This is the Classical Astronomy Update, an email newsletter especially
for Christian homeschool families (though everyone is welcome!) Please feel free to share this with any interested friends.
Praise
ye the Lord. Praise ye the Lord from the heavens: praise him in
the heights. Praise ye him, all his angels: praise ye him, all his hosts.
Praise ye him, sun and moon: praise him, all ye stars of light.
Praise him, ye heavens of heavens, and ye waters that
be above the heavens. - Psalm 148:1-4
IN THIS UPDATE "Super" Moon???
Hello Friends,
Hope everyone is doing well. This is the first newsletter since August, and one of only a few in 2016. As mentioned before, I'm still devoting a large portion of time to the
upcoming 2017 USA Total Eclipse of the Sun. Amazingly, there is still very little awareness of this upcoming celestial glory. I'm hoping this will change soon, as everyone needs to make their plans, while there are still options.
Just a reminder about our website for the 2017 eclipse, American Eclipse USA. I hope you'll all come to visit the site. If you haven't yet done so, please like us on the American Eclipse USA Facebook page, and follow us on Twitter. For over a year, I've been working on a special project, an eclipse ebook. Eclipses Illustrated will provide a comprehensive
understanding of solar and lunar eclipses and their causes. Like our Signs & Seasons curriculum, Eclipses Illustrated uses the visual medium of illustration to provide a visual understanding of the visual subject of eclipses.
I had originally hoped to have the entire project completed well
ahead of the August 21, 2017 date of the USA eclipse. Since that deadline is now unfeasible, Eclipses Illustrated will be serialized, and released in five short "comic book" installments. Book 1 is currently completed and will be released soon, in the Amazon Kindle Store and a couple other selected outlets.
Book 2 is currently well along in production, and will hopefully be released shortly. We'll send along more info in future newsletters!
Eclipse Shades Gift Idea!
Friends, I hope you will all believe me when I tell you that the USA Total Eclipse of the Sun will be a BIG DEAL next summer! And as the time approaches, Eclipse Shades solar viewing glasses will
become a hot commodity! There are about 300 million Americans, and even if you do not travel to totality, that's the number of Americans who will be able to see at least the phase of partial eclipse on Eclipse Day.
So next summer, 300 million Americans will all want their own pair of Eclipse Shades! You can help your friends and family by giving the gift of eclipse viewing this Christmas! You can order a bulk quantity of Eclipse
Shades and give them as gifts! They make great stocking stuffers!
Eclipse Shades are very lightweight, made from cardstock
frames with mylar lenses. Include a pair in your Christmas cards! Send a pair to everyone on your list! Not only will you be giving your loved ones something inexpensive that they can use next summer or anytime, but you'll be helping to spread the word about the upcoming eclipse, one card at a time!
Please visit our Eclipse Shades page at our website. Our Shades are printed with the date of the USA eclipse, August 21, 2017. As you can see from the pricing, with even a small bulk, our Shades cost less than a buck apiece. This will be the perfect gift for all the sky watchers
in your life, young and old!
These Shades will be in high demand next summer, and are likely to sell out early. So why not beat the rush and order some right now, before Christmastime?
Thank you friends for your orders! And Merry Christmas!
Moonfinder
Special We're still running our "informal" special... anyone who orders our Signs & Seasons homeschool astronomy curriculum receives a free copy of Moonfinder, our children's storybook. And anyone who orders a copy of Moonfinder, we're giving them an extra copy to share with a friend. Everyone who has seen
Moonfinder agrees that it's a wonderful children's story, and it's guaranteed to help young kids (and their parents!) understand the monthly cycle of the Moon's phases. This offer is not posted on our site but anyone who orders our curriculum will receive a free copy of Moonfinder just the same. Thanks, friends, for your interest and support.
For more information about topics from Classical Astronomy discussed in this newsletter, please check out
a homeschool astronomy curriculum (but popular with adult readers too!)
Visit our archive of previous editions of the Classical Astronomy Update newsletters, going back to 2007.
Visit this page to subscribe to the Classical
Astronomy Update and the Northeast Ohio Astronomy (NEOastro) newsletters.
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"Super" Moon???
Normally, this newsletter reports about upcoming sky events. The fact is, there is not much going on at the moment, though 2016 has been an exciting year for observing planetary
conjunctions. In this newsletter, we want to take some time to write about a sky non-event that just occurred this week... the so-called "supermoon."
As you are undoubtedly aware, over the last several years, the media have become fond of reporting about the occasional "supermoon," a grandiose word for a perigean Full Moon. Due to the Moon's elliptical orbit around the Earth,
there is a time every month when the Moon is closest to our world, called perigee. At the opposite end of the month, there is a time when the Moon is at a point of its orbit farthest from the Earth, called apogee.
