Word: nebula
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...almost ready. It is housed in a softly revolving dome 137 feet in diameter. The telescope weighs 500 tons, but is so exquisitely mounted that an electric motor not much bigger than an orange turns it on its bearings. Its 200-inch parabolic mirror gathers four times as much nebula light as Mount Wilson's 100-inch mirror. Palomar will see twice as far, and it may tell Hubble whether the universe is really exploding-or whether even stranger things are happening...
...general method (in practice, enormously difficult) was to determine the intrinsic brightness of objects in a nebula and then gauge its distance (the fainter it is, the farther away). Variable stars called Cepheids, discovered at Harvard, told him that the bright nebula called Messier 31 is 680,000 light-years away. Messier 31 was therefore no mere part of the Milky Way galaxy (the star-congregation in which our sun is a fourth-rate star), but an isolated star-system far out in space and as big as our entire galaxy. Other, longer-ranged measuring sticks carried him farther...
Working with short, amiable spectrograph expert Milton Humason, Hubble studied the light of the distant nebulae. In every case he found a "red shift."* The farther off a nebula was, the faster it appeared to be rushing away, and the enormous speeds (thousands of miles per second) were new, strange and startling to astronomers...
While Humason's spectrographs gradually improved, Hubble theorized until he came to a momentous conclusion: that the speed of recession of the nebulae is directly proportionate to their distance. This meant that each of the large units of matter in the universe (nebulae) is moving away from every other unit. The Milky Way galaxy (the earth's local nebula) is not the only center of the explosion. Every other nebula is equally an explosion center...
Pavements were rippling like thin ice on a pond. Steel and stone buildings trembled in a portentous wind. The sky sizzled as though tons of bacon were frying in an apocalyptic pan. "Obviously, men," gasped the Professor, "the Katz-Alpha-Ogallala nebula is approaching the earth at terrific speed, just as I predicted. We have not a moment to lose." The atom-powered space ship was ready and waiting in Joe's Parkview Garage, and off they zoomed to safety on the planet Mars, where there are marvels enough to fill a year's issues of Flabbergasting Stories...