how long is now there is a legend among the more advanced civilizations of the universe one whispered quietly passed down through the generations the story of the star whale a formidable creature that can open its Cosmic mouth and swallow solar systems whole in a single gulp one flick of its Mighty fluke can lay waste to entire civilization the oldest libraries in the cosmos hold the most ancient of books all with drawings of this Leviathan pieced together from rumor and heay its leathery skin is said to be encrusted with Barnacles of star stuff it's enormous baline plates peppered with billions of years worth of interplanetary Plankton at least that is billions of years to us for the star whale travels at as close to the speed of light as it is possible for an object with mass to get to it time passes very differently indeed making our sense of now a nonsense to the star whale all 13.8 billion years of the universe's history unfolds in a single quintilian of a second the entirety of human history happens in far less not even noticeable to its senses every war every invention every lost love and every laughing child gone in no time at [Music] all and as we'll see as we follow the story of this great creature the notion of now is not only highly mysterious but also wildly subjective and you don't need to be a giant Intergalactic whale to have an altered perception of [Music] it a car races down a road towards a flock of pigeons seemingly oblivious to the oncoming danger it looks through all the world like the birds will become one with the tarmac only for them to scatter at the very last moment why did they leave it so long the truth is they didn't our sense of now when theirs is different pigeons experience the world at over 100 frames per second as opposed to the 25 to 30 that films do it helps them keep track of fast moving insects so in the case of the onrushing car they simply have more time to react to it than it naively seems to you or I they experience the world in slow motion and so now can last longer or shorter depending on how you have evolved what you are doing and like the star whale in the most extreme cases how fast you are traveling indeed it is even possible for two people to see a series of Nows unfold in a completely different order human intuition is no yard stick for the way the universe really works and so as we journey with the star whale into the far distant Universe Giga anoms passing in the blink of an eye we are left with one big question what is now and does it even exist outside of our heads on Christmas Day 2021 millions of people around the world held their breath as the James web Space Telescope finally took off 6 months later the images began to be released in incredible detail with unprecedented quality this video has been sponsored by displate metal posters and they are a unique and stunning way to enjoy iconic images like the updated pillers of creation on your wall they are magnetic and take less than 20 seconds to mount indeed the mounting system includes a wall protective leaf that leaves no traces when removed they have posters for whatever your passion is movies gaming Comics Nature music anything from Real World science to iconic science fiction from their fantastic NASA collection with the Voyager spacecraft to Star Trek Voyager new brands and new collections are arriving every week and will be with you in four to 5 days both in Europe and the US yes they're already Great Value but you can get an even better deal using my Link at www.d displate.com hotu or my discount code H to access my special discount 22% off for up to two dis plates and then 33% off for three or more thanks to displate for supporting educational content on [Music] YouTube what does space taste like stars swirl in the void at dizzying speeds as the very fabric of time and space is tugged and stretched we are in the shadow of Sagittarius AAR the monstrous black hole at the heart of our Milky Way galaxy just 390 light years away from this dark heart an astronomical footstep lies a vast cloud of gas and dust known as Sagittarius B2 it's been the subject of much scr with astronomers pouring over its Ancient Light In Search for Clues to what lies within among the many ingredients they found there is a molecule known as ethyl formate it may sound unfamiliar but it's the same molecule that gives raspberries their distinctive flavor and so this begs the question what does space taste like does the star whale find some Celestial snacks more delicious than others and what about what space smells like well ethyl formate is also responsible for the smell of rum then there's the kickstarter campaign that's raised over half a million dollars to manufacture odor space a perfume based on astronauts accounts of the universe's distinctive odor think burnt meat burnt cakes spent gunpowder and the welding of metal but whatever the star whales culinary preference is it's still Bound by a nervous system just like you and I and the way your senses help you interpret the world around you has important consequences Brown notion of now you sit and watch as a carefully orchestrated ballet unfolds before you a penguin suited waiter pulls out a chair for a newly arrived guest as the semier buzzes with excitement while discussing the finest Bordeaux in the extensive wine list the white tablecloths are freshly ironed The Cutlery suitably weighty and the glassware reassuringly expensive shortly afterwards your first course arrives a delicate morsel lovingly crafted by a brigade of chefs with an imagination to rival the greatest painters you take a bite and your brain floods with endorphins