One evening,a husband and wife are working in their garden. While watering the grass, the wife holds the hose horizontally and the water flows from the end of the hose. She twists the nozzle of the hose to partially close it and suddenly the water shoots farther from the end of the hose. This seems odd to her husband, who wonders, "Why does the stream of water travel farther, since it appears that less water is flowing from the end of the hose?" My challenge is to give a scientific explanation for this unnatural phenomenom.
By Siv Schwink
September 3, 2013
Tonight, as the sun sinks below the horizon, the world’s most powerful digital camera will turn its gleaming eye skyward once again in its 5-year mission to map the southern sky in more detail than ever before. On August 31, the Dark Energy Survey (DES), with an international collaboration of more than 200 scientists, officially began the largest galaxy survey ever attempted.
Counting galaxy clusters. While gravity pulls mass together to form galaxies, dark energy pulls it apart. The Dark Energy Camera will see light from 100,000 galaxy clusters billions of light years away. Counting the number of galaxy clusters at different points in time sheds light on this cosmic competition between gravity and dark energy.
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