STEPHEN HAWKING: WE ALL HAVE QUESTIONS.

BIG QUESTIONS.

MAN: AM I HERE FOR A REASON?

HAWKING: IT'S PART OF WHAT IT MEANS TO BE A HUMAN.

MAN: DO I CONTROL MY OWN DESTINY?

HAWKING: MY NAME IS STEPHEN HAWKING AND I BELIEVE THAT ANYONE CAN ANSWER BIG QUESTIONS FOR THEMSELVES.

THAT'S AWESOME.

HAWKING: SO, WITH THE HELP OF SOME ORDINARY PEOPLE... OH!

HAWKING: AND A TEAM OF EXPERTS... MAN: IN A FLASH CAME TO HIM THE NOTION THAT THERE MIGHT BE A SINGLE WALL.

HAWKING: WE ARE GOING ON THE ULTIMATE VOYAGE.

IT'S A COMPLETE HEAD TRIP.

HAWKING: A QUEST TO ANSWER THE GREATEST MYSTERIES OF THE UNIVERSE.

I'M NOT READY TO MAKE THAT LEAP.

IT'S SO MESSED UP.

HAWKING: USING THE POWER OF THE HUMAN MIND.

IT'S A VERY EXCITING MOMENT.

WOMAN: YES.

[LAUGHTER] HAWKING: BECAUSE ANYONE CAN THINK LIKE A GENIUS.

ANNOUNCER: "GENIUS BY STEPHEN HAWKING" WAS MADE POSSIBLE IN PART BY CONTRIBUTIONS TO YOUR PBS STATION FROM VIEWERS LIKE YOU.

THANK YOU.

VOICES AND NARRATOR: WHY ARE WE HERE?

HAWKING: HAVE YOU EVER WONDERED WHY WE ARE HERE?

I THINK MOST PEOPLE HAVE.

IF WE COULD ANSWER IT, MAYBE WE COULD ALL GET ALONG WITH EACH OTHER A LITTLE BETTER, WHICH WOULD BE GOOD.

SOME BELIEVE IN A HIGHER BEING WHO CREATED US FOR A PURPOSE.

OTHERS SAY THAT LIFE IS JUST A RANDOM CHAIN OF EVENTS WITH NO REAL MEANING.

BUT I BELIEVE THERE IS ANOTHER WAY TO ANSWER THE QUESTION.

IF WE LOOK AT THE FACTS, WE CAN WORK IT OUT FOR OURSELVES.

SO, I'VE ASKED 3 ORDINARY PEOPLE TO COME ON A JOURNEY.

A SERIES OF PUZZLES AND CHALLENGES AWAITS THEM.

THEY'LL BE GIVEN EQUIPMENT AND INSTRUCTIONS TO HELP.

CAN THEY SOLVE THE MYSTERIES AND TRY TO ANSWER THIS FASCINATING QUESTION?

WHY AM I HERE?

I REALLY CAN'T TELL YOU.

AM I AN ACCIDENT?

ARE WE ALL AN ACCIDENT?

AH, I DON'T THINK WE ARE.

IS THERE A REASON WE'RE HERE?

THAT WOULD ALMOST PRESUPPOSE SOMEBODY PUTTING US HERE.

I AM HERE, BUT THAT'S ALL I KNOW.

[LAUGHS] HAWKING: TO START THIS JOURNEY, I WANT MY VOLUNTEERS TO MAKE A BASIC REALIZATION.

SO, I HAVE BROUGHT THEM TO THIS ANCIENT ENGLISH CASTLE.

WHEN IT WAS BUILT NEARLY 600 YEARS AGO, THE WORD "SCIENCE" WAS ALMOST UNKNOWN.

PEOPLE THOUGHT THE UNIVERSE WAS MAGICALLY CONTROLLED BY ALL-POWERFUL BEINGS.

BUT MAGIC IS NOT ALWAYS THE BEST WAY TO EXPLAIN THINGS, WHICH IS WHAT I WANT THEM TO GRASP AT THIS SPECIAL DINNER.

KELLY: WOW.

ARJUN: IT'S SO WEIRD.

ERIC: PRETTY SPOOKY.

ARJUN: ROMANTIC AND HAUNTING AT THE SAME TIME.

KELLY: WHAT?

ERIC: SPINNING PLATES.

KELLY: OH, MY GOODNESS.

[LAUGHS] IT WAS SPOOKY.

IT WAS GREAT.

SO COOL.

[LAUGHS] IT'S MAGICAL.

HAWKING: PERHAPS THE ROOM IS FULL OF POLTERGEISTS.

HOW ARE THEY LEVITATING?

NO IDEA.

ERIC: SLIGHTLY SCARY.

ARJUN: IF YOU HAD DONE THIS SOME HUNDREDS OF YEARS AGO, YOU WOULD HAVE BEEN HUNG.

AND, YOU KNOW, THE FIRST THING THAT CROSSED MY MIND IS, "WHERE ARE THE STRINGS?"

[BLOWING] WHAT IS THE PURPOSE OF THAT BLOWING?

KELLY: IT COULD BE MAGIC.

ARJUN: COULD BE MAGIC.

MAYBE IT IS.

I'M--I'M NOT A BELIEVER.

[LAUGHTER] HAWKING: OF COURSE, I DON'T BELIEVE IN MAGIC EITHER.

BUT I DO BELIEVE IN HUMAN CURIOSITY.

ARJUN: MINE'S NOT SPINNING, YOURS ARE.

YEAH.

ERIC: WONDER WHY THAT IS.

HAWKING: OUR DESIRE TO UNDERSTAND HAS ALLOWED US TO ACHIEVE GREAT THINGS AND FINDING OUT HOW THINGS WORK IS FUN.

HA HA!

ARJUN: IN MY MIND, LOOKING AT THE PLATES FLOATING, IT WAS ABOUT, "HOW ARE THEY FLOATING?"

AND MORE IMPORTANTLY, "WHY ARE THEY FLOATING?"

BON APPETIT.

ERIC AND ARJUN: THANK YOU.

KELLY: CHEERS, GUYS.

ARJUN AND ERIC: CHEERS.

KELLY: I WANTED TO SEE IF THERE WAS REALLY ANYTHING UNDERNEATH IT THAT MIGHT HAVE BEEN HIDDEN, THAT COULD POSSIBLY BE SPINNING IT, BUT THERE DIDN'T SEEM TO BE.

AND SO THAT'S WHEN I FIGURED IT HAD TO BE SOME KIND OF, YOU KNOW, TECHNOLOGY.

[LAUGHS] SHE'S TAKEN IT ALL APART.

[LAUGHS] GUYS.

ERIC: NICE.

ARJUN: GONNA KICK YOU OUT.

IT'S CLEARLY A MAGNET.

MAGNETS.

IS THERE SOMEBODY UNDER THERE?

ARJUN: NO, THERE'S NOBODY UNDER THERE.

ERIC: ELECTROMAGNET.

KELLY: IT'S A HEXAGON.

HAWKING: THEY FOUND OUT THE SECRET OF THE MAGICALLY FLOATING PLATES: MAGNETS.

THE FORCE THAT THE TWO MAGNETS EXERT AGAINST EACH OTHER CAUSES THE PLATES TO HOVER IN THE AIR ABOVE THE TABLE.

BUT WHAT DO LEVITATING PLATES HAVE TO DO WITH OUR CENTRAL QUESTION-- WHY ARE WE HERE?

ARJUN: ONCE THE PLATES HAVE FALLEN, THE IDEA OF MAGIC SOON KIND OF DISAPPEARS.

IT COMES BACK TO IT'S JUST A TRICK.

SO, ONCE YOU MIGHT HAVE BEEN HUNG, BUT NOW IT'S JUST MAGNETS.

THAT'S PRETTY COOL.

ERIC: IT JUST SHOWS THE PROGRESSION OF HUMANITY FROM NOT UNDERSTANDING TO COMPLETELY UNDERSTANDING HOW TO DO SOMETHING LIKE THAT AND NOT HAVING IT BE MAGICAL ANY MORE.

IT WAS ABOUT THE JOURNEY FROM THE MAGICAL TO THE PRACTICAL WITH SCIENCE.

HAWKING: NOW THEY ARE STARTING TO UNLOCK THE MYSTERY.

THE UNIVERSE IS NOT CONTROLLED BY MAGIC BUT BY A SET OF RULES THAT WE CALL THE LAWS OF NATURE.

