Dark Side of the Moon + 2012 + Start of Spring
Part 1:
So, is the other side of the moon really dark?
The answer is no!
Bad Astronomy: The Moon only shows one face to us because it is not rotating.
Better astronomy: The Moon only shows one face because it is rotating, once every time it revolves around the Earth.
Best astronomy: The Moon does not appear to rotate in the reference frame where the Earth-Moon line is fixed in direction, but it does rotate as seen by an outside observer.
If you go out on several different nights and look at the Moon, you will always see the same features, at about the same position. It looks as if the Moon doesn't rotate! Ah, but it does. This can be seen using a model. Grab two oranges (or apples, or baseballs, or whatever roughly spherical objects you have handy). Mark one with an "X"; this represents a feature on the Moon. Now put the other one down on a table; this is the Earth. Place the Moon model on the table about 30 centimeters (one foot) away with the X facing the Earth model. Now move the Moon model as if it were orbiting the Earth, taking care to make sure that the X faces the Earth model at all times.
Surprise! You'll see that to keep the X facing the Earth model, you have to rotate the Moon model as it goes around the Earth model. Furthermore, you can see you have to spin it exactly once every orbit to keep the X facing the Earth model. If you don't rotate it, the Moon model will show all of its "sides" to the Earth model as it goes around.
Now, I have been a bit tricky here. We are talking about two different frames of reference; one on the surface of the Earth looking out at the Moon, and one outside the Earth-Moon system looking in. You performed the experiment from the latter frame, and saw the Moon rotating. From the former, however, you can see for yourself the Moon does not rotate. What is being argued here is that in one frame the Moon rotates, in another it does not.
We've actually learned three things:
1) the Moon rotates as it orbits the Earth (as seen by an outside observer);
2) it rotates one time for every orbit (to that observer); and
3) if it didn't rotate, we would eventually see all of the Moon as it orbited the Earth.
There is a bit more to this story. We actually can see a bit more than just the one face of the Moon. Because the Moon's orbit is not a perfect circle but actually an ellipse, its spin and rotation don't exactly match up. This means that sometimes the spin lags behind the orbital speed, and sometimes it moves ahead. This in turn means that sometimes we can "peek" around a bit onto the far side of the Moon. This is called "libration". You can see it yourself! If you happen to observe the Moon a week after perigee (closest point to the Earth) and then two weeks later, a week after apogee (farthest point from the Earth) you can see that the face looks like it has rotated a bit. This is easiest to see with binoculars or a small telescope. It's very hard to see with the naked eye, but remember, ancient astronomers knew about this effect long before the invention of the telescope! - BA
Part 2:
So, will the world end at 2012?
The Mesoamerican Long Count calendar is a non-repeating, vigesimal and base-18 calendar used by several Pre-Columbian Mesoamerican cultures, most notably the Maya. For this reason, it is sometimes known as the Maya (or Mayan) Long Count calendar. Using a modified vigesimal tally, the Long Count calendar identifies a day by counting the number of days passed since a mythical creation date that corresponds to August 11, 3114 BCE in the Gregorian calendar. The Long Count calendar was widely used on monuments.
To actualy calculate the calendar, there are many events after 2012, so it's actually false that the world will end.
Dec. 21, 2012, won't be the end of the world as we know. It will, however, be another winter solstice.
Much like Y2K, 2012 has been analyzed and the science of the end of the Earth thoroughly studied. Contrary to some of the common beliefs out there, the science behind the end of the world quickly unravels when pinned down to the 2012 timeline. Below, NASA Scientists answer several questions that we're frequently asked regarding 2012.
Question (Q): Are there any threats to the Earth in 2012? Many Internet websites say the world will end in December 2012.
Answer (A): Nothing bad will happen to the Earth in 2012. Our planet has been getting along just fine for more than 4 billion years, and credible scientists worldwide know of no threat associated with 2012.
Q: What is the origin of the prediction that the world will end in 2012?
A: The story started with claims that Nibiru, a supposed planet discovered by the Sumerians, is headed toward Earth. This catastrophe was initially predicted for May 2003, but when nothing happened the doomsday date was moved forward to December 2012. Then these two fables were linked to the end of one of the cycles in the ancient Mayan calendar at the winter solstice in 2012 -- hence the predicted doomsday date of December 21, 2012.
Q: Does the Mayan calendar end in December 2012?
A: Just as the calendar you have on your kitchen wall does not cease to exist after December 31, the Mayan calendar does not cease to exist on December 21, 2012. This date is the end of the Mayan long-count period but then -- just as your calendar begins again on January 1 -- another long-count period begins for the Mayan calendar.
Q: Could a phenomena occur where planets align in a way that impacts Earth?
A: There are no planetary alignments in the next few decades, Earth will not cross the galactic plane in 2012, and even if these alignments were to occur, their effects on the Earth would be negligible. Each December the Earth and sun align with the approximate center of the Milky Way Galaxy but that is an annual event of no consequence.
Q: Is there a planet or brown dwarf called Nibiru or Planet X or Eris that is approaching the Earth and threatening our planet with widespread destruction?
A: Nibiru and other stories about wayward planets are an Internet hoax. There is no factual basis for these claims. If Nibiru or Planet X were real and headed for an encounter with the Earth in 2012, astronomers would have been tracking it for at least the past decade, and it would be visible by now to the naked eye. Obviously, it does not exist. Eris is real, but it is a dwarf planet similar to Pluto that will remain in the outer solar system; the closest it can come to Earth is about 4 billion miles.
Q: What is the polar shift theory? Is it true that the earth’s crust does a 180-degree rotation around the core in a matter of days if not hours?
A: A reversal in the rotation of Earth is impossible. There are slow movements of the continents (for example Antarctica was near the equator hundreds of millions of years ago), but that is irrelevant to claims of reversal of the rotational poles. However, many of the disaster websites pull a bait-and-shift to fool people. They claim a relationship between the rotation and the magnetic polarity of Earth, which does change irregularly, with a magnetic reversal taking place every 400,000 years on average. As far as we know, such a magnetic reversal doesn’t cause any harm to life on Earth. A magnetic reversal is very unlikely to happen in the next few millennia, anyway.
A: The Earth has always been subject to impacts by comets and asteroids, although big hits are very rare. The last big impact was 65 million years ago, and that led to the extinction of the dinosaurs. Today NASA astronomers are carrying out a survey called the Spaceguard Survey to find any large near-Earth asteroids long before they hit. We have already determined that there are no threatening asteroids as large as the one that killed the dinosaurs.
Q: How do NASA scientists feel about claims of pending doomsday?
A: For any claims of disaster or dramatic changes in 2012, where is the science? Where is the evidence? There is none, and for all the fictional assertions, whether they are made in books, movies, documentaries or over the Internet, we cannot change that simple fact. There is no credible evidence for any of the assertions made in support of unusual events taking place in December 2012.
Q: Is there a danger from giant solar storms predicted for 2012?
A: Solar activity has a regular cycle, with peaks approximately every 11 years. Near these activity peaks, solar flares can cause some interruption of satellite communications, although engineers are learning how to build electronics that are protected against most solar storms. But there is no special risk associated with 2012. The next solar maximum will occur in the 2012-2014 time frame and is predicted to be an average solar cycle, no different than previous cycles throughout history.
All the Questions and Answers above are from NASA.
Science Myth of the Week:
So, when does spring start?
Spring only starts on March 21st 36 times every 100 years. Sometimes it's March 20th, and it can even go to March 19th!
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