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00:00Scientists are brushing up upon age-old questions that used to be the purview solely of theologians.
00:08Last century, a radical idea about the origin of everything was born.
00:14It would become the most famous theory in all of science.
00:18Fred Hoyle, in a rather derogatory way, described it as a Big Bang.
00:23As the Big Bang theory evolved, it made predictions that were only confirmed by accident.
00:31This radiation was discovered using this radio antenna that wasn't even looking for it.
00:38What's coming out of this thing had to come from somewhere.
00:42Had science discovered the moment of creation?
00:45We're looking at the infant pictures of the baby universe.
00:50But the Big Bang theory had its challenges.
00:54There were several problems that could not be explained without conspiracies.
00:59Cosmologists were forced to propose a mind-blowing scenario to fix the difficulties.
01:06I wake up my wife and I said, I think that I know how the universe was born.
01:12They claimed that the universe expanded by trillions of times in a tiny amount of time.
01:20An idea called inflation.
01:23It took the observable universe and flung it apart so fast that space itself expanded faster than the speed of light.
01:32But could this be true?
01:35Or was there a flaw in the whole idea of the Big Bang itself?
01:39There should be a tell-tale signature all over the sky.
01:42An intrepid team of scientists built a telescope in one of the most inhospitable places on Earth.
01:50Looking for the answer.
01:52It could be one of the greatest experiments of all time.
01:56But the team would face intense challenges and controversy as they battled to answer the greatest scientific mystery of them all.
02:05So, is the Big Bang right?
02:08So, is the Big Bang right?
02:09Wondering where the universe came from is the biggest question anyone can ask.
02:26All the billions of galaxies, the untold trillions of stars and planets stretching out over unimaginable distances.
02:38What could possibly have made them?
02:40For some, the question itself was irrelevant.
02:46Because the universe never had a beginning.
02:49It had just always been.
02:51Well, our lifespans as humans are very short compared to the age of the universe.
02:57So, during our lifetimes, the universe doesn't appear to do very much.
03:00If you couple that with people's limited ability to observe distant objects, the universe did appear very static.
03:07But for others, a moment of creation better fitted their beliefs.
03:12There was a persistent belief that the universe must have been created as we see it, and generally that was attributed to God.
03:25Yet other religions believed that the universe might be an everlasting cycle of birth and death.
03:31These ideas that humans have had about whether there's a beginning to everything or something that's more cyclical, that is everlasting, that didn't have a beginning, that didn't have an end.
03:43These are things that have absolutely reflected now in the questions that we're asking.
03:47Now that we actually have data and we're kind of doing this from a scientific point of view, not a religious point of view.
03:54Most scientists at the start of the 20th century thought the universe was static and had always been.
04:02But in 1915, preconceptions about the origins of the universe would be challenged when Albert Einstein published a paper.
04:12He came up with this beautiful theory of general relativity, which tells us how the whole of space-time should behave.
04:21It tells us that if you put mass into it, a bit like throwing a ball onto a rubber sheet, it deforms space.
04:28At its core, general relativity said that neither space nor time are rigid. They are continuously distorted by matter.
04:38But Einstein was troubled by the implications of this on a cosmic scale.
04:42He came to realize that his new theory of relativity said that space actually should be changing.
04:52If you just put masses into space, the gravity of them should actually try and pull the space between them back together and should actually shrink space.
05:02But Einstein hated this idea. Einstein thought that the universe was static.
05:07And so he came up with this thing that he called the cosmological constant.
05:12So Einstein's cosmological constant is a kind of a fudge factor that he inserted into his equations.
05:17And he did this really just on grounds of prejudice. You know, towering genius that he was, he somehow felt compelled to fix his equations to prevent the universe from expanding or contracting.
05:30In 1922, a Soviet scientist called Alexander Friedman began corresponding with Einstein.
05:36He was sort of inspired by Einstein's new theory of relativity and tried to apply them to the whole universe.
05:45And, you know, he quickly realized, as Einstein had, that the natural behavior of such a universe was to expand or contract and that being perfectly stable was a kind of vanishingly unlikely knife-edge point between those two possibilities.
05:56He said, depending on the kind of initial conditions, depending on how you started things off, space could be growing, but whatever it is, it shouldn't be static, it shouldn't be unchanging.
06:06And so he wrote a couple of scientific papers, but Einstein didn't like it.
06:15It wasn't long before others would challenge Einstein's position.
06:19Working independently of Friedman was mathematician and priest, Georges Lemaitre.
06:24Lemaitre was a very remarkable man. He had a distinguished war career. He was awarded the Croix de Guerre by the King of Belgium for his service in the First World War.
