What Are The Hidden Rules Of The Universe?

This video has been kindly supported by Wondrium. Imagine a glorious future where humans have overcome our present troubles, And we eventually leave this tiny planet behind to live amongst the stars, In time, our descendants span the entire Milky Way, Countless trillions living in harmony from the galactic centre to the most distant spiral arm. One day, a message arrives from outside, from another distant galaxy, another distant cluster. There is other life, other intelligence, out there in the

universe. Ideas are exchanged and science, art and philosophy prosper. And eventually, plans are made - in the darkness of intergalactic space, the two great civilizations will meet. Many generations labour to build the immense craft capable of traversing great distances. And many generations are born, live their lives and die on the immense journey. But after countless millennia, in the inky blackness, the emissaries of the two civilizations approach. Two individuals float across the void, hand

s reaching out. They touch. And both vanish in a blinding flash. The great ships stand off from each other, staring in amazement. The civilizations are fundamentally different. And it is only now it becomes clear - one is made of matter, the other anti-matter, and any contact leads to annihilation. The ships retreat into the darkness, knowing that true contact will always be impossible. But how did it come to this? How did they not know about the difference in their fundamental make-up? They had

shared their science, their mathematics, and their engineering Surely this difference would have been obvious? But the scientists knew better, they knew that nature holds onto its secrets tightly. They knew that written into the laws of the universe were rules that cloaked these secrets. Rules fundamental to the functioning of the universe. They knew that these rules were built into many of the universe´s processes, from the supermassive to the microscopic. They knew that it was these rules tha

t had helped reality freeze in the first billionth of a second of time. And behind them all - they knew there was always one common factor. Symmetry. Have you ever wondered how your brain works? Or how the earth formed? Or how civilisation began? Wondrium is the perfect place for you, and has been a huge inspiration to both History of the Universe and History of the Earth. Wondrium used to be called Great Courses Plus, which made university level lecture series - and they have now expanded to co

ntain even more content. From travelogues and tutorials to long form documentaries, Wondrium is the best place for all your high quality, enjoyable content that will make you smarter. One great example of this is The Theory of Everything series by Don Lincoln - an easy to understand university level lecture series, and one I like to listen to to get inspiration for the channel. Indeed the two lectures on how symmetry works in physics were a huge help in making this video. Its exhaustive, totally

understandable but never dumbed down. I am not exaggerating when i say that without Wondrium this channel may not have existed. It is the best educational subscription service out there, hands down. And they’re giving viewers a great offer of a FREE trial! So, get the fantastic education I did by heading over to wondrium.com/historyoftheuniverse. Thanks to Wondrium for supporting education on Youtube and sponsoring this video. Two great civilizations Inhabiting two distinct and distant regions

of the universe, And yet we know their laws of physics must have been the same. Then how could they have failed to tell matter from anti-matter? Two particles, two atoms, two intergalactic beings with opposite electric charge? In our patch of the universe, matter is everywhere, and anti-matter is rare. But in their patch of the universe, the inverse must have been true. Whilst we live by the light of a star, they lived by the light of anti-stars. Whilst our ships were built from atoms, theirs we

re constructed from anti-atoms. It would be understandable to think that the laws of physics do not care about the difference between matter and anti-matter. But that is not quite true. We now know that nature does treat matter and anti-matter slightly differently. Though these differences are subtle and unexpected, And they are related to one of the deepest concepts in all of physics. What is symmetry? We all know our first perception of symmetry, a mirror reflection from left to right. Armed w

ith such a mirror, a child can sketch a symmetrical shape, With what is on the left also seen on the right, and vice versa. But looking in a mirror reveals that this reflection runs deeply in nature. Our faces and bodies are symmetrical, a right eye with a left, a left arm with a right. Nature makes many uses of this mirror, or bilateral, symmetry. Most mammals, reptiles, birds, and fish share this simple mirroring. And when the rules of natural symmetry are broken, such as the oversized claw of

