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This image represents an expanding Universe. The arrows show that the movement is outward from the center. The spirals represent galaxies.
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Hubble Flow: The Expanding Universe

In the 1920's the famous American astronomer Edwin Hubble made an amazing discovery. He found that, no matter which direction he looked into space, distant galaxies appeared to be moving away from us. The farther away the galaxy is from our galaxy the faster it moves away from us. Hubble was observing the expansion of the Universe.

What does it mean that the Universe is expanding? Imagine baking a loaf of raisin bread. As the bread rises it also expands. All of the raisins move farther apart from one another. Every single raisin would see all of the others moving away from it. All of the galaxies in the universe are like the raisins in the bread.

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The Fall 2009 issue of The Earth Scientist, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our online store.

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Galaxies - Star Cities

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA