Fw: Eight Myths About the Moon & Four Myths About the Sun

[BCJ]

Eight Myths About the Moon By Bob Grant   Nobody believes it’s made of cheese anymore — hopefully — but plenty of myths about the moon still remain to be skewered.   Just because you believe a few myths about the moon doesn’t mean you’re a lunatic. After all, we all have our favorites.    We revealed the truth behind eight myths about the moon, that calm celestial nightlight that we’ve all gazed upon and wondered about.   We’ll take a look at eight myths about the moon, most of which seem reasonable until examined more closely. It should come as no surprise that myths about the moon are as numerous as hairs on a dog. Perhaps the silliest of the modern crop is the claim that NASA’s moon landings were false. All you have to do to prove that one false and zap one of the laser reflectors our astronauts left behind on the lunar surface.   Astronomers do that all the time — but it’s harder to fight all the other modern myths folks have come to believe about our companion in orbit. They keep trying, though. In this article, we thought we’d give them a little help. Here’s the truth behind eight modern lunar myths.   Myth 1: Blue moons are actually blue.   Come now. While you can’t ever discount the possibility of some external factor like volcanic gasses staining moonlight blue, this myth about the moon is otherwise an impossibility. The moon itself doesn’t change color, any more than the next lunar mission will find limburger in the lunar valleys.   A “blue moon” is simply the common name for a second full moon within a calendar month. It’s a coincidence of human record keeping. A full lunar cycle takes about 29-1/2 days, while most months are 30 or 31 days long. Therefore, it’s inevitable that we’ll have a blue moon every couple of years.   Myth 2: The moon can affect your emotions.   This myth about the moon has been around a long time. The term “lunacy,” derives from the Latin word for the moon, Luna. In modern times, some authorities have lent the idea credence, with the theory being that since the moon causes tides, it can affect the fluids in your body, changing how you feel.   Well, there’s no indication that any such thing can occur, three thousand years of astrology notwithstanding. Hospital personnel and the police often swear that people are wilder and commit more crimes during the full moon, but repeated statistical analyses of their records show no significant correlations.   Myth 3: A lunar month is exactly 28 days long.   This myth about the moon is almost true, but not quite. The moon’s orbital period (that is, the time it takes the moon to complete one revolution around the Earth) is 27-1/3 days, while the average time it takes to go through its phases is 29-1/2 days. That’s why we get a blue moon on occasion.   Now, you might think that the orbital and phase periods would be the same; and they would be, if the Earth-Moon system were sitting dead in the sky. However, we all revolve around the sun too, so it takes the moon about 2-1/6 days longer to get lined back to up in its original phase than it does for it to revolve around the Earth.   Myth 4: There’s no gravity on the moon.   While astronauts on the moon are obviously much lighter than they are back home, they still have to deal with some gravity. It’s only one-sixth of the Earth’s, though. If you weigh 150 pounds on Earth, you’d weigh 25 on the moon. That’s a big difference, which may be why this myth among many myths about the moon is still with us!   Myth 5: The moon doesn’t rotate.   It doesn’t seem to, but the moon does rotate — very, very slowly. A lunar day is exactly as long as a lunar month. Like so many of the moons throughout the solar system, the rotation of the Earth’s moon is tidally locked to its primary. Given the Earth’s much larger bulk, the moon always shows the same face to us.   Therefore, this myth about the moon can’t be true. Think about it. Because of the tidal lock, the moon must gradually rotate as it revolves around the Earth — but only just enough, ironically, not to seem to move at all. (Actually the Earth and the Moon are rotating about a common center, but we won’t get into that here.)   Myth 6: The phases of the moon are caused by Earth’s shadow.   Actually, the only time the Earth’s shadow affects the moon is during a lunar eclipse — which, because of certain details of orbital mechanics, can only occur when the moon is perfect full. For the same reasons, you get solar eclipses only when the moon is new.   In any case, this myth about the moon is mistaken. Phases occur because of the moon’s position in space. When it’s between the Earth and the sun, we see only the dark hemisphere; we call this a new moon. A full moon occurs when the Earth is perfectly centered between the moon and sun.   