06:37A few years after Friedman, he took a step further. He said, well, if the universe is indeed growing, then it must have come from somewhere. It must have had some beginning. He called it a cosmic egg.
06:51Lemaitre was the first to suggest that the beginning of the universe would also be the beginning of time.
06:58He called the beginning of the universe a day without a yesterday.
07:03Einstein, when hearing about this for the first time, called Lemaitre's math elegant, but his physics atrocious.
07:10But Lemaitre had an ace up his sleeve.
07:15He also figured out what we should expect to see around us if the universe were in fact growing.
07:24And so we should see galaxies moving away from us.
07:29And the ones that are further from our Milky Way should recede from us faster than the ones close by.
07:36In a paper published in 1927, Lemaitre had given a prediction of how fast the expansion might be, depending on how far away we look.
07:51Well, this is where the experimentalist comes in, and it always pays to look and let the universe tell us what it thinks.
08:01And Lemaitre was already acquainted with one of the world's greatest astronomers, who was studying the most distant parts of the visible universe.
08:11So, Edwin Hubble studied the motion of galaxies, and all the galaxies that he looked around at were all receding from us.
08:21And that was exactly the kind of prediction that Lemaitre would make, that the universe would be expanding.
08:29In 1929, Edwin Hubble published his results that concurred with Lemaitre's predictions.
08:35The further away the galaxies he observed were, the faster they were moving away from us.
08:42He calculated that the most distant galaxies were moving away at thousands of kilometers per second.
08:49Einstein, in fact, visited Edwin Hubble and his telescope here in Pasadena,
08:54and came to the conclusion that putting in this cosmological constant was a mistake,
08:58and accepted the idea that perhaps, you know, this was possible.
09:01The universe was actually a dynamic place, expanding from a beginning time.
09:07It was rapidly proposed, what's going on?
09:10It's not that there was an explosion centered on our galaxy.
09:14It's just that the entire fabric of space itself is expanding.
09:17If you think of such a picture, a kind of expanding grid, where the galaxy is on the grid points,
09:22it turns out that every point, as it looks out to other points, sees all the points receding.
09:27It doesn't matter where you are, every point is the center of the expansion, as it were,
09:31and the galaxies are just being carried along in the flow of the expansion of space.
09:39Now that most of the world's cosmologists believed that the universe had a definite beginning,
09:45they could start to figure out how it might have worked.
09:50Scientists began to develop ideas about what should happen in these very hot conditions in the early universe.
09:56I think the biggest advance was by a fellow named George Gamow.
10:02He and his collaborators looked at the possibility that elements were cooked up in the early universe.
10:10And this is what's called, this is called primordial nucleosynthesis.
10:15Gamow theorized that at the very beginning, there was only intense heat and energy.
10:20Over the next few seconds and minutes, the energy condensed into the first atoms.
10:26But they were incomplete atoms.
10:28The baby universe was too hot for electrons to become attracted to the atomic cores.
10:32And so you have this very short window in which you can create cores of atoms, and you just have long enough to do that before the universe then cools down enough that you can't do it, a bit like turning your oven off.
10:47You would only be able to develop very light elements like hydrogen and helium, a little bit of lithium.
10:54And this mixture of elements was then remarkably consistent with what astronomers can actually see now out in the skies around us.
11:03But Gamow and his colleagues also made a prediction of immense importance.
11:08He also found that as the universe expands, it should leave a remnant radiation background.
11:16370,000 years after the beginning, the expanding universe would have cooled down enough for the electrons to become attracted to the incomplete atomic cores.
11:26So the significance of this moment when the electrons and protons come together, which we call recombination, is that not only is the full hydrogen atom formed for the first time, but light rays now travel freely through space, eventually towards us.
11:47And so the prediction was that we should be bathed in this primordial radiation of light rays that have indeed been traveling for billions of years since that beginning of the universe time.
12:04Gamow and his collaborators called this first visible remnant of creation the cosmic microwave background.
12:13This entire process of the universe expanding from an ultra dense, ultra hot state and forging matter from energy was given its famous and misleading name by a skeptical British cosmologist called Fred Hoyle on a BBC radio program.
12:32In a rather derogatory way, he just described it as a big bang.
12:38Well, it caught on like these things do.
12:41When people call it the Big Bang, they almost always picture the wrong thing. They picture a firecracker at a place and a time. What we actually observe is the infinite universe expanding into itself with no actual first moment.
12:58People are shocked when I tell them this. We've been told the wrong thing by astronomers and science writers for generations and it's hard to take the meaning of the words that Fred Hoyle gave us.
13:08If the Big Bang really did happen, then finding the cosmic microwave background that Gamow and his colleagues had predicted became of vital importance.
