““Many of the important principles in twentieth century physics are expressed as limitations on what we can know. Einstein's principle of relativity (which was an extension of a principle of Galileo's) says that we cannot do any experiment that would distinguish being at rest from moving at a constant velocity. Heisenberg's uncertainty principle tells us that we cannot know both the position and momentum of a particle to arbitrary accuracy. This new limitation tells us there is an absolute bound to the information available to us about what is contained on the other side of a horizon. It is known as Bekenstein's bound, as it was discussed in papers Jacob Bekenstein wrote in the 1970s shortly after he discovered the entropy of black holes.””
