Word: lightly
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Dates: during 1940-1949
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...Into Space. Even as an apprentice astronomer, Hubble concentrated on the nebulae-the faint patches of light scattered among the stars. Some had been proved mere wraiths, irregular clouds of dust shining by reflected starlight. Others, more interesting, were globes, ellipses, open spirals like patterns of fire from great spinning pin wheels. When the brightest of these were photographed with powerful telescopes, they dissolved into vast congregations of faint stars, whose dimness suggested that they might be very far away. But astronomers, lacking a proper measuring stick, were not agreed. Some thought that the nebulae were comparatively near and small...
...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...
There seemed to be no end to the swarming nebulae. The most distant showed as tiny, dim blobs. By a complex statistical method Hubble proved, after years of work, that these dimmest glimmers were so far away that their light, speeding at 186,000 miles per second, took 500,000,000 years to reach Mount Wilson...
Universe in Flight. Astronomers have a speedometer to clock the motions of skittish heavenly bodies. They take spectrographs: photographs of the body's light spread out by a prism into a band of colors. If the band is "shifted toward the red" (i.e., if it is redder than normal), it shows that the body is moving away from the earth...
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...