TO FIND OUT HOW WE DISCOVERED THESE LAWS, WE'RE GOING TO MEET ONE OF MY HEROES.

HE LIVED IN A LITTLE ENGLISH VILLAGE OVER 300 YEARS AGO.

MAN: WHEN IT COMES TO HUMAN KNOWLEDGE OF NATURE, THE PERIOD BETWEEN ROUGHLY 1500 AND 1700 GETS REMEMBERED AS THE SCIENTIFIC REVOLUTION BECAUSE IT BRINGS IN A NUMBER OF FUNDAMENTAL CHANGES IN OUTLOOK THAT REMAIN INDISPENSABLE TO WHAT WE CALL SCIENCE.

FOR MANY PEOPLE, THE OUTSTANDING FIGURE OF THE SCIENTIFIC REVOLUTION, THE CULMINATING FIGURE IS ISAAC NEWTON.

AND FOR GETTING A GRIP ON JUST WHAT IT IS NEWTON ACHIEVED, WE COULD DO NO BETTER THAN TO BE STANDING RIGHT HERE IN FRONT OF THE VERY APPLE TREE FROM WHICH FELL THE APPLE THAT GAVE NEWTON THE IDEA OF THE LAW OF UNIVERSAL GRAVITATION, OR SO THE STORY GOES.

IT'S 1666.

HE WAS SITTING UNDER THE APPLE TREE AND HE WATCHED AN APPLE FALL TO THE GROUND.

AND IN A FLASH CAME TO HIM THE NOTION THAT THERE MIGHT BE A SINGLE LAW, WHICH GOVERNS NOT JUST THE PULL OF THE EARTH ON AN APPLE BUT THE PULL OF THE EARTH ON THE MOON.

A SINGLE LAW, A LAW OF ATTRACTION BETWEEN ALL OF THE PARTICLES ACROSS THE COSMOS.

THAT WAS THE LAW OF UNIVERSAL GRAVITATION.

HAWKING: BY THE AGE OF JUST 25, ISAAC NEWTON SINGLE-HANDEDLY CHANGED THE WAY WE SEE THE WORLD.

MAGIC WAS NO LONGER NEEDED TO EXPLAIN HOW THE UNIVERSE WORKED OR WHY WE MIGHT BE HERE.

INSTEAD, THE LAWS OF NATURE COULD BE EXPLAINED USING REASON... AND WRITTEN DOWN IN A BOOK.

RADICK: HERE WE HAVE ISAAC NEWTON'S MASTERWORK, HIS "PRINCIPIA MATHEMATICA," THE MATHEMATICAL PRINCIPLES OF NATURAL PHILOSOPHY, PUBLISHED IN 1687 IN LATIN.

THIS IS WHERE NEWTON SET DOWN HIS 3 LAWS OF MOTION AND THE LAW OF UNIVERSAL GRAVITATION AND SET THEM TO WORK TO ACCOUNT FOR THE SYSTEM OF THE HEAVENS: THE TIDES, COMETS, AND OTHER NATURAL PHENOMENA.

HAWKING: IN THIS EXTRAORDINARY BOOK, NEWTON EXPLAINED HOW THE UNIVERSE WORKS IN A WAY THAT NO ONE HAD BEEN ABLE TO BEFORE.

HIS WORK USHERED IN THE MODERN AGE OF REASON, UNDERPINNED BY SCIENCE.

RADICK: NEWTON BECOMES THE FIRST SCIENTIFIC CELEBRITY; HE IS REVERED AS A HERO OF THE ENLIGHTENMENT.

THIS BOOK BECOMES THE BACKGROUND AND THE PLATFORM ON WHICH NATURAL SCIENCE IN ALL ITS VARIETY GROWS UP IN THE 18TH CENTURY.

HAWKING: THANKS TO GENIUSES LIKE NEWTON, SCIENCE GRADUALLY BEGINS TO EXPLAIN THE WORLD.

AND EVEN, I THINK, WHY WE ARE HERE.

I'VE GOT THE MAGIC TOUCH THEN.

OH.

HAWKING: MY VOLUNTEERS HAVE TAKEN THEIR FIRST STEP TO MAKING THAT REALIZATION FOR THEMSELVES.

KELLY: BEING IN THIS AMAZING SETTING REALLY HELPED ME, I THINK, GET IN THE MINDSET OF PEOPLE, FOR EXAMPLE, OF THE MIDDLE AGES AND HOW THEY WOULD HAVE PERCEIVED SOMETHING AS BEING COMPLETELY MAGICAL.

THAT'S REALLY COOL.

[LAUGHS] KELLY: I TOTALLY THINK WE CAN USE THE LAWS OF SCIENCE TO UNDERSTAND THE UNIVERSE AND THEREFORE DEDUCE WHY WE MIGHT BE HERE.

HAWKING: WE HAVE SEEN THAT THE UNIVERSE IS GOVERNED BY LAWS, BUT HOW DOES THAT HELP US WORK OUT WHY WE ARE HERE?

NOW I WANT MY VOLUNTEERS TO UNDERSTAND HOW THE LAWS OF NATURE AFFECT OUR INDIVIDUAL LIVES.

AND TO HELP THEM, I HAVE GIVEN THEM A NEW CHALLENGE.

OH, A BAR.

NICE.

[LAUGHTER] WHO'S THIRSTY?

KELLY: FIRST THING WE SEE IS A BARTENDER STANDING IN THE FAR CORNER, AND HE'S SHAKING A MIXED DRINK.

AND THEN WE NOTICE THAT THERE'S A TABLE SET OUT AND THERE'S ONE MARTINI GLASS ON THE TABLE.

ERIC: WHAT'S THAT NOTE SAY?

OH.

ARJUN: FINISH OFF THE MARTINI WITH AN OLIVE WITHOUT TOUCHING THE GLASS.

WHAT DO YOU THINK THAT MEANS?

I IMAGINE THAT WE HAVE TO KNOCK THAT OLIVE INTO THE MARTINI TO FINISH IT OFF.

ARJUN: WITHOUT TOUCHING IT.

OK. ERIC: MY GUESS IS WE'RE USING THAT.

HAWKING: USING A PENDULUM SUSPENDED BY A CHAIN, THEY MUST MAKE THE PERFECT COCKTAIL BY KNOCKING THE OLIVE INTO THE GLASS.

[GLASS SHATTERS] [LAUGHTER] ARJUN: YEAH, THAT WAS INEVITABLE.

COULD WE GET ANOTHER DRINK?

THANK YOU.

I HOPE THESE AREN'T EXPENSIVE MARTINIS.

ARJUN: WHO WANTS A PERFECT MARTINI?

KELLY: I DO.

[GLASS SHATTERS] OH!

THAT WAS NOT THE PERFECT MARTINI.

SMASHING GLASSES WAS A LOT OF FUN.

[GLASS SHATTERS] WE BROKE QUITE A FEW GLASSES.

OH.

MAN: OH.

UM, AND I WAS PRETTY GOOD AT BREAKING THE GLASSES.

KELLY: I'LL TRY NOT TO DO IT SO STRONG.

THAT WAS SO CLOSE.

ARJUN: I THINK RIGHT DISTANCE, JUST NOT THE RIGHT ANGLE.

IT'S A MIXED BAG OF FEELINGS, 'CAUSE IT'S, "OH, MY GOD, I'M SO CLOSE, IT'S ALMOST THERE."

BUT THERE'S A FEAR OF, "I'VE GOT TO GIVE YOU A LITTLE BIT MORE BUT IF I DO, THAT MAY TIP ME OVER THE EDGE."

UM, IT'S A VERY EXCITING MOMENT.

KELLY: IT'S CRAZY.

EVEN MINOR DIFFERENCES MAKE A BIG DIFFERENCE.

[GLASS SHATTERS] OH!

OOH.

[GLASS SHATTERS] THIS IS CLEARLY NOT WORKING.

HAWKING: TO GET IT RIGHT, THEY NEED TO THINK LIKE SCIENTISTS.

SO, WE'VE GOTTA GET THE OLIVE IN THE GLASS WITHOUT TOUCHING THE GLASS.

WITH THE PERFECT AMOUNT OF PENDULUM SWING TO JUST TOUCH THE OLIVE TO FALL IN THE GLASS.

ARJUN: OK, AND WHERE DID YOU SWING IT FROM LAST TIME?

