All language subtitles for PBS.Genius.By.Stephen.Hawking.2of6.Are.We.Alone.720p.HDTV.x264.AAC.MVGroup.org.eng

STEPHEN HAWKING:
WE ALL HAVE QUESTIONS...

BIG QUESTIONS.

WILL: DO ALIENS EXIST?

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

LINDSAY: HOW WOULD WE FIND THEM?

LISTEN TO THAT!

HAWKING:
MY NAME IS STEPHEN HAWKING.

AND I BELIEVE THAT ANYONE

CAN ANSWER BIG QUESTIONS
FOR THEMSELVES.

LINDSAY: WHOA!

HAWKING: SO WITH THE HELP
OF SOME ORDINARY PEOPLE...

SIAN: OH, MY GOD!

HAWKING:
AND A TEAM OF EXPERTS...

DAVID CHARBONNEAU:
THE FIRST TIME I SAW THAT,

IT BLEW MY MIND.

HAWKING: WE ARE GOING
ON THE ULTIMATE VOYAGE--

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

SIAN: I CAN HEAR
INTELLIGENT LIFE!

HAWKING: USING THE POWER
OF THE HUMAN MIND.

SIAN: RIGHT THERE!

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.

"ARE WE ALONE?"

HAWKING: HAVE YOU EVER
LOOKED UP AT THE NIGHT SKY

AND WONDERED IF THERE
IS ANYONE OUT THERE...

ALIEN CREATURES,

PERHAPS LIVING ON A PLANET
ORBITING SOME FAR-AWAY STAR?

IF YOU CONTEMPLATE THESE THINGS,

YOU ARE IN GOOD COMPANY.

"ARE WE ALONE?" IS ONE

OF HUMANITY'S
MOST IMPORTANT QUESTIONS,

CONTEMPLATED BY SOME OF THE
SMARTEST MINDS WHO EVER LIVED.

[OVERLAPPING TRANSMISSIONS]

YET I BELIEVE ANYONE CAN PRETTY
MUCH ANSWER IT FOR THEMSELVES.

LET'S SEE IF I'M RIGHT.

I'VE ASKED 3 CURIOUS MINDS

TO JOIN ME ON A JOURNEY

OF DISCOVERY.

A SERIES OF EXCITING
CHALLENGES AWAITS THEM.

THEY WILL BE
GIVEN TOOLS AND EQUIPMENT.

CAN THEY FOLLOW THE GREATEST
THINKERS IN HISTORY

TO GRASP HOW LIKELY IT IS
THAT WE ARE ALONE?

ARE WE ALONE?
ARE WE ALONE?

I THINK THAT'S
A BIG QUESTION.

THE HONEST ANSWER
IS I DON'T KNOW.

I HOPE,

MAYBE BELIEVE,
THAT WE ARE NOT ALONE.

ON THE OTHER HAND,
I WOULDN'T MIND

BELIEVING THAT
WE ARE SO SPECIAL.

I'D SAY, "BEAM ME UP!"

I WANT TO GO, I WANT TO EXPLORE,

I WANT TO SEE
WHAT'S OUT THERE.

HAWKING: THE FIRST STEP TO
FINDING OUT THE LIKELIHOOD

OF ALIENS IS TO ASK, WHAT
ULTIMATELY MAKES LIFE POSSIBLE?

SIAN: HOW DID LIFE
START HERE ON EARTH?

OK, WE HAVE LOADS OF DIFFERENT
TYPES OF LIFE ON EARTH.

HOW DID THAT HAPPEN?

I THINK A SOURCE OF
ENERGY IS ESSES--

ESSENTIAL.

HAWKING: CONSIDER WHAT
POWERS LIFE ON OUR LUSH PLANET,

THE EARTH.

IT IS ENERGY
FROM OUR STAR,

THE SUN.

SO PERHAPS OTHER STARS COULD BE
POWERING LIFE ON OTHER WORLDS

IN OUR GALAXY--THE MILKY WAY.

TO BEGIN TO WORK OUT
HOW LIKELY THAT IS,

THE FIRST THING THE VOLUNTEERS
MUST DO IS UNDERSTAND

JUST HOW MANY STARS
THERE ARE IN OUR GALAXY.

WHAT IF THIS TINY GRAIN
OF SAND REPRESENTS

A SINGLE STAR IN THE MILKY WAY?

AND ON THIS SPOON
ARE 50,000 GRAINS OF SAND.

SO THAT WOULD BE 50,000 STARS.

USING THIS AS A STARTING POINT,
CAN MY VOLUNTEERS TAKE A GUESS

AT THE NUMBER OF STARS
IN OUR GALAXY

AND FIND A WAY TO VISUALIZE IT?

A SPOON OF SAND. HMM.

ALL RIGHT.

THIS IS 50,000 STARS.

WOW.

SIAN: AND IT FITS
ON A SPOON.

I KNOW. THAT'S CRAZY.
THAT'S CRAZY.

SO WHAT CAN WE
DO FROM HERE?

CAN YOU GUESS HOW MANY
STARS WE HAVE IN THE GALAXY?

UM, WELL, THAT'S
A GOOD QUESTION.

YEAH. I KNOW THAT THERE
ARE BILLIONS FOR SURE,

BUT I DON'T WANT
TO SAY...
WILL: BILLIONS?

I'M THINKING
A HUNDRED BILLION.

I THINK I HEARD
THAT SOMEWHERE.

WILL: ONE BILLION.
SAY--TRY WITH THAT.

IT WILL BE AN EASY FIGURE.
ONE BILLION?

NO? YOU WANT MORE? OK. OK.

SOME MORE.

I'M LEANING
TOWARDS BIGGER.

WILL: BIGGER
THAN 100 BILLION?

LINDSAY: YEAH.
NO.

I--I LIKE
100 BILLION,

BUT I DON'T KNOW IF
I LIKE ONE BILLION.

LINDSAY: I THINK IT'S
SOMEWHERE BETWEEN

90 BILLION AND 100 BILLION.

SIAN: WHY DON'T WE
WEIGH THIS AND FIND OUT

HOW MUCH THIS WEIGHS,

AND THEN WE CAN SCALE UP
TO THE 100 BILLION?

SIAN: THERE GOES
ALL OF OUR STARS.

WILL: 50,000 STARS
WEIGHED...

70 GRAMS.
70 GRAMS.

SIAN: 70 GRAMS.

LINDSAY: OK.
SO LET'S DO THE MATH.

100.

140,000 KILOGRAMS.

SIAN:
140,000 KILOGRAMS...

HAWKING:
THEY'VE CORRECTLY CALCULATED

THEY'LL NEED
140,000 KILOGRAMS OF SAND

TO REPRESENT THEIR GUESS
OF 100 BILLION STARS.

THAT'S A LOT OF SAND.

WHY DON'T WE WEIGH A BUCKET

AND SEE HOW MANY
BUCKETS WE NEED?

SIAN: THAT SOUNDS GREAT.
WILL: OK.

GOT IT? UGH!

SIAN: ALL RIGHT.
WHAT DO WE HAVE?

LINDSAY: ALL RIGHT.

SO LOOKS LIKE IT'S ABOUT
14 KILOGRAMS.

THAT IS 10,000 BUCKETS.
MY GOSH...

YEAH, THAT'S
GONNA BE CRAZY.

SO WE CAN TRY PILING UP
UP TO A BILLION STARS.

AND THEN A HUNDRED TIMES
OF THAT WOULD GIVE US

AN IDEA OF HOW BIG
OUR GALAXY IS...

WILL: WE ESTIMATE IT.

BASED ON ESTIMATION.

LET'S DO IT. OK.
LINDSAY: ALL RIGHT.

IT'S HARD WORK
SHOVELING BUCKETS OF STARS.

HAWKING: FINALLY,
WE ARE BEGINNING TO GRASP

THE SCALE OF OUR GALAXY.

IT'S A SCIENTIFIC
JOURNEY THAT BEGAN LONG AGO...

WHEN MYTHS
TOLD THAT THE MILKY WAY WAS

A CELESTIAL PATHWAY
MADE FROM MILK.

THEN 500 YEARS AGO,
A REVOLUTIONARY MIND REVEALED

WHAT IT REALLY IS
FOR THE FIRST TIME.

FRANCISCO DIEGO:
GALILEO GALILEI IS

PERHAPS THE FOUNDER
OF MODERN SCIENCE.

HE COMES, UH, IN
THE LATE 1500s, EARLY 1600s

WITH A NEW WAY OF
LOOKING AT THE WORLD.

THIS NEW WAY IS EXPERIMENT.

HAWKING: GALILEO'S
BIG EXPERIMENT WAS

TO TAKE A TECHNOLOGY
DEVELOPED FOR NAVIGATION AT SEA

AND TURN IT TO THE SKIES.

HIS TELESCOPE REVEALED
A BEAUTIFUL TRUTH.

DIEGO: ONCE GALILEO POINTS
HIS TELESCOPE TO THE MILKY WAY,

HE REALIZES, HAVING THE--
THE AID OF THE TELESCOPE

THAT THE MILKY WAY
IS MADE OUT OF STARS.

