THE TIME HAS COME
 TO LOOK AHEAD

 FOR A PREVIEW OF WHAT LIES
 BEYOND THE MECHANICAL UNIVERSE.

I have a wonderful story 
to tell you a little later.

Right now,I'd like to
whet your appetite for it.

A long time ago,
I read to you a letter

that ALBERT EINSTEIN wrote
in1912

to his friend 
ARNOLD SOMMERFELD.

It goes like this.

"I occupy myself exclusively
with the problem of gravitation"

"And now believe that I will
overcome all difficulties."

"But this one thing is certain."

"In all my life, I have never
labored as hard,

"And I have become imbued with
a great respect for mathematics,

"The subtle parts of which,
in my innocence,

I had till now regarded
as pure luxury."

That's a typical physicist'
attitude towards mathematics.

Mathematics is a tool
to be used for other purposes.

The details
of the mathematics themselves

are of little or no interest.

But Einstein had found out,
to his dismay,

That that wasn't always true.

The mathematical basis

of Einstein's general theory
of relativity

was something called
the tensor calculus.

It had been worked out
10 or 15 years before

by two Italian mathematicians,

one of whom was named
TULLIO LEVI-CIVITA.

In 1914, Einstein wrote
his first paper

on the new theory.

Another physicist
named MAX ABRAHAM

who had a rival theory
of his own

tried to read Einstein's paper,
and he couldn't understand it.

It was too difficult.

To get some help,
he set it to LEVI-CIVITA.

LEVI-CIVITA read the paper

and thereby became interested
in the theory of relativity.

In 1915, LEVI-CIVITA wrote
a letter to Albert Einstein

telling him that there was
something wrong with his theory.

You can imagine how Einstein
must have felt about that.

He was struggling to master
this very difficult mathematics,

finally getting up
enough courage

to write his first paper
using it,

and the guy that invented
the mathematics

says he got it wrong.

The issue involved
was a particular tensor--

A tensor is a kind
of generalized vector--

A tensor that represented
the electromagnetic field.

The question was
how that tensor changed

in going from one
coordinate sysytem to another.

LEVI-CIVITA said
Einstein had it wrong.

It turned out that
Einstein was right

and Levi-Civita was wrong

This was a physics theory.
Einstein was a physicist,

and his physical intuition
told him

what the answer had to be.

But the mathematical steps
in his proof were shaky.

That's the point at which
Levi-Civita had attacked him.

The technical details
of that controversy

are not what
we'll be interested in.

We'll be interested in
the subtleties and nuances

of the relationship that
developed between the two men.

To the average person,

the fact that Albert Einstein
didn't consider himself

to be an accomplished
mathematician

may come as
a considerable surprise.

After all, he had a remarkable
command of mathematics

compared to the average
physicist of his day.

Much less the average person
of his or any other day.

What he really meant was that
his grasp of mathematics

was no match for the brilliant
Italian, Tullio Levi-Civita.

So Einstein's perception
was a relative one.

But then, Einstein was
the master of relativity.

Of course, in earlier times,
there had been no distinction

between mathematicians
and physicists.

Since ancient times,
astronomy and computation,

mechanics and geometry

could be thought of as parts
of the same profession.

AND YET, THERE HAD ALWAYS BEEN
CERTAIN INDIVIDUALS

WHO, LIKE EINSTEIN, 
HAD A SPECIAL INTUITION

ABOUT HOW THE WORLD
REALLY WORKS.

IN THE 19th CENTURY,

A NEW TERM WAS PHYSICIST.

BUT EVEN BEFORE
IT HAD A NAME,

THE SCIENCE OF PHYSICS
HAD BEEN ADVANCED

BY TWO INDIVIDUALS

WHOSE COMMAND OF MATHEMATICS
WASN'T JUST WEAK--

IT WAS VIRTUALLY NONEXISTENT.

ONE OF THEM WAS THE HONORABLE
BENJAMIN FRANKLIN

OF PHILADELPHIA,PENNSYLVANIA,
A COLONY OF ENGLAND

IN THE RATHER
UNCIVILIZED AMERICAS

THE OTHER, WHO WAS BORN
AT ABOUT THE TIME

THAT PENNSYLVANIA WAS NO LONGER
ANYONE'S COLONY,

WAS MICHAEL FARADAY.

