Three scientists won the Nobel Prize for their groundbreaking discovery of gravitational waves. These mysterious ripples in space and time were theorized by Albert Einstein and might reveal the secrets behind the birth of the universe.
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LearningTranscript
00:03The theory of cosmic inflation...
00:06On March 17, 2014, a team of astronomers made an announcement that triggered sensational headlines around the world.
00:15They've detected gravitational waves or ripples in what they believe is the oldest light in the sky.
00:21It's being called one of the greatest discoveries in science.
00:25By using a telescope at the South Pole, the researchers had detected a signal indicating gravitational waves, folds in the
00:36fabric of space and time that were made just fractions of a second after the Big Bang.
00:43This is the farthest back we will ever have seen in the history of the universe.
00:49This is the inside story of scientists who announced one of the greatest discoveries of the century.
00:56This would be one of the final confirmations not only of inflationary theory, but also the general theory of relativity.
01:06Only to have it called into doubt.
01:09As happens in every scientific claim, people begin to look more closely and examine whether or not that claim is
01:15really justified.
01:18It's been an emotional rollercoaster for the team.
01:38The South Pole, nearly 10,000 feet above sea level, one of the coldest and remotest places on Earth.
01:48Here can be found Earth's clearest view of space for the telescopes operated by astronomer John Kovach.
01:58Well, welcome to the South Pole.
02:00Behind me in these crates are parts of our latest telescope.
02:03We're going to spend the next few weeks putting it together here at the South Pole.
02:07And then it's going to begin scanning the skies, looking at the oldest light in the universe.
02:13The signals that we hope it will be searching for, though, are from gravitational waves that come from a period
02:18even earlier in the first tiny fraction of a second of the universe's history.
02:28Gravitational waves were first predicted by Albert Einstein almost exactly a century ago.
02:34Distortions of space and time should propagate through the universe like waves in the ocean.
02:43A gravitational wave is really just what it sounds like. It's a wave of gravity.
02:48A ripple in space-time.
02:52Gravitational waves can arise whenever you have a rapid acceleration of mass in the universe.
02:57So a classic example is colliding black holes spiraling around each other.
03:04If a gravitational wave much, much larger than anyone we could ever possibly imagine were to pass right through this
03:10room,
03:10it would look like the room would get squashed and then expanded.
03:13It would pull everything apart, squeeze it all together, pull it apart again with a certain pattern.
03:18So it would distort the space-time in the room.
03:24Theoretically, gravitational waves should be produced on a regular basis by any massive disturbance,
03:31such as colliding black holes or exploding stars.
03:35LIGO is an experiment that uses lasers in an attempt to detect these recently produced gravity waves.
03:42But the gravitational waves that John Kovach and his team hoped to find have a much more ancient origin.
03:50The gravitational waves that we're searching for come from the very first moments after the Big Bang.
03:58The first tiny, tiny fraction of a second after the beginning.
04:020.0000 with 34 zeros and a one second.
04:07The very first instance of time.
04:15Every year, John Kovach and the team travel here to the Amundsen-Scott South Pole Station,
04:20where their telescopes are based.
04:23It is one of the three permanent US research stations in Antarctica.
04:29And to get here requires a ski-equipped LC-130 aircraft.
04:36The air temperature is about minus 30 centigrade in the summertime.
04:40You step out of the aircraft and the cold hits you like a slap in the face.
04:47You actually have to breathe very carefully to avoid burning your lungs.
04:52The South Pole Station can accommodate up to 150 people.
04:56This is where the BICEP team stays when carrying out work on their telescopes.
05:03So there is a big science station with a cafeteria, with all the rooms,
05:09and a basketball court, and a greenhouse.
05:14And then about a mile from there is where our experiments are.
05:33The team uses two telescopes to search for gravitational waves, the Keck Array and BICEP.
05:43The South Pole is a great place for us to put our microwave telescopes,
05:46because here at South Pole the air is the coldest on Earth.
05:50It's incredibly dry.
05:51There's very little that gets in the way of our microwave telescope's observations.
05:54It's almost like the telescopes being in space.
