NARRATOR: THERE ARE MOMENTS IN ASTRONOMY THAT HAVE TRANSFORMED OUR UNDERSTANDING OF THE SKIES... MARCUS: WHAT HE DISCOVERS ARE THE LAWS OF PLANETARY MOTION.

NARRATOR: FLASHES OF INSPIRATION FROM THE HEAVENS, TURNING POINTS THAT CAUSED A SHIFT IN THE VERY WAY WE THINK ABOUT THE COSMOS.

PLAIT: ONCE YOU COME ALONG AND SAY, "THESE THINGS MOVE IN ELLIPSES," BOOM, THAT'S WHEN THE MODEL WORKED.

NARRATOR: THEY HAVE CHANGED OUR PERCEPTION OF THE EARTH AND OUR PLACE IN THE UNIVERSE.

AMON: THESE STARS WERE AT LEAST 10 TIMES FURTHER AWAY THAN ANY OF THE STARS THAT WE KNEW WERE IN OUR GALAXY.

NARRATOR: OUR IMAGINATIONS CAN NOW RUN WILD... CAMPION: THERE MIGHT BE ALIENS OUT THERE WHO MIGHT ACTUALLY COME AND DEVOUR US.

NARRATOR: IN A UNIVERSE OF ENDLESS POSSIBILITIES.

HAMILTON: ALL OF A SUDDEN, WOW, OUR UNIVERSE MIGHT BE MUCH, MUCH, MUCH LARGER THAN WE ORIGINALLY THOUGHT.

NARRATOR: THIS IS THE STORY OF HUMANKIND'S OBSESSION WITH THE SKIES AND THE WAYS OUR ANCESTORS MADE SENSE OF THE UNIVERSE.

THIS IS THE STORY OF HOW WE MOVED FROM A WORLD RULED BY SUPERNATURAL BEINGS TO A COSMOS REVEALED BY SCIENTIFIC ASTRONOMY.

THIS IS THE STORY OF SEEING OTHER WORLDS AND FINDING OUR TRUE PLACE AMONG THEM.

THIS IS THE STORY OF OUR ANCIENT SKIES.

NARRATOR: OVER THE COURSE OF MILLENNIA, WE SHIFTED FROM A MYTHICAL COSMOS GOVERNED BY SUPERNATURAL BEINGS TO A RATIONAL UNIVERSE WHERE SCIENCE AND MATH RULED SUPREME.

WE SAW OUR FLAT EARTH TRANSFORMED INTO A SPHERE AND IMAGINED IT AT THE CENTER OF EVERYTHING, ORBITED BY THE SUN, MOON, PLANETS, AND ALL THE STARS IN THE SKY.

THEN IN 1543, AN ASTRONOMER NAMED NICOLAUS COPERNICUS PROPOSED THAT THE SUN, NOT THE EARTH, WAS AT THE CENTER OF THE COSMOS.

EVEN IN THIS NEW MODEL, EVERYTHING WAS STILL CONTAINED INSIDE CONCENTRIC, CRYSTALLINE SPHERES, BUT THAT IDEA WAS ABOUT TO COME CRASHING DOWN.

IN 1577, A GREAT COMET PASSED CLOSE TO THE EARTH.

IT STAYED IN THE SKY FOR OVER TWO MONTHS.

CAMPION: THE COMET OF 1577 WAS REMARKABLE IN THAT WE HAVE OBSERVATIONS OF IT FROM AROUND THE WORLD-- FROM PERU, JAPAN, ITALY TURKEY-- AND SO IT'S A MOMENT WHICH WE CAN FIX IN TIME.

NARRATOR: PEOPLE BELIEVED COMETS TO BE GREAT BALLS OF FIRE, AND DIFFERENT CULTURES TOLD STORIES DEPICTING THEM AS DIFFERENT CREATURES.

AUSTRALIAN ABORIGINAL PEOPLES BELIEVED THEM TO BE THE FEARSOME, EVIL SPIRIT OF A RAINBOW SERPENT.

OTHER CULTURES IMAGINED COMETS AS FIRE-BREATHING DRAGONS.

IN MOST CASES, THEY WERE SEEN AS OMENS BRINGING BAD LUCK, BUT THE GREAT COMET OF 1577 WOULD BRING ABOUT ONE OF THE GREATEST TRANSFORMATIONS IN ASTRONOMY FOR 1,400 YEARS.

IN THE KINGDOM OF DENMARK WAS A MAN WHO FELT INSPIRED TO TAKE ASTRONOMY TO GREAT NEW HEIGHTS.

HE WAS A MAVERICK SKY WATCHER WHO WORE A BRASS NOSE AFTER HIS REAL ONE WAS CUT OFF IN A DUEL.

HE LIVED IN A CASTLE AND HAD HIS OWN PERSONAL COURT JESTER.

HIS NAME WAS TYCHO BRAHE.

CAMPION: TYCHO BRAHE WAS THE ASTROLOGER TO THE KING OF DENMARK, AND SO ACCURACY WAS AT A PREMIUM.

NARRATOR: AT THIS TIME, ASTROLOGY AND ASTRONOMY WERE STILL INSEPARABLE, AND PEOPLE BELIEVED THAT A KNOWLEDGE OF HOW THE SKIES WORKED COULD HELP TO PREDICT EVENTS ON EARTH.

CAMPION: HE WANTED TO UNDERSTAND THE WORKINGS OF THE UNIVERSE TO MAKE HIS ASTROLOGICAL PREDICTIONS MORE EXACT, SO HE'S ALSO EXTREMELY FAMOUS AS AN ASTRONOMER.

NARRATOR: JUST AS WITH EVERYTHING ELSE IN HIS LIFE, WHEN IT CAME TO ASTRONOMY, BRAHE DIDN'T DO THINGS HALFWAY.

MARCUS: TYCHO BRAHE SETS UP THE WORLD'S GREATEST OBSERVATORY ON HIS ISLAND OF HVEN.

I THINK IT'S 1% OF THE OPERATING BUDGET OF THE CROWN OF DENMARK IS DEDICATED TO FUNDING TYCHO'S ISLAND.

NARRATOR: WITH ALMOST LIMITLESS FUNDS PROVIDED BY THE KING OF DENMARK, BRAHE SET TO WORK FILLING HIS OBSERVATORY WITH THE MOST ADVANCED ASTRONOMICAL INSTRUMENTS YET SEEN.

MARCUS: THESE ARE INSTRUMENTS BEFORE THE TELESCOPE, SO HE HAS CREATED HUGE SEXTANTS AND QUADRANTS THAT TAKE MULTIPLE PEOPLE TO MANAGE AND RECORD THE DATA.

HIS INVENTION OF INSTRUMENTS ALLOWED HIM TO MEASURE WITH THE GREATEST-EVER PRECISION THE POSITIONS OF THE PLANETS AND STARS IN THE NIGHT SKY.

NARRATOR: BUT IT WASN'T JUST PLANETS AND STARS THAT BRAHE WAS INTERESTED IN.

SOMETHING ELSE HE SAW WAS ABOUT THE CHANGE OUR UNDERSTANDING OF THE UNIVERSE FOREVER.

ON NOVEMBER 13, 1577, BRAHE SPOTTED THE GREAT COMET FROM HIS OBSERVATORY.

[ROARING] NARRATOR: HE SET TO WORK PLOTTING ITS COURSE.

HIS CALCULATIONS SHOWED THAT THE GREAT COMET WAS PASSING THROUGH THE ORBIT OF VENUS, BUT ACCORDING TO THE ACCEPTED WISDOM, THIS SHOULDN'T BE POSSIBLE.

AT THIS TIME, PEOPLE BELIEVED THAT EVERYTHING IN THE COSMOS WAS CONTAINED WITHIN CONCENTRIC, CRYSTALLINE SPHERES.