I CANNOT IMAGINE
THE--THE EXCITEMENT

OF--OF GALILEO
AT THAT POINT.

IT'S A MAJOR, MAJOR DISCOVERY.

HAWKING: GALILEO
HAD TAKEN A MAJOR STEP

IN THE SCIENTIFIC QUEST
TO QUANTIFY OUR GALAXY...

A JOURNEY I HOPE
MY VOLUNTEERS WILL FOLLOW.

TODAY WE KNOW THE MILKY WAY IS

A VAST SPIRAL OF STARS, PLANETS,
GAS, AND INTERSTELLAR DUST.

BUT EVEN SO,
WE CAN ONLY ESTIMATE

THE AMAZING NUMBER
OF STARS IT CONTAINS,

WHICH IS ALSO WHAT
THE VOLUNTEERS ARE TRYING TO DO.

WILL: THAT'S IT.

ONE BILLION STARS.

SIAN: THAT'S
A BILLION STARS.

I THINK MY
ORIGINAL ESTIMATE

OF 100 BILLION
WAS TOO BIG.

LINDSAY: LET'S SEE.
100 PILES...

SIAN: THAT'S A LOT.

LINDSAY:
THAT'S A LOT.

WELL, MAYBE
IT'S ONLY A BILLION STARS.

HAWKING: SCIENTISTS NOW ESTIMATE

THE NUMBER
OF STARS IN OUR GALAXY

WITH A COMPLEX
MATHEMATICAL EQUATION.

AND THE ANSWER
IS QUITE EXTRAORDINARY.

AN ESTIMATED
300 BILLION STARS.

THAT'S 3 TIMES THEIR FIRST GUESS

AND 300 TIMES
THEIR REVISED ESTIMATE.

HOW WRONG CAN YOU BE?

OHH!

OHH, MY GOSH.

OH, MY GOSH.

WOW.

300 BILLION.

I MEAN,
THAT'S JUST UNBELIEVABLE.

I MEAN, IT'S JUST SO BIG.

I THINK WE'RE GONNA
NEED SOME MORE SAND.

LINDSAY: THAT IS A LOT.

WHOA!
OH, MY GOD.

LINDSAY: WOW!

SIAN: THAT'S CRAZY.

WILL: NOW THAT'S A GALAXY.

OH, YEAH.
WOW...

WHOO!

HAWKING:
NOW THEY'VE GOT THE EQUIPMENT

TO MATCH THE SCALE OF THE JOB.

HOW MUCH SAND WILL THEY NEED?

LINDSAY: THAT'S 8 TONS.

WE NEED A TOTAL OF 416 TONS,
AND WE HAVE 40 SO FAR.

SIAN: 362 TO GO.

MOVING THE SHOVELS

AND, YOU KNOW,
DIRECTING THE TRUCKS

JUST MADE ME THINK, LIKE, HOW--
REALLY HOW BIG THE GALAXY IS.

61 TONS SO FAR.

SIAN: MIND-BOGGLING.

HAWKING: I THINK THIS IS
THE ONLY WAY TO REALLY GRASP

THE NUMBER OF STARS
IN JUST OUR GALAXY.

EACH 8-TON SHOVEL
REPRESENTS 6 BILLION STARS...

EACH ONE A POSSIBLE ENERGY
SOURCE FOR AN ALIEN WORLD.

SIAN: WE COULD HAVE NEVER
BUILT THIS PILE ON OUR OWN.

LINDSAY: NO WAY.
I WOULD BE DEAD BY NOW.

SIAN: I GOT TO SAY,
THAT'S A HECK OF A LOT

OF STARS
WE GOT GOING ON THERE.

LINDSAY: WOW.

OK, WE NEED 15 MORE TONS.

SHOVEL NUMBER ONE,

YOU READY TO DO THE LAST ONE?

LAST ONE FINALLY!

WHOO-HOO!

SIAN: I NEVER WOULD HAVE
GOT IT UNTIL I SAW IT.

HAWKING: SO THIS
IS A GALAXY'S WORTH OF STARS--

A PILE THAT WEIGHS 416 TONS.

ABOUT 300 BILLION
INDIVIDUAL GRAINS OF SAND.

THIS I GET.

SIAN, VOICE-OVER: TO THINK
OF THE MILKY WAY BEING THAT BIG

WITH THAT MANY STARS,
LIKE, HOW IS THAT EVEN POSSIBLE?

I THINK NEXT TIME I'M GONNA
BE ABLE TO SEE THE STARS,

IT'S JUST GONNA
CRUSH ME A BIT TO THINK.

IT'S ABOUT 300 BILLION.

THAT'S OUR GALAXY.

ALL OF IT JUST MADE OF
TINY, TINY,

LITTLE GRAIN OF SAND.

AND IF YOU GET JUST ONE
RIGHT HERE, THAT'S OUR SUN.

NOW WHEN I SEE THAT, IT'S
NOT EVEN PROBABLE ANYMORE.

THERE--THERE HAS TO
BE LIFE SOMEWHERE.

SIAN: WHEN I LOOK UP
AT THE NIGHT SKY

AND I SEE ALL THOSE STARS,

IT ADDS ANOTHER LAYER OF MEANING

TO WHY WE ARE HERE
AND WHERE WE'RE GOING.

LINDSAY: IT IS MAKING ME THINK

ABOUT ACTUALLY
WHAT THE MEANING OF LIFE IS.

HAWKING: WITH A BIT OF
HELP, MY BUDDING GENIUSES

HAVE GRASPED THE REMARKABLE
NUMBER OF STARS IN OUR GALAXY--

POTENTIAL POWERHOUSES
FOR LITTLE GREEN MEN AND WOMEN.

HAWKING: THE NEXT STEP IN
FINDING OUT IF WE ARE ALONE

IS TO ASK, WHAT ELSE
WOULD AN ALIEN LIFE FORM

PROBABLY NEED?

SO WHAT'S THE NEXT STEP?

WELL, WE ARE A PLANET
AROUND OUR STAR.

AND PERHAPS THE CLOSEST
THING WE CAN LOOK FOR

ARE PLANETS THAT ORBIT

AROUND THESE
BILLIONS OF STARS.

SIAN, VOICE-OVER: SO WHAT I FIND
INTERESTING IS THAT YOU HAVE

ALL OF THESE STARS
IN OUR MILKY WAY,

BUT THAT DOESN'T MEAN ANYTHING
UNLESS YOU HAVE PLANETS.

HAWKING: THE EXISTENCE
OF FAR-AWAY PLANETS IS

A SURPRISINGLY OLD IDEA.

IN 1584, ITALIAN PHILOSOPHER
GIORDANO BRUNO PROPOSED

THE STARS
WERE SURROUNDED BY PLANETS.

IT WAS THOUGHT THESE PLANETS
COULD BE POPULATED BY ALIENS.

UNFORTUNATELY,
BRUNO WAS BURNED AT THE STAKE

FOR WHAT WAS THEN
AN OUTRAGEOUS IDEA.

I AM LUCKY THAT NOW

IS A SAFER TIME TO BE
A COSMOLOGIST.

TODAY IT SEEMS LOGICAL
THAT IF LIFE STARTED HERE

ON OUR PLANET,
IT COULD ALSO BEGIN

ON OTHER PLANETS
ORBITING OTHER STARS.

BUT HOW DO WE FIND THEM?

LINDSAY: WHOA. WOW.

SIAN: WHA--WHAT THE...?

HAWKING: FINDING PLANETS IN THE
VASTNESS OF SPACE IS NOT EASY.

[SIAN, LINDSAY,
AND WILL SPEAKING INDISTINCTLY]

HAWKING: HERE ARE SOME
SCALE MODELS OF PLANETS.

USING THESE SMALL SPHERES,

CAN THE VOLUNTEERS
WORK OUT WHAT THE SOLUTION IS?

SIAN: MY GOD,
THAT IS CRAZY.

LINDSAY: THIS--
THIS IS A THEATER.

WHAT THE HECK?
I LOVE IT!

OH, WOW.

LINDSAY: IT'S GREAT!

SIAN: THAT'S COOL.
THAT'S REALLY NICE.

LINDSAY: WOW!
WE'RE ON STAGE.

LINDSAY, VOICE-OVER:
WE SEE THIS BRIGHT SPOTLIGHT,

AND I JUST IMMEDIATELY
CONNECTED,

THAT'S PROBABLY A STAR
THAT, YOU KNOW--

THAT'S THE ANALOGY
WE ARE WORKING WITH.

SIAN: OH, WOW.

LINDSAY: RIGHT
THERE, RIGHT?

WILL: OH, DEFINITELY.

OH, THAT'S COOL.

LINDSAY:
STAR AND THE PLANETS.

SIAN: LOOK AT THIS.

LINDSAY:
LOOKIT HERE.

SIAN: THERE IS A SHADOW.

LINDSAY: MAKES
A SHADOW. RIGHT.

