Time Travel. A History

For space, the deeper reality is the network of relationships among all the entities that fill it. Things are related to other things; they are connected, and it is the relationships that define space rather than the other way around. This is not a new perspective. It goes back at least to Newton’s great rival Leibniz, who refused to accept the view of time and space as containers in which everything is situated—an absolute background for the universe. He preferred to treat them as relations between objects: “Space is nothing else, but That Order or Relation; and is nothing at all without Bodies, but the Possibility of placing them.” Empty space is not space at all, Leibniz would say, nor would time exist in an empty universe, because time is the measure of change. “I hold space to be something merely relative, as time is,” wrote Leibniz. “Instants, considered without the things, are nothing at all.” With the triumph of the Newtonian program, Leibniz’s view almost faded from view.

To appreciate the network-centered, relational view of space, we need look no further than the connected, digital world. The internet, like the telegraph a century before, is commonly said to “annihilate” space. It does this by making neighbors of the most distant nodes in a network that transcends physical dimension. Instead of six degrees of separation we have billions of degrees of connectedness. As Smolin put it:

We live in a world in which technology has trumped the limitations inherent in living in a low-dimensional space….From a cell-phone perspective, we live in a 2.5 billion–dimensional space, in which very nearly all our fellow humans are our nearest neighbors. The Internet, of course has done the same thing. The space separating us has been dissolved by a network of connections.

So maybe it’s easier now for us to see how things really are. This is what Smolin believes: that time is fundamental but space an illusion; “that the real relationships that form the world are a dynamical network”; and that the network itself, along with everything in it, can and must evolve over time.

He presents a program for further study, based on a notion of “preferred global time” that extends throughout the universe and defines a boundary between past and future. It imagines a family of observers, spread throughout the universe, and a preferred state of rest, against which motion can be measured. Even if “now” need not be the same to different observers, it retains its meaning for the cosmos. These observers, with their persistent sense of a present moment, are a problem to be investigated, rather than set aside.

The universe does what it does. We perceive change, perceive motion, and try to make sense of the teeming, blooming confusion. The hard problem, in other words, is consciousness. We’re back where we started, with Wells’s Time Traveller, insisting that the only difference between time and space is that “our consciousness moves along it,” just before Einstein and Minkowski said the same. Physicists have developed a love-hate relationship with the problem of the self. On the one hand it’s none of their business—leave it to the (mere) psychologists. On the other hand, trying to extricate the observer—the measurer, the accumulator of information—from the cool description of nature has turned out to be impossible. Our consciousness is not some magical onlooker; it is a part of the universe it tries to contemplate.

The mind is what we experience most immediately and what does the experiencing. It is subject to the arrow of time. It creates memories as it goes. It models the world and continually compares these models with their predecessors. Whatever consciousness will turn out to be, it’s not a moving flashlight illuminating successive slices of the four-dimensional space-time continuum. It is a dynamical system, occurring in time, evolving in time, able to absorb bits of information from the past and process them, and able as well to create anticipation for the future.