Any other phase is a function of where the moon happens to be in its rotation around the Earth. A thin crescent means the moon isn’t quite centered between the Earth and sun. One way or the other, a half-moon means its position is at right angles to the Earth-sun line-up. Simple enough, right?   Myth 7: The far side of the moon is always dark.   This myth about the moon is easy to dismiss, given a little thought. The lunar far side gets as much light as the near side — but we never see it, due to the tidal locking. When the moon is full on the far side, it is a new moon to us. The opposite is true when our side is full moon.   Although the tide lock means we can never see all of the lunar far side without spacecraft, we can cheat a little, because the moon wobbles a bit as it moves through the sky. This idea was understood in Galileo’s time, and by using it, astronomers were able to map about 60% of the moon’s surface area.   Myth 8: The moon’s surface is highly reflective.   Oddly enough, it isn’t. The moon reflects an average of only 7% of the sunlight that falls upon it. Given that it’s the brightest thing in the night sky, it’s hard to believe that this myth about the moon is false, but even the brightest parts of the moon’s surface are only about 30% reflective.   Hope you’ve enjoyed this trip to our lunar neighbor, and dispelled a few myths about the moon in the process! ==============================================================================  Throwing Light on a Few Myths About the Sun  By Bob Grant   Even in this modern age, myths about the sun still exist. Here are a few to consider.   As one of the most ubiquitous objects in the lives of nearly everyone who has ever lived, it’s no surprise that myths about the sun have always been common. In the past, some cultures have even worshipped it as the source of all things — which it is, when you get right down to it. Without the sun, we wouldn’t be here.   It’s not within our purview to examine the various religious beliefs about the sun, but there are quite a few modern misconceptions about our daystar that should be put to rest. In this article, we’ll discuss a few.   Myth 1: The sun is just an average, everyday star.   No one really believes that the sun is the center of the universe anymore, but some of us have gone completely in the other direction with this myth about the sun. It’s true that our sun is mid-range in size and age, but it’s not just any star. It has a few significant characteristics that distinguish it from most of its neighbors.   Of the 50 closest stars, ours ranks #4 in terms of brightness. It’s also near the top of the list for mass, size, and energy production. As it happens, almost all stars are tiny red M-Class dwarfs. While they do tend to last forever, our sun is much brighter, hotter, and bigger than they are.   Myth 2: Summer is when the Earth is closest to the sun.   This myth about the sun seems logical, but it’s only half right — and it isn’t true at all if you live in the Northern Hemisphere. Oddly enough, summer comes for North America, Europe, and Asia when the Earth is farthest away from the sun in its orbit. Why? Because the Earth is tilted at a 23.5º angle on its axis of rotation.   When the Northern Hemisphere is tilted toward the sun, our part of the world gets more light, and the days are longer. This translates into greater warmth. As the sun moves around to the other side of its orbit, we get less light, and the days grow shorter and cooler — even though we’re closer to the sun.   Myth 3: The sun doesn’t rotate.   Actually, it does. This was something Galileo himself discovered (with great difficulty) in the 1600s. Every natural object in the universe rotates, even the galaxy. Our star doesn’t rotate very fast, taking some 25-27days to turn on its axis — but it does rotate, and that’s enough to put paid to this myth about the sun.   Myth 4: The solar wind can push satellites out of orbit.   While the sun does produce something called the solar wind, which is comprised of all the trillions upon trillions of energetic particles that radiate from it every single day, it’s not as strong as all that. This far away from the sun, outer space is a vacuum far harder than anything scientists have been able to create in any lab.   Solar wind and solar flares can, however, cause the Earth’s upper atmosphere to become more agitated, making it hot and dense enough for satellites in very low orbit to encounter more friction. Over time, this can slow a satellite enough that it can fall out of orbit. That’s where this particular one of many myths about the sun comes from. ===================================================================================