PATRICK STEWART: SINCE THE DAWN OF HUMANKIND, WE HAVE LOOKED TO THE STARS AND WONDERED, WHAT'S UP THERE?

WHAT LIES BEYOND THIS SMALL, BLUE PLANET WE CALL HOME?

"IF ONLY," OUR ANCESTORS THOUGHT, "THERE WAS A WAY TO BRING THE SKY CLOSER TO REALLY SEE THE STARS."

JUST HOW HUMANITY MANAGED TO DO THIS IS QUITE A TALE.

IT WOULD TAKE CRYSTALS FORGED INSIDE THE EARTH... JUST THE RIGHT AMOUNT OF SALT, A CHANCE ALIGNMENT OF TWO SMALL PIECES OF GLASS, A PROPERTY BOOM IN NEW YORK, AND AN ACCIDENT OF CHEMISTRY AND LIGHT TO CREATE THE DEVICE THAT WOULD OPEN OUR EYES TO THE UNIVERSE ITSELF-- THE TELESCOPE.

THESE ARE THE INVENTIONS THAT DEFINE OUR AGE AND CHANGED OUR WORLD FOREVER.

THEY HAVE ALLOWED US TO MOVE ON THE GROUND AND IN THE AIR, TO CONNECT WITH EACH OTHER, AND MAKE MACHINES IN OUR OWN IMAGE... EACH A STORY OF INGENUITY, OF WONDER, OF BREAKTHROUGH.

STEWART: TODAY, WE ARE ON THE BRINK OF A NEW REVOLUTION.

GIANT NEW TELESCOPES ARE BEING BUILT ALL OVER THE WORLD, WHICH SCIENTISTS HOPE WILL ANSWER SOME OF THE OLDEST AND MOST PROFOUND QUESTIONS HUMANS HAVE EVER ASKED-- HOW BIG IS THE UNIVERSE?

ARE WE ALONE?

DO THE STARS GO ON FOREVER?

THIS IS A REALLY FANTASTIC TIME TO BE AN ASTRONOMER, HELPING US BUILD THE PICTURE OF UNDERSTANDING ABOUT THE UNIVERSE THAT WAS COMPLETELY UNIMAGINABLE EVEN 100 YEARS AGO.

STEWART: AROUND THE WORLD, A NEW GENERATION OF TELESCOPES IS PUSHING THE LIMITS OF OUR VISION EVER DEEPER INTO THE COSMOS, AND THE HUBBLE SPACE TELESCOPE IS STILL AT THE FOREFRONT OF THIS EFFORT.

ASTRONOMERS HERE AT THE SPACE TELESCOPE SCIENCE INSTITUTE ARE COMBINING IMAGES FROM HUBBLE WITH OTHER TELESCOPES TO STRETCH OUR VISION AS FAR AS POSSIBLE.

SALMON: WE'RE LOOKING FOR THE MOST DISTANT GALAXIES THAT WE CAN FIND IN THE UNIVERSE.

THERE'S ENTIRE SYSTEMS AND WORLDS OUT THERE THAT, YOU KNOW, I'M SEEING FOR THE FIRST TIME.

STEWART: THE STORY OF THE TELESCOPE IS INSEPARABLE FROM WHO WE ARE.

MAN: IT TOOK OVER 13 BILLION YEARS TO GET TO THIS POINT WHERE WE COULD BUILD TELESCOPES IN SPACE AND WITNESS OUR ORIGINS.

STEWART: THESE GLEAMING TECHNOLOGICAL MIRACLES OF GLASS AND STEEL DEFINE OUR AGE.

BUT THE TELESCOPE'S ORIGIN IS STRANGER THAN YOU WOULD IMAGINE.

IT WOULD ALL BEGIN WITH A PILE OF ROCKS IN SOUTHERN EUROPE.

♪ MAN: 6,000 YEARS AGO, THE STONE AGE PEOPLE LIVING IN THIS PART OF PORTUGAL BUILT THESE STONE STRUCTURES.

FOR THE LAST 10 YEARS, I'VE BEEN STUDYING THESE ANCIENT SITES AROUND THE COUNTRYSIDE WHERE I GREW UP.

AND I BELIEVE THESE MEGALITHS WERE ONE OF OUR EARLIEST ATTEMPTS TO STUDY THE STARS.

BUT WHY WERE THE STARS SO IMPORTANT TO THESE ANCIENT PEOPLE?

BECAUSE THE STONE AGE COMMUNITIES LIVING HERE WERE HUNTER GATHERERS AND SHEPHERDS.

THEY WERE LIVING OFF THE LAND, WHICH ISN'T ALWAYS EASY.

THAT'S WHY IN THE SUMMER THEY WOULD GO INTO THE MOUNTAIN RANGES THAT WERE GREEN AND PROVIDED ENOUGH PASTURE FOR THEIR ANIMALS AND FOR THEMSELVES.

AND THE BEST WAY TO KNOW WHEN IT WAS TIME TO MOVE TO THE MOUNTAINS WAS TO LOOK TO THE STARS.

SO HOW DID THESE MEGALITHS HELP THEM IN THIS QUEST?

IN A PERFECTLY DARK NIGHT SKY, THE HUMAN EYE CAN SEE AROUND 5,000 STARS.

TO LOOK BEYOND AND SEE THINGS THAT WE WOULDN'T NORMALLY SEE, WE NEED THE TELESCOPE.

AND I THINK THAT SUCH TECHNOLOGY WAS ALREADY PRESENT 6,000 YEARS AGO, 1,000 YEARS BEFORE STONEHENGE AND ABOUT 1,500 YEARS BEFORE THE PYRAMIDS IN EGYPT.

AND WE ALSO FIND THE REMAINS OF IT HERE IN PORTUGAL IN THE SHAPE OF THESE STONE MONUMENTS OR DOLMENS.

THEY ONLY HAD STONE TOOLS, WOODEN TOOLS, AND POSSIBLY BONE TOOLS.

AND YET, SOMEHOW THEY MANAGED TO CARVE THESE ROCKS OUT OF THE LANDSCAPE, DRAG THEM A FEW MILES, AND PUT THEM IN PLACE.

THIS WAS CLEARLY A PROJECT OF HUGE SIGNIFICANCE FOR THESE COMMUNITIES, AND THEY DIDN'T JUST DO IT ONCE.

THERE ARE BETWEEN 15 AND 20 MONUMENTS IN THIS RIVER VALLEY ALONE WITH THE SAME ORIENTATION, TOWARDS THE EAST.

I THINK THESE ROCK CHAMBERS WERE USED TO ACCUSTOM THEIR EYES TO THE DARK, ALLOWING THEM TO SEE FAINTER STARS.

USING COMPUTER SOFTWARE, WE CAN RECONSTRUCT THE SKIES 6,000 YEARS AGO, AS IT WOULD HAVE BEEN SEEN FROM INSIDE THESE STONE MONUMENTS.

IN THE COURSE OF A YEAR, AS WE ORBIT THE SUN, AS SEEN FROM THE EARTH, THE SUN APPEARS TO PASS THROUGH DIFFERENT PARTS OF THE SKY.

IN THE SPRING, A STAR CALLED ALDEBARAN BEGINS TO APPEAR CLOSE TO THE SUN AS IT RISES IN THE EAST, MARKING THE PERFECT TIME OF THE YEAR TO MOVE TO HIGHER PASTURE.

THE PROBLEM IS THAT ALDEBARAN IS ALL BUT OBSCURED BY THE GLARE OF THE RISING SUN, WHICH MAKES IT HARD TO SEE.

BUT I THINK THESE DOLMEN, WITH THEIR LARGE CHAMBERS AND LONG, STONE TUNNEL, WOULD HAVE ALLOWED THEM TO FOCUS THEIR EYES ON A SMALLER PATCH OF SKY TO SEE THE STAR AT SUNRISE SOONER THAN THEY WOULD BY STANDING OUTSIDE, SIGNALING TO MOVE TO THE MOUNTAINS FOR THE SUMMER.

THESE STRUCTURES MARK THE MOMENT IN HUMAN HISTORY WHEN WE REALIZED THAT THE SKIES RAN PREDICTABLY LIKE CLOCKWORK, AND IF YOU COULD SEE THE STARS BETTER AND, THEREFORE, DECIPHER THE PATTERNS IN THE NIGHT SKY, IT COULD HELP YOU TO SURVIVE.

