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The fraction of the mass of two hydrogen atoms that is released as energy when they fuse to produce helium is 0.007 (0.7%). That is the source of the heat produced in the sun and in a hydrogen bomb.
It is the amount of mass (m) that is converted to energy (E) in the famous Einstein formula E = mc2, and it is a direct measure of the
strong nuclear force. If the strong force had a value of 0.006 or less, the universe would consist only of hydrogen—not very conducive
to the complexities of life. If the value were greater than 0.008, all the hydrogen would have been fused shortly after the big bang, and there could be no stars, no solar heat—again, no life.
As Stephen Hawking and Leonard Mlodinow put it in their book The Grand Design, “Our universe and its laws appear to have a design that both is tailor-made to support us and, if we are to exist,
leaves little room for alteration.
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