A VERY soft spoken British man tells you interesting space facts while you sleep

how are we ever to prove that there are universes other than our own and that they are run on different lines other universes by definition are not part of our universe and so cannot be contacted so it could be that the multiverse idea might also lie beyond the realms of science when thinking about our universe being life friendly one can't help wondering whether there might be other forms of life out there and it's intelligent how does that affect the status of us humans what do we know about the human brain and consciousness or to put it another way what can a brain know about itself chemical flows electrical currents some liken it to this an elaborate computer but unlike this or any other computer that's been built so far the brain is conscious it's aware of itself all that physical activity is accompanied by feelings and emotions this was an early attempt to try to associate different parts of the brain with different mental experiences this shows a person when they are meditating and when they are not meditating but which is which which one shows the person meditating we can't tell not from just looking at these these scans not until the subject tells us that that is what they're doing they're they're meditating okay once they've done that when we come across the same sort of brain pattern in someone else say it's a good bet that it will be accompanied by the same sort of mental experience again but without a subject volunteering the information about the mental experience in the first place we get nowhere in fact why are there conscious mental experiences at all we don't even know which things are conscious i'm conscious i know that from a direct experience you well you have a brain like mine and you talk about having mental experiences so okay i'll give you the benefits of the doubt how about this well not exactly this but you know a proper chimpanzee are chimpanzees conscious are they aware of themselves well yes what about this a worm is a worm conscious could they feel pain well there's one way to find out cut it in half and see what happens both halves are writhing about so what does that mean you know the it now has two minds whereas previously it only had one or does it not have a mind at all and what about these bacteria you shouldn't have thought so the sun well definitely not the sun humans definitely yes the sun and definitely know but where was the dividing line how how could we ever find out this is the problem of consciousness how to understand the brain in relation to conscious mental experience are we dealing with with two separate things a brain and a mind somehow they're they're interacting with each other uh that's one theory but it's it's not very popular these days is there just the one thing which we approach in in two quite separate ways atoms electricity spatial orientation and and another more language where we talk about your pain and and love and happiness the kind of you would never find in in a physics equation all right and and one needs both languages it's understanding of what's going on consciousness poses a a big big problem see how we'll ever have a fully satisfactory answer to it one that everyone agrees about it's a close encounter of the first kind with what i call the boundaries of the knowable you see science science has its limits in fact science will grind to a halt scientific discoveries not when we've discovered everything complete knowledge nothing more to know but when we've discovered everything that is open to us to understand which is not the same thing don't get me wrong it's not going to happen soon and the applications of science so they'll continue to all be plenty of scope for new gadgets and things like that and updates of computers and playstations that sort of thing technology will continue but not fundamental science not not not the discovery of of new laws of nature why do i say that in the first place we have to consider what we do our science with this but how do we come to have a brain in the first place according to the theory of evolution it's something that has been fashioned in it helped our ancestors to find food shelter a mate it helped them to predators it was part of their their survival kit capable of understanding everything about the world that wasn't necessary for our ancestors to survive a second reason why we might not be able to complete our understanding of the world has to do with with practical considerations i i'm what's called a a high energy nuclear physicist it means i'm interested in discovering the ultimate structure of matter what what everything is is made of and and and what holds it together to do this we have to accelerate tiny subatomic particles to great energies and then we smash them together to see what happens the big international laboratory where i i used to work is in fact just a small section of a great giant circular machine 27 kilometers in circumference that's geneva airport to show you in comparison give an idea of the scale as a general rule each time we've built a machine we've made discoveries that were quite unexpected and this raises a question crucial piece of evidence now the there's no reason why the final clinching experiment has to fit in with what we humans happen to be able to afford or or can physically build and without that last crucial piece of experimental evidence our theories about the world could remain forever incomplete and then there's there's a third reason for suspecting that science will eventually fall short of providing us with a complete understanding of everything the fact that we can perhaps already discern where some of those limits might be stubborn questions that have been around or for a very long time questions to do with the nature of space and of time of matter of light stuff like that perhaps because for us they are intrinsically unanswerable they are at the boundaries of the knowable how are we to understand consciousness is but the first of those questions stop sulking wally sorry if i frightened you no animals were hurt in the making of this program okay you've had your 15 seconds of fame it's now time to go back to work in the garden all day long we have to make choices okay i happen to choose this one i could just as easily have chosen a brown one or a