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Name: Doug S.
Status: other
Grade: other
Location: WA
Country: N/A
Date: 6/22/2005

I have heard a casual comment that the moon receives 20 times as much light as the earth does, due to the lack of an atmosphere. My question has to do with relative apparent brightness, if a person was standing on the moon compared to the earth. Also, given that the moon has no atmosphere, would there not also be an immediate extreme risk of eye damage due to far higher UV and infrared light on the moon?

The "insolation" (the amount of light from the Sun impinging upon an interstellar object) of the Moon and Earth would be similar if the detector is above the Earth's atmosphere, since the intensity in the absence of an absorber decreases with distance, R, like 1/R^2. This neglects fluctuations of the solar output, occultations, and the like. You are correct that the Earth's atmosphere absorbs a significant amount of ultraviolet and infrared radiation. In the absence of an atmosphere, there is a risk of eye damage from ultraviolet, infrared, and even intense visible light. In addition, there are solar "winds" in which streams of particles (largely protons, electrons and alpha particles).

Vince Calder

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