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In the following partial solar eclipse, the moon is "invisible" rather than being dark. By contrast, if someone stands between my view and the sun, they will appear as a dark figure instead of invisible.

Why doesn't the moon appear as a dark circle instead of being invisible?

enter image description here

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What you see is clouds which are in front of the Moon. If there were neither clouds nor atmosphere between you and the Moon and you had amazing eye sight, you couldn't see any stars where the Moon is, but the Moon itself illuminated from the Earth (which is in full Sun ligth). Thus the Moon is neither invisible nor dark.

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  • $\begingroup$ Is there an astrological term for something that is not invisible but cannot be seen? $\endgroup$ – user1477388 Dec 1 '14 at 21:17
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    $\begingroup$ Astrological is fortune-telling, horoscopes, etc. I think you are looking for an astronomical term. I'm not aware of a term for exactly what you are describing. $\endgroup$ – Mark Bailey Dec 1 '14 at 22:11
  • $\begingroup$ @user1477388: What Mark Bailey said about the word "astrological", but to answer your question I think the word "hidden" covers what you're describing. $\endgroup$ – Keith Thompson Dec 1 '14 at 23:38
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Light refracts in the atmosphere, causing the light to scatter in many directions. This light scattering is what causes our day to be blue, our sunsets to be their red-orange-violetish colors and allows us to see the light of the Sun shortly before sunrise and after sunset. As this only begins happening in any significant amount after the light enters Earth's atmosphere, there should not be any notable difference in the color or intensity of light between you and the moon and any other part of the sky at a relative angle from the Sun.

On the other hand, the foreground does not have direct light on the photographer's side (because it is nearly between the sun and the photographer) and there is a very limited amount of atmosphere to scatter light. As a result, less light will be coming to the camera from that direction.

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Sunlight reflects through the clouds, making them visible in front of the dark Moon.

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  • $\begingroup$ This is a very succinct answer. I think I understand now. Thanks. $\endgroup$ – user1477388 Jan 30 '15 at 16:20

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