a Fiddler Crab, The appearance can be quite jarring. But symmetry is more than just reflection. A starfish builds itself using rotational symmetry, so when rotated its appearance does not change. and a millipede uses translational symmetry, constructing its body with identical chunks. Through symmetries, nature is being economical in design. Symmetry can also spark a deep emotional response. In human concepts of beauty, symmetry of appearance is pleasing, even though beauty is only skin deep, a

nd inside we can be quite asymmetrical. And this appreciation has made its way into art and design. The great temples of the ancients in Egypt and Greek show exquisite symmetry As do more modern buildings like the Taj Mahal and Arc de Triomphe and many great artworks, such as DaVinci’s Last Supper. And art and design call on more than just simple mirror symmetry, as rotational symmetry can be powerful. From the rotating disks of the pre-Columbian Americans, to the exquisite Islamic patterns ador

ning many mosques across the globe. And indeed the massive Pentagon, home of the US Department of Defence, bears its geometry in its name. Symmetry is everywhere. But you might be wondering how this relates to the fundamental rules of the universe? Well, our story starts, as all good stories do - with a duel. At dawn on the 30th May 1832, two men met in a field outside of Paris, The cause of the conflagration is unclear, but rumour goes it was over the affections of a young woman. By the time th

e sun was fully up that day, 20-year-old mathematician, Everiste Galois, lay dying in the grass. The night before Galois had had a premonition of his upcoming death. Into the early hours, he had scribbled, with letters to friends and colleagues, And amongst these missives, he had poured out the last of his mathematical ideas. For in his short life, Galois had brought many new ideas to the world of maths, and central to these was the idea of symmetry. The mathematics of symmetry was not a new ide

a. Ancient geometers had realised that a rotated circle remained the same circle. And triangles, squares and pentagons appeared the same after fixed rotations. But Galois saw deeper. His focus was algebra, and more specifically - polynomials. Polynomials are equations with quantities to a power, squares, cubes, and higher. For example “one plus x plus x squared” is a simple polynomial. As is three plus five times x to the power of five minus x to the power of seven. Such polynomials are found ac

ross all of science, engineering, economics, and many other fields. Other mathematicians had scrambled to try and find algebraic solutions to higher-order polynomials, But Galois wondered if such an equation existed for all polynomials - one equation to unlock them all. Yet instead of discovering this ultimate equation, he actually showed it was a fool’s errand - the solutions just didn’t exist. And he didn’t do this by simply fighting through the algebra, but by looking into the symmetries of t

he solutions. He realised the solutions to polynomial equations were complex numbers, each being a point on the infinite complex plane. These points could appear as shapes, triangles, pentagons or others. And shapes, of course, have symmetries – they can be reflected or rotated. This was a radical way of doing mathematics - translating equations into a geometric picture and thinking about their symmetries. And since his work in the early nineteenth century, mathematical insights into symmetries

have grown, It has blossomed into group theory, the study of groups of things that share properties and symmetries. Modern cryptology is underpinned by group theory, but it is symmetry´s impact on science which has been the most startling. And so as he lay dying in the morning light, Galois didn’t know that his scribbles would revolutionize our universe. Long before they met, our two great civilizations came into contact. Radio beams were fired across the universe, taking many millions of years

to reach their destination. It was a slow and cumbersome way of talking, But this new conversation with our distant neighbours did work. Both civilizations knew the laws of electromagnetism. On Earth, the jiggling of electrons formed the radio beam that carried the messages. And in the instruments of the aliens, charges jiggled as the messages arrived. But unlike on Earth, these were anti-electrons, positrons, dancing to the beat of the radio waves. Electromagnetism has a fundamental symmetry. I

f you swap all the positive and negative charges, the outcomes remain the same. The exchange of radio waves alone between the two civilizations could never tell matter from anti-matter. Something else was needed, some crack in the symmetry of physics. To understand why, we need to start our story almost a century ago. We need to start with a funeral. On the first of May in 1935, an obituary appeared in the New York Times, This was not unusual, but the author, famous physics professor Albert Eins