QUEEN VICTORIA'S ENGLAND--

WITHOUT A PROPER EDUCATION.

MICHAEL FARADAY
FOUND IT DIFFICULT

EVEN TO GET HIS FOOT
IN THE DOOR.

BUT ONCE ESTABLISHED
WITHIN THE ROYAL INSTITUTION,

MICHAEL FARADAY FOUND
A SATISFACTION

THAT COMES ONLY
FROM THE PURSUIT AND DISCOVERY

OF ORIGINAL SCIENTIFIC IDEAS.

AND THOUGH ILL-EQUIPPED
IN MATHEMATICS,

FARADAY WOULD DO
AS MUCH AS ANYONE

TO PROPEL SCIENCE
BEYOND THE MECHANICAL UNIVERSE

OF ISAAC NEWTON.

NEWTON'S LAWS OF MECHANICS,

TOGETHER WITH HIS THEORY
OF THE FORCE OF GRAVITY,

HAD CONVINCED
THE WORLD OF SCIENCE

THAT THE WORLD COULD BE
UNDERSTOOD BY RATIONAL MEANS.

ALONG THIS SAME PATH,

NEWTON'S FOLLOWERS WOULD
DISCOVER THAT LIKE GRAVITY,

ELECTRICITY AND MAGNETISM
ARE ALSO FORCES

THAT DECREASE WITH THE SQUARE
OF THE DISTANCE.

THE SIMILARITY WAS AMAZING.

AND TO BOTH FARADAY

AND THE SCIENTIFIC COMMUNITY
AT LARGE,

IT POSED ONE OF THE SIGNIFICANT
QUESTIONS IN PHYSICS--

WHETHER GRAVITATIONAL,
ELECTRIC, OR MAGNETIC,

HOW COULD ANY FORCE
ACT BETWEEN BODIES

WHEN THEY WEREN'T EVEN TOUCHING?

HERE FARADAY'S INTUITIVE POWER
REALLY SHONE,

FOR AT THIS POINT HE IMAGINED
THAT A 1/R-SQUARED FORCE

MUST BE APPLIED BY SOMETHING
THAT RADIATED OUTWARD,

LIKE SUNLIGHT.

SEEING EVEN FURTHER,

FARADAY CONCEIVED OF
LINES OF FORCE,

STARTING ON POSITIVE CHARGES
AND ENDING ON NEGATIVE ONES.

AND EVERYWHERE THEY WENT,

WHICH WAS EVERY WHERE
IN THE UNIVERSE,

THEY CARRIED THE POWER
TO ATTRACT AND REPEL.

FARADAY'S IMAGE
OF MAGNETIC FORCES

WAS NO LESS VIVID THAN
HIS PERCEPTION OF ELECTRICITY.

ONE DAY,
MICHAEL FARADAY'S VISIONS

WOULD BECOME THE PICTURE

OF THE ELECTRIC
AND MAGNETIC FIELD.

BUT HIS COLLEAGUES,

EACH FAR MORE MATHEMATICALLY
SOPHISTICATED THAN HE,

DEMANDED A MORE RIGOROUS
EXPRESSION OF HIS IDEAS

THAN PURE INTUITION.

OBVIOUSLY,MATHEMATICAL STEPS
HAD TO BE TAKEN.

AND THEY WERE--

IN GERMANY BY GAUSS
AND IN FRANCE BY AMPERE.

BUT NOBODY STRODE MORE
GRACEFULLY THROUGH MATHEMATICS

NOR UNDERSTOOD LINES OF FORCE
MORE CLEARLY

THAN JAMES CLEAK MAXWELL

HIS WAS THE MOST PENETRATING
INSIGHT INTO FARADAY'S IDEAS,

AND WITH AN ENORMOUS EFFORT,
HE TRANSFORMED THEM

INTO THE ELECTROMAGNETIC
FIELD THEORY.

THE FOUR LAWS
OF ELECTRIC AND MAGNETIC FIELDS

THAT REMAIN AS VALID TODAY
AS THEY WERE

THE DAY JAMES CLEAK MAXWELL
WROTE THEM DOWN.