it's your first taste of michelan starred food and in an instant you see what all the fuss is about except that it isn't really an instant at all when the food hits your tongue your taste buds register different tastes such as salty sweet sour bitter and Umami those signals travel along your cranial nerves to your brain stem which then passes them onto a part of your brain called the thalamus next they are shuffled to a small region right in the middle of your brain known as the gustat Tre cortex about the size of a grain of rice it is here that the taste signals are carefully decoded like a spy pouring over a secret Cipher but this race along your nervous system takes time the 2012 study led by Katherine Ola found that your brain typically registers The Taste 100 milliseconds after the food actually hits your tongue you are tasting a slice of the past not the present it gets even more complicated is not all tastes are interpreted by your brain equally Studies have shown that you often register sweet slightly before salty so you are in fact devouring a layered tapestry of distinct and separate culinary Nows this hectic temporal hodg Podge is true of all five of your senses when you picked up the cutlery and admired its weight those touch signals had to First travel from your fingertips to your brain in 2022 scientists at Caltech used a camera that could capture 70 trillion frames per second to record electrical pulses traveling at different speeds through different nerve cells the device relied on a similar technique to the one used by astronomers to measure gravitational waves from colliding black holes they found the touch signals travel at around 75 m/s to the brain that's faster than the world's quickest roller coaster but slower than the diving speed of a peragine falcon the world's fastest animal your brain then needs time to process the received signal this all means that when you first feel the knife it has already been in your hand for over 100 milliseconds once again you are sensing the past with your other senses there is an additional layer of delay as the information has to travel to reach your body before you ate the canopy you could smell how delicious it was going to be tiny molecules left the surface of the food and wafted through the air to your nose where they encountered nearly 400 olfactory receptors those receptors turned the chemical signal into a neural impulse which was then Express cour to your brain but how fast do smells travel as it turns out that's a complicated question it depends on many factors including the temperature of the food and the room what the food actually is and what the air currents in the room are like typically though it's in the region of a few hundred m/s so again we're looking at hundreds of milliseconds between the smell leaving the food and it registering in your brain you are never sniffing now only getting a a whiff of what the food used to smell like as your next course arrives the sky outside darkens and through the window you can see a fork of lightning rip towards the ground a Rumble of Thunder booms a few seconds later disturbing the delicate Serenity of the dining room it takes light just three microc seconds to travel 1 kilometer but it takes sound a full 3 seconds to C over the same distance this means you can easily work out how far away you are from the storm by simply counting the number of seconds between the flash of lightning and the crack of thunder each second of delay represents a distance of 330 M but whether you see the lightning hear the thunder or both you aren't perceiving a thunderstorm unfolding now you're seeing and hearing a thunderstorm that has already happened the further away you are the further back into the the past you are sensing your eyes and ears are time machines and this is the case with everything you [Music] see imagine looking in a mirror for you to see yourself staring back at you light has to hit your face and bounce into the mirror only then to be reflected back into your eyes the light that entered your eyes bounced off your face 2 NS ago so you aren't seeing yourself in the mirror as you are now but as you were 2 NS ago in reality it is actually slightly longer than that because your brain needs extra time to convert the light that falls onto your retina the back of your eye into an image of course a few slices of a second aren't going to change how you see yourself but imagine instead you saw a much younger you staring back when the distance that light has to travel becomes literally astronomical the effect becomes considerably more pronounced take the moon the closer this natural object to the Earth it sits some 384,000 seconds to cover that distance so we say that the Moon is 1.3 light seconds away when you gaze up at the beautiful full moon on a clear night you aren't seeing it as it is now but as it was the situation gets even odder if the moon is only half full look closely and you'll still be able to make out the other half of the Moon but it will be far more dimly lit the light from the bright half is sunlight directly reflecting off the lunar surface yet the dimmer light is Earth shine this is sunlight that is reflected off the Earth and then hit the moon only to be reflected back to us in a sense we are looking at ourselves in a giant Moon mirror if we could somehow fashion that light into an image we'd see our planet as it was over 2 and 1/ half seconds ago so each half of of a half lit Moon represents sunlight from a slightly different now the sunlight itself is actually even older as it takes just over 8 minutes to reach Earth from the surface of the Sun indeed