HAWKING: WE ALL HAVE QUESTIONS.

BIG QUESTIONS.

MAN: DID THE UNIVERSE HAVE A BEGINNING?

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

WOMAN: WHERE WAS THE BIG BANG?

AND IT'S JUST MIND-BLOWING.

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

[TIRES SQUEALING] SO WITH THE HELP OF SOME ORDINARY PEOPLE... WOMAN: PAUL, YOU'RE NOT EVEN CLOSE.

I'M SORRY.

HEH HEH.

HAWKING: AND A TEAM OF EXPERTS... MAN: WE COULD UNDERSTAND THE ORIGIN OF EVERYTHING.

HAWKING: WE ARE GOING ON THE ULTIMATE VOYAGE, A QUEST TO ANSWER THE GREATEST MYSTERIES OF THE UNIVERSE... HUH.

USING THE POWER OF THE HUMAN MIND.

BRILLIANT!

BECAUSE ANYONE CAN THINK LIKE A GENIUS.

VOICES: WHERE DID THE UNIVERSE COME FROM?

HAWKING: HAVE YOU EVER LOOKED UP AT THE NIGHT SKY AND WONDERED WHERE IT ALL CAME FROM?

IT IS HARD TO THINK OF A BIGGER QUESTION.

[RUMBLING] THE ANSWER, AS MOST PEOPLE CAN TELL YOU, IS THE BIG BANG.

[BANG] EVERYTHING IN EXISTENCE EXPANDING EXPONENTIALLY IN EVERY DIRECTION FROM AN INFINITELY SMALL, INFINITELY HOT, AND INFINITELY DENSE POINT...

CREATING A COSMOS FILLED WITH ENERGY AND MATTER.

BUT WHAT DOES THAT REALLY MEAN AND WHERE DID IT ALL BEGIN?

I THINK THAT WITH A LITTLE HELP ANYONE CAN WORK IT OUT, SO LET'S SEE IF I'M RIGHT.

I HAVE ASKED 3 CURIOUS MINDS TO JOIN ME ON A JOURNEY OF DISCOVERY.

A SERIES OF FUN CHALLENGES AWAITS THEM.

[TIRES SQUEALING] THEY WILL BE GIVEN TOOLS AND EQUIPMENT.

CAN THEY FOLLOW THE GREATEST THINKERS IN HISTORY AND DISCOVER THE ORIGIN OF THE UNIVERSE?

WOW!

WHAT A QUESTION.

HA HA HA!

WHERE DO YOU EVEN START WITH THAT?

I THINK THE UNIVERSE BEGAN IN SPACE AT SOME POINT.

ALEJANDRO, VOICE-OVER: I THINK IT'S CALLED THE BIG BANG BECAUSE IT WAS A BANG AND IT WAS BIG.

IT'S SOMETHING THAT'S ALMOST IMPOSSIBLE TO GET YOUR HEAD AROUND.

HAWKING: MY VOLUNTEERS' FIRST CHALLENGE IS TO GRASP THE ENORMITY OF THE UNIVERSE BY CALCULATING THE TOTAL NUMBER OF GALAXIES VISIBLE FROM EARTH.

SO I'VE BROUGHT THEM SOMEWHERE WITH PLENTY OF SPACE AND GIVEN THEM THIS IMAGE.

MARCIA: IT LOOKS LIKE, UH, STARS.

A PICTURE OF THE UNIVERSE.

YEAH.

ALL RIGHT.

PAUL, VOICE-OVER: THERE APPEARS TO BE STARS, BUT CLEARLY UNDERNEATH, IT SAYS, "10,000 GALAXIES."

LOOK AT ALL THE DIFFERENT SHAPES AND COLORS.

PAUL: I KNOW.

EVERY SPECK OF LIGHT HERE-- IS A SEPARATE GALAXY.

MARCIA, VOICE-OVER: IT SURPRISED ME THAT 10,000 OF ANYTHING COULD FIT IN A SQUARE FOOT, LET ALONE PICTURES OF GALAXIES.

PAUL, VOICE-OVER: IT'S A BEAUTIFUL PICTURE.

CLEARLY, IT'S A SCIENTIFIC PICTURE.

IT'S A VIEW THAT YOU WOULD NEVER SEE WITH YOUR OWN EYES.

HAWKING: THE PHOTO IS A FAMOUS ONE CALLED THE ULTRA-DEEP FIELD IMAGE.

IT'S A PART OF THE NIGHT SKY LIKE ANY OTHER, TAKEN BY THE HUBBLE SPACE TELESCOPE.

IT REVEALS NEARLY 10,000 GALAXIES, SOME OVER 13 BILLION LIGHT YEARS AWAY, YET BECAUSE THIS IMAGE COVERS ONLY A FRACTION OF THE SKY, IT SHOWS JUST A SMALL NUMBER OF THE GALAXIES OUT THERE.

PAUL, VOICE-OVER: TO SOMEHOW COME UP WITH A NUMBER OF HOW MANY GALAXIES THERE ARE IN OUR UNIVERSE, THAT WE CAN SEE, UH, WHERE TO START-- WHERE TO START WITH THAT ONE?

LET'S ASSUME THIS IS PLANET EARTH... MARCIA: RIGHT.

AND THEN WE JUST HAVE TO SEE HOW MANY OF THESE TILES WE NEED TO COVER THE WHOLE-- RIGHT.

AND OBVIOUSLY, THIS IS JUST ONE POINT, BUT THE SKY-- OR SPACE, UNIVERSE IS ALL AROUND THE SPHERE.

WE STARTED COMING UP WITH IDEAS, AND WE SAID, "OK.

HOLD ON.

"THIS IS JUST A PIECE OF THE SKY.

COULD WE JUST REPLICATE THIS PICTURE?"

HAWKING: MY VOLUNTEERS HAVE FIGURED OUT THEY NEED TO IMAGINE THE NIGHT SKY AS A SPHERE SURROUNDING OUR PLANET.

IF THEY CAN WORK OUT HOW MANY PATCHES OF SKY THE SIZE OF THEIR HUBBLE IMAGE IT WOULD TAKE TO COVER THIS SPHERE, THEN THEY WILL BE ABLE TO CALCULATE HOW MANY GALAXIES THERE ARE VISIBLE FROM EARTH.

PAUL, VOICE-OVER: THE SCALE WAS--WAS CLEARLY THE, UM--THE CRUX OF THIS MATTER.

WE HAD TO FIGURE OUT HOW MUCH OF THE SKY THAT PICTURE COVERED.

HOW MANY ARE WE GONNA NEED... TO COVER THE WHOLE-- TO COVER THE ENTIRE SKY AND OF COURSE WHAT'S BELOW OUR FEET?

FROM HERE, WE'RE GONNA TALK ABOUT, I DON'T KNOW, WHAT, 600?

YEAH.

AND THAT'S AT OUR ARMS' LENGTH.

IMAGINE--IMAGINE I'M ALL THE WAY BACK HERE.

ALEJANDRO: YEAH.

IT JUST GROWS EXPONENTIALLY.

NOW HOW MANY IS IT?

YEAH.

PAUL, VOICE-OVER: IT QUICKLY BECAME EVIDENT THAT WE NEEDED SOME REFERENCE POINTS HERE.

WE COULDN'T JUST GUESS AS TO HOW FAR AWAY WE NEEDED TO BE.

EXCELLENT.

HAWKING: I HAVE GIVEN THEM THE CRUCIAL PIECE OF EQUIPMENT THEY'LL NEED.

OOH!

TELESCOPE.

OH, WOW.

OK. NICE!

OH, WOW.

HAWKING: THIS TELESCOPE REPRESENTS THE HUBBLE SPACE TELESCOPE.

IT SEES EXACTLY THE SAME AMOUNT OF SKY, SO IF MY VOLUNTEERS CAN PRECISELY FIT THE IMAGE I'VE GIVEN THEM INTO THE TELESCOPE'S FIELD OF VIEW, THAT WILL HELP THEM WORK OUT HOW MUCH OF THE SKY IT COVERS.

WE COULD TAKE THIS IMAGE AWAY FROM THE TELESCOPE UNTIL IT FILLS THE VIEWFINDER, AND THEN WE'LL MEASURE THE DISTANCE BETWEEN THE IMAGE AND THE TELESCOPE THAT ACTUALLY MADE THE IMAGE.

YEAH, YEAH.

HAWKING: HOW FAR AWAY WILL THEY NEED TO TAKE THE IMAGE?

PAUL: YOU READY?

YEAH.

OK. LET'S DO IT.

HAWKING: WILL 300 FEET BE FAR ENOUGH?

PAUL, YOU'RE NOT EVEN CLOSE.

I'M SORRY.

HA HA HA!

PAUL: OK. WE'LL KEEP GOING BACK.

