>> Sreenivasan: THE TERM
"QUANTUM MECHANICS" DESCRIBES
THE STRANGE DOINGS OF THE
TINIEST PARTICLES IN THE
UNIVERSE.
WHERE, FOR EXAMPLE, TWO OBJECTS
CAN OCCUPY THE EXACT SAME SPACE
AT THE SAME TIME.
OR AFFECT EACH OTHER, EVEN
THOUGH THEY'RE MILLIONS OF MILES
APART.
BUT IF THAT SOUNDS OUTLANDISH,
HOLD ON TO YOUR HAT.
WITHIN THE REALM OF QUANTUM
MECHANICS THERE IS A HIGHLY
ABSTRACT AND CONTROVERSIAL
THEORY KNOWN AS "MANY WORLDS."
IT DESCRIBES THE IDEA THAT WITH
EVERY DECISION YOU MAKE AN
ENTIRELY NEW UNIVERSE SPRINGS
INTO EXISTENCE, CONTAINING A NEW
VERSION OF YOURSELF.
AS BIZARRE AS IT SOUNDS, SOME
THEORETICAL PHYSICISTS BELIEVE
THAT MANY WORLDS IS AN EXACT
DESCRIPTION OF REALITY.
SEAN CARROLL HAS STAKED HIS
REPUTATION ON IT.
HE'S A BEST-SELLING AUTHOR AND A
PROFESSOR OF PHYSICS AT THE
CALIFORNIA INSTITUTE OF
TECHNOLOGY.
NEWSHOUR WEEKEND'S TOM CASCIATO
RECENTLY VISITED HIM AT CALTECH
TO DISCUSS HIS LATEST BOOK AND
ITS IMPLICATIONS NOT JUST FOR
PHYSICS, BUT FOR ALL OF US.
>> THE SIMPLEST SYSTEM THAT WE
CAN IMAGINE IS A SINGLE,
SPINNING PARTICLE.
>> Reporter: TO SPEAK WITH
CALTECH THEORETICAL PHYSICIST
SEAN CARROLL ABOUT QUANTUM
MECHANICS IS TO CONFRONT A BASIC
CONTRADICTION.
SEAN, YOU'VE WRITTEN THAT ONE OF
THE PREMISES OF SCIENCE IS THAT
IT RENDERS THE WORLD
INTELLIGIBLE.
YOU'VE ALSO WRITTEN THAT QUANTUM
MECHANICS TELLS US THAT WHAT WE
SEE ISN'T WHAT'S REALLY
HAPPENING.
THAT ALREADY STARTS TO SOUND A
LITTLE UNINTELLIGIBLE.
>> WELL, IT IS.
I THINK THAT QUANTUM MECHANICS
HISTORICALLY IS THE GREAT
BETRAYAL OF THE GOAL OF SCIENCE,
WHICH IS TO UNDERSTAND HOW THE
WORLD WORKS, RIGHT?
>> Reporter: AND THAT'S THE
PROBLEM, SAYS CARROLL.
WHILE SCIENTISTS USE QUANTUM
MECHANICS ALL THE TIME-- IT'S
MADE POSSIBLE THE TRANSISTOR,
THE PERSONAL COMPUTER, THE LASER
AND MUCH MORE-- THEY DON'T
REALLY UNDERSTAND IT.
HE LAYS IT ALL OUT IN HIS NEW
BOOK, "SOMETHING DEEPLY HIDDEN."
>> THE PROBLEM IS WHAT'S CALLED
THE MEASUREMENT PROBLEM, RIGHT?
YOU KNOW, WE ALWAYS TALK ABOUT
AN ELECTRON FOR EXAMPLE, AN
ELEMENTARY PARTICLE.
WE SAY, WELL, IT HAS A POSITION
YOU KNOW, THERE IT IS.
>> Reporter: WHEN I WAS A KID IN
SCIENCE CLASS, THEY SHOWED THE
LITTLE NUCLEUS AND THEN THE
ELECTRONS WERE GOING AROUND IT.
>> YUP.
>> Reporter: THAT'S NOT WHAT'S
HAPPENING?
>> LIED, YOU WERE LIED TO,
RIGHT.
IN QUANTUM MECHANICS THERE'S NO
SUCH THING AS THE POSITION OF
THE ELECTRON.
WHAT THERE IS IS WHERE YOU WOULD
SEE IT WERE YOU TO LOOK, AND WE
REALLY HAVE TROUBLE WRAPPING OUR
BRAINS AROUND THAT CONCEPT.