ERIC: I SWUNG IT FROM SOMEWHERE UP HERE.

ARJUN: SO, THESE HOLES HERE ARE REPRESENTING?

ERIC: NUMBER OF DEGREES, RIGHT?

SO, I BROUGHT IT UP TO HERE.

SO, IF WE MARK IT, THE NEXT TIME.

OK, SO-- SO, LET'S SAY WE GO THERE, RIGHT?

OH, YES.

YES.

[LAUGHS] SUCCESS.

[LAUGHS] HAWKING: IT'S A PERFECT SWING.

NICELY DONE.

ALL RIGHT.

HAWKING: BUT ONCE IS NOT ENOUGH.

ALL RIGHT.

LET ME TRY.

HAWKING: TO PROVE THEY CAN MAKE THE PERFECT COCKTAIL EVERY TIME... HOW'S THAT LOOK?

HAWKING: THEY HAVE TO DO IT 3 TIMES IN A ROW.

ARJUN: DANGEROUS.

ERIC: WHOA.

[GLASS SHATTERS] [LAUGHTER] WE KNOW THAT WE CAN HIT THE OLIVE SOME OF THE TIME, BUT WE ALSO KNOW MANY TIMES WE WILL PUSH IT AND IT WILL WRECK THE GLASS.

IT'S SUCH A DELICATE OPERATION.

ERIC: WHAT IF WE CAME UP WITH A STICK OR SOMETHING, TO PUT THROUGH THE HOLES?

OR SOMETHING TO HOLD THE BALL.

'CAUSE WE'VE GOT THE RIGHT SPOT, I GUESS, BUT THE RELEASE IS DIFFERENT.

YOU'RE EITHER PUSHING IT OR YOU DON'T LET IT OUT.

KELLY: 'CAUSE YOU'RE STILL EYEBALLING IT, REALLY.

ERIC: OK. MAYBE THERE'S SOMETHING ABOUT HERE.

THERE'S A BATTERY.

OH, EXCELLENT.

LOOK AT THIS.

A MAGNET.

ERIC: WHICH--WHICH HOLE WERE WE IN?

ARJUN: UH, WE WERE IN 14, I BELIEVE.

OK, SO, IF WE INSERT THIS.

KELLY: IT LOOKS GOOD.

SHALL WE TRY IT?

KELLY: YEAH.

OK. OK. NICE.

ERIC: PERFECT.

ARJUN: BETTER.

ERIC: SO, IT'S ABOUT THE ALIGNMENT.

KELLY: YEAH.

BY USING THE MAGNET TO SET THE STARTING CONDITIONS EXACTLY THE SAME EVERY TIME, AND THE RELEASE CONDITIONS EXACTLY THE SAME EVERY TIME, THE RESULT IS PREDICTABLE.

RIGHT.

ERIC: MAKE SURE THE CHAIN'S ALIGNED, THE GLASS IS ALIGNED.

KELLY: OOPS.

OLIVE ISN'T ALIGNED.

LET'S MAKE SURE THAT THAT'S-- OK. ALL IS ALIGNED.

ERIC: YOU GUYS READY?

ARJUN: YEAH.

NICE.

ERIC: ALL RIGHT.

LET'S TRY AGAIN.

ARJUN: WHO CAN GET IT 3 TIMES?

ERIC: NO, DON'T MOVE ANYTHING.

ARJUN: WE'VE DEFINITELY GOT IT, YEAH.

HOLD ON FOR A SEC.

ERIC: THAT LOOKS PRETTY GOOD.

NOW I'M HAPPY.

YOU THINK IT'S GONNA WORK?

SHE'S HAPPY.

ALL RIGHT, LET'S GO.

OK. NICE.

AWESOME.

RIGHT.

HAWKING: DELICIOUS, I'M SURE.

SO, HOW DOES THIS COCKTAIL RELATE TO OUR CENTRAL QUESTION-- WHY ARE WE HERE?

KELLY: SO, WHAT DO YOU GUYS THINK THIS MEANS?

ARJUN: DOING THE EXACT SAME THING EVERY SINGLE TIME GIVES YOU THE EXACT SAME RESULT.

KELLY: I GUESS ONE COULD SAY, IF THE LAWS OF PHYSICS APPLY EVERY TIME, THEN WHATEVER HAPPENS IS WHATEVER WAS SUPPOSED TO HAPPEN.

IT'S ALWAYS THE SAME RESULT.

YEAH.

YEAH.

HAWKING: THAT'S EXACTLY RIGHT.

WHAT HAPPENS TO THE COCKTAIL IS PREDETERMINED BY WHERE AND HOW THE PENDULUM IS RELEASED.

THE LAWS OF NATURE ARE ALWAYS IN CONTROL AND THEY DON'T VARY.

SO, THE START GUARANTEES THE OUTCOME EVERY TIME.

[GLASS SHATTERS] [LAUGHTER] ERIC: THE PERFECT COCKTAIL IS DEFINED BY A SET OF ALREADY EXISTING LAWS.

IF THE LAWS THROUGHOUT THE UNIVERSE ARE KNOWN AND WHOMEVER IS DOING THE EXPERIMENT KNOWS WHAT TO EXPECT, THEY WILL ALWAYS KNOW WHAT THE FUTURE HOLDS.

AND THAT IS MIND BLOWING.

HAWKING: WHEN IT COMES TO WORKING OUT WHY WE ARE HERE, THIS IDEA HAS HUGE IMPLICATIONS FOR MANKIND.

IF THE WHOLE UNIVERSE IS RIGIDLY DETERMINED BY THE LAWS OF NATURE, ITS FUTURE IS ALREADY DICTATED BY WHAT HAPPENED BEFORE.

SO, PERHAPS OUR DESTINY AS A SPECIES AND AS INDIVIDUALS IS PREDETERMINED, TOO.

THIS DISTURBING IDEAL WAS FIRST SET OUT IN 1814 BY A FRENCH GENIUS NAMED LAPLACE.

MAN: THE MARQUIS, PIERRE SIMON DE LAPLACE, WAS A FRENCH PHILOSOPHER, MATHEMATICIAN, AND PHYSICIST.

IF YOU KNEW, LAPLACE SAID, IF YOU KNEW EVERYTHING ABOUT THE UNIVERSE RIGHT NOW.

WHICH MEANS IF YOU KNEW WHERE EVERYTHING WAS, HOW IT WAS MOVING, ALL THE LAWS OF PHYSICS, AND YOU WERE INFINITELY SMART-- TODAY, WE WOULD SAY IF YOU HAD A INFINITELY GOOD COMPUTER-- LAPLACE SAYS, THEN YOU KNOW THE ENTIRE FUTURE OF THE UNIVERSE AND YOU KNOW THE ENTIRE PAST OF THE UNIVERSE.

THE WHOLE HISTORY OF REALITY IS CONTAINED IMPLICITLY IN EVERY MOMENT.

HAWKING: LAPLACE BELIEVED THAT THE UNIVERSE WORKED LIKE CLOCKWORK.

IF YOU KNOW THE POSITION OF EVERY COG IN THE MACHINE, THEN YOU CAN TELL ITS POSITION WITH CERTAINTY AT ANY POINT IN THE PAST OR FUTURE.

THIS IDEA CAME TO BE KNOWN AS DETERMINISM.

IT DESCRIBED A UNIVERSE THAT WOULD CONTINUE PREDICTABLY WITHOUT DIVINE INTERVENTION.

CARROLL: LAPLACE WROTE A VERY FAMOUS BOOK ON CELESTIAL MECHANICS-- THE MOTIONS OF THE PLANETS AND THE STARS THAT WAS PRESENTED TO THE EMPEROR NAPOLEON.

AND TO TEASE LAPLACE, NAPOLEON SAID TO HIM, "I SEE NO MENTION OF GOD IN YOUR WORK," AND VERY HUFFILY LAPLACE REPLIED, "I HAD NO NEED OF THAT HYPOTHESIS," AND HE KEPT MAKING THAT POINT THROUGHOUT HIS LIFE.

HE WAS VERY CLEAR THAT THE UNIVERSE MOVED BY ITSELF, IT WAS NOT PUSHED ALONG BY A HIGHER POWER.

HAWKING: I DON'T BELIEVE LAPLACE WAS CLAIMING THAT GOD DIDN'T EXIST, JUST THAT GOD DOESN'T INTERVENE TO BREAK THE LAWS OF NATURE.

