The Holographic Universe.

Juan Maldacena

Discoverer of the 

AdS/CFT correspondence.

The New York Times wrote recently on the Holographic Universe, something that the truly great PBS Space Time has visited as a topic repeatedly. The interesting point is always, for me, that the information content of any three-dimensional space is limited to the number of bits that can be encoded on an imaginary surface surrounding it, and that limit is defined by the Planck length. The consequences of this are mind-bending.  

"'It's completely crazy,' [says Leonard Susskind], in reference to the holographic universe. 'You could imagine in a laboratory, in a sufficiently advanced laboratory, a large sphere — let’s say, a hollow sphere of a specially tailored material — to be made of silicon and other things, with some kind of appropriate quantum fields inscribed on it.' Then you could conduct experiments, he said: 'Tap on the sphere, interact with it, then wait for answers from the entities inside ... [o]n the other hand, you could open up that shell and you would find nothing in it,' he added. As for us entities inside: 'We don’t read the hologram, we are the hologram.'"

Wikipedia has a dense, but good article on the same subject. This also leads to the AdS/CFT correspondence, which really makes a lot more sense after watching this video from Matt O'Dowd.