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Certain physical constants, like the mass of an electron or the gravitational constant, are not determined by physical theory. Rather, physicists must determine them empirically. However, in case after case, physicists have also found that these constants fit within a narrow range of possible values that allow life to exist in our universe. Tweak them even slightly, and the universe becomes incapable...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.