VOA慢速英语 哈勃改变了我们对宇宙的概念
As stars differ from one another, he said, so do galaxies. Some are spiral galaxies like the Milky Way and Andromeda. They have a center, and arms of matter that seem to circle the center like a pinwheel. Others are shaped like baseballs or eggs. A few have no special shape.
VOICE TWO:
Hubble proposed a system to describe galaxies by their shape. His system still is used today. He also showed that galaxies are similar in the kinds of bright objects they contain. All galaxies, he said, are related to each other, much as members of a family are related to each other.
In the late nineteen twenties, Hubble studied the movement of galaxies through space. His investigation led to the most important astronomical discovery of the Twentieth century -- the expanding universe.
VOICE ONE:
Earlier observations about the movement of galaxies had been done by V. M. Silpher. He discovered that galaxies are moving away from Earth at speeds between three hundred kilometers a second and one thousand eight hundred kilometers a second.
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