More evidence, if we needed it, that eyewitness testimony isn't as reliable as we thought. According to scientists at the University of Edinburgh, "[P]eople looking at pictures often failed to detect deliberate alterations, such as objects becoming bigger or disappearing. Professor John Henderson of the School of Philosophy, Psychology and Language Sciences said: 'We think our eyes show us the world in sharp detail all the time, but in fact this is not the case. "Our studies show that our eyes do, in fact, miss a great deal. Our research gives us insight into how people see the world and ultimately how the brain processes information.'" BBC1's program Bang Goes the Theory highlighted the research.
And Abracadabra! That's how David Copperfield disappears.
For more from Dr. Henderson, see also Peter Lamont and John Henderson, Correspondence: More attention and greater awareness in the scientific study of magic, Nature Reviews Neuroscience 10, 241 (March 2009), in response to Stephen L. Macknik, Mac King, James Randi, Apollo Robbins, Teller, John Thompson & Susana Martinez-Conde, Science and society: Attention and awareness in stage magic: turning tricks into research, Nature Reviews Neuroscience 9, 871-879 (November 2008).