There was physics before Einstein… in the
same way that there was biology before Darwin.
Einstein didn’t just add some new ideas
to physics. And he didn’t just add a unifying
framework for doing physics, like Newton.
Einstein took what people thought was physics,
turned it upside down, then turned it inside
out.
In the same way Darwin’s work made people
see life itself differently, Einstein’s
work made humanity reexamine time and space.
[Intro Music Plays]
The classical worldview—associated with
names you know, like Euclid, Aristotle, and
Newton—held that the rules governing space
and time were absolute. One meter was always
one meter long; one hour would always be one
hour long…
Matter was made up of immutable and indivisible
atoms.
And energy moved through a medium called ether—because
everything had to move through something,
right? God wouldn’t just make, I dunno,
a howling void?
And with new disciplines like thermodynamics
and fun applications like steam power and
light bulbs, human understanding of the fundamental
forces of nature seemed pretty solid.
To quote historian of science Milena Wazeck, by 1900, “physics
was perceived by many to be an almost completed
discipline.”
But within this almost-completeness lurked
many unanswered questions. One of the biggest
was the failure of the Michelson–Morley
experiment in 1887. They’d attempted to
demonstrate that the speed of light changed
just a little when measured from the earth,
which is always moving, relative to the ether,
which never moves.
But despite meticulous efforts, they couldn’t
find any slowing-down. Light moved at a constant
speed—almost as if there was no ether.
Then there was the electron and radioactivity.
In 1897, English physicist J. J. Thomson showed
that cathode rays were made up of discrete
particles, way smaller than whole atoms—electrons.
And around the same time, Marie Curie proposed
the theory of radioactivity, which classical
physics didn’t predict.
Then, in the early 1900s, Ernest Rutherford
experimented on radioactive decay. He named
radioactive alpha, beta, and gamma particles,
classifying them by their ability to penetrate
different kinds of matter.
And Henri Becquerel measured
beta particles and realized they were actually
electrons exiting the nuclei of atoms at high
speeds.
So by the early 1900s, radioactive decay was
understood, and the crisis of the immutable
atom was as deep as the crisis of the ether.
A bunch of folks were investigating Maxwell’s
equations and looking at black-body radiation,
or the heat emitted by dark objects when they
absorb light.
Then Heinrich Hertz, the original radio wave
guy, discovered the photoelectric effect,
or the paradox that certain metals produce
electrical currents when zapped with wavelengths
of light above a certain threshold.
Things started to get messy. Energy was thought
to be a continuous wave. But according to
wave-based theory, there might be infinite
energy radiated back by black bodies zapped
with certain wavelengths. This seemingly violated
the newly established laws of thermodynamics. Like, infinite energy doesn't seem right.
So, in trying to explain the weird results
about light and heat, German physicist Max
Planck theorized that light
may not be a wave after all, but a series
of particles or quantum units. All very non-“classical.”
Sorry, Aristotle!
Check out Crash Course: Physics for more about
quantum weirdness!
Enter Albert.
Einstein was born in 1879 and grew up in southern
Germany, Italy, and Switzerland. He dropped
out of high school, then studied to teach
physics and math and became a Swiss citizen.
But he couldn’t get a teaching job—because
he was Jewish.
So in 1901 he took a job at the patent office
and started a Ph.D. at the University of Zurich,
which he finished in 1905. You’re going
to want to remember that year…. 1905.
Now, Al wasn’t an academic hotshot or self-funded
amateur. He was a working-class nobody who
did physics on the side. But he was also a
patent officer who spent his days pouring
over technical documents.
He was an outsider obsessed with math because
math is beautiful, and yet he was a deeply
practical person who believed that good math
and science could be communicated plainly.
Plus, he was young and bold. And he had a
super smart and supportive first wife, Serbian
mathematician Mileva Marić.
So, the year he finished his Ph.D., 1905,
Al published his dissertation and four papers
that changed physics overnight. This was his
annus mirabilis or miracle year, like 1666 had been for Newton.
Help us out, ThoughtBubble.
At age twenty six, Einstein published revolutionary
work on:
1. Brownian motion, or the random motion of particles
in fluids;
2. the photoelectric effect, supporting the idea
of energy as a series of particles, not a wave;
3. the equivalence of mass and energy; and
4.special relativity.
Special relativity, especially made Einstein
a scientific rock star. He proved that nothing
can move faster than light. This explained
why Michelson and Morley hadn’t observed
light slowing in ether. And a lot of other things.
Einstein got rid of all reference frames for
space and time. There was no longer some universal
space in which physics happened. All measurements
became relative to the position and speed
of the observer.
Space and time became one mathematically continuous
spacetime. So an event at one time for observer
A could take place at a completely different
time for observer B.
And the only constant in the entire system
became the speed of light—which classical
physics predicted could change!
From special relativity followed the equivalence
of mass and energy proof. Which was also mind-blowing.
