Symmetry— Essay: By K.C. Cole
People say that nothing is perfect. I beg to differ. The notion of symmetry is both perfect and nothing—a combination that gives it unreasonable effectiveness in physics.
Summing up 50 years of progress in fundamental physics, David Gross recently concluded: “The secret of nature is symmetry.” Everyone gets seduced by symmetry in one form or another, whether it’s the symmetry inherent in snowflakes or snail shells, kaleidoscopes or decorative tiles. But in physics, symmetry is more than just a pretty face. As Emmy Noether showed, there are symmetries behind every fundamental law.
This makes sense, because a symmetry describes what doesn’t vary even as things change—the solid truth beneath the superficial difference. Einstein, who first made symmetry central to physics, exposed a wealth of these pseudo-differences—including those between energy and matter, space and time. (As Einstein so often pointed out, his theories aren’t so much about things that are relative as things which are invariant.)
The late Frank Oppenheimer even cited the Golden Rule as an example of symmetry: If you do unto others as you’d like others to do unto you, and the doer and doee change places, it shouldn’t make a difference. Of course, a snowflake is symmetrical in that you can rotate it 60 degrees without making a discernible difference. But if you rotate it 5 degrees, the symmetry is shattered. To a physicist, the puddle the snowflake melts into is much more symmetrical: snowflakes can be individuals, but drops of water all look alike.
Turning snowflakes into drops of water is essentially what the Large Hadron Collider (LHC) at CERN in Geneva will be trying to do—melting matter to reveal underlying symmetries.
If supersymmetric particles turn up at high energies, for example, it will mean that bosons and fermions—which seem like apples and oranges—have fallen off the same family tree. Each quark will have its squark; each photon its photino—a perfectly symmetrical team. The symmetry lost when the universe cooled will be, for the moment, restored.
Even more beautiful symmetries appear at even higher energies. Heat up the universe to big bang temperatures, and the wildly diverse family of forces turns into one. String theory, with its tangled 10-dimensional topologies, is more symmetrical still; with so much room to move about, there are ample ways for the same thing (the string) to appear in radically different forms (quarks, gravity).
Connecting the dots..