if the sun were to suddenly disappear we wouldn't even know for 8 minutes while incredibly unlikely a similar Peril befalls anything or anyone traveling from Earth to Mars the average distance between the two planets is 225 million kilm that is 12 1/2 light minutes when a spacecraft carrying a Mars Rover hits the top of the Martian atmosphere it then takes 7 minutes to reach the surface so by the time emission control back on Earth gets the signal that The Descent has started the Rover is already safely on the surface or lying scattered in smoked out ruins future astronauts traveling to the red planet will face a similar predicament if an emergency unfolds halfway to Mars they would understandably need help now except their Now isn't the same as Mission controls it would take more than 6 minutes for their distress call to reach Earth and another 6 minutes for Mission control's response to arrive the fact that it's impossible for the two teams to sink up their Nows could well prove costly travel further out into the solar system and the delay extends to hours Voyager One the most distant human-made object is fast approaching being one light day from Earth by the time you reach the stars that twinkle away in the night sky the delay has jumped from days to years you aren't seeing the stars as they are now but as they were years decades and even centuries ago if you can find a star that is the same number of light years away as your age in years then the light entering your eyes has been traveling across the universe for the entirety of your life you are seeing the star as it was in the year that you were born the farthest star you can see with the naked eye is nestled away in the prominent w-shaped constellation of copia known as v762 cassia P it sits over 16,000 Li years away we are therefore seeing it as it was around the time when humans first domesticated dogs and let's flip the situation around any civiliz on a planet orbiting around v762 Casio PE would also see our sun and the solar system as it was 16,000 years ago with a big enough telescope they'd see the ghosts of people who've been dead for far longer than humans have been able to write the light that will bring them news of the ensuing revolutions Wars miraculous inventions and even YouTube videos is still surging towards them at 300,000 km/s a cascading succession of Nows tumbling through space at the speed of light v762 Casio PE may be the furthest star that you can see without binoculars or a telescope but it is not the furthest object in an adjacent constellation you'll find a fuzzy cotton wool likee smudge this is Andromeda the nearest major Galaxy to our own Milky Way near but not near for it sits some 2 and 1/2 million light years away in their version of now any aliens in Andromeda would only be able to see Earth as it was 2 and 1 half million years ago when one of our ancestors Australopithecus first started fashioning tools out of stone and the most extreme example of this is in the static you see when you turn on an old analog TV 1% of the black and white flickering received by your television is from the first light to stream in the universe nearly 13.8 billion years ago so our senses can clearly never deliver information to us instantly it always takes time and our subjective sense of now is affected by this delay but what about the universe beyond our bodies does the concept of now even exist in the universe at Large [Music] the star whale streaks across the night sky high above the planet Earth not that the cosmic satation has any concept of what a planet is according to Einstein's special theory of relativity traveling at exceptionally close to light speed means that the billion years history of a planet is condensed into the minutest fraction of a second special relativity allocates to any object moving through the universe a budget that is equal to the speed of light you can spend this Budget on a combination of two things speed and time the more you spend on speed the less you can spend on time the star whale is traveling so fast that its time spend barely registers and so the entire history of the earth flashes by unnoticed its now is stretched thin across Giga anms and so clearly there is no Universal now we all share but what does this mean for our day-to-day [Music] lives although far more famously associated with Albert Einstein the original theory of relativity is actually far older it dates back to the 17th century and the work of galile o galile to understand Galilean relativity picture a sailor standing on the deck of a ship they place a golf ball on a te swing their club and drive the ball off in front of the ship where it drops into the abyss now imagine that you're on the shoreline watching all of this unfold for one thing you would disagree with the sailor on the speed of the golf ball from your point of view the ball was already moving at the same speed as the ship before it was hit the swing of the sa's Club only increased the speed of the ball further the Sailor sees things differently however they were already moving at the same speed as the unhit ball and so we'll only see it move away from them as fast as they hit it in scenarios such as these each person's view is valid and neither is wrong it is all relative hence why it's called relativity crucially though according to Galileo F the Sailor timed how long the ball took to hit the water you'd get the same answer the time the ball is in Flight is equal to the distance it traveled divided by the speed it was traveling the lower speed the Sailor measures is offset by the fact that they also measure a shorter distance because the