Sunday, November 11, 2012 essays on explanations

I remarked that physicists keep looking for hidden variables, in spite of an 80-year consensus that such theories contradict quantum mechanics. Satyajit Das writes in response to the annual question:
In 1927, Heisenberg showed that uncertainty is inherent in quantum mechanics. ...

The play repeats their meeting three times, each with different outcomes. As Heisenberg, the character, states: "No one understands my trip to Copenhagen. Time and time again I've explained it. To Bohr himself, and Margrethe. To interrogators and intelligence officers, to journalists and historians. The more I've explained, the deeper the uncertainty has become."

In his 1930 text The Principles of Quantum Mechanic. Paul Dirac, a colleague of Heisenberg, contrasted the Newtonian world and the Quantum one: "It has become increasingly evident… that nature works on a different plan. Her fundamental laws do not govern the world as it appears in our mental picture in any direct way, but instead they control a substratum of which we cannot form a mental picture without introducing irrelevancies."
Dirac was right. It is very hard to form a mental picture of the atom without introducing irrelevant hidden variables.

I think that today's search for hidden variables is a misguided attempt to validate some flawed mental picture. They are usually not explicit about their faulty assumptions.

For an example of someone who expects mathematics to explain everything, Antony Garrett Lisi writes:
What is tetrahedral symmetry doing in the masses of neutrinos?! Nobody knows. But you can bet there will be a good explanation. It is likely that this explanation will come from mathematicians and physicists working closely with Lie groups. The most important lesson from the great success of Einstein's theory of General Relativity is that our universe is fundamentally geometric, and this idea has extended to the geometric description of known forces and particles using group theory. It seems natural that a complete explanation of the Standard Model, including why there are three generations of fermions and why they have the masses they do, will come from the geometry of group theory. This explanation does not yet exist, but when it does it will be deep, elegant, and beautiful — and it will be my favorite.
Yes, we have geometric description of the known forces and particles, but I am not so sure that the our universe is fundamentally geometric.

Eric R. Weinstein also promotes the geometrical theory of everything:
But the most important lesson is that, at a minimum, Einstein's minor dream of a world of pure geometry has largely been realized as the result of a large group effort. All known physical phenomena can now be recognized as fashioned from the pure, if still heterogeneous, marble of geometry through the efforts of a new pantheon of giants. Their achievements, while still incomplete, explain in advance of unification that the source code of the universe is overwhelmingly likely to determine a purely geometric operating system written in a uniform programming language.
Lisa Randall writes:
The Standard Model's success nonetheless illustrates another beautiful idea essential to all of physics, which is the concept of an "effective theory." The idea is simply that you can focus on measurable quantities when making predictions and leave understanding the source of those quantities to later research when you have better precision.
Not only physics. This idea has been essential to all of science for millennia. She is just describing a theory that has been stripped of its pretentions of being some sort of perfect knowledge.

It is funny that she describes effective theory as if it were just one type of a physical theory. She also studies string theory which never makes any predictions and claims to be a theory of everything. She acts as if these are just two kinds of scientific theories. No, there is one kind of scientific theory. String theory is not science.

All of the Edge essays are on this page.

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