AFTER ALL, A SCIENTIFIC LAW ISN'T A LAW AT ALL IF ITS OUTCOME CAN BE ALTERED BY A HIGHER POWER.

I THINK THAT IF YOU'RE LISTING 10 PEOPLE IN HUMAN HISTORY WHO REALLY CHANGED THE WAY WE THINK ABOUT OURSELVES AND THE UNIVERSE AND HOW WE FIT INTO IT--I WOULD ARGUE THAT LAPLACE DESERVES A-A SPOT ON THAT ALL-STAR TEAM.

HAWKING: IF LAPLACE IS RIGHT, THEN EVERY MOMENT IN YOUR LIFE... WHO YOU FALL IN LOVE WITH, YOUR CAREER, WHEN YOU DIE... IS ALREADY PRE-DETERMINED BY THE STRICT LAWS THAT GOVERN THE UNIVERSE.

THAT MEANS THAT ALTHOUGH WE MAY THINK WE CHOOSE OUR DESTINY, FREE WILL IS AN ILLUSION, AND WE ARE JUST VERY COMPLICATED COGS IN THE MACHINE.

KELLY: I COULD SEE THE UNIVERSE PLAYING OUT LIKE CLOCKWORK.

I-I COULD ACTUALLY SEE THAT.

ERIC: I WANT TO BELIEVE THAT I STILL HAVE A CHOICE BUT IF PHYSICS IS TAKING US TO A PLACE WHERE WE HAVE ALL THE STEPS LAID OUT AND WE ALWAYS CAN PREDICT WHAT THE FUTURE IS, THAT'S GOING TO BE A REALLY HARD PILL TO SWALLOW.

HAWKING: SO, IS YOUR LIFE DETERMINED JUST LIKE THE COCKTAIL?

OR ARE YOU FREE TO MAKE YOUR OWN CHOICES?

IT'S A QUESTION THAT SCIENTISTS OF ALL DISCIPLINES HAVE WRESTLED WITH FOR CENTURIES.

BUT MODERN NEUROSCIENCE HAS REVEALED SURPRISING RESULTS.

MAN: IN THE LATE 1970S, PEOPLE FOR THE FIRST TIME WERE ABLE TO MEASURE SOME BRAIN ACTIVITY WHILE PEOPLE WERE ENGAGED IN CONSCIOUS MENTAL ACTIVITY.

LATER, PEOPLE STARTED DEVELOPING BRAIN-SCANNING TECHNIQUES WITH WHICH IT'S POSSIBLE TO LOOK AT THE BRAIN ACTIVITY IN MUCH MORE DETAIL.

AND THE PSYCHOLOGIST BENJAMIN LIBET PERFORMED A VERY FAMOUS EXPERIMENT.

HE GOT PEOPLE TO MAKE VERY SIMPLE DECISIONS ABOUT MOVING THEIR FINGERS.

AT THE SAME TIME HE RECORDED THEIR BRAIN ACTIVITY.

WHAT THESE EXPERIMENTS SHOW IS THAT AT THE POINT IN TIME WHEN WE THINK WE'RE DECIDING; TO SOME DEGREE AT LEAST THE DECISION HAS ALREADY BEEN MADE BY UNCONSCIOUS BRAIN ACTIVITY.

HAWKING: I WANT MY VOLUNTEERS TO UNDERSTAND WHAT THIS EXPERIMENT REALLY MEANS AND WHAT IT IMPLIES FOR THE IDEA OF FREE WILL.

SO, WE ARE GOING TO RUN A VERSION OF IT AT THE CASTLE, USING SOME HIGH-TECH EQUIPMENT.

ARJUN: HELLO.

WE'RE GONNA WATCH A MOVIE.

NO.

I'M GONNA BE TESTED.

WHAT IS HAPPENING?

KELLY: WHAT IS THAT?

THERE IT GOES.

IT'S READING.

THAT'S ME.

UP ON A CASTLE.

KELLY: THAT'S CRAZY.

ERIC: I KNOW.

I HAVE THIS--THIS CONTRAPTION ON MY HEAD AND IT'S READING ELECTRICAL PULSES.

IT'S READING ACTIVITY IN MY BRAIN.

KELLY: YOU LOOK LIKE YOU'RE THINKING HARD.

I'M--I'M REALLY FEELING IT.

WHAT IS IT TELLING YOU?

YEAH, CAN YOU MAKE IT CHANGE?

I DON'T KNOW.

LET'S TRY.

SHOULD I GET ANGRY?

GRR.

[LAUGHS] HAWKING: THIS CONTRAPTION IS CALLED AN EEG.

IT'S THE SAME KIND OF DEVICE THAT LIBET USED IN HIS EXPERIMENTS.

HAYNES: WHAT YOU CAN SEE HERE IS ELECTRICAL ACTIVITY OF THE 100 BILLION NERVE CELLS IN YOUR BRAIN.

OK. HAYNES: WE TEND TO THINK THAT OUR MIND IS PRIVATE, THAT NOBODY CAN SEE OUR THOUGHTS FROM THE OUTSIDE.

EVERY THOUGHT YOU HAVE HAS A UNIQUE SIGNATURE IN THIS BRAIN ACTIVITY.

EVERY DECISION YOU MAKE LEAVES A TRACE IN YOUR BRAIN ACTIVITY.

THIS BRAIN ACTIVITY IS YOU.

OOH, FANCY.

LOOK AT THAT.

HAYNES: WHAT WE'RE GOING TO DO IS WE'RE GOING TO MEASURE SOME SPONTANEOUS DECISIONS THAT YOU'RE GOING TO MAKE.

OK.

SO, I'D LIKE YOU, TO SOME POINT, WHEN YOU FEEL THE URGE TO DO SO, TO SPONTANEOUSLY PRESS THIS BUTTON.

OK. WHAT I'D LIKE YOU TO ALSO DO IS TELL ME WHERE THE DIAL IS ON THE SCREEN WHEN YOU MAKE UP YOUR MIND.

OK. ERIC: THAT'S AWESOME.

ARJUN: NICE.

[LAUGHTER] INTERESTINGLY ENOUGH, TURNS OUT EVERY TIME WE PRESS THE BUTTON, FIREWORKS GO OFF.

[LAUGHS] AND WE ALL ABOUT HAVE A MINI HEART ATTACK.

[LAUGHS] [LAUGHS] ERIC: IT WAS AROUND THE 50 MARK.

MY HEART'S RACING A BIT.

[LAUGHTER] IT DOESN'T GET OLD.

NO, IT DOESN'T.

THAT'S AWESOME.

HAYNES: WHERE WAS THE DIAL?

ERIC: UH, 50ISH.

KELLY: WHOA, LOOK AT IT.

ERIC: YEAH, THAT'S COOL.

I DON'T HAVE ANY FURTHER URGE TO PRESS IT.

OK. KELLY: 10.

[ARJUN LAUGHS] THAT'S SO COOL.

KELLY: I THINK IT WAS AROUND 20.

[LAUGHS] HAWKING: SO, CAN THEY WORK OUT WHAT THIS EXPERIMENT HAS TO DO WITH DETERMINISM AND FREE WILL?

IT'S HARD TO IMAGINE THAT IT'S NOT FREE WILL, 'CAUSE WHO'S TELLING ME OR FORCING ME TO PRESS IT AT A CERTAIN TIME?

SO, I THINK I'LL PUSH IT ONE MORE TIME.

HERE I GO.

TRY NOT TO LOOK AT THE CLOCK SO MUCH.

ERIC: DON'T LOOK AT THE CLOCK.

KELLY: IT'S RIGHT AROUND-- BETWEEN 20 AND 25.

HAWKING: WHEN THE DATA IS COLLECTED, THIS EXPERIMENT CAN REVEAL HOW A CONSCIOUS DECISION SUCH AS DECIDING TO PRESS A BUTTON...

IT WAS AT 20.

HAWKING: IS PRECEDED BY UNCONSCIOUS BRAIN ACTIVITY.

AND AVERAGE RESULTS FROM MANY OF THESE EXPERIMENTS POINT TO A REMARKABLE CONCLUSION.

AS MY VOLUNTEERS TRY TO EXERCISE FREE WILL, IT APPEARS THAT THEIR BRAINS ARE MAKING DECISIONS BEFORE THEY ARE EVEN AWARE OF IT.

