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00:00There are moments in astronomy that have transformed our understanding of
00:08the skies. What he discovers are the laws of planetary motion. Flashes of
00:15inspiration from the heavens. Turning points. They caused a shift in the very
00:22way we think about the cosmos. Points come along and say these things move in
00:28ellipses. Boom. That's when the model worked. They have changed our perception of the earth
00:37and our place in the universe. These stars were at least ten times further away than
00:44any of the stars that we knew were in our galaxy. Our imaginations can now run wild.
00:52There might be aliens out there who might actually come and devour us. In a universe of endless
01:01possibilities. All of a sudden, wow. Our universe might be much, much, much larger than
01:09we originally thought.
01:10This is the story of humankind's obsession with the skies and the ways our ancestors made
01:22sense of the universe. This is the story of how we move from a world ruled by supernatural
01:31beings to a cosmos revealed by scientific astronomy. This is the story of seeing other worlds and
01:43finding our true place among them. This is the story of our ancient skies.
01:52Over the course of millennia, we shifted from a mythical cosmos governed by supernatural beings to a rational
02:17universe where science and math ruled supreme. We saw our flat earth transformed into a sphere
02:26and imagined it at the center of everything, orbited by the sun, moon, planets, and all the stars in the sky.
02:36Then, in 1543, an astronomer named Nicholas Copernicus proposed that the sun, not the earth, was at the center of the cosmos.
02:52Even in this new model, everything was still contained inside concentric crystalline spheres.
03:01But that idea was about to come crashing down.
03:13In 1577, a great comet passed close to the earth.
03:20It stayed in the sky for over two months.
03:24The comet of 1577 was remarkable in that we have observations of it from around the world, from Peru, Japan, Italy, Turkey.
03:36And so it's a moment which we can fix in time.
03:43People believed comets to be great balls of fire and different cultures told stories depicting them as different creatures.
03:50Australian Aboriginal peoples believe them to be the fearsome evil spirit of a rainbow serpent.
04:05Other cultures imagined comets as fire-breathing dragons.
04:08In most cases, they were seen as omens, bringing bad luck.
04:15But the great comet of 1577 would bring about one of the greatest transformations in astronomy for 1400 years.
04:23In the kingdom of Denmark was a man who felt inspired to take astronomy to great new heights.
04:38He was a maverick sky watcher who wore a brass nose after his real one was cut off in a duel.
04:53He lived in a castle and had his own personal court jester.
04:59His name was Tycho Brahe.
05:03Tycho Brahe was the astrologer to the king of Denmark.
05:08And so accuracy was at a premium.
05:12At this time, astrology and astronomy were still inseparable.
05:17And people believed that a knowledge of how the skies worked could help to predict events on Earth.
05:24He wanted to understand the workings of the universe to make his astrological predictions more exact.
05:33So he's also extremely famous as an astronomer.
05:39Just as with everything else in his life, when it came to astronomy, Brahe didn't do things halfway.
05:47Tycho Brahe sets up the world's greatest observatory on his island of Venn.
05:54I think it's 1% of the operating budget of the crown of Denmark is dedicated to funding Tycho's island.
06:01With almost limitless funds provided by the king of Denmark, Brahe set to work filling his observatory with the most advanced astronomical instruments yet seen.
06:13These are instruments before the telescope.
06:17So he's created huge sextants and quadrants that take multiple people to manage and record the data.
06:25His invention of instruments allowed him to measure with the greatest ever precision the positions of the planets and stars in the night sky.
06:35But it wasn't just planets and stars that Brahe was interested in.
06:42Something else he saw was about to change our understanding of the universe forever.
06:48On November 13th, 1577, Brahe spotted the Great Comet from his observatory.
07:05He set to work plotting its course.
07:08His calculations showed that the Great Comet was passing through the orbit of Venus.
07:15But according to the accepted wisdom, this shouldn't be possible.
07:24At this time, people believe that everything in the cosmos was contained within concentric crystalline spheres.
07:32The idea of the crystalline spheres isn't just a metaphor for people at this time.
07:39People thought that they actually were crystalline spheres.
07:45Brahe reasoned that it should have been impossible for the comet to follow this trajectory.
