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Documentary, Hidden Universe - Dark Matter
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00:00Today, we are unlocking the secrets of the cosmos.
00:10Exploding stars, supermassive black holes, and screaming jets and gas.
00:19Across the world and in space, high-tech telescopes are picking up the signals that reveal a hidden universe.
00:27A cosmos almost incomprehensible in its size, age, and violence.
00:34Telescopes have continued to open up vaster and vaster windows on the universe.
00:41Scientists are now racing to uncover new secrets.
00:45This is a good-looking area.
00:47With telescopes that are bigger, higher, and more advanced than ever before.
00:54Every time you try and explore a new part of the universe, we have these great discoveries, these great surprises.
01:01Since the start of the 20th century, telescopes have taken us beyond our planets and beyond our galaxy.
01:10To see things we never dreamed of.
01:13They've shown us the very birth of our universe.
01:17Invisible matter.
01:19And the mystery of dark energy.
01:22Will the next generation solve the biggest question of all?
01:26Our ultimate destiny.
01:28Dark energy is one of the keys to understanding the fate, the ultimate fate of the universe.
01:34Hunting the edge of space.
01:38Up now.
01:39On NOVA.
01:40Major funding for NOVA is provided by the following.
01:59David H. Koch.
02:04And...
02:06HHMI.
02:09Howard Hughes Medical Institute.
02:12And the Corporation for Public Broadcasting and viewers like you.
02:16Additional funding for Hunting the Edge of Space is provided by the Alfred P. Sloan Foundation
02:21to enhance public understanding of science and technology in the modern world.
02:24And by Mount Cuba Astronomical Foundation.
02:27And...
02:32At the dawn of the 20th century, our galaxy, the Milky Way, was the entire known universe.
02:46But now we live in the golden age of cosmic discovery.
02:50Telescopes are exploding our understanding of the cosmos.
02:57Bigger than ever, and working in giant networks across the globe and in space,
03:04they are unlocking secrets that astonish and amaze us.
03:09The planets of our solar system in breathtaking detail.
03:21The majestic rings of Saturn.
03:24And rolling storm clouds on the surface of Jupiter.
03:28But far beyond our solar system, we are now discovering exoplanets.
03:35Orbiting other suns.
03:37And beyond our galaxy, another hundred billion galaxies.
03:45Like Andromeda.
03:46And whirlpool.
03:47And whirlpool.
03:48Each harboring hundreds of billions of stars.
03:52We've detected supermassive black holes spinning violently at the very centers of galaxies, including our own.
04:06We've witnessed supernovas exploding stars millions of light years away, spewing out superheated gas at 600,000 miles per hour.
04:23And deep inside clouds of gas and dust, billowing trillions of miles high, we can glimpse new stars being born.
04:36Telescopes have continued to open up vaster and vaster windows on the universe.
04:42Now, the latest telescopes are revealing the invisible mysteries of space that we are only just beginning to understand.
04:55Dark matter, the hidden scaffolding our entire cosmos is built on.
05:02And dark energy, a powerful and invisible force that is pushing our universe apart.
05:11Every time you try and explore a new part of the universe, we have these great discoveries, these great surprises.
05:30Back at the start of the 20th century, the universe seems to be a much smaller place.
05:36The sun, earth and planets make up our solar system.
05:43And beyond them are the millions of stars that make up the rest of our galaxy.
05:48The Milky Way.
05:50But that's it.
05:52That is our universe.
05:55And for astronomers, a major question remains.
05:59A key question at the beginning of the 20th century was whether or not our Milky Way was all there was.
06:06Was that the whole universe?
06:07Or were there other galaxies?
06:09So what happened?
06:11How did telescopes come to reveal so much of our cosmos and reach to its very edges?
06:24The revolution starts in the early 1900s.
06:29A brand new telescope is being built.
06:34It will change our perception of the universe forever.
06:39Explode the edges of the cosmos and set us on a voyage of discovery that is still going on today.
06:47That telescope is one of the most important in the history of astronomy.
06:53The first steps in the revolution.
07:03An astronomer is hiking up Mount Wilson, a 5,700 foot peak high above Pasadena, California.