YOU'RE LOOKING SO SMALL.

[BOTH LAUGHING] HAWKING: THIS TIME, THEY'RE TRYING 600 FEET.

PAUL: OK, MARCIA.

HOW WE DOING?

DO WE NEED TO GO FURTHER?

YEAH, A LOT FURTHER.

SORRY, PAUL.

THAT'S OK.

I'LL KEEP GOING.

ALEJANDRO: LET'S GO.

WELL, I'VE JUST STARTED THINKING ABOUT HOW LITTLE AREA OF SKY WE'VE GOT HERE ON THIS THING.

HAWKING: MY VOLUNTEERS AREN'T THE FIRST TO UNDERESTIMATE THE SIZE OF THE UNIVERSE.

MAN: IN THE EARLY 20th CENTURY, PEOPLE REALLY DIDN'T KNOW WHAT WAS BEYOND OUR GALAXY.

THEY KNEW THERE WERE LOTS OF STARS IN THE SKY, BUT FOR ALL THEY KNEW, THERE WAS ONE GALAXY, UH, WHICH WE LIVED IN, AND BEYOND THERE, THERE WAS JUST NOTHING.

HAWKING: THEN CAME REVOLUTIONARY MIND EDWIN HUBBLE.

HE USED THE WORLD'S MOST POWER TELESCOPE ON TOP OF MOUNT WILSON TO STUDY SMUDGES OF LIGHT CALLED NEBULAE, THOUGHT TO BE JUST GAS AND DUST.

WHAT HE SAW CHANGED EVERYTHING.

TUROK: IT TOOK THE CONSTRUCTION OF MOUNT WILSON IN 1926 TO SHOW THAT THE NEBULAE, THESE LITTLE CLOUDS OF GAS THAT THEY'D SEEN, WERE ACTUALLY FULL OF STARS.

AND SO FROM THAT POINT ON, IT WAS CLEAR THAT THE UNIVERSE WAS FULL OF GALAXIES.

THE DISCOVERY SUDDENLY CHANGED OUR PICTURE OF THE UNIVERSE COMPLETELY.

HAWKING: ALMOST A CENTURY LATER, THE SPACE TELESCOPE THAT BEARS HUBBLE'S NAME GIVES US OUR MOST UP-TO-DATE ESTIMATE OF THE NUMBER OF OBSERVABLE GALAXIES IN THE UNIVERSE...

WHICH IS WHAT MY VOLUNTEERS ARE TRYING TO WORK OUT ON THEIR OWN.

OH!

SOMEONE'S LEGS.

PAUL: PROBABLY MY LEGS.

I'M STARTING TO COME DOWN.

YES!

OH!

I SEE WHITE BOARD.

HEY, HEY!

OK. NOW IF YOU CAN MOVE IT TO THE RIGHT NOW.

PERFECT.

YEAH!

WE GOT IT!

HA HA HA!

HEY, HEY!

HAWKING: NOW THEY HAVE FRAMED THEIR HUBBLE IMAGE WITHIN THEIR TELESCOPE'S VIEWFINDER, THEY'RE READY TO MEASURE THE DISTANCE BACK TO THE TELESCOPE.

SO THAT DISTANCE IS CRUCIAL BECAUSE THAT DISTANCE WILL THEN GIVE US THAT RADIUS THAT WE NEED IN ORDER TO CALCULATE JUST HOW MANY IMAGES WE WOULD NEED TO FILL THE WHOLE SPHERE, IF YOU LIKE.

OK, MARCIA.

WE'VE GOT OUR DISTANCE, SO, UM, WE'RE GONNA START MEASURING BACK TO YOU NOW.

EXCELLENT.

PAUL: LOOKING BACK AT THE TELESCOPE, IT'S TRULY ASTONISHING AT HOW SMALL IT MUST LOOK FROM HER END AND HOW SMALL A PIECE OF SKY WE HAVE A PHOTOGRAPH OF.

MARCIA: IT WAS SURPRISING TO SEE HOW FAR WE HAD TO WALK BEFORE THE IMAGE CAME IN VIEW.

OH, WOW.

EXCELLENT.

WE MADE IT.

WHAT HAVE WE GOT THEN?

OK.

SO THE TERRAIN WASN'T COMPLETELY FLAT, AND WE JUST GOT OVER 1,000 FEET DISTANCE, SO I THINK FOR THE PURPOSE OF THE EXERCISES, WOULD YOU AGREE TO ROUND IT TO 1,000 FEET?

OK. 1,000.

YEAH.

I THINK I AM, AS WELL.

OK. OK. HAWKING: MY VOLUNTEERS WILL NEED TO USE THE FORMULA FOR CALCULATING THE SURFACE AREA OF A SPHERE.

THEY HAVE MEASURED THE RADIUS, THE DISTANCE FROM THE TELESCOPE TO THE IMAGE.

NOW THEY'LL NEED TO SQUARE IT, MULTIPLY IT BY 4, AND THEN BY PI, 3.14.

SO WE HAVE THE 1,000-FEET RADIUS.

RIGHT.

SQUARED.

MULTIPLY THAT BY PI AND TIMES 4.

THAT'S... 12 MILLION... ALL: 560,000.

SQUARE FEET.

HAWKING: THAT'S THE ANSWER, AND THIS IMAGE IS ONE SQUARE FOOT, SO NOW THEY CAN WORK OUT THE NUMBER OF GALAXIES WE CAN SEE IN OUR UNIVERSE.

AND THIS TILE IS ONE SQUARE FOOT.

OK.

SO WHAT THAT IS SAYING IS WE WILL NEED 12,560,000 OF THESE ONES TO COVER--TO TILE THE WHOLE SKY.

TO TILE THE WHOLE SKY.

AND EACH ONE OF THOSE HAS 10,000 GALAXIES, SO IF WE GOT THAT 12,560,000 TIMES 10,000, THAT SHOULD GIVE US THE NUMBER OF GALAXIES.

125,600,000,000 GALAXIES.

HA HA HA!

WOW!

HAWKING: BY USING A DETAILED IMAGE FROM THE HUBBLE TELESCOPE AND A LITTLE MATHEMATICS, MY VOLUNTEERS HAVE ESTIMATED THE ASTONISHING NUMBER OF GALAXIES THAT SCIENTISTS HAVE OBSERVED IN OUR UNIVERSE.

WITH MORE ADVANCED TELESCOPES, WE MAY ONE DAY BE ABLE TO SEE 200 BILLION GALAXIES OUT THERE.

PAUL: IT'S JUST MIND-BLOWING BECAUSE THIS ISN'T PLANETS, THIS ISN'T STARS.

THIS IS GALAXIES WITHIN OUR UNIVERSE.

IT MADE ME FEEL SO SMALL AND INSIGNIFICANT, COMPLETELY INSIGNIFICANT.

HAWKING: MY BUDDING GENIUSES HAVE SO FAR GRASPED THE REMARKABLE SCALE OF OUR UNIVERSE, BUT CAN THEY TAKE THE NEXT STEP AND BEGIN TO FIGURE OUT WHERE I ALL CAME FROM?

THE SEARCH FOR WHERE THE UNIVERSE BEGAN IS A RELATIVELY RECENT QUEST.

UNTIL 1929, EDWIN HUBBLE, ALBERT EINSTEIN, AND MANY OTHER GREAT MINDS HAD A FIXED VIEW OF WHAT THE UNIVERSE WAS LIKE.

TUROK: EINSTEIN HAD HIMSELF PUBLISHED A PAPER ACCORDING TO WHICH THE UNIVERSE WAS STATIC.

EINSTEIN THOUGHT PHILOSOPHICALLY THAT THE UNIVERSE HAS ALWAYS BEEN HERE, WILL ALWAYS BE HERE, IS UNCHANGING, AND HE THOUGHT THAT WAS A SENSIBLE PHILOSOPHICAL PICTURE.

HAWKING: BUT THEN IN 1929, HUBBLE DISCOVERED SOMETHING THAT CHANGED EVERYTHING.

I WANT TO SEE IF THE VOLUNTEERS CAN UNDERSTAND WHAT HUBBLE FOUND...

SO THEY'VE COME HERE... TO A QUARTER-MILE DRAG STRIP... [TIRES SQUEALING] AND A VERY SPECIAL VEHICLE.

OH, MY GOODNESS!

IT'S A BUG!

YEAH, YEAH.

IT'S A BEETLE.

IT'S A BUG!

A REALLY FAST-LOOKING BUG.

IT'S UNLIKE ANYTHING I'VE EVER SEEN.

IT'S ELECTRIC.

HAWKING: THIS IS THE WORLD'S QUICKEST ACCELERATING ELECTRIC DRAG RACER-- FAST BUT VERY QUIET, AN ADVANTAGE FOR WHAT I HAVE IN STORE.

