There is a parlor game physics students play: Who was the greater genius?
Galileo or Kepler? (Galileo.) Maxwell or Bohr? (Maxwell, but it's closer than
you might think.) Hawking or Heisenberg? (A nobrainer, whatever the
bestseller lists might say. It's Heisenberg.) But there are two figures who
are simply off the charts. Isaac Newton is one. The other is Albert Einstein.
If pressed, physicists give Newton pride of place, but it's a photo
finish—and no one else is in the race.
Newton's claim is obvious. He created modern physics. His system described the
behavior of the entire cosmos, and while others before him had invented grand
schemes, Newton's was different. His theories were mathematical, making
specific predictions to be confirmed by experiments in the real world. Little
wonder that those after Newton called him lucky—"for there is only one
universe to discover, and he discovered it."
But what of Einstein? Well, Einstein felt compelled to apologize to Newton.
"Newton, forgive me," Einstein wrote in his Autobiographical Notes. "You
found the only way which, in your age, was just about possible for a man of
highest thought and creative power." Forgive him? For what? For replacing
Newton's system with his own—and, like Newton, for putting his mark on
virtually every branch of physics.
Miracle year
That's the difference. Young physicists who play the "who's smarter" game are
really asking "How will I measure up?" Is there a shot to match—if not
Maxwell, then perhaps Lorentz? But Einstein? Don't go there. Match this:
In 1905, Einstein is 26, a patent examiner, working on physics on his own.
After hours, he creates the special theory of relativity, in which he
demonstrates that measurements of time and distance vary systematically as
anything moves relative to anything else. Which means that Newton was wrong.
Space and time are not absolute, and the relativistic universe we inhabit is
not the one Newton "discovered."
That's pretty good, but one idea, however spectacular, does not make a demigod.
But now add the rest of what Einstein did in 1905:
In March, Einstein creates the quantum theory of light, the idea that
light exists as tiny packets, or particles, that we now call photons. Alongside
Max Planck's work on quanta of heat, and Niels Bohr's later work on quanta of
matter, Einstein's work anchors the most shocking idea in 20thcentury physics:
we live in a quantum universe, one built out of tiny, discrete chunks of energy
and matter.
Next, in April and May, Einstein publishes two papers. In one he invents a
new method of counting and determining the size of the atoms or molecules in a
given space, and in the other he explains the phenomenon of Brownian motion.
The net result is a proof that atoms actually exist—still an issue at
that time—and the end to a millenniaold debate on the fundamental nature
of the chemical elements.
And then, in June, Einstein completes special relativity, which adds a
twist to the story: Einstein's March paper treated light as particles, but
special relativity sees light as a continuous field of waves. Alice's Red Queen
can accept many impossible things before breakfast, but it takes a supremely
confident mind to do so. Einstein, age 26, sees light as wave and particle,
picking the attribute he needs to confront each problem in turn. Now that's
tough.
And, of course, Einstein isn't finished. Later in 1905 comes an extension
of special relativity in which Einstein proves that energy and matter are
linked in the most famous relationship in physics: E = mc^{2}. (The
energy content of a body is equal to the mass of the body times the speed of
light squared.) At first, even Einstein does not grasp the full implications of
his formula, but even then he suggests that the heat produced by radium could
mark the conversion of tiny amounts of the mass of the radium salts into
energy.
In sum, an amazing outburst: Einstein's 1905 still evokes awe. Historians call
it the annus mirabilis, the miracle year. Einstein ranges from the
smallest scale to the largest (for special relativity is embodied in all motion
throughout the universe), through fundamental problems about the nature of
energy, matter, motion, time, and space—all the while putting in 40 hours
a week at the patent office.
Who’s smarter? No one since Newton comes close.
Further miracles
And that alone would have been enough to secure Einstein's reputation. But it
is what comes next that is almost more remarkable. After 1905, Einstein
achieves what no one since has equaled: a 20year run at the cutting edge of
physics. For all the miracles of his miracle year, his best work is still to
come:
In 1907, he confronts the problem of gravitation, the same problem that
Newton confronted and solved (almost). Einstein begins his work with one
crucial insight: gravity and acceleration are equivalent, two facets of the
same phenomenon. Where this "principle of equivalence" will lead remains
obscure, but to Einstein, it offers the first hint of a theory that could
supplant Newton's.
Before anyone else, Einstein recognizes the essential dualism in nature,
the coexistence of particles and waves at the level of quanta. In 1911, he
declares resolving the quantum issue to be the central problem of physics.