THE FRUITS OF BOTH MAXWELL
AND FARADAY'S WORK BLOOMED

DURING THE INDUSTRIAL AGE
AND THE ELECTROMAGNETIC ERA,

BUT ONLY BECAUSE THE SEEDS
HAD ALREADY BEEN SOWN

BY SOMEONE ELSE
IN A DISTANT LAND.

HE'D FIRST MADE A NAME
FOR HIMSELF AS A PRINTER,

THEN AN INDELIBLE MARK
ON THE AFFAIRS OF STATE.

BUT IN HIS PRIME,

BENJAMIN FRANKLIN MADE
SOME REMARKABLE ACCOMPLISHMENTS

IN THE FIELD OF SCIENCE.

IN FRANKLIN'S DAY,
THE FIELD OF ELECTRICITY,

LIKE THE NEW WORLD ITSELF,
WAS GREEN AND UNDEVELOPED.

IN FACT, ALL THE WORLD'S
KNOWLEDGE ABOUT ELECTRICITY

COULD FIT INTO A LEYDEN JAR.

THE LEYDEN JAR WAS
THE WORLD'S FIRST MEANS

OF STORING ELECTRICITY

AND BENJAMIN FRANKLIN
USED IT

TO REVOLUTIONIZE PHYSICS
SINGLE-HANDEDLY.


IT WAS WITH LEYDEN JARS,
NOT LIGHTNING BOLTS,

THAT FRANKLIN MADE
HIS MOST IMPORTANT DISCOVERIES.

HE CORRECTLY OBSERVED

THAT IF ONE OBJECT
HAS A POSITIVE CHARGE,

THEY WILL ATTRACT
EACH OTHER.

BUT IF BOTH OBJECTS
ARE POSITIVELY CHARGED,

THEY REPEL EACH OTHER.

IN FACT, BENJAMIN FRANKLIN
INVENTED THE VERY TERMS

POSITIVE CHARGE
AND NEGATIVE CHARGE.

BUT WHAT EXACTLY
IS ELECTRIC CHARGE?

AND WHAT ARE THE FACTORS

THAT DETERMINE HOW ELECTRICITY
DOES ITS WORK?

PLAYING IT SAFE WITH ELECTRICITY

MEANS UNDERSTANDING
A NUMBER OF QUANTITIES,

NOT JUST CHARGES, BUT ALSO
VOLTS AND AMPS AND FIELDS,

TO NAME JUST A FEW.

BUT NO MATTER WHICH QUANTITY
IS ON THE TABLE,

IT'S ALWAYS TAKEN SOMETHING
TO GET ELECTRICITY STARTED

SINCE 1800, ONE WAY HAS BEEN
THE ELECTRIC BATTERY.

GIUSEPPE GALVANI, THE WORLD'S
FIRST NEUROBIOLOGIST,

STARTED IT ALL BY ASKING
A SIMPLE QUESTION--

HOW CAN A FROG'S LEG,
WITHOUT THE BENEFIT OF A FROG,

HAVE SUCH A LARGE REACTION

TO SUCH A SMALL
ELECTRICAL IMPULSE?

HIS COLLEAGUE, ALESSANDRO VOLTA,
FOUND THE ANSWER,

AND BY THE TIME
HE HAD IT ALL WORKED OUT,

HE'D ALSO INVENTED
THE ELECTRIC BATTERY.

OF COURSE, THE BATTERY'S COME
A LONG WAY

SINCE VOLTA MADE
HIS VOLTAIC PILE

WITH VARIOUS METALS SEPARATED BY
THE ODD SCRAP OF CLOTH, CLAY,

OR ALMOST ANYTHING
THAT WAS HANDY AND MOIST.

BUT ALTHOUGH THE BATTERY
COULD GET ELECTRICITY FLOWING,

IT WOULD TAKE SOMETHING
CONSIDERABLY MORE POWERFUL

TO TURN THE WHEELS
OF COMMERCE AND INDUSTRY.

FOR EXAMPLE, CONSIDER
THE ROUNDABOUT PROGRESS

OF THE DUTCH.

