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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
no-brainer, whatever the best-seller 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
20th-century 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 millennia-old 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 20-year 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, four-dimensional space-time. 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
Bose-Einstein 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 four-dimensional space-time. 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.
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