07:12He's rising above the clouds and haze of the lower atmosphere, which distort telescopic images.
07:23He wants to see if it is possible to build an observatory at the very peak of the mountain,
07:29where the air is thin and crystal clear.
07:33It was a growing realization that for really good astronomical seeing, you had to find good sights,
07:42rather than just build a telescope where you happen to have an old observatory.
07:46And people have begun to realize that the mountains in the west of the United States offered real possibilities.
07:53One hundred years ago, the simple idea of putting an observatory on top of a mountain is revolutionary.
08:02And an enormous logistical challenge.
08:07Hundreds of tons of steel and concrete have to be carefully hauled up the narrow mountain roads.
08:14But the clear skies are worth it.
08:17Mount Wilson will become the highest observatory on Earth,
08:21and a blueprint for observatories all over the world.
08:28This observatory is the vision of one man, George Ellery Hale.
08:34His mission, to solve the greatest mysteries in the cosmos.
08:39To find out if there is anything beyond our galaxy.
08:43But for Hale, high altitude is just the first step.
08:52To see deep into the cosmos with stunning clarity,
08:56he needs his new observatory to house the biggest telescope in the world.
09:02Telescopes are like light buckets.
09:06The larger the telescope, the more light it can gather, bringing the faintest stars into focus.
09:14But Hale faces a challenge.
09:17Most telescopes at the time use glass lenses to focus light.
09:22But when glass lenses get really big, they bend under their own weight, causing distortion.
09:29Glass lenses just can't get any bigger.
09:34What Hale needs is a radical new design.
09:38A giant telescope that can collect a lot of light, but which doesn't use lenses.
09:48So Hale turns to a telescope first created by Isaac Newton in 1668.
09:54The reflector.
09:58This kind of telescope uses a curved metal mirror instead of glass lenses.
10:04It focuses light by reflecting it to a point.
10:11Now, Hale is planning to build one on a scale that has never been seen before.
10:17Only revolutionary engineering can support the gigantic instrument he plans.
10:25And the project will take 11 years to complete.
10:31The curved mirror spans 100 inches in diameter and weighs 9,000 pounds.
10:40It sits at the bottom of a 40 foot cast iron cube.
10:43Housed in a 100 foot diameter dome.
10:46Finally, in 1917, the biggest telescope the world has ever seen sparks wonder amongst the public.
11:02The scientific eye of America.
11:04To this mecca of stargazers, a flock of Svelmers from all nations.
11:08In the pantheon of telescopes and astronomy, Mount Wilson, it is no exaggeration to say,
11:17is probably the most important telescope in the history of cosmology.
11:23Discoveries that were made here really put it onto the map.
11:29This great telescope is soon directed towards one of astronomy's most enduring mysteries.
11:41Strange fuzzy clouds of light hanging amongst the stars have puzzled astronomers for years.
11:48They are the nebulae.
11:50Some are egg-shaped swirls.
11:55Others are delicate spirals of stars.
11:59Others have branching tentacles.
12:02Thousands of them are visible through telescopes.
12:06But nobody knows what they are or how far away they are.
12:10Some astronomers believe that certain types of nebulae could lie outside the edges of our Milky Way galaxy.
12:20They wonder if they could be island universes, galaxies like our own.
12:25If so, this would shatter the limits of the universe and our understanding of it.
12:31But they have never had the technology to solve the mystery.
12:38Until now.
12:42Hale invites the world's best astronomers to help crack the mystery once and for all.
12:51Among them is a young man called Edwin Hubble.
12:54Edwin Hubble was one of the greatest observational astronomers ever to have lived.
13:02He made a tremendous number of important discoveries.
13:07Night after night, Hubble examines the nebulae with the 100-inch telescope.
13:14He examines one in particular, the Andromeda Nebula,
13:19which Hubble can now see in unprecedented detail.
13:22It would be this 100-inch telescope that would finally be powerful enough to bring the nebulae within reach
13:31and would start a series of discoveries that just completely changed our understanding of the universe.
13:42Hubble can see stars within the Andromeda Nebula,
13:46but to find out if it really is an island universe outside the Milky Way,
13:50he has to find out how far away it is.