WHAT WE'RE GONNA SHOW YOU IS THE AVERAGE BRAIN ACTIVITY BEFORE THE TIME WHEN YOU ACTUALLY PRESS THE BUTTON.

SO, WE CAN LOOK AT IT HERE.

IT'S THE ELECTRICAL ACTIVITY OF YOUR BRAIN AROUND THE TIME OF THE MOVEMENT.

HAWKING: THE GRAPH COVERS A PERIOD OF 2.5 SECONDS.

JUST AFTER THE PEAK IS THE PRECISE MOMENT WHEN THE BUTTON IS PRESSED.

HAYNES: THE BIG QUESTION IS, WHEN DID YOU CONSCIOUSLY DECIDE TO MOVE?

ARJUN: ONE SECOND BEFORE WE MOVED.

HAYNES: YOU THINK YOU MADE UP YOUR MIND HERE?

YEAH.

HAYNES: SO, IN FACT, WHAT HAPPENS IS THAT YOU DECIDE AROUND HERE AND THAT YOUR BRAIN HAS STARTED PREPARING YOUR DECISION LONG BEFORE YOUR CONSCIOUS MIND KICKS IN.

HAWKING: THIS DATA SHOWS US THAT THE SUBCONSCIOUS PART OF YOUR BRAIN BEGINS TO MAKE A DECISION AS MUCH AS HALF A SECOND BEFORE YOU DO IT CONSCIOUSLY.

AND YOUR FINGER ACTUALLY MOVES ANOTHER HALF-SECOND AFTER THAT.

THIS SUGGESTS YOUR SUBCONSCIOUS MIND MADE THE DECISION TO PRESS THE BUTTON, NOT YOUR CONSCIOUS MIND.

IF THIS IS RIGHT, THEN YOU HAVE NO FREE WILL.

ARJUN: I DEFINITELY HAVE FREE WILL.

IF I WAS JUST A BRAIN, I WOULD BE JUST THE BRAIN.

THERE WOULDN'T BE ALL THESE OTHER THINGS THAT I FEEL AND THINK.

IF THERE IS JUST THE BRAIN FEELING IT, WHY DOES IT DETERMINE SO MANY OTHER THINGS IN OUR LIVES?

HAWKING: MY OPINION IS THAT THE BRAIN IS MADE OF MATTER WHICH, LIKE THE REST OF THE UNIVERSE, MUST FOLLOW THE LAWS OF NATURE.

THERE IS NO SPECIAL STUFF IN OUR HEADS, NO GHOST IN THE MACHINE.

IF LIFE IS COMPLETELY PREDETERMINED, BASED ON SCIENCE, THEN I CAN'T-- I'M NOT SURE WHAT THE REASON FOR EVERYTHING WE'RE DOING IS.

IT'S JUST--THAT'S SO MESSED UP.

IT'S REALLY MESSED UP.

YEAH.

HAWKING: MY VOLUNTEERS HAVE LEARNED THAT THE UNIVERSE IS, AS FAR AS WE CAN TELL, GOVERNED BY LAWS.

AND IT SEEMS THAT IF EVERYTHING IS DETERMINED, LIKE THE SWING OF A PENDULUM, THEN THE FUTURE IS SET IN STONE.

THAT MEANS WE HUMANS, AS PART OF THE UNIVERSE, ARE TRAVELING ON A FIXED PATH.

AND WHAT WE THINK OF AS FREE WILL IS INDEED AN ILLUSION.

KELLY: I AM NOT YET CONCEDING THAT I AM A FIXED MACHINE IN A FIXED UNIVERSE.

I UNDERSTAND THAT WE CAN'T BE IN CONTROL OF EVERYTHING.

BUT I DON'T THINK THAT YOU CAN SAY THAT THERE'S NO FREE WILL.

I'M NOT READY TO MAKE THAT LEAP.

HAWKING: FORTUNATELY, THIS IS NOT THE END OF KELLY'S JOURNEY.

TO LEARN MORE ABOUT WHY WE ARE HERE, WE NEED TO SEE IF THE LAWS THAT DETERMINE THE COSMOS ON A LARGE SCALE HOLD UP WHEN WE EXAMINE THE UNIVERSE AT THE SMALLEST OF SCALES.

BECAUSE AS THEY SAY, THE DEVIL IS IN THE DETAIL.

HOW DO THE LAWS OF NATURE APPLY TO THE TINIEST STRUCTURES-- TO ATOMS AND BEYOND?

MAN: THE IDEA OF ATOMS ACTUALLY GOES BACK TO THE ANCIENT GREEKS...

DIRECT SEEING OF THE COMPONENTS THAT MAKE UP ATOMS DON'T BEGIN TO COME UNTIL THE LATE 19TH CENTURY, UH, WITH, FOR EXAMPLE, THE DISCOVERY OF THE ELECTRON.

HAWKING: IT WAS A BRITISH SCIENTIST NAMED JOHN JOSEPH THOMPSON WHO DISCOVERED ELECTRONS IN 1897.

HE DISCOVERED THAT THEY ARE TINY CHARGED PARTICLES, WHICH SPIN AROUND THE OUTSIDE OF THE ATOM.

THEY ORBIT A CENTRAL CORE CALLED A NUCLEUS.

AND THIS NUCLEUS IS MADE OF TWO OTHER SUBATOMIC PARTICLES...

KNOWN AS PROTONS AND NEUTRONS.

THEY IN TURN ARE BUILT OF EVEN SMALLER PARTICLES CALLED QUARKS.

WELCOME TO THE WORLD OF QUANTUM PHYSICS.

JOHNSON: ALL OF A SUDDEN, IT TURNED OUT THERE'S THIS WHOLE OTHER WORLD, THIS QUANTUM WORLD UNDERLYING EVERYTHING THAT REQUIRED A WHOLE NEW SET OF RULES TO BE DISCOVERED.

NEWTON, CENTURIES EARLIER, HAD EXPECTED THAT THOSE ATOMIC CONSTITUENTS WOULD ALSO OBEY NEWTON'S LAWS OF MOTION.

AND THAT TURNS OUT TO BE WRONG, VERY WRONG.

SO, IT WASN'T JUST DISCOVERING NEW PARTICLES THAT MAKE THINGS UP, BUT THEY NEEDED NEW RULES.

ENTIRELY NEW PHYSICS.

AND THAT PHYSICS WAS LIKE NOTHING WE'D EVER SEEN.

HAWKING: THIS IS WHERE THINGS START TO GET STRANGE AND THE IDEA THAT EVERYTHING IS DETERMINED STARTS TO FACE PROBLEMS.

BECAUSE SCIENTISTS HAVE DISCOVERED AT VERY SMALL SCALES THE UNIVERSE DOES NOT PLAY BY THE SAME RULES.

FOR THEIR NEXT CHALLENGE, I WANT MY VOLUNTEERS TO WORK OUT WHY.

ALL RIGHT.

WE'VE GOT A GRID HERE WITH NUMBERS ON ONE SIDE AND LETTERS ON THE OTHER.

ARJUN: AND RED BALLOONS.

KELLY: I'M THINKING WE MUST BE DOWN AT THE SUBATOMIC LEVEL.

HAWKING: IMAGINE WE WERE IN THE SUBATOMIC WORLD AND AN ELECTRON WAS THE SIZE OF A BALLOON.

WHAT IF WE TRY TO PRECISELY LOCATE THE ELECTRONS ON THE GRID TO FIND THEIR EXACT POSITION?

KELLY: HERE, I'LL COVER THESE.

ERIC: UH, SURE.

ARJUN: OK. HAWKING: AN ELECTRON IS SO TINY THAT IT CAN'T BE SEEN DIRECTLY, WHICH IS A BIT LIKE LOOKING FOR SOMETHING WHEN WEARING A BLINDFOLD.

I-I DON'T KNOW HOW WE'RE GONNA DO THIS WITH BLINDFOLDS ON.

KELLY: I HAVE NO IDEA.

HAWKING: LET'S SEE WHAT HAPPENS.

A9.

KELLY: OH!

THEY'RE GETTING AWAY FROM ME.

I'M PLAYING BASKETBALL WITH THEM.

KELLY: HA HA!

KELLY: WE START JUST RANDOMLY GROPING ABOUT, UM, TRYING TO FIND THEM.

ERIC: HOW MANY DID YOU GUYS FIND?