SO HERE YOU ARE, AND YOU HAVE
NOT YET OBSERVED THE PARTICLE.
>> Reporter: IN FACT, THAT
CONCEPT LED TO A SPLIT IN THE
PHYSICS COMMUNITY.
ON ONE SIDE, SAYING THE THEORY
THAT THE OBSERVER IS CRITICAL TO
THE POSITION OF A PARTICLE WAS
THE FAMED DANISH PHYSICIST,
NOBEL-PRIZE WINNER NIELS BOHR.
IT'S KNOWN AS THE "COPENHAGEN
INTERPRETATION."
CARROLL WRITES THAT NO LESS A
SCIENTIST THAN ALBERT EINSTEIN
WAS UNSATISFIED WITH THE
COPENHAGEN INTERPRETATION.
BOHR'S AND EINSTEIN'S
DISAGREEMENT WAS DRAMATIZED IN
THE NATIONAL GEOGRAPHIC SERIES,
"GENIUS."
>> IT FUNCTIONS.
AND IT ALLOWS US TO MAKE USE OF
THE QUANTUM WORLD.
>> THE GOAL OF SCIENTIFIC
PURSUIT SHOULD NOT BE MERELY TO
MAKE USE OF THE WORLD AROUND US.
IT SHOULD BE TO UNDERSTAND IT
FUNDAMENTALLY.
>> Reporter: IN THE END NIELS
BOHR PREVAILED.
>> AND HE DECISIVELY WON THE
PUBLIC RELATIONS BATTLE.
EINSTEIN SORT OF SAT IN HIS
OFFICE IN PRINCETON, WOULD
OCCASIONALLY WRITE A PAPER,
WROTE A LOT OF LETTERS TO HIS
FRIENDS, BUT IN THE PHYSICS
COMMUNITY BOHR WAS JUST GIVEN
THE VICTORY PRIZE.
LIKE, OKAY, WE'RE GOING TO DO
WHAT YOU SAY.
IT GOT SO BAD THAT, YOU KNOW
PEOPLE WERE PUSHED OUT OF THE
FIELD IF THEY TRIED TO QUESTION
THE QUANTUM DOGMA.
>> Reporter: SO THE DOGMA THAT
HAD HARDENED UNDER NIELS BOHR
WAS THAT THE OBSERVER WAS THE
IMPORTANT THING, THAT THERE WAS
AN ELEMENT TO QUANTUM MECHANICS
THAT INVOLVED OBSERVATION.
>> ABSOLUTELY, SO THE DOGMA SAYS
THAT THE ACT OF OBSERVATION IS
CRUCIAL, BUT THEN YOU SAY WELL
OKAY.
WHAT COUNTS AS AN OBSERVER.
DOES IT HAVE TO BE A HUMAN
BEING?
COULD IT BE A CAT?
WHAT ABOUT A ROCK?
WHAT IF I JUST, LIKE, GLANCED AT
THE SYSTEM RATHER THAN LOOKING
AT IT DIRECTLY, AND THE
COPENHAGEN INTERPRETATION SAYS
NO, NO, NO.
DON'T ANSWER THOSE QUESTIONS.
>> Reporter: REALLY, DON'T
ANSWER THOSE QUESTIONS?
>> WE HAVE NOTHING TO SAY ABOUT
THAT.
IT'S OBVIOUS WHAT AN OBSERVER
IS.
LET'S GET ON WITH OUR LIVES.
>> Reporter: SEAN CARROLL IS
AMONG A GROUP OF THEORETICAL
PHYSICISTS WHO REJECT THE
ORTHODOXY, AND REFUSE TO JUST
"GET ON WITH THEIR LIVES."
THEY CALL THEMSELVES
"EVERETTIANS," AFTER A LESSER
KNOWN 20th CENTURY AMERICAN
PHYSICIST WHO CARROLL THINKS
SHOULD BE A LOT BETTER KNOWN.
HIS NAME WAS HUGH EVERETT.
>> HUGH EVERETT WAS A GRADUATE
STUDENT AT PRINCETON.
AND HUGH EVERETT, CAME ALONG
SAYING "WELL, WHAT IF WE STUDIED
THE WHOLE UNIVERSE AS A QUANTUM
MECHANICAL SYSTEM, THEN WE
WOULDN'T HAVE A SYSTEM AND AN
OBSERVER, WE ONLY HAVE THE
SYSTEM."
SO EVERETT SAID WE NEED TO
UNDERSTAND QUANTUM MECHANICS IN
AND OF ITSELF.