05:57That's really important because the telescopes are searching for exceedingly faint signals.
06:03Signals that might arise from gravitational waves in the early universe.
06:13Doing astronomy at the bottom of the Earth brings its own unique challenges.
06:20The team works on their telescopes during the few months of the Antarctic summer.
06:28But it is in the Antarctic winter when most of the observations are done.
06:33The South Pole station is only accessible for about three months out of each year.
06:40Temperatures are only warm enough to fly planes in and out for that period of time.
06:44So when we take one of these telescopes, like BICEP-1 or BICEP-2 to the South Pole,
06:48we come in with a team and we work furiously for three months to try to get everything to work,
06:54to put it all together, to calibrate it, to tune it up to get it in pristine condition.
06:59And then all of us get on an airplane and leave, except for one guy.
07:03He watches the plane go and knows there isn't going to be another one for about nine months.
07:14Engineer Stefan Richter was the one guy left to operate the BICEP-2 telescope
07:18over three Antarctic winters when the sun doesn't rise for six months.
07:25Back in those days we had to top up the telescope with liquid helium every three days.
07:30And that had to happen no matter what the weather was.
07:35Temperature can range anywhere from minus 40 to minus 73 centigrade,
07:40which is close to minus 100 Fahrenheit.
07:45There's a daily walk out to the telescope just to go to work.
07:50There's no traffic. There's beautiful stars out there and there's aurora almost every day in the winter.
07:59I personally think it's one of the most beautiful commutes in the world.
08:07It's akin to being in space.
08:11You get an amazingly unique experience when you spend a winter at South Pole.
08:23When the team first started hunting for gravitational waves,
08:26the prospect for success seemed remote.
08:32It's kind of a brave thing to devote years of your life to going after the signal that may or
08:37may not be there.
08:38A colleague of mine called this a wild goose chase.
08:42A wild goose chase.
08:43A wild goose chase. It was described in those terms by Andrew Lang, my mentor at Caltech.
08:49He liked to say, you know, it's better to fail at something important than to succeed at something unimportant.
08:57So I think it's with this mindset that we collectively started doing that back in 2003.
09:06When John Kovach and his team embarked on their epic challenge,
09:10there was not a single observation from any telescope in the world indicating that gravitational waves actually exist.
09:17What there was, was one man and his theory.
09:22The theory that started this entire wild goose chase.
09:41Okay, I think we get started now. Good morning, everybody.
09:44This is the man who inspires his colleagues to spend their lives on a scientific goose chase.
09:52Professor Alan Guth.
09:53He's one of the world's most eminent cosmologists.
09:57Back in the 1970s, when Alan was at the beginning of his career,
10:01he grew frustrated with what was known as the Big Bang model.
10:10This is the idea that the entire observable universe emerged from a tiny, hot, dense region of space,
10:17and has been expanding and cooling ever since.
10:22The conventional Big Bang theory described how the universe expanded, how it cooled, how the matter coagulated to form galaxies
10:30and structures.
10:31Oddly though, in spite of its name, it really said nothing about the bang itself.
10:36I like to say that it didn't tell us what banged, why it banged, or what happened before it banged.
10:49In December 1979, Alan came up with a revolutionary new idea for what happened in the first fractions of a
10:56second after the Big Bang.
11:02He named his theory the theory of inflation, and it was to have a profound effect on cosmology.
11:11These actually are copies of the notebook pages that I wrote in the night that I came up with the
11:16idea that has become inflation.
11:18I went home one night to my rented house in Menlo Park, California, and wrote down the basic equations,
11:25and I became very excited about it, and I even made a comment here with a double box around it,
11:31which is not the sort of thing I do very often.
11:34Spectacular realization, doubly boxed.
11:37I had only been working on cosmology for about a year or so at this time,
11:41so I was very worried that when I started showing it to other people,
11:44somebody would point out something that was obviously wrong about it.
11:48But I was excited nonetheless, and the next day I started telling my friends about it.
11:57The equations that Alan had written down that night in 1979 were just the beginning.
12:03Within a few months, Alan went on a tour of universities around America,
12:07giving a series of talks to promote his bold new idea of inflation.