tein, certainly was. Emmy Noether, Einstein wrote, had been the “most significant creative [female] mathematical genius produced so far”, And her insights had been necessary for “the deeper penetration into the laws of nature”. But what did he mean? Emmy Noether was only fifty-three when cancer struck her. And whilst her name might not be as iconic today as Einstein and the other old fathers of physics, Her work was just as important - and Noether’s theorem has everything to do with symmetry. An

d key to this was one simple fact - the universe, nature itself - is lazy. With the coming of modern science, mathematics had steadily replaced mysticism, and geometric symmetries had emerged from the equations. The spherical pull of Newton’s gravity resulted in spherical planets and stars, Whilst the magnetic field of an electrical current was found to be shaped like a cylinder. These geometric symmetries, symmetries of shape, were pleasing to the eye, But they were really only skin-deep. There

were other, much deeper symmetries lurking in the mathematics of the universe. As with any story, there were many potential players, but here we will focus on just two. The first is Italian-born Giuseppe Lodovico Lagrangia, better known as Joseph-Louis Lagrange. And Irish mathematician William Rowan Hamilton. They share few similarities in their lives - Lagrangia lived through the French revolution and was instrumental in bringing in the metric system - Hamilton grew up as a wonderkid in Dublin

almost a century later. But despite their separation in time, their work dovetailed on one key thing - reformulating the equations of Newton. And key to their insight was the idea that the universe was lazy - the curious concept of "least action". Indeed, long before, the French mathematician Pierre de Fermat had proposed that light always took the quickest path through any optical system. Imagine you are at the beach, with waves crashing into the shore. Off in the distance, somewhere to the le

ft, you spot something in the water. A person is waving. No, a person is drowning! You have to rush to save them. But which way do you go? You can run fast on the sand, or you swim slower in the water. Dashing straight to the shore, and then swimming out and left will take too long. Should you run along the shore and minimize the time you spend swimming? As you race the calculations in your head, you realise there is a better path. An optimal path! You can run part way along the beach and then d

ive into the water. This path will be the shortest time between you and the drowning man. All other paths are longer. Fermat realised that light travelling from one place to another is like you on the beach. That light takes the minimum time path between two points. The bent path of light as it refracts in water is just like the bent path you take between the land and sea. But Fermat only considered this for light - Lagrangia and Hamilton wondered if this notion could be expanded across all of p

hysics. And so hidden within the equations they found that all nature somehow always chose the laziest of options. This might sound strange. Why does the universe function like this? We still don´t know - but it works. To test this, physicists define what is known as the “action”, And then consider every conceivable possibility of a physical process. Indeed there are an infinite number of imaginary paths that light can take between two points, and for each of these paths, physicists can calculat

e the associated action. It seems that the path where the action is most minimized is always taken by Nature. From Newton’s mechanics and Maxwell's electromagnetism, From quantum mechanics to Einstein’s general theory of relativity, The universe´s laziness ruled supreme. This principle of least action is written in the language of mathematics, And it is this that Emmy Noether was looking at when she noticed something intriguing. She realised that, if the equations possessed symmetries, Then this

would mean that there would be special unchanging quantities associated with the symmetry. This was an idea central to modern physics. The idea of conserved quantities - amounts that do not change. Perhaps the most famous of these is the idea of the conservation of energy. As school children, we are told that energy cannot be created or destroyed, Only changed from one form into another. Throw a ball into the air and the energy you expend is converted into potential energy and then back into ki

netic. Start a fire, and the fuel put in will equal the heat and light that comes out the other side. But that is just the beginning. Physics is full of conserved quantities. In particle reactions, for every positive electric charge that is created or destroyed, An equal but opposite negative charge is also created or destroyed. The total charge of the universe remains a harmonious quantity of zero. In a collision between two objects, the quantity of momentum is conserved. And the amount of mome

ntum before the collision exactly matches that after the collision. And so in terms of momentum, the universe also appears to be harmoniously balanced. But why are these quantities conserved? Other physical quantities - mass, speed, acceleration, temperature – are not - what made these quantities special? What was it that separated the conserved from the non-conserved? The answer, as found by Emmy Noether, is symmetry. Imagine you have a physics experiment set up on a table. Something involving

springs and bouncing balls. You do your experiment and record the outcomes, how the various bits and bobs move and interact. Then you push the table 10m to the left and redo the experiment. Of course, moving the table does not change the outcome of the experiment. The springs stretch and the balls bounce in the same way they did before. The physics controlling the experiment does not change with the change of location. This means that the laws of physics have a symmetry, translational symmetry.

