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00:00Why are we here? Where do we come from? These are the most enduring of questions, and it's
00:20part of human nature to want to find the answers. We can trace our ancestry back hundreds of
00:30thousands of years to the dawn of humankind, but our story extends far further back in
00:38time. Our story starts with the beginning of the universe.
00:4313.7 billion years old, filled with countless stars and galaxies. It's a universe of unimaginable
01:01wonders. Yet each is connected to us. Ultimately, we are part of the universe.
01:13So its story is our story. It's one that we wouldn't be able to tell were
01:22it not for the one thing that connects us so vividly to our vast cosmos. Light. Light reveals
01:33the wonders of our universe in all their glory. Stars being born in distant realms. And galaxies
01:41frozen in time. But light is also a messenger from a long forgotten era, and contained in
01:49the light from the most distant stars in the cosmos, is the story of our universe's origin.
02:00Through light, we can stare back across the entire history of the universe. And ultimately, see
02:09how light breathed life into us.
02:12This is Karnak, one of the largest religious temples ever.
02:13This is Karnak, one of the largest religious temples ever.
02:17This is Karnak, one of the largest religious temples ever built.
02:24Stood here in Luxor, Egypt, for three and a half thousand years.
02:25This is Karnak, one of the largest religious temples ever built.
02:47Stood here in Luxor, Egypt, for three and a half thousand years.
02:54It is a magnificent and beautiful sight.
03:00But in order to see the temple in its full splendor, you must look at it during one spectacular
03:05event that takes place at sunrise on the winter solstice.
03:10The shortest day of the year.
03:19Every stone that makes up these monumental walls was laid to celebrate this moment that
03:25honours the sun god, Amun-Ra.
03:30It's so brief, it lasts for little more than a minute.
03:39The light from Amun-Ra cascades down the avenue of the temple, perfectly aligning with the
04:05pillars and flooding it with light.
04:10This ancient civilisation worshipped the sun as a god, but not without good reason.
04:16The sun was central in their lives.
04:21Today we no longer build temples to the sun, but our fascination with our star has never been stronger.
04:28Shining brighter than 95% of all other stars in our galaxy, this is our sun.
04:46It's in the prime of its life, and rightfully it dominates our world, sitting at the heart of our solar system.
05:01The light the sun generates pours out from the photosphere, its visible surface.
05:14It radiates across space and bathes our planet in its light and warmth.
05:20But every day this most special of stars disappears as it sets across our planet.
05:29Each time a beautiful reminder of one of the most fundamental elements of the universe.
05:35Light.
05:37Light.
05:38Light.
05:39Light.
05:40Light.
05:41Light.
05:42Light.
05:43Light.
05:44Light.
05:45Light.
05:46Light.
05:47Light.
05:48Light.
05:49Light.
05:50Light.
05:51Light.
05:52Light.
05:53Light.
05:54Light.
05:55Light.
05:56Light.
05:57Light.
05:58Light.
05:59Light.
06:00Light.
06:01Light.
06:02Light.
06:03But look carefully and you can see a band of hundreds of billions of stars as you look through our Milky Way galaxy.
06:22From our planet we have a perfect ringside view of the galaxy's wonders.
06:26As we move from the Earth to the edge of the Milky Way,
06:38our Sun becomes just one more point of light in a sea of light.
06:50Pull out even further and we see the whole of our galaxy laid out before us.
06:57Spiralling out from a dense, light-filled core.
07:11But stars like our Sun aren't the only sources of light inside this beautiful spinning disc.
07:18There are other spectacular worlds throughout our galaxy,
07:24which we know intimately because of the light that they emit.
07:27This is the Lagoon Nebula.
07:37Visible on a dark night from Earth, in the star cloud of Sagittarius,
07:41this cloud of dust and gas may appear beautiful and serene.
07:47But this is a furnace where new stars are forged.
07:50This is a furnace where new stars are forged.
07:51This is a furnace where new stars are forged.
07:57The Lagoon Nebula is one of the brightest nebulae in the Milky Way,
08:02all because of a hot, young, new star that sits at its heart.
08:03The Lagoon Nebula is one of the brightest nebulae in the Milky Way,
08:08all because of a hot, young, new star that sits at its heart.
08:18A giant called Herschel 36.
08:21This star is 20 times more massive than our Sun,
08:23and shines around five times hotter,
08:24and shines around five times hotter,
08:25with the light of the sky.