red one or could i was i really free to choose we do all our thinking with our brain but the brain is a physical object the behavior of physical objects is governed by the laws of nature even with apparatus this complex we can still predict how it's going to behave well not me personally i i don't understand these things but the computer experts understand what's going on there for them it's it's all predictable in which case what if what if someone were to examine the workings of my brain in the same way as a computer engineer can examine the workings of the computer he examines my brain just before i make my decision as to which suite to take he applies the laws of nature and predicts with certainty what the state of my brain will be after making this decision this so-called decision surely that way he will know what my choice is going to be that i'm about to pick the the blue one even before i even before i know what i'm going to do it's all predetermined i i have no choice no no real choice i'm just going through the motions this is the so-called free will determinism problem how to reconcile the grinding predictability of the physical brain and the physical world in general with the mental sense that the future is is open the sense that it's it's up to us to decide what it will be we have freedom to make genuine choices it's a problem that scientists and philosophers have wrestled with for centuries recently some have sought to solve the problem by calling upon quantum theory quantum theory is necessary for the description of the behavior of very small objects atoms and and subatomic particles what it shows is that on the very small scale the future is not predictable not with absolute certainty the electrons that make up an atom we never know where we're going to find them next time we look and know it it's not a case of look more carefully or invest in more expensive measuring equipment no no this is this is a built-in uncertainty an uncertainty so that's absolutely fundamental to nature itself at the subatomic level all we can ever hope to do is to predict the odds of various possible outcomes which of course doesn't seem to square with normal everyday life where things are predictable up to a point but here we're not looking at individual atoms this array is made up of a vast vast number of of atoms so what we're looking at here is the is the average behavior of many many atoms and that average behavior is predictable but not the behavior of the individual atom or subatomic particle that is governed by so this raises an intriguing possibility if the action of the brain corresponding to the making of a choice if that action is something happening on the very small scale up here perhaps involving the movement of an individual atom then the behavior is not predetermined it's subject to chance random chance and some have latched onto this to claim that that is how we come to make a free will decision uh the blue or the red what could i do okay blue tails redheads but is that me making a decision a conscious decision no that's me leaving it to chance opting out of making a conscious decision now quantum uncertainty with its dependence on chance seems to go the way of all previous attempts to solve the free will determinism problem it's a problem like that of consciousness itself a problem we seem to be stuck with i can't see how it will ever be solved not to everyone's satisfaction what kind of world do we live in or kind of of universe well thanks to telescopes more like for example that one over there and today especially the the hubble telescope out in space we know a great deal about what's out there the structure of the universe how it came into existence how it got to be the way it is today beginning with planet earth we know it to be part of the solar system our sun is a star much like all the other stars stars are gathered together into great swirling whirlpools called galaxies our galaxy is called the milky way galaxy galaxies in their turn are gathered in two clusters of galaxies and these clusters stretch out into space as far as we can see and when we observe distant galaxy clusters we find that they are all receding away from us the further off a galaxy cluster the faster it's receding into the distance and all this seems to point to the idea that at some time in the past all the matter of the universe was gathered together the big bang and everything flew apart the motion of the galaxies we see today is exactly what we would expect if it had resulted from such an explosion not only that but knowing how fast a galaxy cluster is moving and its distance from us we can work back to when everything must have been together in other words when the big bang occurred it turns out that it happened uh 13.7 billion years ago that gets switched off right about here and then we get the normal sort of expansion we see today happening along here we call that the expansion edwin hubble was the astronomer who first discovered the universe was expanded in saying that in inflation took place over a brief period i i mean really really brief it all happened in the space of a tiny tiny fraction of a second that's why we're we're talking about what happened a tiny fraction of a second after the instant of the big bang yep you know it's a truly mind-blowing achievement the big bang was such a cataclysmic event that we assume it must have marked the point when the universe came into being in which case it appears natural to ask what caused it now what caused the big bang and what came before the big bang but there's a problem it's all very well talking about what happened immediately after the incident of the big bang you know inflation tiny fraction of a second there is all the difference in the world between saying what the universe was like a tiny fraction of a second after the instance of the big bang and what it was like at the instant of the big bang let alone what might have happened before that instant you see at that instant all the matter of the universe would have been squashed down to a point a place of no volume so the density would be infinite and there's no way our physics can handle a situation like that we we call it a singularity we can't handle it but at least we can give it a name we call it a singularity and that means we have no hope of extending our investigation through