Did Scientists Just Find the Harmony of the Universe? | Unveiled - video Dailymotion

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00:00 For many years, cosmologists have been on the hunt for the gravitational wave background,

00:05 a hidden symphony of ripples in space left behind by the Big Bang.

00:10 While we've detected gravitational waves several times, detection of this gravitational

00:14 wave background is a new and historic milestone.

00:18 This is Unveiled, and today we're answering the extraordinary question; did scientists

00:22 just find the harmony of the universe?

00:26 Do you need the big questions answered?

00:28 Are you constantly curious?

00:30 Then why not subscribe to Unveiled for more clips like this one?

00:33 And ring the bell for more thought-provoking content!

00:37 In June 2023, cosmologists announced that they had detected the faint signals of a gravitational

00:43 wave background, a feat never before accomplished.

00:46 This gentle echo of ripples in space-time has long been theorised by physicists, but

00:51 only detected for the first time this year.

00:53 This is a major moment in cosmology, but what exactly is this wave background, and why is

00:58 this discovery so significant?

01:00 To find out, we first need to travel more than a century back in time, to the life's

01:05 work of one of history's most celebrated minds.

01:08 Published in 1915, Einstein's General Theory of Relativity provided a revolutionary description

01:14 of gravity.

01:16 And then, based on this theory, he went on to predict the existence of gravitational

01:20 waves - ripples in space-time - although at times he also rejected the idea.

01:26 Here is where this particular field in physics really starts to open up.

01:30 Although, surprisingly, some pre-Einstein scientists had already proposed the existence

01:35 of these waves.

01:36 Originally, the concept was derived from the laws of electromagnetism.

01:40 In the 1860s, James Clerk Maxwell formulated equations that formed the foundation of classical

01:47 electromagnetism.

01:48 He unified electricity and magnetism, discovering that they were two sides of the same phenomenon,

01:54 and that they travelled through space as waves at the speed of light.

01:59 Maxwell's discovery had serious implications across physics, and Maxwell himself pondered

02:04 whether we can similarly describe gravity via fields.

02:07 Next, and the first to follow up on this, was an electrical engineer named Oliver Heaviside.

02:13 In his 1893 paper, "A Gravitational and Electromagnetic Analogy", Heaviside directly

02:19 compared gravitational and electromagnetic fields, wondering whether gravitational fields

02:25 similarly propagate at the speed of light.

02:27 If so, the movements of attracting bodies would result in disturbances in the gravitational

02:32 field, travelling at a fixed velocity.

02:35 More than twenty years prior to Einstein, then, science had already pushed itself to

02:40 the edge of this major discovery.

02:42 In hindsight, this research is truly astounding… but then the repercussions of it really came

02:47 into view.

02:48 Einstein's theory of special relativity was published in 1905.

02:52 Special relativity posited that the speed of light in a vacuum is the same, regardless

02:56 of the motion of the light source or an observer.

02:59 In short, this means that nothing, not even gravity, can move beyond the speed of light.

03:05 While Einstein was working on special relativity, however, the French polymath Henri Poincaré

03:10 developed a lot of similar mathematics independent of Einstein.

03:14 And in his 1905 paper, "On the Dynamics of the Electron", he pondered the laws of

03:19 gravitation.

03:20 Poincaré again tried to understand gravity using the principles of electromagnetic fields,

03:25 and assumed that gravity propagates at the speed of light.

03:28 The result of this is a time delay between gravitational changes and their effect.

03:33 Poincaré's major point was that these changes are propagated by gravitational waves.

03:38 Unfortunately, he did not expand on their nature, but was amazingly correct in this

03:43 assumption.

03:44 A decade later, Einstein published his famous paper on "general relativity".

03:48 This described gravity as a geometric property of spacetime, but didn't mention any sort

03:53 of cosmic vibrations.

03:54 We're getting closer, but not quite there.

03:57 And in fact, in 1916, Einstein reportedly wrote in a letter to the German physicist

04:03 Karl Schwarzschild that "there are no gravitational waves analogous to light waves".

04:09 Two years later, Einstein published a follow-up paper on the topic.

04:13 In the paper, he shows a change of heart toward the idea, and subsequently incorporated the

04:17 concept of gravitational waves into his theory.

04:21 And broadly, how Einstein explained them is still how we think of these waves today; as

04:26 infinitesimally small distortions in spacetime which transport energy as gravitational radiation.

04:33 Today, this breakthrough is still remembered as an incredibly impressive feat, especially

04:37 since he had no way of observing this phenomenon.

04:41 Disappointingly, though, after a few decades, an older Einstein began to reject gravitational

04:47 waves.

04:48 Indeed, he changed his mind on them throughout his life.