MARCUS: THE IDEA OF THE CRYSTALLINE SPHERES ISN'T JUST A METAPHOR FOR PEOPLE AT THIS TIME.

PEOPLE THOUGHT THAT THEY ACTUALLY WERE CRYSTALLINE SPHERES.

NARRATOR: BRAHE REASONED THAT IT SHOULD HAVE BEEN IMPOSSIBLE FOR THE COMET TO FOLLOW THIS TRAJECTORY.

THE CRYSTALLINE SPHERES OUGHT TO HAVE STOPPED IT IN ITS TRACKS.

HE REALIZED THAT THE ONLY WAY FOR THE GREAT COMET TO FOLLOW THIS PATH WOULD BE IF THE CRYSTALLINE SPHERES SIMPLY DID NOT EXIST.

MARCUS: IN EFFECT, THE COMET OF 1577 AND TYCHO'S INTERPRETATION SHATTERS THOSE CRYSTALLINE SPHERES.

NARRATOR: AFTER 2,000 YEARS, THE CRYSTALLINE SPHERES WERE GONE, AND WITH THE IDEA OF A SUN-CENTERED UNIVERSE TAKING HOLD, THE DOOR WAS OPENED TO A WHOLE NEW ERA OF ASTRONOMY...

BUT THERE WAS STILL ONE ANCIENT IDEA THAT REMAINED-- THE BELIEF THAT EVERYTHING IN THE HEAVENS MOVED IN PERFECT CIRCLES.

THAT WAS UNTIL THE ARRIVAL OF A NEW STAR ASTRONOMER.

JOHANNES KEPLER WAS A GERMAN ASTRONOMER AND MATHEMATICIAN WHO WORKED IN PRAGUE.

HE HAD BEEN INSPIRED TO STUDY ASTRONOMY AS A CHILD WHEN HE WITNESSED GREAT COMET OF 1577.

CAMPION: KEPLER BELIEVED THAT GOD HAD CREATED THE UNIVERSE, AND, THEREFORE, BY WATCHING THE MOVEMENTS OF THE STARS AND THE PLANETS, YOU WOULD GET A GLIMPSE INTO THE UNFOLDING OF GOD'S PLAN.

HE DECIDED THAT THE WHOLE OF CLASSICAL AND MEDIAEVAL ASTROLOGY SHOULD BE DISCARDED AND WE SHOULD BEGIN AGAIN WITH A NEW, REFORMED ASTROLOGY BASED COMPLETELY ON EMPIRICAL OBSERVATION.

NARRATOR: MOST ASTRONOMERS STILL BELIEVED THAT EVERYTHING IN THE UNIVERSE MOVED IN PERFECT CIRCLES, BUT THIS THEORY COULDN'T EXPLAIN THE WAY PEOPLE SAW THE PLANETS MOVING IN THE SKIES...

SO FOR OVER 1,500 YEARS, THEY USED AN IDEA CALLED EPICYCLES WHERE PLANETS MOVED IN ORBITS THAT LOOKED LIKE SPIRALING LOOPS.

MARCUS: THAT HAS WORKED REALLY WELL FOR A LONG TIME, AND YET IT IS MESSY, THESE EPICYCLES.

UGH!

IT'S REALLY HARD TO WORK WITH.

NARRATOR: KEPLER WANTED TO SIMPLIFY THIS MODEL OF THE COSMOS, AND WITH ACCESS TO TYCHO BRAHE'S OBSERVATIONS, HE BEGAN TO RECALCULATE THE ORBITS OF THE PLANETS.

MARCUS: KEPLER'S GREAT CONTRIBUTION IS THAT HE TAKES TYCHO BRAHE'S NUMBERS, TYCHO BRAHE'S VERY PRECISE DATA, AND HE STARTS CALCULATING.

NARRATOR: AS KEPLER CRUNCHED THE NUMBERS, HE STRUCK ON AN IDEA SO BEAUTIFUL IN ITS SIMPLICITY THAT HE COULDN'T BELIEVE THAT NO ONE HAD THOUGHT OF IT BEFORE-- THE PLANETS DIDN'T MOVE IN CIRCLES.

THEY MOVED IN ELLIPSES.

TO GET AN ELLIPTICAL ORBIT, YOU TAKE A CIRCULAR ORBIT, AND YOU ESSENTIALLY SQUASH IT ON TWO SIDES SO IT'S MORE EGG-SHAPED.

MARCUS: THIS IS A HUGE CHANGE.

PLANETS DON'T APPEAR TO BE MAKING EXACT CIRCLES.

IN FACT, WHAT HE DISCOVERS ARE THE LAWS OF PLANETARY MOTION.

PLAIT: ONCE YOU HAD KEPLER COME ALONG AND SAY, "YOU KNOW WHAT?

THESE THINGS MOVE IN ELLIPSES," BOOM, THAT'S WHEN THE COPERNICAN MODEL WORKED.

NARRATOR: KEPLER PUBLISHED HIS NEW LAWS OF PLANETARY MOTION IN 1609 IN A BOOK CALLED "THE ASTRONOMIA NOVA."

HE HAD COME UP WITH A DESCRIPTION OF THE MOTIONS OF PLANETS WHICH ELIMINATED THE NEED FOR EPICYCLES, BUT IT WAS ONLY A THEORY.

THE ONE MAN WHO WOULD FINALLY PROVIDE PROOF WOULD ALSO DISCOVER THE FORCE THAT HELD THE UNIVERSE TOGETHER AND BECOME, ARGUABLY, THE MOST FAMOUS SCIENTIST OF ALL TIME.

IN 17th-CENTURY ENGLAND, ISAAC NEWTON WAS A MAN DETERMINED TO REWRITE JUST ABOUT EVERY TEXTBOOK GOING.

HE WAS A GENIUS WHO TURNED HIS HAND TO PHILOSOPHY, SCIENCE, AND MATH, EVEN TO ALCHEMY.

HAMILTON: WE MIGHT TODAY REMEMBER HIM AS BEING A PHYSICIST, JUST BEING AN ASTRONOMER, AND BEING A MATHEMATICIAN.

AT THE TIME, HE WAS WORKING IN THE CONTEXT OF NATURAL PHILOSOPHY, WHICH WAS A MORE HOLISTIC WAY OF UNDERSTANDING THE UNIVERSE.

NARRATOR: NEWTON WAS A DEEPLY RELIGIOUS MAN WHO BELIEVED THAT SCIENCE COULD REVEAL GOD'S MASTER PLAN FOR THE UNIVERSE.

HE WAS ALSO A RADICAL.

FOR THOUSANDS OF YEARS, THE ASSUMPTION HAD BEEN THAT THINGS IN SPACE WORKED VERY DIFFERENTLY THAN HOW THEY DID ON EARTH, BUT NEWTON HAD OTHER IDEAS.

HAMILTON: HE NOT ONLY COMES UP WITH THESE SIMPLE LAWS TO EXPLAIN WHAT HAPPENS HERE ON EARTH, BUT EVEN MORE IMPORTANTLY, HE SAYS THAT THESE SAME LAWS WORK OUTSIDE OF EARTH.

CAMPION: ISAAC NEWTON ARGUES THAT THE WHOLE UNIVERSE IS GOVERNED BY A SINGLE LAW-- THE LAW OF GRAVITY.

IMARA: GRAVITY IS ONE OF THE 4 FUNDAMENTAL FORCES OF NATURE, AND IT'S THE FORCE OF ATTRACTION THAT ANY OBJECTS THAT HAVE MASS WILL FEEL TOWARDS EACH OTHER.