12:14I first heard about inflationary theory in spring of 1980 when Alan Guth came by to give a talk at
12:22Harvard University,
12:23introducing this new idea of the inflationary universe.
12:30Alan embarked on a tour of American universities, ripping up conventional ideas about how the universe began and pushing further
12:38back in time than anyone had dared to do before.
12:43The title talk that I was using at that time was 10 to the minus 35 seconds after the Big
12:48Bang.
12:49This was one of the most exciting talks I have ever heard.
13:01Alan was trying to correct a number of flaws in the original hot Big Bang model.
13:09Alan's theory neatly explained the first few moments of the universe by adding a new twist called inflation.
13:18Inflation caused the universe to expand astonishingly fast before suddenly slowing down.
13:30Inflation is basically a theory, I like to say, of the bang of the Big Bang.
13:34It's a theory that describes what propelled the universe into this period of gigantic expansion that we call the Big
13:41Bang.
13:42A plausible number, for example, for the starting time of inflation might be something like 10 to the minus 37
13:50seconds after the instant of creation.
13:54So it's something like a trillionth, trillionth, trillionth of a second after the Big Bang.
13:58An incredibly short length of time. It took me a long time to convince myself that it made any sense
14:02to talk about these things.
14:03Once it starts, the universe would double in size over and over again, every trillionth, trillionth, trillionth of a second.
14:10A typical size for the universe at the beginning.
14:17Something like 10 to the minus 24 centimeters across.
14:21Decimal point, 23 zeros, 1 centimeters.
14:26Unbelievably small. This is more than a billion times smaller than the size of a single proton.
14:31By the end of the inflationary period, the final size of the universe will be something on the order of
14:39maybe one centimeter.
14:41It's still small at that point, but this is still the early universe.
14:44From then on, it goes from the one centimeter stage to the universe we observe today.
14:51With his new inflation theory, Alan had fundamentally rewritten how the universe was born.
14:58The theory of inflation is a little bit crazy, but it really does a very natural, nice job at explaining
15:05some of the most puzzling features of our universe.
15:10Alan showed in his lecture how inflation, this incredible burst of expansion after the Big Bang, could very neatly explain
15:19some of the great unsolved mysteries of the universe.
15:24Why is the universe so large, with a geometry that appears to be almost perfectly flat?
15:30And why, at the largest scale, is the universe so incredibly uniform in all directions?
15:38It was a triumph of science.
15:47But the idea of inflation has not been universally accepted.
15:51One thing above all would put the theory beyond question.
15:55The discovery of its greatest prediction.
15:59Gravitational waves from the beginning of time.
16:14Alan Guth believes the universe started with a bang.
16:17A massive, instantaneous explosion, big enough to leave waves of space and time that still ripple today.
16:25He predicted the existence of gravitational waves, but no one has actually observed them.
16:32Before we just accept this is what happened, it's really, really, really critical that we see the experimental evidence.
16:41That's why we have to go out with our experiments and actually measure something that tells us whether inflation is
16:46correct or is just the wrong theory.
17:00A detection of gravitational waves is often described as the smoking gun signature of inflation.
17:05It proves that inflation really is responsible for kicking off the start of our universe.
17:12If gravitational waves are detected, that provides very strong evidence to this whole story of inflation.
17:25The theory of inflation actually predicts that there will be gravitational waves.
17:29But it doesn't tell you how much, how big they'll be.
17:34It just says that, you know, they'll exist.
17:38The gravitational waves which we can potentially observe right now, they were produced approximately one trillionth of a trillionth of
17:45a trillionth of a second after the Big Bang.
17:50So when people talk about gravitational waves from the Big Bang, you might be tempted to think that this is
17:56some huge shock wave propagating through the universe.
17:58This isn't true at all.
18:01The secret to gravitational waves from inflation is really quantum mechanics.
18:06It's simply the fact that on very small wavelengths, quantum theory tells us that everything fluctuates, including the gravitational field.
18:18Quantum mechanics says you can't pin down a physical system to something that is an absolutely precisely defined state.