07:51The crystalline spheres ought to have stopped it in its tracks.
07:55He realized that the only way for the Great Comet to follow this path would be if the crystalline spheres simply did not exist.
08:08In effect, the comet of 1577 and Tycho's interpretation shatters those crystalline spheres.
08:13After 2,000 years, the crystalline spheres were gone.
08:28And with the idea of a sun-centered universe taking hold, the door was opened to a whole new era of astronomy.
08:39But there was still one ancient idea that remained.
08:49The belief that everything in the heavens moved in perfect circles.
08:56That was until the arrival of a new star astronomer.
09:03Johannes Kepler was a German astronomer and mathematician who worked in Prague.
09:23He had been inspired to study astronomy as a child when he witnessed Great Comet of 1577.
09:32Kepler believed that God had created the universe and therefore, by watching the movements of the stars and planets, you would get a glimpse into the unfolding of God's plan.
09:46He decided that the whole of classical and medieval astrology should be discarded and we should begin again with a new reformed astrology based completely on empirical observation.
10:01Most astronomers still believe that everything in the universe moved in perfect circles.
10:08But this theory couldn't explain the way people saw the planets moving in the skies.
10:15So for over 1,500 years, they used an idea called epicycles, where planets moved in orbits that looked like spiraling loops.
10:32That has worked really well for a long time, and yet it's messy, these epicycles.
10:38It's really hard to work with.
10:43Kepler wanted to simplify this model of the cosmos.
10:48And with access to Tycho Brahe's observations, he began to recalculate the orbits of the planets.
10:57Kepler's great contribution is that he takes Tycho Brahe's numbers, Tycho Brahe's very precise data, and he starts calculating.
11:09As 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.
11:21The planets didn't move in circles, they moved in ellipses.
11:28To get an elliptical orbit, you take a circular orbit and you essentially squash it on two sides, so it's more egg-shaped.
11:39This is a huge change.
11:41Planets don't appear to be making exact circles.
11:45In fact, what he discovers are the laws of planetary motion.
11:52Once you had Kepler come along and say, you know what? These things move in ellipses.
11:57Boom! That's when the Copernican model worked.
11:59Kepler published his new laws of planetary motion in 1609 in a book called the Astronomia Nova.
12:09He had come up with a description of the motions of planets, which eliminated the need for epicycles.
12:17But it was only a theory. The one man who would finally provide proof would also discover the force that held the universe together.
12:31And become arguably the most famous scientist of all time.
12:44In 17th century England, Isaac Newton was a man determined to rewrite just about every textbook going.
12:51He was a genius who turned his hand to philosophy, science and math. Even to alchemy.
13:03We might today remember him as being a physicist, as being an astronomer, as being a mathematician.
13:08At the time, he was working in the context of natural philosophy, which was a more holistic way of understanding the universe.
13:14Newton was a deeply religious man who believed that science could reveal God's master plan for the universe.
13:26He was also a radical.
13:31For thousands of years, the assumption had been that things in space worked very differently than how they did on Earth.
13:38But Newton had other ideas.
13:41He 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.
13:57Isaac Newton argues that the whole universe is governed by a single law, the law of gravity.
14:13Gravity is one of the four fundamental forces of nature.
14:17And it's the force of attraction that any objects that have mass will feel towards each other.
14:22Newton needed a way to prove the theory that gravity worked the same everywhere in the universe.
14:33And in 1680, proof arrived from outer space.
14:38The comet of 1680 was incredibly bright and you could see it during the daytime.
14:45And it becomes a topic of dispute, especially among Newton's circle, because people see the comet pass in 1680.
14:50And then another comet comes back in 1681.
14:55And there's a question, is this one comet or is this two comets?
14:59Newton realized that his theory of gravity held the answer to this question.
15:06In his mind, the comets of 1680 and 1681 had to be one in the same.
15:12He argued that it had journeyed through the solar system once before the sun's gravity had swung it back again.
15:21When people discover that it's one comet, they understand that it's gone around the sun and is coming back around the other side of its orbit.
15:29Newton realized that the gravity of the sun had caused the comet to follow an elliptical path through the cosmos.
15:40So could gravity also support the theory that the planets moved on elliptical orbits?