AND HE REALIZED THAT THAT
IMPLIED THE EXISTENCE OF MANY
WORLDS.
AND, YOU KNOW, EVERETT GOT
TREATED VERY BADLY.
HE GOT RIDICULED.
HE WAS TOLD HE DIDN'T UNDERSTAND
QUANTUM MECHANICS, AND WE
FIGURED THIS OUT 20 YEARS AGO,
THE WHOLE BIT.
SO HE DIDN'T EVEN APPLY FOR A
FACULTY JOB AS A PHYSICIST.
HE LEFT AND WORKED IN THE
DEFENSE INDUSTRY.
BUT WE'VE LEARNED A LOT MORE
ABOUT HOW QUANTUM MECHANICS
WORKS SINCE THE 1950s.
SO IN FACT IN MY MIND EVERYTHING
WE'VE LEARNED HAS MADE HIS CASE
STRONGER.
AND WE LOOK AT AND SAY YES, I
SEE THE WORLDS, THERE THEY ARE.
I SEE THEM IN MY MATH.
I DON'T SEE THEM IN MY
TELESCOPES OR MICROSCOPES.
>> Reporter: SO WHAT DOES THE
MATH TELL YOU ABOUT THE
UNIVERSE?
>> IT TELLS US THAT THE UNIVERSE
IS AN ABSTRACT MATHEMATICAL
STRUCTURE THAT EVOLVES IN A VERY
CERTAIN WAY AND WITH A VERY
REMARKABLE CONSEQUENCE THAT WHEN
YOU LOOK AT A QUANTUM SYSTEM,
WHEN YOU OBSERVE IT, DIFFERENT
COPIES OF YOUR UNIVERSE ARE
CREATED.
THE UNIVERSE YOU SEE AROUND YOU
IS A TINY, TINY SLIVER OF
EVERYTHING THAT THERE IS.
>> Reporter: HERE'S WHERE IT
STARTS TO SOUND REALLY CRAZY.
IN THE MANY WORLDS
INTERPRETATION, EVERY TIME YOU
MAKE AN OBSERVATION, A NEW
UNIVERSE SPLITS OFF FROM THE ONE
YOU WERE JUST IN.
DOES THAT MEAN THERE ARE NOW TWO
YOUS?
>> THERE'S A DIFFICULT QUESTION
IN MANY WORLDS AS TO HOW WE
SHOULD DEAL WITH PERSONAL
IDENTITY, RIGHT?
>> Reporter: IS IT LIKE THAT
90'S MOVIE "SLIDING DOORS,"
WHERE GWYNETH PALTROW CATCHES
THE TRAIN, BUT SHE ALSO MISSES
THE TRAIN?
SORT OF.
>> THE PEOPLE IN OTHER WORLDS
AREN'T ME.
THEY MIGHT HAVE COME FROM THE
SAME YOUNGSTER AS I DID.
>> Reporter: THEY MIGHT HAVE.
>> BUT THEY'RE A DIFFERENT
PERSON.
>> Reporter: SLOW DOWN.
WHAT DO YOU MEAN THEY MIGHT HAVE
COME FROM THE SAME YOUNGSTER
THAT YOU WERE?
>> SO, IN OTHER WORDS, IN MANY
WORLDS THERE WAS A YOUNGSTER.
THERE WAS A PERSON WHO I HAVE
DESCENDED FROM OVER THE LAST
SOME NUMBER OF YEARS, AND THE
WORLD HAS BRANCHED MANY, MANY
TIMES SINCE THEN, AND SO THERE
ARE OTHER PEOPLE IN THESE OTHER
WORLDS WHO WERE ME BACK THEN BUT
NOW THEY'RE DIFFERENT PEOPLE
BECAUSE THE WORLD HAS BRANCHED
SINCE THEN AND SO WE HAVE TO
EXPAND WHAT WE MEAN BY PERSONAL
IDENTITY BECAUSE YOUR WORLD LINE
IS A TREE, RIGHT?
IT'S LIKE YOU'RE AN AMOEBA THAT
BRANCHES AND SPLITS.
>> Reporter: IS THERE A PERSON
WHO USED TO BE ME, WHO IS THE
POINT GUARD FOR THE PORTLAND
TRAIL BLAZERS?
>> THERE IS.
YES.
>> Reporter: AT MY HEIGHT?
>> AND YOU WON THE N.B.A.
CHAMPIONSHIP.
YES.
