What was the significance of the Manhattan Project to society?

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Kaboom, the friendly atomic bomb.
Followed by 60 years of world wide fear of it.

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plus the atomic pile (self-staining chain reaction) – hence nuclear power, which we now badly need!

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Developed a weapon that:
1) killed a couple hundred thousand people
2) ended the war early, thereby saving a couple hundred thousand people per month it might have otherwise continued
3) maintained an uneasy peace between the superpowers for 50 years

Layed the framework for atomic energy

Like any big science project, I’m sure it had secondary technological spinoffs–advances in metallurgy and mechanical computing among others.