Regarding waves and interference, have a look at this video: https://www.youtube.com/watch?v=TshYfYIxR9E https://www.youtube.com/watch?v=TshYfYIxR9E. It shows h

Regarding waves and interference, have a look at this video: https://www.youtube.com/watch?v=TshYfYIxR9E https://www.youtube.com/watch?v=TshYfYIxR9E. It shows how the interference patterns actually look. Yes, the wave is 3D and the interference patterns can be kind of like checker board. We are usually considering a 2D example because it is simpler to visualize and analize. > how do we know that entanglement is the result of 'spooky action at a distance' and not the result of creating two entangled particles? A very high-level explanation is that we know this because quantum computers work (even though right now we can't build them big enough to be useful) and it can't be explained by any classical effects.