ship has moved forwards while the ball is in Flight in relativity each person's Viewpoint is known as a reference frame to convert from one person's reference frame to another you need to perform a transformation it's just a complicated way of saying that you you need to account for the fact that each Observer sees the golf ball traveling at a different speed Galilean Transformations worked well for over two centuries but by the mid 1800s cracks began to appear in 1865 the Scottish physicist James Clark Maxwell published the four equations that now bear his name Maxwell's equations describe light as an electromagnetic wave one that always travels at a fixed speed dubbed C from the Latin word Solarity meaning Swift or quick but if the speed of light is indeed constant that's incompatible with the concept of Galilean Transformations which take account of the different speeds measured by observers in different reference frames and so physicists searched for a way to extricate themselves from this existential Quagmire and in doing so they hit upon a rather strange notion the so-called luminiferous ether The Ether was proposed osed as the medium through which light waves travel after all sound waves wouldn't travel without air to propagate through perhaps light also needed a vessel to help vary it about if true The Ether would become an absolute and unique reference frame in which Maxwell's equations and the fixed speed of light hold in all other reference frames the apparent speed of light would be as variable as the speed of our golf ball and subject to the appropriate Galilean Transformations the only trouble was testing this idea that honor eventually fell to a pair of alliterative American physicists Albert mikkelson and Edward moley their aonomus 1887 experiment involved taking advantage of our planet's orbit around the Sun to test for the existence of The Ether the duo set up an intricate device known as a mikkelson interferometer it is effectively an elaborate racetrack a single beam of light is dispatched from the starting line and then split into two beams by half silvered mirror one beam continues on in a straight line the other is fired out at a right angle both beams travel the same distance to mirrors which reflect the beam's back to the Finishing Line as the distance that each beam travels is identical if one beam wins the race then it must have completed the course at a greater speed and that's exactly what you'd expect to happen if the ether exists Michelson and moley carefully set up the experiment so that the straight on beam lined up with the dire of the Earth's motion around the Sun the light traveling in that direction would be boosted by the speed of the earth just like the speed of the golf ball was boosted by the speed of the ship light traveling in the other direction would not receive such a boost and would be more sluggish as a result the Race Across the mikkelson Moy experiment would have a clear winner except the pair saw nothing of the sort both beams finished the race together two different reference frames one IM mutable speed of light the speed of light was [Music] absolute it took a while for the enormity of mikkelson and mle's result to sink in and one Dutch physicist thought particularly deeply about it hendrik Loren he would go on to win a Nobel Prize with the Nobel Foundation later remarking it may well be said that lorrence was regarded by all theoretical physicists as the world's leading Spirit who completed what was left unfinished by his predecessors and eventually Loren's name would become synonymous with the Transformations that would usurp galileos to understand the nature of Loren's Transformations first imagine a train moving at a constant speed along a track from left to right helpfully this train has completely see- through walls so that we can easily peer inside in the middle of the carriage there was somebody bouncing a ball up and down from their perspective that's exactly what happens the ball travels in a vertical line hand to floor to hand again but our view is somewhat different while the ball is in Flight we see the Train move further along the track the result is that we see the person catch the ball to the right of where they dropped it in other words we see the ball Trace out a triangle instead of a straight line there's nothing particularly strange about this after all it's just Galilean relativity we saw the ball travel a greater distance because we also saw the ball move faster due to factoring in the speed of the train but what if the person is replaced with mirrors and the ball with a beam of light exactly the same situation would play out at least at first a person on the train would see the light bounce straight up and down between the mirrors and we'd see the light Trace out the same triangle as the ball except this time we know from the and Moy experiment that the speed of light is fixed for all observers so we're no longer allowed to say that the person on the train measures a shorter distance because they measure light traveling at a slower speed and this leaves only one alternative one that initially appears so Preposterous that it cannot possibly be true if the person on the train measures a shorter distance it must be because from their point of view the light has been traveling for a shorter amount of time less time passes on the moving train than outside of it Len's work was incorporated by Albert Einstein into the special theory of relativity it tells us that two observers moving at different speeds disagree on how long something lasts because they are spending different amounts of their budget on