Posted by MIT Technology Review Dec. 4. 2012.
The idea that our Universe is a giant cosmic computer pervades modern science. Now one physicists says this assumption is dangerously wrong.
One of the driving forces in modern science is the idea that the Universe “computes” the future, taking some initial state as an input and generating future states as an output. This is a powerful approach that has produced much insight. Some scientists go as far as to say that the Universe is a giant computer.
Is this a reasonable assumption? Today, Ken Wharton at San Jose State University in California, makes an important argument that it is not. His fear is that the idea of the universe as a computer is worryingly anthropocentric. “It’s basically the assumption that the way we humans solve physics problems must be the way the universe actually operates,” he says.
What’s more, the idea has spread through science without any proper consideration of its validity or any examination of the alternatives. “This assumption…is so strong that many physicists can’t even articulate what other type of universe might be conceptually possible,” says Wharton.
He argues that a close look at the notion of the cosmos as a computer reveals important problems. Wharton examines several. For example, a computation involves three steps. First, the physical world has to be mapped onto some mathematical state. Next, this state mathematically evolves into a new state. And finally, the new state is mapped back onto the physical world.
In quantum mechanics, this can only happen if this final step is probabilistic. As Wharton puts it: “Not even the universe knows which particular outcome will occur.”
And yet, when the universe is measured, a specific outcome does occur. The operation of a computer cannot account for this. For Wharton, this is a crucial flaw that most physicists just overlook.
It’s also an important clue that idea of the universe is a computer is merely an assumption and one that has never been rigorously questioned. “It is the least-questioned (and most fundamental) assumptions that have the greatest potential to lead us astray,” he says.
The consequences of this are profound. “Thanks to this deep bias, it’s possible that we have missed the bigger picture: the mounting evidence that the fundamental rules that govern our universe cannot be expressed in terms of [a traditional computation].”
To demonstrate the point, Wharton spends a significant part of his paper explaining an alternative view of the cosmos which does not rely on traditional computation. This is Lagrange’s formulation of the laws of physics based on the principle of least action.
An example is the principle that light travels the shortest distance between two points. Lagrange’s method is essentially to stipulate the start point and end point, examine all possible paths and choose the shortest. “In this view, the reason light bends at an air/water interface is not because of any algorithm-like chain of cause-and-eﬀect, but rather because it’s globally more eﬃcient,” explains Wharton.
Anybody familiar with this approach will know its great elegance and beauty. But critics ask how the light ray can know its end point when it starts its journey. Wharton says these critics argue like this: “Yes, [Lagrange’s method] may be beautiful, it may be powerful, but it’s not how our universe really works. It’s just a useful trick we’ve discovered.”
But this argument is itself powerfully anthropocentric, says Wharton. It assumes the Universe must work in the way we solve problems–that the Universe is as “in the dark” about the future as we are.
Of course, there are plenty of good arguments for thinking that the Universe works like a conventional computer. The point Wharton makes is that there are other ways of thinking about the cosmos too and that these may provide important new insights. We ignore them at our peril.
Ref: arxiv.org/abs/1211.7081: The Universe As Not A Computer