15:47Imagine that I'm throwing a ball to you, which is a newly formed planet with some initial velocity.
15:57It would go in a straight line towards you.
15:59But if we then switched on in the center of a room, some attractive force, so that would be the gravity from the sun.
16:10The newly formed planet wouldn't go straight to you and it wouldn't go straight into the center of the sun either.
16:17It would form a curved orbit. And that would be elliptical.
16:26Gravity powered elliptical orbits.
16:30And it was the glue that held the universe together.
16:35We finally had an accurate model of our solar system.
16:41Well, almost.
16:43But before we could extend our knowledge of the heavens any further, we had an important earthbound problem to solve.
16:56Beginning in the 16th century, vast colonial empires began to spread out across the planet.
17:03There was a rush to conquer and exploit the wealth of newly discovered territories.
17:08For seafaring nations like the English, Spanish and French, being able to navigate accurately and safely was essential.
17:21There's an example of a ship that was lost at sea trying to figure out where they actually were in the wide open ocean.
17:29And meanwhile, hundreds of crew members died of scrutiny.
17:31This actually is a life and death situation.
17:35In 1707, a navigational error caused a fleet of ships to crash into the Isles of Scilly off the southwest coast of England.
17:46It was one of the deadliest maritime disasters in history.
17:51Up to 2,000 sailors lost their lives.
17:58This became public outcry, right, about this.
18:02This isn't okay to have people going out and doing commerce for England and dying on the way back.
18:08Although sailors could use the sun and stars as a compass, it wasn't enough just to know what direction they were going.
18:23Plotting their exact position was a problem.
18:27They could use the pole stars to work out latitude, their position north or south.
18:34At night, you just measure how high Polaris is off the horizon, and to within a degree or so, that's your latitude.
18:42But to pinpoint their exact position, mariners also needed to know their longitude, their position east or west.
18:51This was almost impossible.
18:55Because the Earth is spinning, there's no distinguishing characteristic on it, east and west.
19:01So really, you just have to make one up and say arbitrarily, this spot becomes zero degrees longitude.
19:07You can do that.
19:09But if you move away from it, then it becomes very, very difficult to know exactly what your longitude is.
19:14As far back as the second century BC, the Greek mathematician Hipparchus believed that the answer lay in the skies.
19:25He proposed that if you could compare the solar time where you were now with the time where you would set off,
19:34then you could calculate your position either east or west.
19:38Although this theory was sound, there was a problem with it.
19:42In the 2,000 years since Hipparchus, no one had invented a clock that could work accurately at sea.
19:52For most of history, keeping time used some sort of device like, say, a pendulum.
19:58Well, 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.
20:06If you put something like this on a boat, these are famous for rocking.
20:09So as the sea is moving up and down, that's affecting the motion of the pendulum.
20:13It's basically impossible to keep time that way.
20:16What was needed was a new kind of clock.
20:19It would come not from a clock maker, but from a carpenter.
20:26In 1714, with mounting pressure from the maritime community, the British government passed a law called the Longitude Act.
20:42They put up a reward equaling almost two million dollars in today's money to anyone who could crack the problem of calculating longitude at sea.
20:54John Harrison was a woodworker from the north of England with a passion for repairing clocks.
21:04He 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.
21:15Here to my left is John Harrison's first sea clock, which we now call H1.
21:24It has a number of innovations that Harrison himself came up with.
21:28Instead of a pendulum, it has these wonderful dumbbells.
21:32And the idea here is that anything that affects one will affect the other in the opposite direction.
21:38So any errors caused by motion will counteract each other.
21:43The H1 worked at sea, and it kept time to within three seconds a day.
21:50But Harrison still wasn't satisfied.
21:53He began to realize that actually a sea clock was not going to be the solution.
21:58So he went back to the drawing board.
22:04In the early 1750s, he began looking at watches as the solution.
22:10The watch that Harrison eventually came up with was the H4.
22:15What it came up with was a design which had a large, heavy balance wheel, which oscillated very quickly.
22:21And his thinking was that the ship moves in a certain way fairly slowly.
22:27And with this very quickly moving high energy system, it would not be affected by the kinds of motion that would affect the ship.