13:54But that is not an easy task.
13:59Establishing distances in the vastness of space is one of astronomers' biggest challenges.
14:06Stars, like car headlights, appear brighter the closer they are.
14:15If you know their true brightness, you can work out their distance.
14:20It's like knowing the wattage of a light bulb.
14:23If you don't know this, you have a problem.
14:26As NASA astrophysicist Kim Weaver explains.
14:32At that distance, the headlight on that car appears to be the same brightness as the headlamp on this bicycle.
14:39But as the headlights get nearer, it becomes obvious that their true brightness is in fact greater than that of the bicycle lamp.
14:46It's the same with stars.
14:49If we know how bright a star is intrinsically, we can work out how far away it is from us.
14:57And that's what we call a standard candle.
15:00Luckily for Hubble, astronomers had recently discovered a special type of star with a true brightness they can calculate.
15:08It is called a Cepheid variable.
15:16And it's recognizable because it pulsates over a period of days.
15:21All Hubble has to do now is find one of these stars in a nebula like Andromeda.
15:28At night, he scans the heavens with a hundred inch mirror.
15:41By day, he analyzes the photographs he has taken, hunting for any stars that have changed brightness.
15:48Then, on October 6th, 1923, after months of work, Hubble strikes gold.
16:00A Cepheid variable on the edge of Andromeda.
16:07I'm looking at the original discovery plate of Edwin Hubble, where he first found a Cepheid in the Andromeda galaxy.
16:14And he actually marks on this plate, between two black lines, where the position of the Cepheid is.
16:22And he writes VAR, exclamation mark, when he realizes it's a Cepheid.
16:28So he's compared two different plates, and he's discovered that this thing is actually changing in its brightness.
16:34Hubble can now make a measurement that will change history.
16:39The distance to one of the nebulae.
16:41He works out that Andromeda is about 800,000 light years away.
16:48That's more than eight times the distance to the furthest known stars in the Milky Way.
16:55This means Andromeda has to be outside the Milky Way.
17:01A whole new galaxy beyond our own.
17:04This is irrefutable evidence. He's very excited. He writes it with an exclamation mark, because he realizes the significance of the discovery.
17:14Hubble's discovery explodes the frontiers of our universe.
17:18Our Milky Way galaxy is no longer all there is in the cosmos.
17:30Hubble goes on to discover that Andromeda is not alone.
17:35He reveals that dozens of nebulae are actually other galaxies.
17:40Edwin Hubble's research with telescopes profoundly changed our view of the universe.
17:47The most powerful telescopes of today are still exploring the wider cosmos that Hubble first discovered.
17:56Looking across billions of light years, they have uncovered 100 billion new galaxies beyond our own.
18:05Each made up of 100 billion stars.
18:10Multiply those together and you have more stars than all the grains of sand on all the beaches and all the deserts on Earth.
18:20Just like that, the universe became 100 billion times larger.
18:29Hubble's discovery that there were other galaxies outside our own blows the universe wide open.
18:37But what he discovers next will be even more extraordinary.
18:44Several years earlier, other astronomers had discovered that many of the nebulae, now identified by Hubble as galaxies, were moving away from us.
19:02Now, Hubble wants to work out why, and he will do it by analyzing light itself.
19:15He uses a method first discovered in the 1800s.
19:21This is a spectroscope made in about 1880.
19:25One of the first generation of instruments used for analyzing the light from the sun.
19:32It's an instrument like this that transformed astronomy, because you can decode the light in a way that you'd never imagined.
19:44The spectroscope splits white light into its rainbow spectrum of colors, and hidden in this spectrum are clues to the behavior of the stars.
19:56Light is made up of waves, and each color has its own wavelength.
20:02Blue light has a short wavelength.
20:05Red light has a longer wavelength.
20:08But when a galaxy is racing through the cosmos, the wavelengths of the light appear to change from our perspective on Earth.
20:15If the galaxy is moving towards us, the wavelengths get squashed and appear more blue.
20:23If the galaxy is moving away from us, the wavelengths get stretched out and appear to become more red.
20:29We call the effect redshift.