To Noether, the existence of this symmetry had to mean that something was conserved, something didn’t change. And from the mathematics underlying the principle of least action, the mathematics of a lazy universe, She showed that this conserved quantity is just linear momentum, the sum of masses times their velocities. So, translational symmetry implies the conservation of linear momentum. But there are other symmetries hidden in the mathematics, and so there must be other conserved quantities. P

erhaps most startling is the implications of the symmetry in time. Performing the experiment tomorrow should give the same results as today, And so the existence of this symmetry results in the most famous conservation law. For it is this symmetry in time results in the conservation of energy. Emmy Noether had found that the equations led to a remarkable conclusion, tested and proved countless times in the century since: Every conserved quantity in the universe can be traced to an underlying sym

metry, and every symmetry results in a conserved quantity. Although they are not always straightforward… Many are buried in the equations of quantum mechanics, And whilst being subtle, their impact can be profound. In quantum mechanics, things are described by waves. These quantum waves are like ripples on a pond, But unlike rippling water, quantum waves are waves of probability. These waves share a lot of similarities with the oscillations of water. As well as a wavelength that tells us how lon

g a wave is, Quantum waves have amplitudes that tell us the strength of the wave. And, like water waves, quantum waves also have a property known as their phase. The phase is a measurement of where in the cycles of oscillations the wave is. Is the wave in a peak or in a trough? But the properties of an electron are independent of the phase of its wave function - they don´t change no matter how the phase may alter. And it is this symmetry that gives us the conservation of electric charge. Other s

ymmetries in the mathematics of quantum mechanics reveal even more esoteric conservation laws. Baryon number, lepton number, isospin and strangeness to name but a few. Symmetries can even be found that predict the fundamental forces - gauge symmetries for example result in gauge bosons - the gluons that hold protons and neutrons together through the strong nuclear force. The symmetry between protons and neutrons, their inherent similarity, results in this quantum force. And so when physicists un

ravel the complex interactions of particles in the Large Hadron Collider, These quantum conservation laws rule supreme. Inevitably, we should expect that all fundamental interactions are totally bound by these fundamental laws - symmetries and conservation laws operating hand in hand. Everything in balance. And indeed they mostly are. But there are exceptions. And it is these exceptions that may have formed our universe. By the mid-twentieth century, astronomers were thinking about aliens. Giant

radio telescopes scanned the skies for any faint beep-beep from distant civilizations Some wondered just what we would say to our ET cousins when we eventually made contact. But others worried about more fundamental questions - for example the existence of anti-matter beings. The problem was centred around telling left from right. This might seem trivial, but it is implicitly tied to matter and anti-matter, and the twin fates of our doomed intergalactic civilisations. How do you tell an alien t

he meaning of left or right? It’s harder than you think. You can’t send a picture, as they would need to know left from right to properly reconstruct the image. You can’t make reference to trappings of civilization, such as writing, as they again would need a reference. You need to appeal to left and right written into the fundamental universe, You need to find a break in symmetry that allows you to do this. And this all starts with the concept of parity. In 1956, the universe was broken. In a l

aboratory in Washington DC, individual atoms of cobalt were spinning in a magnetic field. The experimenter, Chien-Shiung Wu, was watching patiently for the cobalt to change - to undergo radioactive decay and spit out an electron. In cooling the cobalt atoms and placing them in a magnetic field, Wu could ensure that they were all spinning together, And she could chart the directions that electrons sped away from the cobalt. And conservation of angular momentum meant they should be spat out from t

