A lot of my sophomore year in astronomy was spent solving harmonic oscillator problems.  A harmonic oscillator is something that moves with a periodic motion—say, a pendulum swinging or a mass on a spring sliding back and forth.  Students of physics and astrophysics learn to love (pronounced “loathe” in the first months) harmonic oscillators, because the equations that describe their motion also describes a bunch of other phenomena, including what happens when you deform a solid and the quantum theory of the atom.  If you’re able to solve a simple harmonic oscillator problem, you can solve a whole gamut of others.

Needless to say, now that I’m a writer I never thought to see a harmonic oscillator again.  Fancy my surprise when I read the physics colloquium title for last week’s speaker:  “Black Holes: The Harmonic Oscillators of the 21st Century.”

The speaker, Dr. Andrew Strominger of Harvard University, said that, just as his PhD advisor once told him to beat quantum chromodynamics* into submission by treating it like a harmonic oscillator, he now tells his students to take anything and treat it like a black hole.

Black holes’ utility, Strominger argued, is that they are both the most simple and most complex objects in the universe.  With a mere three numbers—mass, spin (rotation), and charge (which isn’t important, astrophysically)—we can fully describe a black hole, an object which is basically “nothing,” a nondescript hole in spacetime.  Yet black holes are also thermodynamic objects with an absurd number of possible internal states:  their entropy, or disorder, is the highest it could be within the spacetime the black holes occupy.

That’s neat, but how does that make them harmonic oscillators?  Strominger claims that black holes simplify the study of quantum gravity, the unification (as yet unattained) of Einstein’s general relativity theory of gravity with quantum mechanics.  They achieve this feat by reducing the problem to just one dimension of spacetime movement:  the material falling into a black hole has very particular rules governing its orbit that limit the motion of matter in this way.  By studying black holes, physicists could extrapolate backwards to two dimensions, and, hopefully, further.  

Strominger says this ability to collapse the problem could be useful in fields like algebraic geometry and superconductivity.  And because the black hole’s horizon is a one-way membrane (minus Hawking radiation), it’s basically a fluid, which means that understanding the event horizon might actually improve our understanding of fluid mechanics and turbulence.

So, not only are black holes the only macroscopic elementary particle of the universe, they’re the keyhole in the door to understanding it.  I just hope students learn to love black holes for deeper reasons than I loved harmonic oscillators.

*quantum chromodynamics:  the study of the interactions between quarks, the subatomic particles that make up protons and neutrons, and, to some extent, between protons and neutrons.