ACROSS THE WORLD THERE ARE MANY OTHER STONE STRUCTURES FROM THIS TIME WHICH ALSO APPEAR TO BE ALIGNED WITH THE HEAVENS.

IT SEEMS THAT AS SOON AS WE COULD DEPLOY TECHNOLOGY, EVEN STONE TECHNOLOGY, WE APPLIED IT TO THE STARS.

TO ME, THIS POTENTIALLY REPRESENTS HUMANITY'S FIRST STEPS INTO THIS JOURNEY OF DISCOVERING THEIR PLACE IN THE COSMOS.

STEWART: ACROSS THE WORLD, OUR ANCESTORS WERE EXPLORING THE HEAVENS.

FROM EGYPT TO AUSTRALIA, EARLY HUMAN CIVILIZATIONS WERE DRIVING A REVOLUTION IN HUMAN VISION, STRETCHING OUR SIGHT FURTHER OUT INTO THE COSMOS THAN THE NAKED EYE ALONE COULD ACHIEVE.

BUT THE TELESCOPE REQUIRES ONE MATERIAL ABOVE ALL OTHERS-- GLASS.

AND THE FIRST GLASS WOULD COME FROM THE EARTH ITSELF.

WOMAN: OVER 5,000 YEARS AGO, THE PEOPLE OF RIFEH AND EL BADARI IN CENTRAL EGYPT STARTED TO PICK UP SMALL PIECES OF GLASSY QUARTZ CRYSTAL THAT CAUGHT THEIR EYE, AND THIS IS ONE OF THEM.

AROUND THE WORLD, PEOPLE WERE FINDING NATURALLY-OCCURRING CRYSTAL FRAGMENTS LIKE THIS THAT APPEARED TO DISTORT THE LIGHT.

NO ONE KNOWS FOR SURE WHAT THEY MIGHT HAVE BEEN USED FOR, PERHAPS AS A TOOL OF SOME KIND OR SIMPLY AS JEWELRY OR SOME KIND OF DECORATION.

BUT THEY ALL HAVE ONE THING IN COMMON-- THEY COULD CONTROL LIGHT.

STEWART: HOW THEY WERE DOING THIS REMAINED A MYSTERY, ONE THAT WOULD ONLY BE SOLVED BY SOMEONE LIVING IN AN EXTRAORDINARY PLACE AT AN EXTRAORDINARY TIME.

MAN: BAGHDAD IN THE 9th CENTURY REALLY WAS ONE OF THE GREATEST AND MOST AMAZING CITIES IN HISTORY-- PERFECTLY ROUND, 4 MILES IN CIRCUMFERENCE WITH 4 GATES, EACH AT RIGHT ANGLES TO THE OTHER.

CLEARLY THE PEOPLE WHO LIVE HERE JUST LOVED MATH AND LOVED USING MATH.

BAGHDAD IN THIS PERIOD WAS LIKE FLORENCE DURING THE RENAISSANCE OR SILICON VALLEY IN THE AGE OF THE INTERNET.

WE OFTEN TALK ABOUT THIS MYTHICAL PLACE, THE HOUSE OF WISDOM.

SOME WOULD SAY IT WAS A LIBRARY OR IT WAS A TRANSLATION HOUSE THAT BROUGHT TOGETHER THE KNOWLEDGE OF THE GREEKS, THE KNOWLEDGE OF THE PERSIANS, THE KNOWLEDGE OF THE INDIANS, ALL CONVERGING ON THIS ONE SPOT IN BAGHDAD IN THE HOUSE OF WISDOM, A CROSS FERTILIZATION OF IDEAS THAT HADN'T REALLY HAPPENED ANYTIME BEFORE THAT IN HISTORY.

♪ ONE OF THE GREATEST OF SCHOLARS OF THE MEDIEVAL TIME WAS IBN AL-HAYTHAM, WHO WAS CURIOUS ABOUT THE WORLD.

ANCIENT GREEKS COULDN'T AGREE ON THE NATURE OF LIGHT, ON HOW WE SEE.

SOME THOUGHT IT WAS LIGHT ENTERING OUR EYES, SOME THOUGHT IT WAS LIGHT BEAMED OUT FROM OUR EYES.

STEWART: IN A GROUND-BREAKING EXPERIMENT THAT WOULD PROVE WHICH IT IS, IBN AL-HAYTHAM BLOCKED A WINDOW, LEAVING A TINY HOLE TO CREATE WHAT'S KNOWN TODAY AS A PINHOLE CAMERA OR CAMERA OBSCURA.

A FAINT VIEW OF THE STREET OUTSIDE MATERIALIZED ON THE WALL OPPOSITE, PROVING THAT THE LIGHT WAS ENTERING THE ROOM FROM THE STREET, RATHER THAN BEING PROJECTED FROM HIS EYES.

BUT THERE WAS A SECOND REVELATION-- THE IMAGE WAS UPSIDE DOWN.

IBN AL-HAYTHAM REALIZED THIS MUST BE BECAUSE THE LIGHT FROM OUTSIDE WAS TRAVELING IN STRAIGHT LINES AS IT ENTERED THE ROOM.

IN FACT, ALL LIGHT BOUNCES OFF OBJECTS IN ALL DIRECTIONS IN STRAIGHT LINES.

AND ONCE YOU KNOW THAT, YOU CAN START TO MANIPULATE LIGHT AND USE IT TO REVEAL THINGS THAT WERE PREVIOUSLY HIDDEN.

AL KAHLILI: LIGHT TRAVELS IN STRAIGHT LINES.

[SPEAKS ARABIC] A PHRASE THAT WOULD BE TRANSLATED INTO OTHER LANGUAGES ALL AROUND THE WORLD.

[PEOPLE SPEAKING FOREIGN LANGUAGES] IBN AL-HAYTHAM'S THEORIES ARE DOCUMENTED IN HIS CELEBRATED "BOOK OF OPTICS," WRITTEN ALMOST EXACTLY 1,000 YEARS AGO IN THE EARLY 11th CENTURY.

ITS PAGES CONTAIN PROFOUND IDEAS ABOUT THE NATURE OF LIGHT, AND THEY EXPLAIN WHY THOSE CRYSTAL LENSES DISTORT THE LIGHT AS THEY DO.

FOR ME, IBN AL-HAYTHAM IS THE MOST SIGNIFICANT PHYSICIST OF HIS AGE.

HIS ACCURATE MODELING OF THE NATURE OF LIGHT IS A REVOLUTION OF SUCH IMPORTANCE THAT IT HAS THE POTENTIAL TO UNLOCK THE SECRETS OF THE ENTIRE COSMOS.

♪ JAMES: AL HAYTHAM'S BREAKTHROUGH WILL EXPLAIN HOW THOSE NATURAL CRYSTALS CONTROL THE LIGHT.

IT'S JUST A GLIMPSE OF HOW WE MIGHT BRING THE STARS CLOSER.

BUT TO DO THAT, WE ARE ALSO GOING TO NEED THIS.

IT'S A PLANT CALLED SAMPHIRE.

IN ENGLISH, WE ALSO CALL IT GLASSWORT.

AND THIS PLANT, REMARKABLY, HOLDS THE KEY TO THE REVOLUTION WHICH WILL ULTIMATELY BRING US THE TELESCOPE.

IN THE 13th CENTURY, VENICE IS THE WORLD CENTRE OF GLASSMAKING.

AND MOST OF THE INNOVATION WHICH TAKES PLACE HERE IS TO BE FOUND ON THIS SMALL VENETIAN ISLAND CALLED MURANO.

THE FIERCE COMPETITION OF GLASSMAKERS HERE MEANT THAT IT'S A KIND OF GEEK'S PARADISE FOR GLASS.

IT WAS THE VERY FIRST TIME PEOPLE CARED ABOUT EVERY SINGLE TECHNICAL DETAIL TO CREATE THE MOST BEAUTIFUL WORK THAT THEY POSSIBLY COULD.

MOST GLASS AT THIS TIME IS OPAQUE DUE TO BUBBLES AND IMPURITIES IN THE MIXTURE.

THE HOLY GRAIL FOR THE ARTISANS OF MURANO IS TO WORK OUT HOW TO MAKE GLASS THAT'S PERFECTLY CLEAR THROUGH CAREFUL AND METICULOUS EXPERIMENTATION WITH NEW AND OLD INGREDIENTS.

