Dropping Schrödinger's Cat Into a Black Hole
Combining gravity with the process that transforms the fuzzy uncertainty of the quantum realm into the definite classical world we see around us could lead to a theory of quantum gravity.
A radical reformulation of quantum mechanics suggests that the universe has a set destiny and its pre-existing fate reaches back in time to influence the past. It could explain the origin of life, dark energy and solve other cosmic conundrums.
by Julie Rehmeyer
August 21, 2011
Paul Davies Arizona State University
The universe has a destiny—and this set fate could be reaching backwards in time and combining with influences from the past to shape the present. It’s a mind-bending claim, but some cosmologists now believe that a radical reformulation of quantum mechanics in which the future can affect the past could solve some of the universe’s biggest mysteries, including how life arose. What’s more, the researchers claim that recent lab experiments are dramatically confirming the concepts underpinning this reformulation.
Cosmologist Paul Davies, at Arizona State University in Tempe, is embarking on a project to investigate the future’s reach into the present, with the help of a $70,000 grant from the Foundational Questions Institute. It is a project that has been brewing for more than 30 years, since Davies first heard of attempts by physicist Yakir Aharonov to get to root of some of the paradoxes of quantum mechanics. One of these is the theory’s apparent indeterminism: You cannot predict the outcome of experiments on a quantum particle precisely; perform exactly the same experiment on two identical particles and you will get two different results.
While most physicists faced with this have concluded that reality is fundamentally, deeply random, Aharonov argues that there is order hidden within the uncertainty. But to understand its source requires a leap of imagination that takes us beyond our traditional view of time and causality. In his radical reinterpretation of quantum mechanics, Aharonov argues that two seemingly identical particles behave differently under the same conditions because they are fundamentally different. We just do not appreciate this difference in the present because it can only be revealed by experiments carried out in the future.
"It’s a very, very profound idea," says Davies. Aharonov’s take on quantum mechanics can explain all the usual results that the conventional interpretations can, but with the added bonus that it also explains away nature’s apparent indeterminism. What’s more, a theory in which the future can influence the past may have huge—and much needed—repercussions for our understanding of the universe, says Davies.
In the video below, Davies’ collaborator, Jeff Tollaksen of Chapman University, California, describes the alternative approach to quantum mechanics in more detail:
Cosmologists studying the conditions of the early universe have been puzzling about why the cosmos seems so ideally suited for life. There are other mysteries too: Why is the expansion of the universe speeding up? What is the origin of the magnetic fields seen in galaxies? And why do some cosmic rays appear to have impossibly high energies? These questions cannot be answered just by looking at the past conditions of the universe. But perhaps, Davies ponders, if the cosmos has set final conditions in place—a destiny—then this, combined with the influence of the initial conditions set out at the beginning of the universe, might together perfectly explain these cosmic conundrums.
Testing Time’s Arrow
It’s a nice—if extremely strange—idea. But is there any way to check its feasibility? Given that it invokes a future that we do not yet have access to as a partial cause of the present, this seems like an impossible task. However, cunningly devised lab tests have recently put the future to the test and found that it could indeed be affecting the past.
Aharonov and his colleagues had long predicted that for certain very specific quantum experiments carried out in three successive steps, the way that the third and final step is performed could dramatically change the properties measured during the second, intermediate step. In this sense, actions carried out in the future (the third step) would be seen to affect results of measurements carried out in the past (the second step).
In particular, over the past two years, experimental teams have carried out repeated tests with lasers that show that by tweaking the final step of the experiment they can introduce dramatic amplifications in the amount by which their laser beam is deflected during the intermediate steps of the experiment. In some cases, the observed deflection during the intermediate step can be amplified by a factor of 10,000, depending on choices made in the final step.
Testing fate Rochester physicists, including Ben Dixon (pictured), used Aharonov’s predictions to amplify light in a laser experiment. Credit: University of Rochester
These strange results can be explained simply by Aharonov’s picture: The intermediate amplification is the result of the combination of actions carried out both in the past (the first step) and the future (the final step). It is far more awkward to explain the results using traditional interpretations of quantum mechanics, says Andrew Jordan of the University of Rochester, who helped to devise one of the laser experiments. The situation can be likened to the way that Copernicus’ heliocentric model of the solar system and Ptolemy’s geocentric model both provide valid interpretations of the same planetary data, but the sun-centered model is thought to be simpler and more elegant.
While laser experiments are providing the team with good news, Davies, Aharonov, Tollaksen and their colleague Menas Kefatos, at Chapman University, California, are now searching for observable cosmic consequences of information from the future influencing the past. One place to look is the cosmic microwave background (CMB), the fading afterglow of the big bang. The CMB has faint ripples of warmth or coolness and thirty years ago, Davies developed a model with his then-student Tim Bunch, describing these ripples at the quantum level.
Davies and Tollaksen are now revising this model within the new quantum framework. Physicists have well-developed thoughts about what the initial state of the universe was and what the final state of the universe could end up being (most likely a vacuum, the inevitable result of continued expansion), and the team are putting these together with their new model to see if they can predict characteristic signatures of the future’s influence on the CMB that could be picked up by the Planck satellite.
"Cosmology is an ideal case for this approach," says Bill Unruh of the University of British Columbia, Vancouver. "Since Aharonov has found such strange results in some situations, it’s worth looking at cosmology."
Davies does not yet know whether these ideas will pan out. But if they do, it would be revolutionary. "The remarkable thing about Paul," says Michael Berry of the University of Bristol, "is that he has very wild ideas combined with extreme care and sobriety."
That may be just the character needed to make a breakthrough. It might even be Davies’ destiny.
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