20:34It's like a cosmic speedometer.
20:36The faster a galaxy is moving away from us, the more its light waves are stretched towards the red.
20:42Sound works in much the same way, because it too is made up of waves, as astronomer Alex Filippenko explains.
20:55This is going to be great. I'm going to blare on the horn now. Here we go.
21:12The pitch of the sound is constant, even though the car is speeding down the road.
21:20In the driver's seat, Filippenko hears the horn at a constant pitch. It doesn't change.
21:27But now he wants to hear what the horn will sound like if he stands on the roadside, and the car drives past him.
21:46When the car was coming toward me, the waves from the horn were being squished together, so the pitch sounded higher.
21:52And as the car passed me and moved away, the waves were stretched apart, so the pitch sounded lower.
21:59So it sort of went like that.
22:03If that blue car had been going fast enough, the high-frequency blue light would have been stretched apart,
22:11then the blue color would have shifted all the way to red. The car would have looked red to me.
22:17That's known as a redshift.
22:22Back in 1928, Hubble is looking at the redshift of his new galaxies to find out how fast they are moving.
22:32He sets out to chart the speeds of galaxies both near and far.
22:37He wants to see if he can find any correlation between how fast they are moving and how far away they are.
22:45Night after night is spent painstakingly analyzing the light from galaxies.
22:53The final results are staggering.
22:57Hubble discovers that the farther away a galaxy is, the greater its redshift.
23:04So the faster it is moving away.
23:06By 1929, he had established a very interesting relationship between them.
23:17The nebulae that are farther away are moving faster away.
23:21Hubble comes to an astounding conclusion.
23:25The universe is expanding.
23:28The galaxies may look like they are traveling away from us, but in fact, it is space itself that is stretching apart.
23:38Here's a good analogy of how the expanding universe works.
23:46Now this is a hypothetical one-dimensional universe where the ping pong balls are the galaxies and the hose is the space between them.
23:54As the space expands, all of the ping pong balls recede away from one another.
23:59And every bit of space expands.
24:03The more space there is, the faster the distant one looks like it's expanding away from us.
24:11Hubble's discovery is one of the greatest breakthroughs in the history of astronomy.
24:17The universe is not static.
24:20It is growing bigger and bigger.
24:22These galaxies are moving apart from one another because space itself is expanding between the galaxies.
24:32That was a marvelous discovery.
24:35Hubble could never have made his discoveries without the 100-inch telescope on Mount Wilson.
24:40High above the plains of New Mexico, one of the most advanced telescopes of today is taking Hubble's groundbreaking work even further.
24:56The Sloan Digital Sky Survey is analyzing starlight from hundreds of thousands of distant galaxies.
25:04Each aluminum disc is a galaxy map for a small part of the night sky.
25:13So we've got 640 holes on an aluminum plate.
25:17Each hole corresponds to a galaxy many millions of light years away.
25:25Optic fibers link each hole to a high-tech version of the spectroscope used by Edwin Hubble.
25:32It will measure the redshift of the galaxies.
25:38Then technicians insert the map into the base of the telescope
25:42and match it up to the right section of the night sky.
25:47So you can get 640 spectra at once,
25:51which is a great way to get a survey done, much better than once at a time.
25:54This survey has now calculated the speeds of over 930,000 galaxies,
26:04giving us a far more precise image of the universe we live in,
26:09and how fast it is racing apart.
26:12But back in 1929, Hubble's discovery begs a new question.
26:22If the universe is expanding, what is it expanding from?
26:29Hubble saw and realized that things were moving away from each other,
26:32and the natural leap from that is,
26:36well, if things are now moving away,
26:38weren't they all at one time in a central location?
26:43Astronomers put forward a revolutionary theory.
26:47The Big Bang.
26:49A single moment in time when the universe was born.
26:52The idea is so revolutionary, scientists struggle to make sense of it.
27:02We had no way to observe this phenomenon.
27:06It made no sense to people at the time.
27:09Even Einstein didn't believe in this idea.
27:12We didn't have the belief that it might happen,
27:15and we also didn't have the telescopes to observe the effects of the Big Bang.
