Announcements
Transcript - Homeschool Heartbeat Interview
As mentioned, my interview with Mike Farris from HSLDA was featured on this week's Homeschool Heartbeat. Mike and I had a very nice chat during the interview in July and he seems like a really neat guy. In case you missed the broadcasts, the transcripts and also audio podcasts from each installment are posted at Homeschool Heartbeat web site. Hope you all can check them out.
Signs & Seasons Review at EHO
Our
Signs & Seasons astronomy curriculum has recently received positive reviews at
The Old Schoolhouse and also
Homeschool Enrichment magazines. Hope you all had a chance to read those.
Signs & Seasons has also recently received a wonderful, comprehensive
review from Mrs Jean Hall at
Eclectic Homeschooling Online (EHO). If you've been unsure about ordering
Signs & Seasons, please check out Mrs. Hall's review since she is someone who really understands what we're trying to accomplish with this curriculum. Here are some exerpts:
This is a thorough treatment of astronomy written in an engaging style that has kept the attention of our littler ones during read-aloud time though dealing with complex issues suited to further study by older students.
The author discusses how the night sky changes with the seasons, making for a wonderful foundation for stargazing. I can't tell you how satisfying it is to be outside and hear a small voice pipe up, "There's the Big Dipper! Look, it leads to the North Star! That way's north!" or "I found Cassiopeia!" or "There's Saturn!"
Dance of the Planets
Earlybird Special - Venus and Mars
Another thing I don't like about the hot, ticky Dog Days of Summer is that it's light in the morning when I'm waking up. I don't know about you folks, but I'm a Night Owl, not an Earlybird! I'm usually fast asleep at 5:00 AM when the summer dawn is breaking over Cleveland, Ohio. I like the darker months when one can get up at a decent hour and still see some morning stars before the sunrise.
Anyway, I was up at 6:30 this week and had a spectacular view of the classic Autumn morning sky featuring two very bright planets.
Orion
I'm always amazed at how quickly Orion climbs the morning sky this time of year. As reported in recent Updates, Orion only emerges from the sunrise in early August, and it reaches the meridian only a month or so later. This is only an illusion because the days are getting shorter during August and September. If you're up in the morning, keep an eye on Orion as the days quickly continue to grow shorter for those of us in the nrothern hemisphere.
Our friends in the southern hemisphere will see the opposite sort of thing. As the days grow longer in Australia and New Zealand, Orion will appear to hang high in the middle of the sky through about November. This phenomenon is complex to explain and we hope to discuss it in detail in a sequel to Signs & Seasons.
Mars
If you can find Orion in the morning sky, you can't miss the bright red planet Mars. Mars is currently hovering to the north of Orion, over the top of his head as seen from the northern hemisphere. Mars is very bright these days, shining at magnitude zero, and outshining all the very bright first magnitude stars in and around the neighborhood of Orion.
If you're an Earlybird, keep your eye on Mars over the next couple months as it will move east into the constellation Gemini, and will begin its retrogradation where it appears to move backwards among the stars. We'll (hopefully) find the time to report on Mars as it approaches opposition on Christmas Eve, December 24, 2007.
Venus
Though you should have no problem whatsoever spotting Mars, there's no way you'll be able to miss the dazzling planet Venus. In the Update we showed that Venus was in the evening sky all through summer, and vanished into the sunset in late July, passing before the Sun at inferior conjunction on August 18. The speedy planet has now shot over to the other side of the Sun, quickly becoming the Morning Star. Venus will now dominate the morning sky through the winter and spring of 2008, passing behind the Sun on June 9 of next year.
The "Morning Star" is mentioned several times in Scripture, and in the Apocalypse is another name for Jesus:
I Jesus have sent mine angel to testify unto you these things in the churches. I am the root and the offspring of David, and the bright and morning star. - Revelation 22:16
This is clearly a Biblical metaphor since Jesus is certainly not the planet Venus! At any rate, we can enjoy the happy sight of brilliant Venus rising before the Sun as a bright harbinger of day.
If you'd like to know more about the seasonal constellations and the various motions of the visible planets, please check out Signs & Seasons, our homeschool astronomy curriculum.
We do what we can to explain these topics in this newsletter, but they are explained in much greater detail in the curriculum.
