# Eddington number

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The Eddington number is $$N_\text{Edd} = 136 \cdot 2^{256} \approx 1.575 \times 10^{79}$$, which Arthur Eddington asserted to be the exact number of protons in the observable universe.[1] 136 is the reciprocal of the fine structure constant, or at least the best available estimation at the time. It is now known to be about $$1/137.035999074$$; Eddington's original value, if not his whole argument, is incorrect.

Its full decimal expansion is

15747724136275002577605653961181555468044717914527116709366231425076185631031296

1. [1]