13:21The challenging thing is that it would be very difficult to find because as the universe has grown and cooled down, this light from the early universe has stretched its wavelength well beyond the waves that our eyes can see into microwave wavelength.
13:40And they should now be extremely cold, almost absolute zero.
13:48The temperature of this cosmic microwave background, or CMB, was carefully predicted by a Princeton scientist called Jim Peebles.
13:58Some of his colleagues then set about trying to find it.
14:03And then, completely serendipitously, this wonderful thing happened.
14:06When I took a job at Bell Labs, they had a unique radio antenna, which we planned to look at some special things in radio astronomy with.
14:19And what we found was something we weren't looking for.
14:23Rather than collecting light that our eyes can see, radio astronomy uses antennas that capture light of much longer wavelengths, like microwaves and radio waves.
14:34Only 26 miles from Princeton University, Robert Wilson and his colleague Arno Penzias wanted to use their radio antenna to measure the emissions coming from the halo of gas around our own galaxy.
14:50But in order to do so, they would first need to calibrate it.
14:54Radio astronomers aim their big antennas at a source they're interested in and get a signal, but then they turn them off to the side a little bit, and so they measure the difference between near the source and on the source.
15:10Wherever they pointed their telescope, they always found background radio emission, a kind of noisy hiss at a certain frequency.
15:18The background should have been quite small, and so we had a real conundrum that the antenna was producing more noise than we could understand.
15:31Arno and Bob set about trying to locate the source of the noise that was ruining their experiment.
15:37Yeah, we had a checklist of something like nine different things, but things like we had a perfect view of New York City.
15:46Could it be that the city is noisy and that the side lobes of our antennae were picking that up?
15:53Well, we had the perfect instrument. We turn it around and we look at New York City. Nada.
15:57They wondered if the troublesome signals were coming from the ground, and so they wheeled a cart around the antennae with the radio source in it.
16:08But again, nothing.
16:10Bob and Arno were narrowing down their list.
16:14But what if it was something inside the antennae that was causing the problems?
16:19There was a pair of pigeons who had taken up roost in the antennae.
16:23They would fly up just about into the cabin of the antennae, and it must have been a nice, toasty place to be.
16:31It wasn't necessarily the pigeons that were suspected of causing the interference, but something they were leaving behind.
16:39There was this white dielectric material all over the inside of the horn reflector, and so we thought it could be radiating.
16:48We first got a trap, and put it where the receiver normally would be, and caught the pigeons.
16:55We put them in a cardboard box, and mailed them as far away as we could in the company mail to a pigeon fancier in Whippany, New Jersey.
17:03Well, he took a look at these pigeons and said, these are junk pigeons, and let them go.
17:08Well, a day or so later, here are the pigeons back.
17:11So that didn't work.
17:15Our technician brought in his shotgun, and in the name of science, dispensed with the pigeons.
17:26In short, none of the things we could think of and do anything about actually made any difference.
17:31A hint at where their problems might lie came when Arno had a chance conversation with a fellow astronomer.
17:40He said to Arno, what's happening with your crazy experiment?
17:44And Arno laid it on him.
17:45We've got this excess noise in our antennae.
17:48We can't find it.
17:49He said, you ought to talk to Bob Dickey at Princeton.
17:51Bob Dickey was the colleague of Jim Peebles at Princeton University, whose team were already actively looking for evidence of the radiation predicted by the Big Bang Theory.
18:04Although Peebles had calculated what kind of radiation they were looking for, their experiments were only being calibrated and had yet to begin.
18:13The team were eating lunch together when the phone rang.
18:16Dicky picked up the phone and they heard atmospheric radiation, sky temperature, antenna noise, all the things they were interested in.
18:29Dicky put down the phone and said, boys, we've been scooped.
18:36Robert Wilson and Arno Penzias had accidentally found what Jim Peebles and George Gamow had predicted.
18:42We invited them over, they looked at our antennae and all the measuring system and agreed that we'd done the right thing.
18:50We went down to the conference room and they told us about how a Big Bang might produce a universe full of radiation.
18:58Wilson, Penzias and Peebles were all awarded Nobel Prizes for their parts in this momentous discovery.
19:05And suddenly it changed everything.
19:06The fact that we see the galaxies expanding around us, we see the elements in the right abundances that you'd expect from a hot Big Bang.
19:15And then we see this radiation coming from all directions in the sky.
19:20Those three things became the pillars of the Big Bang Theory.
19:23So now scientists had a picture of a universe that expands from a Big Bang, cooks up basic elements in the inferno and leaves behind a detectable background.
19:34But that couldn't be the whole picture.