that instant to what might have preceded it to what might have caused the big bang okay that's that's that reason why the question what caused the big bang can't be answered but there might be an even stranger reason they also mark the coming into existence of space and the coming into existence of time bound up in einstein's theory of relativity so there was no time before the big bang now for those seeking a cause of the big bang there's a problem here i stir the coffee that's the cause and what you see happening there is the effect first the cause then the effect the effect here is the big bang so the cause of it must have existed before the big bang but where the big bang is concerned there is no before extrapolate through that point of of infinite density no the problem goes deeper than that the question probably has no meaning there is no time to accommodate a cause so there can't be a cause augustine was once asked you know what was god doing before he made heaven and earth and augustine replied he was creating hell for people who ask questions like that in fact this is a fairly common problem when exploring science at its deepest levels the boundaries of the knowable perfectly fair question you know what caused the big bang but is it no a much better question in this particular instance is this why is there something rather than nothing we're not talking specifically about the mechanism of the big bang no we're asking the very general question why does anything exist you see if nothing existed or had ever existed why should anything exist but as soon as something exists anything at all then the questions start why does this particular kind of thing exist and not something else what is responsible for their existence and once having got something into existence does it need an agency of some kind to keep it in existence science does not address questions like that it takes the world as a given his job is to describe the world as it happens to be be a world in the first place to say that the question why is there something rather than nothing can be ignored it might well be a meaningful question it simply lies beyond the boundaries of scientific inquiry the sun and the other stars are great balls of fire the depths of space by contrast are freezing cold the distances involved are immense it's perhaps not surprising that many people view the universe as hostile to life the physicist stephen weinberg once dismissed life as a more or less fossical outcome of a chain of accidents but first impressions can be deceptive here are some of the the laws of nature the laws that govern how the cosmos evolved and govern all that goes on around us now it turns out that if these laws have been fixed at random if the with the strength of the gravitational force or the strength of the electrical force or all the masses of the subatomic particles all the violence of the big bang if any of these have been chosen purely at random then the chances of having a world with life any kind of life would have been virtually zero so the universe appears to have bent over backwards to accommodate life this observation goes under the name the anthropic principle as another physicist freeman dyson somewhat colorfully put it the universe knew we were coming so how are we to account for it the way the universe is so life friendly was it specifically designed as a home for life by some creator that's one possibility but that of course takes us way beyond the realms of science some seek to solve the problem by suggesting that our universe might not be alone there are other universes lots of them perhaps an infinite number of them the whole ensemble is called the multiverse and the idea is the laws of nature are different in all the individual universes in the vast majority of them there is no life because one or other of the conditions was not satisfied but once in a while that comes along the universe which happens to have the right set of conditions for the development of life we being a form of life ourselves must of course find ourselves in one of these freak universes well fair enough that would look for why our universe is life friendly that simply raises another problem how are we ever to prove that there are universes other than our own and that they are run on different lines other universes by definition are not part of our universe and so cannot be contacted so it could be that the multiverse idea might also lie beyond the realms of science when thinking about our universe being life friendly one can't help wondering whether there might be other forms of life out there and if there is life and it's intelligent how does that affect the status of us humans well as far as our solar system is concerned the planets circling our sun there might be some forms of very primitive life we should have the answer to that quite soon as a result of planned space probes but not intelligent life now if if et exists it must be on a planet going around some other star what we call an exoplanet and there's no shortage of those several hundred have been found and the tally increases weakly most of them will not be habitable from the law of averages there must be many many earth-like planets out there planets where intelligent life could flourish which is not to say that that it has so a big question is whether or not there is extraterrestrial intelligent life and if so what's it like evolution on earth took a very long time billions of years so on some other planet it is only to get out of step with what happened here on earth to only a small degree for e.t to have reached our level of intelligence the intelligence of a charles darwin to have reached that level a long long time ago so that means they must by now be way ahead of us except except the human race has got this far in intelligent because in the past there was survival value in having a superior intelligence you had a better chance of surviving to the point where you could mate and pass on your superior genes but does that still apply today do the more intelligent people today have more children than the less intelligent if anything i i'd have thought it was the other way around after all the more intelligent you are the better your chances of getting a well-paid job and the better paid job leads to a higher standard of living and the fewer children you're likely