Even the minor works resonate. For example, in 1910, Einstein answers a
basic question: "Why is the sky blue?" His paper on the phenomenon called
critical opalescence solves the problem by examining the cumulative effect of
the scattering of light by individual molecules in the atmosphere.
Then, in 1915, Einstein completes the general theory of relativity, the
product of eight years of work on the problem of gravity. In general
relativity, Einstein shows that matter and energy—all the "stuff" in the
universe—actually mold the shape of space and the flow of time. What we
feel as the "force" of gravity is simply the sensation of following the
shortest path we can through curved, fourdimensional spacetime. It is a
radical vision: space is no longer the box the universe comes in; instead,
space and time, matter and energy are, as Einstein proves, locked together in
the most intimate embrace.
In 1917, Einstein publishes a paper that uses general relativity to model
the behavior of an entire universe. General relativity has spawned some of the
weirdest and most important results in modern astronomy (see Relativity and
the Cosmos), but Einstein's paper is the starting point, the first in the
modern field of cosmology—the study of the behavior of the universe as a
whole. (It is also the paper in which Einstein makes what he would call his
worst blunder—inventing a "cosmological constant" to keep his universe
static. When Einstein learned of Edwin Hubble's observations that the universe
is expanding, he promptly jettisoned the constant.)
Returning to the quantum, by 1919, six years before the invention of
quantum mechanics and the uncertainty principle, Einstein recognizes that there
might be a problem with the classical notion of cause and effect. Given the
peculiar dual nature of quanta as both waves and particles, it might be
impossible, he warns, to definitively tie effects to their causes.
Yet as late as 1924 and 1925, Einstein still makes significant
contributions to the development of quantum theory. His last work on the theory
builds on ideas developed by Satyendra Nath Bose and predicts a new state of
matter (to add to the list of solid, liquid, and gas) called a BoseEinstein
condensate. The condensate was finally created at exceptionally low
temperatures only in 1995.
In sum, Einstein is famous for his distaste for modern quantum theory, largely
because its probabilistic nature forbids a complete description of cause and
effect. But still he recognizes many of the fundamental implications of the
idea of the quantum long before the rest of the physics community does.
The miracle that eluded him
After the quantum mechanical revolution of 1925 through 1927, Einstein spends
the bulk of his remaining scientific career searching for a deeper theory to
subsume quantum mechanics and eliminate its probabilities and uncertainties. It
is the end, as far as his contemporaries believe, of Einstein's active
participation in science. He generates pages of equations, geometrical
descriptions of fields extending through many dimensions that could unify all
the known forces of nature. None of the theories works out. It is a waste of
time—and yet:
Contemporary theoretical physics is dominated by what is known as "string
theory." It is multidimensional. (Some versions include as many as 26
dimensions, with 15 or 16 curled up in a tiny ball.) It is geometrical: the
interactions of one multidimensional shape with another produces the effects we
call forces, just as the "force" of gravity in general relativity is what we
feel as we move through the curves of fourdimensional spacetime. And it
unifies, no doubt about it: in the math, at least, all of nature from quantum
mechanics to gravity emerges from the equations of string theory.
As it stands, string theory is unproved, and perhaps unprovable, as it involves
interactions at energy levels far beyond any we can handle. But to those versed
enough in the language of mathematics to follow it, it is beautiful. And in
its beauty (and perhaps in its impenetrability), string theory is the heir to
Einstein's primitive first attempts to produce a unified field theory.
Between 1905 and 1925, Einstein transformed humankind's understanding of nature
on every scale, from the smallest to that of the cosmos as a whole. Now, a
century after he began to make his mark, we are still exploring Einstein's
universe. The problems he could not solve remain the ones that define the
cutting edge, the most tantalizing and compelling.
You can't touch that. Who's smarter? No one since Newton comes close.
Note: This feature originally appeared on NOVA's "Einstein Revealed" Web site, which has been subsumed into the "Einstein's Big Idea" Web site.

Who was smarter, Newton or Einstein? "It's a photo finish,"
Levenson says.
 
Quantum theory owes
its existence to Einstein's work as well as that of Max Planck (left) and Niels
Bohr (right).
 
Marie Curie's research with radium led Einstein
to suggest that that radioactive element might be exhibiting E = mc^{2}
in miniature. In time, he was shown to be right.
 
BoseEinstein condensates, a new form of
matter that Einstein predicted in the 1920s and that was first seen in the
1990s, are named in his honor and that of Indian physicist Satyendranath Bose
(above).
 
