The majority of Quantum Gravitists agree that the unified theory will get rid of space and time. But what does this mean? Does it mean letting a classical spacetime emerge from a summation over quantum geometries, such as spin foam graphs? No, of course not. It means removing space from one's conception of the cosmos
. When we observe binary pulsars
for example, we should not imagine this object occupying a concrete objective classical spacetime out there. Even a traditional dynamical spacetime is completely inadequate
. Quantum physics has taught us that a good way to approach a physical problem is to consider what we measure
. One must be much more careful about the constraints one puts upon different classes of observation. If we wish to 'observe' the universe, we must define what we mean by this so that we are able to write down the correct geometry for this experiment.
People speak of holography in terms of data on a boundary. Where
is this boundary? With respect to what may I position it? The best I
can do is try to imagine that it is within myself.