time move through space at 99.999999% of the speed of light and what seems to you like a second will last almost two hours for someone back on Earth we could watch an entire football match in the time it takes for your heart to beat once our sense of now and yours are suddenly wildly different the difference between the two is calculated using the Lorent factor which Compares your speed to the speed of light its value does not rise in a straight line however but exponentially instead so you have to travel close to the speed of light for the difference to be noticeable travel at just 10% of light speed and the Len factor is only 1.5 100 seconds for you would last 100.5 seconds for someone who is stationary relative to you at 99% of light speed the Loren Factor Rises to just over 7 and from there every. n makes a massive difference travel at 99.9% of the speed of light and the theen factor is just over 23 at just one more. n to travel at 99.99 9% of the speed of light and it SES to more than 70 for the star whale traveling even closer to the speed of light the lorence factor is just over 7even trillion that's seven followed by 42 zeros the Loren factor is an important part of the Lorent Transformations that allow us to switch from our perspective to that of the star whale and gain an insight into its unique existence yet for all the peculiarities of the star whale the there is a creature that inhabits this universe with an even more bizarre existence the [Music] photon the photon is a particle of light and for it time simply does not exist the Loren Factor equation breaks down and the answer becomes what a mathematician would call undefined as a result from a photon's perspective it gets from A to B in an instant and the idea of one now ebbing away into another is meaningless and if this wasn't strange enough for those of us who are moving slowly enough to experience the notion of now it's even possible for our Nows to get out of syn for two observers to disagree on which now came first let's return to our moving train The Carriage is midway between two trees that are both hit by a bolt of lightning from our perspective the bolts hit the trees simultaneously but does the person on the train agree you've guessed it they don't they are moving towards one tree so see that flash first The Flash from the tree they are fleeing from takes longer to catch up however according to the appropriate Lorent Transformations how much two observers now get out of sync depends both on their speeds and the space between the events you'd have to be traveling at half the speed of light and the separation would have to be greater than the the gap between the Earth and the moon for two events to drift by just one second but there is an important caveat to all of this causality must always be preserved if event a causes event B to happen then it will appear that way in all reference frames two observers might disagree on the time interval between the events but not the order in which they happened this notion is a central tenet of the Lorent Transformations and special relativity according to the equation seeing effect happening before cause would only be possible if you could travel faster than the speed of light and that is impossible so where does all of this leave our sense of now it seems the subjective now is all we have both inside our heads and in The Wider universe everything is relative there is no objective now but does that make mean there is no way of definitively telling the time in The Wider Universe not quite thankfully there is an invisible arrow pointing the [Music] way gigantic spiral arms unwind as stars scatter like pigeons into the darkness planets are slung out to one w space alone as solar systems grow cold and ancient civilizations grow fearful the star whale has just laid waste to another Prime section of cosmic real estate the destruction it leaves in its wake progresses steadily across Cosmic distances shattering galaxies in glacial slow motion to our eyes it is a truly bizarre thing to witness this gargantuan breakdown of order but despite its strangeness it does have happen in order one event follows another chaos is the effect the star whale the cause and so why is it that our Nows always unfold in that order why aren't they simply a jumbled scattering of distinct moments what is the chain upon which they hang our journey towards the answer begins in California in 1874 the courtroom Falls silent as the foreman of the jury Rises to his feet how do you find the defendant not guilty comes the reply accompanied by a gasp that spreads around the room like falling dominoes Edward mybridge has gotten away with murder born in England in 1830 mybridge immigrated to the United States age 20 then in 1872 aged 42 he married 21-year-old Flora Stone and the couple had a son 2 years later or did they one day mybridge discovers a series of letters between flora and a major Harry Lins there's even a photo of her son captioned little Harry mybridge is incensed and shoots Lins through the heart when arrested he first pleads insanity but later changes his defense to justifiable homicide the jury will later acquit him on exactly those grounds today mybridge surely would have gone to jail but that he didn't had a huge effect on our understanding of the true nature of now for mybridge was a keen photographer and he was about to Pioneer an important new technique chronophotography the photography of time it involved capturing a series of still photographs that show successive phases in an object's Motion in other words it records the apparent passage of time as one now drifts into the next