ON THE TRADE ROUTES BETWEEN EAST AND WEST, VENICE COULD EASILY SOURCE THE MAIN INGREDIENTS OF GLASS-- SILICON DIOXIDE OR SAND AND VARIOUS SODIUM AND CALCIUM MINERAL SALTS.

THE SECRET WAS THE SHIFT FROM THE USE OF MINERAL SALTS TO PLANT-BASED SALTS FROM PLANTS WHICH GROW IN SALTY ENVIRONMENTS AND A PARTICULAR PLANT THAT WE CALL SAMPHIRE, WHICH TRAPS SALT BUT ALMOST NOTHING ELSE.

AND SO, WHEN YOU BURN IT, YOU GET A VERY CLEAN, PURE MATERIAL TO ADD TO YOUR SILICA TO CREATE YOUR GLASS.

REMARKABLY, THE ASH FROM THIS MARINE PLANT SIGNIFICANTLY REDUCES THE MELTING POINT OF SILICON...

WHICH ALLOWED THEM TO KEEP IT AT A TEMPERATURE WHERE THE GLASS WAS LIQUID ENOUGH THAT ANY LITTLE BUBBLES AND IMPURITIES WOULD COME TO THE TOP AND POP.

THIS THEN WAS THE REVOLUTION WHICH WOULD ALLOW THEM TO MAKE GLASS WHICH WAS VERY CLEAR AND VERY PURE.

AND IT WAS THAT SHIFT WHICH ALLOWED THE VENETIANS TO CREATE THIS VERY, VERY TRANSPARENT CRISTALLO, THE NAME GIVEN TO CLEAR ROCK CRYSTAL BY THE GREEKS.

STEWART: THIS WAS THE FIRST TIME WE HAD MASS PRODUCED CLEAR GLASS.

THIS REVOLUTION IN GLASS TECHNOLOGY WOULD HAVE MANY CONSEQUENCES FOR SOCIETY, BUT PERHAPS THE GREATEST WAS THE WAY IT WOULD CHANGE HOW WE SAW THE WORLD.

HERE IN THE BASILICA OF SAN NICOLO IN TREVISO, JUST NORTH OF VENICE, LIES EVIDENCE OF WHAT MUST HAVE SEEMED AN ASTONISHING INVENTION AT THE TIME.

JAMES: PAINTED BY TOMMASO DA MODENA IN 1352, THE FRESCO DEPICTS A GROUP OF MONKS IN A MONASTERY SCRIPTORIUM POURING OVER THEIR MANUSCRIPTS.

BUT LOOK CLOSER.

ONE OF THEM IS WEARING SPECTACLES.

THIS EXQUISITE FRESCO FROM ALMOST 700 YEARS AGO IS THE FIRST IMAGE OF SPECTACLES IN SOCIETY.

IT ALLOWED THE MONKS TO KEEP ON READING AND WRITING FOR DECADES LONGER THAN BEFORE.

THEY DIDN'T HAVE TO ACCEPT FAILING EYESIGHT AS THE WILL OF GOD.

THEY DIDN'T HAVE TO DELEGATE THE REALLY IMPORTANT TASK OF ACQUIRING KNOWLEDGE TO YOUNGER PEOPLE.

THEY COULD JUST KEEP ON GOING, AND SO THEY DID.

WE DON'T KNOW WHO CREATED THESE FIRST GLASS LENSES.

THEY ARE LOST TO HISTORY.

BUT IT'S NO EXAGGERATION TO SAY THAT YOU CAN DRAW A DIRECT LINE FROM THESE SPECTACLES TO THE EXTRAORDINARY OPTICAL INSTRUMENTS THAT WE USE TODAY TO GAZE INTO SPACE.

STEWART: BY THE 13th CENTURY, WE HAD CLEAR GLASS LENSES.

BUT THAT ALONE WON'T BRING THE STARS CLOSER.

TO DO THAT, WOULD TAKE ANOTHER 300 YEARS AND THE BIRTH OF AN INSTRUMENT DESIGNED TO SEE MORE CLEARLY THROUGH THE FOG OF WAR.

[CANONS FIRING] IN 1608, A BRUTAL 40-YEAR CONFLICT BETWEEN THE DUTCH AND THE SPANISH WAS IN DEADLOCK.

BOTH SIDES WERE DESPERATE TO FIND A MILITARY ADVANTAGE THAT WOULD GIVE THEM THE EDGE.

[CLANG] PITTS: ENTER HANS LIPPERSHEY, A YOUNG LENS-MAKER FROM THE PROVINCIAL TOWN OF MIDDLEBURG.

HE HAS A SHOP IN WHICH HE'S BEEN USING LENSES TO MAKE EYEGLASSES FOR PEOPLE.

AND AT THIS POINT, 1608, EYEGLASS MANUFACTURING HAS BEEN GOING ON FOR ALMOST 300 YEARS.

STEWART: THE STORY HAS IT THAT ONE DAY LIPPERSHEY WAS WATCHING TWO CUSTOMERS IN HIS SHOP PLAYING WITH A PAIR OF LENSES.

PITTS: ONE HAS A CONVEX LENS, THE TYPE USED IN SPECTACLES TO MAGNIFY OBJECTS, WHICH SHE USES TO LOOK AT A WEATHER VANE.

BUT WHEN SHE MOVES THE LENS TOO FAR FROM HER EYE, THE IMAGE BLURS.

THE OTHER GIRL WAS HOLDING A CONCAVE LENS IN FRONT OF THE CONVEX LENS...

WHICH TO THEIR SURPRISE AND DELIGHT RE-SHARPENS THE MAGNIFIED IMAGE FROM THE FIRST LENS BY BENDING THE LIGHT BACK INTO A PARALLEL RAY, BRIGHTENING THE IMAGE AS IT ENTERS THE EYE.

SO WHAT HE DOES WITH THESE TWO LENSES IS HE PUTS THEM TOGETHER IN THE CORRECT ORIENTATION INSIDE A TUBE.

STEWART: AS LIPPERSHEY LOOKS THROUGH IT, HE REALIZES THAT A TOOL LIKE THIS COULD INDEED BE HELPFUL TO THE DUTCH IN BATTLE, ALLOWING THEM TO SEE THE SPANISH INVADERS FROM MUCH FURTHER AWAY THAN THEIR EYES ALONE WOULD ALLOW.

PITTS: HE QUICKLY ASKS THE DUTCH AUTHORITIES FOR AN EXCLUSIVE PATENT FOR IT, CONVINCED HE WILL MAKE HIS FORTUNE.

[SPEAKING DUTCH] PITTS: THEY SET UP A COMMITTEE TO CONSIDER THE CLAIM.

[MEN SPEAKING DUTCH] PITTS: UNFORTUNATELY, THE GOVERNMENT OFFICIALS DECIDE HIS PARTICULAR CONSTRUCTION IS NOT UNIQUE ENOUGH TO SEPARATELY AWARD HIM THE PATENT AND THE RECOGNITION AS THE INVENTOR.

SILVA: THAT ONE DECISION BY THE DUTCH AUTHORITIES ACTUALLY GAVE LIPPERSHEY'S INVENTION TO THE WORLD.

STEWART: WITH LIPPERSHEY'S ATTEMPT TO PATENT HIS INVENTION, THE SECRET OF THE SPYGLASS WAS UNLEASHED, AND THE IDEA HURTLED ACROSS EUROPE TO A MAN WE'VE ALL HEARD OF, SOMEONE WHOSE NAME WOULD BECOME SYNONYMOUS WITH THE TELESCOPE.

JAMES: IN VENICE, ITALY, TALK OF A SPYGLASS CREATED BY A CERTAIN DUTCHMAN CAME TO THE ATTENTION OF A 44-YEAR-OLD MATH TEACHER.

INSPIRED BY LIPPERSHEY'S SPYGLASS, HE STARTS TO APPLY LOGIC AND CALCULATION TO ANALYZE THESE PHENOMENA AND EXPERIMENT WITH LENSES HIMSELF.

HE QUICKLY MAKES HIS OWN VERSION OF THE SPYGLASS IN A SINGLE DAY, AND THEN WRITES TO HIS FRIENDS TO BRAG ABOUT WHAT HE'S DONE.

AND THE LETTER HE SENDS RECORDS A MOMENT THAT WILL CHANGE THE COURSE OF HUMAN HISTORY.

HIS NAME?

GALILEO.

