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Inconstant sun: how solar evolution has affected cosmic and ultraviolet radiation exposure over the history of life

P Andrew Karam1

  • 1University of Rochester, Department of Environmental Medicine, 601 Elmwood Avenue, Box HPH, Rochester, NY 14642, USA. Andrew_Karam@URMC.Rochester.edu

Health Physics
|March 21, 2003
PubMed

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Scientists record evolutionary history by analyzing fossil, morphological, and genetic data. The fossil record documents the history of life on Earth and provides evidence for evolution. However, both fossil and living organisms offer evidence that outlines Earth’s evolutionary history.Phylogenetic trees illustrate the evolutionary relationships among these organisms. Scientists infer organisms’ common ancestry by evaluating shared morphological and genetic characteristics. Together, the fossil...
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The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process called fusion. The principal source of energy in the sun is a net fusion reaction in which four hydrogen nuclei fuse and ultimately produce one helium nucleus and two positrons.
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