счастливая случайность
• Since Rutherford did not know that quantum mechanics governed his scattering experiment, it is (only) a happy accident that his formula correctly describes low-energy scattering.
Русско-английский научно-технический словарь• Since Rutherford did not know that quantum mechanics governed his scattering experiment, it is (only) a happy accident that his formula correctly describes low-energy scattering.
Русско-английский научно-технический словарь