"APPLYING MY EYE TO THE CONCAVE LENS, "I SAW OBJECTS SATISFACTORILY LARGE AND NEAR, "FOR THEY APPEARED ONE-THIRD OF THE DISTANCE OFF "AND 9 TIMES LARGER THAN WHEN THEY WERE SEEN WITH THE NATURAL EYE ALONE."

GALILEO WASN'T NECESSARILY MOTIVATED BY PURE INTELLECTUAL CURIOSITY.

HE WAS REALLY EXCITED BY FAME AND GLORY AND POWER, AND HE WAS REALLY TRYING TO SHOW OFF TO SOME OF THE RULING FAMILIES, SUCH AS THE MEDICIS OF FLORENCE AND THE DOGE IN VENICE.

GALILEO'S LIFE IS PIECED TOGETHER FROM FRAGMENTS OF HIS WRITINGS, INCLUDING, SURPRISINGLY, A SHOPPING LIST THAT HE PUT TOGETHER FOR A TRIP TO VENICE IN THE WINTER OF 1609.

THE LIST, JOTTED ON THE BACK OF A LETTER, ALLOWS HISTORIANS TO WORK OUT WHAT MATERIALS HE WAS USING TO MAKE HIS LENSES.

THE INGREDIENTS FOR ONE OF THE MOST FAMOUS TELESCOPES IN HISTORY-- HIGH-QUALITY CRYSTAL BLANKS, POLISHED GLASS, ARTILLERY BALLS AND DISH-SHAPED MOLDS, AND TRIPOLI POWDER, PITCH, AND FELT FOR THE GRINDING AND POLISHING OF THE GLASS INTO THE LENSES HE NEEDED.

ALONGSIDE THESE INGREDIENTS, THERE WERE ALSO REMINDERS TO PICK UP SOME CHICKPEAS AND LENTILS, SOME SUGAR, PEPPER, SOME CINNAMON, CLOVES, AND SOME JAM.

ALONG WITH HIS TASTE IN FOOD, THIS IS THE BEST CLUE WE HAVE TO THE CONSTRUCTION OF HIS REVOLUTIONARY TELESCOPE.

[SPEAKS ITALIAN] THIS SHOPPING LIST REALLY GIVES ME GOOSEBUMPS, NOT ONLY BECAUSE IT GIVES ME AN INSIGHT INTO GALILEO'S LIFE 400 YEARS AGO, BUT IT ALSO SHOWS HE WAS GRINDING AND POLISHING HIS OWN LENSES.

AND AS A GLASSMAKER, I CAN REALLY IDENTIFY WITH THAT.

BUT THE TELESCOPE HE WAS MAKING WITH THEM IS REALLY SOMETHING ELSE.

STEWART: THE ORIGINAL TELESCOPE THAT GALILEO BUILT WAS A VERY CRUDE INSTRUMENT, BUT THE VERSION HE MADE FOR THE MEDICI WAS REFINED, PERFECTED, AND WRAPPED IN BEAUTIFUL RED LEATHER.

IT'S KNOWN AS THE PRESENTATION TELESCOPE AND REMAINS ONE OF THE GREAT TREASURES OF ASTRONOMY.

PITTS: FOR ME, AN ENCOUNTER WITH THE PRESENTATION TELESCOPE WAS LIKE A RELIGIOUS EXPERIENCE.

STEWART: IN 2009, THE TELESCOPE WAS BROUGHT FROM ITALY TO HERE, THE FRANKLIN INSTITUTE IN PHILADELPHIA.

PITTS: WHEN I FIRST CAME INTO THE ROOM WHERE THE TELESCOPE HAD BEEN PLACED, I WAS ACTUALLY SPEECHLESS, BECAUSE HERE IN FRONT OF ME WAS AN ICONIC INSTRUMENT, AN ICONIC INSTRUMENT USED BY ONE OF THE MOST BRILLIANT SCIENTISTS EVER.

THE CHANGES IN THE UNIVERSE, THE CHANGES IN THE WAY WE PURSUE SCIENCE ARE ALL DERIVATIVE FROM THIS INSTRUMENT AS IT SITS, AND ALL I CAN DO IS STAND IN AWE THAT I'M SO CLOSE TO IT.

IT'S AS IF I CAN FEEL THE GENIUS OF GALILEO RADIATING OFF IT, AND IT'S ALMOST PALPABLE.

OF COURSE, THE ONLY WAY TO APPRECIATE GALILEO'S GENIUS IS TO TAKE A LOOK INSIDE.

OBVIOUSLY THIS ISN'T GALILEO'S TELESCOPE, BUT IT IS A VERY GOOD REPLICA.

PITTS: HERE IS THE INSTRUMENT CREATED BY THE PERSON WHO OPENED THE UNIVERSE IN A WAY IN WHICH THE UNIVERSE HAD NEVER BEEN EXPANDED BEFORE.

THE WORK THAT WAS DONE WITH THIS INSTRUMENT COMPLETELY CHANGED OUR UNDERSTANDING OF THE UNIVERSE WE LIVE IN, AND IT BEGAN TO ALTER OUR UNDERSTANDING OF OUR PLACE IN IT.

AS I LOOK AT THE WAY IN WHICH IT'S BUILT, I BEGIN TO FEEL AS IF I CAN SEE INTO HIS WAY OF THINKING.

IT'S ALMOST AS IF HE AND I ARE STANDING TOGETHER, HE SHOWING HOW HE BUILT IT, ME APPRECIATING THE INSTRUMENTATION WE HAVE TODAY TO STUDY THE UNIVERSE GIVEN WHAT HE DID SO MANY YEARS AGO.

GALILEO USED A CONVEX LENS TO GATHER LIGHT FROM WHEREVER HE POINTED THE TELESCOPE, AND HE USED A CONCAVE LENS TO THEN FOCUS THAT LIGHT SO THAT HE COULD SEE THE OBJECT CLEARLY.

GALILEO ACTUALLY SEARCHED THROUGH HUNDREDS OF PIECES OF GLASS AT THE MURANO GLASSWORKS TO GET JUST THE RIGHT PIECES THAT WERE CLOSE TO THE SHAPE HE NEEDED.

HE GROUND THE GLASS VERY CAREFULLY, THEN POLISHED EACH OF THE LENSES SO THAT IT WOULD BE JUST THE RIGHT SHAPE TO MAKE A PERFECT IMAGE, USING THESE TWO LENSES.

STEWART: BY APPLYING IBN AL-HAYTHAM'S KNOWLEDGE OF OPTICS TO LIPPERSHEY'S PATENT APPLICATION, GALILEO WAS ABLE TO IMPROVE THE SPYGLASS'S POWERS OF MAGNIFICATION ALMOST TENFOLD.

BUT IT'S WHAT HE DID NEXT WHICH WOULD MAKE HIS NAME SYNONYMOUS WITH THE INVENTION OF THE TELESCOPE.

HE HELD IT UP AND POINTED IT AT THE BIGGEST OBJECT IN THE NIGHT SKY.

PITTS: AND WHAT HE SEES WHEN HE LOOKS AT THE MOON IS ABSOLUTELY ASTONISHING.

HE TAKES INCREDIBLE NOTES AND MAKES INCREDIBLE DRAWINGS ABOUT WHAT HE SEES OF THE MOON.

AND THIS WAS A VERY BIG CHALLENGE FOR HIM AT THE TIME, BECAUSE HIS EYEPIECE DIDN'T ALLOW HIM TO SEE THE ENTIRE MOON, HE COULD ONLY SEE SMALL BITS AT A TIME.

SO HE WOULD OBSERVE, TAKE NOTES, MAKE SOME SKETCHES, AND OVER TIME, HE COULD THEN BUILD UP AN IMAGE OF WHAT THE MOON APPEARED LIKE THROUGH THE TELESCOPE, WHAT HE COULD SEE OF THE SURFACE OF THE MOON WITH ITS CRATERS AND ITS VALLEYS AND OTHER SORTS OF FEATURES.

IT'S AN ENTIRE WORLD UNTO ITSELF, AND WHAT GALILEO'S TELESCOPE IS DOING FOR US IS MAKING OBJECTS THAT HADN'T BEEN VISIBLE BEFORE NOW VISIBLE TO US.

AND WE BEGIN TO REALIZE THAT THERE ARE A GREAT MANY MORE STARS AVAILABLE THAN WE HAD EVER REALIZED IN THE PAST.