SIAN: COULD YOU ACTUALLY
SEE THE SHADOW OF A PLANET

ON--IT'D HAVE
TO BE A BIG PLANET.

WILL: WELL, I THINK THAT'S
WHAT YOU'RE LOOKING FOR.

YOU KNOW, YOU'RE LOOKING
AT YOUR STAR.

AND IF IN A REGULAR--
YOU KNOW, EVERY MONTH,

EVERY 5 YEAR, EVERY 10
YEARS, YOU SEE A SHADOW

COMING IN OR A CHANGE
OF YOUR ENERGY LEVELS.

YES!

IF THE STAR HAS PLANETS,

IT WOULD BE ORBITING
AROUND THE STAR.

AND WHEN IT PASSED THROUGH
THE--THE LINE BETWEEN THE SUN

AND THE EARTH, WE WOULD
PROBABLY SEE A DIM IN THE LIGHT

JUST BECAUSE IT BLOCKS
THE LIGHT.

AND SO THAT'S WHAT
WE WANT TO LOOK FOR.

THE PROBLEM WAS WE HAD THIS
HUGE DISTANCE BETWEEN THE STAR

AND WHERE WE HAD
SET UP THE PLANETS.

SO DO YOU THINK THAT THE--

THE DISTANCE BETWEEN
THE PLANETS AND THE STAR

SHOULD BE MUCH CLOSER
THAN THE DISTANCE

BETWEEN THE OBSERVER
FROM EARTH

AND THE PLANETS, RIGHT?

ABSOLUTELY.

AND WE ONLY HAVE THAT
MUCH SPACE TO GO BACK.

'CAUSE THAT'S A HUGE SPACE,

SO MAYBE WE SHOULD ACTUALLY
GO UP TO THE BALCONY.

HAWKING: THAT'S GOOD.

THEY'RE CORRECTLY REPLICATING

THE LAYOUT OF
A DISTANT SOLAR SYSTEM

AND ANTICIPATING A PROBLEM.

THE PLANETS
ARE COMPARATIVELY TINY,

AND THEIR STAR IS
VERY BRIGHT.

I THINK WE'RE LOOKING
FOR A FLICKER

AS IT PASSES IN FRONT.

YEAH.

SIAN: HEY, LINDSAY,
YOU UP THERE?

LINDSAY: I'M UP HERE.

OK, LET'S GO
WITH THE FIRST--UM,

NUMBER ONE--
THE SMALLEST PLANET.

LET'S SEE IF WE
CAN SEE THAT, OK?

WILL: I THINK
IT'S TOO SMALL.

ALL RIGHT. OK.

UM, LET'S TRY
NUMBER TWO.

LINDSAY:
COULD YOU SEE IT?

SIAN: WE COULDN'T
SEE ANYTHING.

OH, WAIT. WHOA.

LINDSAY:
THAT WAS MY ARM.

[LAUGHTER]

NOW, WE COULD SEE THAT.

SO THAT WORKED OUT
JUST FINE.

I'VE GOT MY GLASSES,

SO I'M GONNA
PUT MY GLASSES ON

AND SEE WHAT I CAN SEE
'CAUSE THIS IS CRAZY.

WILL: I'LL JUST
FOLLOW YOU UP.

OK. ALL RIGHT. WAIT.

LET'S GO TO NUMBER THREE
AND SEE WHAT'S GOING ON.

LET'S TRY
THE BIGGER ONE, OK?

ALL RIGHT. I HAVE
PLANET NUMBER THREE

RIGHT IN THE MIDDLE.

CAN YOU SEE ANYTHING?

STILL NOTHING
FOR ME.

I GOT NOTHING. UH-UH.
I CAN'T SEE ANYTHING.

EVEN IF WE KNOW WE HAVE
THE PLANET RIGHT IN FRONT OF US,

THE LIGHT IS SO BRIGHT

THAT YOU--YOU CAN'T SEE
THE SHADOW OF THE PLANET.

ALL RIGHT.
WELL, WHAT DO YOU THINK?

BECAUSE WE
CAN'T SEE IT.

WE CAN'T SPOT THE LIGHT,
WE CAN'T SPOT THE FLICKER,

THE SHADOW...

HAWKING:
THEY MAY HAVE A PROBLEM,

BUT THEY'RE ON THE RIGHT TRACK.

ANY PLANET ORBITING
A DISTANT STAR IS

TOO SMALL TO SEE DIRECTLY
FROM EARTH.

IT IS LOST IN THE GLARE
OF ITS STAR.

BUT SCIENTISTS REALIZED

THEY MAY BE ABLE TO SPOT
DISTANT PLANETS ANOTHER WAY.

AS A PLANET ORBITS BETWEEN
ITS STAR AND US ON EARTH,

ASTRONOMERS HYPOTHESIZED
IT WOULD FRACTIONALLY DECREASE

THE AMOUNT
OF STARLIGHT REACHING US.

THE EFFECT IS RATHER
LIKE THE STAR WINKING.

BUT IT WAS JUST A THEORY

UNTIL 1999, WHEN
A TEAM OF SCIENTISTS USING

JUST A SIMPLE TELESCOPE
WITH A LIGHT METER

ATTEMPTED TO DETECT THIS EFFECT
ON A DISTANT STAR FOR REAL.

CHARBONNEAU: IN 1999
AS A GRADUATE STUDENT,

I HAD THE VERY SPECIAL PRIVILEGE
OF BEING THE FIRST HUMAN TO SEE

A PLANET PASS
IN FRONT OF ANOTHER STAR.

THE FIRST TIME I SAW
THAT PLOT, IT BLEW MY MIND.

THIS WAS EXACTLY THE SIGNAL
THAT I WAS HOPING TO SEE,

AND THERE IT WAS
ON THE COMPUTER IN FRONT OF ME.

HAWKING: 150 LIGHT YEARS AWAY,

PLANET OSIRIS, AS IT WAS
UNOFFICIALLY NAMED, IS HUGE--

A GAS GIANT ABOUT 220 TIMES
THE MASS OF PLANET EARTH.

CONFIRMING THE EXISTENCE
OF SUCH A WORLD

WAS A MONUMENTAL ACHIEVEMENT.

BUT IS IT POSSIBLE
TO FIND MUCH SMALLER PLANETS

MORE LIKE THE EARTH...

PLANETS THAT COULD BE
POPULATED BY ALIENS?

IN THEIR SEARCH FOR ALIEN LIFE,

SCIENTISTS HAVE SHOWN
THERE IS A WAY TO DETECT PLANETS

OUTSIDE OUR SOLAR SYSTEM.

LINDSAY, ARE YOU
IN POSITION...

HAWKING:
WITH A NEW SET OF TOOLS,

CAN MY VOLUNTEERS WORK OUT

HOW THE SCIENTISTS
MADE THEIR BREAKTHROUGH?

SIAN: OH, MY GOD.

WILL: OH, NICE.

SIAN: THAT'S A TELESCOPE.

OH, MY GOD.

WILL: DO YOU KNOW
HOW TO MAKE IT WORK?

SIAN: UM, NO.

BUT IT CAN'T BE THAT
HARD, I DON'T THINK.

I THINK THAT'S LIKE
A SENSOR.

SO YOU PUT IT
ON THE TELESCOPE

AND IT--TELLS YOU
THE INTENSITY OF LIGHT.

YEAH. I THINK WE CAN
ACTUALLY MEASURE THE LUMENS,

THE CHANGE IN LUMENS.

SO WE MEASURE HOW
MUCH WE GET TO THAT.

SIAN: ALL RIGHT. I'M TOTALLY
EXCITED ABOUT THIS.

WILL: OH, WOW.

SIAN: OH, MY GOD!

OK. SO THAT'S WHAT WE
PICKED FROM THE STAR.

SIAN: SO THAT'S
OUR BASELINE.

YEAH.
YOU WANT TO MARK THAT?

NOW, THAT'S OUR UPPER ZERO.

THAT'S WITH NO PLANET.

OK, SOUNDS GOOD.

HAWKING: THEIR LIGHT METER,
WHICH IS MUCH MORE SENSITIVE

THAN THE HUMAN EYE, WILL REACT

TO EVEN THE TINIEST CHANGE
IN LIGHT INTENSITY.

SIAN: ALL RIGHT, LINDSAY,

WE'RE GOING TO TRY PUTTING
THE PLANET ACROSS AGAIN.

LET'S START WITH
THE SMALLEST ONE.

WILL: I CAN FEEL
THE TENSION.

SIAN: I KNOW!

SIAN: OK, I DON'T
SEE ANYTHING.

WILL: OH, OH, OH.

SIAN: OH, MY GOD!

OK, WE TOTALLY
SAW SOMETHING CHANGE.

IT WAS A RELIEF TO ACTUALLY
SEE THAT IT WORKED

BECAUSE I CAME TO THAT POINT

WHERE I WAS LIKE, ARE WE
ACTUALLY GOING TO SPOT ANYTHING?

