Word: nebula
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Dates: during 1940-1949
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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...
Casting around for a layman's analogy, Hubble compared the exploding universe to a rubber balloon with small dots (representing nebulae) spaced equally far apart on its surface. When the balloon is blown up larger, each dot becomes farther from every other dot. Place an observer on any dot, and he will see the same picture. Every other dot-nebula will be moving away from...
...announcement of the exploding universe theory threw all grades of scientists-from semi-mystic philosophers to earthy materialists-into counterattack. Some critics could not believe that the nebulae move at such breakneck speed. Einstein's Relativity (supreme law of physics) says that nothing can move faster than light (186,000 miles per second). But Hubble and Humason have clocked a nebula about 250 million light-years away that seems to be moving at 26,000 miles per second, more than one-eighth the speed of light. They have glimpsed nebulae twice as far away. If the nebulae continue...
...light waves, making them longer (redder) than normal. But since red light contains less energy per unit (photon) than violet light, Bubble's critics suggest that light may lose some of its energy in traversing space, thus turning redder. It may start out from a distant nebula as young, vigorous violet and arrive at the earth after millions of weary years as old, tired red. If that is what happens, perhaps nebulae are not moving...