he poles of the cobalt. Some heading from the cobalt north pole, And the same number emitted from the south. But as Wu sat and counted the electrons, a disturbing pattern appeared. Instead of a mix of electrons heading north and south, All appeared to be escaping from just one side of the cobalt atom. It appeared that this radioactive decay of cobalt was not symmetric! But what did this mean? So what if cobalt preferred to spit out electrons from one side rather than another? It all came down to

a concept called parity. Up until the 1950s, the conservation of parity was core to fundamental physics. It meant that whatever was seen in a mirror universe, Was as real as the physics that is seen in our universe. Think of an atom. When an electron jumps from one energy level to another. A photon of light is emitted. But in which direction does the photon flee? You’d see half of the photons heading to the right, And the other half heading to the left. But what about the view of the atoms in a

mirror? The mirror switches right to left and vice versa. But it also flips spins, from clockwise to anti-clockwise, anti-clockwise to clockwise. So the view in the mirror is half the photons moving to the left, half to the right, And the total amount of angular momentum being conserved. And so the emission of a photon, an electromagnetic interaction, Obeys parity conservation. The same is true for the gravitational force. Imagine a planet spinning and orbiting its star in a clockwise fashion.

In the mirror universe, everything would slip to anti-clockwise motion. At the quantum level, there are other forces that we need to consider. Inside protons and neutrons, quarks interact with quarks, Exchanging a small particle known as a gluon. This is the strong force in action, the force that binds your atomic nuclei together. Both electromagnetism and the strong force respect quantum symmetries and quantum conservation laws. But there is another fundamental force. The weak nuclear force. Th

e weak force seems different. It’s responsible for aspects of radioactivity, changing neutrons into protons and spitting out electrons. But radioactivity is not so common in the universe, And it can seem that the weak force is little more than a bit player. But this all changed in 1955 - when it was realised that the weak force is the strangest of them all. Particle physics had flourished in the first half of the twentieth century. A flurry of particle discoveries and quantum insights peeled awa

y the world of the very small. As patterns and pictures began to emerge in the families of particles, The action of the weak force came steadily into focus. Chen-Ning Yang and Tsung-Dao Lee were at the forefront of this effort. As young scientists at Princeton, they began to explore what nuclear experiments had revealed. They knew that the weak force was responsible for some radioactivity, And that in these decays, the great Wolfgang Pauli had predicted the existence of a ghostly new particle, t

he neutrino. And whilst no one had ever seen a neutrino, The conservation of energy was sacrosanct and so it must exist. Yang and Lee were puzzled, however, over what they saw. They understood that fundamental forces conserved parity, But there was no smoking gun to prove that the weak force understood that this was the rule. And an audacious idea took hold – maybe the weak force didn’t conserve parity - maybe it wouldn't work in a mirror universe. Whilst this sounded interesting as a theoretica

l idea, They needed an experiment that could show that the weak force broke the universe? And this is why Wu had cooled her cobalt atoms and placed them in a magnetic field. Just like a photon being spat out of an atom, The spin of electrons can be switched between clockwise and anti-clockwise, And we should expect equal numbers of electrons heading both northwards and southwards, But this is not what Wu saw in her sensitive experiment! Why would electrons preferentially emerge from one pole of

a spinning cobalt nucleus? The startling conclusion was that Pauli's neutrino could only spin one way relative to its motion. There are only clockwise neutrinos, and, by the conservation of angular momentum, They can only be emitted from one cobalt pole, the electron from the other. A mirror view of the neutrino would appear to be spinning anti-clockwise, And such neutrinos simply do not exist in our universe. The mirror version of the weak force does not exist in our universe - the weak force t

herefore violates parity! This discovery won Yang and Lee the Nobel Prize in the 1957 Nobel Prize, One of the fastest ever awarded in physics, much faster than the seventeen years that Einstein had to wait. Wu, mysteriously, missed out, but her name is written into the history books of science, For the experiment that shook physics to its very core. The weak force violating parity means that neutrinos know right from left, That the universe itself somehow knows right from left. But the weak forc