WE MANAGED TO SPOT
PLANETS GOING

IN FRONT
OF OUR STAR.

HIGH FIVE.
HA HA!

HAWKING: NOW THEY ARE
REALLY ON TO SOMETHING.

SIAN: NOW WE'RE GONNA
TRY NUMBER TWO, OK?

LINDSAY: OK...

HAWKING: WITH EVERY
NEW PLANET THEY TRY,

THE STARLIGHT DIMS
TO A DIFFERENT DEGREE.

CAN THE VOLUNTEERS WORK OUT
WHY THIS EFFECT IS SO IMPORTANT?

NOW LET'S TRY
PLANET NUMBER THREE.

WILL: WELL,
A TINY BIT FURTHER.

DEPENDING ON THE SIZE
OF THE PLANET,

YOU'LL GET A BIGGER DEFLECTION.

OK.
SIAN: THERE IT GOES.

THERE IT GOES.

SIAN, VOICE-OVER:
AND SO YOU CAN START

TO GET INTO DETERMINING SIZE
POTENTIALLY OF THE PLANETS

ORBITING STARS
FAR OFF IN THE MILKY WAY.

IT MEANS THAT WE'RE GETTING
SO MUCH CLOSER

TO THE POSSIBILITY
OF FINDING INTELLIGENT LIFE

BECAUSE WE KNOW WHERE TO LOOK.

AND, I MEAN, WHEN YOU'RE
DEALING WITH 300 BILLION STARS,

YOU KNOW, YOU GOT TO KNOW
WHERE TO LOOK.

HAWKING: BY GRASPING HOW
TO DETECT ALIEN WORLDS,

MY VOLUNTEERS
HAVE TAKEN THE NEXT STEP

TOWARD ANSWERING
THE QUESTION "ARE WE ALONE?"

SCIENTISTS USE THE SAME
METHOD TO HUNT FOR SOLAR SYSTEMS

LIKE OUR OWN
THROUGHOUT OUR GALAXY,

ONLY THEY USE MORE
SOPHISTICATED INSTRUMENTS.

CHARBONNEAU:
WHAT WE NEEDED TO DO WAS

TO GET ABOVE
THE EARTH'S ATMOSPHERE

WITH A LARGE TELESCOPE IN SPACE.

THAT TELESCOPE WAS TO BECOME
THE NASA KEPLER MISSION.

HAWKING: THE KEPLER TELESCOPE
SIMULTANEOUSLY MEASURES

THE BRIGHTNESS OF 100,000 STARS.

ITS OBJECTIVE IS
TO SEEK OUT SOLAR SYSTEMS

WITH SMALL ROCKY PLANETS,
LIKE EARTH.

AND ITS RESULTS ARE ASTONISHING.

CHARBONNEAU: WE COULD SEE,
UNAMBIGUOUSLY, DOZENS OF PLANETS

IN THE KEPLER DATA.

AND THEN WITH EACH NEW DOWNLOAD
FROM THE SPACECRAFT,

MORE PLANETS POURED IN.

CURRENTLY THE TALLY
STANDS AT 4,000.

WE'VE LEARNED THAT WHEN WE LOOK
OUT AT STARS IN THE NIGHT SKY,

WE ARE LOOKING AT BROTHERS
AND SISTERS--

OTHER SYSTEMS OF PLANETS

THAT ONE DAY WE MIGHT
HOPE TO INTERACT WITH.

MAYBE WE LIVE
IN THE "STAR TREK" UNIVERSE,

WHERE EVERY SINGLE STAR
HOSTS A SYSTEM OF PLANETS

WITH DIFFERENT CIVILIZATIONS
FOR US TO GO AND EXPLORE.

HAWKING: YET WHAT KEPLER
HAS DISCOVERED SO FAR IS

ONLY PART OF THE STORY.

KEPLER CAN ONLY DETECT PLANETS

THAT COME DIRECTLY BETWEEN
IT AND THE STAR THEY ORBIT.

SO THERE MUST BE
MANY MORE PLANETS

OUTSIDE KEPLER'S
DIRECT LINE OF SIGHT.

WHAT'S MORE, ITS FIELD OF VIEW

IS JUST 1/4 OF ONE PERCENT
OF THE SKY.

SO SCIENTISTS EXTRAPOLATED

KEPLER'S DATA
FOR THE ENTIRE GALAXY.

THEIR CALCULATIONS REVEALED
AT LEAST 100 BILLION PLANETS...

OF WHICH, 50 BILLION
ARE LIKELY TO BE ROCKY WORLDS

IN SOME WAY SIMILAR TO OUR OWN.

SIAN: I FIND ALL OF
THESE NUMBERS FASCINATING

BECAUSE IT--THEY'RE SO LARGE,

LARGER THAN I
WOULD HAVE EVER IMAGINED.

IF YOU HAVE IN THE GALAXY
ABOUT 50 BILLIONS MORE CHANCE

TO HAVE IT HAPPEN,
WE CAN'T BE THE ONLY ONE.

ARE WE REALLY
THAT SPECIAL, RIGHT,

OUT OF THE 50 BILLION
ROCKY PLANETS?

TO ME THAT JUST GIVES
ME ENOUGH HOPE TO SAY,

YEAH, IT'S OUT THERE.

HAWKING: IN THE SEARCH
FOR EXTRATERRESTRIAL LIFE,

SCIENTISTS HAVE DISCOVERED

THAT ROCKY PLANETS ARE
A COMMON FEATURE OF OUR GALAXY.

THEIR NEXT STEP IS TO CONSIDER

WHAT COULD MAKE SOME OF
THESE PLANETS SUITABLE FOR LIFE.

WELL, OF COURSE, ON THIS PLANET,

LIFE MOST ASSUREDLY GOT
STARTED IN A WATERY ENVIRONMENT.

WATER'S THE ESSENTIAL LIQUID.

WATER HAS CERTAIN
ADVANTAGES.

TO BEGIN WITH, THERE'S A LOT
OF WATER ALL OVER THE PLACE.

HYDROGEN IS THE MOST
ABUNDANT ELEMENT IN THE COSMOS.

THE THIRD MOST ABUNDANT
ELEMENT IN THE COSMOS IS OXYGEN.

HYDROGEN, OXYGEN: H2O.

THE OTHER ADVANTAGE OF WATER
IS THAT IT'S LIQUID

OVER A VERY WIDE RANGE
OF TEMPERATURES...

AND CAN INTERACT
WITH OTHER MOLECULES

IN WAYS
THAT FACILITATE CHEMISTRY.

[THUNDER]

HAWKING: LIFE AS WE KNOW IT

NEEDS WATER TO BE
IN ITS LIQUID FORM.

THIS MEANS
WE CAN NARROW OUR SEARCH

FOR HABITABLE PLANETS
STILL FURTHER.

THE DISTANCE FROM A ROCKY
PLANET'S ORBIT FROM ITS STAR

IS CRITICAL TO WHETHER
THERE CAN BE LIQUID WATER.

TOO CLOSE TO ITS HEAT SOURCE

AND ANY WATER WOULD BOIL
INTO STEAM AND LIKELY DISAPPEAR.

TOO FAR AWAY,
AND IT WOULD FREEZE INTO ICE.

BUT IN BETWEEN,
THE PLANET'S TEMPERATURE

WOULD BE JUST RIGHT...

RATHER LIKE THE PORRIDGE
IN THE STORY OF THE THREE BEARS.

SO SCIENTISTS NAME
THIS HABITABLE REGION

THE GOLDILOCKS ZONE.

SCIENTISTS NOW ESTIMATE
THERE COULD BE

AROUND 500 MILLION ROCKY PLANETS
WITH LIQUID WATER

IN GOLDILOCKS ZONES.

IT'S VERY SIMPLE.

UH, IF YOU HAVE A PLANET THERE,

THEN IT COULD HAVE
LIQUID OCEANS, RIGHT?

SO IN OTHER WORDS,
IT'S CONCEIVABLE

THAT THERE'S SOME LIFE THERE

SIMPLY ON THE BASIS OF THE
AVAILABILITY OF LIQUID WATER.

HAWKING: FOR MANY YEARS,
SCIENTISTS BELIEVED

GOLDILOCKS ZONES WERE THE ONLY
PLACE WITH LIQUID WATER

AND SO THE ONLY PLACE
WORTH LOOKING FOR ALIENS.

BUT A RECENT DISCOVERY
POINTS TO THERE BEING

AN ALTERNATIVE SOURCE
OF ENERGY FOR LIFE,

A SOURCE FROM
DEEP WITHIN CELESTIAL BODIES.

IT'S A CONCEPT
I HOPE MY VOLUNTEERS CAN GRASP

IN THEIR NEXT CHALLENGE.

I HAVE GIVEN THEM
AN IRON BAR AND SOME ICE CUBES.

CAN THEY WORK OUT HOW LIQUID
WATER COULD BE PRESENT,

FAR FROM ANY STAR?

SIAN: OHH.
OH, MY GOD.

WHAT HAVE WE
GOT GOING ON HERE?

