Lawrence Krauss, a professor of physics and astronomy at Case Western Reserve University, has a reputation for shooting down pseudoscience. He opposed the teaching of intelligent design on The NewsHour With Jim Lehrer. He penned an essay for the New York Times that dissed President Bush's proposal for a manned Mars mission. Yet in his latest book, Hiding in the Mirror, Krauss turns on his own—by taking on string theory, the leading edge of theoretical physics. Krauss is probably right that string theory is a threat to science, but his book proves he's too late to stop it.
String theory, which stretches back to the late 1960s, has become in the last 20 years the field of choice for up-and-coming physics researchers. Many of them hope it will deliver a "Theory of Everything"—the key to a few elegant equations that explain the workings of the entire universe, from quarks to galaxies.
Elegance is a term theorists apply to formulas, like E=mc2, which are simple and symmetrical yet have great scope and power. The concept has become so associated with string theory that Nova's three-hour 2003 series on the topic was titled The Elegant Universe (you can watch the whole thing online for free here).
Yet a demonstration of string theory's mathematical elegance was conspicuously absent from Nova's special effects and on-location shoots. No one explained any of the math onscreen. That's because compared to E=mc2, string theory equations look like spaghetti. And unfortunately for the aspirations of its proponents, the ideas are just as hard to explain in words. Let's give it a shot anyway, by retracing the 20th century's three big breakthroughs in understanding the universe.
Step 1: Relativity (1905-1915). Einstein's Special Theory of Relativity says matter and energy (E and m in the famous equation) are equivalent. His General Theory of Relativity says gravity is caused by the warping of space due to the presence of matter. In 1905, this seemed like opium-smoking nonsense. But Einstein's complex math (E=mc2 is the easy part) accurately predicted oddball behaviors in stars and galaxies that were later observed and confirmed by astronomers.
Step 2: Quantum mechanics (1900-1927). Relativistic math works wonderfully for predicting events at the galactic scale, but physicists found that subatomic particles don't obey the rules. Their behavior follows complex probability formulas rather than graceful high-school geometry. The results of particle physics experiments can't be determined exactly—you can only calculate the likeliness of each possible outcome.
Quantum's elegant equation is the Heisenberg uncertainty principle. It says the position (x) and momentum (p) of any one particle are never completely knowable at the same time. The closest you can get is a function related to Planck's constant (h), the theoretical minimum unit to which the universe can be quantized.
Einstein dismissed this probabilistic model of the universe with his famous quip, "God does not play dice." But just as Einstein's own theories were vindicated by real-world tests, he had to adjust his worldview when experimental results matched quantum's crazy predictions over and over again.
These two breakthroughs left scientists with one major problem. If relativity and quantum mechanics are both correct, they should work in agreement to model the Big Bang, the point 14 billion years ago at which the universe was at the same time supermassive (where relativity works) and supersmall (where quantum math holds). Instead, the math breaks down. Einstein spent his last three decades unsuccessfully seeking a formula to reconcile it all—a Theory of Everything.
Step 3: String theory (1969-present). String theory proposes a solution that reconciles relativity and quantum mechanics. To get there, it requires two radical changes in our view of the universe. The first is easy: What we've presumed are subatomic particles are actually tiny vibrating strings of energy, each 100 billion billion times smaller than the protons at the nucleus of an atom.