Zero - Charles Seife [63]
This might not seem like such a strange assumption, but it is not the way the world seems to work. Nature doesn’t move in jumps. It would seem silly to have five-foot-tall people and six-foot-tall people but nothing in between. It would be ridiculous if cars drove at 30 miles an hour and 40 miles an hour, but never at 33 or 38 miles an hour. However, a quantum car would behave in exactly this way. You might be driving along at 30 miles an hour, but when you step on the gas, all of a sudden you would instantly—pop!—be driving 40 miles an hour. Nothing in between is allowed, so to get from 30 to 40 miles an hour, you have to make a quantum leap. In the same way, quantum people could not grow very easily; they would hover at four feet for a number of years, and then, in a fraction of a second—pop!—they would be five feet tall. The quantum hypothesis violates everything our everyday experience tells us.
Even though it doesn’t agree with the way nature seems to work, Planck’s strange hypothesis—that molecular vibrations were quantized—led to the correct formula for the frequencies of light that come off an object. Even though physicists quickly realized that Planck’s equation was right, they did not accept the quantum hypothesis. It was too bizarre to accept.
An unlikely candidate would turn the quantum hypothesis from a pecularity to an accepted fact. Albert Einstein, a twenty-six-year-old patent clerk, showed the physics world that nature worked in quanta rather than in smooth increments. He would later become the chief opponent of the theory he helped create.
Einstein didn’t seem like a revolutionary. When Max Planck was turning the physics world on its head, Albert Einstein was scrambling for a job. Out of money, he took a temporary position at the Swiss patent office, a far cry from the assistantship at a university that he wanted. By 1904 he was married, had a newborn son, and was laboring in the patent office—hardly the path to greatness. However, in March 1905, he wrote a paper that would eventually earn him the Nobel Prize. This paper—which explained the photoelectric effect, brought quantum mechanics into the mainstream. Once quantum mechanics was accepted, so, too, would the mysterious powers of zero.
The photoelectric effect was discovered in 1887 when the German physicist Heinrich Hertz discovered that a beam of ultraviolet light could cause a plate to spark: electrons quite simply pop out of the metal when light shines on it. This phenomenon, causing sparks with a beam of light, was very puzzling to classical physicists. Ultraviolet light is light with a lot of energy, so scientists naturally concluded that it took quite a bit of energy to kick an electron out of an atom. But according to the wave theory of light, there is another way to get high-energy light: make it brighter. A very bright blue light, for instance, might have as much energy as a dim ultra-violet beam; therefore, a bright blue light should be able to kick electrons out of atoms, just as a dim ultraviolet beam can.
This simply is not the case, as experiments quickly showed. Even a dim beam of ultraviolet (high frequency) light causes electrons to get knocked out of the metal. However, if you lower the frequency just a little bit beyond a critical threshold—making the light a wee bit too red—the sparking stops all of a sudden. No matter how bright the beam is, if the light is the wrong color, all the electrons in the metal stay put; none of them can escape. That’s not the sort of thing a light wave would do.
Einstein solved this quandary—the puzzle of the photo-electric effect—but his solution was even more revolutionary than Planck’s hypothesis. While Planck proposed that molecules’ vibrations were quantized, Einstein proposed that light came in little packets of energy called photons. This idea conflicted with the accepted physics of light, because it meant that light was not a wave.
On the other hand, if light energy is bundled into little packets, then the photoelectric effect is easy