SO WHAT'S THIS?

LOOKS LIKE A S-- LIKE A SIREN OR SOMETHING.

IT IS A SIREN I THINK.

WHAT'S THIS FOR?

[SIREN] OOH!

HA HA HA!

THAT'S COOL.

HAWKING: THERE IS CHALLENGE TO USE THE SOUND OF THIS SIREN TO DETERMINE THE SPEED AND DIRECTION OF THE CAR.

MARCIA: OH, NO.

HA HA HA!

HAWKING: I HAVE ALSO GIVEN THEM A LAPTOP AND MICROPHONE TO RECORD THE SIREN'S SOUND WAVES.

WHAT DO--WHAT DO YOU THINK WE'RE DOING HERE, OK?

YESTER-- HA HA HA!

SO WHAT... HAWKING: WILL THEY WORK OUT HOW?

WE'VE GOT SOUND.

SOUND IS IMPORTANT.

SO SOUND GIVES YOU A HINT.

HAWKING: THEY SEEM TO BE ON TO SOMETHING, BUT THERE'S ONLY ONE WAY TO FIND OUT.

MARCIA, VOICE-OVER: IMMEDIATELY, I'M THINKING, "OH, WE'RE ALL GOING TO END UP RACING."

WHEW.

HAWKING: LET'S BURN SOME RUBBER.

MARCIA: OH, WOW.

HA HA HA!

ALEJANDRO: AND OFF HE GOES.

HA HA HA!

[SIREN] [TIRES SQUEALING] WHOO HOO HOO HOO!

THAT THING FLIES.

HA HA HA!

IT WAS HALFWAY DOWN THE TRACK BY THE TIME I TURNED MY HEAD.

HA HA HA!

OH, THERE HE IS.

THERE HE IS.

HA HA HA!

HOW WAS IT?

[ALL LAUGHING] IT WAS AMAZING.

WELL DONE.

OH, MY GOODNESS.

[WHOOSH] WE GOT--WE GOT SOME INTERESTING DATA HERE, AS WELL.

IS THAT MY SIREN?

THAT'S THE SIREN, SO RIGHT AROUND HERE IS WHERE YOU STARTED, AND THEN YOU'RE MOVING AWAY FROM US, MOVING AWAY FROM US, MOVING AWAY FROM US, MOVING AWAY FROM US.

MARCIA, VOICE-OVER: WE OBSERVED THE SOUND WAVES MOVING BY A SHIFT IN TONE.

[SIREN, TIRES SQUEALING] ALEJANDRO, VOICE-OVER: THERE IS CLEARLY A CHANGE IN THE FREQUENCY, AND THAT STARTED GIVING US AN IDEA.

OK. WE CAN USE THE WAVES OF SOUND TO DETERMINATE, UM, DIRECTION.

MARCIA, VOICE-OVER: AND WE FIGURED OUT THAT WE WERE PROBABLY GOING TO BE DOING SOMETHING WITH THE DOPPLER EFFECT.

HAWKING: MY VOLUNTEERS HAVE GRASPED A CRITICAL CONCEPT, AN EFFECT NAMED AFTER THE 19th CENTURY AUSTRIAN PHYSICIST WHO FIRST PROPOSED IT-- CHRISTIAN DOPPLER.

IT'S ALL ABOUT THE WAY WAVES TRAVEL FROM A MOVING OBJECT.

SOUND THROWS OFF A REGULAR PATTERN OF WAVES.

AS THE SOURCE MOVES, EACH SUCCESSIVE WAVE IS REDUCED CLOSER TO THE OBSERVER, WHO HEARS THE INCREASED FREQUENCY AS A HIGHER PITCHED SOUND.

AFTER THE SOUND PASSES, THE WAVE FREQUENCY DECREASES, AND THE OBSERVER HEARS A LOWER PITCHED SOUND.

CAN MY VOLUNTEERS FIGURE OUT HOW THIS PRINCIPLE HELPED SCIENTISTS DISCOVER WHERE THE UNIVERSE CAME FROM?

ALEJANDRO: I THINK WE SHOULD TRY THE SECOND RUN REPOSITIONING THE MICROPHONE.

HAWKING: MY VOLUNTEERS REALIZED THERE'S A BETTER PLACE TO EXPERIENCE THE DOPPLER EFFECT IN FULL.

...FAST IN THIS DIRECTION.

WE'RE GONNA PUT THE MICROPHONE HALFWAY THROUGH THE TRACK AND SEE WHAT HAPPENS.

COOL.

LET'S DO IT.

ALEJANDRO, VOICE-OVER: MARCIA'S GONNA GO IN THE CAR.

MARCIA, VOICE-OVER: I'M REALLY EXCITED ABOUT--HEH HEH-- WHAT'S GONNA GO DOWN.

HAWKING: FROM HALFWAY DOWN THE TRACK, THEY CAN RECORD DATA OF BOTH THE CAR COMING TOWARDS THEM AND GOING AWAY FROM THEM WITHOUT SO MUCH INTERFERENCE FROM SCREECHING TIRES.

ALEJANDRO: OK. WE--WE RECORDING?

YEAH.

RECORDING.

YEAH.

EVERYTHING'S GOOD.

OK, MARCIA.

WE'RE READY WHEN-- WHENEVER YOU ARE.

[TIRES SQUEALING] I'M STRAPPED UP, AND EVERYTHING'S REALLY, REALLY TIGHT... AND THEN ALL OF A SUDDEN... [SIREN] HA HA HA!

YOU GOT IT?

I GOT IT.

EXCELLENT.

THAT WAS REALLY FAST.

AS THE SIREN ON TOP OF THE CAR APPROACHES THE MICROPHONE, THE TONE IS SLIGHTLY HIGHER, AND THEN AS IT MOVES AWAY FROM THE MICROPHONE, IT GETS SLIGHTLY LOWER.

IT'S LIKE VRRROOOOMMM!

KIND OF JUST THE SOUND CHANGES.

MARCIA, ARE YOU ALL RIGHT?

MARCIA: I START CURSING BECAUSE I'M MOVING, AND MY BODY--HA HA HA-- MY BODY IS--IS STILL AT THE STARTING LINE.

IT WAS EXHILARATING.

HAWKING: MY VOLUNTEERS HAVE HEARD THE FULL DOPPLER EFFECT CONNECTION AND THE MADE THE LINK BETWEEN THE PITCH OF SOUND THEY HEAR IN THEIR VEHICLE'S DIRECTION RELATIVE TO THEM.

HELLO.

HEY, MARCIA.

HI.

HOW WAS THAT?

OH, MY GOD.

HOW WAS IT?

HAWKING: WE CAN SEE WHAT MY TRACKSIDE VOLUNTEERS EXPERIENCED.

THEY RECORDED A HIGH-PITCHED SOUND AS THE DRAGSTER APPROACHED BECAUSE THE SOUND WAVES REACHED THEM WITH A HIGHER FREQUENCY.

THE CHANGE TO A LOW-PITCHED SOUND WAS BECAUSE THEY EXPERIENCED WAVES A LOWER FREQUENCY AS THE DRAGSTER SPED AWAY.

HA HA HA!

I MEAN, WE CERTAINLY HEARD IT.

AS YOU CAME TOWARD US, YOU WERE LIKE, "NNNRRRR!"

IT JUST GOES, LIKE-- THAT DROP IN SOUND.

HAWKING: NOW USING SPECIAL AUDIO SOFTWARE WHICH MEASURES THE DROP IN FREQUENCY AS THE DRAGSTER RACES BY, MY VOLUNTEERS CAN CALCULATE THE SPEED OF THEIR VEHICLE.

A BREATHTAKING 138 MILES AN HOUR REACHED IN JUST UNDER 10 SECONDS.

MARCIA: I DIDN'T ACTUALLY THINK THAT A BUG COULD GO SO FAST.

VERY, VERY FAST.

I DIDN'T EXPECT THE CAR TO MOVE THAT--THAT FAST.

HAWKING: WILL MY VOLUNTEERS BE ABLE TO FIGURE OUT THE CONNECTION BETWEEN THE DOPPLER EFFECT AND WHAT SCIENTISTS HAVE OBSERVED IN OUR UNIVERSE?

IN 1929, SCIENTISTS DISCOVERED SOMETHING THAT TURNED THE ACCEPTED MODEL OF THE UNIVERSE ON ITS HEAD.

EDWIN HUBBLE FOUND THAT ALMOST ALL THE GALAXIES BEYOND OUR MILKY WAY ARE MOVING AWAY FROM US.

THE UNIVERSE MUST BE EXPANDING.

SO HOW DID HUBBLE GO ABOUT DETECTING THE SPEED AND DIRECTION OF GALAXIES BILLIONS OF LIGHT YEARS AWAY.

