The proton-proton chain is an important nuclear reaction which occurs inside the core of main-sequence stars such as the Sun. It involves the conversion of hydrogen nuclei (protons, or 1H) into helium nuclei (4He) via several steps. First, two protons come together and stick. One of them is converted into a neutron, and debris is emitted in the form of a positron and a neutrino. The result is deuterium - a nucleus consisting of one proton and one neutron. With the addition of another proton and the subsequent emission of a gamma-ray, a new product is formed - an isotope of helium called helium-3 or tralphium. Finally, two of these helium-3 nuclei collide, and two protons are ejected, to make hydrogen. On average, a typical proton can wait...
Science Photo Library was founded in 1981 by Michael Marten, one of the authors of "Worlds Within Worlds", a book exploring different ways to observe the universe - from electron micrographs, to images of earthrise taken from the Apollo spacecraft. When Marten started receiving requests for the beautiful images in the book, he had an idea of setting up Science Photo Library.
Since then, Science Photo Library has continued to work alongside world acclaimed photographers and the leading science and medical experts to provide a central source of the best science and specialist imagery available. Although the collection started with scientific images, it has grown to encompass all aspects of science and their impact on everyday life.
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If you're not happy with a purchase that you made on FineArtAmerica.com, for any reason, you can return it to us within 30 days of the order date. As soon as it arrives, we'll issue a full refund for the entire purchase price. Please note - Fine Art America does not reimburse the outgoing or return shipping charges unless the return is due to a defect in quality.