on the angle of the sun). This is because the moon is locked into orbit with the Earth. The far side of it was (pretty much) unknown until the Soviet spacecraft Luna photographed it in 1959. Even though we can’t view this “dark” side of the moon from Earth, it does get just as much sunlight as the side we see.
The crust of the moon averages about 68 km in thickness. Under the crust is a mantle and small core (like the Earth’s composition) but the core of the moon, unlike the earth, is inactive.
The moon has two different types of terrain, cratered and smooth. Most of the craters have been named for renowned scientists, such as Copernicus.
Most rocks on the surface of the Moon seem to be between 4.6 and 3 billion years old. The oldest rocks on earth appear to be only 3 billion years old.
The latest theory of the origin of the moon is that the Earth collided with a very large object and that the moon was formed from ejected material. This is known as the Impact Theory.
The revolution of the Moon around the Earth makes the Moon appear as if it is changing shape in the sky. This is caused by the different angles from which we see the bright part of the Moon's surface. These are called "phases" of the Moon. Of course, the Moon doesn't generate any light itself; it just reflects the light of the Sun. The Moon passes through four major shapes during a cycle that repeats itself every 29.5 days. The phases always follow one another in the same order.
What you see when you look at the moon depends on its location in relationship to the sun and Earth. We see a different fraction of sunlight being reflected from the moon to Earth
Moon & Earth Phase View The four major moon phases are "New" , "1st Quarter" , "Full" and "Last or 3rd Quarter". These phases have to do with the relative positions of the sun, the moon and the earth in the moon's 29 day monthly orbit of the earth.
Moon Phase Descriptions...
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 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.
Full Moon and Lunatic Dogs
By Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
09 January 2001
With little scientific backing, the full Moon has forever been blamed for increased rates of violence, suicide, births and simply driving some people stark raving mad.
Luna, Lunatic, Lunarian
The goddess Luna lent her name to the ancient belief in the power of the Moon to make us mad. Modern studies have associated full Moons with everything from extra insanity to traffic accidents. But the connections have been thin.
Perhaps the most well-founded human relationship to the lunar cycle is the menstrual cycle of many women. Some studies have found weak associations to increased aggression, unintentional poisonings and absenteeism. But other studies have contradicted these findings.
Unquestionably, the Moon is the source of a rich lexicon: Top 10 Luna-Terms
Even animal behavior has long been tied to the lunar cycle. One word: werewolf.
But what about dogs? Is your favorite mutt more likely to take a bite outta someone during a full Moon? The question hasn't exactly been dogging scientists forever, but it does beg for an answer, and now two separate groups of researchers have looked into it.
Problem is, they have two answers: yes and no.
In one study, animal bites were found to have sent twice as many British people to the emergency room during full Moons compared with other days. But the other study, in Australia, found Fido can be pretty beastly on any given day.
Both studies were published in a recent issue of the British Medical Journal.
Bitten in Britain
In England, researchers doggedly examined the records of 1,621 animal bite cases at the emergency room of the Bradford Royal Infirmary, a public hospital. Eleven of the injuries were inflicted by rats, 13 by horses, 56 by cats and the rest by man's best friend.
Here's the real news: Not only are animals twice as dangerous during a full Moon, they seem to warm up their canine teeth (or their homologues) in the days prior.
Next Page: Why dogs are different "down under"
The resulting graph of the activity is a classic bell curve of biting, peaking on the night when lovers are supposed to be swooning, not fending off ferocious flea hotels.
"Altered behavior of the animals, influenced by the full Moon, might be the reason of their increased propensity to bite during the full Moon period," said Chanchal Bhattacharjee, lead author of the study.
But Bhattacharjee and colleagues could not sink their teeth into any solid reasons for the strange behavior, and said more research is needed to confirm the findings.
Another continent, another doggone result
A year's worth of bites.
Aussie pooches on the other hand (which they will still bite) seem to be less affected by calls from above. The study "down under" surveyed all public hospital emergency rooms, counting dog bite admissions over a one-year period.
Researchers Simon Chapman and Stephen Morrell of the University of Sydney think they've sniffed out the real truth: No positive relation seems to exist between the full Moon and dog bites, they say.
But how could the results from two studies in two countries be so different? Chapman has what he admits is a somewhat mischievous answer.
Total Diversion ...
Top 10 Luna-Terms
"The only hypothesis that occurs to me is that Britain is such a dull place that when they have full Moons, people get about more," Chapman said. "So there are more opportunities to bite. Australia has perfect weather most of the year, so a full Moon is no big deal."
Chapman and Morrell did find an unexplained peak in attacks centered around New Year's Day. And, for the record, Sunday is the most likely day to meet a raving Rover in Australia. Wednesday, on the other hand, appears to be the safest day to pat the head of a hound.
