The Future of Physics Is Undetermined

The world of classical physics is one described by precision, whilst the quantum domain seems marked by true randomness. Should classical physics be revised to include the possibility of chance?

There are many factors that divide classical physics and quantum physics. The behavior of particles, the concept that information can pass between particles faster than light, the wave/particle duality nature of matter and light, being just a few examples, but there is one crucial and striking difference that underlies the divide between the two disciplines. Whilst classical physics is deterministic — repeat the same experiment under the same conditions and you will achieve the same results — at the heart of quantum mechanics lies true randomness.

Quantum physics is indeterministic, the results of experiments can only be described with probabilities, not with certain predictions. The idea of this random foundation troubled Albert Einstein until his death, leading him to famously remark:

“ God does not play dice with the universe”

in reference to his belief that quantum mechanics must be an incomplete theory. He believed that there must be “hidden variables” which when uncovered would make the outcomes of quantum mechanics determinable.

Time has proved the Austrian physicist wrong. A century of experimentation with quantum principles investigating the minutiae of the discipline has failed to turn-up hidden variables. There is no missing information. On the smallest scale, the universe, it seems, is truly random.

This leads us to ask, how then do we delineate quantum and classical physics? Where is the dividing line at which the universe and its interactions become determinable?

Nicolas Gisin, professor emeritus at the University of Geneva who has spent his professional life investigating the foundations of quantum mechanics, has a startling answer to these questions. In a paper published in Nature, he maintains that it is classical physics that should be altered to conform with the quantum. Gisin believes that all physics has at its core true randomness.

“Everyone tries to make quantum theory look more like classical physics,” Gisin says. “ I believe we’ll learn more by making classical physics look more like quantum, in particular with some indeterminism.”

If it ain’t broke, why fix it?

The world of classical or Newtonian physics is built around the idea that given a particular set of starting conditions, we could in principle, calculate the evolution of the universe from beginning to end. This means with the initial conditions of the big bang and the correct equations all things should be predictable. There should be no room for chance.

Yet, our day-to-day experience and very intuition seem to reject the idea of that everything in the universe has been predicted in advance.

“The idea that everything was settled at the big-bang is bizarre, it is too fine-tuned,” Gisin says. “This is too far from our experience.”

The equations of classical physics suggest that every event since the big bang could be predicted given the correct starting conditions. But the addition of a new mathematical language could reintroduce the idea of indeterminism to physics (MIT)

Gisin isn’t the first physicist to take issue with the totally deterministic nature of classical physics. Notable physicists such as Boltzmann, Exner, Schrodinger, and Born all argued that Newtonian physics needed to be expanded to include genuine indeterminism — albeit from very different perspectives. The latter of these great scientists were intrinsically involved in the development of quantum physics, which no doubt influenced and bolstered their support for an indeterministic element.

Gisin says he has not experienced as much resistance to this revision as one may expect:

“Interestingly, when discussing my ideas with colleagues, I find it pretty easy to convince physicists, but more difficult with philosophers, especially philosophers of science.”

The researcher also points out that alterations to fundamental equations that he proposes, do nothing to undermine the awesome predictive power of Newton and Maxwell’s theories:

“Introducing randomness to classical physics the way I do it doesn’t affect prediction made by classical theory. Its value is conceptual: the same huge empirical evidence can be interpreted in a deterministic and an indeterministic theory.”

Gisin has more than just counterintuition forming his justification in revising physics, of course. Were that adequate reason for rethinking a discipline then it would likely be the deeply counterintuitive rules of quantum physics that would spark such a revision first.

To support his proposed revision, Gisin points to a fundamental issue with the mathematics used to describe classical physics; how can the infinite information contained within an infinite never-ending number such as pi ‘fit’ within a finite universe?

The infinite within the finite

The equations that describe the initial conditions of the universe depend on a language comprised of classical mathematics and ‘real numbers.’

“These numbers are characterised by an infinite number of decimals that follow the dot,” Gisin explains. “This implies they contain an infinite amount of information.”

Such real numbers — accepted as a postulate in maths — are far more numerous than named numbers like pi and e and are frequently encountered within the equations of physics, but not within ‘everyday life.’

How does the infinite information represented by some real numbers such as pi ‘fit’ into a finite universe?

Gisin negates the impossibility of fitting an infinite amount of information within a finite world, Gisin suggests that the classical mathematical language of Newtonian physics should be changed. He puts forward a numerical system that does not depend on real numbers.

“There is another mathematical language called intuitionistic maths that doesn't believe in the infinite,” Gisin says. “It was completely crushed by the language of classical mathematics at the beginning of the twentieth century.”

To do away with real numbers and infinite digits following a decimal point at any given point in time, intuitionistic maths represents these numbers as a random process that occurs over time, one decimal following another. Thus, at any given moment there is only a finite number of decimals and a finite amount of information.

“In classical mathematics, every number is given at once, including the infinite number of decimals of typical real numbers,” Gisin explains. “In contrast, in intuitionistic mathematics numbers are processes that develop in time one after the other in such a way that at each instance there is only finite information. “The equations don’t change. It is only the initial conditions that would no longer be represented by ‘infinite information’ real numbers, but by ‘finite information’ intuitionistic numbers.”

This, therefore, solves the problem of infinite information in a finite universe. But, intuitionistic maths introduces another concept to physics — indeterminacy.

True or false… or indetermined?

Another aspect intuitionistic maths that differs from classical maths are the possible values of a proposition. In classical maths, a proposition is determined as ‘true or false’ according to the law of the excluded middle. Contrary to this, intuitionistic maths offers a third option. A proposition can be found ‘true, false or indeterminate.’

“So there is an accepted part of indeterminacy,” explains Gisin.

Not only does this bring physics closer to our everyday experience, Gisin believes, but it also compliments the randomness found in quantum mechanics.

“Some people endeavour to avoid it at all costs by involving other variables based on real numbers,” the physicist says. “But in my opinion, we shouldn’t try to bring quantum physic closer to classical physics by eliminating randomness. “Quite the opposite; we must bring classical physics closer to quantum physics by finally incorporating indeterminacy.”

Gisin believes that choosing to base physics on intuitionistic maths will remove determinacy that was unnecessary in classical physics and open up future discoveries. All without calling into question the utility of the discipline or its achievements.

“This change in language wouldn’t change the results of research conducted to date but it would make it easier to understand quantum physics and eventually to abandon a worldview where everything is already written,” Gisin concludes. “This makes room for new perspectives, randomness, chance and creativity.”