LINDSAY: OK. OH, WOW.

SIAN, VOICE-OVER:
AND I'M THINKING,

WHAT THE HECK CAN
WE DO WITH THIS?

LINDSAY: WHAT IS THIS THING?

LINDSAY, VOICE-OVER:
AND THE CHALLENGE IS TO GENERATE

HEAT WITHOUT A HEAT--
HEAT SOURCE.

WILL: SO WE KNOW WE
HAVE TO MELT THAT.

WE HAVE TO GO FROM ICE TO WATER.

HOW DO WE HEAT UP THE ICE
WITHOUT A HEAT SOURCE?

SIAN: WELL WE CAN GENERATE
OUR OWN HEAT. RIGHT?

PROBABLY WE HAVE
TO USE OUR HANDS TO CREATE

SOME SORT OF MECHANICAL FORCE,

KINETIC ENERGY TO BE
TRANSFORMED INTO HEAT.

LINDSAY: I THINK WE NEED
TO RUB THIS ROD--AND

TO HEAT IT UP AND THEN
PUT THE ROD IN THERE.

BUT THE WHOLE IDEA IS ENERGY.

YOU NEED A SOURCE OF ENERGY.

I MEAN, IF YOU WANT
TO RUB IT, I THINK IT'LL

BE EASIER TO RUB IT
AGAINST THE OTHER METAL.

YEAH.

FIRST OF ALL,
IT WAS THAT PROCESS

OF, WELL, COULD WE USE FRICTION?

SIAN: KEEP GOING.

WILL: LET'S TRY IT.
TRY--TRY

TO PUT--PUT
THE ICE CUBE ON.

LINDSAY: OK.
SO THAT--OH, YEAH.

LINDSAY: OK.

THE PROBLEM WE HAVE
AT THAT MOMENT THAT WE'RE

NOT GENERATING ENOUGH HEAT
TO MELT THE ICE PROPERLY.

SIAN: IF WE TRY TO FLEX
THE IRON UP AND DOWN--

BUT WAIT. IT HAS
TO BE REALLY TIGHT.

YEAH. AND THEN WE'LL
GENERATE HEAT.

SO THE NEXT STEP WAS JUST TO
ACTUALLY TWIST IT AND BEND IT.

SIAN: SO WE'RE TRYING
TO GET THIS AREA TO HEAT UP.

I DIDN'T THINK, ONCE AGAIN, THAT
WE WOULD GENERATE ENOUGH ENERGY.

SIAN: AND THEN...

BY GOING BACK AND FORTH...

OH, MY GOD.
WHOA!

IT'S ACTUALLY STARTING
TO BREAK AND BEND...

OH, MY GOD. WOW!
AND WEAKEN...

OH, MY GOD.

ACTUALLY GENERATE
MAYBE ENOUGH HEAT.

WOW.

OH, MY GOD. YOU GUYS ARE
GOING TO HAVE TO HELP ME.

THAT'S AMAZING!
OH, MY GOD.

SIAN: OK, WE'RE GOING
TO ROTATE IN AND OUT.

YOU'RE ACTUALLY
BREAKING IT...

THE NEXT PERSON
READY TO GO?

WILL: UH, IN TWO SECONDS,
YOU HAVE ANOTHER 10 SECONDS.

KEEP GOING.
SIAN: ALL RIGHT.

SOMETIMES, YOU KNOW, YOU JUST
GOT TO SIT BACK AND SUPERVISE...

SIAN: IT'S GETTING HOT.
KEEP GOING, FURTHER.

AND MOTIVATE.

OH, YEAH.
KEEP GOING, KEEP GOING.

AND I FEEL LIKE
I'M A GOOD MOTIVATOR.

I KNOW IT'S TOUGH. JUST
KEEP CONCENTRATING ON IT.

YEAH! KEEP GOING. KEEP GOING.

BACK AND FORTH, BACK AND FORTH.

WILL: NEED TO
PUT THE ICE ON.

LINDSAY: WOW.

BUT I WAS
WATCHING THAT IRON BEND.

HAWKING: THE ALTERNATING
STRETCHING AND COMPRESSION

PRODUCES INTERNAL FRICTION
AND HEAT INSIDE THE ROD.

KEEP GOING. KEEP GOING.
YOU'RE STARTING TO GET IT.

YOU'RE STARTING
TO GENERATE IT.

AND IT WAS GETTING HOT.

HAWKING: BUT CAN THEY GENERATE
ENOUGH HEAT TO MELT THE ICE?

SIAN: KEEP GOING. ALL RIGHT.
LOOK OUT, LOOK OUT, LOOK OUT.

LINDSAY: ALL RIGHT.
LET'S TRY THE ICE.

LINDSAY AND SIAN: OH, WOW.

LINDSAY: NICE.

SIAN: OH, HO HO!
THAT'S AWESOME.

LOOK AT THAT GO.

THIS IS COOL. LIKE, WHEW!

SIAN: THAT IS FANTASTIC. HA HA!

GOOD JOB, YOU GUYS.

LINDSAY: GOOD JOB.

SIAN: HA HA!

I DIDN'T EXPECT, UM,
THAT MUCH HEAT, YOU KNOW.

UM, ACTUALLY IT WAS STEAMING,
SO IT WAS VERY AMAZING.

HAWKING: HAVE MY VOLUNTEERS
GRASPED WHY SCIENTISTS

NOW THINK LIFE COULD EXIST FAR
FROM THE HEAT SOURCE OF STARS?

LINDSAY: YOU KNOW, WHEN
WE'RE LOOKING FOR LIFE,

WE'RE LOOKING FOR THE
PLANETS SURROUNDING A STAR,

BECAUSE WE NEED
A HEAT SOURCE.

AND THE HEAT COMES
FROM THE STAR,

BUT IT SEEMS LIKE THE HEAT
THAT MIGHT BE NEEDED

FO--FOR LIFE CAN ALSO BE
FROM MECHANICAL FORCES.

HAWKING: THIS IS
A PROCESS SCIENTISTS THINK

IS HAPPENING RIGHT NOW
IN OUR OWN SOLAR SYSTEM.

484 MILLION MILES FROM OUR SUN
IS THE MAGNIFICENT GAS GIANT,

THE PLANET JUPITER.

IT HAS 67 MOONS.

ONE OF THEM, EUROPA, IS
ABOUT THE SIZE OF OUR OWN MOON,

BUT IT'S A VERY DIFFERENT PLACE.

CHARBONNEAU: THE SURFACE
OF EUROPA IS

A BONE-CHILLING
MINUS 150 DEGREES CENTIGRADE.

WE KNOW THAT EUROPA HAS
A LOT OF WATER,

BUT EUROPA IS SO FAR
FROM THE SUN,

THERE'S NO QUESTION
THAT THE WATER IS

ABSOLUTELY ROCK SOLID
AND NOT A GOOD PLACE FOR LIFE.

HAWKING: BUT EUROPA DOES NOT
BEHAVE AS YOU'D EXPECT

BECAUSE ITS ORBIT AROUND
JUPITER ISN'T A PERFECT CIRCLE.

INSTEAD, IT HAS
AN ELLIPTICAL PATH.

CHARBONNEAU: AS A RESULT,
THAT SLIGHTLY ELLIPTICAL ORBIT--

ABOUT A 1% DEVIATION
FROM A PERFECT CIRCLE--

MEANS THAT EUROPA'S
DISTANCE FROM JUPITER

CHANGES AS IT GOES
AROUND IN ITS ORBIT,

SOMETIMES SLIGHTLY FARTHER AWAY

AND SOMETIMES
EVER SO SLIGHTLY CLOSER.

HAWKING: THIS MEANS THE STRENGTH
OF JUPITER'S GRAVITATIONAL PULL

ON EUROPA CHANGES, TOO.

AND THAT MAKES THE ENTIRE
MOON STRETCH

ONE WAY AND THEN THE OTHER.

CHARBONNEAU: THAT CONSTANT
STRETCHING AND SQUISHING

AND STRETCHING
AND SQUISHING

HEATS THE INSIDE OF EUROPA

AND ALLOWS THE ICE OUT
OF WHICH EUROPA IS MADE TO MELT.

WHAT EUROPA TELLS US IS THERE'S
ANOTHER WAY TO HEAT A PLANET,

TO KEEP THE WATER LIQUID,

AND ULTIMATELY TO PROVIDE
A HABITABLE ENVIRONMENT

WHERE LIFE MIGHT THRIVE.

HAWKING:
NASA IS PROPOSING A MISSION

TO EXPLORE
THIS MYSTERIOUS WORLD.

I THINK THEY MAY FIND
AN ENTIRE ECOSYSTEM,

LIKE THE DEEP SEA ECOSYSTEMS
WE HAVE HERE ON EARTH.

THAT WOULD BE TRULY AMAZING.

WITH A VAST NUMBER OF
WATERY ROCKY WORLDS TO CONSIDER,

IT IS LIKELY THERE
ARE COUNTLESS PLACES

WHERE WATER-BASED LIFE COULD
BE THRIVING AT THIS VERY MOMENT.

