To most laymen, the atmosphere on a clear day or night looks beautifully transparent. The astronomers, aware of this illusion, know that even the clearest atmosphere is opaque to many kinds of radiation. Visible light pushes through it without much loss. So do ultraviolet and infrared if their wave lengths are not very different from ordinary visible light. Most other radiation coming from outside the atmosphere is absorbed before it reaches the ground. The chief exception is radio waves, which penetrate not only the atmosphere but also thick clouds.
British astronomers, often frustrated...
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