DE SILVA: WITH THE BIRTH OF THESE INSTRUMENTS, SUDDENLY EVERYONE COULD LOOK UP INTO THE SKY AND SEE IT FOR WHAT IT IS.

JAMES: HE TRANSFORMED THE WAY WE THOUGHT ABOUT TRUTH AND EVIDENCE.

WE COULD SUDDENLY SEE THINGS FOR OURSELVES.

WE NO LONGER HAD TO ACCEPT SOMEONE ELSE'S AUTHORITY FOR THAT.

PITTS: IT ALLOWS OTHER SCIENTISTS AROUND THE WORLD TO BECOME REPORTERS ON WHAT THE UNIVERSE IS DOING, WHAT NATURE IS PRESENTING US, HOW THIS UNIVERSE WORKS.

STEWART: "YOU WILL BEHOLD THROUGH THE TELESCOPE A HOST OF STARS, "WHICH ESCAPE THE UNASSISTED SIGHT SO NUMEROUS AS TO BE ALMOST BEYOND BELIEF."

GALILEO PUSHED THE LIMITS OF OUR SEEING TO THE MOONS OF JUPITER, THE RINGS OF SATURN, AND ULTIMATELY TO THE EDGES OF OUR OWN GALAXY, THE MILKY WAY.

IN THE FOLLOWING YEARS, THERE WAS AN EXPLOSION OF TELESCOPES AROUND THE WORLD AS LENSES GREW BIGGER AND MORE POWERFUL, THEN ISAAC NEWTON'S MIRRORS WERE HARNESSED TO CAPTURE EVEN MORE LIGHT, EXTENDING THE POWER OF THE TELESCOPE TO SEE EVEN DEEPER INTO THE COSMOS.

BUT THERE WAS STILL A FUNDAMENTAL LIMIT TO THE TELESCOPE.

THE HUMAN EYE WAS STILL PART OF THE TECHNOLOGY, THE ASTRONOMER LIMITED TO DRAWING WHAT THEY COULD SEE THROUGH THE EYE PIECE.

TO SEE MORE, TO CAPTURE THE UNIVERSE AS IT REALLY IS WOULD TAKE A BREAKTHROUGH IN PARIS MADE BY CHANCE THROUGH A SPILT BOTTLE OF MERCURY.

IN THE 1830s, TAKING A PICTURE WASN'T EXACTLY EASY.

POLISH A SILVER PLATE, EXPOSE IT TO IODINE TO SENSITIZE IT, AND THEN THE TRICKY PART, FIND A SUBJECT THAT'S NOT GOING TO MOVE FOR ABOUT 8 HOURS.

THAT'S HOW LONG IT TOOK TO TAKE A SINGLE PHOTOGRAPH.

ONLY THE MOST DEVOTED PIONEERS COULD BE BOTHERED TO TAKE PICTURES.

PHOTOGRAPHIC PLATES WERE NOT VERY SENSITIVE TO LIGHT.

SO UN-SENSITIVE, IN FACT, AS TO RENDER THE TECHNOLOGY OF PHOTOGRAPHY ALMOST USELESS.

BUT PARISIAN LOUIS DAGUERRE WAS DETERMINED TO CHANGE ALL THAT.

A SHOWMAN AND THEATER ENTREPRENEUR, HE WAS MOTIVATED BY THE PROMISE OF GREATER FAME AND WEALTH AND DEVOTED YEARS TO FINDING A SOLUTION.

ONE DAY HE PLACED AN ABORTED PHOTOGRAPHIC PLATE IN HIS CUPBOARD.

THE PLATE HAD BARELY BEEN EXPOSED TO LIGHT.

DAGUERRE WAS SAVING IT FOR ANOTHER TRY.

WEEKS LATER, HE PULLED IT FROM THE CUPBOARD AGAIN, ONLY TO FIND A FULLY DEVELOPED PHOTOGRAPH ON IT.

PUZZLED, HE RUMMAGED IN THE CUPBOARD AND DISCOVERED A SPLIT BOTTLE OF MERCURY.

COULD THE FUMES FROM THE MERCURY HAVE ENHANCED THE LIGHT SENSITIVITY OF THE PHOTOGRAPHIC PLATE, MEANING THAT LESS LIGHT IS REQUIRED TO TAKE A PICTURE?

TO FIND OUT, DAGUERRE PUT HIS THEORY TO THE TEST.

MAN: MY NAME IS BINH DAHN, AND I'M AN ASSISTANT PROFESSOR OF PHOTOGRAPHY AT SAN JOSE STATE UNIVERSITY.

I'M HEADING OUT INTO THE DESERT CLOSE TO WHERE I LIVE TO RECREATE DAGUERRE'S EXPERIMENT.

♪ IT IS 8:00 IN THE MORNING, AND LOUIS IS JUST ADDING THE FINAL POLISH TO HIS SILVER PLATE.

AND HE LOOKS OUT HIS WINDOW, AND HE SEES THIS BEAUTIFUL PARIS STREET SCENE-- PEOPLE WALKING DOWN THE STREET, HORSES CARRYING PEOPLE, AND WAGONS.

SO, LOUIS TAKES A LIGHT-SENSITIVE PLATE...

HE SETS UP HIS CAMERA... AND HE INSERTS HIS PLATE AND EXPOSED THE SCENE FOR 10 MINUTES.

♪ AND THEN HE CLOSED THE LENS, HE REMOVED THE PLATE, AND HE RUNS TO HIS MERCURY POT AND DEVELOPED THE PLATE.

♪ LOUIS HAS TO WAIT BEFORE HE SEES THIS IMAGE.

THERE WERE TONS OF PEOPLE WALKING THE STREET HERE, AND THEY DISAPPEAR BECAUSE THEY WERE MOVING.

THE MAN THAT WAS STANDING STILL GETTING HIS BOOTS SHINED WAS RECORDED INTO HISTORY.

EVEN DAGUERRE WAS OVERWHELMED WITH THE QUALITY OF THIS IMAGE.

AND IT'S JUST LIKE THIS SCENE HERE.

THIS IS A PICTURE I'VE JUST TAKEN.

IT'S ABOUT A MINUTE EXPOSURE.

SO THOSE WHO WERE STANDING STILL WERE RECORDED ONTO THIS PLATE HERE.

OTHER FOLKS WERE MOVING AROUND TAKING IN THE SCENE, SO THEY BECAME GHOSTLY.

LOUIS FEELS IT WAS HIS LUCKY DAY.

FINALLY, HE WAS ABLE TO RECORD A PERSON STANDING THERE.

IT'S LIKE THE MOST WONDERFUL EXPERIENCE IN LIFE TO SEE THAT YOU'RE ABLE TO RECORD HISTORY JUST AT THAT ONE MOMENT.

AND THAT, FOR ME, IS JUST, LIKE, AN AMAZING QUALITY.

IT GIVES ME TEARS JUST TO THINK ABOUT IT.

STEWART: GREAT NEWS FOR PHOTOGRAPHERS, AND FOR THE REST OF US, TOO.

BUT WHAT DOES IT HAVE TO DO WITH THE TELESCOPE?

WHEN THE TECHNOLOGY OF PHOTOGRAPHY WAS COMBINED WITH THE MAGNIFICATION CAPABILITIES OF THE TELESCOPE, WE GO FROM GALILEO'S HAND-DRAWN VIEW OF THE MOON TO THIS EXQUISITE IMAGE, THE DAWN OF MODERN ASTRONOMY.

DAHN: WITH THE ABILITY TO TRACK THE NIGHT SKY, SUDDENLY WE'RE ABLE TO SEE FURTHER INTO THE UNIVERSE THAN EVER BEFORE.

SO DAGUERREOTYPE BECAME A TOOL IN SCIENCE TO RECORD THE NIGHT SKY.

AL KAHLILI: THIS WAS A DEVELOPMENT THAT THE EARLY PIONEERS OF PHOTOGRAPHY COULDN'T POSSIBLY HAVE IMAGINED.

STEWART: PHOTOGRAPHY, COUPLED WITH THE TELESCOPE, PROVED TO BE A POWERFUL COMBINATION OF TECHNOLOGIES, CHANGING OUR VIEW OF THE COSMOS ONCE MORE.

WE'D SUCCESSFULLY BROUGHT THE STARS CLOSER, BUT HOW CLOSE WERE THEY?

ASTRONOMY NEEDED A YARDSTICK TO GIVE SCALE TO OUR VISION.