AND WITH NEW DISCOVERIES,
LIKE WATER ON MARS AND PLUTO,

I BELIEVE WE WILL ENCOUNTER
ALIEN ORGANISMS IN OUR LIFETIME.

THE MATHEMATICS PREDICTS IT.

LIFE IS UNDOUBTEDLY OUT THERE.

NOW HERE'S A PROSPECT
I FIND EVEN MORE TANTALIZING.

GIVEN THAT OUR GALAXY
IS OVER 13 BILLION YEARS OLD,

THERE HAS BEEN AMPLE
TIME FOR SIMPLE LIFE TO EVOLVE

INTO COMPLEX ORGANISMS

AND PERHAPS
INTO INTELLIGENT CIVILIZATIONS

JUST AS WE HAVE ON EARTH.

AND IF ADVANCED LIFE HAS EVOLVED

ON ONLY A TINY PERCENTAGE
OF THESE PLANETS,

THERE MIGHT STILL BE A GOOD
NUMBER OF ALIEN CIVILIZATIONS

IN OUR GALAXY,

WITH THE TECHNOLOGY
TO COMMUNICATE WITH US.

MAYBE SOME ARE ALREADY TRYING.

TO FIND OUT, ALL THE SCIENTISTS
HAVE TO DO IS LISTEN.

BUT THIS ISN'T
AS STRAIGHTFORWARD

AS IT FIRST SEEMS.

I HAVE SENT MY VOLUNTEERS
TO WHERE SCIENTISTS PROBE

FOR SIGNALS FROM DEEP SPACE.

OH, MY GOD!

LINDSAY: WOW!
THIS IS AMAZING.

SIAN: THIS IS
UN-FREAKIN'-BELIEVABLE.

LINDSAY: THAT IS CRAZY.

[SIAN LAUGHING]

SIAN: THIS--
THIS FOR ME IS

A SIGN OF INTELLIGENT
LIFE RIGHT HERE--

WITH ADVANCED
TECHNOLOGY.

HAWKING: NOW LET'S FIND OUT
WHAT ASTRONOMERS ARE PICKING UP

AND HOW IT MAY HELP THEM

TRACK DOWN INTELLIGENT
EXTRATERRESTRIALS.

LINDSAY: OH, WOW...

SIAN: THIS IS COOL.

WILL: I'M GONNA
PLAY WITH THAT.

HOW ABOUT THIS ONE...

SIAN: OH, LOOK AT THIS.
WAIT.

[HISSING STATIC-LIKE SOUND]

LISTEN TO THAT.

SIAN: WE SEE THIS WAVE
GOING ACROSS THE SCREEN,

BUT NOT ONLY THAT.

YOU CAN HEAR THE SOUND.

LIKE, YOU KNOW, WEIRD
KIND OF--

[IMITATES UNDULATING NOISE]

YOU KNOW?

WILL: I WAS THINKING
THAT THIS SIGNAL

THAT WE TAKE FROM THE DISH,
IS WHAT WE SEE HERE.

HAWKING: THAT'S RIGHT.

WHEREVER THIS RADIO
TELESCOPE POINTS,

IT RECEIVES ELECTROMAGNETIC
VIBRATIONS FROM SPACE.

BECAUSE DISTANT STARS
AND PLANETS--

IN FACT,
EVERYTHING IN OUR GALAXY--

EMITS RADIO WAVES

ALL AT ONCE AND ALL THE TIME.

HAWKING: THIS WHITE NOISE IS

THE COMBINED SOUND
OF THE UNIVERSE,

CONVERTED INTO SOMETHING THAT
WE CAN HEAR WITH OUR OWN EARS.

AND SOMEWHERE IN THERE MAY BE
A MESSAGE FROM INTELLIGENT LIFE.

SO IN THE SEARCH
FOR EXTRATERRESTRIAL LIFE,

WE FACE A PROBLEM.

HOW IS IT POSSIBLE
TO HEAR AN ALIEN BROADCAST

AMONG SO MUCH BACKGROUND NOISE?

WILL: ALL RIGHT.

SIAN: OH, MY GOD.
THAT'S AWESOME.

LINDSAY: OH, OK.
WOW. GREAT.

HAWKING: WITH
THE EQUIPMENT I'VE LAID OUT,

CAN MY VOLUNTEERS WORK OUT
THE SOLUTION?

SIAN, VOICE-OVER:
IT'S AN INTERESTING CHALLENGE

BECAUSE SPACE IS NOISY.

AND IF SOMEBODY OUT THERE
IS INTELLIGENT

AND BROADCASTING TO US,
HOW ARE WE GOING TO HEAR THEM?

HOW ARE WE GOING TO FIND THEM?

LINDSAY:
THIS LOOKS FAMILIAR.

WE KNOW ALREADY THAT'S--THAT'S
SPACE WHITE NOISE.

WE'RE LISTENING TO SPACE.

LINDSAY:
THE WHITE NOISE IS COMING

FROM THESE SPEAKERS
SURROUNDING US.

SIAN: IT LOOKS LIKE WE
HAVE AN EQUALIZER HERE.

WILL: YEAH. DO YOU THINK
WE CAN MIX--LIKE, MIX OUT

AND TRY TO FIGURE OUT
WHAT WE WANT TO HEAR?

HAWKING: THE VOLUME OF
THE WHITE NOISE IS FIXED.

SO USING THE EQUALIZER
AND MEGAPHONE ALONE,

HOW WILL MY VOLUNTEERS
GO ABOUT SIMULATING A MESSAGE

FROM DEEP SPACE?

SIAN: YOU'RE GONNA BE
INTELLIGENT LIFE...

WILL: YEAH.
OF THE UNIVERSE.

I LIKE THAT.

WE MADE WILL AN ALIEN,

AND HIS JOB WAS
TO BROADCAST AS AN ALIEN.

SIAN: GO, WILL. GO!

SO THEY SEND ME TO BE THIS
TEST ALIEN SOMEWHERE IN SPACE.

SO WE WANT TO SEE
IF WE CAN HEAR

WILL...
YEAH.

WHO IS OUR ALIEN
IN DEEP SPACE.

LINDSAY: RIGHT.
AND SO...

BUT THE BIG PROBLEM
IS IT'S SO NOISY OVER HERE

THAT EVEN IF THERE IS
AN INTELLIGENT SIGNAL,

WE WOULDN'T BE
ABLE TO PICK IT UP.

WE'RE DROWNED IN THIS NOISE.

WILL: I AM AN ALIEN.

SIAN: I CAN'T HEAR HIM.

I AM AN ALIEN.

SIAN: WHAT CAN WE DO?
IF WE HAVE THIS HERE...

I AM AN ALIEN.

HE WAS CREATING
ARTIFICIAL NOISE.

I AM AN ALIEN.

WE--WE CAN'T HEAR ANYTHING,

THOUGH HE
WAS SHOUTING AT US.

I AM AN ALIEN.

I AM AN ALIEN.
I AM...

HAWKING: THE CHALLENGE
OF DETECTING ALIEN BROADCASTS

WAS CONSIDERED BY
SCIENTISTS BACK IN THE 1950s.

GIUSEPPE COCCONI
AND PHILIP MORRISON PROPOSED

THAT INTELLIGENT
ALIENS WOULD MAKE USE

OF ONE PECULIAR FEATURE
OF THE UNIVERSE.

THERE IS ONE BAND OF FREQUENCIES

WHERE THERE ARE
VERY FEW VIBRATIONS,

AND SO IT IS EERILY QUIET.

AND WITHIN THIS BAND
IS A UNIQUE FREQUENCY

THAT IS IDEAL
FOR LONG-DISTANCE COMMUNICATION.

SETH SHOSTACK: THERE'S
A CERTAIN FREQUENCY

CALLED
THE HYDROGEN LINE FREQUENCY.

IT'S AT 1,420 MEGAHERTZ.

THAT'S WAY ABOVE
TELEVISION/RADIO.

AND THAT FREQUENCY IS ONE THAT'S
VERY IMPORTANT FOR ASTRONOMY.

HAWKING:
BECAUSE THIS FREQUENCY BELONGS

TO THE MOST COMMON ELEMENT
IN THE UNIVERSE, HYDROGEN,

SCIENTISTS FIGURED
ALIEN ASTRONOMERS

WOULD UNDOUBTEDLY
BE AWARE OF IT.

SHOSTACK: TUNING TO THIS
MAGIC FREQUENCY, IF YOU WILL.

WELL, THAT MAKES SENSE
BECAUSE, YOU KNOW,

THEY WILL KNOW THAT FREQUENCY.

AND IF THEY'RE DELIBERATELY
TRYING TO GET IN TOUCH,

MAYBE THEY'LL USE IT.

[OVERLAPPING TRANSMISSIONS]

HAWKING: COCCONI
AND MORRISON SUGGESTED

THAT THIS QUIET SPOT
ON THE RADIO DIAL WOULD BE

THE IDEAL FREQUENCY FOR ALIEN
CIVILIZATIONS TO COMMUNICATE ON.