08:26The Lagoon Nebula is one of the brightest nebulae in the Milky Way,
08:27all because of a hot, young, new star that sits at its heart.
08:33A giant called Herschel 36.
08:44This star is 20 times more massive than our Sun,
08:48and shines around five times hotter,
08:51which makes the light that pours from its surface blue.
09:06But this is not the biggest star out there.
09:12By analysing the light from countless Suns,
09:15we have revealed a star that would dwarf even Herschel 36.
09:2975,000 million million kilometres away.
09:34This is Eta Karaini.
09:36This monster star is over 100 times more massive than our Sun.
09:48And burns about four million times brighter,
09:51making it one of the most luminous stars in the Milky Way.
09:55The light from these worlds intimately connects us to the wider universe.
10:14But light can reveal so much more.
10:18Because ultimately, through light, we can read the story of the universe.
10:25I think everybody takes light for granted.
10:35We're so used to it that it just becomes a background part of our lives.
10:39We need it for everything we are and for our very being, for our life.
10:48Light is the thing that has allowed us to understand the universe.
10:59We take light for granted.
11:00But it has a remarkable property which allows it to reveal so much.
11:09A property shared by the energy in the oceans of the world.
11:14Waves.
11:15Astrophysicist Dr. Sasha Shedoui is in Jefferies Bay in South Africa.
11:31So a wave is basically just a transfer of energy.
11:34It's just a collection of peaks and troughs that move from out,
11:38further out to sea, out onto the shore.
11:41As the local surfers wait in the line-up and calm before the breaking surf,
11:46they tell us something about the nature of waves.
11:51They perfectly illustrate the movement of energy through the sea.
11:55As they remain in the same place,
11:58they show that it's not the water which moves towards shore,
12:02just the energy within it.
12:06You can see the surfers out beyond the breakers,
12:09and they just move up and down as the waves pass underneath them.
12:17Just as these waves crash on the shore, releasing their energy onto the beach,
12:22waves of light from space deliver energy to the surface of our planet.
12:27When you're looking out into the night sky and you're seeing all these stars and the constellations and the galaxies,
12:37it's the waves of light that you're really detecting with your eye.
12:41So we're really in some way connected to the rest of the universe.
12:49Our other senses, sound, touch, taste and smell, are all limited by distance.
12:56But light makes vision quite exceptional.
12:58Light waves are special.
13:04They have the ability to transcend all distances.
13:08They journey uninterrupted across the vacuum of space,
13:13from billions and billions of kilometres away,
13:16extending this sense to the furthest reaches of the universe.
13:19But light waves not only let us see out into space, they can also take us on a journey through time.
13:35To understand how light lets us look through time, you must look at a property of all waves, their speed.
13:47Their speed.
14:04Like light, sound also travels as a wave.
14:12By exploring the speed that sound waves travel,
14:14it's possible to show something that all waves have in common, including light.
14:20They all have a speed limit.
14:25Few people come up against the speed limits of waves.
14:29But Dave Southwood is one of them,
14:32having flown military jets for the RAF for 30 years.
14:37This is the Hawker Hunter.
14:39In 1953, it had attained the world's absolute speed record.
14:42So this type of aeroplane was the fastest thing on the planet at the time.
14:48What makes this jet special is it can break the sound barrier at a push.
14:55For Dave to conquer the speed of sound, he has to make the Hunter fall out of the sky.
15:00To take something like the Hunter supersonic, it's basically an understanding of the physics and the aerodynamics of what's required.
15:11And you have to go to high altitude and put the aeroplane into a dive.
15:15Dave needs to climb to 42,000 feet to gain enough altitude before attempting his supersonic dive.
15:28The maximum speed of sound waves, depending on altitude, is around 1,200 kilometres per hour.
15:47Or Mach 1.
15:50Dave keeps gaining altitude.
16:01Dave keeps gaining altitude.
16:02We'll continue to climb on this heading to all the time again at 42,000 feet.
16:06We should be over the water.
16:08And then we should be good to go.
16:13Speed builds and the Mach meter creeps up and up.
16:16Dave needs to work hard to get the aircraft to go faster than its own sound waves.
16:21It is a real balance of the physics to push yourself through the sound barrier.
16:26So you've got to use gravity in the dive to accelerators to get there.
16:33Progress dive down to the supersonic.
16:36Roger, standby.
16:38Roger, clear descend of the supersonic run.