NARRATOR: NEWTON NEEDED A WAY TO PROVE THE THEORY THAT GRAVITY WORKED THE SAME EVERYWHERE IN THE UNIVERSE, AND IN 1680, PROOF ARRIVED FROM OUTER SPACE.

MARCUS: THE COMET OF 1680, IT WAS INCREDIBLY BRIGHT, AND YOU COULD SEE IT DURING THE DAYTIME, AND IT BECOMES A TOPIC OF DISPUTE, ESPECIALLY AMONG NEWTON'S CIRCLE, BECAUSE PEOPLE SEE THE COMET PASS IN 1680 AND THEN ANOTHER COMET COMES BACK IN 1681, AND THERE IS A QUESTION-- IS THIS ONE COMET, OR IS THIS TWO COMETS?

NARRATOR: NEWTON REALIZED THAT HIS THEORY OF GRAVITY HELD THE ANSWER TO THIS QUESTION.

IN HIS MIND, THE COMETS OF 1680 AND 1681 HAD TO BE ONE AND THE SAME.

HE ARGUED THAT IT HAD JOURNEYED THROUGH THE SOLAR SYSTEM ONCE BEFORE THE SUN'S GRAVITY HAD SWUNG IT BACK AGAIN.

MARCUS: WHEN PEOPLE DISCOVER THAT IT'S ONE COMET, THEY UNDERSTAND THEN THAT IT'S GONE AROUND THE SUN AND IT'S COMING BACK AROUND THE OTHER SIDE OF ITS ORBIT.

NARRATOR: NEWTON REALIZED THAT THE GRAVITY OF THE SUN HAD CAUSED THE COMET TO FOLLOW AN ELLIPTICAL PATH THROUGH THE COSMOS, SO COULD GRAVITY ALSO SUPPORT THE THEORY THAT THE PLANETS MOVED ON ELLIPTICAL ORBITS?

IMAGINE THAT I AM THROWING A BALL TO YOU WHICH IS A NEWLY FORMED PLANET WITH SOME INITIAL VELOCITY.

IT WOULD GO IN A STRAIGHT LINE TOWARDS YOU...

BUT IF WE THEN SWITCHED ON, IN THE CENTER OF A ROOM, SOME ATTRACTIVE FORCE-- SO THAT WOULD BE THE GRAVITY FROM THE SUN-- THE NEWLY FORMED PLANET WOULDN'T GO STRAIGHT TO YOU, AND IT WOULDN'T GO STRAIGHT INTO THE CENTER OF THE SUN, EITHER.

IT WOULD FORM A CURVED ORBIT, AND THAT WOULD BE ELLIPTICAL.

NARRATOR: GRAVITY POWERED ELLIPTICAL ORBITS, AND IT WAS THE GLUE THAT HELD THE UNIVERSE TOGETHER.

WE FINALLY HAD AN ACCURATE MODEL OF OUR SOLAR SYSTEM-- WELL, ALMOST-- BUT BEFORE WE COULD EXTEND OUR KNOWLEDGE OF THE HEAVENS ANY FURTHER, WE HAD AN IMPORTANT, EARTHBOUND PROBLEM TO SOLVE.

BEGINNING IN THE 16th CENTURY, VAST COLONIAL EMPIRES BEGAN TO SPREAD OUT ACROSS THE PLANET.

THERE WAS A RUSH TO CONQUER AND EXPLOIT THE WEALTH OF NEWLY DISCOVERED TERRITORIES.

FOR SEAFARING NATIONS LIKE THE ENGLISH, SPANISH, AND FRENCH, BEING ABLE TO NAVIGATE ACCURATELY AND SAFELY WAS ESSENTIAL.

HAMILTON: THERE'S AN EXAMPLE OF A SHIP THAT WAS LOST AT SEA TRYING TO FIGURE OUT WHERE THEY ACTUALLY WERE IN THE WIDE OPEN OCEAN, AND MEANWHILE, HUNDREDS OF CREWMEMBERS DIED OF SCURVY.

THIS ACTUALLY IS A LIFE-AND-DEATH SITUATION.

[THUNDER] NARRATOR: IN 1707, A NAVIGATIONAL ERROR CAUSED A FLEET OF SHIPS TO CRASH INTO THE ISLES OF SCILLY OFF THE SOUTHWEST COAST OF ENGLAND.

IT WAS ONE OF THE DEADLIEST MARITIME DISASTERS IN HISTORY.

UP TO 2,000 SAILORS LOST THEIR LIVES.

HAMILTON: THIS BECAME PUBLIC OUTCRY, RIGHT, ABOUT THIS.

THIS ISN'T OK TO HAVE PEOPLE GOING OUT AND DOING COMMERCE FOR ENGLAND AND DYING ON THE WAY BACK.

[THUNDER] NARRATOR: ALTHOUGH SAILORS COULD USE THE SUN AND STARS AS A COMPASS, IT WASN'T ENOUGH JUST TO KNOW WHAT DIRECTION THEY WERE GOING.

PLOTTING THEIR EXACT POSITION WAS A PROBLEM.

THEY COULD USE THE POLE STARS TO WORK OUT LATITUDE, THEIR POSITION NORTH OR SOUTH.

PLAIT: AT NIGHT, YOU JUST MEASURE HOW HIGH POLARIS IS OFF THE HORIZON, AND TO WITHIN A DEGREE OR SO, THAT'S YOUR LATITUDE.

NARRATOR: BUT TO PINPOINT THEIR EXACT POSITION, MARINERS ALSO NEEDED TO KNOW THEIR LONGITUDE, THEIR POSITION EAST OR WEST.

THIS WAS ALMOST IMPOSSIBLE.

PLAIT: BECAUSE THE EARTH IS SPINNING, THERE'S NO DISTINGUISHING CHARACTERISTIC ON IT EAST AND WEST, SO REALLY, YOU JUST HAVE TO MAKE ONE UP AND SAY ARBITRARILY, "THIS SPOT BECOMES ZERO DEGREES LONGITUDE."

YOU CAN DO THAT, BUT IF YOU MOVE AWAY FROM IT, THEN IT BECOMES VERY, VERY DIFFICULT TO KNOW EXACTLY WHAT YOUR LONGITUDE IS.

NARRATOR: AS FAR BACK AS THE SECOND CENTURY BC, THE GREEK MATHEMATICIAN HIPPARCHUS BELIEVED THAT THE ANSWER LAY IN THE SKIES.

HE PROPOSED THAT IF YOU COULD COMPARE THE SOLAR TIME WHERE YOU WERE NOW WITH THE TIME WHERE YOU HAD SET OFF, THEN YOU COULD CALCULATE YOUR POSITION EITHER EAST OR WEST.

ALTHOUGH THIS THEORY WAS SOUND, THERE WAS A PROBLEM WITH IT.

IN THE 2,000 YEARS SINCE HIPPARCHUS, NO ONE HAD INVENTED A CLOCK THAT COULD WORK ACCURATELY AT SEA.

PLAIT: FOR MOST OF HISTORY, KEEPING TIME USED SOME SORT OF DEVICE LIKE, SAY, A PENDULUM.

WELL FOR A PENDULUM TO WORK AND FOR YOU TO BE ABLE TO MEASURE THESE NICE, EVEN SWINGS, THIS NEEDS TO BE ON A STEADY SURFACE THAT ISN'T MOVING.

IF YOU PUT SOMETHING LIKE THIS ON A BOAT, THESE ARE FAMOUS FOR ROCKING, SO AS THE SEA IS MOVING UP AND DOWN, THAT'S AFFECTING THE MOTION OF THE PENDULUM.

IT'S BASICALLY IMPOSSIBLE TO KEEP TIME THAT WAY.

NARRATOR: WHAT WAS NEEDED WAS A NEW KIND OF CLOCK.

