OldProf
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 p.1 #18 · Moon's Heading. The Doppler Effect? | |
Older Fossil wrote:
OldProf wrote:
Greg Campbell wrote:
It will be moving to the upper right, headed toward the '1' on a 12 hour clock.
Why do you ask? 
Thanks for the question Greg
The picture (and every other large one taken of the moon for that matter) illustrates the rare case of an optical doppler effect. The reflected sunlight's color, from the moon to the earth, is shifted according to how the moon is moving relative to us. It is in the order, from high to low frequencies: violet, indigo, blue, green, yellow, orange and red.
The subtle Doppler effect will be most visible at the circumference of the moon. Notice the blue color at the circumference in the upper right range between 9:30 to 12:00 to3:30 on the 12 hour clock. The maximum blue color is, as you correctly noted, at 1:30 and is the direction of motion of the moon! In the lower left range from 3:30 to 6:00 to 9:30 the circumference is yellow!
An even more subtle form of the Doppler effect becomes apparent if you magnify the circumference to the pixel level around 1:30. There you will see the blue to red layers stacked perpendicular to 1:30. Really fascinating.
Love your lanscapes and macro pictures. They are also accompanied by a unique sense of humor.
Take care and cheers
Saba
PS. This should not be misinterpred as a form of chromatic abberation.
Call me skeptical! I don't have the time right now to calculate the magnitude, but from my understanding of the physics, at the relative velocities involved, the wavelength shift should be miniscule and not detectable by our vision.
Also, the motion most people ascribe the moon is mostly apparent motion caused by the earth's rotation. The actual orbital motion of the moon is in the opposite direction from its apparent motion and is actually orbiting in the same direction as the earth's rotation. But the earth rotates much faster making the moon's apparent motion seem to go the opposite direction. This is why the moon rises about 53 minutes later each day.
I'll side with imperfect optics for this effect.
Art
Art, I think you are right about the magnitude of the shift. A simple back-of-the-envelope calculation, the earth would have to rotate 1000 times faster to cause a Doppler shift from blue to yellow. I will look into it further and try to get the true relative velocities (speed and direction).
That's the beauty of science and scientists. Every phenomenon can be challenged and scientists accept these challenges and rethink things until the phenomena or effect is fully understood.
Thank you for your comments. They are very helpful!
Saba
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As long as someone else tells me the rise/set/phase, I'm good. Great shot of the moon. 