Episode #12-38 "The Harvest Moon Illusion"
FIVE MINUTE EPISODE SCRIPT
MARLENE: And Iím Marlene Hidalgo.
DEAN: And Iím Dean Regas, and weíre here to tell you all about the strange Ďharvest mooní illusion, while we allÖ
ALL: Look up!
JAMES: This Saturday September 29th is the official night of the Harvest Moon. And along with it comes the Harvest Moon illusion, and you can prove this is an illusion in two fun but weird ways. But just what is a Harvest Moon anyway?
MARLENE: Well according to the dictionary a harvest is simply the act of gathering in a crop or the harvested crop itself. And for centuries at this time of year across North America and Europe the fall harvest took place.
DEAN: Now traditionally the full Moon closest to the first day of fall, the autumnal equinox, is called the harvest moon. And since this year the autumnal equinox occurs on September 22nd at 10:47 a.m. EDT the full Moon this Saturday is the closest to the equinox and thus itís the Harvest Moon. Simple.
MARLENE: But there is more to a Harvest Moon than that because even though there is only one official night of the Harvest Moon the visual effects last for three nights, September 28th, 29th and 30th.
DEAN: You see normally the Moon rises approximately 50 minutes later each successive night, but not the Harvest Moon. It rises only 20 to 25 minutes later each successive night. The reason for this is that the path that the full Moon takes as it crosses the sky from night to night when itís closest to the autumnal equinox makes a much smaller angle with the horizon than at any other time of year. But why does it move this way?
JAMES: Well, letís draw two lines in the sky. Now youíll never see them but theyíre key to answering Deanís question. The first line weíll draw is called the celestial equator. It divides the sky into a northern half and a southern half. The second line is called the ecliptic and itís the path that the sun seems to follow through the sky. Notice that these lines are tilted to each other. This is because of the tilt of the earthís axis. Remember that 23 Ĺ degrees tilt we talked about when we explained why itís hotter in the summer?† The sun is at the point where they cross on Sept 22, which is what makes it the fall equinox. The sun, the planets and the moon all move along this line, the ecliptic, not exactly but close. So at this time of year the moonís path is nearly parallel to the horizon, which is why the moon rises close to sunset for several days in a row.
MARLENE: Now before the invention of electric lights this was very important to farmers at harvest time because it meant that they could work after sunset for at least three nights in a row gathering in their crops by the bright light of the harvest moon. Today mechanized farming is all done with artificial lighting so that aspect of the Harvest Moon has lost its original significance. But what it will never lose is its incredible beauty in early evening. Because for three nights we will see it rise just before or just after sunset.
JAMES: And all rising full moons always look much bigger and more colorful than when they're overhead. The reason the full Moon looks more colorful as it rises is because we see it through thicker and dustier layers of our Earth's atmosphere than when it's overhead. Now the reason the full Moon always looks bigger when it's closer to the horizon than when it's overhead is one of the grandest illusions of nature, which you can prove is an illusion yourself this Friday, Saturday and Sunday nights.
DEAN: Simply take a dime, hold it at arm's length when the Harvest Moon is close to the horizon just after sunset and again when it's at its highest around midnight and you'll see that your dime will cover exactly the same amount of the moon. Wow!
MARLENE: But an even more fun way to prove this illusion is to bend over at the waist and watch the rising Harvest Moon upside down between your legs. Because, bingo, it will instantly look smaller than when you look at it right side up. The reason for this is still being argued. But believe me, it's one heck of an illusion.
DEAN: So don't miss next week's three nights of the Harvest Moon because it will be absolutely gorgeous
JAMES: And may even look like an orange pre-Halloween jack o' lantern.
MARLENE: And remember, whether you're right side up or upside down, keep looking up!
Episode #12-38 "The Harvest Moon Illusion"
ONE MINUTE EPISODE SCRIPT
JAMES: Just after sunset look east and you'll see a huge pumpkin colored full Harvest Moon rising.
MARLENE: Itís called the Harvest Moon because itís the full moon closest ot the Autumnal Equinox, which happens on September 22nd at 10:47 a.m. EDT.
JAMES: Now everyone knows that when the moon rises it often looks much bigger than when it's overhead. But this is just an illusion, which you can prove to yourself.
MARLENE: Simply take a dime, hold it at arm's length when the moon is rising and again when it's at its highest around midnight. And you will see that your dime covers exactly the same amount of the moon.
JAMES: For moon illusion #2 bend over at the waist and look at the rising moon upside down between your legs and bingo! It will instantly look smaller than when you look at it right side up. Try it.
MARLENE: Happy Harvest Moon and
BOTH: Keep looking up!
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