Quantum Nonlocality (video)
I've uploaded another video: https://youtu.be/ZYAeuGuqtTM
TL;DW: There are certain possible situations in which an event at one location can have an instantaneous effect on what happens at a distant location outside the first event's light cone, so there is 'faster-than-light causal influence'. This is implied by the empirical predictions of quantum mechanics, as shown by Bell's Theorem. Those predictions have been experimentally verified. So nonlocality is true.
The scenarios involve cases where a pair of particles are in an "entangled" state, such that the outcome of a measurement the particles cannot be predicted, but it can be known in advance that, however each particle comes out, the other particle will have an opposite property (e.g., one spin up, the other spin down).
This phenomenon might mean that Relativity is false.