IT WOULD COME NOT FROM A CLOCKMAKER, BUT FROM A CARPENTER.

[CLACKING] IN 1714, WITH MOUNTING PRESSURE FROM THE MARITIME COMMUNITY, THE BRITISH GOVERNMENT PASSED A LAW CALLED THE LONGITUDE ACT.

THEY PUT UP A REWARD EQUALING ALMOST $2 MILLION IN TODAY'S MONEY TO ANYONE WHO COULD CRACK THE PROBLEM OF CALCULATING LONGITUDE AT SEA.

JOHN HARRISON WAS A WOODWORKER FROM THE NORTH OF ENGLAND WITH A PASSION FOR REPAIRING CLOCKS.

HE SAW AN OPPORTUNITY TO CAPITALIZE ON HIS HOBBY, AND HE SET TO WORK DESIGNING A SEA CLOCK HE BELIEVED WOULD BE THE MOST ACCURATE THE WORLD HAD EVER SEEN.

DUNN: HERE TO MY LEFT IS JOHN HARRISON'S FIRST SEA CLOCK, WHICH WE NOW CALL H1.

IT HAS A NUMBER OF INNOVATIONS THAT HARRISON HIMSELF CAME UP WITH.

INSTEAD OF A PENDULUM, IT HAS THESE WONDERFUL DUMBBELLS, AND THE IDEA HERE IS THAT ANYTHING THAT AFFECTS ONE WILL AFFECT THE OTHER IN THE OPPOSITE DIRECTION, SO ANY ERRORS CAUSED BY MOTION WILL COUNTERACT EACH OTHER.

NARRATOR: THE H1 WORKED AT SEA, AND IT KEPT TIME TO WITHIN 3 SECONDS A DAY, BUT HARRISON STILL WASN'T SATISFIED.

DUNN: HE BEGAN TO REALIZE THAT ACTUALLY, A SEA CLOCK WAS NOT GOING TO BE THE SOLUTION.

NARRATOR: SO HE WENT BACK TO THE DRAWING BOARD.

DUNN: IN THE EARLY 1750s, HE BEGAN LOOKING AT WATCHES AS THE SOLUTION.

NARRATOR: THE WATCH THAT HARRISON EVENTUALLY CAME UP WITH WAS THE H4.

DUNN: WHAT HE CAME UP WITH WAS A DESIGN WHICH HAD A LARGE, HEAVY BALANCE WHEEL WHICH OSCILLATED VERY QUICKLY, AND HIS THINKING WAS THAT THE SHIP MOVES IN A CERTAIN WAY FAIRLY SLOWLY, AND WITH THIS VERY-QUICKLY-MOVING, HIGH-ENERGY SYSTEM, IT WOULD NOT BE AFFECTED BY THE KINDS OF MOTION THAT WOULD AFFECT A SHIP.

NARRATOR: HARRISON'S H4 PROTOTYPE WAS PUT TO THE TEST IN 1764, AND IT WORKED.

FINALLY, WE HAD THE TECHNOLOGY TO HARNESS THE TIME GIVEN TO US BY THE SUN AND TAKE IT WITH US TO CALCULATE LONGITUDE AT SEA.

BY THE MIDDLE OF THE 18th CENTURY, TECHNOLOGY WAS ALSO HELPING US TO MAKE GREAT LEAPS FORWARD IN ASTRONOMY.

SINCE THE INVENTION OF THE TELESCOPE, WE HAD BEEN ABLE TO LOOK DEEPER AND DEEPER INTO THE COSMOS.

HAMILTON: THE TELESCOPE IS THE FIRST SCIENTIFIC INSTRUMENT THAT EXTENDS THE HUMAN SENSES.

NARRATOR: AND AS TELESCOPES GOT BIGGER AND BETTER, THEY REVEALED MORE AND MORE OF WHAT LAY IN OUR SOLAR SYSTEM.

CAMPION: WILLIAM HERSCHEL WAS BORN IN GERMANY.

HE CAME TO ENGLAND TO BE A MUSICIAN IN ENGLAND.

HE MOVED TO THE CITY OF BATH, WHERE HE ALSO DEVELOPED A DEEP AND PROFOUND INTEREST IN ASTRONOMY.

HE WORKED AND COLLABORATED WITH HIS SISTER CAROLINE, WHO HERSELF ALSO BECAME A DISTINGUISHED ASTRONOMER.

NARRATOR: THE HERSCHELS BUILT A SERIES OF INCREASINGLY POWERFUL TELESCOPES.

WITH THESE, THEY OBSERVED AND METICULOUSLY CATALOGUED THOUSANDS OF STARS.

IN 1781 AS HE GAZED AT THE NIGHT SKY, WILLIAM NOTICED AN OBJECT THAT GRABBED HIS ATTENTION.

HAMILTON: HE DID NOT KNOW AT THAT POINT WHAT IT WAS THAT HE HAD DISCOVERED, BUT HE WORKED WITH SOME OF HIS CONTEMPORARIES TO DETERMINE THAT, IN FACT, THIS WAS ANOTHER PLANET.

CAMPION: THEY ARE RESPONSIBLE FOR THE DISCOVERY OF THE PLANET URANUS.

NARRATOR: THIS WAS AN EARTH-SHATTERING DISCOVERY.

FOR MILLENNIA, WE HAD BELIEVED THERE WERE ONLY 5 PLANETS.

NOW, WITH THE DISCOVERY OF URANUS, WE HAD A SIXTH.

WILLIAM DEDICATED THIS NEW PLANET TO KING GEORGE III.

THE GESTURE WON HERSCHEL ROYAL FAVOR, AND HE WAS MADE THE KING'S ASTRONOMER.

THIS MEANT THAT HERSCHEL NOW HAD THE FUNDS AND THE FREEDOM TO BUILD EVEN BIGGER AND BETTER TELESCOPES THAN EVER BEFORE, AND IN 1789, HE COMPLETED A TELESCOPE THAT WOULD BE HIS CROWNING ACHIEVEMENT.

DEVOY: THIS IS THE LAST REMAINING QUARTER OF WILLIAM HERSCHEL'S LARGEST TELESCOPE, THE 40-FOOT REFLECTOR, THAT WAS BUILT BETWEEN 1785 AND 1789.

AT THE END HERE, YOU'D HAVE THE MIRROR, WHICH HE POLISHED AND SHAPED HIMSELF-- IT WOULD TAKE MANY, MANY HOURS OF WORK TO ACHIEVE THAT-- AND THEN THE WHOLE STRUCTURE WAS SUPPORTED BY A VERY LARGE, WOODEN FRAME THAT ROTATED ON ROLLERS SO THAT THE TELESCOPE COULD BE POINTED TO ANY PART OF THE SKY.

THIS WAS CERTAINLY THE LARGEST TELESCOPE IN THE WORLD AT THAT TIME.

NARRATOR: WHEN HERSCHEL TURNED THIS GIANT TELESCOPE TOWARDS THE SKIES, HE MADE EVEN MORE NEW DISCOVERIES.

DEVOY: SO WHEN WILLIAM HERSCHEL FIRST USED THIS TELESCOPE IN 1789, HE DISCOVERED THE SIXTH AND SEVENTH MOONS OF SATURN-- ENCELADUS AND MIMAS.

THAT WAS A REALLY IMPORTANT MOMENT IN THIS TELESCOPE'S HISTORY.

NARRATOR: HERSCHEL'S 40-FOOT TELESCOPE BECAME A GLOBAL SYMBOL OF SCIENTIFIC PROGRESS.

IT OPENED THE DOOR TO A NEW ERA OF ASTRONOMICAL EXPLORATION, AND AS WE STUDIED THE COSMOS IN UNPRECEDENTED DETAIL, OUR IMAGINATIONS BEGAN TO RUN WILD.