to have if that's true of us perhaps is also true of e.t on the other hand when e.t reached our stage of development you would know all about dna and genetic engineering so all we know they might be heavily into genetically engineering designer babies with superior intelligence a case of directed evolution rather than relying on evolution by natural selection in which case as we previously thought they will now be vastly superior to us on the other hand when they reach our stage they discover nuclear power and in all probability in a comparatively short perhaps that's the fate of all intelligent species throughout the cosmos they reach no further improvement go and visit them science fiction adventure stories no hardly the the distances are just simply too far space travel is is not the answer the other approach is to search the skies for for any signals indicating that et is trying to communicate with us such searches have been carried out for many years by the seti program the search for extraterrestrial intelligence but so far without success they'll find anything even if et exists they might not have the means to communicate with us or not the desire to communicate with us the situation is it's not under our control it's up to e.t perhaps we're destined never to find out about intelligent life elsewhere in the universe i'm not just thinking of of outer space i mean any sort of space in space here the space where you're sitting well the answer seems obvious you know empty space is just another name for for nothing but that's not how the modern physicist views it take for example a space station it's orbiting the earth why why doesn't it just go drifting off into outer space in a straight line gravity the earth's gravitational force acting on it well fair enough but what if an astronaut steps outside the spacecraft he too is orbiting the earth and in more or less the same orbit why earth's gravity again but the astronaut is much lighter than the space station so in order to get him to go in the same orbit the gravity force on him has to be less than on the craft so how does gravity know how much less it has to pull on him than on the craft and in any case why would gravity want them to go in the same orbit the puzzle is solved once one sets aside the idea of the earth exerting gravitational force and instead thinks of gravity curving the space around it okay this is something i've rigged up this surface represents uh normal empty space and if we have an object uh going through that space perhaps a spacecraft then the natural path to follow is a straight line like that but look what happens once i put a heavy object into that space the earth now you see what it's done to the to the surface it's it's curved the surface so now that the natural path for an object passing through it like a spacecraft is no longer a straight line it's a curved path a bit like this okay well forget about the the the spiraling in um that's just due to the friction we've got here but for the spacecraft above the atmosphere there's no friction to speak of so we get a steady repeated orbit let me just show you how it comes about that the astronaut and the at the same sort of speed as you see i've got a curved surface here and now we'll make the heavy ball represent the spacecraft and the lighter ball is the astronaut who's just stepped outside the spacecraft to go for a space walk so the reason why the astronaut and the spacecraft follow the same orbit is that that is the natural path to follow the natural path is no longer a straight line a straight line which has then got to be curved because of the action of a force this way of viewing gravity we owe to einstein it's part of his theory of relativity so space is is not nothing space is something a mysterious something that can be curved and that's not all the universe is expanding distant galaxy clusters are receding into the distance this is all in the aftermath of the big bang but that's not to say the galaxies are moving through space into an outer space where previously there had been nothing no they're moving because it's it's space itself that is expanding the space between us and the distant galaxy it's carrying the galaxy along on a tide of expanding space okay here i've got some galaxies because the rubber in between the galaxies has expanded and carried them along with it okay that's what's happening out there space so-called empty space is pushing the galaxy clusters apart of the various stages of the expansion of the universe the big bang occurred here and that's followed by the more gentle normal kind of expansion like what i showed you with the balloon because of the mutual gravity between the galaxies but look what's happening here the rate of expansion is now increasing this is due to what is called dark energy space empty space has energy whereas matter attracts through its its gravity empty space through its dark energy repels but it can also push around heavy things such as galaxies it's not simple at it's a deeply mysterious something but what we all start our thinking there's just the one time the same for everyone but einstein's a theory of relativity shows that this is not the case two people moving relative to each other they have their own times and they're not the same at normal speeds me moving relative to you like this at these sorts of speed the difference between your time and mine it it's not obvious it's it's too tiny to notice but at high speeds really high speeds the effects become enormous suppose for example we have a spacecraft and it's flying to a distant planet and just suppose it's going to speed equivalent to well let's say nine tenths the speed of light around 270 000 kilometers per second not realistic but i just suppose it's time itself that is slowed down it's called time dilation now you might think that the astronaut would find this all very strange living in a world of slow motion but no his thinking processes will be slowed down and in the same ratio and if you look at a slow watch with a slow brain it appears normal so for the astronaut everything happening in the craft appears perfectly normal it only appears slowed down to the mission controllers but you might think well sorry you know the astronaut will know his time has been going slow when he arrives at the distant planet the expected time no there's a