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Einstein's "Year of Wonders," 100 Years Later

Stefan Lovgren
for National Geographic News
Updated April 15, 2005
 
It has been a hundred years since Albert Einstein's annus mirabilis, or "year of wonders," during which the then-26-year-old government worker wrote a series of papers that revolutionized our understanding of the universe.

To mark the occasion, 2005 has been designated by the United Nations as the International Year of Physics.

There have, of course, been scores of groundbreaking scientific developments since Einstein's time. Yet at its core, science is still operating in the same framework that Einstein laid out a century ago.

"He changed not only science but also the way to go about good science," said Gerald Holton, a physics professor and Einstein scholar at Harvard University in Cambridge, Massachusetts. "He was not trying to find solutions to small problems but to bring all of physics under one roof."

E=mc2

Einstein, who was born in Germany, really was working as a lowly clerk at the Swiss Patent Office in Bern when he conceived his radical theories, which came to provide the foundation of modern physics.

He submitted his series of papers to the Annalen der Physik, the leading German physics journal at the time.

In a paper written in May, 1905, Einstein showed how the existence of atoms—an idea that had been hotly debated but far from universally accepted—could be verified by measuring the jiggling of microscopic particles in a glass of water.

The process, measuring what is known as Brownian motion, gave scientists a way to count atoms by looking through an ordinary microscope.

In June of that year, Einstein introduced relativity, a theory of time, distance, mass, and energy. He set the speed of light as the universal speed limit and showed that distance and time are not absolute but instead affected by one's motion.

"Until his day, people were tied to this idea of time as being fixed," said Clifford Will, a physics professor at Washington University in St. Louis, Missouri. "Einstein took an operational viewpoint that time is what clocks measure and nothing more." (Will is the author of Was Einstein Right?)

In a three-page add-on to the theory, completed in September 1905, Einstein derived his famous equation E=mc2. The equation shows that the energy of a body equals its mass times the speed of light squared.

Quantum Mechanics

Yet it was his first paper, written in March, that was perhaps his most revolutionary.

In it, Einstein argued that light is not a wave, as most physicists previously thought, but instead a stream of tiny packets of energy that have since come to be known as photons. This helped explain the photoelectric effect (the emission of electrons by certain substances when subjected to light or radiation).

The theory won Einstein the Nobel Prize in 1921 and helped lay the foundation for quantum theory, which states that physics cannot make definite predictions. It can only predict the probability that things will turn out one way or another.

The quantum theory, with its statistical description of nature at the subatomic scale, has turned out to be right.

However, Einstein came to reject the unpredictability of quantum mechanics, famously saying, "God does not play dice with the universe." Instead he saw it as a mere path to a deeper and more complete description of the universe.

"He couldn't accept that so deeply woven into the fabric of the cosmos was an element of uncertainty," said Brian Greene, a physics and mathematics professor at Columbia University in New York. "He hoped the probabilistic framework of quantum mechanics was merely an intermediary point physicists reached in their study. But that doesn't seem to be the case," said Greene, who wrote the best-selling The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory.

Unified Theory

Holton, the Harvard physicist, says it is a mistake to look at Einstein's papers individually.

"They all show the same motivation," Holton said. "In the very first lines [Einstein says] there is something wrong with the way we understand nature … that there are microscopic bodies big enough to see, and a submicroscopic world of atoms and molecules, which we can't see. Einstein said, 'No, there must be just one kind of physics. God would not have made two kinds of physics.'"

Einstein became convinced that one unified theory could explain the order of the universe.

"His way of approaching physics was to find connections between things which had been viewed as separate," Greene said. "His ultimate goal was to find a connection between all of nature's forces."

Einstein never succeeded in his search for a theory of everything. But many people consider string theorists such as Greene to be Einstein's natural successors.

String theory is a physical model that says that the fundamental building blocks of the universe are vibrating filaments of energy within every particle.

"We're certainly carrying on a program that Einstein initiated," Greene said. "Whether we are on the right track, I don't know. But if it is correct, then it would be the kind of theory that Einstein spent 30 years searching for but never found. That would be quite a wonderful thing."

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