IN HOLLAND, THEY MADE PROFITS
ANYWHERE WIND ROSE

AND WATER FLOWED.

THROUGHOUT THE WESTERN WORLD,

THIS ENERGY SOURCE WAS HAILED
AS THE WAVE OF THE FUTURE.

BUT BUSINESS CONDITIONS
TEND TO CHANGE...

AND CHANGE THEY DID,

WHEN THE STEAM ENGINE
CAME ALONG.

AT PRECISELY THE SAME TIME
IN HISTORY,

COAL WAS BEING ADDED
TO THE EQUATION

OF ENERGY SOURCES
AND INDUSTRIAL POWER

COAL PROVED TO BE
MORE RELIABLE THAN WIND

AND EASIER TO TRANSPORT
THAN WATER.

BUT A DIFFERENT ELEMENT

WOULD SOON ENTER THE PICTURE
OF INDUSTRIAL POWER.

IT WAS ELECTRICITY,

AND NO ONE HAD A BETTER GRASP
OF IT THAN MICHAEL FARADAY.

HE INVENTED A DEVICE
THAT TWISTED

BECAUSE OF THE MAGNETIC FIELD
CREATED BY AN ELECTRIC CURRENT.

THIS WAS THE WORLD'S FIRST
ELECTRIC MOTOR.

BUT FARADAY WENT
MUCH FURTHER.

IF AN ELECTRIC CURRENT
CREATES MAGNETISM, HE WONDERED,

COULD A MAGNETIC FIELD
CREATE ELECTRICITY?

BY WAY OF AN ANSWER,

FARADAY DISCOVERED
ELECTROMAGNETIC INDUCTION.

BY INCREASING OR DECREASING
THE CURRENT

IN ONE ELECTRIC CIRCUIT,

THE CHANGING MAGNETIC FIELD
HE CREATED

INDUCED A CURRENT TO FLOW
IN A SECOND CIRCUIT.

AND TO ONE MAN,

THAT IMAGE WOULD SUGGEST
UNLIMITED POSSIBILITIES.

HIS NAME WAS NIKOLA TESLA.

ADDING AN INGENIOUS TWIST
TO FARADAY'S DISCOVERY,

HE CAME TO AMERICA TO CREATE
A VAST ELECTRICAL POWER GRID


AND TO SPIN LIKE A DYNAMO
INTO THE MODERN INDUSTRIAL AGE.

IN THEORY--THE THEORY
OF ALTERNATING CURRENT--

IT WAS SMOOTH SAILING
FOR TESLA.

BUT IN PRACTICE, TESLA MET WITH
THE MOST POWERFUL RESISTANCE

ON THE AMERICAN LANDSCAPE.

THOMAS EDISON SEEMED TO BE
THE FORCE

BEHIND JUST ABOUT EVERY
BRIGHT IDEA UNDER THE SUN--

THE PHONOGRAPH,
THE MOTION PICTURE CAMERA,

THE TICKER TAPE,
AND OF COURSE, THE LIGHT BULB.

BUT UNLIKE THE GLOW
HE'D PUT IN THIS HISTORIC HOUSE,

THE GLOW IN HIS HEART
WAS FAINT INDEED

TOWARD TESLA AND HIS IDEA
OF ALTERNATING CURRENT

BECAUSE EDISON FELT
THAT IT WAS DIRECT CURRENT

THAT WOULD PROPEL AMERICA
INTO THE FUTURE.

BUT THE SO-CALLED
WAR OF THE CURRENTS

WASN'T THE ONLY
CONTROVERSY BREWING

IN THE LATE 19th CENTURY

THE YEAR WAS 1887.

THE PLACE--CLEVELAND, OHIO.

AND THE EXPERIMENT--

THE EARTHSHAKING
MICHELSON-MORLEY EXPERIMENT--

WAS DESIGNED TO DETECT
THE MOTION OF THE EARTH

THROUGH THE LUMINIFEROUS ETHER,

THE MEDIUM THAT WAS SUPPOSED TO
CARRY LIGHT

FROM THE SUN TO THE EARTH.