the most famous of my brid's works is the horse in motion by quickly flicking through the still images one at a time you can see the Horse and Rider at full Gallop it was revolutionary revealing for the first time that at one stage all four of the hores hooves are off the ground chronophotography was the Forerunner of the modern motion picture but what looks like motion is really just the result of comparing ing one still frame to the last when you view the images the horse isn't really moving time isn't really flowing either it is the change we see between frames between Nows that gives us the illusion of time passing or flowing like a river from the past to the present we are caught in an imaginary current except there is nothing in the laws of motion famously set out by Isaac Newton that describes the preferred direction to time that we experience let's imagine that instead of a horse Galloping we watch a succession of chronophotography through the air from left to right here is the very same set of still images but played in Reverse nothing looks particularly out of place I could likely convince you that the first film was the one that was backwards and I deliberately misled you there's no way you'd know the truth yet there are some films that you would know instantly if you were being played play them in Reverse perhaps one that shows a broken egg miraculously reforming or an initially cold cup of coffee suddenly starting to steam this is such a fundamental part of our existence that given the individual Stills a small child could likely place them in the correct order showing an intact egg breaking for these events time does not appear to be reversible it's like there is an arrow pointing us in a particular direction telling us the order to put the Nows in [Music] it was the English astronomer Sir Arthur Edington who first referred to times arrow in his 1928 book the nature of the physical world if as we Follow the arrow we find more and more of the random elements in the state of the world then the arrow is pointing towards the future Edington wrote If the random element decreases the arrow points towards the past that is the only distinction known to physics but what exactly does Randomness have to do with time and the apparent order in which events unfold follow the river sen out of the ancient Parisian streets and you'll eventually roll into the industrial suburb of i s sen enter the local cemetery and towards its northern end you'll find a gravestone bearing the name of one Leonard Sardi Caro further down on the stone AR the word F de thermodynamic founder of thermodynamics the tale of sardo is a tragic one he died in 1832 at the tender age of just 36 he'd recently been committed to the local Asylum and wound up succumbing to a color outbreak as a result understandably his work received very little attention at the time it is only since then that we realized what a towering figure he was and the consequences of his work for our understanding understanding of the ephemeral nature of now today Caro's name is synonymous with the Caro cycle which describes an idealized heat engine except that it is impossible to operate a Carno engine in real life still to this day Engineers measure the Caro efficiency of their engines how close they can get to this unrealizable Perfection one man who thought about the consequences of carno's work in great detail was Rudolph clous in 1850 he published the basic ideas that now constitute the famous second law of Thermodynamics and in 1865 he introduced the world to the concept of entropy the entropy of the universe tends to a maximum he [Music] said one way to think about entropy is as a measure of the amount of energy that is unavailable for doing something useful clausius showed that the energy loss to the surrounding environment during a cycle of the engine is larger than the energy transferred to the engine by the heat source so overall the energy that's unavailable for doing something useful goes up in other words the entropy increases perhaps a more intuitive way of thinking about entropy is as a measure of disorder the randomness discussed by Edington let's imagine six coins all initially showing heads this is a highly ordered low entropy system you then toss all the coins there's nothing stopping them all being heads again but the chances are very low in fact you could try it 64 times and it will probably only happen once on the other occasions the coins are likely to become more random a mixture of heads and tails the disorder or entropy has increased and when it comes to the world around us the odds are even more heavy stacked in favor of an entropy increase imagine an empty box the size of a sugar cube floating in front of your face it isn't really empty though because it is full of air molecules a lot of air molecules there are more molecules in a cubic centimeter of air than there are stars in tens of millions of galaxies like our own Milky Way as the gas molecules Jive and jostle about randomly there are Myriad ways that they can become more disordered but only a limited number of ways that they can become more ordered the chances of those more orderly outcomes occurring are so low that you'd have to wait for longer than the current age of the universe to see them so we never do we always see order eing away into disorder and that's what produces edington's Arrow of time it is this that allows us to reliably put the NeverEnding jumble of Nows in order except when we look at the universe around us there are many islands of order amidst the growing ocean of disorder searingly bright stars in swirling galaxies strung out