It's time for our weekly Just Ask feature, where the experts tackle your questions on science and technology. John Eichelberger, a volcano expert with the U.S. Geological Survey, answers the question, "Why Does the Earth Have Volcanoes, and…

Regarding the expanding universe which recent observations shows is accelerating: I understand that not everything is expanding, just the space between galaxies. Is that correct? If so, why? -- Bill Ellena It's true -- not everything is expanding. The earth…

Robert Kirshner, an astrophysicist from the Harvard-Smithsonian Center for Astrophysics, answers the question, "What is a supernova?" A supernova explosion is something where you see a star that you hadn't seen before suddenly turn billions of times brighter…

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