We can now observe phenomena ranging from low-frequency radio waves a dozen meters long, crest to crest, to high-frequency gamma rays no longer than a quadrillionth of a meter. That rich palette of light supplies no end of astrophysical discoveries: Curious how much gas lurks among the stars in galaxies? Radio telescopes do that best. There is no knowledge of the cosmic background, and no real understanding of the big bang, without microwave telescopes. Want to peek at stellar nurseries deep inside galactic gas clouds? Pay attention to what infrared telescopes do. How about emissions from the
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