THAT'S WHAT THE VOLUNTEERS ARE TRYING TO UNDERSTAND.

MARCIA, VOICE-OVER: INITIALLY, I THOUGHT WE'RE MEASURING SOUND, BUT, YOU KNOW, GALAXIES DON'T MAKE A SOUND.

PAUL, VOICE-OVER: SO CLEARLY, WERE NOT GONNA BE USING SOUND TO LISTEN TO THE SOUND COMING FROM GALAXIES, BUT, UM, SOUND IS A WAVE, UM, JUST LIKE LIGHT TRAVELS IN WAVES, AS WELL, SO WHEN THE SOURCE IS MOVING, IT CHANGES THE FREQUENCY.

IT WIDENS THE FREQUENCY AS IT'S MOVING AWAY.

SO WHEN IT COMES TO GALAXIES, WE DON'T LOOK FOR SOUND, BUT WE KIND OF MEASURE THE WAVES OF THE LIGHT.

[TIRES SQUEALING] HAWKING: THAT'S RIGHT.

SO WILL MY VOLUNTEERS GRASP THE BEAUTIFULLY SIMPLE WAY TO DETECT A CHANGE IN THE FREQUENCY OF LIGHT?

PAUL: WE SORT OF FIGURED OUT THAT WHEN WE GET A RAINBOW LIGHT HITS WATER AND IT SPLITS INTO DIFFERENT COLORS.

WE ALSO GET DIFFERENT FREQUENCIES, AND COLOR AND FREQUENCY ARE LINKED WHEN IT COMES TO LIGHT, SO WE'RE SORT OF WONDERING WHETHER PERHAPS THE--THE COLOR OF GALAXIES MIGHT GIVE US A CLUE AS TO WHICH WAY THEY'RE MOVING-- TOWARDS US OR AWAY FROM US, AND MAYBE THAT'S THE WAY THAT WE CAN MEASURE WHICH DIRECTION GALAXIES ARE MOVING, BY STUDYING THE COLOR OF THE LIGHT FROM THEM.

HAWKING: THEY'VE GOT IT.

HIGH-FREQUENCY LIGHT APPEARS BLUE.

LOW-FREQUENCY LIGHT APPEARS RED.

MY VOLUNTEERS HAVE REALIZED THE SPEED AND DIRECTION A GALAXY IS TRAVELING CAN BE DEDUCED SIMPLY BY OBSERVING ITS COLOR... AND IN 1929, THAT'S PRECISELY HOW EDWIN HUBBLE OBSERVED GALAXIES WERE MOVING AWAY FROM US.

TUROK: HUBBLE WAS LOOKING AT THE MOST DISTANT OBJECTS HE COULD FIND.

THAT'S WHAT YOU DO WITH THE BIGGEST TELESCOPE YOU HAVE.

IF YOU SEE A STAR LIKE THE SUN AND YOU PUT IT AT A MUCH GREATER DISTANCE, OBVIOUSLY IT WOULD APPEAR MUCH DIMMER, AND SO HE USES THAT FACT TO TELL HIM THE DISTANCE OF THE GALAXIES.

WHAT HE NOTICES IS THAT THE GALAXIES WHICH ARE DIMMER AND THEREFORE FURTHER AWAY ARE REDDER, AND THE INTERPRETATION OF THIS REDDENING IS SOMETHING CALLED THE DOPPLER SHIFT, WHICH IS THAT IF SOMETHING IS MOVING AWAY FROM YOU THE LIGHT WE RECEIVE IS SHIFTED INTO THE RED.

IT WAS A VERY RADICAL IDEA THAT THE UNIVERSE WAS EXPANDING BECAUSE IF YOU TOOK IT SERIOUSLY, IT IMPLIED THERE WAS A BEGINNING... THAT YOU COULD EXTRAPOLATE THE EXPANSION BACKWARDS IN TIME, AND IT WOULD HAVE IMPLIED THAT EVERYTHING IN THE UNIVERSE EMERGED FROM WHAT WE NOW CALL A SINGULARITY.

WITH HUBBLE'S DISCOVERY, IT BECAME CLEAR VERY DRAMATICALLY THAT POTENTIALLY WE COULD UNDERSTAND THE ORIGIN OF EVERYTHING.

HUBBLE'S DISCOVERY WAS RECOGNIZED AS VERY IMPORTANT AT THE TIME, BUT THE NOTION THAT WE COULD ACTUALLY UNDERSTAND THE BIG BANG AT THAT TIME SEEMED A STEP TOO FAR.

YOU KNOW, HOW WOULD WE EVER ANSWER QUESTIONS THAT GRANDIOSE?

HAWKING: IF SCIENTISTS WERE TO BELIEVE THAT THE BIG BANG THEORY SOLVED THE PROBLEM OF WHERE THE UNIVERSE CAME FROM, THEY'D NEED EVIDENCE IT HAPPENED PRECISELY AS THE THEORY DESCRIBED.

SCIENTISTS PREDICTED THE BIG BANG'S INITIAL BURST OF LIGHT FROM JUST AFTER THE BIG BANG WOULD BE DETECTABLE TODAY AS MICROWAVE RADIATION.

THE RACE WAS ON TO FIND IT... AND THE FIRST LEAD CAME FROM AN UNLIKELY SOURCE, AMERICAN RADIO ASTRONOMERS ARNO PENZIAS AND ROBERT WILSON.

WOMAN: PENZIAS AND WILSON WERE INTERESTED IN STUDYING OUR GALAXY.

THEY WERE USING NEW TECHNOLOGY, NEW RADIO TELESCOPES TO LOOK AT RADIO WAVES, BUT WHEREVER THEY LOOKED IN THE SKY AND HOWEVER THEY TUNED THEIR TELESCOPE, THEY KEPT PICKING UP THIS VERY FAINT SIGNAL OF LIGHT.

NOW FOR A WHILE, THEY WERE CONVINCED THAT IT MUST BE SOMETHING THAT WAS GETTING INTO THE TELESCOPE THAT WASN'T REAL, THAT WAS EITHER SOME PROBLEM WITH THEIR TELESCOPE ITSELF OR SOMETHING INSIDE THE TELESCOPE ITSELF, BUT THERE WAS NO EXPLANATION FOR THIS FAINT LIGHT THAT APPEARED TO BE COMING FROM SPACE AND EVERYWHERE IN SPACE, AND QUITE QUICKLY, IT BECAME COMPLETELY OBVIOUS THAT WHAT PENZIAS AND WILSON WERE SEEING WITH THEIR DISH POINTING AT DIFFERENT PARTS OF THE SKY WAS EXACTLY THIS BIG BANG SIGNAL.

HAWKING: IT WAS A HISTORIC MOMENT.

WE SAW ALMOST BACK TO THE BIG BANG ITSELF, AND SCIENTISTS HAD THE EVIDENCE THEY HAD BEEN SEARCHING FOR.

DUNKLEY: SO THIS SIGNAL WAS HUGELY IMPORTANT FOR CONVINCING PEOPLE THAT THE BIG BANG HAD HAPPENED, AND SO QUITE QUICKLY, PEOPLE WHO HADN'T PREVIOUSLY BEEN CONVINCED BY THE BIG BANG, THEIR MINDS WERE CHANGED.

HAWKING: BUT WE DON'T HAVE TO TAKE THEIR WORD FOR IT.

WHAT'S REMARKABLE IS THE ECHO OF THE BIG BANG IS SOMETHING WE CAN ALL LISTEN TO.

DUNKLEY, VOICE-OVER: SO ONE OF THE REMARKABLE THINGS ABOUT THE COSMIC MICROWAVE BACKGROUND RADIATION IS YOU CAN ACTUALLY PICK IT UP AND HEAR IT WITH A RADIO.

THIS LIGHT IS HITTING US ALL THE TIME, AND ITS WAVELENGTH IS THE RIGHT KIND OF WAVELENGTH THAT A RADIO CAN ACTUALLY TURN IT INTO A SIGNAL YOU CAN HEAR, AND WHEN YOU TURN BETWEEN CHANNELS ON AN OLD-FASHIONED ANALOGUE RADIO, YOU CAN HEAR THAT HISS, THAT LITTLE FUZZY NOISE THAT COMES BETWEEN RADIO STATIONS.

IT IS ACTUALLY LIGHT FROM THE BIG BANG, AND YOU CAN ACTUALLY HEAR IT ON A RADIO, AND THAT'S EXTRAORDINARY.

HAWKING: BUT THIS IS ONLY PART OF THE STORY.

