22 JUNE 2006
IRVINE,
Calif. — If you're a devotee of vacationing in strange places, you'll surely want to visit the volcanoes in Hawaii, the Grand Canyon in Arizona, and the canals of Venice, Italy (or, for stranger still, spend a day people-watching at Venice Beach in California).
But for the strangest vacation of all, you need not venture a centimeter from where you stand. The universe itself surpasses in strangeness any vacation spot you can imagine.
Just ask Frank Wilczek, winner of the Nobel Prize in physics in 2004. In a recent public lecture at the University of California, Irvine, he guided the audience on an intellectual tour of the strangeness of the cosmos and the mysterious successes physics has had in explaining it.
It is strange, for instance, that most of the matter in the universe is mysteriously "dark," that
is, not visible to telescopes, while its presence is deduced from the gravitational
effects it exerts on visible galaxies of stars.
Other
evidence shows that the
dark matter cannot consist of the ordinary kind of matter
(atoms or the particles
from which atoms are made) found on earth.
There's perhaps five times as much of this mystery matter in the universe than
the kind of ordinary matter we know about. How strange is that?
In this false-color X-ray image of hot gas within a group of galaxies, it is deduced that the presence of dark matter and it's gravitational effects keep the gas from escaping. Image: NASA
Even stranger, all of space is infused with an equally mysterious dark form of energy. This "dark energy" is far more abundant than all the rest of the matter and energy in the universe put together. And it has the weird property of exerting "negative pressure." Instead of smushing things together (which is what ordinary pressure does) the negative-pressure dark energy drives things apart, including space itself. As a consequence, the universe is not only expanding, it is growing larger at a faster and faster rate. Stranger and stranger.
Curiously, though, ordinary matter itself is even stranger still. Where does
it come from? Atoms are made of electrons which fly around a nucleus made of
protons and neutrons. 
Almost all the mass of an atom is in the nucleus, so
you'd think matter is mainly composed of protons and neutrons. But where do
they get their mass? Both particles, physicists now know, are made of smaller
particles known as quarks and gluons (the gluons, strangely enough, being the
particles that hold the quarks together).
Surprisingly, though, gluons themselves have no mass. And the quarks have very little mass, far less than the mass measured for protons and neutrons. Which makes it very strange that atoms have any mass at all. Fortunately, Einstein provided the recipe for resolving this paradox, by pointing out that matter is really just a form of energy.
The mass of an object depends mainly on its energy content, the basis of the paper Einstein wrote when he introduced his famous equation E = mc2. Actually, the original paper put it differently, expressing it as m = E/c2. (OK, really it was m=L/c2, but that's because the paper was in German.)
"It's the energy of this massless stuff…that makes the mass," Wilczek explained in his talk.
Matter therefore comes from energy, but where does the energy come from? That gets much trickier, but the abridged answer is that matter particles represent the energy of vibrating waves in empty space. Thanks to some other strange features of the universe, all sorts of particles boil up out of emptiness, kicking up a kaleidoscopic mishmash of frenzied activity throughout all space (on submicroscopic scales). The void, it seems, is where the actions is, which just goes to show that nothing is stranger than nothing.
"What appears to us as empty space is in reality a wildly dynamical medium," Wilczek told his audience at the Irvine lecture. (You can see what it would look like, if you could see things that small, in a simulation here.)
When this background of activity is disturbed, particles such as the ones we know appear as vibrations on top of all the unseen activity below. Masses of the particles correspond to the vibration frequencies, so in a sense masses are the tones played by the music of the void.
These and other strange features of reality are not merely simplified pictures to explain the world at large -- they are the reality. The world at large as we usually describe it is the simplified picture that we use to conceal the subtleties of the real subatomic world.
Strangely enough, there is no particular reason that people should have been able to discern the strange subtleties of the subatomic realm. After all, the human brain evolved to deal with things like escaping from tigers and finding food. But the power of mathematics and the cleverness of experiments have led science to a deeper understanding of the weirdness of reality.
"Who would have thought that creatures evolved to interact with nature and each other at distances of centimeters or meters could possibly understand . . . such small objects and such strange objects?" Wilczek said. "It's a remarkable thing that we really can understand the basic structure of matter, even though it is so strange."
In other words, the strangest thing about the universe is the ability of human brains to figure out how strange the universe is.
E-mail: tsiegfried@nasw.org