Because of the "wheels within wheels" of the celestial cycles, about every 14 months, perigee coincides with the Full Moon. In all the other
months in between, perigee occurs in the other lunar phases, like the New Moon and First and Last Quarter.
When the Moon is at perigee, being physically closest to the Earth, it appears slightly larger in the sky than average. Also, due to the greater proximity of the Moon to our world, there is
a slightly greater gravitational pull. This is simply enough to raise a slightly larger tide. Normally, the greatest tides occur near the New Moon and Full Moon, when the lunar gravity lines up with the gravitational pull of the Sun. These are called spring tides. But when the New or Full Moon coincides with perigee, these are the greatest tides of all, the perigean spring tides.
Well anyway, the term "supermoon" was coined in the 1970s by an astrologer, and is not a term originating from science or astronomy. An arbitrary definition was given for a supermoon of being a Full Moon within 90% of perigee.
Not many people heard of the term "supermoon" until the 2011 earthquake and tsunami which created
the disaster at the Fukishima nuclear plant in Japan. At this time, an astrologer (not an astronomer) hypothesized that the earthquake was caused by the "supermoon," in which the Moon's perigean gravity tugged extra hard on the Earth, causing the ground to move and thus the earthquake and the ensuing disaster.
Well, astrologers should stick to casting horoscopes and other fortune
telling nonsense and leave the actual astronomy to the astronomers! We have always had perigean spring tides in the past, throughout all history, and it's well understood from Newton's law of universal gravitation that even the perigean Moon does not exert enough pull to produce a "land tide" that would move the Earth's crust. Though the New Zealand earthquake just this week also happened to occur near a perigean Full Moon, we have had other "supermoons" and other earthquakes since
2011, and many more for all of past history, and most have not coincided. There is no evidence of any correlation between earthquakes and perigean Full Moons.
But the media is nevertheless undeterred! Ever since 2011, every time a perigean Full Moon comes around, the news is inundated with "supermoon" reports. This is not necessarily a bad thing if it motivates
people to go outside and take a look at the Full Moon, especially for those how might not look otherwise. But as it has worked out, these "supermoon" reports have become an occasion for propagating misinformation.
For example, we heard all about the supermoon "Blood Moon" of 2015, which was reported as being an extra-special supermoon. Some construed this as really, REALLY
emphasizing the prophetic significance of the "Blood Moon" eschatology. Well, it's more than a year later and no particularly ominous events came to pass (though some have considered the Cubs-Indians World Series to be a sign of the end times!)
This week, the media were filled with reports of a
"superDUPERmoon"!!! This was the "biggest, closest supermoon since 1948!!!" and "The Moon will not be this close to the Earth again until 2034!!!!" While these astro-factoids sound very impressive. the reality of it all is actually quite mundane.
The Moon moves through extremes in its orbit, being typically
as distant as 252,000 miles at apogee, and normally as close as 222,000 miles at perigee. On average, the Moon is about 240,000 miles away from the Earth. At all times, the angular size of the Moon in the sky is about 1/2 degree. In this way, 360 Moons placed end to end could span an arc across the visible sky. This is actually very small! The Sun is also about the same apparent size. But the Sun and Moon actually appear large in the sky because of their
considerable brightness, which enhances our perception of their actual size.
Precisely speaking, the Moon has an average angular size of 31.086 acrminutes, in which there are 60 arcminutes in a single degree of arc. This is roughly the same angular size of a pencil eraser held out at arm's length, assuming an
adult arm of about 24 inches from the eye to the pencil. Try this and see that this is not a very large size at all! It's certainly not as large as one might expect.
We're told in typical media reports that during a "regular" supermoon, the Full Moon is about 14% larger than average, and 30% brighter. But this is not a very large amount on the celestial scale.
This only amounts to the Moon appearing about 1/13th wider than average. This would be like the average width of the Moon with an additional width of a pencil as seen from 30 feet away! Get a tape measure and look at a pencil from that distance. Notice how minor of an amount that really is!
A scale representation of an average Full Moon side-by-side with the perigean
Full Moon of November 14, 2016 is shown below:
While this subtle size difference can be seen in such a depiction, there is no actual way to readily notice this 14% difference over the span of months. The scientific way to make such a visual determination
would be to record a series of angular measurements of the lunar diameter. Barring that, one would have to rely on memories of previous Full Moons and compare those with the present sighting. Any such observations would be subjective and would not be based on any objective evidence, and would only be the result of impressions and opinions, but nothing concrete. Maybe if the supermoon would double or triple the normal size of the Moon, it might make a very strong impression and
be something significant to notice.