WILL THE VOLUNTEERS REALIZE

THEY HAVE
TO CREATE THEIR OWN VERSION

OF THE GALAXY'S
QUIET FREQUENCY BAND?

SIAN: NO, NO. THIS IS,
UH, AMPLIFYING IT.

IT'S BRINGING IT DOWN.

I AM AN ALIEN.

WE'VE GOT ALL
THESE FREQUENCIES,

AND HE'S BROADCASTING
ON JUST A SHORT FEW.

HE'S BROADCASTING IN
A NARROW BAND OF FREQUENCIES.

WE FIGURED OUT THAT IF
WE COULD ELIMINATE THE SIGNALS

FROM THE BACKGROUND NOISE,
THEN WE COULD HEAR HIM.

YEAH. IF WE CAN FIGURE
OUT WHAT THAT IS,

THEN WE
CAN ISOLATE IT.

JE SUIS UN EXTRATERRESTRE.

SIAN: HERE.
GET THESE ONES DOWN.

WILL: I AM AN ALIEN.

SIAN: SO WE CAN EITHER
BOOST SIGNALS.

I AM AN ALIEN.
OOH.

I'M STARTING
TO HEAR HIM.

I'M ACTUALLY STARTING
TO HEAR HIM.

I AM AN ALIEN.

WILL, VOICE-OVER:
EVENTUALLY THEY MANAGED

TO PICK THE FREQUENCY I WAS ON

BY LOWERING THE WHITE NOISE
ON THIS SPECIAL FREQUENCY.

THEY MANAGED TO ISOLATE
MY VOICE FROM THE NOISE.

I AM AN ALIEN...

SIAN: I CAN HEAR
HIM. OH, MY GOD.

YEAH.
WILL: I AM AN ALIEN.

NOW WE CAN HEAR HIM.

I CAN
TOTALLY HEAR HIM.

HAWKING: NOW CAN THEY MAKE THE
SAME CONNECTION SCIENTISTS MADE?

IF YOU'RE
AN INTELLIGENT SPECIES,

YOU ACTUALLY WILL CHOOSE
TO BROADCAST, "HEY, WE'RE HERE,"

YOU KNOW, IN A FREQUENCY
THAT'S LESS NOISY

SO THAT THE OTHER
INTELLIGENT LIFE

WOULD ACTUALLY
FIND YOU AND HEAR YOU.

HE'S SAYING,
"I AM AN ALIEN."

RIGHT!

CAN YOU HEAR ME?

SIAN: I CAN HEAR
INTELLIGENT LIFE OUT THERE.

WILL: I AM AN ALIEN.

THAT IS SO AWESOME.

WILL: I AM AN ALIEN.

HAWKING: ASTRONOMERS HAVE
BEEN LISTENING FOR ALIEN SIGNALS

FOR REAL ON THE SWEET SPOT OF
THE COSMIC DIAL FOR 30 YEARS.

SHOSTACK: FOR A LOT OF PEOPLE,

THE OBVIOUS WAY TO FIND
THE ALIENS IS JUST GO LOOK.

I MEAN, THAT'S WHAT THEY
DO ON "STAR TREK," RIGHT?

THEY BOLDLY GO OUT INTO SPACE

WITH A REALLY
HIGH-POWERED CRAFT,

AND THEY JUST LOOK FOR THEM.

WELL, I MEAN, THAT--THAT MAY BE
MORE INTERESTING FOR TELEVISION,

BUT THIS IS ACTUALLY
FAR MORE PRACTICAL.

HAWKING:
IT'S A PROJECT CALLED SETI--

THE SEARCH FOR
EXTRATERRESTRIAL INTELLIGENCE.

SHOSTACK: THE TOTAL NUMBER
OF STAR SYSTEMS

THAT WE'VE LOOKED AT
CAREFULLY IS A FEW THOUSAND.

SO, YOU KNOW,
IT'S VERY EARLY DAYS.

WE'VE JUST SCRATCHED
THE SURFACE.

THERE COULD BE SIGNALS
GOING THROUGH MY BODY

AS I STAND HERE RIGHT NOW.

AND IF ONLY WE HAD THESE
ANTENNAS POINTED THE RIGHT WAY,

I'D FLY TO STOCKHOLM IN A WEEK
AND COLLECT THE NOBEL PRIZE.

HAWKING: YET IN 3 DECADES
OF SCANNING THE GALAXY,

SCIENTISTS HAVE HEARD NOTHING.

IT HIGHLIGHTS A PARADOX REVEALED
BY PHYSICIST ENRICO FERMI,

WHEN HE ASKED,
"WHERE IS EVERYBODY?"

FERMI WAS TALKING
ABOUT A CONTRADICTION--

THE LARGE NUMBER
OF ALIEN CIVILIZATIONS

THE MATHEMATICS PREDICTS

AND THE LACK OF EVIDENCE
OF THOSE CIVILIZATIONS.

FERMI BELIEVED ASTRONOMERS
OUGHT TO HAVE MADE CONTACT

LONG AGO AND MANY TIMES OVER.

BUT BECAUSE WE DON'T SEEM
TO HAVE BEEN VISITED BY ALIENS,

PERHAPS THERE IS A PROBLEM THAT
SCIENTISTS HADN'T CONSIDERED.

TO GET MY VOLUNTEERS
THINKING ABOUT THIS PARADOX,

HERE IS A SPECIAL MACHINE.

SIAN: OH, MY GOODNESS.

HAWKING: ITS DESIGN REFLECTS
THE JOURNEY

WE'VE TAKEN TO WORK OUT
THE PROBABILITY OF ALIEN LIFE.

IT'S A DEMONSTRATION
OF A PRINCIPLE

CALLED THE GREAT FILTER.

CAN THEY FIGURE OUT
WHAT IT REPRESENTS?

[MUSIC PLAYING ON SOUNDTRACK]

I'M LOOKING AT THIS CONTRAPTION,

AND THEN I'M LIKE, "WILL,
PUT THE BUCKET OF BALLS IN,"

YOU KNOW?

"LET'S SEE WHAT GOES ON."

AND THEN I'M LIKE,
I'M SWITCHING SWITCHES.

SIAN: ONE...

WILL: OH!

SIAN: MY GOD,
THAT'S AWESOME.

WILL: HOW NICE!

LOOK AT THAT.

LINDSAY: WHAT?
OK, NUMBER TWO.

A GOOD AMOUNT OF BALLS
WOULD GO FROM THE FIRST COLUMN

TO THE SECOND ONE.

FROM ONE TO TWO,
EH, IT'S EASY.

FROM TWO TO THREE,
HMM, NOT SO EASY.

LINDSAY: OH, RIGHT! YES!

SIAN: OH, WE
DID IT? YEAH!

SIAN, VOICE-OVER: VERY FEW
ARE MAKING IT IN--INTO THREE.

AND NONE AT THIS POINT
ARE MAKING IT INTO FOUR.

WHEN YOU GO CLOSER
AND YOU INSPECT IT,

YOU'RE LIKE, "WAIT.
WHAT'S GOING ON HERE?"

TO ME THAT MACHINE
LOOKS LIKE, YOU KNOW,

IT COULD BE AN ANALOGY
FOR A NUMBER OF THINGS.

WE'RE JUST KIND OF THROWING
OUT DIFFERENT HYPOTHESIS.

WILL: I FEEL WE'VE MADE THEM

MORE LIKE,
THAT'S ALL YOUR PLANETS.

AND THEN THEY HAVE
TO MEET CRITERIA TO GET LIFE.

LINDSAY: SO THERE--YOU'RE SAYING
THERE ARE A LOT OF CRITERIA

THAT NEEDS TO BE MET
BEFORE LIFE HAPPENS

AND THEN MORE CRITERIA
FOR LIFE TO BE INTELLIGENT.

AND SO THIS IS LIKE THE...

WILL: I THINK SO.
YEAH.

THE DIFFERENT PROCESS,
AND IT GETS RARER AND RARER.

LINDSAY, VOICE-OVER:
THERE ARE OBVIOUS BARRIERS,

UM, TO THE EVOLUTION OF LIFE.

AND, YOU KNOW,
THAT SEEMS KIND OF FITTING.

HAWKING: THEY'VE GOT IT.

AND THESE BARRIERS SEPARATE

THE PARTS OF
MY GREAT FILTER MACHINE.

THE WINDOWS IN THE BARRIERS
GET SMALLER,

SO IT BECOMES HARDER
TO PROGRESS THROUGH THE MACHINE.

THE BALLS IN
THE FIRST COMPARTMENT REPRESENT

THE NUMBER OF ROCKY PLANETS
ORBITING STARS IN OUR GALAXY.

IN THE SECOND ARE THOSE
ROCKY PLANETS WITH LIQUID WATER,

WHICH HAVE DEVELOPED
SIMPLE LIFE.