19:38The hot Big Bang model was on pretty firm footing, but there were definitely some puzzles.
19:43This CMB radiation did appear indeed to be the same temperature everywhere.
19:51And that's really weird because you're receiving a ray of light from all different directions and those rays of light have traveled for 14 billion years to reach you.
20:00And they could only have achieved the same temperature if they were once in contact.
20:04There was a second problem, which is that the universe seemed to be something known as flat.
20:16The universe is observed to have very close to what's known as spatial flatness.
20:21What is spatial flatness?
20:22So if you imagine yourself on the surface of the Earth, the Earth locally looks very flat, meaning that if you go to a sidewalk and you draw a triangle with three straight lines to it,
20:32you will get, when you sum up those three angles, 180 degrees.
20:37However, if you make that triangle bigger and you put one vertex of the triangle in Bangkok, one in Mexico City, and one at the South Pole,
20:46that triangle has about 270 degrees between its three angles when summed together.
20:52Now, imagine going off the surface of the Earth, pick three stars, measure the angle that they subtend, and make the triangle and observe their three interior angles and add those up.
21:02It turns out, no matter how big a triangle you make in the universe, those angles always add up to 180 degrees.
21:10So it's very, very striking that the universe was fine-tuned to parts in a billion or a trillion in its curvature right after the Big Bang.
21:18How could that possibly happen?
21:19Physicists were pretty confident about their model of how the universe worked, down to a time of about one second, where the conditions had to be right to start to form these light elements.
21:33So how flat would the universe have to have been then to explain how flat it is now?
21:39And it has to be extremely flat to, you know, parts in ten to a large number.
21:45And that seemed just very odd that that would be the case.
21:48So the solution to both of these problems is something called inflation.
21:55I didn't expect that I'm going to be a cosmologist.
21:59I thought that I'm going to work on particle physics, but then unexpected things happen.
22:05The original theory of cosmic inflation was built independently by Alan Guth in the U.S. and Alexei Starobinsky in the Soviet Union.
22:17Inflation introduced a new phase at the very beginning of the universe, before the formation of atoms, in which there was a sudden accelerated expansion of the universe.
22:30Inflation would have been staggeringly brief and increased the size of the universe by a scale that is hard to comprehend and even to say.
22:42In much less than a trillionth of a second, the universe would have expanded by 100 trillion trillion times.
22:50And you would very rapidly blow up a space smaller than an atom to, you know, larger than a galaxy very, very, very fast.
22:59This means the overall universe is much bigger than we can ever observe from our own bubble within it.
23:07So it's a very fundamental rule in physics that nothing can move through the fabric of space faster than light.
23:13But that actually says nothing about the fabric of space itself.
23:16The fabric of space itself can expand faster than the speed of light in these theories.
23:21There's nothing to prevent that.
23:22And that's what happens during the inflationary phase.
23:26The distance between points is growing faster than the speed at which light can close the gap between those two points, so to speak.
23:34But there was a brief moment before inflation began in which the universe expanded much more slowly.
23:40Those regions that we observe on the sky being the same temperature, they were all connected at this earlier time before the universe got ripped apart by inflation.
23:50Inflation also explains why the universe is so flat, because that expansion takes whatever geometry the universe had prior to inflation and stretches it out tremendously.
24:01So that local region that we can see today looks very, very flat.
24:04It's like if we're on the surface of the Earth now, we know the surface of the Earth is curved, it has continents and oceans, and suddenly through stretching all we can have access to is our backyards.
24:19Well, now our backyard is going to look rather locally flat.
24:22The original theory of cosmic inflation utilized a core concept taken from quantum theory that suggests that there can never be such a thing as zero energy.
24:36Even a random spot in the vacuum of space has quantum particles fizzing in and out of existence.
24:44In this picture of the Big Bang, the tiny and seemingly empty speck from which the universe would grow was bursting with potential energy.
24:52So this is a strange way of producing lots of particles, lots of energy practically from nothing.
25:02In models for inflation, the universe that would have been extremely compressed was composed of like an energy field.
25:11And it would be the stored up energy in that field that would be released a little bit like releasing a spring.
25:18They would have this sort of potential energy, this energy that's raring to go.
25:23This newly unleashed energy and the rapid creation of space would propel a chain reaction of bubbles of potential energy exploding.
25:32And as a result of it, the universe does not look like one bubble, but instead it looks like bubbles producing bubbles, producing bubbles, producing bubbles forever.
25:45It becomes a fractal.
25:47So the classical picture of the universe, which is something big and round.
25:52No, it's not a big and round.
25:54It's something like a tree of universes growing like that.
25:57And this mechanism, with its random fluctuations, is ultimately responsible for us being here at all.