WHAT'S CRUCIAL TO UNDERSTANDING THE BEGINNING OF EVERYTHING IS NOT SIMPLY THAT THE UNIVERSE IS EXPANDING BUT THE UNEXPECTED WAY IN WHICH IT DOES EXPAND BECAUSE EDWIN HUBBLE'S DATA FROM HIS OBSERVATION OF MOVING GALAXIES CONTAINS A FURTHER SECRET, ONE THAT I HOPE MY VOLUNTEERS WILL GRASP IN THEIR NEXT CHALLENGE.

TO SEE IF MY VOLUNTEERS CAN WORK OUT WHERE THE UNIVERSE CAME FROM, I HAVE BROUGHT THEM SOMEWHERE THEY CAN EXERCISE MORE THAN JUST THEIR MINDS.

MARCIA: TRACK AND FIELD.

VERY COOL.

ALEJANDRO: INDOOR ARENA.

OK. PAUL, VOICE-OVER: WE'RE IN AN INDOOR RUNNING TRACK.

WHAT'S THIS GOT TO DO WITH THE UNIVERSE?

MORNING, GUYS, MORNING.

ALL RIGHT.

RIGHT.

SO WE HAVE SOME SIGNS.

HAWKING: MY VOLUNTEERS HAVE THE EQUIPMENT THEY NEED TO ORGANIZE A SPECIAL RACE... SAFETY PINS.

SAFETY PINS.

HAWKING: MIMICKING THE MOVEMENT OF GALAXIES IN SPACE.

WILL THEY FIGURE IT OUT?

OH, SO THESE ARE DIFFERENT GALAXIES AND THEIR, UH, DISTANCE FROM EARTH.

OH, WAIT.

GUYS, LOOK.

THEY HAVE, LIKE, LITTLE GALAXIES ON THEM.

PAUL: OH, THEY DO.

LOOK AT THAT.

HA HA HA!

THIS IS PERFECT.

MARCIA, VOICE-OVER: I NOTICED THAT ALL OF THE T-SHIRTS HAVE GALAXIES ON THEM, SO I'M ASSUMING THAT EACH OF THESE RUNNERS WILL REPRESENT A GALAXY.

YOU KNOW WHAT THESE LOOK LIKE TO ME?

THESE LOOK LIKE RACE NUMBERS.

RACE NUMBERS.

MARCIA, VOICE-OVER: EACH OF THE RACE BIBS CONTAINS NAME OF THE GALAXY AND HOW FAR THE GALAXY IS IN LIGHT YEARS AWAY FROM EARTH.

I THINK WE JUST PUT THESE ON OUR LOVELY VOLUNTEERS.

OK. AND THEN WE CAN HAVE A RACE.

SOUNDS LIKE A GOOD IDEA.

YEP.

LET'S HAVE A RACE.

LET'S HAVE A RACE.

HAWKING: TO HELP THEM UNCOVER THE SECRET IN HUBBLE'S DATA, MY VOLUNTEERS WILL NEED TO SET UP THE STARTING POINT OF THEIR RACE CAREFULLY.

MARCIA: ALL RIGHT.

SO WE GOT ALL OUR GALAXIES.

ALEJANDRO: YEAH.

WE HAVE TO DO EVERYTHING TO SCALE, RIGHT?

FIRST OF ALL, WE HAVE TO ESTABLISH OUR EARTH.

WHICH IS GONNA BE OUR START LINE.

THESE STARTING BLOCKS ARE NOT IN LINE.

THEY'RE ALL AT DIFFERENT DISTANCES FROM OUR STARTING POINT.

BECAUSE THE DISTANCES THEY HAVE IS LIGHT YEARS FROM EARTH.

SO I'M THINKING WE NEED TO-- WE NEED TO GET THESE GUYS IN THE RIGHT ORDER.

IN ORDER.

OK.

THE COGS START TURNING.

"HANG ON A MINUTE.

"PERHAPS WE NEED TO BE MATCHING UP THESE NUMBERS WITH THE STARTING POSITIONS FOR THESE RUNNERS."

HAWKING: GOOD WORK.

THEY'RE CORRECTLY REPLICATING THE LAYOUT OF OUR UNIVERSE AS WE SEE IT FROM PLANET EARTH.

SHE'S RIGHT HERE.

THEN IT'S 210 BILLION.

HAWKING: AND EACH RUNNER IS STANDING AT THE CORRECT DISTANCE FROM EARTH OF THE GALAXY THEY REPRESENT.

PAUL: 12.8 BILLION.

AND 13 BILLION THIS WAY.

YOU GET THE BIGGEST HEAD START.

ALEJANDRO: COOL!

MARCIA: SO WE'VE GOT OUR GALAXIES ALIGNED.

ALEJANDRO: ALIGNED.

PAUL: LET'S RUN IT.

LET'S RUN IT.

LET'S SEE WHAT HAPPENS.

OK. ALL RIGHT.

HAWKING: BUT THIS IS NO ORDINARY RACE, AND THERE MAY BE SOME SURPRISES IN STORE.

WILL THEY WORK OUT WHAT IT MEANS?

MARCIA, VOICE-OVER: I'M EXPECTING THAT WHEN I PULL THE TRIGGER EVERYONE WILL FLY FORWARD.

GALAXIES READY.

[BANG] PAUL: WOW.

HEY.

YOU KNOW WHAT?

THEY'RE RUNNING AT DIFFERENT SPEEDS.

HAWKING: WELL, I DID SAY THAT THIS IS NO ORDINARY RACE.

PAUL, VOICE-OVER: SOME OF THEM JOG, SOME OF THEM WALK.

ALEJANDRO, VOICE-OVER: IT TOOK ME A WHILE TO REALIZE WHAT WAS HAPPENING.

THERE'S NO COMPETITION.

IT'S JUST--IT'S JUST HOW IT'S MOVING.

I WASN'T EXPECTING THAT.

SO DID I.

THERE SHOULD BE A CLUE IN THAT.

THERE'S A CLUE IN THAT.

RIGHT.

PAUL, VOICE-OVER: SO CLEARLY, THE RACE ISN'T ABOUT THE PHYSICAL PROWESS OF EACH INDIVIDUAL ATHLETE.

IT'S GONNA BE MORE DETERMINED BY THE NUMBERS THAT WE'VE ASSIGNED TO THEM.

SO SO FAR, WHAT WE HAVE LEARNED?

13 BILLION.

13 BILLION IS FLYING.

YEAH.

SHE'S SUPERFAST.

800,000 IS WALKING.

OK.

THE CLOSER YOU WERE TO THE START LINE...

THE START, YEAH.

UM, THE SLOWER YOU MOVE.

PAUL, VOICE-OVER: THE SECRET THAT WE DISCOVERED WAS THAT GALAXIES THAT ARE THE FURTHEST AWAY FROM EARTH ARE ALSO THE ONES TRAVELING THE FASTEST AWAY FROM EARTH.

MARCIA: THE FURTHER THEY GET FROM EARTH, THE FASTER THEY TRAVEL.

HAWKING: MY VOLUNTEERS HAVE DISCOVERED A VITAL CLUE IN HUBBLE'S DATA.

NOT ONLY DID HUBBLE'S OBSERVATION OF A DOPPLER RED SHIFT REVEAL GALAXIES WERE MOVING AWAY...

IT REVEALED THE MOST DISTANT GALAXIES GLOWED A DEEPER SHADE OF RED.

THEY WERE RECEDING FASTER INTO THE DEPTHS OF THE UNIVERSE, SOME AT SEEMINGLY REMARKABLE SPEEDS.

TUROK: THESE WERE ABSOLUTELY REVOLUTIONARY IDEAS, AND IN THE MID-1920s, THIS DEBATE ABOUT THE NATURE OF THE WORLD, THE NATURE OF REALITY WAS AT ITS MOST, UH, DRAMATIC.

HAWKING: THIS EXTRAORDINARY CLUE IN HUBBLE'S DATA WAS A KEY TURNING POINT OF DISCOVERING WHERE THE UNIVERSE CAME FROM.

CAN MY VOLUNTEERS TAKE THE NEXT STEP TO FIGURE OUT WHAT'S MAKING GALAXIES MOVE THE WAY THEY DO?

SO... ALEJANDRO: OK. QUITE CLEARLY, WE'RE IN AN ICE RINK.

OH, YEAH.

OH, MY GOODNESS.

HAWKING: TO REVEAL THE EXTRAORDINARY TRUTH BEHIND HOW THE UNIVERSE EXPANDS, MY VOLUNTEERS WILL NEED TO BRAVE THE ICE.

WE'RE GONNA PLAY ICE HOCKEY?

NO.

WE'VE GOT OUR GALAXY JERSEYS AGAIN.

OH, YEAH.

THE GALAXIES ARE ON JERSEYS.

WE'RE GONNA BE THE GALAXIES TODAY.