KELLY: I BUMPED INTO ONE.

ARJUN: GOD'S SAKE.

[KELLY LAUGHS] ARJUN: NOTHING WITH REGARDS TO THE ELECTRONS WERE CONSTANT.

SO, WE WERE MOVING AROUND, THE ELECTRONS WERE MOVING AROUND.

ERIC: HOW IS IT POSSIBLE FOR ME TO WALK THROUGH THIS WHOLE THING WITHOUT FINDING A BALLOON?

KELLY: OOH, GOT ONE.

BOPPED ME ON THE NOSE.

UH, THIS IS, UH, C14.

ARJUN: C14.

KELLY: AS SOON AS WE PUT THE BLINDFOLD BACK ON, IT'S MOVED AGAIN.

AND SOMEBODY ELSE WILL FIND THE SAME ONE BUT IN A DIFFERENT LOCATION.

I'M WALKING TOWARDS KELLY NOW.

I'M JUST WALKING AROUND IN CIRCLES.

[LAUGHS] HAWKING: THE LIGHTER AN OBJECT IS, THE HARDER IT IS TO PIN DOWN, SIMPLY BECAUSE IT'S SO EASY TO DISTURB.

ARJUN: OH.

I'VE JUST WALKED INTO ANOTHER.

THIS IS E-- OH, I'M SORRY.

E9.

E9.

KELLY: OH.

ERIC: I DON'T KNOW HOW MANY I HAVE FOUND NOW.

ARJUN: NO, I KEEP FINDING MORE.

KELLY: UH, E8.

ERIC: I'VE SENT ONE FLYING.

EVERYTHING WAS JUST COMPLETELY RANDOM AND THERE WAS NO WAY TO PREDICT WHERE IT WAS GONNA BE.

ERIC: ALL RIGHT.

THIS IS NOT GONNA WORK.

KELLY: YEAH, I-I TOTALLY AGREE.

THIS IS NOT GONNA WORK.

ARJUN: I'M JUST TAKING MY BLINDFOLD OFF.

OH, WOW.

DID I COMPLETELY MISS ALL THESE?

THERE IS REALLY NO WAY TO FIGURE THIS OUT.

IT'S COMPLETELY RANDOM AND THERE'S NO WAY TO PREDICT WHAT'S GOING ON.

HAWKING: I ADMIT IT.

THIS CHALLENGE IS NEXT TO IMPOSSIBLE, MUCH LIKE TRYING TO LOCATE SOMETHING AS TINY AND LIGHT AS AN ELECTRON.

WE CAN'T HELP BUT DISTURB IT.

SO ITS EXACT POSITION IS FUNDAMENTALLY UNKNOWABLE.

KELLY: WE'RE NEVER GONNA GET IT.

ARJUN: UNLESS WE DON'T TOUCH IT.

KELLY: YEAH, BUT WE CAN'T FIND IT IF WE DON'T TOUCH IT.

SO, IT'S A PARADOX.

MAN: HA HA!

HAWKING: BUT HERE'S THE REAL ISSUE.

IT ISN'T JUST A PROBLEM OF LOCATING SMALL THINGS BUT SOMETHING ELSE MUCH MORE PROFOUND.

ARE THE BUILDING BLOCKS OF MATTER HARD TO PIN DOWN BECAUSE THEY ARE NOT ACTUALLY IN A PERFECTLY DEFINED PLACE?

THE UNIVERSE IS A BIT FUSSY AT THE SMALL SCALE, LIKE ZOOMING TOO FAR INTO A PHOTOGRAPH.

THIS MIGHT SOUND CRAZY, BUT IT APPEARS TO BE TRUE.

ON THE VERY SMALLEST OF SCALES, MATTER BEHAVES IN A VERY STRANGE, EVER SO SLIGHTLY INDISTINCT WAY.

IN 1927, A GERMAN GENIUS NAMED WERNER HEISENBERG TOOK A BOLD STEP.

HE CAME UP WITH AN IDEA CALLED THE UNCERTAINTY PRINCIPLE, WHICH SUGGESTED THAT THE DIFFICULTY OF LOCATING SMALL THINGS POINTS TO A DEEPER REALITY.

THE BEHAVIOR OF SUBATOMIC PARTICLES IS INDEED A BIT UNCERTAIN AND ILL-DEFINED.

WHICH IMPLIES THE ENTIRE UNIVERSE HAS RANDOMNESS AT ITS CORE.

KELLY: SO, AT THE ELECTRON LEVEL, AT THE SUBATOMIC LEVEL, IF THINGS ARE TOTALLY RANDOM, TO MY MIND THAT WOULD MEAN THAT YOU CAN'T SAY THAT THINGS IN THE UNIVERSE WORK LIKE CLOCKWORK.

IT ISN'T PREDETERMINED, IT ISN'T PREDESTINED.

IT ISN'T THE UNIVERSE JUST PLAYING OUT AS IT MUST.

AND THAT MAKES ME FEEL REALLY LUCKY.

[LAUGHS] SO, I'M A CHEMICAL ACCIDENT.

I GOT HERE THROUGH DUMB LUCK.

HAWKING: KELLY MAY FEEL LUCKY, BUT IN THE 1920S, SCIENTISTS FELT DIFFERENTLY.

ONE OF HEISENBERG'S CONTEMPORARIES WAS ALBERT EINSTEIN.

HE HATED THE IDEA THAT RANDOMNESS COULD EXIST IN NATURE.

HE SAID, "GOD DOES NOT PLAY DICE WITH THE WORLD."

BUT TODAY, SCIENTISTS HAVE PROVED THAT, AS DIFFICULT AS IT IS TO COMPREHEND, THE UNCERTAINTY PRINCIPLE IS INDEED CORRECT.

SO, LAPLACE'S IDEA OF DETERMINISM, OF A SINGLE UNIVERSE OPERATING LIKE CLOCKWORK, CANNOT BE THE WHOLE PICTURE.

SUBATOMIC RANDOMNESS REVEALS THERE IS SOMETHING ELSE GOING ON, AND WE WILL NEED A NEW UNDERSTANDING TO FIND OUT HOW IT WORKS.

WE KNOW THAT QUANTUM PHYSICS IS IMPORTANT.

WE'RE STILL TRYING TO FIGURE OUT HOW TO COMBINE QUANTUM PHYSICS AND GRAVITY, IN ORDER TO UNDERSTAND HOW THE THINGS WE'RE MADE OF GOT HERE.

HAWKING: BUT WE ARE STARTING TO FIND SOME ANSWERS TO WHY WE ARE HERE.

WE HAVE FOUND OUT THAT DESPITE NEWTON'S LAWS, THE UNCERTAINTY PRINCIPLE SUGGESTS THAT THE UNIVERSE MIGHT ACTUALLY BE RANDOM... AND NOT DETERMINED AFTER ALL.

IN THE HISTORY OF SCIENCE, THIS IS ABOUT AS BIG A CHANGE AS CAN BE IMAGINED.

IN THEIR NEXT CHALLENGE, I WANT MY VOLUNTEERS TO WORK OUT HOW THE RANDOMNESS OF THE QUANTUM WORLD CAN AFFECT THE UNIVERSE ON OUR LARGE SCALE.

MAYBE STEPHEN JUST WANTS US NOW TO PAINT AND DECORATE THE CASTLE.

AFTER ALL THE DAMAGE WE'VE CAUSED.

BROKEN GLASSES... KELLY: A LITTLE DIY.

ARJUN: YEAH, EXACTLY.

OH, BOY, WHAT HAVE WE GOT HERE?

HAWKING: THIS MAY HURT...

BUT I AM HOPING THIS MACHINE WILL POINT THE WAY TO THE REAL REASON BEHIND WHY WE ARE HERE.

ARJUN: IT SEEMS LIKE WHICHEVER COLOR IT LANDS ON, THAT PERSON IS EITHER GOING TO GET SHOT, ELECTROCUTED, OR MAYBE WET.

I DON'T KNOW WHICH ONE'S WORSE.

KELLY: WE REALIZED, OF COURSE, WE'RE SUPPOSED TO STAND THERE AND BE TARGET PRACTICE.

HAWKING: THESE CANNONS SHOOT WET SPONGES COMPLETELY RANDOMLY.

[EXHALES] ERIC: IT'S GONNA SHOOT US.

BUT WHO?

[LAUGHS] ERIC: A DISPROPORTIONATE AMOUNT--AAH!