22:36Harrison's H4 prototype was put to the test in 1764.
22:41And it worked.
22:47Finally, we had the technology to harness the time given to us by the sun.
22:53And take it with us to calculate longitude at sea.
22:57By the middle of the 18th century, technology was also helping us to make great leaps forward in astronomy.
23:17Since the invention of the telescope, we had been able to look deeper and deeper into the cosmos.
23:25The telescope is the first scientific instrument that extends the human senses.
23:34And as telescopes got bigger and better, they revealed more and more of what lay in our solar system.
23:41William Herschel was born in Germany.
23:49He came to England to be a musician in England.
23:52He moved to the city of Bath, where he also developed a deep and profound interest in astronomy.
24:00He worked and collaborated with his sister Caroline, who herself also became a distinguished astronomer.
24:07The Herschels built a series of increasingly powerful telescopes.
24:18With these, they observed and meticulously catalogued thousands of stars.
24:28In 1781, as he gazed at the night sky, William noticed an object that grabbed his attention.
24:40He 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.
24:50They are responsible for the discovery of the planet Uranus.
25:01This was an earth-shattering discovery.
25:06For millennia, we had believed there were only five planets.
25:12Now, with the discovery of Uranus, we have a sixth.
25:16William dedicated this new planet to King George III.
25:25The Jester won Herschel royal favor.
25:28And he was made the King's astronomer.
25:30This meant that Herschel now had the funds and the freedom to build even bigger and better telescopes than ever before.
25:49And in 1789, he completed a telescope that would be his crowning achievement.
25:55This is the last remaining quarter of William Herschel's largest telescope, the 40-foot reflector, that was built between 1785 and 1789.
26:07At the end here, you'd have the mirror, which he polished and shaped himself.
26:11It would take many, many hours of work to achieve that.
26:14And 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.
26:25This was certainly the largest telescope in the world at that time.
26:31When Herschel turned this giant telescope towards the skies, he made even more new discoveries.
26:38So when William Herschel first used this telescope in 1789, he discovered the sixth and seventh moons of Saturn, Enceladus and Minus.
26:47So that was a really important moment in this telescope's history.
26:49Herschel's 40-foot telescope became a global symbol of scientific progress.
26:57It opened the door to a new era of astronomical exploration.
27:02And as we study the cosmos in unprecedented detail, our imaginations began to run wild.
27:11One 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.
27:23And this reaches a peak in the 19th century with Jules Verne.
27:36Jules Verne was a highly prolific writer and many of his works contained lots of really important descriptions of technology.
27:48Sometimes very futuristic technology that many argue is actually very forward thinking.
27:54In 1865, Verne published his book, From the Earth to the Moon.
28:02Jules Verne writes about this 19th century American gun club.
28:08And they're basically going to build a huge gun and fire three of the members into space and land on the moon.
28:14An awesome silence hung over the whole scene.
28:21And everyone realized that the daring explorers inside the projectile were also counting the seconds.
28:2938, 39, 40, fire!
28:35Although it was a work of fiction, Verne's novel became an inspiration to scientists all over the world.
28:45The really kind of important thing here is that it's very highly researched.
28:51Jules Verne does the legwork to explain the kinds of thrust that would be needed,
28:56to explain the types of materials that would be needed to make this actually happen.
28:59His calculations were so exact that for the first time, the idea of being able to send a person into space appeared plausible.
29:19But while the theory seems sound, any artillery expert will tell you that the reality isn't so straightforward.
29:29My name is Sergeant First Class Gary White. I'm a 13 Bravo Field Artillery Cannon crew member.
29:37The artillery piece that I'm standing in front of is the M1A1 Pac-75 howitzer.
29:42The ranges of these howitzers in particular are 5.5 miles, 8.8 kilometers.
29:48Fire!
29:50Achieving longer ranges for howitzers is generally accomplished through a longer barrel,
29:54which allows the projectile to attain a greater speed and hence greater range.
29:59To make Verne's moonshot a reality, the barrel would need to be over 15 times longer than the canon in the novel.
30:08I think that theoretically it is possible. The practicability of it is relatively nil.
30:15And as it turns out, there was one other thing Jules Verne hadn't accounted for.