second effect of relativity theory this is the situation as seen by the mission controller here we have the earth and this is the planet for which the astronaut is journeying but according to the astronaut this is what it's like relative speed affects not only time but also distances according to the astronaut traveling at 270 000 kilometers per second the distance from the earth to the planet is only half of what the mission controller says it is it squashed up the earth and the planet themselves they're squashed up in fact any length seen to be moving relative to the spacecraft according to the astronaut will be squashed up it's what we call length contraction so we have time dilation and also length contraction the mission controller says your time is running slow the astronaut says there's nothing wrong with my time it's your distances that are squashed up it all makes perfect sense except it doesn't agree with what the mission controller says is going on okay if this is the first time you've come across this sort of thing that it it all seems quite bizarre it's all been tested out and found to be true not with the spacecraft and flying about at speeds close to that of light but but here higher energy physics laboratories like cern just outside geneva here we can check out einstein's theory using subatomic particles hurtling around the particle accelerator at speeds that are indeed very close to that of light this is the the large hadron collider if you yourself were to travel at the speeds achieved here you'd live to be half a million years old that's a time dilation as i say all this sounds very confusing you know different people having different ideas about lengths and and times but fortunately there is something the astronaut and the controllers over there in fact all observers can agree on comes about like this we're used to thinking in terms of three-dimensional space up down sideways backwards forwards so three axes at right angles like this are a separate one-dimensional time three-dimensional space as it moves up the time axis but what if we're wrong and they are joined together a four-dimensional space time that's what we call it space time what would we expect to find in this four-dimensional space-time well should be characterized by a particular point in space as measured along the three spatial axes a particular point in time as measured along the time axis in short we're talking about events one event might be the the launch of the spacecraft at that's its point in space the launch also taking place at a particular point in time three two one blast off a second event will be the arrival of the spacecraft at the distant planet at a later point in time now what one finds is that although the two sets of observers the the astronaut and the mission controllers they they don't agree about either the spatial distance about the interval between those launch and arrival events in four-dimensional space-time and it's because everyone agrees about what the situation is in four-dimensional space-time our familiar time and space that they're nothing more than appearances appearances of this of this reality subjective appearances as seen from some specific point of view okay now you know different appearances well i'll take this pen it has many different appearances depending on on the angle one is looking at it now sometimes it appears short but sometimes from from another angle from another point of view it appears long this is because all we see with with our eyes or photograph with a with a camera is it's a flat two-dimensional projection a projection of something that is actually solid something that exists in three spatial dimensions uh not not just just two so what we're saying now is the space by itself is but a a three-dimensional projection a projection of something that is actually four-dimensional and the time interval is nothing more than a one-dimensional projection of this four-dimensional reality as einstein once said henceforth we deal in a four-dimensional reality not a three-dimensional reality evolving in time times and distances but does it this four-dimensional space-time is sometimes called the block universe and also all of time present and future this point here that represents the present instant and then on this side uh that point there is uh when we started the program and i say the subject of time has always fascinated people and uh and here on the other side that's when i say fathom the riddle of time and the program comes to an end and you can take a headache pill on an equal footing according to the the block universe idea the future already exists it's out there waiting for us to come across it and experience it consciously it's static nothing nothing changes in the block universe changes occur in time all right but time is not here time is in it but if nothing changes how can we experience a flow of time time rolling on how can we have this impression that whatever exists is what is present instant we can't be sure because it doesn't yet exist what we're talking about now is is the mental experience of time an experience that seems not to be reflected in the physics in fact the physics community is deeply divided over the concept of the block universe it's that space-time is is real that it's the reality instead of some or some abstract mathematical thing so does all of time exist including the future in some sense and if so in what sense exactly will we ever fathom the riddle of time or is this another encounter with the boundaries of the noble what is everything ultimately made of it was once thought that the answer was atoms atoms the fundamental building blocks of matter which cannot be cut which is hardly the case atoms have an inner structure they consist of a central nucleus surrounded by tiny particles called electrons the nucleus has a positive electric charge the electrons a negative charge and it's the electrical attraction between these charges that holds the electrons close to the nucleus electrons are considered to be truly fundamental they really are one of the basic building blocks of the matter we see around us the nucleus is that fundamental no it too has an inner structure it's made up of neutrons and protons the neutron and proton are very similar to each other it's just that the proton carries a positive electric charge whereas