04:51 As it turned out, this was due to an error in his calculations, which was spotted and

04:55 fixed by the American mathematician and physicist Howard P. Robertson.

04:59 The confusion had created a temporary stigma around the topic, though, and there was something

05:04 of a dark period in its research.

05:06 Thankfully, technology has now come a long way since Einstein's day, and we now know

05:11 that the waves are there, even if they are exceedingly tough to detect, requiring extremely

05:16 sensitive equipment.

05:18 In the twenty-first century, gravitational wave astronomy has certainly started to flourish.

05:23 In 2015, the first ever successful observation of a gravitational wave was made, achieved

05:29 thanks to the Laser Interferometer Gravitational Wave Observatory, or LIGO.

05:34 Back then, what the researchers detected was a gravitational signal emitted from the merging

05:38 of two black holes.

05:40 Interestingly, this was also the first black hole merging period ever observed.

05:45 In the context of gravitational waves, however, the intensity of the event created gravitational

05:50 radiation with more energy than all of the observable stars in the universe emitted as

05:55 light in the same time frame.

05:58 And finally, this detection was the crucial first step in finding the aforementioned gravitational

06:03 wave background.

06:05 Also called the stochastic background, the gravitational wave background is a relic of

06:09 the gravitational radiation left behind from the very early years of our universe.

06:14 This creates something of a hum, permeating throughout the entire cosmos, caused by various

06:20 events.

06:21 One such event is, of course, the Big Bang itself, which is likely to have produced the

06:25 majority of the hum.

06:27 These waves would have likely been made in the universe's first seconds, and will have

06:31 since stretched with the cosmos' expansion.

06:33 They've simply always been here.

06:36 Theoretically, the stochastic background should be a continuous noise which is ubiquitous

06:41 and homogenous across all of nature.

06:44 And that's why the quest to find it has gotten so many excited.

06:48 Researchers believe that studying these universal cosmic ripples could give us insight into

06:52 the very earliest moments of the universe.

06:55 We could learn about mind-blowingly ancient processes that are inaccessible via all other

07:00 methods.

07:01 The good news?

07:02 In 2023, we successfully detected what has been referred to as the universe's cosmic

07:08 harmony.

07:09 It was announced in June by the North American Nanohertz Observatory for Gravitational Waves,

07:15 an international consortium of astronomers who drew on observations from radio telescopes

07:20 around the world.

07:22 They were able to reach their results by analysing approximately fifteen years of pulsar data.

07:27 A pulsar is an extremely magnetised, rotating neutron star that emits intense beams of electromagnetic

07:34 radiation from its poles.

07:35 They're created in supernova explosions of massive stars, but we can measure them when

07:41 they just so happen to point towards Earth.

07:43 This allows us to calculate their rotational periods, which can be amazingly short, ranging

07:48 from milliseconds up to around eight seconds.

07:52 Fifteen years of data on sixty-seven pulsars was compiled and used in the study.

07:56 The underlying principle was to treat the pulsars as reference clocks that send out

08:01 regular signals monitored on Earth.

08:03 Theoretically, if a gravitational wave were to pass through our line of sight to the pulsar,

08:08 the local fabric of spacetime would be perturbed, altering the observed pulsar rotational frequency.

08:15 Even though pulsar-emitted electromagnetic radiation spends hundreds to thousands of

08:19 years travelling through space, the detectors we have on Earth are able to measure perturbations

08:25 of less than a millionth of a second.

08:27 Back in 1983, astrophysicists Richard Hellings and Alan Downes produced a prediction for

08:33 what these waves might look like, in a model called the Hellings and Downes Curve.

08:38 That fifteen-year dataset then provided clear evidence of an isotropic background of gravitational

08:44 radiation, and gave the first real-life measurement of the Hellings and Downes Curve.

08:50 Currently, the specific sources of this background is undetermined and requires further research.

08:55 Observatories hope to someday observe the gravitational rhythm of the first trillionth

09:00 of a second of the universe's existence.

09:03 This would allow cosmologists to witness, in a way, the birth of our universe, almost

09:08 fourteen billion years later.

09:10 While it's been over a century since Einstein's great prediction of these ripples in the cosmos,

09:15 we're only just beginning to see the tip of the gravitational wave iceberg.

09:20 For now, the future is bright for the field, and we can expect this research to continue

09:25 to answer the mysteries of the origins of the universe.

09:28 So watch this space.

09:30 What do you think?

09:31 Is there anything we missed?

09:33 Let us know in the comments, check out these other clips from Unveiled, and make sure you

09:37 subscribe and ring the bell for our latest content.

Did Scientists Just Find the Harmony of the Universe? | Unveiled

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