IN THE THIRD ARE SPECIES
ON THOSE PLANETS

THAT HAVE FURTHER EVOLVED
INTO COMPLEX LIFE FORMS.

AND THE FEW BALLS THAT HAVE
MADE IT TO THE LAST COMPARTMENT

REPRESENT INTELLIGENT LIFE THAT
HASN'T YET DEVELOPED TECHNOLOGY.

BUT THERE IS
ONE FINAL STAGE REMAINING--

MAKING IT OUT OF
THE COMPARTMENTS ALTOGETHER.

LINDSAY, VOICE-OVER: IT HAS
THIS SPIRAL THING DOWN.

AND EVENTUALLY, BOOM.

OHH. LOOK AT THAT.
OH, MY GOSH!

LINDSAY, VOICE-OVER: FINALLY,
WE WERE VERY EXCITED TO SEE

THAT THERE WAS ONE BALL
THAT MADE IT, YOU KNOW,

OUT THAT--THAT TUBE THING.

COMES DOWN, SLIDES DOWN.

HAWKING: THIS REPRESENTS
INTELLIGENT BEINGS

WHO HAVE DEVELOPED TECHNOLOGIES

FOR COMMUNICATING
WITH OTHER WORLDS.

SO IF THAT BALL
REPRESENTS AN ALIEN LIFE

THAT CAN, UM, HAVE
THE TECHNOLOGY TO COMMUNICATE,

IT IS VERY UNLIKELY

AND VERY HARD
TO GET TO THAT STAGE.

HAWKING: THAT
ALIEN CIVILIZATION'S GOAL IS

TO NOW ACHIEVE FIRST CONTACT

BY GETTING TO THE BOX
AT THE END OF MY MACHINE.

WE WERE ROOTING FOR IT
TO GET TO THE BOX.

SIAN: OH, WELL, COME ON.
COME ON...

STEADY.

COME ON, COME ON.

AND THEN, OH, MY GOD.

AAH! OH, MY GOD!

WHAT THE HECK?

SIAN: OH, MY GOD!

OUR BALL JUST GOT ANNIHILATED.

IT WAS JUST DISAPPOINTING
ALMOST TO THINK

IT'S BEEN THROUGH
THE ENTIRE PROCESS

AND, LAST MINUTE,
IT GETS BLOWN AWAY.

HAWKING: SO WHAT DO THEY
THINK THE FLAME SIGNIFIES?

SIAN: THE FLAME REPRESENTED
THE FACT THAT BY THE TIME

WE GET TO INTELLIGENT LIFE,

THE PLANET OR THE SPECIES
THAT IS INTELLIGENT,

JUST, SOMETHING HAPPENS TO IT.

YOU CAN HAVE INTELLIGENT LIFE.

IT DOESN'T MEAN
IT'S GOING TO SURVIVE.

ANYTHING CAN HAPPEN.

LINDSAY, VOICE-OVER: AND IT
COULD BE NATURAL DISASTERS;

THE PLANET COULD BE HIT
BY AN ASTEROID;

OR IT COULD BE WARS.

OR THERE COULD BE AN EPIDEMIC

OF, YOU KNOW,
DISEASE THAT CAN DESTROY.

SO, YOU KNOW, LIFE IS FRAGILE.

HAWKING: THE GREAT FILTER
THEORY SUGGESTS THERE MAY BE

ONE SIGNIFICANT STUMBLING BLOCK

TO BECOMING AN ADVANCED
EXTRATERRESTRIAL CIVILIZATION--

THAT ADVANCED ALIEN LIFE
OCCURS SO RARELY OR BRIEFLY

THAT WE ARE
UNLIKELY TO MAKE CONTACT.

I, FOR ONE,
AM MORE OPTIMISTIC THAN THAT.

BUT THE IDEA DELIVERS A STARK
WARNING TO OUR OWN CIVILIZATION.

SIAN: I THINK HUMANS ARE

IN A VERY DELICATE
POSITION RIGHT NOW.

THE MACHINE
IS ABSOLUTELY TELLING ME

THAT HUMAN LIFE IS FRAGILE

AND OUR EXISTENCE
AS AN INTELLIGENT SPECIES

IS EXTREMELY FRAGILE.

HAWKING: CONSIDER WHAT
WE'VE ACHIEVED ON OUR JOURNEY.

OUR GALAXY CONTAINS
AROUND 300 BILLION STARS...

SIAN: OH, MY GOD.

LINDSAY: WHOO!

HAWKING: EACH ONE
A POTENTIAL POWERHOUSE

FOR ALIEN WORLDS.

SIAN: I NEVER WOULD
HAVE GOT IT UNTIL I SAW IT.

HAWKING: ORBITING THOSE
STARS ARE 100 BILLION PLANETS,

50 BILLION OF WHICH
COULD BE ROCKY, LIKE OUR OWN.

SIAN: IT'S OFFICIAL.

WE KNOW HOW TO FIND PLANETS
ORBITING STARS FAR AWAY.

HAWKING: WE KNOW
500 MILLION ROCKY WORLDS

COULD HAVE THE VITAL MATERIAL
NEEDED BY LIFE--LIQUID WATER.

SIMPLE LIFE COULD BE THRIVING

ON COUNTLESS NUMBERS OF THESE
WORLDS AT THIS VERY MOMENT.

AND ON SOME
OF THESE, EVOLUTION HAS HAD

THE TIME TO PRODUCE INTELLIGENT,
TECHNOLOGICALLY ADVANCED LIFE.

CAN YOU HEAR ME?

SIAN: I CAN HEAR
INTELLIGENT LIFE OUT THERE.

HAWKING: I BELIEVE
HUMAN BEINGS CANNOT BE

THE SINGULAR ADVANCED SPECIES
IN OUR GALAXY...

THOUGH I THINK
IT QUITE LIKELY THAT WE ARE

THE ONLY CIVILIZATION
AT OUR STAGE OF DEVELOPMENT

WITHIN
SEVERAL HUNDRED LIGHT YEARS.

SIAN: OH!

WILL: IT MADE IT.
IT MADE IT.

LINDSAY: OH, MY GOD!

HAWKING: SO IF I WERE YOU,
I WOULDN'T LOSE TOO MUCH SLEEP

WORRYING ABOUT
BEING ABDUCTED BY ALIENS.

OUR JOURNEY HAS CERTAINLY THROWN
UP SOME PRETTY BIG THOUGHTS.

SIAN: THIS JOURNEY ENABLED
ME TO GO DEEPER, UM, TO--

TO COME TO REALIZATIONS
THAT I DIDN'T HAVE BEFORE.

WILL: I DO HOPE WE'LL DISCOVER

LIFE SOMEWHERE ELSE

AND THAT WE'LL LEARN
NEW THINGS FROM THAT.

I WON'T LOOK AT THE SKY IN
THE SAME WAY. THAT'S FOR SURE.

LINDSAY: THERE'S A SAYING
THAT EVERY JOURNEY LEADS YOU

BACK TO WHERE YOU START.

WHEN WE SEARCH OUTSIDE,
WE OFTEN FIND SOMETHING ABOUT

OUR--OURSELVES.

HAWKING: NOW, HAVING
SO FAR EXPLORED THE POSSIBILITY

FOR LIFE
IN OUR COSMIC NEIGHBORHOOD--

THE MILKY WAY--WE CAN TURN
AGAIN TO OUR GRAND QUESTION:

"ARE WE ALONE IN THE UNIVERSE?"

CONSIDER THIS.

THE UNIVERSE
AT ITS GRANDER SCALE IS

A MAELSTROM OF GALAXIES.

SCIENTISTS ESTIMATE
THAT THERE MAY BE

MORE THAN 200 BILLION IN NUMBER.

THAT'S PRACTICALLY
A GALAXY IN THE UNIVERSE

FOR EVERY STAR IN OUR GALAXY.

EVEN IF EACH
OF THESE GALAXIES IS HOME

TO JUST ONE TECHNOLOGICALLY
ADVANCED SPECIES LIKE US,

THEN THERE WILL BE
BILLIONS OF POSSIBILITIES

FOR EXTRATERRESTRIAL
CIVILIZATIONS.

AND THE UNIVERSE IS
ABOUNDING WITH INTELLIGENT LIFE.

THE FACT WE CAN
ALL UNDERSTAND THIS IS

A REMARKABLE FEAT
OF THE HUMAN MIND.

SO NOW I HOPE YOU
ARE BEGINNING TO REALIZE

THAT WITH A LITTLE
BIT OF THINKING,

YOU'VE HAD THE GENIUS
TO FIGURE OUT

THAT WE CANNOT BE ALONE.

Hawking: Why are we here?

My name is Stephen Hawking.

Ahjun: Am I an accident,
are we all an accident?

Hawking: I believe that anyone
can answer big questions

for themselves.

Ahjun: We're here simply because
of the choices we made.

Hawking: Follow the greatest
thinkers in history.

Scientist: And in a flash
came to him--

there might be a single law.

Hawking: Think like a genius.

Ahjun: I definitely have free
will. If I was just the brain,

I would be just the brain.

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