the neutron has none it's the charge on the protons that gives the nucleus as a whole its positive charge but you might be thinking hold on but won't the nucleus no things are more subtle than that okay here i have two protons right i'm going to push them apart that represents the electrical repulsion but they don't separate why because there's another force at work an attractive force nuclear force is more powerful than the repulsive electrical force and that's what leads to an overall attraction holding the nucleus together and and neutron fundamental like the electron nope when you look inside them you find that they're made up of tiny tiny particles called quarks a bit like the pips in the apple two types of quark what we call the the up quark and the down quark which we denote by u and d the proton has two ups and a down and the neutron two downs and an up so both the proton and the neutron are made up of three quarks each quarks like electrons are believed to be truly fundamental they mark the end of the line so everything we is made up of two kinds of quark up and the down together with the electron and to this we need to add a fourth particle the neutrino neutrinos are produced for example in the nuclear reactions going on in the sun the neutrino is like the electron except that it carries no electric charge and so it doesn't experience the electrical force and like the electron it doesn't experience the strong nuclear force either that's only felt by the quarks but it does experience what we call the weak nuclear force that's a force responsible for or for certain kinds of radioactivity so because they experience only this weak force neutrinos are famous for hardly interacting with anything at all 100 billion solar neutrinos can pass through my thumbnail every second and i don't feel a thing so there we have it constituents of mata the up and the down quark the electron and its neutrino what could be simpler except that it is not that simple it's much more interesting it accelerates protons around in a huge circle two beams in that tube traveling in opposite directions one going clockwise and the other anti-clockwise and the various points they're made to collide why what what's it all about no the original motivations but actually something much more intriguing than that happens new matter being created didn't we learn at school that matter can be neither created nor destroyed yes and and that's that's still true you know this new matter arises from the from the brought into the collision by the original bombarding particles it's a consequence of einstein's famous equation e equals m c squared is that some of these new particles carry properties that ordinary matter doesn't have properties that have been given quirky names strangeness charm top and bottom i myself had the privilege of belonging to the international collaboration that was the first to make a direct sighting of a particle carrying charm now like the proton and the neutron these new particles are made up of strongly interacting quarks but because of these new properties the new particles can't all be made of just the two types of quark that we've been talking about so far the ones that make up the proton and the neutron now we need to add more fundamental particles different quarks one carrying charm one carrying strangeness one for top and one for bottom three groupings or four particles each of these groupings called a generation three generations one two and three these are the ultimate constituents of all the matter we see around us plus all the more exotic types we create in these high-energy collisions unraveling all this has been a wonderful achievement but we're still left with some worrying puzzles three generations why three why not just one or if you're going to have more than one and why not an infinite number what's special about three of these particles what determines the values of their masses and their masses are very odd the tau particle for example than the electron as for the neutrinos they are so incredibly uh light that for a long time it was thought they had no mass at all weighs 50 to 100 000 times as much as the up quark what what does it all mean we simply don't know in fact in order to make sense of our understanding of the nature of matter and the forces between them we need to feed in by hand the values of 19 different parameters being a high-energy physicist myself it remains my hope that one day someday we shall be able to find answers to these outstanding questions but i can't help wondering how close we might be getting to the boundaries of the knowable well what is light for a long time it was thought the answer is obvious light is made up of waves electromagnetic waves undulating electric and magnetic forces traveling through space much like waves on the surface of a liquid okay this seemed obvious for for a number of reasons for example when waves pass through a narrow gap in a barrier they spread out somewhat to the side rather than going straight on and then that's what light does put two gaps close together and the humps and troughs from the two gaps overlap and interfere with each other this gives rise to directions where the humps and troughs are in step and they reinforce each other and then in between the humps and trolls are out of step they cancel each other out and you get very little activity now this is exactly the kind of behavior we get with light past light through two parallel slits and we get white beams going off in a number of directions with little in between liquid you get from a spray can for example okay i can demonstrate this like this that light is made up of waves except if you examine closely how light gives up its energy when it hits the screen using a very weak beam all you see at first are the smoothed out distribution you might expect if flight were a gently undulating wave as more and more light arrives on the screen so you get more dots and the interference pattern begins to emerge but note the energy is being given up as localized dots we call these tiny bundles of energy photons can only be explained by saying light is particles so the crucial question becomes how can something be both a wave spread out over space with a succession of humps and troughs point like particles this dilemma is known as the wave particle paradox and atoms are