18:25There will always be some uncertainty. There will always be some quantum mechanical jiggle in the universe.
18:31So what that means is the gravitational field during inflation is not precisely smooth. It has these little jiggles.
18:40What inflation does is it stretches out these very small fluctuations to make the wavelengths large enough that they can
18:47be observed in the early universe.
18:53And if inflation really did produce these gravitational waves, they might still be detectable with telescopes.
19:02So the way we are searching for this gravitational wave signal is to study the microwave background.
19:08It's the oldest light in the universe, and it's a treasure trove of information, but it really gives us a
19:13snapshot of the universe as it looked 300,000 years or so after the Big Bang.
19:21The cosmic microwave background is essentially the afterglow of the Big Bang.
19:28Released as the universe cooled down, this light, now incredibly faint, still fills the entire universe.
19:38Gravitational waves would have affected the orientation of these light waves, what's called polarization.
19:48So the cosmic microwave background has a polarization, and polarization is kind of like a directional thing.
19:55So think of a pattern of little headless arrows over the sky.
19:59Gravitational waves stretching and compressing would leave an effect on the polarization of the cosmic microwave background.
20:06It would produce a particular swirling pattern in that polarization that we call a B-mode polarization.
20:18It's kind of a pinwheel pattern of polarization, or a twisty pattern.
20:25A curly pattern on the sky.
20:31It's the unique signature of gravitational waves.
20:38Gravitational waves stretching and compressing space would have left this pattern imprinted in the cosmic microwave background,
20:46the afterglow of the Big Bang.
20:49If that B-mode signature is there, it is an incredibly powerful messenger coming to us from the first tiny
20:57fractions of a second of the universe's history.
21:02The hunt for gravitational waves from inflation had become a hunt for this B-mode.
21:12If inflation theory was correct, then this B-mode was out there, waiting to be found.
21:21So behind me you see one of our telescopes.
21:24It's actually a very simple design.
21:26It consists of a number of small two-lens refracting telescopes,
21:30each of which has an entrance aperture of only about this big, 30 centimeters.
21:35It's scanning back and forth on a relatively small patch of sky, relentlessly collecting microwave photons.
21:41And it needs to do that because the B-mode polarization signals that it's looking for are exceedingly faint.
21:58The team's first telescope, BICEP-1, saw first light in the Antarctic summer, January of 2006.
22:08But after three years of steady observation, there was little to show for it.
22:16No glimpse yet of any B-modes.
22:19The wild goose chase may have been just that.
22:33The BICEP scientists' first attempt at finding gravitational waves was a failure, but not a dead end.
22:39The next step? Build a bigger telescope.
22:46In November 2009, John and the team were back at the South Pole to install a new telescope, BICEP-2.
22:59Even before the three-year observation of BICEP-1 ends, we already knew we want something more sensitive.
23:06In BICEP-1, we had nearly 50 detector pairs.
23:12In BICEP-2, we had about 250.
23:15And H1 is slightly more sensitive than BICEP-1.
23:19So in the end, we get almost a factor of 10 improvement in sensitivity.
23:24So this is the detector technology in BICEP-2.
23:29And what you see here is effectively a printed camera.
23:34Each of these pixels is basically a camera in the sense that it's not just the detector,
23:39it's actually the lens and the filter as well.
23:55Like its predecessor, the BICEP-2 telescope was in operation across three Antarctic winters,
24:01continuing the hunt for gravitational waves.
24:07It was a quantum leap in sensitivity.
24:09We were able to map the sky 10 times faster with BICEP-2 than we could with BICEP-1,
24:16and achieve much more sensitive maps of the polarization in the same patch of sky that we had observed before,
24:22but much deeper now.
24:27We analyzed the data as it came in through 2010 and through 2011, the first two seasons of operation.
24:34But we quickly ran into a problem.
24:36We did all these tests with BICEP-2, and we couldn't get rid of this signal.
24:44The BICEP-2 telescope had picked up a signal,
24:47and it displayed all the characteristics of gravitational waves.
24:53It had the distinctive swirling pattern, the B-mode, that John and the team had been looking for.