27:19To find the proof, astronomers will need a completely different type of telescope,
27:27one that can see what our eyes cannot.
27:33Beyond the colors of visible light are the rays of the electromagnetic spectrum
27:39that our eyes cannot detect.
27:41Gamma rays, X-rays, radio waves and microwaves may be invisible,
27:46but they are crucial for astronomers.
27:50They hold the keys to some of the most violent events in the universe.
27:56The human eye is only sensitive to a very small part of the electromagnetic spectrum.
28:03These are all the waves that behave like light.
28:06But we have been able to see in parts of this spectrum
28:09which are not visible to the human eye.
28:211964. Astronomers Arno Penzias and Robert Wilson are working with a new radio telescope.
28:29Its giant antenna enables them to measure microwaves and radio waves in space in the form of heat.
28:38They expect the stars of our Milky Way to emit a faint glow.
28:43But when they point their antenna to empty space, where there should be nothing at all,
28:49they discover something very unusual.
28:52We expected to find the sky away from the Milky Way to be quite cold,
29:02to be very close to absolute zero.
29:05Instead we found, to our very great surprise,
29:09that it was about three degrees hotter than that.
29:12The mysterious signal seems to come from every direction.
29:16We had a noise, a signal if you want to call it that.
29:19Could be radio noise sources or something else.
29:23But I had no idea what it was.
29:25Penzias and Wilson suspect that there is a defect with the equipment which is causing interference.
29:31They try everything.
29:36Even sweeping the pigeon droppings from inside the antenna.
29:40It didn't go away from winter or summer, day to night, seasons.
29:45We've looked at every possible direction.
29:50There was a high altitude nuclear explosion of two summers ago.
29:56So maybe there was something in the atmosphere, charged particles.
29:59I didn't know.
30:03Penzias and Wilson are at a loss.
30:06Until they hear about the work being carried out by a team of scientists just down the road,
30:13at Princeton University.
30:15Robert Dickey and his colleagues have worked out that the afterglow from the Big Bang should still be felt today.
30:21They have even calculated the temperature, three degrees above absolute zero.
30:33So I called up and I told Bob Dickey's office.
30:37And I happened to get him.
30:38And what I learned afterwards was that he put down the phone and he turned to his colleagues.
30:47And he said, boys, we've been scooped.
30:52Penzias and Wilson have unwittingly found the first physical evidence of the Big Bang.
30:57Their radio telescope has picked up the afterglow of the beginning of the universe.
31:07It remains one of the most important discoveries of all time.
31:14I have no idea that we will see the echo of creation.
31:19In 1978, Penzias and Wilson received the Nobel Prize.
31:30To be on Liszt with Albert Einstein, to be on that same role, was almost too much to bear.
31:41I just couldn't think of comparing myself against the people who have won Nobel Prizes.
31:45In 1964, when the background radiation from the Big Bang was discovered,
31:52it was for the first time direct evidence that there was a hot Big Bang, an origin to our universe.
32:02Penzias and Wilson have found direct proof for the Big Bang.
32:07But it will take another 37 years and far more sophisticated microwave technology
32:12before we discover how the Big Bang formed the universe we see today.
32:24Heading to an orbit one million miles from Earth
32:27is the Wilkinson Microwave Anistropy Probe, or WMAP.
32:32A super-advanced version of Penzias and Wilson's giant antenna,
32:38armed with two reflecting telescopes.
32:42WMAP's mission is to examine the afterglow of the Big Bang in extreme detail,
32:50and to try and find out why galaxies formed.
32:53With WMAP, we were trying to look way back to the very, very earliest times in the universe.
33:02After a year of recording, the first results are mapped.
33:08The WMAP observations were incredible.
33:11Instead of a smooth background radiation, you could measure to one thousandth of one percent
33:20changes in temperature across the sky.
33:24WMAP shows that actually there are tiny fluctuations in temperature.
33:29The dramatic-looking temperature changes here are actually tiny.
33:34Going from a redder hot spot here to a bluer cold spot
33:38is only a change of a couple hundred millionths of a degree.
33:42So it's really tiny temperature changes, but a very dramatic pattern over the sky
33:47which has revealed tremendous information to us.