AND UNEXPECTEDLY, IT WOULD COME FROM A BOOM IN REAL ESTATE.

IN THE 1840s, NEW YORK WAS ON THE UP.

INVESTORS WERE LINING UP TO POUR MONEY INTO A BUILDING BOOM IN THE BIG APPLE.

ENTREPRENEUR CORTLAND PALMER WAS ABOUT TO MAKE A FORTUNE IN MANHATTAN.

BY THE TIME HE DIED IN 1874, HE WAS A MULTI-MILLIONAIRE AND LEFT HIS MONEY TO HIS CHILDREN.

HIS DAUGHTER, MARY ANNA PALMER DRAPER, WAS MARRIED A PIONEER OF ASTRO-PHOTOGRAPHY.

CONVINCED OF ITS POTENTIAL, SHE MADE A SUBSTANTIAL DONATION TO HARVARD UNIVERSITY FOR A MAJOR ASTRONOMY PROJECT.

WOMAN: THE HARVARD OBSERVATORY AT THE TIME WAS VERY INTERESTED IN ASTROPHOTOGRAPHY AND WANTED TO MAKE AN ENTIRE MAP OF THE SKY WITH THESE PHOTOGRAPHS THAT WERE TAKEN BOTH IN THE NORTHERN AND THE SOUTHERN HEMISPHERE.

SO NOW THAT YOU HAVE THOUSANDS OF PHOTOGRAPHS, YOU NEEDED A TEAM TO ORGANIZE THEM AND STUDY THEM.

THE HARVARD OBSERVATORY HIRED A TEAM OF WOMEN WHO WERE SPECIFICALLY STUDYING THE STARS USING GLASS PLATES, WHICH WAS VERY UNUSUAL BACK THEN BECAUSE THERE WEREN'T VERY MANY WOMEN WORKING IN THE SCIENCES.

SO THESE WOMEN DID NUMBER CRUNCHING ALL DAY, AND THAT'S WHY THEY WERE KNOWN AS THE HUMAN COMPUTERS.

♪ SOME OF THE WOMEN THAT WERE WORKING HERE, THEIR JOB WAS TO MEASURE THE BRIGHTNESS OF STARS.

SOME OF THE TOOLS THAT THESE WOMEN USED INCLUDED FLY SPANKERS, WHICH WERE TINY LITTLE PIECES OF GLASS PLATES THAT HAD DIFFERENT SIZED STARS ON THEM.

IT WAS CALLED A FLY SPANKER BECAUSE IT WAS TOO LITTLE TO DO A FLY MUCH DAMAGE.

SO AS YOU CAN SEE, THERE ARE DIFFERENT SIZED DOTS WITH NUMBERS WRITTEN NEXT TO THEM, AND THESE WERE USED AS THE STANDARD FOR MEASURING.

SO SAY YOU WANTED TO MEASURE THIS LITTLE "A" STAR HERE.

YOU COULD BRING UP YOUR FLY SPANKER AND TRY TO FIND THE BEST MATCH, AND THEN THAT WAS THE BRIGHTNESS OF YOUR STAR.

STEWART: BUT THIS IMPRESSIVE STAR CATALOGUE WAS MISSING VITAL INFORMATION-- DISTANCE.

AFTER ALL, IF TWO STARS HAVE IDENTICAL BRIGHTNESS AS SEEN FROM THE EARTH, IT DOESN'T MEAN THEY ARE THE SAME DISTANCE AWAY.

ONE STAR COULD BE QUITE DIM IN REALITY, YET QUITE CLOSE, AND THE OTHER, HUGE AND POWERFUL, BUT A LONG WAY OFF, AND STILL THEY WOULD LOOK THE SAME FROM EARTH.

WITHOUT KNOWING THE TRUE BRIGHTNESS OF A STAR, ASTRONOMERS HAD NO IDEA HOW FAR AWAY IT WAS.

BUT ONE WOMAN HAD AN IDEA.

SMITH ZRULL: HENRIETTA LEAVITT WAS KNOWN FOR BEING A VERY METICULOUS WORKER.

SHE OFTEN STAYED LATE INTO THE EVENING TO MAKE SURE THAT SHE MEASURED ALL OF THE STARS THAT SHE WANTED TO MEASURE THAT DAY.

AND I THINK THAT REALLY COMES THROUGH WHEN YOU LOOK AT HER NOTES.

THROUGH THIS VERY METICULOUS APPROACH, SHE WAS ABLE TO HAVE A BREAKTHROUGH THAT IS NOW KNOWN AS THE LEAVITT LAW.

STEWART: LEAVITT'S LAW IS A LITTLE COMPLEX, BUT IT'S THE KEY TO UNLOCKING THE UNIVERSE.

THERE ARE SOME STARS THAT REGULARLY GET SLIGHTLY DIMMER OVER TIME BEFORE RETURNING TO THEIR FORMER GLORY.

THESE VARIABLE STARS HAVE A KIND OF HEARTBEAT OF BRIGHTNESS.

LEAVITT STUDIED A GROUP OF THEM AND DISCOVERED THAT THE DIMMER ONES BEAT QUICKLY.

THE ONES THAT ARE BRIGHTER BEAT MORE SLOWLY.

IT'S AS IF THE BIG, BRIGHT STARS HAVE A SLOW HEARTBEAT AND THE SMALLER, DIMMER ONES, A FAST ONE.

FIND A VARIABLE STAR ANYWHERE IN THE SKY AND ITS HEARTBEAT GIVES ITS TRUE BRIGHTNESS AWAY.

NOW ITS DISTANCE CAN BE MEASURED BY HOW BRIGHT IT APPEARS FROM THE EARTH.

SMITH ZRULL: AND BAM, YOU HAVE A YARDSTICK FOR ASTRONOMERS SO THAT THEY COULD START TO MEASURE DISTANCES IN SPACE IN WAYS THAT THEY COULDN'T DO BEFORE.

FOR THE FIRST TIME, ASTRONOMERS WERE ABLE TO UNDERSTAND EXACTLY HOW LARGE OUR GALAXY IS.

SO THIS 19th-CENTURY PROPERTY BOOM IN NEW YORK HAD ACCIDENTALLY UNLOCKED THE SCALE OF THE UNIVERSE.

HENRIETTA LEAVITT'S DISCOVERY ALLOWED US TO MEASURE DISTANCES TO STARS VERY ACCURATELY.

FOR THE FIRST TIME, WE COULD REALLY CHART THE COSMOS AND CREATE A MAP OF THE VISIBLE UNIVERSE.

STEWART: BY THE 1920s, WE COULD SEE THE STARS BETTER THAN EVER BEFORE.

AND WE NOW WE KNEW HOW FAR AWAY THEY WERE, TOO.

BUT WAS THIS THE ENTIRE UNIVERSE OR WAS THERE MORE OUT THERE?

TANTALIZINGLY, THERE ON OUR PHOTOGRAPHIC PLATES, RIGHT AT THE LIMITS OF WHAT OUR TELESCOPES COULD RECORD AT THE TIME, ARE A SERIES OF CLOUDY PATCHES, LIKE THIS ONE, KNOWN THEN AS THE ANDROMEDA NEBULA.

THE EXACT NATURE OF THESE CLOUDY PATCHES WAS THE BURNING QUESTION OF THE AGE, THE SO-CALLED GREAT DEBATE, BECAUSE THE ANSWER TO THIS QUESTION WOULD REVEAL A FUNDAMENTAL TRUTH ABOUT OUR UNIVERSE.

PITTS: IF YOU LOOKED AT THE EVIDENCE THAT COULD BE GATHERED THROUGH TELESCOPES AT THE TIME, THE DEBATE, OF COURSE, SURROUNDED THIS IDEA OF WHETHER THERE WERE A NUMBER OF GALAXIES LIKE OUR GALAXY.

AND THIS DEBATE RAGED ON.

STEWART: WERE THESE BLURRY PATCHES OF LIGHT NEARBY CLUMPS OF GAS AND DUST OR WERE THEY A MUCH MORE DISTANT COLLECTION OF STARS, GALAXIES IN THEIR OWN RIGHT?

TO ANSWER THIS QUESTION, PHILANTHROPISTS FUNDED THE CONSTRUCTION OF AN EXCITING NEW TELESCOPE, THE LARGEST TELESCOPE AT THE TIME.