25:00Yet it was less faint than they'd been expecting.
25:05Something did not seem quite right.
25:08It was at a much higher level than we were expecting,
25:11either from emission from our own galaxy,
25:15or really from what we thought were favored models of inflationary gravitational waves.
25:24It was higher than either of those, and so we thought,
25:28oh, well, the signal can't be real, it must be a problem with our instrument.
25:31There must be some kind of subtle effect that we haven't yet controlled in the experiment that's producing a false
25:37B-mode signal.
25:40Yet tests confirmed that there was nothing wrong with the telescope.
25:45The signal that had been detected was real.
25:48It was coming from the sky.
25:53Once you've established that there's a signal, then the next question is, what is the signal?
26:04You can't just assume right off the bat that you're looking at the signature of primordial gravitational waves.
26:09It would be nice if you could, but unfortunately, although most of space is remarkably empty,
26:15and therefore we can make a lot of measurements of the microwave background,
26:18we live in a galaxy, and within our own galaxy there are a number of sources that can create a
26:24polarization that have B-mode patterns.
26:27So the two ones that we worry about the most are something called synchrotron radiation and something called dust emission.
26:36Synchrotron radiation is a type of light that is produced in the galaxy when its magnetic field sends tiny electrically
26:43charged particles whizzing around very fast in spirals.
26:47This can mimic the B-mode pattern of gravitational waves.
26:51But using data from a satellite, the BICEP team was able to show that this effect was too small to
26:57produce the signal that they had detected.
27:00Synchrotron radiation was ruled out.
27:04The other big potential contaminant is dust, and this dust isn't so different from the dust in your living room
27:10that you see when the sun pours through the windows.
27:14It's made up of carbon and silicates, just like little rock, bits of rock, coated in water ice.
27:21And these little dust grains can line up in the magnetic fields, and then when light shines through them, they
27:27can create a little bit of polarization.
27:32Dust was harder for the team to discount.
27:35There was less data available, but the models that did exist suggested that dust wouldn't produce such a large signal.
27:42Dust was also ruled out.
27:47Once you're really convinced that you're seeing signal that comes from the early universe, then you can say you've detected
27:53primordial gravitational waves.
27:58And the team now felt that this was the most likely conclusion.
28:03After four years of analysis, everything pointed to the signal coming from gravitational waves.
28:10So as the final tests of the BICEP-2 dataset were completed by our analysis team, we called a collaboration
28:16-wide meeting, and about half of us were calling in from the South Pole, and half of us from locations
28:21around North America.
28:23We had looked at the data set in every way that we knew how to scrutinize it from every different
28:29angle, and convinced ourselves that there were no other tests that we could perform.
28:34We were feeling at that stage that it was our obligation to share our results with the community.
28:40In fact, that it was overdue that we do so, because we had had that data for so long at
28:50that point.
28:55The team members had kept their discovery under wraps, but now, finally, they felt compelled to go public with their
29:02news.
29:04We knew that it was time to show the B-Mode map that BICEP-2 had made to the world
29:10and not keep it a secret any longer.
29:12But first, there was a very special person they needed to tell.
29:32In December 2013, John Kovach returned from the South Pole.
29:40As the team prepared to announce their discovery of gravitational waves, there was one man above all with whom John
29:47wanted to share the news.
29:49The man whose theory had predicted the existence of these space-time ripples from the early universe.
29:57John initially sent me an email saying that he would like to talk to me urgently about an issue that's
30:04very important to your research and mine.
30:07In quotation marks.
30:10A meeting was hastily arranged at MIT in Boston.
30:14I got in a taxi cab and drove over here on the evening of Monday, March 10th of this year,
30:222014.
30:24Walked down the corridor behind me and carried the drafts of the paper that we had been preparing.
30:29We arranged for him to come through the back door of the Center for Theoretical Physics,
30:33so he would be unlikely to be noticed by the other people in the Center.
30:37I was greeted by Alan very cordially, very calmly.
30:41In fact, we both sat down and he knew immediately what this would be about.
30:48This was the news that Alan had been waiting for more than 30 years to hear.