33:52The tiny red spots are where matter is beginning to come together,
33:57and where clusters of galaxies will eventually form.
34:03This is vital evidence.
34:05Clues to how stars and galaxies first came into being.
34:10The WMAP data helps astronomers work out what happened at the very beginning of the universe,
34:18right after the Big Bang.
34:20We can actually deduce from that things that happened in the first trillionth of a trillionth of a second of the universe,
34:27and I think that's just extraordinary to be able to probe that early in the history of the universe.
34:33And WMAP's accuracy allows astronomers to solve another great cosmic mystery,
34:42the exact age of the universe.
34:46For the first time, astronomers have an accurate figure.
34:50We now know that the universe is about 13.7 billion years old.
34:57That's very old, but it's not infinite.
35:00It could have been infinite, but it's not.
35:02One of the great discoveries of 20th century science.
35:06WMAP has taken us further from the Earth and closer to the very birth of the cosmos than any other telescope in history.
35:15It is revealing the edges of the universe in unprecedented detail.
35:22But the microwave data it records is invisible to the human eye.
35:28Would it ever be possible to see the very first galaxies in the universe in ordinary visible light?
35:37Only if optical telescopes also take a giant leap in technology and head for the skies.
35:48Liftoff of the space shuttle Discovery with the Hubble Space Telescope, our window on the universe.
35:53NASA launches the most famous telescope ever built.
36:00If you ask any person on the street to name a telescope, they will say the Hubble Space Telescope.
36:08The Hubble Space Telescope is probably the most productive telescope in history.
36:14It has been compared to the time when Galileo lifted his telescope to the sky for the very first time.
36:23The 12-ton Hubble Space Telescope is a fitting tribute to the man who first took us beyond the edges of our galaxy.
36:33It bursts through Earth's atmosphere and is released into orbit 370 miles above us.
36:40Ever since Hale built his observatory on a mountain top, astronomers have dreamt of having a telescope in space.
36:59Here, far above the interference of the Earth's atmosphere, there is no haze, smog or cloud to obscure the light streaming in from the universe.
37:11Putting a telescope in space gives us an incredibly clear view of the universe.
37:18We have seen further and deeper the Hubble than any other telescope in history.
37:24And Hubble is looking at light that is visible.
37:29What we are able to do with the Hubble is essentially capture the images as though you had two-meter eyes and you were in a vacuum and you could hold them open for a week.
37:39This is what you would see.
37:42They are not computer creations, they are actually digital pictures that you can actually see.
37:47The crystal clear images taken by Hubble are some of the most extraordinary visions of space ever seen.
37:55The remains of exploding stars streaming through space.
38:02Vast clouds of gas and dust where new stars are being born.
38:07Distant galaxies spiraling in giant disks and colliding to create super galaxies.
38:16My favourite image, I think, must be the butterfly nebulae.
38:22It's a nebulae that has gas streaming out at 600,000 miles an hour.
38:27Telescopes are time machines.
38:42We are seeing photons that actually started their journey 13 billion years ago and have taken that long to traverse interstellar space to us.
38:49And so you are not only looking out into space, you are looking back in time.
38:57In 1995, Hubble's ability to look back in time is put to the test.
39:04Astronomers decide to turn its gaze onto one dark point in the universe, just to find out what they can see.
39:13We picked one tiny point in the sky in which there was essentially nothing there or nothing special there.
39:23We stared for 10 days at a single dark spot on the sky.
39:27It is as if Hubble is peering through a tiny keyhole of our Milky Way galaxy to the universe beyond.
39:35The size of the spot that we looked through was no more than a drinking straw.
39:40What Hubble sees is extraordinary.
39:45And what we saw were 10,000 galaxies in that single spot.
39:50Every point of light that you see in the image represents a galaxy with a hundred billion stars like the sun.
40:02The image is called the Hubble Deep Field.
40:06It shows light from galaxies four billion times fainter than anything we can see with the human eye.
40:15Light that set out on its journey billions of years ago.
40:20If there is something that gives you a sense of the size of the universe and its depth, it's this kind of image.
40:27Every time the Hubble Space Telescope has been serviced by astronauts, the camera has been upgraded.
