If we instantly forgot everything known about gravity, and even forgot calculus, but we kept the existing economic infrastructure of science and math—computers, professional mathematicians of roughly equivalent skill level who happen not to know calculus, billions of dollars a year in R&D funding, etc. - then calculus would be discovered in a month (though it wouldn’t be rigorous), Newton’s laws a week later, and Einstein’s general relativity before the year was out. That’s seriously my best estimate for how long it would take.
If we instantly forgot everything known about gravity, and even forgot calculus, but we kept the existing economic infrastructure of science and math—computers, professional mathematicians of roughly equivalent skill level who happen not to know calculus, billions of dollars a year in R&D funding, etc. - then calculus would be discovered in a month (though it wouldn’t be rigorous), Newton’s laws a week later, and Einstein’s general relativity before the year was out. That’s seriously my best estimate for how long it would take.