CAMPION: ONE DIRECT EFFECT OF TECHNOLOGY ON OUR ABILITY TO LOOK FURTHER INTO THE UNIVERSE AND IMAGINE HOW WE MIGHT TRAVEL THROUGH IT IS IN SCIENCE FICTION... AND THIS REACHES A PEAK IN THE 19th CENTURY WITH JULES VERNE.

HAMILTON: VERNE WAS A HIGHLY PROLIFIC WRITER, AND MANY OF HIS WORKS CONTAINED LOTS OF REALLY IMPORTANT DESCRIPTIONS OF TECHNOLOGY, SOMETIMES VERY FUTURISTIC TECHNOLOGY, THAT MANY ARGUE IS ACTUALLY VERY FORWARD-THINKING.

NARRATOR: IN 1865, VERNE PUBLISHED HIS BOOK "FROM THE EARTH TO THE MOON."

HAMILTON: JULES VERNE WRITES ABOUT THIS 19th-CENTURY, AMERICAN GUN CLUB, AND THEY'RE BASICALLY GOING TO BUILD A HUGE GUN AND FIRE 3 OF THE MEMBERS INTO SPACE AND LAND ON THE MOON.

WOMAN: "AN AWESOME SILENCE HUNG OVER THE WHOLE SCENE, "AND EVERYONE REALIZED THAT THE DARING EXPLORERS "INSIDE THE PROJECTILE WERE ALSO COUNTING THE SECONDS.

"38, 39, 40, FIRE."

NARRATOR: ALTHOUGH IT WAS A WORK OF FICTION, VERNE'S NOVEL BECAME AN INSPIRATION TO SCIENTISTS ALL OVER THE WORLD.

HAMILTON: THE REALLY KIND OF IMPORTANT THING HERE IS THAT IT'S VERY HIGHLY RESEARCHED.

JULES VERNE DOES THE LEGWORK TO EXPLAIN THE KINDS OF THRUST THAT WOULD BE NEEDED, TO EXPLAIN THAT TYPES OF MATERIALS THAT WOULD BE NEEDED TO MAKE THIS ACTUALLY HAPPEN.

NARRATOR: HIS CALCULATIONS WERE SO EXACT THAT, FOR THE FIRST TIME, THE IDEA OF BEING ABLE TO SEND A PERSON INTO SPACE APPEARED PLAUSIBLE...

STAND BY.

NARRATOR: BUT WHILE THE THEORY SEEMED SOUND... FIRE.

NARRATOR: ANY ARTILLERY EXPERT WILL TELL YOU THAT THE REALITY ISN'T SO STRAIGHTFORWARD.

MY NAME IS SERGEANT FIRST CLASS GARY WHITE.

I'M A 13 BRAVO FIELD ARTILLERY CANNON CREW MEMBER.

THE ARTILLERY PIECE THAT I'M STANDING IN FRONT OF IS THE M1A1 PACK 75 HOWITZER.

THE RANGE OF THESE HOWITZERS IN PARTICULAR ARE 5.5 MILES, 8.8 KILOMETERS.

FIRE!

WHITE: ACHIEVING LONGER RANGES FOR HOWITZERS IS GENERALLY ACCOMPLISHED THROUGH A LONGER BARREL, WHICH ALLOWS THE PROJECTILE TO ATTAIN A GREATER SPEED AND, HENCE, GREATER RANGE.

NARRATOR: IN THEORY, IF YOU COULD BUILD A CANNON LONG ENOUGH, YOU COULD FIRE A PROJECTILE OR A PERSON TO THE MOON.

[PIANO PLAYING] PERHAPS JULES VERNE'S SCIENCE FICTION COULD BECOME SCIENCE FACT.

IN THE MID 1960s, THE U.S. AND CANADIAN GOVERNMENTS FOUNDED A SCHEME CALLED PROJECT HARP.

THEY WANTED TO TEST THE FEASIBILITY OF FIRING A SATELLITE INTO ORBIT AROUND THE EARTH.

THE CANNON THEY BUILT WAS AROUND 100 FEET LONG.

MAN: 5, 4, 3, 2, 1, CLEAR.

WHITE: IT ACHIEVED AN ALTITUDE OF 180 KILOMETERS ABOVE THE EARTH'S SURFACE.

PROJECT HARP STILL MAINTAINS THE RECORD FOR GREATEST ALTITUDE ACHIEVED BY A PROJECTILE FIRED FROM A CANNON.

NARRATOR: 180 KILOMETERS IS ABOUT 112 MILES.

TECHNICALLY, THAT'S FAR ENOUGH TO PASS THE BOUNDARY FROM EARTH'S ATMOSPHERE INTO SPACE.

BUT TO TRULY BREAK FREE OF EARTH'S GRAVITY, YOU NEED TO GO BEYOND WHAT IS KNOWN AS NEAR-EARTH ORBIT.

WHITE: NEAR-EARTH ORBIT BEGINS AT 2,000 KILOMETERS ABOVE THE EARTH'S SURFACE.

WE ARE STILL DRAMATICALLY SHORT OF THAT MEASURE.

NARRATOR: THE DISTANCE FROM THE EARTH TO THE MOON IS AROUND 240,000 MILES.

TO MAKE VERNE'S MOON SHOT A REALITY, THE BARREL WOULD NEED TO BE OVER 15 TIMES LONGER THAN THE CANNON IN THE NOVEL.

WHITE: I THINK THAT, THEORETICALLY, IT IS POSSIBLE.

THE PRACTICABILITY OF IT IS RELATIVELY NIL.

NARRATOR: AND, AS IT TURNS OUT, THERE WAS ONE OTHER THING JULES VERNE HADN'T ACCOUNTED FOR.

WHITE: THE G FORCES EXPERIENCED BY A PROJECTILE WHEN IT'S INITIALLY FIRED OUT OF THE BARREL IS EXTREME, TO SAY THE LEAST.

IF A PERSON WERE SUBJECTED TO THE SAME STRESS AS AN ARTILLERY ROUND WERE WHEN FIRED, IT WOULD NOT END WELL FOR THEM.

THE PERSON WOULD WIND UP WITH BROKEN BONES, ABSOLUTELY DEAD.

NARRATOR: VERNE'S DREAM OF PUTTING PEOPLE ON THE MOON WOULD REMAIN LODGED FIRMLY IN THE REALM OF SCIENCE FICTION, AT LEAST FOR NOW, BUT THE FLOODGATES OF POPULAR IMAGINATION HAD BEEN OPENED.

NOW A WHOLE HOST OF WRITERS AND THINKERS WERE DREAMING OF WHAT, OR EVEN WHO, WE MIGHT FIND OUT IN SPACE.

IN 1877, THE PLANET MARS PASSED UNUSUALLY CLOSE TO THE EARTH, AND IN MILAN, AN ITALIAN ASTRONOMER NAMED GIOVANNI SCHIAPARELLI TOOK THE OPPORTUNITY TO STUDY THE RED PLANET IN UNPRECEDENTED DETAIL.

SCHIAPARELLI FILLED HIS NOTEBOOKS WITH HAND-DRAWN PICTURES OF MARS, DESCRIBING ALL OF THE FEATURES HE SAW THROUGH HIS TELESCOPE.

HE DREW METICULOUS MAPS OF A MARTIAN LANDSCAPE FILLED WITH WHAT HE NAMED CONTINENTS AND SEAS.

HAMILTON: ONE OF THE THINGS THAT HE NOTICED IS THAT ON THE SURFACE OF MARS, THERE SEEMED TO BE THESE, KIND OF, LIKE, CRISSCROSSING NETWORKS OF LINES AND DESCRIBED THEM AS CANALI, SO IN ITALIAN, THIS MEANS CHANNELS.