40:35After NASA's final mission in 2009, a new deep field image reveals the furthest galaxies ever seen, only 600 million years after the Big Bang.
40:50We are seeing back as far as we can see because we are seeing back to the time of the birth of the galaxies.
40:59The Hubble Space Telescope is taking images that continue to amaze us.
41:04I believe that Hubble Space Telescope in some sense has been really unique in the history of science.
41:13It has taken really the excitement of discovery and has made it, you know, to belong to every home, to humans all across the globe.
41:30Hubble has revealed the mysteries of our cosmos in stunning glory.
41:39Now it is working within a vast network of modern super telescopes to investigate a discovery that has rocked the world of astronomy.
41:49A discovery that threatens to turn everything we thought we knew about the universe on its head.
41:55An enigmatic force called dark energy.
42:05Dark energy is the most mysterious thing we've ever discovered.
42:10It's an energy that seems to be created out of nothing, out of the vacuum.
42:16But we have no idea what it is.
42:19Dark energy's discovery comes as a complete surprise.
42:23In the mid-1990s, on Mauna Kea, Hawaii at the Keck Observatory, a team of astronomers, including Alex Filippenko, is scouring the distant cosmos.
42:40They know the universe and expanding.
42:45But will it really expand forever?
42:50They have a theory.
42:52The universe might actually stop expanding and start slowing down.
42:57Just like when I throw this apple in the air, the gravitational attraction of the earth on the apple slows it down and eventually stops it and reverses its motion.
43:08So too, all the galaxies pulling on each other could slow down and ultimately stop the expansion of the universe.
43:16To be followed then by the collapse of the universe into a big crunch.
43:19So is the universe really beginning to fall back in on itself?
43:27To measure the speed of the very edges of space, astronomers need the most powerful telescopes on earth.
43:33The giant mirrors of the Keck telescopes are 33 feet in diameter, made not from one single disc of glass, but 36 hexagonal mirrors working together.
43:52They give a single image of exceptional clarity.
43:55The Keck telescopes are really fantastic devices.
44:02They can allow us to see galaxies that are literally at the visible edge of the universe, 10, 11, 12 billion light years away.
44:12But to find out how far away these distant galaxies actually are, astronomers need a standard candle,
44:20a star that will act as a cosmic yardstick.
44:25But the Cepheid variable stars that Edwin Hubble used are too faint at the extremities of the cosmos.
44:33The astronomers need to hunt for an especially bright kind of star inside the furthest galaxies.
44:41The deaths of these stars cause some of the most devastating explosions known to humankind.
44:49They are called supernovae.
44:53A supernovae is quite literally an exploding star.
44:57Now most stars don't explode at the end of their lives, but a few completely disrupt themselves in a colossal titanic explosion.
45:08And not just any type of exploding star will do.
45:11They are looking for a type of supernova that explodes with a very intense and consistent brightness.
45:19A type 1A.
45:22They go off as a gigantic nuclear runaway.
45:26They are essentially a gigantic nuclear bomb.
45:29In the most distant galaxies of the universe, they find what they are looking for.
45:34Type 1A supernovae.
45:37That looks good.
45:38There it is.
45:39There it is.
45:41Look at that.
45:42It's a little bit fuzzy.
45:43Now, they measure the redshift to calculate how fast these distant galaxies are moving away.
45:49Finally, in 1998, after years of research, they come to a shocking conclusion.
45:59The expansion of the universe isn't slowing down at all.
46:03It's speeding up.
46:04Much to our surprise, we found that the universe is expanding faster now than it used to be.
46:12So instead of slowing down, it's been speeding up.
46:15So it's like the apple goes zoom like that.
46:18A completely fantastic conclusion.
46:22A mysterious force that no one can see is defying gravity.
46:27Pushing the universe apart faster than ever.
46:30It is the force astronomers now call dark energy.
46:36There's the possibility that Einstein's gravity is incomplete.
46:41That we don't understand gravity.
46:42There's a possibility that it could change some of the fundamental laws of physics.
46:47But what dark energy actually is, and what it will do to our universe, remains a mystery to this day.
