VOA慢速英语 哈勃改变了我们对宇宙的概念

　　VOICE TWO:

　　From nineteen twenty-two on, Edwin Hubble began examining more and more distant objects. His first great discovery was made when he recognized a Cepheid variable star. It was in the outer area of the great nebula called Andromeda. Cepheid variable stars are stars whose brightness changes at regular periods.

　　An astronomer at Harvard College, Henrietta Leavitt, had discovered that these periods of brightness could be used to measure the star's distance from Earth. Hubble made the measurements. They showed that the Andromeda nebula lay far outside our Milky Way Galaxy.

　　Hubble's discovery ended a long dispute. He proved wrong those who believed nebulae lay inside the Milky Way. And he proved that nebulae were galaxies themselves. Astronomers now agree that far distant galaxies do exist.

　　VOICE ONE:

　　Hubble then began to observe more details about galaxies. He studied their shape and brightness. By nineteen twenty-five, he had made enough observations to say that the universe is organized into galaxies of many shapes and sizes.

小精灵儿童网站