It has been evident since long that if our physical constants have been slightly different then the life on the Earth would not have been possible. Why the physical constants have the value they have, or what made it that physical constants have such values to make life possible in this universe. Moreover, the overall chemical composition of the universe was determined by the physical conditions during the first few seconds of the Big Bang. For example, the elements on which life depends such as Carbon, nitrogen, oxygen and Iron are the products of nuclear fusion reactions within the stars if the initial condition would have been different from formation of stars; nuclear fusion and supernova which distributed these would not have been possible. Also the processes by which the chemical elements are formed are governed very precisely by the strengths of four fundamental physical interactions: gravitation, electromagnetism, weak and strong nuclear interactions. If the relative strengths of these forces were different, the resultant universe would have been different. For example, increasing the strong nuclear interaction by 3 % relative to electromagnetic interaction gives a cosmological model in which none of the known chemical elements could have been formed. Conversely, decreasing it by just 1 % gives a model in which Carbon atoms would be highly unstable. Both scenarios would preclude carbon-based life. Other tiny variation in these forces might have given rise to a universe which contained 100 % helium or one in which supernova explosion could not occur (since these explosions are though to be chief way in which the chemicals necessary for life are ejected from stars), these scenario too preclude the evolution of life. These ‘precisions’ in the various parameters, such as to give rise to life, are known as the ‘Anthropic coincidences’.
http://www.hssrd.org/journal/spring2...ionunverse.htm
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