THE METHODS WERE CONCEIVED
BY ALBERT A. MICHELSON.

NO EXPERIMENT IN HISTORY had been thought out better
and executed with more care.

Not since Galileo had so much
ridden on a scientific idea.

Galileo said that 
if nothing comes along

to interfere with it,

an object in motion 
would remain in motion.

That was the law of inertia.

It meant there could be
no absolute state of motion

and no absolute
state of rest.

And then Michelson set out
to disprove that fact.

He was the best 
and the brightest,

the first American physicist
to win the Nobel prize,

and he failed.

Of course, not finding
the absolute motion of the earth

wasn't the only failure
in scientific history,

but it was absolutely
the most brilliant.

for one thing, it meant
that all observers,

regardless of 
their own motion,

measure the same
speed of light.

And if the speed of light's
the same for all observers,

it would be impossible
to figure out one's motion

by measuring it.

If that were true,
when it came to time and space,

people could wave good-bye
to conventional wisdom.

Not that train schedules
would change,

nothing so mundane as that.

But someone was rewriting
the itinerary of physics.

Soon everything that anyone
had taken for granted

was about to be derailed,
past, present, and forevermore.

He'd been
a relatively poor student,

perhaps because the work
was too hard or too easy

or because his views
were too unconventional

from the start.

For a quarter of a century,
his life remained uneventful,

at least on the surface.

But in 1905, while working as
a patent official

in Switzerland,

this man saw the universe
more dramatically

than anyone since Isaac newton.

He was Albert Einstein,

and relativity, 
his way of seeing things,

changed the meaning
of time and space.

If a light is switched on
as a train passes,

it reaches the front
and the rear at the same time.

Well, that's one man's opinion.

But consider
an outsider's point of view.

In Einstein's relativity,

events that are simultaneous
to one observer

may happen at different times
according to someone else.

And to see both points of view
together

requires combining
space and time

in a single 
four-dimensional continuum.

Looking at the world freshly,

and as no one ever had,

Albert Einstein saw

that according to
any observer at rest,

a moving clock must actually
run slow,

and that moving rulers
are contracted.

And for that matter,
he saw much

that would change
human perceptions

about the way of the world.

For example, a set of twins,
Albert and henry,

born in the same
time and space,

are, on the surface,
very much alike.

And yet, on the inside,

they may turn out as different
as night and day.

Being different
and at the same time so alike

may be the ultimate paradox
of identical twins.

In physics, however,

the twins paradox takes off
with another image.

This is henry's
first time away from Albert.

His destination--

the planet zog,
10 light-years away.

If he could compare his clock
to his twin brother's,

he'd find Albert's clock
running slower.

If Albert could compare
his clock to henry's,

he'd find it running slow.

No matter how it looks,
that spells paradox.

But when it comes 
right down to it,

what does that 
and countless other mysteries

throughout the mechanical
universe mean?

It means a journey
into the atom itself,

into electricity and magnetism,

relativity, thermodynamics,
and more--

into a realm
previously unimagined.

It's a realm where
even the laws of Isaac newton

have to give way to new
and more profound insights,

giving birth to a new science,

a science that would come
to be called quantum mechanics.

In all, it's an adventure
that's called

the mechanical universe
and beyond.

Beyond all else,
from beginning to end,

it's the story
not only of laws and principles,

but of the people
who discovered them.

OK, let's get back now
to Einstein and Levi-civita.

That first letter
I mentioned

from Levi-civita
to Albert Einstein

doesn't exist anymore.

In all the correspondence,

we have all the letters
Einstein wrote

and none written
by Levi-civita,

with one exception,
which you'll understand later.

The reason is
because Levi-civita,

being a meticulous
mathematician,

saved every letter
he ever received.

But Albert Einstein,

who had a different sort
of character,

threw everything away.

That doesn't matter.

It's easy to reconstruct
the entire correspondence

from the letters we have
written by Einstein.

The correspondence
was very intense--

many letters exchanging hands
in a very short time.

In fact, so quickly

that it couldn't possibly
happen today

because the mail service
isn't good enough.

But it was possible
in 1915.