26:06So the idea of inflation is that all structure in the universe originated from quantum fluctuations during this hyperexpansion phase at a very early time.
26:16If the quantum fluctuations in the Big Bang were the correct description, plus inflation, then we should have roughly the pattern of hot and cold spots that we see in the sky and that should match with where the galaxies are today.
26:30Sure enough, they do.
26:31The current idea is gravity acts on the denser regions and stops them from expanding, pulls the material back together again to make a galaxy and then planets and stars.
26:41So we're here because of those spots in the Big Bang radiation, plus gravity, which is a pretty amazing result.
26:51But inflationary theory, in its original form, had a fundamental problem.
26:56This energy would sort of permeate space and would be expanding incredibly fast.
27:03And somehow you have to stop that from happening in a gradual and smoothly controlled way.
27:09For about a year or more, many different people worked on it.
27:15Stephen Hawking and his collaborators wrote a paper saying that it's impossible to solve this particular problem.
27:21But late one night, André had a brainwave.
27:27I wake up my wife and I said, I think that I know how the universe was born.
27:34During the summer of 1981, André wrote a paper on the modified theory, which he called New Inflation.
27:41And so what André Linde came up with was a different mechanism for gently sort of rolling into a smoother expansion than had been come up with to begin with.
27:55And in October, there was a conference in Moscow.
27:59Lots of brilliant people came.
28:01And one of them was Stephen Hawking.
28:03And they gave a talk at this conference and everybody got very excited.
28:07But next day, I came to the talk by Stephen Hawking.
28:10Unexpectedly, they suggested me to translate.
28:14Steve would say one word.
28:16His students said one word.
28:18I translated this word.
28:19It was about old inflationary theory.
28:22And then Stephen said, and recently there was an interesting suggestion about how to improve it by André Linde.
28:30And I happily translated.
28:32And next second, he said, but this suggestion is completely wrong.
28:36And for half an hour, I was translating why my own theory, which I just reported the day before, why it does not work, et cetera, et cetera.
28:50After the lecture, André asked Stephen if they could talk in more detail.
28:55They retired to a side room where, for more than two hours, they discussed André's modification to inflation.
29:01He said something and his student would say, but you didn't say that before.
29:06And this thing continued.
29:08I ended up in his hotel.
29:10He was showing me photographs of his family and we became friends.
29:15Hawking realized that Linde had solved the issues that were plaguing inflation.
29:21He had proposed a mechanism by which inflation could not only start, but gracefully come to an end.
29:27André was invited to come back to Cambridge and work with Stephen, where over the next year, they and their fellow cosmologists molded a simpler and more robust inflationary theory that became the centerpiece of Big Bang cosmology.
29:42By the late 1990s, cosmologists knew that there was some evidence for inflation, but they wanted to find a smoking gun that would tell them that it must have happened.
29:56And they were sure that it could be found in patterns within the cosmic microwave background.
30:01If inflation happens, a likely thing to come from it is this really particular signature that we're all searching for now with our telescopes.
30:12And it's an imprint of ripples in space time that would have been imprinted during that inflationary process.
30:21The patterns they were looking for are called polarization patterns.
30:27But what is polarization?
30:29Any given ray of light is a fluctuation in the electric field and a fluctuation in the magnetic field that are 90 degrees apart.
30:37And then this whole wave train is moving along the third direction.
30:41As you rotate around the direction of motion, these are other polarizations.
30:44So you have a continuous range of polarizations for each individual ray of light.
30:50The polarization properties of an individual ray of light can tell us a story about what has happened to the light on its journey to us.
30:59Now, most of those fluctuations we see in the microwave background, they're like a sound wave.
31:04It's a compression wave traveling through the universe.
31:07This first common type of fluctuation creates either a cross-like or circular pattern, which is called an E-mode.
31:16But there is another pattern called a B-mode.
31:20And this is the one that is crucial to finding evidence for inflation.
31:25In Einstein's theory, you can also have fluctuations in space time called gravitational waves.
31:31And they don't act like a density wave that compresses and rarefies.
31:35Instead, they squeeze space in one direction and stretch it in the other direction while they're propagating in the third dimension.
31:43Those fluctuations have a very, very specific signature.
31:47They will have imprinted a particular form, a particular swirliness, actually.
31:54And if we could detect this pattern of swirling, twisting polarization in the microwave background,
31:58that would be perhaps indirect evidence that inflation took place.
32:03If it could be observed to be truly cosmological, not caused by some systematic error in the instrument or in the galaxy or something else,
32:11that would be as close to what was called smoking gun evidence that inflation took place.
