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Gold Medal Eclipse
Observing > Wow. August is a big month for China. Not only is the enormous country hosting the biggest sporting event in the world, but it is also putting on one of the most spectacular sky events, as well - a total solar eclipse.
On August 1/2, the Moon's shadow, like an Olympic anti-torch, will begin a run starting actually in northernmost Canada, moving across Russia, into Mongolia, finishing up in China.
Those few, those lucky few, on the swath will see the sun completely covered by the Moon as it passes in front.
But why so few? Why not everyone? Why that day and not the next? Why not the next month?
The size of the Moon and its distance from Earth account for the limited viewing problem. The moon's shadow is actually a huge cone stretching for over 200,000 miles. That happens to be the distance from the moon to our planet. Meaning, by the time the shadow reaches us it is a small shadow of its former self, sometimes just tens of miles across.
If one happens to be directly in it - ta da! - total solar eclipse. If not, out of luck. Which is why the total solar eclipse is such an elitist event. Just the privileged among us who happen to live at, or make a trip to the streak of shadow blazing across the planet get to see it.
It's not like its counterpart, that lunar eclipse thing, which more than half the planet gets to experience merely by looking up when it happens. Moreover, our shadow on the moon is a hefty one and it takes hours for our satellite to travel through it. A lunar eclipse has a huge viewing audience.
The solar eclipse happens specifically next week because, of course, it is the time in the moon's orbit when it crosses in front of the sun. But it won't happen the next time it passes in front, nor the next time, nor the next time. Why?
The moon's orbit is a little off-kilter. It isn't in the same plane as our orbit around the sun so it doesn't always pass directly in front of the sun. Most of the time it is either a little higher, in which case the shadow misses us over the north pole of our planet, or below, in which case the shadow goes way south. On this present trip, it manages to slash earth across the northern hemisphere.
You may have noticed that these eclipses, both solar and lunar, happen at regular intervals, about every six months or so during "eclipse seasons." Our last eclipse set - lunar/solar - was in February, this one is in August, and the next is next February. Time to put on the Thinking Cap.
These "seasons" are when the moon's path takes it through the imaginary plane of earth's orbit around the sun and, at the same time, all three of us happened to be lined up nicely. Because of the Moon's awkward orbit this only happens about twice a year. It is then that we either block the sun's light to the moon or the Moon pushes itself between us and the sun, an event we will witness next week.
In a couple weeks, when the Moon moves around to the other side of the earth, we will have a lunar eclipse, just as expected. But, sadly, the whole other side of the planet gets to see this one - not we. This is a lose-lose eclipse month for us.
In fact, watching the solar eclipse next week for us in the States will be like watching the Olympics. We will need to see it via satellite, or internet. It will occur during the wee hours of the morning here. If you want to experience it live there will be several sites, including San Francisco's Exploratorium, that will carry live webcasts. Check them out. We won’t get to see a total solar here live and in color until one strikes the Great Northwest in 2017. Make plans now.
Until next time, clear skies!
Posted by Mark Ritter at 2008.07.27 09:18 PM | Comments (0)