made up of a nucleus surrounded by electrons the nucleus is made up of neutrons and take a beam of electrons like the ones you get in the in the older style tvs and computer monitors the electrons are emitted from an electron gun at the back of the tube and then they travel to the screen where the energy that gets converted into the light that makes up the picture that we see they hit the screen like a hail of tiny bullets and this shows how those interference electrons the the other constituents of of mata protons they they also exhibit wave particle duality complete molecules everything is afflicted by wave particle duality so well back in the 1920s the the danish so for example take the case of the electron in in the tv and hence where exactly define it on this tiny particles how it interacts when it gets to its destination there's never any call to have to use the concept wave and particle at the same time is solved but the solution comes at a price the price is such questions are meaningless suppose for example out there in empty spaces there's an electron on its own not being observed not interacting with anything [Music] under those circumstances what is it is it a wave or is it a particle observations it's a misuse of language to try and use those same words to describe what might exist in between the observations what you eventually write down in your science textbook is a description of it is possible to ask whether there is still concealed behind the statistical universe of perception a true universe in which the law of causality would be valid but such speculation seems to us to be without value and meaningless for physics must confine itself to the description of the relationship between perceptions the relationship between perceptions the relationship between observations one of the most fascinating fields of study at the present time is the theory that the fundamental constituents of nature are not point-like particles but strings [Music] tiny vibrating strings called super strings a bit like this and depending on how the string vibrates you get different particles so this might be an electron that might be a quark and this might be a bundle of light energy called a photon each different particle is a different mode of vibration of the same sort of string now with the string only certain modes of vibration are are allowed only certain modes of vibration are allowed and these different modes will have different energies and because energy and mass are related einstein's theory of relativity e equals m c squared e the energy equals m the mass because of that these different allowed energies will correspond to different allowed masses in other words only certain masses are allowed which is exactly what it is with quarks and electrons now the fundamental particles differ in mass but they also differ in other ways and some have electric charge others don't account for the additional properties by invoking yet further in the way the super string vibrates vibrate in two directions that way and that way the ends not being fixed and that will give you vibrations in that ray which would add variety a bit like this with a slinky spring you can um it turns out that if we could have vibrations of this which would be great take that pointer over there uh the other day i noticed there was a chalk mark on it i i meant to clean it off how can i specify where the mark is on the pointer well how far was it from the end well i noticed it was 18 inches well let's go and take a look nine eighteen no mark oh wait in saying it was eighteen inches from the end we haven't specified precisely where the mark is all that tells us is that it's somewhere around the circumference of the cross section that's 18 inches from the end if i twist it around there we are here are the the three familiar extended dimensions with x1 x2 and x3 and what i've tried to do here for that point there is to to show you two extra curled up dimensions we've got x4 there and we've got x5 there and that's as far as i can go as far as the drawing is concerned and you'll be you can't in fact form a mental image of it in fact there should be six curled up dimensions there and not not just a true of that particular point in space but of every other point in the normal conventional three dimensional space six extra curled up dimensions at every point as well as the three extended ones being super strings vibrating in nine spatial dimensions and one dimension of time but the worrying thing is that despite so many people working on this problem for the past 30 40 years they have yet to come up with a single prediction that could be verified you see it's all very well talking about string theory but there are many variants of string theory now the geometry of the curled up dimensions might be more like this x4 and x5 or some other twisted topology not nine same goes for the super strings themselves they are tiny forget about the large hadron collider at cern 27 kilometers in circumference that's absolutely no good at all uh for seeing strings the strings are believed to be so small it would take an accelerator this or the size of a galaxy in order to be able to observe them directly and to check that they really are strings finite size strings and not point like so what does that mean are we destined never to know whether this attractive idea is true or not these are but two of the major questions facing fundamental science today what we've been looking at in this series is not meant to be an exhaustive list of outstanding questions facing science today other scientists were doubtless of right to see mention of but when we have discovered whatever is open to us to understand when we have finally come up against the boundary of the knowable in all directions when will that be who knows 100 years from now a thousand years indeed i don't see how we or more strictly speaking our descendants how they will even know when science has come to an end rather than thinking that it's just going through a particularly boring bad patch which is itself quite a thought not only are there things we should never understand we shall never even be sure what it is we should never understand

Channel: Pure Unintentional ASMR

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Id: ysVVtI-0F8k

Length: 69min 22sec (4162 seconds)

Published: Fri Dec 03 2021