32:15In 1996, the European Space Agency, ESA, started planning a space mission called PLONK to map the cosmic microwave background at very high resolution.
32:29In the sky maps, you will see the different colors show the temperature variations.
32:33Blues and yellows are hottest, through to greens and then red for the coldest areas.
32:40Initially, we were not planning to measure polarization when we first started out with the project.
32:48PLONK's prime mission was to do the ultimate job measuring the temperature variations in the microwave background.
32:53People had not really realized how important and how much information polarization signals would carry.
33:02So it was not the primary goal.
33:05A separate project from around the same time, called Boomerang, didn't go into space,
33:11but used balloons to make high-sensitivity observations of the CMB.
33:15My last year as a graduate student, I worked on developing new technology detectors for Boomerang.
33:24Now, the detectors that were developed on Boomerang turned into the detectors on the PLONK satellite,
33:31and they were developed here at JPL.
33:33In the midst of PLONK's development, the science team got more and more interested with polarization measurements.
33:40So I was also a postdoc at the California Institute of Technology.
33:43I was really fascinated by building a telescope that was only sensitive to the polarization of the microwave background.
33:50Myself and Brian Keating, we came up with an approach that we call B-modes or bust.
33:56We proposed to the Caltech president at the time to get some seed money.
34:00We said we're going to look for this inflationary gravitational wave signal to look and see if we can see it,
34:07and build an experiment that's just tailor-made to do that one thing and do it really well.
34:10We would have loved to take it into space, but space-borne experiments will cost you anywhere from 100 to 1,000 times more than their ground-based equivalent.
34:21And we believe we could do it from the ground if we went to an exquisite site like the South Pole.
34:26Brian, Jamie, and their colleagues established BICEP, background imaging of cosmic extragalactic polarization.
34:36I started working on it full-time, 2007, 2008.
34:40The stage was set for a battle between two very different missions, both sharing mostly related technology.
34:51But for the Planck team, they still did not really believe that BICEP was a competitor.
34:56Within the Planck community, we were not really all that concerned.
35:02What BICEP was trying to achieve was quite a different thing, using quite a different approach.
35:07The really novel thing about BICEP is the telescope.
35:12So we're looking for swirly patterns in the polarization on scales several times bigger than the full moon.
35:17Now, you don't need a very big telescope to do that.
35:21A telescope of 25 centimeters or so would be just fine.
35:25And actually, that brings a huge number of advantages.
35:28Because I can take that small telescope and I can spin it around to take out any polarization that's in the instrument.
35:34It's really hard to do that with a large telescope.
35:37The small size of the BICEP telescope also makes it easier to cool.
35:41The ancient light of the cosmic microwave background is now extremely cold.
35:47So in order to see it, the telescope itself must be kept very cold.
35:52I can cool that whole telescope down to four degrees above absolute zero.
35:56And that's very hard to do with a large telescope.
35:59The first generation of BICEP used these kinds of detectors we developed for Planck called a bilometer.
36:05And the basic idea is you take something that absorbs, in this case millimeter wave radiation,
36:09and you stick a sensitive thermometer to that absorber.
36:13And if any radiation hits the absorber, you measure the increase in temperature using the thermometer.
36:21The BICEP experiment is located at the Amundsen-Scott South Pole Station in Antarctica.
36:28The South Pole is flat. It's featureless. It's cold. It's barren. It's dark.
36:33Literally six months of the year, the sun is below the horizon.
36:35And we pay one person to sit there for the next nine months of his or her life.
36:40But we call that person a winter over.
36:42And we always joke, we're going to pay you $75,000, and all you have to do is work for one night.
36:47Because that's all they'll be there for.
36:52So it would sit there at the South Pole, and it would scan back and forth for years on end.
36:57Accumulating data, storing the data, we're testing it, we're analyzing it, we're looking for artifacts.
37:02BICEP-1 was created in 2001, and we deployed it in 2005.
37:08It took data from 2006 till 2009.
37:11We then decommissioned it to make way for a bigger, better instrument called BICEP-2.
37:16Those first three years really showed that the method worked really, really well.
37:21Meanwhile, much of the field was struggling with larger telescopes to do these kinds of measurements.
37:25After 13 years of careful development, the European Space Agency was ready to launch the Planck spacecraft in May 2009.
37:39I was very happy to be part of the Planck collaboration. I joined when it was about to be launched.
37:49So basically you can think of Planck as a camera that has a lens of about one and a half to two meters in diameter.
37:57It has an array of about 50 detectors or so.
38:06While we were pleased with the devices on Planck, BICEP didn't have as much sensitivity as we ultimately wanted.
38:13We needed to increase the detectors from dozens to hundreds to thousands to tens of thousands.