16:41Rolling in.
16:46As Dave enters the dive, he approaches Mach 1.
16:49The jet begins to catch up with its own sound waves, which can't travel any faster.
16:56Within seconds, as Dave plummets towards the ground,
17:00he smashes through the wall of sound waves.
17:03This is heard on the ground as a sonic beam.
17:09There's a Mach number, 1.03.
17:12Wow. Easy.
17:14Easy.
17:17Sound waves have a maximum speed limit, which you can exceed if you have the right piece of engineering.
17:28But the speed of light is another thing entirely.
17:31It was always thought that light waves were different, that they travelled infinitely fast,
17:41because light seemed to switch from an object to our eye instantly.
17:45But the truth was stumbled upon by accident a few hundred years ago.
17:54As scientists watched the precise clockwork motions of the planets and their moons.
17:59Jupiter, the fifth planet from the sun and the largest in the solar system, was the focus of attention at the time.
18:12It was suggested Jupiter's closest moon, Io, could act as a clock in the sky.
18:19Every time the moon emerged from behind the planet's shadow, would mark a unit of time, like the hand on a clock.
18:31So from the Paris observatory, a young Danish astronomer called Ole Christian Romer observed Jupiter.
18:52He followed Io's orbit and measured it each time it came back into view from behind Jupiter's shadow.
18:59But his clocks seemed to shift time.
19:04Astronomer Dr Francisco Diego recounts the leap of genius Romer took to understand this mystery.
19:12So here is Romer with his big telescope at the observatory of Paris,
19:17looking at the movements of Io going around Jupiter and timing it very carefully.
19:22And then something very strange happened.
19:24He realised that that movement was not constant.
19:30It seemed to get slower and then faster and then slower and then faster.
19:36This happened every year.
19:38And he was observing this for ten years.
19:40And he said, well, in no way Io is going to be a different speed around Jupiter.
19:47It cannot change speed. What's going on?
19:49Roma knew that the orbits of the planets and the moons were constant.
19:56Io wasn't changing speed.
19:58It was the position of the planets and moons relative to each other, which changed through the year as they orbited the sun.
20:05He had this amazing intuition because when I am here, closer to Jupiter, I can see Io emerging from the shadow of Jupiter, from this position, when the light has travelled this distance.
20:25And a few months later, I will still see Jupiter with the moon going around it, but now I am looking from this position, where the light has to travel a longer distance.
20:38I started thinking and said, it is the speed of light.
20:42Light has speed.
20:44It doesn't travel instantly.
20:46It will take time to go from here to there.
20:48Roma had realised that the extra distance the light had to travel from Io to Earth must be responsible for the delay.
21:06He had definitively proved for the first time that the speed of light is finite.
21:10Every physicist today knows this speed, whichever way they look at it.
21:27It's 300 million metres per second.
21:30The time it takes you to click your fingers, the light would travel about seven times around the world.
21:37The speed of light is three times ten to the eight metres per second.
21:40In old-fashioned units, one foot per thousand millionths of a second.
21:48About that far, every nanosecond.
21:52We are quite slow when you think about it.
22:00In the vacuum of space, light travels at ten trillion kilometres a year.
22:17This gives the distance measurement the light year.
22:19But the light year is also a measure of time.
22:34And it's this connection to time that means that the finite speed of light has profound consequences.
22:40The finite speed of light is significant because it takes time for light to travel from a distant object to our eye.
23:01So the further away that object is, the further back in time we see it.
23:07For astronomer Dr. Petri Vaisanen, the speed at which light travels opens up a window into our universe's past, here in East Africa.
23:33When I look at my hand, which is quite close by, it actually takes some time for the light which hits my hand to come to my eyes.
23:52Very small time, but nevertheless, it does take time.
23:56I can never see anything right at this moment. We are always looking into the past.
24:00On Earth, the distances that light can travel are relatively short, so the time it takes light to travel to our eye is imperceptible.
24:13But look at astronomical scales and the implications are much greater.
24:18The sun is about 150 million kilometers, so we see the sun as it was eight minutes ago in the past, in history.
24:30Step further out into our cosmic backyard, and it's possible to see even deeper back in time.
24:37Saturn is 1.4 billion kilometers from the sun.
24:45We see its glistening rings of ice as they were over an hour ago in the past.
24:50And we can only ever observe Neptune, the outermost planet in the solar system, as it was more than four hours ago.
