PLanting a seed: was Newton responsible for biasing

our minds about the way the universe works? (Image:

Royal Institution Of Great Britain/SPL)

Ever since Isaac Newton, we have relied on

the notion that the universe works like a

computer. It’s time to question this

assumption

PROGRESS in physics often comes about by

discarding the bias that humans are at the

centre of everything, the most obvious

example being the repositioning of our planet

from the centre of the universe. But might

there still be such anthropocentrism lurking in

our best models of reality? Experience and

instinct make it natural to have such biases;

the difficulty is recognising them and finding a

more objective vantage point from which to

evaluate them. And there is one particular bias

that has resisted this evaluation for far too

long.

We have grown accustomed to the idea that there is no centre of the universe. The space to our left is

no different from the space to our right. But our instincts balk when this comparison shifts from space

to time. Our immediate future seems somehow different to our immediate past. We can fight these

instincts with careful logic, realising there is nothing special about "now", because every time we have

ever experienced seemed like "now" at the time.

The importance of putting the past and future on an equal footing is particularly clear in Einstein's

general theory of relativity. But these arguments still seem instinctively wrong. After all, we don't know

the future, and we can't act to change the past. Our human condition has given rise to an

anthropocentric bias when it comes to time.

Many physicists will tell you that we have purged this bias along with the others. All of the microscopic

laws of physics are time-symmetric, and general relativity represents space and time together as a

four-dimensional "space-time block". Nevertheless, there is a related bias still hiding in modern

physics, and it has been there since Newton - an instinct so natural that it's hard to even notice. This is

the assumption that the universe solves problems in the same way that we do - that the universe works

like a computer.

Humans are always trying to compute the future. Given that all of our experience is of the past, there is

really only one way we can do this: take information about the past, manipulate it using some rules, and

then use the result to forecast the future. Mechanical computers process data in the same fashion.

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A computer cosmos will never explain quantum physics

15 February 2013 by Ken WhartonMagazine issue 2903. Subscribe and saveFor similar stories, visit the The Big Idea , The Human Brain and Quantum World Topic Guides

So it is not surprising that when Newton first laid out how to do physics, he framed it with the same

computational "schema": 1) Map present reality onto some mathematical state; 2) Input that state into

some dynamical equation; 3) Map the equation's output back onto a future reality. As we know, this

process works quite well - many predictions made in this manner actually come to pass.

But even though we have moved well beyond Newtonian physics, we haven't yet moved beyond the

Newtonian schema. The universe, we almost can't help but imagine, is some cosmic computer that

generates the future from the past via some master "software" (the laws of physics) and some special

initial input (the big bang). Note that this is very different from the claim that the universe is a computer

simulation.

After 400 years of solving physics problems in this way, it's only natural that we have incorporated this

schema into our world view. This is the case even when it backs us into an impossible corner, as when

we try to use it to explain quantum phenomena.

The key point is that Newton's schema naturally arose from our human experience of time, and it is

arguably out of sync with what we have discovered since. The notion of the cosmic computer is itself

an anthropocentric bias. This doesn't mean that it's wrong, but it does mean that it should be evaluated

from an unbiased vantage point. This evaluation has not yet occurred.

That could soon change. It may be surprising to hear that there is already a wildly different alternative

to Newton's 3-step schema. The "Lagrangian" approach, largely laid out in 1788 by the mathematician

Joseph Louis Lagrange, turns out to be of crucial importance to both relativity and quantum theory. A

simple example of a Lagrangian-style approach is Fermat's principle of least time, which describes

how light rays travel.

Fermat supposed that when a ray of light travelled from X to Y it would always take the quickest path of

all paths available. In a uniform material this is a straight line, but it is a different matter for rays that

pass from air to water, where light travels more slowly. Just as a smart lifeguard will run a crooked path

to rescue a drowning swimmer - diagonally for the fast portion on the beach, and then less-diagonally

for the slow portion through the water - light rays do the same.

Fermat's principle makes it much easier to explain certain phenomena. Take mirages: light travels

faster just above a hot surface, so the light from the sky bends in such a way that it appears to be

coming from the ground. But stories like this don't follow the Newtonian schema - they don't require

dynamical equations, just two endpoints, X and Y, and a process to determine the fastest of all the

possible paths between them. Crucially, this style of physics is not as blind to the future as we are

ourselves.

Remarkably, these principles can be extended to all of classical physics, and are especially valuable

to quantum field theory. But despite using the Lagrangian approach, physicists tend to view it as a

mathematical trick rather than as an alternative framework for how our universe might really work. This

attitude may be an indication of our biases, where our cosmic computer assumption is so deeply

ingrained that we don't even realise we are making it.

This is not irrelevant metaphysics. Our assumptions frame our best models in physics, and for

quantum physics in particular, the models have deep problems. For example, quantum predictions are

fundamentally uncertain, and Newton's schema doesn't work so nicely with uncertain inputs or

uncertain equations. So modern quantum theory effectively removes this initial uncertainty, postponing

it until the final output step when it can no longer be ignored. Adhering to the Newtonian schema then

leads to a ridiculously impossible "collapse", when all the built-up uncertainty suddenly emerges into

reality.

Contrast this with the mirage example, where the uncertainty of the actual path between X and Y was

smoothly spread out and elegantly solved by Lagrange's methods. Nevertheless, if such stories can't

be translated into the Newtonian schema, no one seems to take them seriously as a template for how

our universe might operate.

From issue 2903 of New Scientist magazine,page 30-31.

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좋아요 5

Well, almost no one. I am proposing a modification of the most Lagrangian-friendly formulation of

quantum theory, such that the mathematics could be taken literally (arxiv.org/abs/1301.7012). If it

works, it could provide an underlying realistic explanation of quantum phenomena, but without any

corresponding Newtonian schema version. Confronting our biases is a prerequisite for even

considering this style of explanation. While it's far too soon to see whether this modification will be

successful, it is about time we tried setting aside our anthropocentric notion of the cosmic computer

and at least see what the alternatives might look like.

Who knows? Quantum theory may have more in common with mirages than anyone could have

guessed, and our universe may not be a computer after all.

This article appeared in print under the headline "Against the cosmic computer"

ProfileKen Wharton is a quantum physicist at San José State University in California. This article is

based on his essay "The universe is not a computer", which won third prize in the 2012

Foundational Questions Institute essay contest

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