>> Reporter: WITH MY LACK OF
PHYSICAL ABILITY.
>> YOU KNOW, SO, THIS, THIS IS
HINTING AT A CRUCIALLY IMPORTANT
PROBLEM FOR MANY WORLDS WHICH IS
HOW DO YOU WEIGH THE RELATIVE
LIKELIHOOD OF DIFFERENT THINGS
HAPPENING?
NOT EVERY WORLD IS CREATED EQUAL
IN SOME SENSE.
SO THE WORLDS THAT YOU THINK OF
AS CRAZY OR UNLIKELY REALLY ARE.
YOU ARE, AGAIN, LESS LIKELY TO
FIND YOURSELF IN THOSE WORLDS
THAN IN THE NORMAL ONES.
>> Reporter: ARE THERE PEOPLE
WHO THINK YOU'RE OUT OF YOUR
MIND?
>> YEAH, THERE'S PLENTY OF
PEOPLE WHO THINK THAT I'M OUT OF
MY MIND AND THAT'S PART OF WHAT
IS TROUBLING.
NOT THAT THEY THINK THAT I'M
WRONG, BUT THAT WE HAVEN'T
SETTLED THIS YET.
I MEAN, THESE WERE ALL QUESTIONS
THAT SHOULD HAVE BEEN HASHED OUT
IN THE 1920s AND '30s.
BUT AS A FIELD, PHYSICS DECIDED
NOT TO FACE UP TO THIS PUZZLE,
AND I THINK THAT IT'S BEEN
HOLDING US BACK AS PHYSICISTS.
I THINK THAT OUR UNDERSTANDING
OF COSMOLOGY AND GRAVITY ISN'T
NEARLY AS GOOD AS IT COULD HAVE
BEEN HAD WE WORKED HARDER AT
UNDERSTANDING QUANTUM MECHANICS.
>> Reporter: MANY WORLDS
SUGGESTS A NEW YOU IS CREATED IN
A NEW UNIVERSE THOUSANDS OF
TIMES PER SECOND.
SO THE YOU IN THIS UNIVERSE
WON'T BE SURPRISED TO LEARN THE
THEORY IS CONTROVERSIAL.
THE ONLINE MATH-AND-SCIENCE
JOURNAL "QUANTA MAGAZINE" HAS
CALLED IT "THE MOST POLARIZING
OF INTERPRETATIONS," SAYING
"SOME PHYSICISTS CONSIDER IT
ALMOST SELF-EVIDENTLY ABSURD."
DO YOU SAY THIS AT SOME RISK TO
YOURSELF?
YOU ARE A BEST SELLING AUTHOR,
AND YOU TEACH AT CALTECH, YOU'RE
IN A PRETTY FIRM POSITION AS
THESE THINGS GO.
>> I'M NOT IN A SUPER FIRM
POSITION, 'CAUSE I DON'T HAVE
TENURE AT CALTECH, SO, BUT I
DON'T CARE EITHER.
LIKE, I THINK IT'S MORE
IMPORTANT TO ME AT THIS POINT IN
MY LIFE TO TRY MY BEST TO GET IT
RIGHT.
AND IT'S NOT LIKE I'M GOING TO
BE BLACKBALLED OR OSTRACIZED BY
THE COMMUNITY, THERE'S PLENTY OF
OTHER PEOPLE WHO ARE
EVERETTIANS.
IT'S NOT SO MUCH THAT I'M A FAN
OF MANY WORLDS, IT'S THAT I CARE
ABOUT THE FOUNDATIONS OF QUANTUM
MECHANICS.
>> Reporter: I'M JUST WONDERING
IF DECADES FROM NOW WE'RE GOING
TO FIND YOU ON THE CORNER WITH A
BOTTLE, BABBLING ABOUT MANY
WORLDS.
>> THERE IS A WORLD IN WHICH
THAT HAPPENS, YES.
BUT YOU KNOW WHAT, I COULD
CHANGE MY MIND NEXT WEEK IF
SOMEONE SHOWED ME A BETTER
THEORY THAT DIDN'T HAVE SOME OF
THESE PROBLEMS AND STILL HAVE
ALL OF THE BENEFITS.
I THINK IT'S UNLIKELY.
I WOULD LOVE TO BE THE PERSON TO
COME UP WITH THAT THEORY MYSELF.
BUT I THINK THAT WE SHOULD HAVE
THE COURAGE TO FOLLOW OUR BEST
THEORIES AND ACCEPT WHAT THEY
PREDICT.