ARJUN AND KELLY: OH!

YOU [BLEEP].

DOES IT HURT?

SOUNDED LIKE IT HURT, BUT HE'S STILL LAUGHING.

IT WAS JUST A QUICK SHOT.

AND, UH, DEFINITELY STUNG A BIT.

[LAUGHS] ERIC: YOU GUYS SHOULD PAY ATTENTION AND KEEP LOOKING OVER THERE!

YEAH.

KELLY: MY COLOR.

AAH!

[LAUGHS] ARJUN: FINALLY.

OUCH.

[MEN LAUGH] I ENJOYED THAT TOO MUCH.

DID YOU NOW, DID YOU?!

[MEN LAUGH] IT HURT!

HERE WE GO.

HAWKING: SO, NOW, CAN THEY USE THESE GUNS TO WORK OUT WHAT HAPPENS WHEN THE RANDOM SUBATOMIC WORLD INTERACTS WITH THE WORLD GOVERNED BY THE LAWS OF NATURE?

ARJUN: SO, HOW ARE WE IMPORTANT IN THIS, APART FROM THE FACT THAT WE'RE GETTING HIT?

IT'S HARD TO THINK WHEN THAT THING IS SPINNING.

AAH!

[MAN LAUGHS] ARJUN: THE EXPERIMENT IS PROBABLY THE HARDEST FOR ME, BUT I GUESS THAT'S THE SAME AS TRYING TO DESCRIBE THE UNIVERSE OR THE WORLD OR OURSELVES.

THERE ARE SO MANY DIFFERENT FACTORS AT PLAY.

HAWKING: THE VOLUNTEERS HAVE BEEN TOLD THAT, INSIDE THIS BOX, A WEAK RADIOACTIVE SOURCE RELEASES A PARTICLE OF RADIATION.

BECAUSE THIS IS A SUBATOMIC PARTICLE WHICH BEHAVES RANDOMLY, THERE IS NO WAY OF KNOWING WHEN IT WILL BE RELEASED.

BUT WHEN IT IS, A GEIGER COUNTER DETECTS IT AND STOPS THE WHEEL.

THE COLOR DETERMINES WHO GETS SHOT.

ERIC: SO, LET'S WALK THROUGH IT.

YOU'VE GOT THE GEIGER COUNTER THAT'S THE TRIGGER.

YEAH.

YEAH.

WE KNOW THAT'S RANDOM.

KELLY: BUT THE SPINNING OF THE WHEEL IS CONSTANT.

ERIC: RIGHT, BUT THAT'S OUR INTERACTION WITH THE RANDOM.

[LAUGHTER] WHAT WE KNOW FROM THE PREVIOUS EXPERIMENT IS THAT ON THE SUBATOMIC LEVEL, EVERYTHING IS RANDOM.

WE'RE DEALING WITH SOMETHING THAT'S ON THE SUBATOMIC LEVEL, RIGHT, RADIOACTIVE MATERIAL THAT'S DECAYING.

ARJUN: YEAH.

WHAT THIS EXPERIMENT IS SHOWING IS THE UNIVERSE IS A BIT LIKE A ROULETTE WHEEL LIKE THIS WHEEL HERE, WHERE THE POTENTIAL OUTCOMES ARE DETERMINED BUT WHERE THE BALL LANDS IS COMPLETELY RANDOM.

ERIC: SO, IT IS DETERMINED THAT WE'RE ALWAYS GOING TO GET HIT, BUT IT'S COMPLETELY RANDOM WHEN!

[KELLY LAUGHS] ERIC: HA HA!

KELLY: SO, WE'RE NEITHER DETERMINED OR RANDOM.

ERIC: WE'RE A HYBRID OF THE TWO.

WHICH MEANS WE SHOULD HAVE FREE WILL.

SO, LET'S GET OUT OF HERE!

[LAUGHTER] HAWKING: THEY ARE GETTING CLOSE TO AN ANSWER.

THE RESULT IS RANDOM, BUT ONLY WITHIN A FIXED SET OF POSSIBILITIES.

NOTHING CRAZY HAPPENS, JUST ONE OF 3 POSSIBLE OUTCOMES.

WE CAN SAY THAT SOMEONE WILL CERTAINLY GET SHOT.

THAT IS DETERMINED.

BUT WE DO NOT KNOW WHO OR WHEN.

IT'S AS IF THE UNIVERSE IS DETERMINED, BUT THAT IT HAS OPTIONS, ALMOST LIKE FORKS IN THE ROAD.

SO, THE QUESTION REMAINS--ARE WE FREE TO CHOOSE OUR OWN PATH?

AND CAN WE REALLY TAKE CREDIT FOR OUR ACTIONS?

AS A SPECIES, WE HAVE TRAVELED TO THE MOON...

FOUNDED GREAT CIVILIZATIONS... AND WE'VE EVEN DONE OUR BEST TO BRING THIS PLANET TO ITS KNEES.

BUT HAVE WE ACTIVELY CHOSEN THESE OUTCOMES?

OR HAS MAN'S ACTIONS BEEN PREDETERMINED?

I BELIEVE THE ANSWERS LIE IN AN IDEA CALLED THE MANY WORLDS THEORY, WHICH SUGGESTS ALL POSSIBLE OUTCOMES OCCUR.

IT'S A STRANGE IDEA.

LET'S SEE IF THE VOLUNTEERS CAN GRASP IT BY COMING FACE TO FACE WITH THEMSELVES.

KELLY: A MASS OF PEOPLE WALK, SWARM OUT OF THE CASTLE... AND THEY'RE ALL WEARING OUR FACES.

[LAUGHS] ERIC: OH, MY GOD.

[ARJUN LAUGHS] THAT IS WEIRD.

ERIC: THAT IS SO MESSED UP.

[ARJUN LAUGHS] HAWKING: I'M HOPING THIS FINAL DEMONSTRATION WILL EXPLAIN WHY WE ARE HERE.

IT'S TOO MUCH.

IT REALLY JUST FREAKED ME OUT.

AND YOU'RE LIKE, WHAT--WHAT IS THIS, WHAT IS GOING ON!

HAWKING: THE RULES ARE SIMPLE.

WHEN THEY HEAR THE SIGNAL, EVERYONE HAS TO MOVE.

THE CHOICE IS THEIRS, BUT THEY ONLY HAVE FINITE OPTIONS-- EITHER ONE STEP LEFT, OR ONE STEP RIGHT.

[HONK] [HONK] [HONK] [HONK] [HONK] [HONK HONK] [HONK] SO, WHAT DO MY VOLUNTEERS MAKE OF ALL THIS?

AND CAN THEY SEE WHAT IT HAS TO DO WITH OUR BIG QUESTION?

ARJUN: I SEEM TO BE SCATTERED EVERYWHERE.

WHAT ARE THEY DOING BEHIND ME?

I GUESS THEY'RE MOVING EVERY TIME I MOVE.

ARJUN: I DON'T KNOW, I CAN'T PINPOINT IT, BUT THERE ARE A LOT OF DIFFERENT THINGS RUNNING THROUGH MY MIND.

ERIC: I'M SPEECHLESS.

IT'S DEFINITELY THE MOST BIZARRE THING I'VE EVER SEEN.

[LAUGHS] IT'S A COMPLETE HEAD TRIP.

HAWKING: IT MAY TAKE TIME TO GET TO THE BOTTOM OF THIS EXPERIMENT.

LET'S TRY IT AGAIN.

[HONK] [HONK] [HONK] [HONK] [HONK] [HONK] ERIC: IT SEEMS LIKE EVERY TIME I DO SOMETHING, THE OTHER ME DOES SOMETHING COMPLETELY DIFFERENT.

THE OTHERS.

I GUESS IT REPRESENTS SOME FORM OF MULTIDIMENSIONAL THING.

HAWKING: THEY'VE NEARLY SOLVED THE PUZZLE.

LET'S DO IT ONE LAST TIME.

[HONK] [HONK] ARJUN: IT COULD HAVE BEEN ABOUT TIME.

YOU KNOW, WE--WE MOVE AROUND IN DIFFERENT TIMES, OR WAS IT PART OF THE UNIVERSES?

[HONK] KELLY: MAYBE THE GRID WAS ALMOST LIKE A TIMELINE.