30:23The G-forces experienced by a projectile when it's initially fired out of the barrel is extreme to say the least.
30:31If a person were subjected to the same stress as an artillery round were when fired, it would not end well for them.
30:40The person that would wind up with broken bones, absolutely dead.
30:50Verne's dream of putting people on the moon would remain lodged firmly in the realm of science fiction.
30:56At least for now.
30:57But the floodgates of popular imagination had been opened.
31:03Now, a whole host of writers and thinkers were dreaming of what, or even who, we might find out in space.
31:15In 1877, the planet Mars passed unusually close to the Earth.
31:30And in Milan, an Italian astronomer named Giovanni Schiaparelli took the opportunity to study the red planet in unprecedented detail.
31:43Schiaparelli filled his notebooks with hand-drawn pictures of Mars, describing all the features he saw through his telescope.
31:51He drew meticulous maps of a Martian landscape filled with what he named continents and seas.
32:01One of the things that he noticed is that on the surface of Mars, there seemed to be these kind of like criss-crossing networks of lines and describe them as canali.
32:14So in Italian, this means channels.
32:16But when his works were picked up around the world, the word canali came to be mistranslated as canals.
32:26It was an error that would have far-reaching consequences.
32:30When you think about canals, they are artificially created, and if someone is creating them, someone has to be building them, right?
32:38They have to be constructed by someone.
32:41Which creates this wave of speculation that lasts until the present day, right?
32:46Thinking about Martians, right?
32:48What are the Martians doing?
32:51So began a new wave of science fiction writing that speculated what life might exist out in space.
32:58In a sense, it's a lovely thought that there could be other people out there with whom we could make friends.
33:06Of course, the other side of it is there might be aliens out there who might actually come and devour us.
33:13The idea of an alien threat inspired one of the greatest works of science fiction of all time.
33:22H.G. Wells' book, The War of the Worlds.
33:27A tale in which a hostile civilization of aliens from Mars invades the Earth.
33:38Like the gods and monsters of the ancient world, once again, we were populating the universe with stories of fantastical creatures.
33:57By the start of the 20th century, we knew that our Milky Way galaxy consisted of billions of stars just like our own sun.
34:10But we still knew relatively little of its size and shape.
34:16In the 1920s, we didn't even know that our universe extended beyond our own galaxy.
34:22The general consensus is that the universe consists of the Milky Way galaxy. The end.
34:31Even Albert Einstein believed that the universe was finite and everything in it had always been in the same place.
34:40When Einstein solved his own equations and gave us what he thought the universe would look like, it was static.
34:48It had always been solved.
34:49But the theory of the greatest scientific mind of all time was about to be blown apart by a man of the cloth.
34:58In the town of Charleroi in Belgium was a Catholic priest.
35:09Georges Lemaitre had been ordained in 1923, seven years after Einstein published his theory of general relativity.
35:16But Lemaitre wasn't just a man of religion. He was also a man of science.
35:26Georges Lemaitre was a theoretician. So he worked with pen and paper.
35:30He was at pains to say that the Bible was not an astronomical text.
35:33Lemaitre was a brilliant mathematician and when he took Einstein's equations and recalculated them himself, he came to a very different conclusion.
35:47What Lemaitre actually gave us was a solution to Einstein's equations from the general theory of relativity that showed that the universe would be expanding.
35:59This was an idea that went against centuries of astronomy.
36:04Even Einstein couldn't bring himself to believe it could be true.
36:07What was needed was proof.
36:17Edwin Hubble was born in Missouri in 1889.
36:23He's the all-American boy.
36:26He plays basketball for Chicago.
36:30He captains the team.
36:32He speaks Spanish.
36:33He studies law.
36:35And at some point decides he wants to become an astronomer.
36:39He worked in Chicago at Yerkes Observatory, which was the biggest refractor of the time.
36:46So he got great observations there.
36:48And then moved to California, where he used the 100-inch telescope to do the rest of his work.
36:55The 100-inch telescope at the Hooker Observatory in California was the most powerful in the world at that time.
37:10Hubble used it to study nebulae.
37:14Distant fuzzy clouds of light that had puzzled astronomers for centuries.