We don't have
the first letter,

but we have 
the first reply,

Einstein writing back
to levi-civita,

who had written to him
criticizing his work.

Einstein writes,

�ghighly esteemed colleague,

�gyou give me 
  great pleasure

�gby paying such meticulous
  attention to my work.

�ghow seldom it is
  that someone

�gwith independent
  and critical perspective

�gconcerns himself in detail
  with this subject.

�gWhen you directed
  your attack

�gagainst the most important
  proof of my theory,

�gpurchased with streams
  of sweat,

�gI was alarmed,

�gespecially knowing you master
  these mathematical things

�gbetter than I.

�gAfter thorough consideration,
  I nevertheless believe

I'm able to maintain
my proof.�h

The second letter
from einstein to levi-civita

is dated
just 12 days later.

In that letter, we start
to see the beginning

of the relationship

that develops
between the two men.

He writes,
�gI would be very glad

�gif you would write to me
  next time in italian.

�gAs a young man, I spent
  half a year in italy.

I had the pleasure
of visiting padua.�h

levi-civita was a professor
at the university of padua.

�gI still enjoy making use
  of the italian language.

�gI could not muster
  enough courage

�gto write to you
  in italian,

as it would be clumsy
and unclear.�h

Undoubtedly, einstein wanted 
to get a letter in italian,

but he's doing something else.

He's busy seducing
levi-civita.

In the next letter
from einstein,

we can see
the results of that.

He says,
�gmy dear colleague,

�gI received your letter
  of March 23th

�gwhich was written
  in the familiar italian

�gI have missed
  for so long.

�gYou cannot imagine
  my pleasure

�gin receiving such
  a genuine italian letter.

It makes beautiful memories
of my youth come alive.�h

In the next line,
we find out

that levi-civita knew
how to play the same game.

einstein says,�gyou make it
nice in your letters.

�gYou pat me
  in a friendly way

�gso that I, when reading
  your new objections,

don't make 
an ill-humored face.�h

In the next letter, we find out
why there still exists

one of the letters
from levi-civita to einstein.

Einstein writes,
�gyour letter of March 28th�h--

five days later--

�ghas interested me
  extraordinaly.

�gFor 1 1/2 days I had to think
  continually

�guntil I had clearly understood
  how your example

�gcould be brought into harmony
  with my proof.

I enclose your letter
so I can refer to it.�h

That's why we still have
that letter.

In that letter, there is
one of the loveliest postscripts

in any scientific
correspondence anywhere.

einstein writes, �gI have never 
had a correspondence

�gas interesting as this before.

You should see how
I look forward to your letters.�h

Unfortunately, all of this
is taking place

in the spring of 1915.

In a very short time,
italy and germany were at war,

and there was no way

for einstein and levi-civita
to exchange letters anymore.

The two of them
didn't correspond again

for two years, until 1917,

when levi-civita received
a post card from switzerland.

The post card said,

�gupon my arrival,
  I found your beautiful new works

�gand took them with me
  at once.

�gI admire the elegance
  of your method of calculation.

�gIt must be nice
  to ride through these fields

�gupon the horse
  of true mathematics,

while the likes of us
must make our way on foot.�h

All of this, and the two men
had never met each other.

But it's clear that
after the beginning,

the controversy itself
became unimportant to them.

They just wanted an excuse
to keep up the correspondence

that they both enjoyed so much.

They finally did meet each other
personally in 1921,

when einstein was invited
to bologna

to give a series of lectures.

later on, einstein moved
to the united states,

where he lived in princeton.

In 1936, he invited levi-civita
to come to princeton,

and the two of them
spent a year together.

But by that time, the world
had begun to go berserk again,

and the clouds of war
were gathering once more.

Levi-civita returned to italy.

In 1938, when racial laws
were passed

by the italian
fascist goverment,

levi-civita, who was jewish,
lost his professorship,

lost his membership
in all scientific societies,

and eventually died,

isolated from the rest
of the scientific world

in his apartment in rome
in 1941.

Later, when einstein was asked
what he liked best about italy,

he said,
�gspaghetti and levi-civita.�h

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Captions copyright 1986
california institute
of technology,

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was provided by...

The mechanical universe
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