e goes deeper - and in the following years other forms of parity started to tumble, It turned out there were other symmetries that the weak force liked to crack. And it is now that the mystery of matter and antimatter can begin to be unravelled. It was realised that order could be restored to the Wu experiment if, as well as parity, another transformation was made. If all of the particles were transformed into their anti-particles, Known as a charge conjugation transformation, The mirror view wi

th the spin anti-neutrino could occur in our universe. This double transformation is known as CP for charge AND parity, And so whilst the weak force violated parity, perhaps it would obey CP? But it didn’t take long for a new series of experiments to show this was not to be the case. And this came from the weird behaviour of particles known as kaons. Kaons are mesons, a combination of one quark and one anti-quark. and neutral kaons, kaons without charge, are a mix of a strange quark and a down q

uark. But there are two neutral kaons, one with a strange quark and anti-down quark. And another with an anti-strange and a down quark. This peculiar situation means that the two neutral kaons can mutate into one another, And a beam of neutral kaons has to be considered a quantum mechanical mix of the two. Kaons lifetimes are very short, decaying into lighter mesons, pions, after about a billionth of second, And the conservation of charge and parity together means there should always be three pi

ons in the decay. In 1964, an experiment was set up to explore whether the combination of charge and parity were conserved, Firing a beam of kaons down a long tube, physicists counted the outcome of decays. Almost all of the decays, 499 out of 500, resulted in a burst of three mesons, But one in 500 resulted in only two pions. And here, the universe was broken once again. Charge and parity were not conserved in the decay of kaons. The result won the experimenters, Val Fitch and James Cronin, the

1980 Nobel Prize in Physics, and shocked the world of physics. But what does CP parity violation really mean? What effect does it have on the universe we know? Well - deep down, it tells us that the laws of the universe are different for matter and antimatter. Thinking back to the great meeting of intergalactic civilisations when we first began this finally gives us a solution. The neutral kaons must be considered a quantum mix of matter and anti-matter. And sometimes this quantum mix can deca

y into electrons and its anti-matter partner, the positron. If CP was conserved, these decays should produce equal numbers of electrons and positrons. But again - Cronin and Fitch found that CP was not conserved. For every three hundred electrons produced in decays, there were three hundred and one positrons. And so, all our intergalactic descendants needed to do was to independently undertake experiments with neutral kaons, And they would have known matter from antimatter. They would have known

whether it was safe to finally shake hands. Whilst communication through electromagnetism wouldn’t reveal this. Nor discussions about gravity and the strong nuclear force, Were this distant meeting to occur - would be able to talk to them about experiments with the weak nuclear force. And there we would find absolutes. But why does the universe break these seemingly obvious symmetries? It would be a much simpler place if the physics of matter and antimatter were perfectly symmetrical, perfectly

balanced. Yet that is only the beginning. It seems the implications of CP violation, as it is known, have much more far-ranging consequences for the universe. To truly understand this, we will need to return to the very beginning of time, When the intense fireball of the Big Bang somehow froze. What is the ultimate goal of fundamental physics? Is it to understand what everything is made of? To reveal the origins of the universe? To Einstein, on his deathbed, there was a simple answer. The ultim

ate prize was a theory of everything - a theory that would unite all of the fundamental forces. Gravity, Electromagnetism, the strong nuclear force and the weak nuclear force. Long the holy grail of quantum mechanics and general relativity, sInce Einstein´s efforts in the early 50s physicists have taken steady steps in this direction, first uniting the weak force with electromagnetism in the 1960s. The nuclear strong force took more work, but in quantum chromodynamics, it too joined the party, A

nd the ultimate aim, the focus of fundamental physics for more than a century, has been to incorporate gravity - a goal that physicists have yet to definitively accomplish. But how do physicists build these theories of everything? Once again, guiding them are ideas of perfection and symmetry. Important clues have come from high-energy experiments, where particles are smashed together at high speeds. As the energies of the interactions are increased, something peculiar begins to happen to the fun

damental forces. They begin to change their spots; they alter just how they operate between particles. They start to lose their distinct nature and all begin to look the same. Let’s consider electromagnetism and the weak force in the universe today. They seem radically different, with electromagnetism connecting charges, and the weak force being a form of radioactivity. Electromagnetism is also carried by the massless photon, Whereas the weak force uses three massive particles, the zed-zero and