Besides being a homeschool curriculum, it makes a great gift for the Christian science and nature enthusiast in your family!
Great for students of all ages!
The Autumnal Equinox
The days have grown shorter, and we will soon reach the autumnal equinox on September 23. This is the first day of fall for those of us in the northern hemisphere. On this day, the Sun crosses the celestial equator on it's way south to the winter solstice. The Sun is in exactly the midpoint of the celestial sky, and the length of the daylight is equal to the length of the night -- each being 12 hours. In fact, the word "equinox" literally means "equal night," coming from the Latin words "aequus" (equal) and "nox" (night).
Since the study of Classical Astronomy is in steep decline in our generation, not many people have heard of the "celestial equator." This is similar to the Equator on Earth, which is the midpoint between the frozen North Pole and the South Pole. Readers of the Update and Signs & Seasons are aware that there are also poles in the sky. The North Star, also known as Polaris, is a star that hangs high in the sky above due north. The bowl stars of the Big Dipper point at Polaris. This trick has helped navigators for centuries to find direction. There is also a south pole in the sky, but it is below the horizon and invisible from the northern hemisphere.
Anyway, like the Equator on Earth, the "celestial equator" is a circle in the sky, midpoint between the celestial poles. Now here's the neat part -- the celestial equator crosses the horizon in the middle of the sky between the north and south celestial poles... at exactly due east and due west. In fact, this is the traditional definition of east and west. So when the Sun crosses the celestial equator on the equinoxes, it is the only times of the year when the Sun can be seen rising due east and setting due west.
(((((((ACTIVITY ALERT!!!!)))))))
Here's another activity you can try with your kids. In the weeks before the equinox, you can see the Sun setting to the north of due west. As the Sun approaches the Equinox, it sets closer and closer to due west, finally setting due west on the actual evening of the equinox. Then in the weeks after the equinox, you can see the Sun setting increasing to the south of due west.
Many streets in the continental USA have been layed out to line up with the compass points. Odds are that most of you reading this either live on a street that runs directly east to west, or else you are near a street that runs directly east to west. If you're not sure, look on a map of your city to find such a street. Try to find a street that has a clear view to the horizon. We have a freeway overpass near our house that offers such a view, with the freeway heading toward the horizon at due west.
So anyway, once you find a good nearby road, try to watch the sunset from this street a couple times a week over the next month (weather permitting of course!) Try to note any landmarks on the ground near the setting sun, i.e. a distant tree or building. Over the next month, you'll be able to see the setting Sun move in comparison with the landmark as it heads south, and setting due west on the day of the equinox. In this way, you'll be able to indirectly observe the Earth progress in its orbit around the Sun!
((((((( OPTIONAL ACTIVITY!!!!)))))))
As a last note, some folks say you can balance an egg on end on the equinox. This is just an urban legend! It's equally easy or hard to balance any egg on its end on any day of the year! Try it yourself over the next month! Some eggs will balance and some won't, on any day of the year.
Equinox Over Equador
As we've seen in in the Update, there are many correspondences between the Earth and the sky. Just as we use latitude and longitude to coordinate locations on the globe, there is a similar system of coordinates in the sky. There are North and South Poles in the sky, just like on the Earth. And just as there is an Equator in the middle of the Earth between the Poles, there is also a celestial equator in the middle of the sky.
For people who live on Earth's Equator, the celestial equator passes directly overhead, at the zenith. On the equinoxes, the Sun appears to cross the celestial equator on its way to the next solstice. So on the Equator, the Sun can be seen passing directly through the zenith at High Noon on the Equinox. At this time, your shadow would disappear underneath you!
The Equator passes through several nations of Africa and South America. But only one nation has connected its national identity to its location along the middle of the Earth -- Republica de Ecuador -- whose very name means "Republic of the Equator." This identity is even reflected in the national flag of Ecuador, which includes a Coat of Arms showing the Sun along the zodiac, passing directly above the land and sea of Ecuador.
In Ecuador there is a place called Cuidad Mitad del Mundo -- "City of the Middle of the World." At Mitad del Mundo, directly on the Equator, is an Equator Monument. This monument has four sides, oriented to face in the directions of the compass points. A brass globe sits atop the monument depicting the "sphaera recta" or "right sphere" -- the Earth lying "on its side" as it would appear from the Equator.
