Brush up your mathematics or physics skills with Brilliant! Start learning for free at https://brilliant.org/sabine/ and get 20% off a premium subscription, which includes daily unlimited access! Can two different theories of physics both accurately explain the same phenomenon? The answer in some cases is yes. In physics, this is called a duality, and it raises the question of why we choose one theory over another. What even is reality if we can use multiple different theories to describe it?