W plus and minus. But at higher energies, this distinction begins to blur. In what is known as the electroweak theory, these seemingly distinct forces are truly one single force. And so when the universe was hot and young, only this single force existed, It was the cooling of the universe through the Big Bang that broke their symmetry and made them distinct. At higher temperatures still, the distinction between electroweak and the strong force fades away, And it’s thought that at ultra-high temp

eratures, gravity too becomes indistinct. This suggests that at the universe's birth, there was one true force, the super-force. And this super-force was perfect and symmetrical. The bible begins in Genesis with the line “In the beginning was the word, and the Word was with God, and the Word was God.” The bible begins with godly perfection that was ultimately corrupted. Modern cosmology begins in a very similar fashion. In the beginning, the universe was perfect and symmetrical. There existed th

e one true super-force, and it reigned over all. But this ultra-hot universe expanded and cooled, And fractures appeared in the perfect symmetry of the cosmos. Out of perfection, imperfections began to appear. The individual force separated, first gravity, then the strong force. As the universe continued to cool, the weak force separated from electromagnetism. But the separations of the fundamental forces as the universe cooled were not uneventful. As a force went its own way, the very nature of

the cosmos changed. The universe before and after the separation was distinctly different – it had undergone a phase transition. As temperature decreases water freezes into ice - its symmetry is reduced. In the same way, the separation of a fundamental force as the universe cooled marked a distinct fracture in the symmetry of the universe. Cosmologists think that these separations impacted the important features of reality. Gravity separating was at the Planck time, when the universe was about

10-43 seconds old. This is an age of the universe we know almost nothing about, And until we can write down our grand unified theory uniting the quantum realm and gravity it may forever remain a mystery. But the separation of the strong force is different. It occurred much later - at about the age of 10-34 seconds. And this is a time that physicists think they have a much better handle on. For this is about the time that inflation blew up the universe. In the late 1970s, Alan Guth was worried ab

out the cosmos. He had started his research career in particle physics, hunting for grand unified theories, explanations for everything. As well as hunting for a permanent position as a professor. But in 1978, he attended a lecture that changed everything. The speaker was Robert Dicke, an elder statesman of science. Being at the other end of his career to Guth, Dicke had explored many mysteries of the cosmos. And in this talk, he was wondering just why the universe appeared to be flat, rather th

an curved like a sphere or a saddle. Somehow the birth of our universe must have been fine-tuned, Selecting flatness from all possible geometries. Guth was intrigued by this seeming specialness of the universe. And wondered if it related to the fact that a chunk of the universe appeared to be missing. A chunk predicted once again by symmetry. The motivation was James Clerk Maxwell on the nature of electricity and magnetism. His equations were profoundly asymmetric, possessing electrical charges,

but no magnetic equivalent. All magnets we see have a north and south - all are duopoles. Many before Guth him had wondered where these “magnetic monopoles” - pure magnetic north or south poles - may be. And so Guth decided that they must be hiding. In the earliest moments of the universe, when it was hot and dense and seething, Guth suggested that electromagnetism was symmetric and that magnetic monopoles were part of the cosmic mix of particles. But as the universe underwent an immense burst

of expansion, doubling 80 times almost instantly, The magnetic monopoles were thinned out enough so there was only one per observable universe. After this period, known as inflation, there wasn’t enough energy in the universe to create new magnetic monopoles. They were effectively lost, never to be seen in a physics laboratory. What happened to the universe during its dramatic expansion? A background field of energy, known as the inflaton, must have dominated. The density of the universe fell pr

