Simplify the following text for a Grade 15 native English-speaking person.
Original: The term Copenhagen interpretation of quantum mechanics was often used interchangeably with and as a synonym for Heisenberg 's Uncertainty Principle by detractors who believed in fate and determinism and saw the common features of the Bohr-Heisenberg theories as a threat .
Simplified: The Copenhagen interpretation of quantum mechanics and Heisenberg 's Uncertainty Principle were in fact seen as twin targets by detractors who believed in an underlying determinism and realism .