WE REALIZED THAT THERE IS SOME ICE SKATING EQUIPMENT, SO IT DOESN'T TAKE A GENIUS TO FIGURE OUT THAT WE ARE GOING IN THE ICE RINK WITH THEM, SO THAT WAS QUITE-- QUITE SCARY.

SO LET'S--SO, UM, I GUESS WE'RE PUTTING SOME KIT ON.

HAWKING: THEIR CHALLENGE IS TO REPLICATE THE BIG BANG ON ICE TO WORK OUT WHY GALAXIES THAT ARE FARTHEST FROM EARTH MOVE FASTEST.

FIRST, THEY'LL NEED TO GET THEIR SKATES ON...

BUT I'VE MADE AN UNUSUAL ADDITION TO THEIR SKATING GEAR.

MARCIA: ON THE TABLE, THERE ARE LEAF BLOWERS WITH BALLOONS ON THEM, WHICH IS VERY ODD.

SHALL WE DO IT?

YEAH.

LET'S GIVE IT A GO.

OH.

OH, WOW!

HAWKING: WILL MY VOLUNTEERS WORK OUT WHAT IS MAKING GALAXIES MOVE THIS WAY?

I THINK WE SHOULD BE ON THE ICE.

YEAH.

LET'S GO ON THE ICE.

PAUL, VOICE-OVER: WE FIGURED THAT IF HEAD TO THE CENTER OF THE ICE THAT WOULD BE A GOOD PLACE TO START IN ORDER TO FIND OUT HOW WE'RE ACTUALLY GONNA REENACT THIS BIG BANG.

I CAN HARDLY DO THIS...

I KNOW.

WITH A LEAF BLOWER.

I KNOW.

IT'S SO HARD TO DO WITH A LEAF BLOWER.

AAH!

OH!

I'M GETTING THE HANG OF THIS.

OKEY-DOKEY.

ALEJANDRO, VOICE-OVER: WE NEED TO FIND A WAY TO USE THESE BALLOONS AND THESE LEAF BLOWERS TO RE-CREATE HOW THE GALAXIES ARE MOVING.

IT'S AN EXPLOSION ESSENTIALLY, ISN'T IT?

RIGHT.

WE'RE THINKING THAT WE NEED TO CAUSE SOME SORT OF EXPLOSION.

WHAT DO WE HAVE THAT IS EXPANDING?

OBVIOUSLY, THESE BALLOONS.

DO WE PUT THESE BALLOONS TOGETHER MAYBE AND THEN THAT IS THE CAUSE OF THE EXPANSION?

SO IF WE EXPAND THEM AGAINST EACH OTHER, WE GO BACKWARDS?

SEE IF WE GO BACKWARDS.

OH, I LIKE IT.

MARCIA, VOICE-OVER: WE DIRECT ALL OF OUR BLOWERS TOWARD EACH OTHER.

1... 1... 2, 3.

2, 3.

WHOA!

HA HA HA!

HA HA HA!

MAYBE WE HAVE TO HAVE IT A LITTLE BIT HIGHER.

AGREED.

OK. OH, MY GOSH.

ALL RIGHT, GUYS.

1, 2, 3.

OH!

HA HA!

PAUL, VOICE-OVER: UNFORTUNATELY, THE THING THAT LETS US DOWN IS OUR ABILITY ON THE ICE.

HAWKING: MY VOLUNTEERS MAY NEED A DIFFERENT STRATEGY.

WE NEED SOME HELP.

YEAH.

MARCIA, VOICE-OVER: WE ENLISTED THE PRO TEAM.

PAUL: WE WERE WONDERING IF YOU COULD STEP IN AS OUR STUNTMEN.

PAUL, VOICE-OVER: SO WE APPROACHED THESE GUYS AND ASKED FOR 3 VOLUNTEERS TO TAKE OUR PLACE ON THE ICE.

PAUL: YOU WANT TO COME WITH ME?

PAUL, VOICE-OVER: WE SQUEEZED THEM IN TOGETHER, POSITIONED THE BALLOONS WHERE WE WANTED THEM, AND ON THE COUNT OF 3 ASKED THEM TO SWITCH THEM ON.

PAUL: OK. 3, 2, 1, ACTION.

YEAH.

THANKS.

THAT WAS GREAT, GUYS.

THANK YOU.

PAUL, VOICE-OVER: IT WAS CLEAR THAT WE HAD A PRINCIPLE THAT WAS WORKING, BUT IT WASN'T QUITE THE BIG BANG THAT WE WERE LOOKING FOR.

YOU WANT TO SCALE IT UP?

ALEJANDRO: BRING MORE PLAYERS?

GET MORE PLAYERS IN?

MORE BALLOONS, MORE PLAYERS?

MAYBE.

LET'S BRING EVERYBODY IN.

HAWKING: NOW MY VOLUNTEERS ARE BEGINNING TO GRASP HOW AN EXPANDING UNIVERSE COULD WORK.

WOULD YOU GUYS GIVE US A HAND?

HAWKING: WILL THEIR SCALED-UP SIMULATION BRING THEM CLOSER TO FINDING OUT WHERE THE UNIVERSE BEGAN?

PAUL: LET'S HAVE SOME FUN.

PAUL, VOICE-OVER: WE'LL START WITH OUR 3 GUYS THAT WE DID, BUT THEN WE'LL CREATE A LINE, A QUEUE, IF YOU LIKE, IN BEHIND EACH OF THE 3 GUYS IN THE MIDDLE.

ALEJANDRO: HOW MANY YOU HAVE THERE?

PAUL: I HAVE 5.

ALEJANDRO: OK. ARE YOU READY GUYS?

PLAYERS: YEAH!

ALL RIGHT.

IN 3, 2, 1, ACTION!

SO THE BALLOONS IN THE CENTER INFLATE.

AS THE BALLOONS WERE EXPANDING, THE FURTHER BACK YOU WERE FROM THE CENTER, THE MORE SPEED YOU HAD, THE MORE DISTANCE YOU TRAVELED.

WHAT DO YOU THINK THIS IS-- ALEJANDRO: I THINK THIS EXPLAINS WHY THE GALAXIES THAT WERE FURTHER WAY WERE MOVING... MOVING FASTER.

FASTER.

FASTER THAN THE ONES WHO WERE... AH.

THAT MAKES SENSE.

AT THE BEGINNING.

WE DISCOVERED THAT THOSE GALAXIES ARE ALL MOVING AWAY FROM EACH OTHER, UM, AND THE FURTHER AWAY THEY ARE FROM EACH OTHER, THE FASTER THEY'RE MOVING AWAY.

THAT WAS VERY INTERESTING TO SEE.

HAWKING: SO WHAT DOES THIS MEAN FOR THE WAY THE UNIVERSE IS EXPANDING?

MARCIA: WE STARTED TO THINK ABOUT WHAT IS ACTUALLY CAUSING THE PLAYERS TO MOVE.

IF THE GALAXIES ARE ALL MOVING AWAY FROM EACH OTHER, WHAT IS IT ABOUT THE BALLOON THAT MAKES THAT HAPPEN?

THE GALAXIES THEMSELVES AREN'T MOVING OR ACCELERATING, CONTROLLING ITS SPEED.

IT'S JUST THE SPACE BETWEEN THEM...

THE SPACE BETWEEN THEM.

RIGHT.

THAT'S--THAT'S EXPANDING.

RIGHT.

YEAH.

MARCIA, VOICE-OVER: WHAT'S EXPANDING IS OBVIOUSLY NOT THE PLAYERS.

THE PLAYERS ARE REMAINING THE SAME, AND IF THE PLAYERS REPRESENT GALAXIES, THEN THE GALAXIES AREN'T REALLY EXPANDING.

PAUL: THE BALLOONS INFLATE, SO SPACE IS INFLATING.

RIGHT.

SO THE GALAXIES ARE KIND OF COMPLETELY IRRELEVANT THEMSELVES.

WE HAVE TO FOCUS ON THE SPACE BETWEEN THE GALAXIES.

ALEJANDRO, VOICE-OVER: IT IS AN EYE-OPENING MOMENT WHEN WE REALIZE IT IS THE SPACE WHAT IS EXPANDING, AND THAT WAS VERY EASY TO SEE TODAY BECAUSE WE WERE ABLE TO SEE THE BALLOONS PUSHING EACH PLAYER.

PAUL: I'M COMING TO REALIZATIONS THAT THINGS AREN'T THE WAY I THOUGHT THEY WERE, UH, AND THAT'S--THAT'S WHAT'S REALLY EXCITING HERE.

HAWKING: THEY'VE GRASPED IT, A CONCEPT SCIENTISTS CALL THE UNIFORM EXPANSION OF SPACE.

WHEN THE UNIVERSE EXPANDS, NOT EVERYTHING IN IT EXPANDS, TOO.