It’s probably the most memorable physics
formula ever, since it’s printed on mugs
and T-shirts the world over: E = mc2. Or,
energy equals mass times the speed of light,
squared. Or, mass and energy can be converted
into each other!
Or, as Einstein said: “…mass and energy
are both but different manifestations of the
same thing—a somewhat unfamiliar conception
for the average mind.”
Now, it’s important to note that Einstein’s
new system of physics is simply a different
system than Netwon’s. “Mass” and “energy”
mean something different in the two systems—because,
to put it bluntly, Newton’s system turns
out to be not so universal. It only seems
to work on earth, because we aren’t particularly
massive or fast-moving, compared to stars.
Thanks Thought Bubble. We don’t have time
to explain all of the cool science that Einstein
and his generation of physicists did around
World War One, but two things stand out:
In 1915, Einstein published the theory of
general relativity. Special relativity was
all about comparing physical effects from
different observer positions in terms of velocity,
or speed in a particular direction.
General relativity provided all of the complicated
math regarding relativity and acceleration,
or speeding up or down.
General relativity explains the physics of
all situations. Special relativity is one
specific case of general relativity.
General relativity nailed the coffin shut
on the classical, Euclidean worldview: now gravity
itself was shown not to be a force like light,
but an effect, a distortion in the shape of
space due to mass…
So the planets didn’t follow certain paths
because of the attraction of the sun’s gravity,
but because the space before them was curved
by the sun’s mass.
Einstein’s universe wasn’t a series of
perfect spheres in an ether, but a void whose
very dimensions—whose rules, basically,
other than the speed of light—could change.
Many of his colleagues initially objected
to this, but Einstein was confident—and
patient. Astronomers awaited a solar eclipse
in 1919, that allowed them to experimentally
confirm Einstein’s theory.
The confirmation of gravitational lensing made
Einstein a scientific hero and an icon of
pop culture. As The Times of London reported,
“Newtonian Ideas Overthrown.”
The second major act of science Einstein did
around World War One was contribute to the
birth of modern particle physics. This story
is about, in part, Einstein getting it wrong.
In 1911, Ernest Rutherford and Danish physicist
Niels Bohr [“NEELS BOAR”] theorized a
model of the atom with electrons zipping around
a heavy nucleus. Scientists began to study
the physics of the very small, just as Einstein
was working out the physics of the very large.
But over the 1920s, these particle physicists
saw a lot of weird quantum or particle-like
effects.
Basically, Bohr’s Copenhagen group showed
that very small particles tend to act like
particles sometimes but like waves at other
times. Like waves, their behaviors have probabilities.
But when measured, individual particles are,
well particles. They are or aren’t there.
In 1926, two German physicists worked out
the math behind these quantum mechanics: Werner
Heisenberg invented matrix mechanics, which
[large exhale] are complex and Erwin Schrödinger,
wave mechanics. And lots of dead/not-dead
cat jokes.
Because, in 1927, Heisenberg proposed his
uncertainty principle: any observer can detect
the position or velocity of any quantum particle,
at any given time interval, but not both at
the same time.
Einstein haaated this. He believed in a universe
ordered by an ultimate rationality, and he
famously quipped, “God doesn’t play dice
with the world.” But Al, who had contributed
in lots of ways to the emerging model of atoms
and particles of energy, was wrong about uncertainty.
By the 1930s, Einstein was easily the most
famous scientist since Darwin. There was just
one problem. He was still Jewish. And living
in Germany.
So in 1933, Einstein renounced his German
citizenship and took a professorship at Princeton.
As a celebrity genius with intimate knowledge
of the cutting-edge of German science—and
perfect hair—Einstein had the ears of politicians
anxiously planning for another great war in
Europe.
And, after one of his physicist buddies demonstrated
that an atom could be straight-up, stone-cold
split open, Einstein felt that he had a moral
obligation to explain to the American establishment
just how powerful atomic energy could be…
We’ll pick up this thread next time.
Suffice to say, World War Two eventually ended,
and a new Cold War started—with scientific
discovery, especially in the physics that
Einstein had created, as the new measuring
stick of imperial might.
Israel offered Einstein the presidency, which
he turned down. He lived the rest of his life
in the home of technological innovation and
“fat sandwiches”—New Jersey.
Einstein always regretted that his work was
used for violent ends. In fact, he was generally
skeptical of modernity. Way back during World
War One, he wrote: “Our entire much-praised
technological progress, and civilization generally,
could be compared to an axe in the hand of
a pathological criminal.”
And yet, in the end, even the horrors of two
world wars never shook his faith that there
was great meaning in the universe—a code
to be deciphered by science.
He died never quite accepting quantum randomness,
and believing that, one day, humans would
crack the code.
Next time—the Americans use Einstein’s
world-threatening Bomb, and warfare changes
forever. It’s the birth of nuclear physics,
the end of World War Two, and the beginning
of  the Cold War.
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