Isaac Newton thought of time as a river flowing at the same rate everywhere. Albert Einstein unified space and time into a single entity, but he still held on to the concept of time as a measure of change. In Barbour’s view there is no invisible river of time. Instead, he thinks that change merely creates an illusion of time, with each individual moment existing in its own right, complete and whole. He calls these moments “Nows.”
“As we live, we seem to move through a succession of Nows. The question is, what are they?” Barbour asks. His answer: Each Now is an arrangement of everything in the universe. “We have the strong impression that things have definite positions relative to each other. I aim to abstract away everything we cannot see, directly or indirectly, and simply keep this idea of many different things coexisting at once. There are simply the Nows, nothing more and nothing less.”
Barbour’s Nows can be imagined as pages of a novel ripped from the book’s spine and tossed randomly onto the floor. Each page is a separate entity. Arranging the pages in some special order and moving through them step by step makes it seem that a story is unfolding. Even so, no matter how we arrange the sheets, each page is complete and independent. For Barbour, reality is just the physics of these Nows taken together as a whole.
“What really intrigues me is that the totality of all possible Nows has a very special structure,” he says. “You can think of it as a landscape or country. Each point in this country is a Now, and I call the country Platonia,” in reference to Plato’s conception of a deeper reality, “because it is timeless and created by perfect mathematical rules. Platonia is the true arena of the universe.”
In Platonia all possible configurations of the universe, every possible location of every atom, exist simultaneously. There is no past moment that flows into a future moment; the question of what came before the Big Bang never arises because Barbour’s cosmology has no time. The Big Bang is not an event in the distant past; it is just one special place in Platonia.
Our illusion of the past comes because each Now in Platonia contains objects that appear as “records,” in Barbour’s language. “The only evidence you have of last week is your memory—but memory comes from a stable structure of neurons in your brain now. The only evidence we have of the earth’s past are rocks and fossils—but these are just stable structures in the form of an arrangement of minerals we examine in the present. All we have are these records, and we only have them in this Now,” Barbour says. In his theory, some Nows are linked to others in Platonia’s landscape even though they all exist simultaneously. Those links create the appearance of a sequence from past to future, but there is no actual flow of time from one Now to another.
“Think of the integers,” Barbour says. “Every integer exists simultaneously. But some of the integers are linked in structure, like the set of all primes or the numbers you get from the Fibonacci series.” Yet the number 3 does not occur in the past of the number 5 any more than the Big Bang exists in the past of the year 2008.
These ideas might sound like the stuff of late-night dorm-room conversations, but Barbour has spent four decades hammering them out in the hard language of mathematical physics (pdf). He has blended Platonia with the equations of quantum mechanics to devise a mathematical description of a “changeless” physics. With Irish collaborator Niall Ó Murchadha of the National University of Ireland in Cork, Barbour is continuing to reformulate a time-free version of Einstein’s theory.
So What Really Happened?
For each of the alternatives to the Big Bang, it is easier to demonstrate the appeal of the idea than to prove that it is correct. Steinhardt and Turok’s cyclic cosmology can account for critical pieces of evidence usually cited to support the Big Bang, but the experiments that could put it over the top are decades away. Carroll’s model of the multiverse depends on a speculative interpretation of inflationary cosmology, which is itself only loosely verified.
Barbour stands at the farthest extreme. He has no way to test his concept of Platonia. The power of his ideas rests heavily on the beauty of their formulation and on their capacity to unify physics. “What we are working out now is simple and coherent,” Barbour says, “and because of that I believe it is showing us something fundamental.”
The payoff that Barbour offers is not just a mathematical solution but a philosophical one. In place of all the conflicting notions about the Big Bang and what came before, he offers a way out. He proposes letting go of the past—of the whole idea of the past—and living fully, happily, in the Now.
In one model, each round of existence stretches a trillion years. By that reckoning, our universe is still in its infancy.