NARRATOR: BUT WHEN HIS WORKS WERE PICKED UP AROUND THE WORLD, THE WORD "CANALI" CAME TO BE MISTRANSLATED AS CANALS.

IT WAS AN ERROR THAT WOULD HAVE FAR-REACHING CONSEQUENCES.

HAMILTON: WHEN YOU THINK ABOUT CANALS, THEY ARE ARTIFICIALLY CREATED, AND IF SOMEONE IS CREATING THEM, SOMEONE HAS TO BE BUILDING THEM, RIGHT?

THEY HAVE TO BE CONSTRUCTED BY SOMEONE, WHICH CREATES THIS WAVE OF SPECULATION THAT LASTS UNTIL THE PRESENT DAY, RIGHT, THINKING ABOUT MARTIANS, LIKE, "WHAT ARE THE MARTIANS DOING?"

NARRATOR: SO BEGAN A NEW WAVE OF SCIENCE FICTION WRITING THAT SPECULATED WHAT LIFE MIGHT EXIST OUT IN SPACE.

CAMPION: IN A SENSE, IT'S A LOVELY THOUGHT THAT THERE COULD BE OTHER PEOPLE OUT THERE WITH WHOM WE CAN MAKE FRIENDS.

OF COURSE, THE OTHER SIDE OF IT IS, THERE MIGHT BE ALIENS OUT THERE WHO MIGHT ACTUALLY COME AND DEVOUR US.

NARRATOR: THE IDEA OF AN ALIEN THREAT INSPIRED ONE OF THE GREATEST WORKS OF SCIENCE FICTION OF ALL TIME-- H.G.

WELLS' BOOK "THE WAR OF THE WORLDS," A TALE IN WHICH A HOSTILE CIVILIZATION OF ALIENS FROM MARS INVADES THE EARTH.

LIKE THE GODS AND MONSTERS OF THE ANCIENT WORLD, ONCE AGAIN, WE WERE POPULATING THE UNIVERSE WITH STORIES OF FANTASTICAL CREATURES.

BY THE START OF THE 20th CENTURY, WE KNEW THAT OUR MILKY WAY GALAXY CONSISTED OF BILLIONS OF STARS JUST LIKE OUR OWN SUN, BUT WE STILL KNEW RELATIVELY LITTLE OF ITS SIZE AND SHAPE.

IN THE 1920s, WE DIDN'T EVEN KNOW THAT OUR UNIVERSE EXTENDED BEYOND OUR OWN GALAXY.

THE GENERAL CONSENSUS IS THAT THE UNIVERSE CONSISTS OF THE MILKY WAY GALAXY, THE END.

NARRATOR: EVEN ALBERT EINSTEIN BELIEVED THAT THE UNIVERSE WAS FINITE AND EVERYTHING IN IT HAD ALWAYS BEEN IN THE SAME PLACE.

WHEN EINSTEIN SOLVED HIS OWN EQUATIONS AND GAVE US WHAT HE THOUGHT THE UNIVERSE WOULD LOOK LIKE, IT WAS STATIC.

IT HAD ALWAYS BEEN SO.

NARRATOR: BUT THE THEORY OF THE GREATEST SCIENTIFIC MIND OF ALL TIME WAS ABOUT TO BE BLOWN APART BY A MAN OF THE CLOTH.

IN THE TOWN OF CHARLEROI IN BELGIUM WAS A CATHOLIC PRIEST.

GEORGES LEMAITRE HAD BEEN ORDAINED IN 1923, 7 YEARS AFTER EINSTEIN PUBLISHED HIS THEORY OF GENERAL RELATIVITY, BUT LEMAITRE WASN'T JUST A MAN OF RELIGION.

HE WAS ALSO A MAN OF SCIENCE.

SPYROMILLIO: GEORGE LEMAITRE WAS A THEORETICIAN, SO HE WORKED WITH PEN AND PAPER.

HE WAS AT PAINS TO SAY THAT THE BIBLE WAS NOT AN ASTRONOMICAL TEXT.

NARRATOR: LEMAITRE WAS A BRILLIANT MATHEMATICIAN, AND WHEN HE TOOK EINSTEIN'S EQUATIONS AND RECALCULATED THEM HIMSELF, HE CAME TO A VERY DIFFERENT CONCLUSION.

SPYROMILLIO: WHAT LEMAITRE ACTUALLY GAVE US WAS A SOLUTION TO EINSTEIN'S EQUATIONS FROM THE GENERAL THEORY OF RELATIVITY THAT SHOW THAT THE UNIVERSE WOULD BE EXPANDING.

NARRATOR: THIS WAS AN IDEA THAT WENT AGAINST CENTURIES OF ASTRONOMY.

EVEN EINSTEIN COULDN'T BRING HIMSELF TO BELIEVE IT COULD BE TRUE.

WHAT WAS NEEDED WAS PROOF.

SPYROMILLIO: EDWIN HUBBLE WAS BORN IN MISSOURI IN 1889.

HE IS THE ALL-AMERICAN BOY.

HE PLAYS BASKETBALL FOR CHICAGO.

HE CAPTAINS THE TEAM.

HE SPEAKS SPANISH.

HE STUDIES LAW AND AT SOME POINT DECIDES HE WANTS TO BECOME AN ASTRONOMER.

HE WORKED IN CHICAGO AT YERKES OBSERVATORY, WHICH WAS THE BIGGEST REFRACTOR OF THE TIME, SO HE GOT GREAT OBSERVATIONS THERE AND THEN MOVED TO CALIFORNIA, WHERE HE USED THE 100-INCH TELESCOPE TO DO THE REST OF HIS WORK.

NARRATOR: THE 100-INCH TELESCOPE AT THE HOOKER OBSERVATORY IN CALIFORNIA WAS THE MOST POWERFUL IN THE WORLD AT THAT TIME.

HUBBLE USED IT TO STUDY NEBULAE-- DISTANT, FUZZY CLOUDS OF LIGHT THAT HAD PUZZLED ASTRONOMERS.

FOR CENTURIES.

ONE OF THESE NEBULAE IN PARTICULAR CAUGHT HUBBLE'S IMAGINATION.

AMON: FOR THE FIRST TIME WITH THIS GREAT RESOLUTION WAS HE ABLE TO TAKE IMAGES OF THE ANDROMEDA NEBULA.

NARRATOR: HUBBLE COULD SEE THAT THE ANDROMEDA NEBULA WASN'T A CLOUD OF GAS, AS PEOPLE HAD LONG BELIEVED.

IT WAS ACTUALLY A VAST COLLECTION OF INDIVIDUAL STARS, AND HE WAS ABOUT TO SOLVE THE AGE-OLD CONUNDRUM OF WHAT ANDROMEDA REALLY WAS.

AT THIS TIME, MOST PEOPLE BELIEVED THAT OUR MILKY WAY WAS THE ONLY GALAXY IN THE UNIVERSE AND THAT ANDROMEDA WAS LOCATED INSIDE IT.

AMON: THERE WAS HOT DEBATE OVER WHETHER IT WAS STARS IN OUR OWN GALAXY OR SOMETHING OUTSIDE OF OUR OWN GALAXY.

NARRATOR: BUT HUBBLE HAD OTHER IDEAS.

HE WANTED TO CALCULATE ANDROMEDA'S DISTANCE FROM EARTH, AND TO DO THIS, HE USED A TECHNIQUE VERY SIMILAR TO THE WAY THAT WE CAN ESTIMATE HOW FAR AWAY LIGHTS ARE AT NIGHT BY OBSERVING THEIR INTENSITY.