In spite of the news stories, the 2016 supermoon is really not that much closer than a normal supermoon. At the time of perigee, the Full Moon of November 14, 2016 was 221,526 miles away from the Earth. However, during the "Super Blood Moon" of September 28, 2015, the Moon was 221,752 miles from the Earth, only a lousy 226 miles further away than
this week. A couple hundred miles is insignificant compared to the overall distance from the Earth to the Moon, only about 0.1%. Thus, the "historic," "spectacular" supermoon of 2016 does not really offer anything out of the ordinary to see.
According to the hype, the 2016 supermoon is the "closest since 1948!" and the Moon "won't be closer until 2034!" But the
The Full Moon of 1948 was only 30 miles closer to the Earth than in 2016! And the Full Moon of 2034 will be a mere 21 miles closer to Earth than this year! Think about it... on an astronomical scale, how much difference could that really make? The answer - the 1948 supermoon appeared 0.01% wider than in 2016! And the supermoon of 2034 will appear a whopping 0.02% larger than this year!
Perhaps the most unfortunate aspects of supermoon reporting is when casual observers read stories that instruct them to go out and observe the Full Moon at moonrise, shortly after sunset. At such a time, one will instead notice the "Moon Illusion." Celestial bodies always appear larger when near the horizon, while rising and setting. This applies to the Sun and Moon and even constellations.
However, this strictly an optical illusion. If you take your pencil at arm's length and compare to the Moon while rising, it will be the same size while appearing big and bold at the horizon than a few hours later, when it appears small while high in the sky. The measured angular diameter of the Moon is exactly the same. The Moon Illusion is well understood to be strictly the result of psychology, an artifact of human
perception. Such spectacular sightings of the rising Moon should not be confused with any purported enlargement due to the "supermoon" effect.
As for the reported difference in brightness, it's worth considering that celestial brightness is measured on the stellar magnitude scale.
Each stellar magnitude is about 250% brighter than the next fainter magnitude. For example, the first magnitude stars are the brightest stars, and they are about 250% brighter than the second magnitude stars. So a 30% difference in lunar brightness would be 130% brighter than average, or only about a half magnitude on the scale. Considering that a typical Full Moon is at a magnitude of about -13.5, 30% does not add very much additional brightness.
The apparent brightness of the Moon can vary considerably based on atmospheric conditions. Water vapor in the air can affect the transparency of the atmosphere, which is a much greater factor in visible brightness than a mere 0.5
magnitude. We've all noticed that a frosty Moon on a cold, crisp, clear winter night will be much more brilliant than a murky Moon of a humid summer night.
Many people swear by these supermoons, and stand by their reports that the Moon actually appears larger and brighter than normal.
This might be due to the power of suggestion, something at which the media is very good! Some people also claim to have superior eyesight, and can notice vivid color differences in the stars and other celestial objects. Others claim to be able to spot the "horns" of Venus or the moons of Jupiter with the unaided eye, without a telescope. Perhaps there might be some gifted individuals able to perceive those few extra arcminutes of lunar diameter during a supermoon, but it's
highly unlikely that most will have the visual acuity or the observing experience to notice any significant difference.
Pop astronomer Neil deGrasse Tyson recently quipped that, if you have a 15 inch diameter pizza, you don't call a 16 inch a "superpizza." The esteemed Dr. Tyson is one of the majority of people in mainstream astronomy discouraging the public from getting all hyped up
by supermoon reports in the media.
Supermoon reports are based on calculated lunar orbit numbers, but don't offer anything much to see compared to any regular Full Moon. But on the other hand, I'm glad if such media reports help people to take the time to go outside and look at the sky, which they might not do otherwise. The Moon is always a beautiful sight, and is up there all the time, on
nearly every clear night.
My fear is that if media-hyped sky event fails to impress, it might leave some people disillusioned and skeptical, and they'll be disinterested when a genuinely worthy sky event comes along. I'm also concerned by the selective misdirection of the media, how supermoons receive so much fanfare, while truly spectacular sky events go unmentioned, like the
upcoming 2017 USA Total Eclipse of the Sun.
Thanks to all of you who do take the time to look up at the LORD's glorious sky! Let me offer you an early Merry Christmas and blessings to you and your family for the upcoming
year!
For more information
about sky events, please visit our website and keep an eye on our Facebook page. Til next time, God bless and clear skies,
- jay
The Ryan Family Cleveland, Ohio,
USA
When I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained, what is man that thou art mindful of him? and the son of man, that thou visitest him? - Psalm 8:3-4, a Psalm of David
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