By Vijay Damodharan - Natural Sciences Student @ Christ College, Cambridge
People sometimes play basketball, football, or table tennis using a wall as their opponent. It may be for practice, or just out of boredom. When the ball strikes the wall, it dutifully returns the ball back to us. But what if it didn’t? What if the ball passed straight through? It seems like an absurd question to ask; however, it occurs more often than one might think in quantum mechanics.