BY MEASURING THE BRIGHTNESS OF ANDROMEDA'S STARS, HUBBLE WAS ABLE TO WORK OUT HOW DISTANT IT IS.

AMON: WELL, HE FOUND THAT THESE STARS WERE AT LEAST 10 TIMES FURTHER AWAY THAN ANY OF THE STARS THAT WE KNEW WERE IN OUR GALAXY.

NARRATOR: THIS WAS AN INCREDIBLE BREAKTHROUGH FOR ASTRONOMY.

HUBBLE REALIZED THAT IF STAR SYSTEMS EXISTED OUTSIDE THE MILKY WAY, THEN THE UNIVERSE WAS BIGGER THAN JUST OUR GALAXY.

THIS IS THE REVOLUTION THAT THE GALAXIES, THE NEBULAE THAT PEOPLE WERE SEEING, WERE GALAXIES.

"ISLAND UNIVERSES" THEY WERE CALLED.

HE'S ABLE TO PROVE THAT THERE ARE GALAXIES OUTSIDE OF THE MILKY WAY GALAXY AND SAYING ALL OF A SUDDEN, "WOW.

OUR UNIVERSE MIGHT BE MUCH, MUCH, MUCH LARGER THAN WE ORIGINALLY THOUGHT."

NARRATOR: FOR THE FIRST TIME, WE HAD PROOF THAT OURS WAS NOT THE ONLY GALAXY IN THE UNIVERSE-- IN FACT, IT WAS JUST ONE AMONG MANY-- BUT HUBBLE WASN'T DONE YET.

SPYROMILLIO: EDWIN HUBBLE MAKES A CAREER MEASURING THE UNIVERSE WITH THE VERY BEST TELESCOPES.

NARRATOR: AS HUBBLE STUDIED GALAXIES FAR BEYOND OUR OWN, HE COULD SEE THAT THE LIGHT COMING FROM THEM APPEARED RED.

HE KNEW THAT THIS INDICATED THEY WERE MOVING AWAY FROM THE EARTH.

IT'S A CONCEPT THAT CAN BE UNDERSTOOD MOST CLEARLY NOT WITH LIGHT... [TRAIN HORN BLOWS] [MOTORCYCLE PASSES] [TRUCK HORN BLOWS] BUT WITH SOUND.

[SIREN] SPYROMILLIO: AT SCHOOL, YOU WILL HAVE HAD THIS EXAMPLE GIVEN TO YOU WITH A SIREN OF AN AMBULANCE OR A TRAIN, AND YOU HEAR THE PITCH CHANGING, DEPENDING ON WHETHER SOMETHING IS MOVING AWAY OR TOWARDS YOU.

NARRATOR: SOUND TRAVELS IN WAVES.

[SIREN] AS AN AMBULANCE TRAVELS TOWARDS YOU, THE WAVELENGTH OF THE SIREN IS COMPRESSED, BUT AS IT PASSES YOU, THE WAVELENGTH GETS STRETCHED OUT, AND THE PITCH OF THE SIREN DROPS AS IT TRAVELS INTO THE DISTANCE.

LIGHT WORKS IN THE EXACTLY SAME WAY.

IMARA: WE CAN THINK OF LIGHT AS A WAVE WITH A SUCCESSION OF PEAKS AND VALLEYS, AND THE DISTANCE BETWEEN ANY TWO PEAKS IS WHAT WE CALL THE WAVELENGTH.

NARRATOR: THE WAVELENGTH OF LIGHT DICTATES ITS COLOR.

A SHORT WAVELENGTH APPEARS BLUE AND A LONGER ONE RED.

JUST LIKE SOUND, THE WAVELENGTH OF LIGHT CHANGES DEPENDING ON WHETHER IT'S MOVING TOWARDS YOU OR AWAY FROM YOU.

SPYROMILLIO: IF YOU TOOK A STREET LAMP AND IF YOU WERE TO RUN VERY FAST TOWARDS ONE OF THESE LAMPS, THE LIGHT THAT YOUR EYES WOULD SEE WOULD BE BLUE, AND IF YOU WERE TO RUN VERY FAST AWAY FROM IT, BACKWARDS BECAUSE YOU'D HAVE TO BE LOOKING AT IT, YOU WOULD ACTUALLY SEE REDDER LIGHT, AND WHEN YOU LOOK AT THE UNIVERSE, IT'S A VERY SIMILAR THING.

IF THE GALAXIES WERE MOVING TOWARDS YOU, THEN THEY WOULD APPEAR BLUE.

IF THE GALAXY IS MOVING AWAY FROM YOU, IT WOULD APPEAR TO YOU RED.

AMON: THIS WAS A GROUNDBREAKING MOMENT FOR ASTRONOMY.

THE GALAXIES ARE GETTING FURTHER APART.

THAT MEANS THAT OUR UNIVERSE IS EXPANDING.

NARRATOR: AN EXPANDING UNIVERSE WAS A GAME CHANGER.

FOR THE VERY FIRST TIME, WE KNEW THAT IT WASN'T STATIC.

IT WAS DYNAMIC.

WE WERE NOW CLOSER THAN EVER BEFORE TO UNDERSTANDING HOW THE UNIVERSE BEGAN.

BACK IN BELGIUM, GEORGES LEMAITRE WAS BEGINNING WORK ON HIS NEXT BIG IDEA.

THE FACT THAT THE UNIVERSE WAS EXPANDING WAS PROOF THAT HIS MATHEMATICAL CALCULATIONS HAD BEEN RIGHT AND EINSTEIN HAD BEEN WRONG.

LEMAITRE WAS A MAN OF BOLD IDEAS, AND, HAVING SHOWN THAT THE UNIVERSE WAS EXPANDING, HE BELIEVED HE ALSO HAD A THEORY FOR HOW IT BEGAN.

SPYROMILLIO: IF YOU TAKE A UNIVERSE THAT IS EXPANDING, IT IS A NATURAL QUESTION TO ASK WHAT HAPPENS IF I RUN THE CLOCK BACKWARDS, SO IF IT'S GETTING BIGGER NOW, IT WAS SMALLER IN THE PAST.

NARRATOR: LEMAITRE WENT BACK TO HIS CALCULATIONS AND THOUGHT ABOUT WHAT WOULD HAPPEN IF YOU KEPT WINDING THE CLOCK FURTHER AND FURTHER BACK.

SPYROMILLIO: KEEP ON WINDING THE CLOCK BACKWARDS, AND YOU REALIZE THAT THINGS BECOME DENSER AND DENSER AND DENSER.

LEMAITRE WORKED OUT THAT AT CERTAIN POINT, THE DENSITY OF THE MATERIAL IF YOU WOUND EVERYTHING BACK WOULD BE LIKE AN ATOM, AND THIS WAS HIS STARTING POINT.

NARRATOR: AT THE TIME, IT WAS BELIEVED THAT THE ATOM WAS THE SMALLEST PARTICLE IN THE UNIVERSE, AND LEMAITRE USED THIS AS THE SINGULAR POINT FROM WHICH ALL CREATION SPRANG FORTH.

HE CALLED IT THE PRIMEVAL ATOM.

THIS WAS A TRULY RADICAL IDEA.

EINSTEIN'S THEORY OF GENERAL RELATIVITY PREDICTED THAT THE UNIVERSE HAD ALWAYS BEEN THERE-- IT COULDN'T HAVE A BEGINNING-- BUT LEMAITRE WAS PROPOSING THE OPPOSITE OF THIS, THAT THE UNIVERSE WAS BORN FROM A SINGLE POINT.

AT SOME POINT THIS EXPANDS, EXPLODES, BLOWS UP.

IT BECOMES THE UNIVERSE THAT WE SEE NOW.