25:03Look up into the sky on a cloudless night, and you can see the light that has traveled from much further afield.
25:18Amongst the stars of the Milky Way lies a faint smear of light.
25:23This is another galaxy outside of our own, called Andromeda.
25:39This beautiful spiral galaxy lies 25 million million million kilometers from Earth, the furthest object visible with the naked eye.
25:49The light that pours from this swirling mass of stars connects us to a remarkable time in human evolution,
25:59and to our most distant ancestors, lending the African plains added significance.
26:062.5 million years ago, the first humans, Homo habilis, roamed these plains.
26:22And as they did, light rays from Andromeda began their journey across the universe.
26:29Light rays which are only reaching us today.
26:32It's kind of cool to think that the light that we see now from Andromeda, which started 2.5 million years ago,
26:48was about the same time as our ancestors were stepping these very parts where we are now sitting.
26:52Within that 2.5 million years, everything we know in human history has happened here.
27:07It is just amazing that the time scales and the distance scales are so vast.
27:11And our own civilization is, it's just a snap of fingers compared to all that.
27:19Look back to a time beyond our first ancestors by using telescopes,
27:35and we can, in effect, become virtual time travelers.
27:38So this is Centaurus A, only 10 million light years away.
27:51Active galaxies, a huge, massive dust lane in the front,
27:55and star-forming regions you can see on the background over there.
27:58Now we're getting closer to 100 million light years away.
28:14This is NGC 520, two galaxies which are colliding and producing many stars.
28:20When these galaxies dramatically collided, dinosaurs still ruled the Earth.
28:34Here's another beautiful example of a colliding galaxy.
28:38You see two galaxies, basically one this way and the other one that way,
28:42and it looks like a tinker bell or a bird, so we actually called it the bird galaxy.
28:46It's 650 million light years away.
28:52Life was still confined only to the world's oceans when these galaxies smashed into one another.
28:59It's like an archeological day, you're looking back in time.
29:03The further away we see, the further back we go.
29:09But there's a picture that can take us back even further.
29:12The Hubble Ultra Deep Field.
29:17It can take us right to the very edge of our universe.
29:23Taken by the Hubble Space Telescope on orbit around the Earth,
29:29it looked at one piece of sky for almost a million seconds, about 11 days,
29:34and took this incredibly deep image of the universe where you can see very, very, very distant and faint objects.
29:45We can see some stars from our own Milky Way, but for the most part, almost everything else is galaxies incredibly far away.
29:54There are an estimated 10,000 galaxies in this image, and each one contains thousands of millions of stars, each as massive as our sun.
30:09In fact, some of the furthest away galaxies ever seen to date are from this image, and they are 13 billion light years away.
30:25So it's an incredibly, incredibly big universe we're talking about.
30:33It does make you realize how extremely small we are.
30:38We're seeing the most distant galaxies in this image, as they were 13 billion years ago, when the universe was in its infancy.
30:57But not only that, these galaxies also tell us something much deeper.
31:07They reveal a clue about how our whole universe began.
31:18As Hubble gazed across the cosmos, it saw galaxies shine back in all different colors.
31:27But every one of the galaxies at the very edge of the visible universe glowed red.
31:38These are some of the galaxies that Hubble saw.
31:44Their red light tells us about the universe's origins.
31:49To understand why, you must explore a beautiful property of all starlight.
31:54Color.
32:11For centuries, people thought that light just illuminated the world, letting us see but nothing more.
32:25We now know that every beam carries massive amounts of information and detail.
32:33Some of that information is written in its color.
32:45Physicist Professor Brian Cox has come to one of the most spectacular natural wonders on Earth.
32:50Victoria Falls.
32:53The rainbows above the falls are a permanent feature.
32:56They exist because the spray from the waterfalls acts as nature's very own prism.
33:00Showing that white light is far from colorless.
33:01The rainbows above the falls are a permanent feature.
33:03They exist because the spray from the waterfalls acts as nature's very own prism.
33:06Showing that white light is far from colorless.
33:10Well, rainbows are formed because the white light from the sun is split into its component colors by the water droplets in the atmosphere above the falls.
33:24So imagine a beam of white light coming from the sun, going into the front of the raindrop, bouncing off the back, and then coming out into my eye.
33:45Each color bounces back at a slightly different angle, revealing all of the colors of the rainbow in a magnificent arch.
33:59What separates every color is another property of light.