in clusters like fairy lights along a cosmic electrical cord then there's you you are a highly ordered collection of around a billion billion billion atoms for you to exist some 13.8 billion years after the birth of the universe in a big bang the entropy of the universe must have been incredibly low to start with otherwise the universe's tendency towards ever increasing disorder would have reigned on biology's Parade long before now indeed astronomers estimate that the entropy of the early Universe was a quadrillion times less than it is today how could such a situation have come about one man thinks he knows the answer his name is Julian Barber Barber is an anacronismo age there was a time when the greatest discoveries in science were made by gentleman scientists those with the wealth means and time to pursue the Quest for knowledge as a hobby today you usually have to tread the well-worn path of Academia and work in a university Bara is one of a handful of independent scientists and has been obsessed with time for a long time his answer to why it only appears to move forwards is that it does so only in this part part of the universe He suggests there is another part of the universe where the arrow of time points in the other direction through the Looking Glass world where yesterday happens after today the two parts of the universe are separated by what barar calls the Janus point after the god with two faces who could look both ways it marks not the beginning of the universe but its midpoint time symmetric Across the Universe with no mysterious low entropy state to begin with but Barber's idea is simply that a suggestion and one of many we still don't really know what caused the incredibly low entropy the universe began with universal times steady March still a mystery we haven't fully unwrapped but that isn't the end of the Mysteries shadowing our experience of the present having considered how we sense time the intricacies of special relativity and finally large scale entropic time the gradual crumbling of entire Galaxy's entire universes we can now return to the bizarre world inside our heads the brain our time processing center and it turns out that is where the situation is most [Music] complex the star whale lays stricken beached on some distant Cosmic Shore there have been no stars in the universe for eons all when Supernova and vanished long ago all atoms in the universe have split apart just how the star whale has made it this far remains a mystery no one has ever known what it's made of now even the most super massive of black holes are evaporating oozing the last of their Hawking radiation in into the cosmos there is nothing left despite each of its Nows lasting for billions of years it is seen more Nows than any creature in history starving the star whales eyes close for the final time and as the last Consciousness in the universe is extinguished does time itself still go on or does time die with the mind many of us are prisoners to the clock enslaved to the Relentless passing of the seconds time often seems to drain through our fingers like we are trying to hold a puddle of water it's slippery evasive transient yet how often do you spend time actually thinking about time do you ever wonder how your brain constructs a sense of time from the Deluge of information it perceives about the world around you the uncomfortable truth is that your brain is lying to you take a look at this clock at first the seconds seemed to tick by at regular intervals now Dart your eyes away from the screen and quickly look back at the clock again did the first movement of the second hand linger a little longer than the ones that followed as if the clock had momentarily stopped your eyes are constantly flitting about zipping from one object to another it could be a small adjustment as you read a book line by line or a big one if you suddenly gaze towards the other side of the room these movements are known as cards curiously though despite the fact that your eyes are moving your vision never blurs instead your brain deletes the images from when your eyes are in motion and back fills that Gap with the first thing your eyes land on after the sard and so in the case of the clock that's the first tick this effect is known as the stopped clocker I usion try looking at yourself in a mirror and shifting your focus from one eye to the other can you see your own eyes [Music] move the sliver of time your brain deletes during a sard is Tiny typically less than 100 milliseconds and yet your eyes perform so many sards over the course of a day that you lose out on a total of 40 minutes worth of Nows that's almost 20,000 hours of deleted Nows over an 80-year life lifetime more than 2 years of fake backfill Nows replace them and it gets worse take a look at this moving Square did the flash occur behind the moving Square directly beneath it or further ahead than it did you answer behind it wrong The Flash occurred directly beneath the moving Square this is known as The Flash lag illusion and it is the key to understanding another piece of the puzzle surrounding how your brain constructs a sense of now it takes time for your brain to process the visual information it receives about an object in front of you color is processed first followed by motion and then finally shape except by the time your brain has processed all of that the object has already moved on to a new location so your brain could not tell you for certain where the moving object is now instead it shows you its best guess as to where the object should be as the flash like illusion shows that guess is not always accurate that being said