IT WAS TO BE BUILT ON MOUNT WILSON, 5,700 FEET ABOVE THE CITY OF LOS ANGELES.

TRANSPORTING THE GIANT 8-FOOT MIRROR UP THE MOUNTAIN PUSHED THE CONSTRUCTION TEAM TO THEIR LIMITS.

OPERATING THE TELESCOPE WOULD PROVE EVEN HARDER.

PITTS: EVEN WITH WHAT WAS, FOR THAT TIME, A VERY MODERN AND HIGHLY-CAPABLE INSTRUMENT, THE 100-INCH HOOKER REFLECTOR, IT STILL WAS AN INSTRUMENT THAT YOU HAD TO WORK REALLY HARD TO OPERATE IN A WAY TO BRING YOU THE INFORMATION YOU NEEDED.

IT WASN'T AS THOUGH YOU COULD SIMPLY PUT A CAMERA ON THE TELESCOPE, TAKE A PICTURE, AND YOU'D HAVE YOUR INFORMATION.

OBJECTS THAT WERE OUT THERE, LIKE THE GREAT NEBULA IN ANDROMEDA, WERE STILL VERY FUZZY, CLOUD-LIKE OBJECTS.

SO YOU COULDN'T JUST TAKE A PICTURE, AND THAT WOULD BE THE END OF YOUR WORK.

IN FACT, YOU HAD TO PAINSTAKINGLY TAKE PHOTOGRAPHS, NIGHT AFTER NIGHT AFTER NIGHT AFTER NIGHT.

THAT TASK WOULD FALL TO A 29-YEAR-OLD ASTRONOMER, EDWIN HUBBLE.

HUBBLE WAS A VERY UNUSUAL INDIVIDUAL.

AND WE CAN SEE THAT IF WE LOOK AT HIS EARLY HISTORY.

BEFORE HE BECAME AN ASTRONOMER, HE WAS A VERY ACCOMPLISHED ATHLETE.

HE WAS A BOXER.

HE WAS A BASEBALL PLAYER.

HE DID ALL SORTS OF ATHLETIC PURSUITS, BUT HE WANTED TO BE THE WINNER.

HE NEEDED TO BE THAT PERSON, BECAUSE THIS WORK REQUIRED SUCH ATTENTION TO DETAIL, AND HE WANTED TO BE AT THE HIGHEST LEVEL OF ACCOMPLISHMENT IN THIS FIELD.

STEWART: IN 1923, HUBBLE BEGAN THE PAINSTAKING TASK OF REPEATEDLY PHOTOGRAPHING THE ANDROMEDA NEBULA.

PITTS: HOOKER MIGHT HAVE BEEN THE BIGGEST AND BEST INSTRUMENT AT THE TIME, BUT TRACKING TINY PATCHES OF THE NIGHT SKY WITH ACCURACY AS THE EARTH TURNS IS STILL A DAUNTING CHALLENGE.

HUBBLE HAD TO ACTUALLY BE IN THE OBSERVATORY AT THE TELESCOPE COLLECTING THE DATA, TRYING TO GATHER INFORMATION THAT HAD NEVER BEEN COLLECTED BEFORE, AND THERE WERE SO MANY DIFFERENT KINDS OF ROADBLOCKS HE HAD TO OVERCOME IN ORDER TO MAKE THIS HAPPEN.

NOT ONLY DO YOU HAVE TO MOVE THE TELESCOPE ITSELF, BUT YOU ALSO HAVE TO MOVE THE DOME SO THE SLIP LINES UP PERFECTLY, AND THE WHOLE BUILDING HAS TO BE IN ALIGNMENT WITH THE TELESCOPE TO WORK.

AND IT WASN'T SIMPLY PRESSING A BUTTON.

THIS WAS A VERY MANUAL OPERATION.

IN SOME INSTANCES, AN EXPOSURE MIGHT LAST SEVERAL NIGHTS, WHICH MEANT THAT YOU HAD TO REPOSITION THE TELESCOPE TO EXACTLY THE RIGHT PLACE THE NEXT NIGHT THAT YOU WANTED TO TAKE AN EXPOSURE, UNTIL YOU BUILT UP ENOUGH OF AN IMAGE ON A PLATE TO GIVE YOU SOME DATA THAT YOU COULD THEN USE.

AS AN ASTRONOMER WHO'S SPENT MANY A COLD NIGHT AT A TELESCOPE GATHERING DATA, I HAVE A DEEP RESPECT FOR HIS WORK.

EACH IMAGE HE GATHERED WAS HARD WON, BECAUSE HE HAD TO CONSTANTLY RE-ADJUST THE TELESCOPE TO KEEP IT ACCURATELY TRACKING.

IT TOOK TIME AFTER TIME AFTER TIME OF HIM PHOTOGRAPHING OVER AND OVER AND OVER AGAIN TO GET THE RIGHT RESOLUTION, TO GET EVERYTHING NICE AND STABLE TO DELIVER WHAT HE NEEDED.

WITH EVERY IMAGE HE GATHERED, THE UNIVERSE GOT BIGGER.

♪ IN THIS DRAWER ARE THE HUNDREDS, THE THOUSANDS OF PLATES THAT EDWIN P. HUBBLE WORKED SO HARD TO COLLECT.

AND GETTING THAT FIRST PLATE WAS INCREDIBLY IMPORTANT BECAUSE HE CAN REACH DEEPER INTO THE UNIVERSE THAN ANYONE HAS EVER REACHED BEFORE.

THOSE RESULTS WERE ABSOLUTELY ASTOUNDING, THE FIRST PROOF THAT INSTEAD OF SEEING A NEBULA, IT'S REALLY A GALAXY, A COLLECTION OF STARS.

THAT PLATE SETTLED THE DEBATE, THE ANDROMEDA NEBULA WAS MADE OF STARS.

BUT THIS RAISED ANOTHER QUESTION.

WAS IT PART OF OUR GALAXY?

TO FIND OUT, HUBBLE NEEDED TO FIND A VARIABLE STAR TO APPLY HENRIETTA'S MEASURING STICK.

SO ONE IMAGE ISN'T GOING TO DO IT FOR HIM.

HE HAS TO TAKE MULTIPLE IMAGES OVER AND OVER AND OVER AGAIN SO THAT HE CAN SEE THE VARIABILITY OF THAT PARTICULAR STAR, AND HE CAN IDENTIFY THAT ONE STAR OUT OF ALL THE OTHER STARS THAT ARE FOUND IN THAT GALAXY.

AND HERE IT IS.

THIS IS THE EXTRAORDINARY PLATE IN WHICH HUBBLE CAPTURED THAT MEASURING STICK HE NEEDED.

IN FACT, UP HERE IN THE TOP CORNER, YOU CAN SEE WHERE HE SCRIBBLED IN RED LETTERS "V-A-R," MEANING VARIABLE.

THIS WAS THE PLATE THAT PRESENTED ALL THE INFORMATION HE NEEDED TO UNDERSTAND THE TRUE NATURE OF THE UNIVERSE.

STEWART: USING LEAVITT'S LAW TO CALCULATE THE DISTANCE, IT WAS CLEAR THAT ANDROMEDA WAS VERY, VERY FAR AWAY.

WHAT HE WAS LOOKING AT WAS TRULY REVOLUTIONARY.

PITTS: WHAT WAS BEING SEEN WERE GALAXIES JUST LIKE OURS.

HUBBLE DIDN'T JUST FIND A BUNCH OF NEW STARS, HE FOUND AN ENTIRELY NEW GALAXY.

IN SEEING THE ANDROMEDA GALAXY FOR WHAT IT WAS, HUBBLE REALLY CHANGED HOW WE PERCEIVED OUR PLACE IN THE UNIVERSE.

STEWART: NOT CONTENT WITH DISCOVERING THAT ANDROMEDA IS A DISTANT GALAXY, HUBBLE DEVOTED THE FOLLOWING YEARS TO PHOTOGRAPHING MORE AND MORE GALAXIES THROUGH THE GIANT TELESCOPE.

AND WHAT HE DISCOVERED WAS EVEN MORE ASTOUNDING.

EVERY GALAXY HE EXAMINED APPEARED TO BE MOVING AWAY FROM US AT A TREMENDOUS SPEED.

AND THE MORE DISTANT THE GALAXY, THE FASTER IT WAS RECEDING.

ASTRONOMERS HAD ALWAYS THOUGHT OF THE UNIVERSE AS STATIC, BUT WHAT EDWIN HUBBLE REVEALED WAS THAT THE UNIVERSE IS EXPANDING.