ecipitously, as all particles were robbed of their energy. And the universe became a frozen empty place. But space still seethed as the inflaton eventually decayed, and inflation came to an end. And the energy of inflation was dumped back into the universe. Reheating the universe to many billions of degrees and creating the matter that inhabits the universe today. But the magnetic monopoles were long gone. And all this started around the same time as a phase transition - just as the strong force

separated. Was this just a coincidence? Or was it the departure of the strong force that seeded the inflaton with energy? We are not sure. Indeed, our knowledge of the physics of this epoch is still a little hazy in parts. And so we cannot truly be sure we have found the true culprit of inflation. Some have also tied the inflaton to the formation of the Higgs field, the field that gives particles mass. Whilst others have wondered if the inflaton is just an early incarnation of today’s dark ener

gy. And so when the universe was about 10-12 seconds old, and a balmy 1015 K, All of the fundamental forces had separated into the distinct forms we know today. But the action of symmetry breaking Still had one more trick to play. For it was in this epoch that baryogenesis occurred. This is the time when the soup of fundamental particles, quarks and gluons, Began to condense into protons and neutrons, And the matter in the present universe, the matter of you and me, was finally born. But a probl

em of symmetry remained. Remember that the energy of the inflaton was poured into the universe after inflation, And this is the ultimate source of matter and photons in the cosmos today. This reheating should have equally produced matter and anti-matter. One of the starkest asymmetries in the universe today is the odd preponderance of matter over anti-matter. Cosmic searches have revealed a wealth of matter across the cosmos - and the barest traces of anti-matter. As an example, scientists belie

ve there is about 1 part of antimatter to a quadrillion parts of normal matter within our Milky Way. So where did this asymmetry arise in the lifetime of the universe? Why is there so much more matter? It is thought the answer is buried deep somewhere in baryogenesis. Whilst we know and have seen that the laws of physics can differentiate between matter and anti-matter, The degree of difference is simply too small to account for the difference in matter over anti-matter. And so we are still scra

tching at the fundamental laws of the universe to understand why there is any matter at all. We can estimate the degree of matter/anti-matter asymmetry from an unlikely source, the cosmic microwave background. These photons were emitted when the matter and anti-matter in the universe finally annihilated, And for every proton or neutron in the universe today, There are about a billion of these cosmic microwave background photons. This means that the universe must have been almost symmetrical. For

every billion anti-matter particles, there must have been a billion and one matter particles. And it is this tiny difference that is the source of all the universe’s mass today. It is sobering to think that we are only here because of this tiny asymmetry. But there is still one final mystery that symmetry could reveal. If symmetry is our true guide, and fundamental physics is purely symmetrical, There should be more than magnetic monopoles out there in the universe. Within a super symmetric the

ory for example, for every quark there should be a symmetric squark. And for every electron, a super symmetric selectron. This naming process carries on throughout the standard model - from sneutrinos to smuons for bosons, and higgsinos to photinos for bosons, a hidden supersymmetric universe of sparticles would be lingering just out of reach. Supersymmetry is a key part of many potential theories of everything - and scientists had long expected to finally find evidence in the LHC. But hunts for

these mysterious particles in our colliders have so far yielded none of these super symmetric candidates. All we find are the usual suspects, the quarks and electrons of our universe. Some physicists have claimed symmetry has led us astray and that we are on the wrong path. But for others, symmetry is simply too alluring, and the hunt for super-symmetry and the super-force continues. We are almost at the end of our journey. And we have seen that symmetry is clearly central to our understanding

of the universe. But it is really the breaking of symmetries that gives the universe its peculiar personalities. The fundamental laws and the existence of matter truly arise from cracks in perfection. But before we close, there is one final thing to consider. It feels like the breaking of symmetries is something about the distant past, Yet our universe is still expanding, still cooling, still changing. And we are mere footsteps into the infinite future ahead. Hidden in energies well below our ex

perimental reach might yet be other undiscovered symmetries, And as the universe continues to cool, one day these too might crack, fracture and break, unleashing new forces and new phases that could radically change the cosmos. Our universe’s march from perfection to ultimate corruption might not yet be over.