Top 10 Cool Moon Facts
posted: 30 June 2005
Making of the Moon
The Moon was created when a rock the size of Mars slammed into Earth, shortly after the solar system began forming about 4.5 billion years ago, according to the leading theory.
Locked in orbit
Perhaps the coolest thing about the Moon is that it always shows us the same face. Since both the Earth and Moon are rotating and orbiting, how can this be?
Long ago, the Earth's gravitational effects slowed the Moon's rotation about its axis. Once the Moon's rotation slowed enough to match its orbital period (the time it takes the Moon to go around Earth) the effect stabilized. Many of the moons around other planets behave similarly.
What about phases? Here's how they work: As the Moon orbits Earth, it spends part of its time between us and the Sun, and the lighted half faces away from us. This is called a new Moon. (So there's no such thing as a "dark side of the Moon," just a side that we never see.)
As the Moon swings around on its orbit, a thin sliver of reflected sunlight is seen on Earth as a crescent Moon. Once the Moon is opposite the Sun, it becomes fully lit from our view -- a full Moon.
More than 400 trees on Earth came from the Moon. Well, okay: They came from lunar orbit. Okay, the truth: In 1971, Apollo 14 astronaut Stuart Roosa took a bunch of seeds with him and, while Alan Shepard and Edgar Mitchell were busy sauntering around on the surface, Roosa guarded his seeds.
Later, the seeds were germinated on Earth, planted at various sites around the country, and came to be called the Moon trees. Most of them are doing just fine
The Moon's heavily cratered surface is the result of intense pummeling by space rocks between 4.1 billion and 3.8 billion years ago.
The scars of this war, seen as craters, have not eroded much for two main reasons: The Moon is not geologically very active, so earthquakes, volcanoes and mountain-building don't destroy the landscape as they do on Earth; and with virtually no atmosphere there is no wind or rain, so very little surface erosion occurs.
The Moon is Earth's only natural satellite. Right? Maybe not. In 1999, scientists found that a 3-mile- (5-kilometer-) wide asteroid may be caught in Earth's gravitational grip, thereby becoming a satellite of our planet.
Cruithne, as it is called, takes 770 years to complete a horseshoe-shaped orbit around Earth, the scientists say, and it will remain in a suspended state around Earth for at least 5,000 years.
Top 10 Cool Moon Facts
posted: 30 June 2005
The Moon is not round (or spherical). Instead, it's shaped like an egg. If you go outside and look up, one of the small ends is pointing right at you. And the Moon's center of mass is not at the geometric center of the satellite; it's about 1.2 miles (2 kilometers) off-center.
Apollo astronauts used seismometers during their visits to the Moon and discovered that the gray orb isn't a totally dead place, geologically speaking. Small moonquakes, originating several miles (kilometers) below the surface, are thought to be caused by the gravitational pull of Earth. Sometimes tiny fractures appear at the surface, and gas escapes.
Scientists say they think the Moon probably has a core that is hot and perhaps partially molten, as is Earth's core. But data from NASA's Lunar Prospector spacecraft showed in 1999 that the Moon's core is small -- probably between 2 percent and 4 percent of its mass. This is tiny compared with Earth, in which the iron core makes up about 30 percent of the planet's mass.
The Moon is a planet?
Our Moon is bigger than Pluto. And at roughly one-fourth the diameter of Earth, some scientists think the Moon is more like a planet. They refer to the Earth-Moon system as a "double planet." Pluto and its moon Charon are also called a double-planet system by some.
Tides on Earth are caused mostly by the Moon (the Sun has a smaller effect). Here's how it works:
The Moon's gravity pulls on Earth's oceans. High tide aligns with the Moon as Earth spins underneath. Another high tide occurs on the opposite side of the planet because gravity pulls Earth toward the Moon more than it pulls the water.
At full Moon and new Moon, the Sun, Earth and Moon are lined up, producing the higher than normal tides (called spring tides, for the way they spring up). When the Moon is at first or last quarter, smaller neap tides form. The Moon's 29.5-day orbit around Earth is not quite circular. When the Moon is closest to Earth (called its perigee), spring tides are even higher, and they're called perigean spring tides.
All this tugging has another interesting effect: Some of Earth's rotational energy is stolen by the Moon, causing our planet to slow down by about 1.5 milliseconds every century.
Bye bye Moon
As you read this, the Moon is moving away from us. Each year, the Moon steals some of Earth's rotational energy, and uses it to propel itself about 3.8 centimeters higher in its orbit. Researchers say that when it formed, the Moon was about 14,000 miles (22,530 kilometers) from Earth. It's now more than 280,000 miles, or 450,000 kilometers away.
By Kezia Bacon-Bernstein, Correspondent
Kezia Bacon-Bernstein's articles appear courtesy of the North and South Rivers Watershed Association, a local non-profit organization devoted to the preservation, restoration, maintenance and conservation of the North and South Rivers and their watershed. For membership information and a copy of their latest newsletter, contact NSRWA at (781) 659-8168.