Time to rethink physics?
In his new book the theoretical physicist Lee Smolin calls for a major shift in the discipline and a recognition that rather than a relative value or an effect of space, time is real and fundamental. Marcus Chown explains
Here is a peculiar thing. Most people think time exists. Most physicists think it does not. Now a prominent American-Canadian physicist is maintaining that we, who never doubted it, were right after all. “It’s time to reinstate time,” says Lee Smolin of the Perimeter Institute in Waterloo, Ontario. “By doing so, we will remove a major roadblock preventing progress in fundamental physics.”
No doubt you are confused that physicists think there is no time when it seems so central a part of our everyday experience. It all goes back to Newton. He found that, miraculously, nature appears to obey mathematical laws. His laws of motion, for instance, are a perfect analogue of actual motion. In other words, motion can be taken from the real world and captured in a formula. Such an “equation” can be graphed to show, for instance, the trajectory of a ball through the air. Not only does the trajectory then exist on paper, frozen in space rather than in time, the equation itself is a statement of logical truth, which is true in perpetuity – that is, outside of time.
For a long time after Newton physicists appeared not to notice or worry that they had banished time from their description of the world. Things came to a head, however, with Einstein. In 1905, he showed that what one person sees as an interval of time another sees as an interval of time and space; and what one person sees as an interval of space, another sees as an interval of space and time. It all depends on how fast the people are moving relative to each other (although, for a noticeable effect, they must be moving at an appreciable fraction of the speed of light – 300,000 kilometres a second). Time and space, it turns out, are interchangeable, mere aspects of a seamless entity: space-time.
“Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality,” said Einstein’s ex-mathematics professor Hermann Minkowski.
Time having the character of space means that, instead of us living in three dimensions of space and one of time, we in fact live in four dimensions of space-time. We can imagine all of space-time, from the Big Bang to the end of the universe, as a 4D map, with every location in space-time laid out just as on a map of Britain, preordained, simultaneous. There is no place for time. This inspired Einstein, on the death of his long-time friend Michele Besso, to write to his family: “Now Besso has departed from this strange world a little ahead of me. That means nothing. People like us … know that the distinction between past, present and future is only a stubbornly persistent illusion.” (It is not recorded whether the family was consoled!)
Banishing time from physics, however, causes many problems. “With timeless laws in timeless space, some questions are unanswerable,” says Smolin. “What, for instance, chooses the laws? Why are they the way they are?” This will be particularly vexing if we ever find the “Theory of Everything”. This Holy Grail of physics will describe all physical phenomena in a compact set of equations that will fit on the back of a stamp (or at least an envelope). “If we get the TOE, we will still be left with the question: why this set of equations and not another set?” says Smolin.
The fundamental problem is that if we banish the laws of physics to some timeless mathematical realm, we are logically removing any possibility of knowing their origin. Smolin’s radical solution, spelled out in his new book, Time Reborn, is to bring physics back into the real world. “Instead of viewing the laws as acting outside of time, we must view them as acting in time – that is, only at this moment,” says Smolin. “Suddenly, the laws will be free to change, to evolve in time.”
This idea of evolving laws was actually anticipated by American philosopher Charles Sanders Peirce in 1893. Everything in the universe changes, or evolves, he maintained. Why should the laws of physics be exempted? “The only way in which we can explain the laws of nature is to attribute them to evolution, and this evolutionary story suggests that the world has become steadily more law-governed through time,” said Peirce.
In fact, Smolin is famous for postulating one way in which the laws of physics might evolve. In his 1997 bestseller The Life of the Cosmos, he imagined black holes spawning baby universes. Those universes in which the laws of physics maximise the production of black holes will then have the most babies and propagate themselves, dominating in number all other universes. We should therefore find ourselves in such a universe. Smolin even made a prediction about the maximum mass of a “neutron star”, a compact object whose overproduction in supernova explosions would cause an underproduction of black holes.
“We will never find a neutron star bigger than twice the mass of the Sun,” says Smolin. “So far, the prediction has been borne out.”
Interestingly, the shrinkage of interstellar gas clouds to make the massive stars that spawn black holes in supernovae is enhanced by molecules of carbon monoxide (CO). So a universe that maximises the number of black holes also maximises the amount of carbon and oxygen, two crucial elements for biology. “My mechanism automatically maximises the number of life-bearing universes,” says Smolin.
If the laws of physics do evolve in time, then suddenly it is possible to ask formerly unanswerable questions like: Where do they come from? “The laws might start out random and then evolve,” says Smolin. “Or maybe there is a meta-law that guides the evolution of laws.” He admits that the latter possibility might lead to the question Where does the meta-law come from? and an infinite regress.
If time is reinstated it might also be possible to resolve several dilemmas in physics. Although the fundamental laws are reversible – the law of gravity equally well permits the Earth to orbit the Sun in the opposite direction – the everyday world is not time-reversible. When did you last see a cup unbreak or a person grow young? Conventional physics can square the circle only if the Big Bang was a highly improbable “low entropy” event. But the whole point of physics is to find general explanations, not appeal to highly improbable events. Smolin and his colleague Marina Cortes at the University of Edinburgh believe that, if time is reinstated in physics, the laws we have observed may hide a deeper level of laws. “And those laws may be time-asymmetric,” says Smolin.
Smolin, in a nutshell, is proposing that time should merely reflect our basic experience of reality – that there is a present moment and that time passes as we think it does. Arguably, he could not have come to such a radical view if not at the Perimeter Institute, of which he is one of the founders. Perimeter was set up on the back of a CAN$120 million donation from Waterloo resident and billionaire Mike Lazarides, the man behind the Blackberry. Its aim, according to its director Neil Turok, is to unite the two big ideas in physics, relativity and quantum theory, into one Theory of Everythjing within the next 10 years. “Our existence will be justified by a single paper that will come out of Perimeter and revolutionise science,” says Smolin.
Perimeter has a beguilingly simple strategy: get together interesting people – Stephen Hawking has a visiting research chair – and maximise the chance of them interacting. Between every half-dozen offices are coffee stations with sofas, whiteboards and wood-burning stoves (winters in Ontario are cold). “We are encouraged to think boldly,” says Smolin. “We are supported in breaking new ground.”
The reinstatement of time, Smolin believes, has implications also for our daily lives. “If the flow of time is not an illusion, it makes our lives more precious and valuable,” he says. On the surface, this might not be as consoling as Einstein’s view that death does not have the finality we think it does. However, Smolin points out that the “Newtonian paradigm” removes all free will. If, as the Greek philosopher Democritus once said – “In reality there are only atoms and the void” – then nothing ever happens in the universe except the rearrangement of atoms. How the atoms of the universe arrange themselves is predictable because the laws that govern the forces between them – Newton’s laws of motion – are predictable.
“There is no novelty, everything is computable,” says Smolin. Or, as Tom Stoppard puts it in his play Arcadia: “If you could stop every atom in its position and direction, and if your mind could comprehend all the actions thus suspended, then if you were really, really good at algebra you could write the formula for all the future; and although nobody can be so clever to do it, the formula must exist just as if one could.”
If the laws of physics can change and evolve, however, so too can the “the space of possible futures”, says Smolin. Nature can create new things. “The impression that we have that we can create novelty is true,” says Smolin. “This makes the universe much more hospitable. We can have free will. We have choices. I find that a much more comforting idea.”
Time Reborn: From the Crisis in Physics to the Future of the Universe by Lee Smolin is published by Allen Lane