David Eagleman of the Baylor College of Medicine demonstrated that we are all living in the past by using several visual illusions to prove the point. One of them is the flash-lag effect. A light flashes when an object moves past it, but we don’t see the two as coincident; there appears to be a slight delay between the two events.
Our consciousness lags 80 milliseconds behind actual events. “When you think an event occurs it has already happened,” Eagleman said. The reason is because our brains try to reconstruct events that happen and stimuli that occur at different times, in a cohesive way so that we can have a cohesive picture of the world around us.
But sometimes the brain just can’t wait. If a hand-clapper is less than 30 meters away, you hear and see the clap happen simultaneously, but one meter further and the sound arrives more than 80 milliseconds later than the light, and the brain no longer matches what you see and hear.