30:53Definitive proof that his inflation theory was right.
30:57Well, he told me that his group had been looking for years to examine the possibility of gravitational radiation from
31:06the early universe.
31:07He told me that he was initially skeptical that it could be found.
31:11He told me that once they had a signal, he was very anxious to make sure that the signal passed
31:17all possible tests to be sure that it was real.
31:21And that gradually, he and the rest of the group became convinced that the signal was real and that now
31:28they were ready to make a public announcement about that.
31:32John's team had potentially made a Nobel Prize winning discovery.
31:42I think we were both very excited.
31:44My reaction at the time was amazement.
31:47I was astounded to suddenly have a group come forward and say that they had a measurement with unbelievably high
31:54statistical significance.
31:55Really was a shock to me and, of course, a very pleasant shock because it would be very strong evidence
32:01for inflation if it was real.
32:06It happened in less than a trillionth of a second after the Big Bang.
32:11Attention, vertige.
32:13Dans notre page science consacrée au Big Bang, des Américains auraient retrouvé la trace de la secousse qui créa.
32:19They've detected gravitational waves or ripples in what they believe is the oldest light in the sky.
32:28On March 17, 2014, the team announced their discovery at a Harvard press conference.
32:36So when we announced BICEP-2's B-mode findings, we knew that that would generate some news.
32:42But we were not expecting anything like the attention that the release got or the excitement that it produced.
32:50Honestly, I expected the reaction to be fairly quiet.
32:55The four years specifically working with this data.
32:58The title of detection of B-mode polarization in cosmic microwave background.
33:02With that title, you wouldn't think it would generate much interest, but it did.
33:06So times change very rapidly.
33:09And then we surround the telescope.
33:10It was emitted 380,000.
33:11I first got wind of the BICEP-2 signal about a week beforehand.
33:16The BICEP-2 announcement was incredibly exciting.
33:20This would be one of the final confirmations, not only of inflationary theory, but also the general theory of relativity.
33:31Appearances aren't always what they seem.
33:36So after the initial announcement and the news, I think most people in the community, in the broader cosmology and
33:43physics community, accepted it as face value.
33:48But as happens in every kind of claim discovery or scientific claim, then people begin to look more closely and
33:56examine whether or not that claim is really justified.
33:59So since the March announcement of the BICEP-2 detection of gravitational waves, there's been a flurry of activity trying
34:06to determine whether or not the source of the detected B-modes is actually the gravitational waves from the early
34:13universe.
34:13Or if it could be something more mundane, like in particular, people are wondering if it could be dust in
34:20our own galaxy.
34:25The possibility that dust in the Milky Way might produce a B-mode signal had been considered by John and
34:32the BICEP team.
34:33They had chosen a patch of sky known as the Southern Hole precisely because it was relatively clear of galactic
34:40dust.
34:42Yet the team's work came under increasing scrutiny.
34:47When we had NASA's result, the most important fact for us was that it was real.
34:52It wasn't produced by the instrument.
34:54And that was the hard part, as far as we were concerned.
34:57That's what we had spent the last 14 years doing.
35:00At that time, based on the information that was available, whose uncertainties were rather hard to quantify, it looked very
35:07much like a large fraction, you know, 90% of the signal was gravitational waves.
35:23The uncertainty over the real identity of the BICEP2 signal was to grow, as in Europe, a separate team of
35:30scientists began to release new data about galactic dust.
35:37The world's best data on polarized dust is available from the Planck satellite.
35:46So, what they knew about dust emission in our particular field in March, you would have to ask them.
35:57Yes, but we had already sufficient information to be quite sure that the optimistic modeling of BICEP was not proper.
36:10The Planck satellite was a state-of-the-art telescope that for several years had been surveying the skies from
36:17its vantage point in space.
36:21Its principal mission had been to make the most detailed map ever of the cosmic microwave background, the afterglow of
36:28the Big Bang.
36:33To accomplish that task, Planck had also carried out the best measurements ever made of galactic dust.
36:41The new data from Planck revised the older models of dust, the models the BICEP team had relied on.
36:47Galactic dust is brighter than anyone had expected.