NARRATOR: LEMAITRE HAD LAIN THE FOUNDATION FOR THE THEORY OF THE BIG BANG.

NOW FOR THE FIRST TIME, WE HAD A CREATION STORY GIVEN TO US NOT BY MYTHOLOGY OR RELIGION, BUT BY SCIENCE.

IT HAS BEEN A CENTURY SINCE HUBBLE AND LEMAITRE SUGGESTED THAT OUR UNIVERSE HAD AN ORIGIN.

IN THAT TIME, WE HAVE LAUNCHED SATELLITES AND TELESCOPES INTO SPACE TO HELP US SEE FURTHER THAN EVER BEFORE AND TO CONTINUE THE WORK THEY STARTED.

PERHAPS THE MOST FAMOUS SPACE TELESCOPE OF THEM ALL EVEN BEARS HUBBLE'S NAME, AND IN 2012, IT GAVE US ONE OF THE MOST ICONIC PICTURES IN MODERN ASTRONOMY-- THE HUBBLE EXTREME DEEP FIELD IMAGE.

IT REVEALED FOR THE FIRST TIME THE TRUE EXTENT OF OUR UNIVERSE.

SPYROMILLIO: ALMOST EVERYTHING IN THAT PICTURE IS A GALAXY, BILLIONS OF STARS IN EACH ONE OF THOSE STRUCTURES THAT YOU SEE BEHIND ME.

AMON: FROM THIS IMAGE, WE KNOW THAT THERE ARE TENS OF BILLIONS OF GALAXIES IN OUR UNIVERSE.

NARRATOR: WE CURRENTLY ESTIMATE THAT THERE ARE AT LEAST 100 BILLION GALAXIES IN OUR UNIVERSE.

SOME BELIEVE THERE COULD EVEN BE DOUBLE THAT NUMBER.

SPYROMILLIO: IT'S POSSIBLY THE DEEPEST IMAGE OF THE SKY EVER TAKEN, SO IT LOOKS FURTHEST INTO THE HISTORY OF OUR UNIVERSE.

NARRATOR: AND THE FURTHER OUT WE LOOK IN SEARCH OF MORE AND MORE GALAXIES, THE FURTHER WE ARE ALSO LOOKING BACK IN TIME TO THE VERY LIMIT OF THE VISIBLE UNIVERSE.

AMON: SO WE CAN OBSERVE THE VERY FIRST LIGHT THAT THE UNIVERSE EMITTED.

WE CALL THIS THE COSMIC MICROWAVE BACKGROUND, AND IT'S BASICALLY THE LEFTOVER ENERGY FROM WHAT WE THINK WAS THE START OF THE UNIVERSE.

NARRATOR: THIS COSMIC MICROWAVE BACKGROUND HAS HELPED US TO CALCULATE HOW OLD THE UNIVERSE MIGHT BE.

IMARA: CURRENT ESTIMATES BY ASTRONOMERS PUT THE AGE OF THE UNIVERSE AT ABOUT 13.8 BILLION YEARS.

THIS MEANS THAT IN OUR DEEPEST IMAGES OF THE UNIVERSE, WE'RE LOOKING AT THE UNIVERSE AS IT APPEARED 13.8 BILLION YEARS AGO.

NARRATOR: NEW TECHNOLOGY CONTINUES TO IMPROVE OUR OBSERVATION AND UNDERSTANDING OF THE UNIVERSE.

IN 2019, WE FINALLY PRODUCED AN IMAGE OF SOMETHING FIRST PREDICTED BY ALBERT EINSTEIN-- A BLACK HOLE, BUT OUR THIRST FOR KNOWLEDGE REMAINS UNQUENCHED.

AT THE HEADQUARTERS OF THE EUROPEAN SOUTHERN OBSERVATORY IN MUNICH, GERMANY... DR. JASON SPYROMILLIO IS OVERSEEING THE CONSTRUCTION OF PARTS FOR THE LARGEST OPTICAL TELESCOPE IN THE WORLD.

IT'S CALLED THE ELT.

ELT IS THE EXTREMELY LARGE TELESCOPE.

WE ARE NOT VERY ORIGINAL WITH THE NAMES, BUT IT'S ACTUALLY APT.

IT IS AN EXTREMELY LARGE TELESCOPE.

NARRATOR: THE ELT IS BEING BUILT ON THE TOP OF A MOUNTAIN IN THE ATACAMA DESERT IN CHILE.

IT IS DUE TO BE COMPLETED IN 2025.

SPYROMILLIO: THE DIAMETER IS 39 METERS.

BY COMPARISON, THE BIGGEST TELESCOPES THAT WE'RE RUNNING TODAY HAVE DIAMETERS OF 8 TO 10 METERS, SO THIS IS AN ENORMOUS LEAP FORWARD.

NARRATOR: ONCE BUILT, IT WILL COLLECT 13 TIMES MORE LIGHT THAN THE MOST POWERFUL TELESCOPES AROUND TODAY AND 100 MILLION TIMES MORE LIGHT THAN THE HUMAN EYE.

DR. SPYROMILLIO IS LOOKING FORWARD TO THAT EXTRA POWER BEING PUT TO GOOD USE.

SPYROMILLIO: ONE OF THE MOST EXCITING THINGS IS GOING TO BE TO DETECT PLANETS AROUND OTHER STARS.

THE OTHER THING THE ELT WILL DO IS BE ABLE TO SEE STARS IN FAIRLY DISTANT GALAXIES.

YOU CAN WORK OUT HOW OLD THEY ARE.

YOU CAN WORK OUT HOW MANY METALS THEY HAVE.

YOU CAN WORK OUT WHERE THEY'VE BEEN.

YOU'RE SUDDENLY MEASURING REALLY WHAT IS HAPPENING INSIDE THE GALAXIES.

THIS IS AN INCREDIBLY POWERFUL MACHINE THAT ALLOWS US TO FURTHER TIE DOWN OUR UNDERSTANDING OF WHY THE UNIVERSE IS THE WAY IT IS.

THIS IS SUPER EXCITING.

NARRATOR: IT MAY BE HARD TO BELIEVE THAT WE ONCE THOUGHT THE EARTH WAS FLAT... THAT WE WERE AT THE CENTER OF EVERYTHING, AND THAT THE UNIVERSE BEGAN AND ENDED WITH OUR OWN GALAXY.

[ROARS] FOR MILLENNIA, WE EXPLAINED THE HEAVENS THROUGH STORIES OF GODS AND MONSTERS... [ROARS] BUT WITH THE INVENTION OF THE TELESCOPE, WE BEGAN TO REVEAL A RATIONAL UNIVERSE.

THANKS TO THE SCIENCE OF ASTRONOMY, WE HAVE DISCOVERED NEW PERSPECTIVES ON THE COSMOS, BUT THERE IS STILL SO MUCH YET TO BE REVEALED.

AMON: OUR UNDERSTANDING OF THE UNIVERSE IS STILL VERY INCOMPLETE.

EVERYTHING THAT WE KNOW OF FROM PLANETS AND THE STARS AND GASES, THESE ONLY ACCOUNT FOR 5% OF THE OBSERVABLE UNIVERSE.

THE OTHER 95% IS LARGELY STILL A MYSTERY.

NARRATOR: AND UNTIL WE FINALLY HAVE THE SCIENTIFIC SOLUTIONS TO THE GREATEST QUESTIONS...

THERE WILL ALWAYS BE SPACE FOR US TO FILL WITH OUR IMAGINATION.

[ROARING] ♪♪ ANNOUNCER: TO ORDER THIS PROGRAM ON DVD, VISIT SHOPPBS OR CALL 1-800-PLAY-PBS, ALSO AVAILABLE ON AMAZON PRIME VIDEO.

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