34:05Each light wave can have a different length.
34:08So red light has a relatively long wavelength, and then you go through the yellow and onwards to blue, and blue has a relatively shorter wavelength.
34:24So what we see as color is really just the different wavelengths of light.
34:28These colors not only paint our world, they also explain the origins of our universe.
34:45Because waves of light are not fixed, they can change.
34:49Now when light's emitted, it doesn't have to stay at the same wavelength.
34:57It can be stretched or it can be squashed.
35:00And if you squash the light, so you reduce the wavelength, then everything moves to the blue end of the spectrum.
35:06But if you stretch it and increase the wavelength, then everything moves to the red end of the spectrum, and that's called redshift.
35:12The furthest galaxies at the edge of the universe were full of young, hot, blue stars.
35:23But as the light left those galaxies and journeyed across the expanse of space, the short blue wavelengths were stretched until they became red.
35:33So the interpretation of the fact that all the most distant galaxies appear red is that space has stretched and stretched and stretched, the light has stretched, and the whole spectrum of the galaxy has moved to the red end of the spectrum.
35:52As space stretches, the galaxies are moving further and further apart from one another.
35:58This can mean only one thing. The universe must be expanding.
36:08If you were to turn back time, then in the past, all of the galaxies must have been closer together.
36:14And if you carry on to rewind backwards and backwards, further and further back into the past, then it looks like at some point, very distant past, all the galaxies were on top of each other.
36:31So that means that the universe used to be very, very much smaller than it is now.
36:36Then it could have had a beginning. And that is the Big Bang Theory.
36:42The Big Bang Theory.
37:00In one violent moment, over 13 billion years ago, our universe was born.
37:12The Big Bang Theory.
37:25The Big Bang is often thought of as a single explosion which expanded into space.
37:30It's hard to imagine that the Big Bang didn't explode into space. It created space.
37:51And that space has been relentlessly expanding in every direction since.
37:55To this day, the galaxies are still flying apart.
38:02This continuing expansion means our universe today is 93 billion light years across.
38:28But remarkably, we can understand how it evolved from a tiny point into this vast cosmos.
38:42That's because a blueprint for our entire universe was written in the light released at the Big Bang.
38:51That light is still there. You just need to know how to look for it.
38:55Visible light is just a tiny fraction of all the light in the universe.
39:13At either end of the visible spectrum, there is something very mysterious.
39:18Invisible light.
39:19Cosmologist Professor Justin Jonas has come to the spectacular Namib Desert.
39:30Not to see, but to feel this light.
39:33This sand here has gotten very hot during the day.
39:44You can put your hand over the sand and you feel the rays of the heat that are coming off.
39:47That heat is actually light.
39:49It's light at longer wavelengths than the light that our eyes are used to seeing.
39:53And it's called infrared.
39:54So it's light, but it's light we can't see, but it's light that we can feel.
40:05This infrared light is released by almost everything in the universe.
40:10Even humans emit it.
40:11But infrared isn't the end of the story.
40:17There are even longer wavelengths of invisible light.
40:22And all we need to detect them is a simple radio.
40:27The very longest waves that we have in the universe are in fact radio waves.
40:32If I detune the radio, you don't hear the station anymore.
40:48You hear a hiss.
40:50But that hiss is radio waves.
40:53And that is being transmitted by all sorts of objects, including the sand.
40:57This sand is giving off radio waves and this radio can pick those up.
41:02And even more intriguingly, a very small fraction of the radio waves that this radio is picking up
41:08is the light that's coming from the Big Bang.
41:14This light produced in the very first moments would give us the blueprint of the entire universe.
41:23And that light has very short wavelengths.
41:25So if I can represent that in the sand here as a wave like that.
41:30But these waves have travelled through space now since the beginning of the universe.
41:36More than 13 billion years.
41:38And in that time, the universe has expanded.
41:42What it's done is effectively stretched out these waves.
41:45And these waves are very much longer now.
41:47And these longer waves are in fact now radio waves.
41:49These stretched out waves have been given a name.
41:59The Cosmic Microwave Background, or CMB.
42:03And it fills every part of our universe.
42:05This light pours across the Earth.
42:10If we could see it, there would be no night.
42:16It would illuminate everything.
42:19In 2001, NASA satellite WMAP took an entire sky photograph of the CMB.
42:32That picture revolutionised our understanding of the origins of the universe.