38:19And the way to do that is using the same methods that we use to make computer chips.
38:27You want to lithograph the entire structure and reproduce them many, many times.
38:32And in fact, you don't want to just reproduce the billometer, you want to produce everything about it.
38:37How it couples to light, which we use a printed antenna, and how we select the frequencies.
38:42All this is just lithographed on the device itself.
38:46So you build an instrument, you measure the sky with it for a few years.
38:49You build more detectors, more sensitivity, more data, so you can improve the sensitivity faster.
38:54So that's been the pattern. There was BICEP-1, then there was BICEP-2, then there was Keck Array.
38:59But basically it's just a continual arms race of improving sensitivities.
39:04Between 2010 and 2012, BICEP-2 collected thousands of scans of the sky.
39:10BICEP-2 was observing a very small part of the sky with as much sensitivity as they could.
39:18They chose the patch of the sky which they thought would be the cleanest possible.
39:23During the same period of time, ESA's Planck spacecraft revolved once every minute,
39:30slowly scanning the entire cosmos over the months.
39:33The measurements that we take, they do not reveal things instantaneously.
39:42The data take years to acquire, they can take a year or more to analyze.
39:47We have four scientists representing the ISEP-2 collaboration, John Kovac.
39:53People have a slightly ivory tower view of science sometimes.
39:56It's like we all sit in the common room, smoking our pipes and being great chums with each other.
40:01Science can be fiercely competitive.
40:04People's careers depend on the results that you publish ahead of other people.
40:08So the theory of cosmic inflation, which attempts to explain the start of the Big Bang itself,
40:14predicts that the early universe will contain a background of gravitational waves
40:18that produce patterns of polarization called B-modes.
40:22Suddenly there was an announcement by the BICEP-2 team claiming that they have observed primordial gravitational waves.
40:29Today we're going to be reporting the detection of B-mode polarization as seen by the BICEP-2 telescope
40:36that matches very closely the predicted pattern.
40:38This was big news in our community, so many of us watched the results together.
40:44It's amazing.
40:46You talk about it being thrilling, maybe it was in a way, but it was also terrifying.
40:51Up here today are the co-leaders of the BICEP and Kekare series...
40:54Um, well, I think the first reaction was, uh, wow.
41:00...the major collaborators that you see in BICEP-2 over the past...
41:03...because it was presented as a clear-cut case.
41:05UC San Diego, Brian Keating's group there...
41:08There are considerable challenges to separating the E-modes and the B-modes accurately enough.
41:13We had to develop new mathematical techniques to allow us to do that.
41:17When we applied those techniques, we started to be able to see a B-mode
41:20detected with statistical significance for the first time.
41:24And this was, of course, tremendously exciting.
41:26It was what we had been trying to do for all of these years.
41:29The pattern is very distinct. However, the signal is very small.
41:33And they said, we have found gravitational waves.
41:35This is yet another confirmation of inflationary theory. Everything was great.
41:40We felt that the polarization pattern on the sky was real.
41:44As Clem Pryk would later say, we, instead of seeing a needle in a haystack,
41:47we observed what was later, he called, a crowbar in a haystack.
41:52Okay, so this is the actual polarization pattern map as measured by the BICEP-2 telescope.
42:00Think of it as little sticks, little sticks indicating the direction and the magnitude of the polarization.
42:06The most reasonable interpretation is that it is gravity waves written in that microwave background pattern.
42:11And those gravity waves come from the inflationary epoch at a tiny, tiny fraction of a second after the beginning.
42:18The BICEP team had made an announcement that suggested that the holy grail of signals had been found.
42:34One that would show for certain that inflation had occurred and that the Big Bang model was correct.
42:41But there were troubles brewing.
42:43But if other people have other data and they can go in and say, actually, we don't see the same thing as you, that's the risk you run.
42:50As you may have gathered, it seems traditional now that each experiment is very secretive about what it's, what it's doing.
43:00As soon as people started to look at the paper and at the details, they realized that, hmm, maybe, maybe there are some issues here.
43:09Now, we had only measured the sky at one frequency, basically where the CMB is brightest.
43:19Now, it's possible that we would have contamination from our own galaxy, from polarized dust.
43:25The issue is that we had the means, Planck, had the means to measure the dust part of the signal.
43:30There were no measurements available to our team at the time of the brightness of polarized dust in these faint regions.
43:39The Planck satellite team had this data, but we didn't have access to it.
43:47The BICEP team thought they had an agreement with ESA that the Planck team would provide them with data that would show the dust contribution to the BICEP signal.
43:55But it's not the way it played out in the end.
44:00We did ask, and they did not provide us the data.