AND IT WAS KIND OF REPRESENTING DIFFERENT POINTS WHERE I COULD HAVE SWERVED LEFT OR RIGHT, BUT I DIDN'T.

[HONK] HAWKING: NOW THEY NEED TO WORK OUT WHAT ALL OF THIS MEANS.

ARJUN: HOW CRAZY WAS IT?

SO MANY DIFFERENT VERSIONS OF YOURSELF, EVERYWHERE.

I FOUND IT ACTUALLY ALMOST OPPRESSIVE, SEEING THAT MUCH OF ME, STARING BACK AT ME.

HA HA!

IT'S AS IF THERE WERE MANY DIFFERENT, YOU KNOW, VERSIONS OF WHAT WE WERE.

KELLY: YEAH, EXACTLY.

IT WAS KIND OF LIKE, WELL, WHAT IF IT REPRESENTED ONE PATH IN LIFE THAT I COULD HAVE GONE DOWN, BUT MAYBE DIDN'T?

AHA.

EVERY TIME YOU HAD MULTIPLES OF YOU, IT WAS A DIFFERENT OPTION WITHIN THAT PATH.

KELLY: YEAH.

LIKE IT WAS LIKE A DIFFERENT PATH OF LIFE, WHERE I MAYBE EXIST IN A DIFFERENT UNIVERSE.

YOU GET TO MAKE DIFFERENT CHOICES.

KELLY: YEAH.

THEY'RE ON DIFFERENT PATHS.

ARJUN: RIGHT, COOL.

[HONK] HAWKING: THE THEORY OF MANY WORLDS IS ACTUALLY A THEORY OF MANY UNIVERSES.

AND THAT THEORY SUGGESTS THAT IN THOSE UNIVERSES, ALL POSSIBLE OUTCOMES WILL OCCUR.

SO, EVERYTHING THAT COULD HAPPEN DOES HAPPEN, JUST IN AN ANOTHER UNIVERSE.

EACH COPY OF THE VOLUNTEERS REPRESENTS A PARALLEL UNIVERSE.

AND THE HISTORY OF THIS PARTICULAR UNIVERSE, AND THIS PARTICULAR VERSION OF YOU IN IT, HAS LED TO WHERE YOU ARE RIGHT NOW.

PARALLEL UNIVERSES ARE MORE THAN JUST AN INTERESTING THEORY.

IN FACT, IF OUR CURRENT UNDERSTANDING OF THE UNIVERSE IS CORRECT, I BELIEVE THEY ARE INEVITABLE.

WHAT'S MORE, THESE BELIEFS ARE SHARED BY RENOWNED SCIENTISTS ALL OVER THE WORLD.

CARROLL: I THINK THAT THE MANY WORLDS VERSION OF QUANTUM MECHANICS IS RIGHT.

I THINK THERE ARE MANY OTHER COPIES OF ME THAT ARE SLIGHTLY DIVERGING AS TIME GOES ON.

AND IT'S A FUNNY QUESTION BECAUSE WE MAY NEVER SEE THE OTHER UNIVERSES.

BUT THEY ARE PREDICTED BY OUR BEST UNDERSTANDING OF WHAT WE DO SEE.

AND IN MY MIND, IT'S THE DUTY OF A SCIENTIST TO COME UP WITH THE BEST UNDERSTANDING OF THE PHYSICAL WORLD THAT YOU CAN AND THEN ACCEPT ITS CONSEQUENCES, EVEN THE CONSEQUENCES YOU CAN'T SEE.

HAWKING: SO, WHAT DO MY VOLUNTEERS MAKE OF THIS IDEA?

ARJUN: WE HAVE MULTIPLE UNIVERSES, MULTIPLE DIFFERENT VERSIONS OF OURSELVES, BUT LOOKING BACK AT EVERYTHING WE'VE DONE, THIS POSITION HERE, WHERE WE ARE RIGHT NOW, ISN'T A DETERMINED FACTOR.

WE WEREN'T ALWAYS GONNA LEAD HERE.

IT WAS JUST DOWN TO OUR CHOICES.

IT'S JUST ONE OF THE POSSIBILITIES.

WE'RE HERE SIMPLY 'CAUSE OF THE CHOICES WE MADE AT THAT GIVEN POINT.

YEAH.

FULLY WITH THAT.

KELLY: YEAH.

ERIC: OUT OF POTENTIAL POSSIBILITIES.

LIMITED POSSIBILITIES, CONSTRAINED BY THE LAWS OF PHYSICS.

ERIC: YEAH, THAT'S GOOD.

[LAUGHTER] JUST AS I'M RESPONSIBLE FOR MY OWN CHOICES, I DO BELIEVE I'M RESPONSIBLE FOR MY OWN FUTURE.

I CAN'T SEE IT BUT IT'S MY OWN MAKING.

KELLY: OK. YEAH, THAT'S COOL.

KELLY: ALL RIGHT.

I CHOOSE GROUP HUG.

ARJUN: I'M DOWN WITH THAT.

[LAUGHS] KELLY: YOU KNOW YOU LOVE IT.

[LAUGHS] HAWKING: OUR BRAINS ARE BOUND BY THE LAWS OF NATURE.

THESE LAWS IMPLY THAT THERE ARE MULTIPLE UNIVERSES WHICH ALLOW FOR EACH AND EVERY POSSIBLE OUTCOME.

THIS LEADS US TO THE MOST EXTRAORDINARY IDEA-- THE UNIVERSE YOU FIND YOURSELF IN MAY BE YOUR OWN UNIQUE VERSION.

ARJUN: THE WHOLE UNIVERSE CAME TOGETHER JUST TO MAKE ME.

SO, I GUESS I AM THE UNIVERSE AND I AM ME, AT THE SAME TIME.

I REALLY HAVE NO CHOICE BUT TO BE HERE RIGHT NOW BECAUSE OF THE DECISIONS I'VE MADE.

HAWKING: SO, HERE IS WHERE I THINK WE CAN FIND MEANING IN OUR LIVES, THANKS TO SCIENCE.

ALTHOUGH WE ARE, EACH OF US, A PRODUCT OF THE UNIVERSE.

THE UNIVERSE WE LIVE IN, IS PERSONAL TO US.

ERIC: THE FACT THAT I CAN KNOW THAT EVERYTHING IS JUST IN THIS MASSIVE AMOUNT OF CHAOS WITH MAYBE INFINITE POTENTIAL UNIVERSES AND DIMENSIONS, THAT'S FINE FOR ME, IT REALLY IS.

KELLY: IT TOOK A WHOLE UNIVERSE TO MAKE ME.

THE ME WHO IS SITTING HERE RIGHT NOW.

AND THAT, I THINK, IS WHAT LEAVES ME IN THE BIGGEST STATE OF ALL.

HAWKING: NOW I THINK WE CAN ANSWER OUR CENTRAL QUESTION-- WHY ARE WE HERE IN THIS UNIVERSE RIGHT NOW?

SINCE THE BIG BANG ITSELF, THE UNIVERSE HAS BEEN GOVERNED BY THE LAWS OF NATURE.

LAWS THAT DETERMINE EVERYTHING FROM THE FORMATION OF ENTIRE GALAXIES... TO THE STABLE ORBITS OF PLANETS AROUND STARS.

THIS IS THE COSMIC LOGIC OF DETERMINISM.

IN THIS WAY, THE UNIVERSE PROVIDES STABLE CONDITIONS, ALLOWING COMPLEX CREATURES TO EVOLVE.

BUT WHEN WE LOOK CLOSER... WE DISCOVER THAT THE UNIVERSE APPEARS TO SPLIT INTO ALL POSSIBLE UNIVERSES, ALL THE TIME.

AND THAT WOULD LEAD TO A PRETTY REMARKABLE REALIZATION.

WE MAY BE TINY AND FEEBLE COMPARED TO THE MAJESTY OF THE COSMOS, BUT IN A VERY REAL WAY, IT EXISTS JUST FOR YOU.

THE UNIVERSE YOU SEE IS THE ONE THAT GIVES RISE TO YOU OUT OF ALL THE POSSIBLE UNIVERSES.

AND THAT IS WHY YOU ARE HERE.

SO, NO MATTER HOW BAD THINGS GET, I ALWAYS SAY, "DON'T LOOK DOWN AT YOUR FEET, BUT LOOK UP AT THE STARS."

ANNOUNCER: "GENIUS BY STEPHEN HAWKING" IS AVAILABLE ON DVD.

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