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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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Scientists Find the True Hubble Constant!

Scientists have found the real Hubble Constant after 8 years of research. The Hubble Constant is the rate that the Universe is expanding at. They found it to be 70 kilometers per second per megaparsec....more

Gamma Ray Bursts - The Most Powerful Objects in the Universe?

Satellites in the 1960's looked for a type of light called Gamma Rays. They found bursts of Gamma Rays coming from outer space! They can't hurt you. They are stopped by the Earth's atmosphere. We have...more

Galaxies - Star Cities

When we look up at the night sky, we notice that there are many stars in our sky. Stars must like to live together in star cities - galaxies. Our city of stars is called the Milky Way, and it is home to...more

Neutron Stars

Neutron Stars form when really big stars die. When such a star runs out of fuel its center begins to collapse under gravity. When the center collapses the entire star collapses. The surface of the star...more

Spiral Galaxies

Spiral galaxies may remind you of a pinwheel that blows in the breeze. Like a pinwheel, a spiral galaxy is rotating, and it has spiral arms. Through a telescope or binoculars,a spiral galaxy may look...more

White Dwarfs

When stars like our own sun die they will become White Dwarfs. As a star like our sun is running out of fuel in its center it grows into a red giant. This will happen to our sun in 5 Billion years. The...more

Algol

What's in a Name: Arabic for "head of the demon" Claim to Fame: Represents Medusa's eye in Perseus. A special variable star that "winks" every 3 days. Type of Star: Blue-white Main Sequence Star, and...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF