Astronomy/Astronomy

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Question
Are sunspots harmful to our skin?

Answer
No. The higher-energy blue, violet and ultraviolet radiation that penetrates our atmosphere and causes tanning, aging skin and eventually pre-cancers can be harmful if not blocked by sufficient clothing or sun-block creams and the like; but the amount of such radiation that reaches the Earth's surface is essentially constant, and is not affected by whether the Sun has any spots on it or not. In fact, somewhat paradoxically, the Sun emits more radiation of all sorts, including the more harmful varieties (though only by a fraction of a percent) when it has no sunspots at all!

There can be some affects on the upper atmosphere, referred to as geomagnetic storms, when a particular sunspot causes a "flare", or a "coronal mass ejection"; and spacecraft that are not "hardened" to resist large variations in the electromagnetic fields caused by such events can be temporarily or partially disabled (hence worries at communication companies and the like if the Sun's "activity" threatens to become greater than normal). But as noted above, this has nothing to do with the effects of sunlight on our skin. So once again, the only thing that affects that is the total amount of solar radiation (which is greater near the Equator than near the Poles, and greater near noon than near sunrise and sunset, and so on), and sunspots do not affect that.

(Concerning the paradoxical change in solar radiation associated with sunspots, there are a number of illustrations and a reasonably adequate discussion of The Sunspot Cycle at http://cseligman.com/text/sun/sunspotcycle.htm )  

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Courtney Seligman

Expertise

I can answer almost any question about astronomy and related sciences, such as physics and geology. I will not answer questions about astrology and similar pseudo-scientific rubbish.

Experience

I have been a professor of astronomy for over 40 years, and am working on an online text/encyclopedia of astronomy, and an online catalog of NGC/IC objects.

Publications
Astronomical Journal, Publications of the Astronomical Society of the Pacific (too long ago to be really relevant, but you could search for Courtney Seligman on Google Scholar)

Education/Credentials
I received a BA in astronomy and physics and a MA in astronomy, both from UCLA. I was working on my doctoral dissertation when I started teaching, and discovered that I preferred teaching to research.

Awards and Honors
(too long ago to be relevant, but Phi Beta Kappa and Sigma Xi still keep trying to get me to become a paying member)

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