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Frankly, we just dont understand it. Craig Hogan, University of Washington at Seattle Bill Wolf (Eastern Illinois University) Dark Energy and the Accelerating Expansion of the Universe October 06, 2008 1 / 12 Dark Energy and the

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“Frankly, we just don’t understand it.” –Craig Hogan, University of Washington at Seattle

Bill Wolf (Eastern Illinois University) Dark Energy and the Accelerating Expansion of the Universe October 06, 2008 1 / 12

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Dark Energy and the Accelerating Expansion of the Universe

Bill Wolf

Eastern Illinois University

October 06, 2008

Bill Wolf (Eastern Illinois University) Dark Energy and the Accelerating Expansion of the Universe October 06, 2008 2 / 12

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The Framework

Big Bang and the expanding universe Acceleration of Expansion Dark Energy What’s being done now

Bill Wolf (Eastern Illinois University) Dark Energy and the Accelerating Expansion of the Universe October 06, 2008 3 / 12

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The Big Bang

Universe started in massive explosion First theorized (and denied) by Einstein Experimentally proven by Edwin Hubble in 1920’s Generally accepted theory

Figure: Image from nasa.gov

Bill Wolf (Eastern Illinois University) Dark Energy and the Accelerating Expansion of the Universe October 06, 2008 4 / 12

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The Expansion of the Universe

We use red shift to determine speeds of objects The further an object is, the faster it is receding Expansion didn’t start until about 10 billion years ago There is no “center” of the universe Much like dots on an inflating balloon Space itself is expanding Diverging Universe vs. “Big Crunch” Theory

Bill Wolf (Eastern Illinois University) Dark Energy and the Accelerating Expansion of the Universe October 06, 2008 5 / 12

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Balloon Analogy

Figure: Graphic from UCLA Astronomy

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Acceleration of Expansion

Discovered in 1998 by two teams of scientists Red shifts of galaxies at known distances were too strong Expansion was not slowing down Unknown energy causing expansion called “Dark Energy”

Bill Wolf (Eastern Illinois University) Dark Energy and the Accelerating Expansion of the Universe October 06, 2008 7 / 12

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Dark Energy

Figure: Chart from nrao.edu

Disproportionate amount of dark energy in the universe Many theories being examined

Quintessence Time-varying forms of dark energy Topological Defects

NOT anti-gravity; more like negative pressure Still largely unknown

Bill Wolf (Eastern Illinois University) Dark Energy and the Accelerating Expansion of the Universe October 06, 2008 8 / 12

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What now?

Testing gravity at close distances Double-checking supernova data / looking for “thawing” or “freezing” Mostly gathering data to form hypotheses

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Who cares?

Knowledge of dark energy could have profound effects on particle physics Dark energy makes up the majority of the universe! Effects on Grand Unified Theory Studies may help understand the evolution of the universe

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References I

Chaikin, Andrew. “Dark Energy: Astronomers Still Clueless About Mystery Force Pushing Galaxies Apart.” Space.com. Posted January 15,

2002. Accessed October 6, 2008.

http://www.space.com/scienceastronomy/astronomy/cosmic darknrg 020115- 1.html “Dark Energy.” NASA’s Imagine the Universe. Posted September 26,

2008. Accessed October 6, 2008.

http://imagine.gsfc.nasa.gov/docs/science/mysteries l1/dark energy.html

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References II

Caldwell, Robert. “Dark Energy.” physicsworld.com. Posted May 30,

2004. Accessed October 06, 2008.

http://physicsworld.com/cws/article/print/19419. “Finding a Way to Test for Dark Energy” Research News, Berekely Labs. Posted August 29, 2005. Accessed October 06, 2008. http://www.lbl.gov/Science-Articles/Archive/Phys-SNAP-dark- energy.html.

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