ys > “six feet” rule was based on
it is based on physics – propagation of large debris that get out of the mouth/nose. There are tons of simulators and tests for that. This is remarkably same as our traditional four amot! 6ft = 1.8m, 4 0.5m amot = 2m. Europeans are using 2 meters for covid rather than 6 ft. So, it looks lkike physics of breathing did not change in thousand years and was accurately measured!
ps 6 ft is for large particles that go down reasonably quickly, this is separate from aerosol that accumulate in the air.