Sunday, December 28, 2014

Why string theory has unraveled

Smithsonian magazine published a Brian Greene article under the title "Is String Theory About to Unravel?" Usually the editor chooses the title, without necessarily any input from the author.

He gives a short history of string theory, how he became one of the theory's biggest enthusiasts, but the past 30 years is mostly a story of theoretical and experiment failures. He even concedes:
I now hold only modest hope that the theory will confront data during my lifetime. ... Looking back, I’m gratified at how far we’ve come but disappointed that a connection to experiment continues to elude us.
So the editor probably read the article and concluded that the theory was unraveling. But either Greene or the other string theorists complained, and now the title reads, "Why String Theory Still Offers Hope We Can Unify Physics".

Arguments for unverifiable theories usually cite Einstein:
Unification has become synonymous with Einstein, but the enterprise has been at the heart of modern physics for centuries. Isaac Newton united the heavens and Earth, revealing that the same laws governing the motion of the planets and the Moon described the trajectory of a spinning wheel and a rolling rock. About 200 years later, James Clerk Maxwell took the unification baton for the next leg, showing that electricity and magnetism are two aspects of a single force described by a single mathematical formalism.

The next two steps, big ones at that, were indeed vintage Einstein. In 1905, Einstein linked space and time, showing that motion through one affects passage through the other, the hallmark of his special theory of relativity. Ten years later, Einstein extended these insights with his general theory of relativity, providing the most refined description of gravity, the force governing the likes of stars and galaxies. With these achievements, Einstein envisioned that a grand synthesis of all of nature’s forces was within reach. ...

While spectacularly successful at predicting the behavior of atoms and subatomic particles, the quantum laws looked askance at Einstein’s formulation of gravity. ...

I like to think that Einstein would look at string theory’s journey and smile, enjoying the theory’s remarkable geometrical features while feeling kinship with fellow travelers on the long and winding road toward unification.
It is not so well known, but Einstein hated geometric formulations of relativity. The string theorists like to pretend that Einstein would have liked the geometric aspects of string theory, but that is unlikely. And his vision of force unification was foolishness, as he never even considered the strong or weak nuclear forces, and never accepted quantum mechanics.

The only string theory accomplishment given is this:
Take black holes, for example. String theory has resolved a vexing puzzle by identifying the microscopic carriers of their internal disorder, a feature discovered in the 1970s by Stephen Hawking.
He is referring to black hole entropy being proportional to the area of the event horizon. The string theorists have another argument for this formula. So they have a new view of some old and untestable formula.

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