37:18One of these nebulae in particular caught Hubble's imagination.
37:25For the first time, with this great resolution, was he able to take images of the Andromeda Nebulae.
37:34Hubble could see that the Andromeda Nebula wasn't a cloud of gas, as people had long believed.
37:40It was actually a vast collection of individual stars.
37:47And he was about to solve the age-old conundrum of what Andromeda really was.
37:54At this time, most people believed that our Milky Way was the only galaxy in the universe.
38:00And that Andromeda was located inside it.
38:06There was hot debate over whether it was stars in our own galaxy or something outside of our own galaxy.
38:12But Hubble had other ideas.
38:15He wanted to calculate Andromeda's distance from Earth.
38:19And to do this, he used a technique very similar to the way that we can estimate how far away lights are at night.
38:30By observing their intensity.
38:33By measuring the brightness of Andromeda's stars, Hubble was able to work out how distant it is.
38:41We found that these stars were at least ten times further away than any of the stars that we knew were in our galaxy.
38:49This was an incredible breakthrough for astronomy.
38:53Hubble realized that if star systems existed outside the Milky Way, then the universe was bigger than just our galaxy.
39:04This is the revolution that the galaxies, the nebulae that people were seeing were galaxies, island universes they were called.
39:15He'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.
39:26For the first time, we had proof that ours was not the only galaxy in the universe.
39:37In fact, it was just one among many.
39:45But Hubble wasn't done yet.
39:46Edwin Hubble makes a career measuring the universe with the very best telescopes.
39:56As Hubble studied galaxies far beyond our own, he could see that the light coming from them appeared red.
40:03He knew that this indicated they were moving away from the Earth.
40:10It's a concept that can be understood most clearly not with light.
40:15But with sound.
40:22At school, you will have had this example given to you with a siren of an ambulance or a train.
40:33And you hear the pitch changing depending on whether something is moving away or towards you.
40:38Sound travels in waves.
40:50As an ambulance travels towards you, the wavelength of the siren is compressed.
40:55But as it passes you, the wavelength gets stretched out and the pitch of the siren drops as it travels into the distance.
41:08Light works in exactly the same way.
41:12We can think of light as a wave with a succession of peaks and valleys.
41:17And the distance between any two peaks is what we call the wavelength.
41:20The wavelength of light dictates its color.
41:26A short wavelength appears blue and a longer one red.
41:31Just like Sam, the wavelength of light changes depending on whether it's moving towards you or away from you.
41:41If you took a street lamp and if you were to run very fast towards one of these lamps,
41:47the light that your eyes would see would be blue.
41:51And if you were to run very fast away from it, backwards, because you'd have to be looking at it,
41:57you would actually see redder light.
42:00And when you look at the universe, it's a very similar thing.
42:04If the galaxies were moving towards you, then they would appear blue.
42:09If the galaxy is moving away from you, it would appear to you red.
42:13This was a groundbreaking moment for astronomy.
42:17The galaxies are getting further apart.
42:20That means that our universe is expanding.
42:23An expanding universe was a game changer.
42:27For the very first time, we knew that it wasn't static.
42:31It was dynamic.
42:32We were now closer than ever before to understanding how the universe began.
42:44Back in Belgium, Georges Lemaitre was beginning work on his next big idea.
42:59The fact that the universe was expanding was proof that his mathematical calculations had been right,
43:06and Einstein had been wrong.
43:08The Metro was a man of bold ideas, and having shown that the universe was expanding,
43:18he believed he also had a theory for how it began.
43:23If you take a universe that is expanding, it is a natural question to ask,
43:28what happens if I run the clock backwards?
43:30So if it's getting bigger now, it was smaller in the past.
43:35Le Metro went back to his calculations,
43:39and thought about what would happen if you kept winding the clock further and further back.
43:46Keep on winding the clock backwards, and you realize that things become denser and denser and denser.
43:52Le Metro worked out that at a certain point, the density of the material, if you wound everything back,
44:01would be like an atom.
44:04And this was his starting point.
44:09At the time, it was believed that the atom was the smallest particle in the universe.
44:13And Le Metro used this as the singular point from which all creation sprang forth.
44:24He called it the primeval atom.