WHAT'S MORE, IF WE RUN THE COSMIC CLOCK BACKWARDS, EVERYTHING WOULD HAVE EMERGED FROM A SINGLE POINT OF INFINITE DENSITY, MARKING THE BEGINNING OF THE UNIVERSE, THE BIG BANG.

IT'S SUCH A PROFOUND IDEA THAT IT TRIGGERED A WHOLE NEW REALM OF COSMOLOGICAL INQUIRY.

BUT NO MATTER HOW ADVANCED TECHNOLOGY BECAME, TELESCOPES WERE LIMITED BY BEING ON EARTH, PEERING OUT THROUGH AN ATMOSPHERE THAT DISTORTS OUR VIEW OF THE NIGHT SKY.

IT WOULD TAKE ANOTHER REVOLUTION TO PLACE TELESCOPES IN A PLACE WHERE THEY COULD TRULY SEE THE UNIVERSE.

THE WORLD'S FIRST MAJOR SPACE-BASED OPTICAL TELESCOPE WAS LAUNCHED IN 1990, AND IT WAS NAMED AFTER THE MAN WHO INSPIRED IT.

ABOVE THE ATMOSPHERE AND WITH A CLEAR VIEW OF THE SKY, THE HUBBLE SPACE TELESCOPE COULD TAKE THE LONGEST TIME EXPOSURES IN THE HISTORY OF ASTRONOMICAL PHOTOGRAPHY, ATTEMPTING TO DO WHAT OUR ANCIENT ANCESTORS COULD ONLY HAVE DREAMED OF-- TO SEE THE FURTHEST REACHES OF THE UNIVERSE IN EXQUISITE DETAIL.

BRETT SALMON AND DAN COE ARE TWO OF THE LUCKY ASTRONOMERS AT THE SPACE TELESCOPE SCIENCE INSTITUTE WHO GET TO WORK WITH HUBBLE EVERY DAY.

SALMON: WE WANTED TO USE HUBBLE TO LOOK INTO THE DEEPEST PARTS OF THE UNIVERSE, AND SO ONE OF THE SIMPLEST IDEAS WAS TO JUST INVEST A LARGE AMOUNT OF HUBBLE'S TIME TO STARE AT THIS BLACK PATCH OF SKY FOR A REALLY LONG TIME.

STEWART: IN 1995, THE INSTITUTE'S DIRECTOR ROBERT WILLIAMS DECIDED TO DO THIS EXPERIMENT DURING THE CHRISTMAS VACATION.

OVER 10 DAYS, HUBBLE COLLECTED 342 SEPARATE EXPOSURES, ADDING UP TO MORE THAN 100 HOURS OF OBSERVATION TIME, THE LONGEST EVER ATTEMPTED.

IT WAS A GAMBLE.

NO ONE KNEW WHAT TO EXPECT.

COE: THE FIRST TIME THAT HUBBLE LOOKED AT A BLANK FIELD, IT WAS A BIT RISKY.

SOME PEOPLE THOUGHT THERE MIGHT NOT BE ANYTHING THERE IN A BLANK PATCH OF SKY.

BUT THAT RISK WAS REWARDED.

IN THAT SMALL PATCH OF SKY, ABOUT THE SIZE OF A GRAIN OF SAND AT ARM'S LENGTH, WE SAW THOUSANDS OF GALAXIES.

SALMON: THE HUBBLE DEEP FIELD IS SURPRISING TO EVERYONE BECAUSE ALMOST EVERYTHING IN THAT IMAGE IS A GALAXY.

COE: JUST IN THAT VERY SMALL PATCH OF SKY, THERE ARE THOUSANDS OF GALAXIES.

STEWART: IT WAS SUCH A SUCCESS THAT SINCE THEN, THE TECHNIQUE HAS BEEN TRIED AGAIN AND AGAIN, AND EACH TIME WE SEE EVEN MORE GALAXIES.

COE: SO OVER THE ENTIRE SKY, THERE ARE PROBABLY TRILLIONS OF GALAXIES.

AND EVERY GALAXY HAS BILLIONS OF STARS IN IT, EACH STAR BEING LIKE OUR SUN, MORE OR LESS.

AND SO, THE UNIVERSE IS SO VAST, AND IT REALLY MAKES YOU FEEL INSIGNIFICANT IN A WAY, BUT WE'RE ALSO VERY SPECIAL, THAT WE'RE ABLE TO BUILD TELESCOPES TO OBSERVE ALL OF THOSE GALAXIES.

STEWART: THIS DISCOVERY, THAT SO MANY GALAXIES EXIST, HAS CHANGED OUR PERSPECTIVE ON OUR PLACE IN THE UNIVERSE ONCE AGAIN.

IT'S IMPOSSIBLE TO LOOK AT THESE DEEP FIELD IMAGES AND NOT FEEL INTIMIDATED BY THE EXTRAORDINARY DEPTH TO THE COSMOS.

THE GALAXIES WE'VE NOW MAPPED ACROSS THE UNIVERSE FORM THEIR OWN WEBS OF MATTER, THE LARGEST STRUCTURES EVER DISCOVERED.

COE: THIS TYPE OF WORK IS VERY EXCITING.

YOU'RE DISCOVERING THE MOST DISTANT GALAXIES KNOWN THAT PEOPLE HAVEN'T SEEN BEFORE.

HERE'S THE CANDIDATE THAT WE WERE TALKING ABOUT.

KIND OF ZOOM IN HERE.

COE: AND SO, WE'RE REALLY LOOKING FORWARD TO THE JAMES WEBB SPACE TELESCOPE STARTING TO WRITE THAT FIRST CHAPTER OF COSMIC HISTORY FOR US.

STEWART: WITH THE NEW JAMES WEBB SPACE TELESCOPE, WE SHOULD BE ABLE TO SEE AS FAR AS PHYSICS ALLOWS.

PITTS: IT'S A WONDER THAT WE, HUMANS ON THIS LITTLE PLANET, OVER IN A CORNER OF THE UNIVERSE SOMEPLACE, CAN UNDERSTAND IT.

THAT, TO ME, JUST IS THE MOST AMAZING THING.

STEWART: ONCE MORE, WE'RE ON THE BRINK OF ANOTHER REVOLUTION IN OUR UNDERSTANDING OF THE COSMOS.

THIS IS OUR LATEST LEAP IN THE STORY OF THE TELESCOPE, AN INVENTION THAT'S ULTIMATELY GIVEN US A GLIMPSE AT THE EDGES OF THE UNIVERSE, AND IN DOING SO, A NEW PERSPECTIVE ON OUR PLACE WITHIN IT.

THANKS TO A TECHNOLOGY FROM WARFARE WHICH TODAY LIFTS OUR STATE-OF-THE-ART TELESCOPES HIGH ABOVE THE ATMOSPHERE, TO THE ACCIDENTS AND EXPERIMENTS IN CHEMISTRY, WHICH GAVE US CLEAR GLASS AND PHOTOGRAPHY.

THE MARVEL OF MEDIEVAL MATHEMATICS, AND THE HUNTER GATHERERS WHO FIRST ATTEMPTED TO BRING THE STARS CLOSER, TODAY WE ALL HAVE A VIEW OF THE UNIVERSE WHICH CONNECTS US TO A COSMOS FROM WHICH WE HAVE ALL COME.

PERHAPS THIS IS THE REAL GIFT OF THE REVOLUTION THAT HAS GIVEN US THE TELESCOPE.

STEWART: NEXT TIME ON "BREAKTHROUGH," THE STORY OF HOW WE TOOK TO THE SKY, A TALE FULL OF EXTRAORDINARY ACCIDENTS AND BIZARRE CONNECTIONS.

IT INVOLVES THE ILL-FATED PENNY-FARTHING BICYCLE AND SEVERAL TRIPS TO THE BEACH, A VISIONARY STUDENT, AND A LEGENDARY GENIUS, TO GIVE US OUR GREAT SUPERPOWER-- THE ABILITY TO FLY.

ANNOUNCER: TO ORDER "BREAKTHROUGH: THE IDEAS THAT CHANGED THE WORLD" ON DVD, VISIT SHOPPBS, OR CALL 1-800-PLAY-PBS.

THIS PROGRAM IS ALSO AVAILABLE ON AMAZON PRIME VIDEO.

♪