The Equator Monument was constructed to commemorate two 18th century French scientific expeditions to precisely measure the length of a degree of longitude at the Equator. These measurements were used later in that century to derive the value of the meter, given as one ten-millionth of the distance from the Equator to the North Pole.
Extending down the avenues from the Equator Monument is a yellow line designating the precise latitude of the Equator -- zero degrees, zero minutes and zero seconds. It seems popular for visitors to have their picture taken straddling this line, with one foot in the northern hemisphere and one foot in the southern hemisphere.
Visitors to Mitad del Mundo at High Noon, local time, on this week's equinox will have a twice-annual opportunity to stand on the Equator while the Sun is overhead at the zenith, crossing the celestial equator. These folks can see their shadows vanish underneath while standing in two hemispheres! I wonder if anyone visiting that day will appreciate this unique phenomenon.
At any rate, Mitad del Mundo is one place that this writer would like to someday visit. But unless we are blessed with unexpected prosperity, it's not likely to be our family vacation anytime soon! A trip to Ecuador could also include hiking in the Andes Mountains and a visit to the Galapagos Islands to see the giant tortoises and Darwin's finches (which are still finches!) Here are some links with more information on Mitad del Mundo:
http://www.ecuador365.com/mitad1.html
http://www.equaguia.com/mitaddelmundo/historical.html
((((((ACTIVITY ALERT))))))
For those of us who won't be traveling to Ecuador for this week's equinox, here's a simple activity you can do at home. You can find your latitude from measuring the length of shadows at Noon and doing some simple mathematical steps on a calculator.
First thing, find out your latitude for the place where you live. If you have a geographical atlas at your house, or even a road map, you can probably find the latitude of your home from that. Here in Cleveland, Ohio, our latitude is about 41 1/2 degrees north. Also, the longitude and latitude of every post office in the Unites States is recorded, and someone at your local post office branch should be able to provide you with your latitude.
If the sky is clear on Wednesday, go out with the kids at "High Noon," which is not the same as 12:00 PM. "High Noon" is the time when the Sun reaches its highest point in the sky, when it is high in the southern sky, and shadows point directly north. (Or, if you live in the southern hemisphere, the Sun is highest in the northern sky, and shadows point south.)
With standard time and daylight savings time, High Noon can be anytime between 12:30 and 1:30 PM, depending on where you live within your time zone. But if you can find direction at your house, check a couple times til the shadows are pointing toward the north (or south).
Now, measure the height of something using a tape measure. It can be a stick stuck in the ground or even a person. It might be fun to have the kids measure their Mom to see how tall she is. Or go ahead and measure all the kids, just to collect more data. Then measure the length of the shadow(s) of Mom, the kids, the stick or whatever you used.
Next, draw a picture of a right triangle on a piece of paper. Label the vertical side of the triangle with the height of the measured object or person. Label the horizontal side of the triangle with the length of the shadow. The other connecting side of the triangle is called the "hypotenuse."
For those who are "mathematically challenged," this can be the scary part -- you have to do some simple trigonometry by pushing some buttons on the calculator. But it's not all that bad, mostly just a division problem, and the following walkthrough will make it easy.
If you have any version of Windows on your computer, you already have a built-in calculator. Click the "Start" button and find Programs=> Accessories. Your calculator should be there, so click the icon and it should open up. In the "View" drop-down menu of the calculator, make sure it's in "Scientific" mode and not "Standard."
In the calculator, type in the measured length of the shadow, then hit the slash button -- " / " -- to divide. After that, then type in the measured length of Mom or the stick, etc. Then hit " = " (equals). Leave this number there for a second and go over to check the box where it says "Inv." Then hit the "tan" button. The answer on the display should be close to the number of your latitude that you read from the map.
The number on the calculator probably won't be exact because of various measuring errors that would be expected with such a simple experiment. But the number will hopefully be close enough to show the remarkable mathematical order in God's Creation. Remember, this only works twice a year on the equinoxes. But you can watch the shadows in the coming months as the lengths of the shadows will change with the seasons.