your brain does do a fairly good job if the motion of the object is predictable a baseball player can still hit a fast moving pitch into the stands and a goalkeeper in a football game can still tip a curling free kick over the crossbar and yet the brain does a considerably worse job when the motion of the object is more random imagine a fly buzzing around the room haphazardly darting this way and that your brain struggles to keep track and ends up showing you the fly in positions that it never actually occupied a completely imaginary now this inforced fiction is one of the reasons that swatting a fly tends to best us like Don kote we are tilting at windmills we have such a sense that what we see is real that it's hard to shake that feeling and yet our brains are the ult at storytellers telling us a tale constructed from all the inputs it is constantly being bombarded with our sense of the present moment is a fantasy just one interpretation of the world laid out before us but how long does now last in the brain one way to answer this question is looking at so-called by stable images and one of the most famous examples is known as schroer stairs after the 19th century German scientist Heinrich schroer at first glance it appears to be an ordinary staircase with steps descending from left to right that is until you start to stare at the back wall labeled B suddenly you can see the staircase flip upside down except it is very hard to hold on to this inverted view for long within a few seconds it will revert back to the conventional staircase again hence the term by stable this seems to suggest that now when the brain lasts for 2 or 3 seconds after that the brain takes a new set of sensory inputs and constructs the next coherent moment psychologists and neuroscientists refer to this time period as the subjective present scientists have conducted various studies in an attempt to explore this concept one looked at repetitive behaviors across different cultures around the world such as chopping rubbing or wiping the most common duration of each repetitive action was between 2 and 3 seconds the person could well be thinking I am chopping it now and I am chopping it again now one motion equals one [Music] moment scientists also refer to this 2 to 3 second snapshot of our world as our temporal integration window it's the time period over which we can successfully bring information together in a coherent way a duration of 2 to 3 seconds was supported in 2014 by an interesting study conducted by Scott farhall Angela Alby and David meler they showed participants 12.8 second long clips from obscure International movies with the sound removed crucially they also split each clip into chunks and scrambled the frames within each chunk so that the participants saw the story unfold out of order so what happened participants had no trouble keeping track of the story if the chunks were less than 2 second seconds long that ability then began to drop off and become markedly harder by 2.8 seconds in other words our brain can construct a coherent version of now in bursts of under 3 seconds any longer and there's just too much information to knit together into a single moment so we reset and go again our sense of time passing is just the result of comparing the current moment to the last with time arrow pointing the way and so if our sense of now is only a construct of the 3 PB worth of mushy gray matter between our ears where exactly in the brain does it all unfold that is still largely a mystery after all we have no temporal sensory organ we can't taste time or feel its texture so our sense of it doesn't light up on an MRI scan in the same way that our five conventional senses do our sense of time is also affected by a emotion time flies when we're having fun and crawls like a sloth when we're not there's a part of the brain called the insul CeX that deals with how we feel and our self-awareness it's been linked to our sense of compassion empathy and disgust to our pain hunger and even our orgasms in other words it is the seat of our deepest and most profound emotions to explore the link between the insular cortex now sense of time psychologist Mark Witman put participants in an fmri machine and asked them to press a button when a sound they were being played matched the duration of a sound they heard previously the insular cortex was reliably activated in those that could accurately time the sounds and so if the insular cortex really is responsible it would explain why our sense of time is so tied up with how we feel both are controlled by the same region right at the heart of the brain it just goes to show that time and our experience of it are both incredibly Troublesome Notions to deal with our senses meld information arriving to our bodies at different times to construct each perceived moment with a significant delay and our brain even delet Snippets of time to help us make sense of the world around us time itself can proceed at different rates depending on how fast we are traveling a speed that can also lead us to disagreeing on the order in which certain events unfold and it's not even clear why time began at the beginning of the universe with the direction that it has from the past to the Future and yet though the present moment may not be real just a fiction created within our remarkable brains without our minds convincing us that it is we couldn't be here now talking about whether now [Music] exists you've been watching the entire history of the universe don't forget to like And subscribe and leave us a comment to tell us what you think thanks for watching I will see you next [Music] time