SO YOU SHOULD THINK OF SPACE EXPANDING, BUT THE OBJECTS INSIDE SPACE, LIKE GALAXIES AND STARS, ARE NOT EXPANDING.

THEY'RE STANDING THE SAME SIZE.

IT'S JUST AS IF YOU TOOK SPACE AND STRETCHED IT UNIFORMLY.

SO IF GIVEN TWO POINTS WILL BE MOVING AWAY AT SOME SPEED, THEN IF YOU TAKE TWO POINTS SEPARATED BY TWICE THE DISTANCE, THEY'RE MOVING AWAY AT TWICE THE SPEED, AND THAT'S HUBBLE'S LAW.

HUBBLE'S LAW, THE OBSERVATION OF AN EXPANDING UNIVERSE, WAS A REVELATION, BUT IT WASN'T A COMPLETE SURPRISE BECAUSE BELGIAN COSMOLOGIST AND PRIEST GEORGES LEMAITRE HAD ALREADY WORKED ON THE THEORY BEHIND IT.

DUNKLEY: LEMAITRE STARTED OFF WITH THIS WONDERFUL THEORY THAT WAS AROUND AT THIS POINT, WHICH WAS EINSTEIN'S NEW THEORY OF GENERAL RELATIVITY.

THIS BEAUTIFUL SET OF EQUATIONS WERE KIND OF RIPE FOR STUDYING FURTHER AND TO APPLYING TO OUR ENTIRE UNIVERSE, AND THIS IS WHAT HE WANTED TO TRY AND UNDERSTAND WAS HE COULD HE TAKE THIS NEW THEORY OF GRAVITY THAT EINSTEIN HAD COME UP WITH AND APPLY IT TO THE WHOLE OF SPACE?

EINSTEIN'S EQUATIONS TELL US THAT SPACE ITSELF GETS DISTORTED BY THE STUFF THAT LIVES IN SPACE.

MATTER BENDS SPACE, AND SPACE TELLS MATTER HOW TO MOVE IN THAT SPACE.

AND SO LEMAITRE SIMPLIFIED THE UNIVERSE, APPLIED EINSTEIN'S THEORY TO IT, AND HE DISCOVERED THAT IF YOU FILL SPACE WITH STUFF-- UH, AS WE KNOW IT TO BE, THE UNIVERSE ISN'T COMPLETELY EMPTY-- UM, IT SHOULD CHANGE, IT SHOULD GROW.

HAWKING: LEMAITRE'S THEORY THAT THE UNIVERSE WAS CHANGING WAS PUBLISHED IN 1927.

IT MARKED THE BIRTH OF THE BIG BANG THEORY AND THE REVOLUTION IN HOW WE UNDERSTAND OUR UNIVERSE.

NOW TO PIECE TOGETHER WHERE THE UNIVERSE CAME FROM, MY VOLUNTEERS WILL NEED TO GO OVER WHAT THEY'VE LEARNED SO FAR.

THEY HAVE GRASPED THE ENORMITY OF THE UNIVERSE'S 200 BILLION GALAXIES.

MARCIA: IT MADE ME FEEL SO SMALL AND INSIGNIFICANT.

[TIRES SQUEAL] THEY HAVE DISCOVERED THAT THE UNIVERSE IS EXPANDING... WHOO HOO HOO HOO!

AS DISTANT GALAXIES ARE MOVING AWAY FROM US... THAT THING FLIES!

AND THAT THOSE GALAXIES FARTHEST FROM EARTH MOVE FASTER THAN THOSE NEARBY... ACTION!

BECAUSE SPACE ITSELF IS UNIFORMLY EXPANDING, PUSHING GALAXIES FURTHER APART.

PAUL: THE GALAXIES THEMSELVES AREN'T MOVING.

IT'S JUST THE SPACE BETWEEN THEM THAT'S EXPANDING.

RIGHT.

HAWKING: BUT THERE'S SOMETHING ABOUT THIS UNIFORM EXPANSION OF SPACE THAT HAS EXTRAORDINARY AND UNEXPECTED CONSEQUENCES THAT CAN TELL US WHERE THE UNIVERSE CAME FROM... SOMETHING I HOPE MY VOLUNTEERS WILL UNCOVER IN THEIR FINAL CHALLENGE.

OK. "MIDDLE OF THE UNIVERSE MACHINE."

"1 BILLION YEARS AGO."

WELL, THAT IS A CLUE BECAUSE THAT'S WHAT WE'VE BEEN TRYING TO FIND OUT, WHERE--WHERE EVERYTHING BEGAN.

PAUL: I GUESS THESE REPRESENT GALAXIES.

AND THAT'S HOW THE UNIVERSE LOOKED THEN.

WHAT DO WE HAVE ON THE OTHER SCREEN?

ON THE OTHER SCREEN, WE HAVE "NOW."

"NOW."

THE OTHER SCREEN SAYS, "NOW."

THEY LOOK PRETTY MUCH THE SAME.

THEY ALMOST LOOK IDENTICAL.

BUT WE'RE NOT LIT.

BUT WE'RE NOT LIT UP.

I THINK WE SHOULD TURN THESE ON.

ALEJANDRO: ALL RIGHT.

LET'S SEE.

HAWKING: THE SCREENS REPRESENT MAPS OF A SMALL PART OF OUR UNIVERSE, AND THE LIGHTS REPRESENT GALAXIES.

THINK OF THEM AS TWO SNAPSHOTS OF THE SAME AREA OF SPACE TAKEN 1 BILLION YEARS APART.

PAUL: SO HOW ABOUT WE PUT OUR MACHINE TOGETHER?

ALEJANDRO: OVERLAP THE SCREENS?

OK. MARCIA: ALL RIGHT, GUYS.

GET TO IT.

I'LL DIRECT YOU.

ALEJANDRO, VOICE-OVER: MARCIA-- VERY CLEVER--LET THE BOYS CARRY THE SCREEN.

HA HA HA!

I WASN'T GONNA DO ANY OF THE HEAVY LIFTING.

ALEJANDRO, VOICE-OVER: AND WE PUT THE TWO SCREENS OVERLAPPING EACH OTHER.

PAUL: YOU'RE IN?

IS IT IN?

YES, IT'S IN NOW.

YEAH.

BRILLIANT.

OK. OK. OK. PAUL, VOICE-OVER: WE STEP BACK AND HAVE A LOOK, AND IT'S CLEAR THAT THEY'RE NOT THE SAME.

HA HA HA!

THEY'RE NOT THE SAME.

THEY ARE NOT THE SAME.

PAUL, VOICE-OVER: IT LOOKS LIKE EVERYTHING IS RADIATING OUT FROM A POINT.

SO IT LOOKS FROM A BILLION YEARS AGO TO--TO TODAY EVERYTHING HAS MOVED AWAY SLIGHTLY.

SAME EXACT PATTERNS.

SAME PATTERNS, BUT THEY HAVE MOVED.

PAUL, VOICE-OVER: IT LOOKED REALLY GOOD.

IT LOOKED AMAZING.

IT WAS LIKE JUMPING TO WARP SPEED AND YOU GET THAT--PSSHEEW-- STARBURST SORT OF EFFECT, YEAH.

MARCIA: AND WE FIGURED OUT THAT THAT IS SUPPOSED TO REPRESENT THE EXPANSION OF SPACE THAT WE HAD SEEN IN OUR--OUR PREVIOUS EXPERIMENT.

SO NOW WE'VE GOT THESE GALAXIES.

THEY'RE ALL POINTING TO SOME BLACK SPOT IN SPACE AS--AS PROBABLY WHERE THEY'VE ALL ORIGINATED FROM.

THE MIDDLE IS WHERE THE UNIVERSE BEGAN BECAUSE EVERYTHING IS--IS MOVING AWAY FROM A SINGLE POINT.

SO THE SIGNIFICANCE OF FINDING THE MIDDLE IS TO ANSWER THE BIG QUESTION-- WHERE--WHERE DID THE BIG BANG HAPPEN?

HAWKING: THAT'S THE IDEA.

SO WILL MY VOLUNTEERS WORK OUT HOW TO TAKE THE NEXT LOGICAL STEP TO FIND WHERE THE UNIVERSE BEGAN?

MAYBE WE CAN MOVE THIS-- MOVE THE SCREEN?

YEAH.

WE CAN MOVE THE SCREEN.

SO WE'RE GONNA TRY TO MOVE IT TO ALIGN IT.

ALEJANDRO, IF WE GET ON THE HANDLES AND, MARCIA, YOU TELL US WHERE YOU WANT IT-- OK.

BRILLIANT.

OK. WHERE DO YOU WANT US TO MOVE IT FOR?

TO THE LEFT.

LEFT.

OK--OH.

A LITTLE BIT TO THE RIGHT, THEN DOWN A LITTLE BIT MORE.

