Solar Eclipse taken by shooting through a couple of layers of old photographic negatives, just for fun. The thin sliver of sun is still enough to overpower the image sensor. |
Illuminated house number. Barely visible here, but it was bright enough to catch my eye. |
Dustbury's post got me to wondering why the moon's shadow was traveling eastward when the sun is traveling westward (the sun rises in the east. Daylight advances ever westward across the face of the Earth). A little math confused the issue even more. As simple as this problem ought to be, it took me several trials before I finally figured out what my model of this situation should look like.
Graph of Speed and Distance Bottom scale is minutes And yes, it's just a coincidence that the bottom scale is 400 minutes long. Spreadsheet with Calculations |
However, since the Earth is a ball and not a disk, this speed is only going to be seen when the Moon is is directly inline between the Earth and the Sun. Before the Moon starts to come between the Earth and the Sun, its shadow is simple traveling across space. When the Moon's shadow first impacts the surface of the Earth, it will be at a tangent, so its speed is infinite. As the shadow passes over the Earths surface, that surface will start turning more toward the sun and more at an angle to the shadow. By the time 40 minutes has passed it's speed has dropped to 2,000 miles per hour.
But the Earth is turning. At the equator that speed is about 1,000 MPH. Now we get to the rotation part. The moon goes around the Earth in the same direction that the Earth turns. Looking down on the Earth from above the North Pole, we see the Earth turning in a counter-clockwise direction. The moon is like-wise turning in the same counter-clockwise direction, but the Earth is turning much faster than the moon is going around. So if we were projecting the moon's position onto the Earth, we would see it move Westward, because the moon is slow moving and the Earth is turning underneath it.
The moon's shadow it traveling at the same speed as the moon (about 1200 MPH), which is just slight faster than the surface speed of the Earth, so as the Moon passes in front of the Earth, it is traveling just slightly faster than the surface of the Earth, so its shadow, the eclipse, moves from West to East.
1973 Concorde Eclipse Chaser (Warning: autostart video) |
Some commercial airlines arrange special eclipse flights.
P.S. All my calculations were done presuming the path of the Eclipse was over the equator. To more accurately model this eclipse, you would need to factor in the latitude, which is constantly changing because apparently the orbital plane of the Moon is at an angle to equatorial plane of the Earth.
The orbital plane of the Moon is at a 5 degree angle to orbital plane of the Earth.
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