36:53Planck's new measurements bring the entire discovery of gravitational waves into question.
37:09The discovery of gravitational waves arrived with much fanfare.
37:13But within months, this great scientific breakthrough was being second-guessed.
37:19The Planck space telescope had gathered new data that the BICEP astronomers desperately needed.
37:26There was a great confluence of interest from the Planck team and from our own team.
37:34A realization that there was a critical and exciting scientific question at stake here.
37:39And the best way to answer it was to use all of the best data in the world all together
37:44in one analysis.
37:46So, in essence, we set up a memory and an understanding between the two teams and went on with it.
37:58In July 2014, the two teams began sharing their data, using the measurements of galactic dust emission from the Planck
38:07satellite to find out where in the universe the BICEP2 signal might have come from.
38:18Let's make an analogy. I'm listening to some headphones.
38:23Imagine that there are two tunes that are playing.
38:26And I'm trying to hear one tune, which is the gravitational wave signal that we're after.
38:33But there's also another tune that's playing that's potentially a bit louder, right? And that's the galactic dust emission.
38:42And by using the data from Planck, the higher frequency data from Planck, we can actually essentially make that distracting
38:49tune quieter.
38:50And improve our ability to listen for that gravitational wave signal.
39:00You know, we're at a fork in the road.
39:03If this is positive, this is just amazing. I mean, you know, it means that, well, we have discovered primordial
39:09gravitational waves and we have actually discovered them jointly.
39:12On the other hand, if it was a false hope, well, let's know it.
39:20On January 30th, 2015, the two teams released the results of the joint analysis.
39:27Where BICEP has done is a tour de force.
39:31It's a magnificent measurement, a little bit tantalizing, exciting.
39:38But we confirm that this is not a discovery.
39:48So the results of the joint analysis of BICEP2 with Planck is that the most likely answer is that 75
39:57% of the signal that we're seeing is due to galactic dust.
40:02But, and this is a very important but, there's a big uncertainty on that 75%, right?
40:07That uncertainty spans the range of half to 100%, right?
40:12I have a piece of coal and I'm not able to tell you how much gold is in there.
40:19Did I detect something?
40:22Do you think you are rich?
40:26You just don't know.
40:28The BICEP team had no choice but to withdraw their claim to have discovered gravitational waves.
40:35So, at this point in time, the proper scientific statement is that there's no evidence of gravitational wave.
40:42B-modes and that if they exist, they're less than about half of the signal that we're seeing.
40:53It's a disappointing result for the BICEP team.
40:58That's the cruel reality of being an experimentalist.
41:01And that's the point of it.
41:02The last nine months has been absolutely an emotional roller coaster for the team.
41:12And, you know, really quite difficult in many ways.
41:16Because we're not used to being in the spotlight in this way.
41:19And so, it's difficult for us scientists to know exactly how to react.
41:24We did underestimate the level of dust polarization in our original announcement.
41:29There's no denying in that.
41:31But that's because of the lack of data, not because we did anything wrong.
41:39One of the greatest discoveries of the century had eluded the BICEP team.
41:43For now, gravitational waves have escaped detection.
41:50The path ahead is very clear.
41:53We have telescopes that are operating right now that are producing more and more powerful data.
41:59Next in the series of telescopes is going to be BICEP-3.
42:03And that's going to be another jump again in sensitivity.
42:06And push further and further the knowledge that we have about what the sky tells us about the first fractions
42:13of a second of the history of our universe.
42:16And the BICEP team are not alone.
42:21Around the world, many scientists have also embarked on the hunt for gravitational waves.
42:28From the Atacama Desert of Northern Chile, to the wilderness of Antarctica.
42:36The quest to confirm how the universe was born, to find the wild goose of inflation, continues.
42:44It's a process that we all, as scientists, are absolutely committed to.
42:50Getting to the truth, wherever it leads us.
42:59As far as I'm concerned, inflation is still in very strong shape.
43:04But whether or not gravitational waves will be added to our list of pieces of evidence for inflation, I don't
43:10really know at this point.
43:12We are in beautiful...
43:28And we're in beautiful...
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