HAWKING: I THINK THEY'LL BE IN FOR A SURPRISE.

MARCIA: IT REALLY IS STRAIGHT DOWN.

DOWN, DOWN, DOWN, DOWN.

HUH.

OK, GUYS.

ONE GALAXY IN THE MIDDLE IS ALIGNED.

OK. AND THE REST?

AND THE REST OF THEM ARE JUST SLIGHTLY OFF.

SLIGHTLY OFF.

IN A UNIFORM MANNER.

I'M TRYING TO EXPLAIN THIS TO YOU GUYS SO THAT YOU UNDERSTAND-- BECAUSE YOU C-- YOU CAN'T SEE IT.

PAUL: WELL, WHY DON'T YOU COME AND HOLD THIS?

LET ME HAVE A LOOK.

YEAH, YEAH.

PERFECT.

AND THEN I CAN MAYBE-- PERFECT, PERFECT.

HAWKING: IT LOOKS LIKE MY VOLUNTEERS ARE ABOUT TO UNCOVER WHAT THE UNIFORM EXPANSION OF SPACE MEANS FOR WHERE THE UNIVERSE CAME FROM.

PAUL: OH, WOW.

HAWKING: THE TEAM HAS FIGURED OUT ALIGNING THEIR GALAXIES IS NOT AS SIMPLE AS IT SEEMS.

PAUL: I SO SEE WHAT YOU MEAN NOW.

I SEE WHAT YOU MEAN NOW.

HAWKING: THEY CAN ONLY LINE UP ONE GALAXY WITH ITS BILLION-YEAR-OLDER COUNTERPART AT A TIME.

HOW WILL THEY FIGURE OUT WHAT THIS COULD MEAN?

PAUL, VOICE-OVER: SO WE STARTED TO THINK ABOUT HOW VIEWPOINT MADE A DIFFERENCE AS TO WHAT IT WAS WE WOULD SEE.

SO WE CAME UP WITH THE IDEA OF PERHAPS CHANGING OUR VIEWPOINT.

SO NOW I'M GONNA PICK ANOTHER GALAXY BUT ON THIS SIDE.

I'M GONNA PICK THIS GALAXY NOW, AND I'M GONNA ALIGN IT UP WITH ITS BILLION-YEAR-OLD PARTNER BEHIND, OK?

WE'LL GO TO MARCIA.

KEEP GOING.

KEEP GOING.

KEEP GOING, KEEP GOING.

WE PICKED A GALAXY, UM, AND LINED IT UP WITH THE ONE BEHIND.

KEEP GOING.

STOP.

PERFECT.

HA HA!

SO NOW I'VE MADE THAT THE CENTER OF THE UNIVERSE, EVERYTHING ELSE IS MOVING OUT FROM THAT POINT.

HA HA!

AND THAT WAS A-- NOT A LIGHT BULB MOMENT, BUT THAT WAS LIKE A "STAR TREK" MOMENT.

THIS IS VISUALLY INCREDIBLE.

MARCIA: IT'S--IT'S COOL.

IT REALLY IS.

IT'S REALLY COOL.

IT WAS--IT JUST CHANGED.

THE WHOLE PICTURE JUST CHANGED.

SUDDENLY, THE MIDDLE OF THE UNIVERSE SEEMED TO CHANGE.

SO EVERYTHING WAS RADIATING FROM THE GALAXY I'D CHOSEN.

ALEJANDRO, YOU HAVE TO HAVE A GO AT THIS.

OK.

I'M COMING.

LET'S--LET'S DO THIS.

LET ME ALIGN TWO.

YOU HAVE TO SEE IT.

ALL RIGHT.

SO HOW ARE WE SUPPOSED TO FIND THE MIDDLE OF THE UNIVERSE IF EVERY TIME WE MOVE IT IT CHANGES?

I'M GONNA CHOOSE THIS GALAXY, AND I'M GONNA ALIGN THAT ONE NOW.

OK. HAWKING: NOW MY VOLUNTEERS ARE REALLY ON TO SOMETHING.

ALEJANDRO: A LITTLE BIT TO THE LEFT.

BRILLIANT.

FROM THAT POINT OF VIEW, NOW I CAN SEE ALL OF THE GALAXIES MOVING AWAY FROM THAT, AND I THINK I'M ON TO SOMETHING HERE.

RIGHT.

SO SEEMINGLY BEING ABLE TO MAKE ANY POINT AT THE CENTER OF THE UNIVERSE, WE START TO SLOWLY REJECT THE IDEA THAT WE'RE GONNA FIND A POINT IN SPACE THAT IS THE CENTER OF THE UNIVERSE.

ALEJANDRO, VOICE-OVER: AND THAT'S WHEN I START THINKING ANY SINGLE POINT COULD BE THE CENTER.

I--I BELIEVE THAT THIS MACHINE IS TELLING US THAT THE MIDDLE OF THE UNIVERSE IS A MATTER OF OUR PERSPECTIVE.

YEP.

RIGHT?

IT'S WHEREVER YOU'RE LOOKING FROM.

WHEREVER YOU'RE LOOKING FROM.

HAWKING: MY VOLUNTEERS HAVE MADE AN EXTRAORDINARY CONNECTION.

PAUL, VOICE-OVER: EVERYWHERE IS THE CENTER OF THE UNIVERSE BECAUSE IT ALL CAME INTO EXISTENCE AT THE SAME TIME, AND IT'S ALL MOVING AWAY FROM EVERYWHERE AT THE SAME TIME.

HAWKING: SPACE DIDN'T EXIST BEFORE THE BIG BANG.

NOW SPACE IS EXPANDING IN ALL DIRECTIONS, AND THESE SIMPLE FACTS MEAN WHEREVER YOU ARE IN THE UNIVERSE, IT'S THE CENTER, WHERE IT ALL BEGAN.

ALEJANDRO: SO WE DID IT.

WE SOLVED THE QUESTION.

WE KNOW WHERE THE UNIVERSE BEGAN.

WE DO.

HERE.

HEH.

RIGHT HERE.

WELL DONE, TEAM.

BRILLIANT.

IT WAS HERE ALL ALONG.

UNDER OUR NOSE.

IT WAS HERE ALL ALONG.

RIGHT UNDER OUR NOSE.

THAT'S WHERE IT BEGAN.

IT WAS RIGHT UNDER OUR NOSE ALL ALONG, YEAH.

MARCIA, VOICE-OVER: TO SAY THAT THE UNIVERSE STARTED AT THE TIP OF MY NOSE, I'M JUST WALKING AROUND, LIKE--HA HA HA--THIS IS THE COOLEST THING EVER, BUT OBVIOUSLY, IF IT STARTED AT THE TIP OF MY NOSE, IT COULD HAVE STARTED AT THE TIP OF EVERYBODY'S NOSE.

HAWKING: THEY'VE GOT IT BECAUSE AT THE BIG BANG THE TIP OF EVERYONE'S NOSE, IN FACT ALL MATTER IN THE ENTIRE UNIVERSE, WAS ONE INFINITELY SMALL POINT.

MY VOLUNTEERS HAVE DECIPHERED THE VAST AND COMPLEX NATURE OF THE UNIVERSE, AND OUR JOURNEY HAS CERTAINLY THROWN UP SOME PRETTY BIG THOUGHTS.

I'VE LEARNT SOMETHING MOST PEOPLE DON'T KNOW.

I'VE--I'VE LEARNT WHERE THE UNIVERSE BEGAN.

ALEJANDRO, VOICE-OVER: I'M HAPPY WE CAME TO THAT ANSWER BECAUSE IT MAKES PERFECT SENSE AND MAKES ME LOOK AT THE UNIVERSE, THE EARTH, AND IN GENERAL MY LIFE FROM A COMPLETELY DIFFERENT PERSPECTIVE.

MARCIA: I'M COMFORTABLE WITH BEING UNCOMFORTABLE, AND I LIKE IT WHEN THINGS EXPAND MY MIND.

HAWKING: THE EXPANSION OF THE UNIVERSE DESCRIBED BY THE BIG BANG THEORY IS ONE OF THE MOST IMPORTANT INTELLECTUAL DISCOVERIES OF THE 20th CENTURY.

IT TELLS US WHERE EVERYTHING CAME FROM AND WHERE WE'RE GOING.

WHAT HAPPENS NEXT?

I BELIEVE THE UNIVERSE WILL CONTINUE TO EXPAND FOREVER...

BUT AT LEAST WE ALL KNOW WHERE IT ALL BEGAN-- RIGHT AT THE TIP OF YOUR NOSE.

♪ Hawking: Have you ever wondered what you really are?

My name is Stephen Hawking.

I believe that anyone can answer big questions for themselves.

Volunteer: It's just amazing.

Hawking: Follow the greatest thinkers in history.

Think like a genius.

♪