42:38This here is an image of the Cosmic Microwave Background made by the WMAP satellite over a number of years.
42:44It may not look like much to the untrained eye, but it is in fact one of the most incredible images that humans have ever made.
42:51It is the earliest picture that we will ever have of the universe.
42:56The WMAP satellite showed that the CMB contained tiny differences in temperature, which correlated with differences in density of the early universe.
43:10As time passed, gravity began to work on the denser areas, and they grew denser and denser.
43:26Atoms formed, and began to clump together to create the very first structures.
43:48Over time, these structures grew so massive that they collapsed and heated to more than 10 million degrees.
43:56Hydrogen fused together, releasing enormous amounts of energy.
44:06200 million years after the Big Bang, the first stars in the cosmos were born.
44:15Across the universe, countless suns burst into life, and space began to fill with light.
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44:52Eventually, these stars group together to form vast galaxies.
45:07It's only because of those tiny differences in density in the early universe
45:11that we have the rich and varied cosmos that we recognize today.
45:16Without them, there would be no planets or stars, and no galaxies.
45:26Our universe would not exist, and space would look the same in every direction.
45:319 billion years after the Big Bang,
45:47those tiny differences in density led to a star forming
45:52in a dark and unremarkable patch of space
45:55known as the Orion Spur of the Perseus Arm in the Milky Way galaxy.
46:08We call that star the Sun,
46:10and its light illuminated our embryonic solar system.
46:14By capturing light from the skies,
46:28we've been able to understand our universe's origins and evolution.
46:36And light is also key in one final twist of the story of our universe.
46:41The evolution of complex life, including us.
46:54This is the Rocky Mountains in British Columbia, Canada.
47:01Amongst these peaks is a snapshot of a remarkable time on Earth.
47:05It's what's drawn paleontologists like Dr. Paul McNeil repeatedly to this place.
47:16Because here lies one of the richest fossil beds ever discovered,
47:21the Burgess Shale.
47:25It may only look like a broken rock face,
47:28but the creatures fossilized within it tell a fascinating story.
47:31505 million years ago, this entire area was actually covered by water.
47:38Something that we might see like off the coast of Florida today.
47:41We had communities of animals which lived up in the reef at that time.
47:46And periodically, large mudslides would actually bury the animals and help preserve them.
47:52And this is quite simply one of the most important fossil sites in the entire world.
47:56The reason for that is when we're looking at the animals here,
48:01this is when animal life first got large.
48:07Up until this point in time, life on Earth hadn't progressed beyond very simple, soft-bodied organisms.
48:14Then suddenly, the diversity of complex life erupted in what we call the Cambrian Explosion.
48:29One of the most interesting animals that we find up here at the Burgess Shale is the trilobites.
48:34These are kind of the classic fossils.
48:35We can see that they have a tail, a number of segments which make up the middle of the body,
48:40and we have the large crescent-shaped eyes.
48:44And trilobites are actually one of the first animals that we find in the fossil record.
48:48It has well-developed eyes.
48:50This ability to see made trilobites an incredibly successful species.
48:56But they were not the only animals to harness the power of light.
48:59Another one of the amazing animals that we find here is this little animal called Pukai.
49:05You know, a lot of people say it looks like kind of a small slug-like creature.
49:10This animal may have had the ability to tell light from darkness.
49:18Though it didn't have well-developed eyes,
49:19some scientists believe that this could have been one of the earliest creatures to detect the light
49:25that has flooded our universe for billions of years.
49:31And this matters because we may well be related to this little worm-like creature.
49:37If you look very closely at it, you see it actually has a cord.
49:41This indicates that this little animal actually belongs to the group called the Chordate.
49:44Scientists are currently re-examining Pukai.
49:50If it is indeed one of the earliest Chordates,
49:54the group of animals from which humans arose,
49:57then we may owe the evolution of our own vision to this little creature.
50:02Light is the thing that has actually given us the key
50:06to interpreting not only life on Earth, but our place in the universe.
50:11Light gave rise to us.
50:18But it not only gave us the ability to enjoy the spectacle of our universe.
50:24It allowed us to understand it.
50:32Through light, we've witnessed stars being born in distant realms.
50:38Galaxies lost in time at the very edge of the visible universe.
50:55And our cosmos just moments after it all began.
51:01Light has allowed us to tell the story of the universe.
51:05Light has allowed us to tell the story of the universe.
51:09of us.