**Cosmic Gateway**

Generation Details

Model

Flux Pro

Prompt

In its present form, quantum mechanics only predicts statistical averages for the outcomes of many kinds of experiments, including these. Consequently, it is not possible to use the nonlocality present in entangled pairs to send a signal faster than light. But many physicists, in an ambition going back to Einstein, de Brgolie, Schrödinger and the other inventors of quantum mechanics, aspire to discover an improved version of quantum theory. This would go deeper and replace the present statistical theory with a more complete theory, which would provide a complete and exact description of what goes on in every individual quantum process. For such a theory to work, it would have to be based on influences traveling arbitrarily faster than light, thus destroying the principle of relativistic causality as well as our intuitive notions of local influence. Is such a more complete understanding of quantum physics possible? And, how are we to search for it? I believe it is not only possible but an inevitable next step in the progress of physics. I believe that the completion of quantum mechanics will be a major part of the resolution of another deep problem—that of unifying our understandings of gravity, spacetime and the quantum, to produce a quantum theory of gravity. The reason is that there is good evidence that the quantum theory of gravity will itself engender big violations of locality. And, as Fotini Markopoulou and I first proposed in 2003, the violations of locality forced on us by quantum gravity are precisely what are needed to explain the nonlocality brought on by quantum entanglement. If we are to have a complete physics, we must unify the geometrical picture of spacetime given by general relativity with quantum physics. There is some theoretical evidence that this project of making a quantum theory of gravity will require space and spacetime to become discrete and built out of finite atoms of geometry. In the same sense that a liquid is just a description of the collective motions of myriads of atoms, space and spacetime will turn out to be just a way of talking about the collective properties of the large number of atomic events. Their constant coming in and out of being, causing the next ones as they recede into the past, make up the continual construction of the world—also known to us as the flow of time. The aim of a quantum theory of gravity is then first to hypothesize the laws that govern the elementary events, by which they continually come into being and then recede into the past. Then we must show how a large-scale picture emerges, in which these discrete events become subsumed in an emergent description of a smooth and continuous spacetime—as described by Einstein’s 1915 general theory of relativity. Initially there is no space—just a network of individual elementary events, together with the relations expressing which of these were the direct causes of which other events. The notion of the flow of events collectively giving rise to a smooth description in terms of the geometry of a spacetime must emerge—and the most important aspect of this is locality. The notion of distance must emerge, and in such a way that those events that are close to each other are, on average, correspondingly more likely to have influenced each other. Getting this right is the holy grail of quantum gravity theorists. Notice that if this is right, there are two notions of locality: a fundamental locality, which is based on the actual facts of which fundamental events were causes of which, and an approximate, collective, emergent notion of which events are near to each other in space and spacetime. The familiar macroscopic notion of distance is then based on a collective averaging of all the myriad of fundamental causal processes. To get a sense of how much is involved in this average, we expect that during each second there are around 10120 elementary events happening within each cubic centimeter of space. Indeed, one way to approach quantum gravity is to aim to derive the Einstein equations, which are the laws general relativity applies to spacetime, from the laws of thermodynamics, applied to myriads of elementary events. This strategy was introduced by Ted Jacobson in 1995 in one of the few papers admired by quantum gravity theorists of all stripes But here we get a surprise and, quite possibly, an opportunity. For the collective, large-scale notion of nearness is only meant to correspond to the fundamental notion of causality when averaged over vast numbers of events. This gives the individual fundamental events and their causal relations a great deal of freedom to depart from the averages.

Resolution

720x1080

Description

Creator

PixelDojo User

Engagement