46:56Dark energy is one of the keys to understanding the fate, the ultimate fate of the universe.
47:04Is it going to expand forever?
47:07Will it continue to speed up?
47:09Will the speed up speed up?
47:11In which case, the whole universe gets ripped apart.
47:14The one thing astronomers do know is that dark energy makes up most of the universe.
47:20We discovered since that this dark energy is some 72% of the energy density of our universe.
47:30And yet we don't know what it is.
47:32I mean, just so that you understand the level of the puzzle.
47:36I mean, you know, about 70% of the surface of the earth is covered with water, right?
47:41Imagine we didn't have a clue what water was.
47:44This is the situation we're in.
47:50As if one invisible mystery isn't enough, scientists at NASA's Jet Propulsion Lab are investigating an equally mysterious invisible substance.
48:01Dark matter.
48:05Dark matter is basically invisible.
48:06We can only see it by looking at how it distorts things that are behind the dark matter.
48:16Images taken by the Hubble Space Telescope are now helping to reveal where dark matter can be found in the universe.
48:25Hubble's images show that this invisible substance is bending light.
48:31A good analogy is a pool of water.
48:35If you went out and you threw a penny into the bottom of the pool, you would look down at that penny and you can see the penny very clearly because the light from the penny is coming through the water.
48:46The water is essentially invisible.
48:48But the shape of that penny is distorted because that light travels not a straight path, but a slightly curvy path through the water to come to our eye.
48:56Dark matter has a similar effect.
49:00It exerts a powerful gravitational pull on light from distant galaxies.
49:06So what we're looking at here is light from a distant galaxy coming to us through this dark matter distribution.
49:16And as the light goes through the dark matter distribution, the path of the light is bent.
49:22Astronomers calculate that dark matter makes up 23% of the universe.
49:29Add that to dark energy and that leaves just 5% of the entire universe that is not invisible.
49:37So after 400 years of searching the heavens with telescopes, we still have 95% of the universe to reveal.
49:51And a new quest is beginning.
49:55A new generation of telescopes, millions of miles in space, high on mountain tops and deep below the earth, is gearing up to change our understanding once again.
50:15Telescopes are actually at the forefront of changing the way we think of the universe because it's the only way to see the universe.
50:22These big giant new telescopes are trying to address some fundamental questions.
50:28What's the nature of the universe that we live in?
50:30What is the stuff that makes up the universe?
50:32Could there be life elsewhere in the universe?
50:35The most sensitive scientific instruments today are not just looking at detectable light.
50:42They are searching for the invisible.
50:45And they will reveal mysteries of the cosmos beyond our wildest dreams.
50:49There's a whole hidden universe out there and that's what we're trying to discover.
50:55Since the time when telescopes were first raised towards the heavens, we have been hunting the edges of the universe.
51:03Revolutions in technology and the race to build bigger, higher and even in space have given us discoveries that have been revelatory, earth shattering and profound.
51:19We now know how little we are compared to the extraordinary size of our universe.
51:27We are even on the brink of discovering planets with the building blocks for life.
51:33Are there earth-like planets? Could there be life elsewhere in the universe?
51:37One of the exciting things about these big telescopes, they're very likely to give us the answers to these questions.
51:42At each stage, we have pushed the boundaries of our universe further.
51:49Beyond our planets, beyond our galaxy, beyond the hundred billion other galaxies, and virtually back to the Big Bang and the beginning of time.
52:00Telescopes are changing everything we thought we knew about our tiny planet and its true place within the cosmos.
52:12Who knows what they will reveal in the future?
52:17If we're going to look back at another hundred years, I think the whole world and our view of it will be transformed yet again.
52:23We'll be transformed yet again.
52:24We'll be transformed yet again.
52:25We'll be transformed yet again.
52:53Cool Hughes
52:55are you?
52:56Totally?
52:57Are you?
52:59Wow!
53:01Is this perfect super different in the future?
53:04Yes you haven't.
53:05So since podcasts have Temczynsareer?
53:08Yes, it's perfect just that's wonderful too.
53:10The only three situations have fun of time.
53:13You have seen____ of what 적ased with people that are not.
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