44:35This was a truly radical idea.
44:38Einstein's theory of general relativity predicted that the universe had always been there.
44:46It couldn't have a beginning.
44:51But Le Metro was proposing the opposite of this,
44:54that the universe was born from a single point.
44:58At some point, this expands, explodes, blows up,
45:03it becomes the universe that we see now.
45:08Le Metro had laid the foundation for the theory of the Big Bang.
45:13Now, for the first time, we had a creation story given to us,
45:27not by mythology or religion, but by science.
45:30It has been a century since Hubble and Le Metro suggested that our universe had an origin.
45:51In that time, we have launched satellites and telescopes into space to help us see further than ever before.
46:02And to continue the work they started.
46:07Perhaps the most famous space telescope of them all even bears Hubble's name.
46:18And in 2012, it gave us one of the most iconic pictures in modern astronomy.
46:25The Hubble Extreme Deep Field image.
46:29It revealed, for the first time, the true extent of our universe.
46:38Almost everything in that picture is a galaxy.
46:42Billions of stars in each one of those structures that you see behind.
46:46From this image, we knew that there are tens of billions of galaxies in our universe.
46:52We currently estimate that there are at least 100 billion galaxies in our universe.
46:59Some believe there could even be double that number.
47:02It's possibly the deepest image of the sky ever taken.
47:07So it looks furthest into the history of our universe.
47:13And the further out we look in search of more and more galaxies,
47:18the further we are also looking back in time to the very limit of the visible universe.
47:26So we can observe the very first light that the universe emitted.
47:29We call this the cosmic microwave background.
47:32And it's basically the leftover energy from what we think was the start of the universe.
47:40This cosmic microwave background has helped us to calculate how old the universe might be.
47:48Current estimates by astronomers put the age of the universe at about 13.8 billion years.
47:54This means that in our deepest images of the universe, we're looking at the universe as it appeared 13.8 billion years ago.
48:05New technology continues to improve our observation and understanding of the universe.
48:10In 2019, we finally produced an image of something first predicted by Albert Einstein.
48:21A black hole.
48:22A black hole.
48:25But our thirst for knowledge remains unquenched.
48:34At the headquarters of the European Southern Observatory in Munich, Germany.
48:38Dr. Jason Spiromilio is overseeing the construction of parts for the largest optical telescope in the world.
48:51It's called the ELT.
48:54The ELT is the extremely large telescope.
49:00We're not very original with the names, but it's actually apt.
49:05It is an extremely large telescope.
49:15The ELT is being built on the top of a mountain in the Atacama Desert in Chile.
49:19It is due to be completed in 2025.
49:24The diameter is 39 meters.
49:29By comparison, the biggest telescopes that we're running today have diameters of 8 to 10 meters.
49:36So this is an enormous leap forward.
49:39Once built, it will collect 13 times more light than the most powerful telescopes around today.
49:44And 100 million times more light than the human eye.
49:49Dr. Spiromilio is looking forward to that extra power being put to good use.
49:54One of the most exciting things is going to be to detect planets around other stars.
50:01The other thing the ELT will do is be able to see stars in fairly distant galaxies.
50:08You can work out how old they are, you can work out how many metals they have, you can work out where they've been.
50:16You're suddenly measuring really what is happening inside the galaxies.
50:23This is an incredibly powerful machine that allows us to further tie down our understanding of why the universe is the way it is.
50:33This is super exciting.
50:34It may be hard to believe that we once thought the Earth was flat.
50:45That we were the center of everything.
50:49And that the universe began and ended with our own galaxy.
50:54For millennia, we explained the heavens through stories of gods and monsters.
51:10But with the invention of the telescope, we began to reveal a rational universe.
51:21Thanks to the science of astronomy, we have discovered new perspectives on the cosmos.
51:29But there is still so much yet to be revealed.
51:33Our understanding of the universe is still very incomplete.
51:40Everything that we know of from planets and the stars and gases, these only account for 5% of the observable universe.
51:50The other 95% is largely still a mystery.
51:53And until we finally have the scientific solutions to the greatest questions.
52:04There will always be space for us to fill with our imagination.
52:09And this is our mission of recognition.
52:11The second generation of stars and the stars.
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