44:03That could be, A, they didn't have it.
44:05B, maybe they did have the results and they were bluffing.
44:08C, this wasn't something that they could agree upon on our timescale.
44:16Well, of course, it was certainly not about destroying anybody or any group.
44:20It was about getting the good result, right?
44:23Well, so the first thing that happened is the Planck team put out a paper on the polarization in the diffuse sky, including our region.
44:34And it showed, indeed, that the polarized emission from the galaxy was bigger than we had assumed from models.
44:43The signal that we saw turned out to be dust emission.
44:47The thing that clears up scientific disputes and uncertainties is data.
44:54In order to get a clean understanding of the problem, you needed to use both sets of data.
44:59You couldn't do it with Planck only, you couldn't do it with BICEP only.
45:03And so we very quickly decided that we had to work together with their team.
45:10The two teams joined forces, and together they published the results of what had happened in this remarkable story.
45:18They jointly told the world that BICEP had not yet found evidence for inflation.
45:23Well, I thought, oh, man, that must hurt. That was tough luck for them. They were too eager.
45:30It's a bit embarrassing, perhaps, but I think being a skeptic about any result and getting independent confirmation, that's how science works.
45:37And, you know, the point here isn't how I feel. The point is, you know, how do we get to the best result?
45:45I don't think I was particularly sorry for them in the sense they did a wonderful job.
45:51I was sorry because it wasn't true, because it would have been scientifically much more exciting to actually have access to that signal and therefore to inflation and to a new part of knowledge in the universe.
46:09It is widely acknowledged that the BICEP team did great science, but at this time they were fooled by the galactic dust.
46:17They made a mistake, but on the other hand, they were the first to come to the verge of possible discovery, and they're still the best.
46:30Theoretical scientists like Andre need experimental scientists like Jamie, Brian, and Clem.
46:38A scientific theory is of limited use unless an experimenter can come along and prove that a theory is correct.
46:44And this is the story of the Big Bang.
46:49Edwin Hubble proved Lemaître right, that the universe must be expanding.
46:54Penzias and Wilson proved the theorists were right when they found the cosmic microwave background.
47:00But as we shall see, finding evidence for inflation is still the key objective.
47:05I think the consensus today in the community is that inflation is the best candidate for the phenomena in the early part of the universe, and so I think we should pursue this, no question about it.
47:23I'm involved in a project called the Simons Observatory, which is building a set of telescopes that are going to be in the north of Chile.
47:35So the Simons Observatory is a large collaboration spanning all seven continents of approximately 300 individual researchers and about 45 institutions.
47:46If you can't be in space, the two best sites are Chile and the South Pole for looking at this CMB radiation is because they're very dry.
47:53Bicep is also continuously pushing the envelope on their experiments in the South Pole, and both teams plan to build a healthy competition between them.
48:06So their goal is to compete with us head to head, and we'll see who does the best.
48:11The goal is to reach similar sensitivity to this radiation and to these gravitational waves from both of these locations on Earth.
48:20I see it as being important to have two complementary approaches to such an important potential discovery.
48:31I think it's very good that people are collaborating and sharing information.
48:37I think that's the way science ought to work.
48:45The best part about it is that no one can do it alone.
48:48One of the powerful lessons of Bicep 2 is that it will take the village of all of cosmology,
48:53that we will rely on the confirmation of sometimes our competitors.
49:00Looking down the horizon, we can perhaps envision a day where there will just be one experiment.
49:04So there is a concrete plan in the works for the ultimate ground-based CMB experiment, and it's being called CMB S4.
49:14The objective is to make observations from both South Pole and from Chile,
49:19with apparatus somewhat similar to the current experiments, but just a lot more of it.
49:23And so it's a kind of a mega-experiment.
49:25I'm sure that all the work that has been done so far, including the one from Bicep, will help in reaching that final goal.
49:36The Big Bang Theory attempts to answer the biggest question anyone can ask.
49:42Where do we come from?
49:44The theory has passed many challenging tests, and it is the best description of how our universe began.
49:51We have to be prepared that all these dedicated efforts may ultimately fall behind the unknowable screen.
50:00It may be that there is simply a limit to how much one can know about the earliest moments of the creation of the universe.
50:10The way I say it is, you imagine in your mind running the universe backwards, so while everything is compressed and compressed and hotter and hotter and hotter,
50:20and when you run out of imagination, that's what you call the Big Bang.
50:23And we may push the imagination a little farther, but eventually you probably still run out of imagination.
50:29The Big Bang Theory
50:30The Big Bang Theory
50:31The Big Bang Theory
50:32The Big Bang Theory
50:34The Big Bang Theory
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51:05Gracias por ver el video.
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