Brian Greene on The B-Theory of Time

once upon a time that magical phrase at the beginning of every good story but what is the story of time people say that time flies that time is money we waste time we kill time we try to save time but what do we really know about time well like this River time seems to flow endlessly from one moment to the next and the flow of time seems to always be in one direction toward the future but that may not be right discoveries over the last century have shown that much of what we think about time may be nothing more than an illusion contrary to everyday experience time may not flow at all our past may not be gone our future may already exist it turns out time itself can speed up or slow down an events that we think can unfold in only one direction and also unfold in Reverse but how could this be how could we be so wrong about something so familiar and if time isn't what we all think it is then what is it did it have a beginning will it have an end where did it come from most people view time in a pretty simple straightforward way time ticks the same for everyone everywhere it's a common-sense picture established by the father of modern science Isaac Newton's time for Isaac Newton is something that is an immutable property of the universe time always changes at the same rate time just goes along and there's really nothing we can do about it sensible as Newton's picture of time may seem I'm Stein realized it wasn't right he discovered that time could run at different rates strange as it sounds this means that time for me may not be the same as time for you Einstein's discovery smashed Newton's conception of reality before Einstein our understanding of time was basically due to Newton and it aligned with our intuition time in the mathematics of Newton is pretty much time as we experience it when Einstein came along that all changed Einstein came up with a number of theories the first the special theory of relativity he developed in 1905 and what perhaps is best described as a hurricane of intellectual fervor in the spring of 1905 where he was struggling to understand aspects of space and time unlike what Newton said Newton said that space is an absolute eternal unchanging stage in which the events of the universe take place and he said that time is something that's also universal it's something that ticks forward second after second in a completely uniform absolute way time for you is the same for time for me is the same for time on Jupiter or the Andromeda galaxy Einstein realized that that isn't true in the Newtonian picture there is a grandmaster clock that defines notion of time that applies throughout the universe Einstein obliterates that idea there is no grand cosmic clock that is the ultimate arbiter of what time it really is time is in the eye of the beholder different people moving relative to one another experiencing different gravitational fields they each have a notion of time that's perfectly valid but generally completely different from the time that anybody else is watching a lapse on their watch Einstein came to the shocking revelation by uncovering a hidden connection between space and time but Einstein figured out is that there's a profound link between motion through space and the passage of time roughly speaking the more you have one less you have of the other to see how this works let's take a little ride right now I'm heading due north at 60 miles an hour and that means all my motion is in the northward direction but let's now turn onto a different road and head Northwest I'm still going 60 miles an hour but I'm not making as much progress toward the north as I was a minute ago and that's because some of my northward motion has been diverted or shared with my westward motion Einstein realized that time and space are linked in much the same way that North and West are and with this surprising insight Einstein would overthrow the common sense idea that time takes the same for everyone here's what I mean that guy over there to say that I'm not moving at all but I am I may not be moving through space but I am moving through time I mean after all my watch just keeps on ticking and ticking and as long as I'm standing still that is not moving through space Einstein said that all of my motion is through time but look what happens if I walk toward that guy we've exaggerated it but because I'm now in motion he'll perceive my watch ticking slower that's because from his perspective some of my previous motion through time is being diverted into my motion through space and it's not just my watch if we really exaggerate the effect he's perceived all my movement my voice everything about me slowing down and now that I've stopped moving the passage of time owner watches once again agrees this was Einstein's key insight that motion through space affects the passage of time the special theory of relativity was developed by Albert Einstein in the spring of 1905 in the space of perhaps five intense weeks of thought where he rewrote our understanding of space and time Newton had given us an understanding of space and time back in the late 1600s which is very intuitive it's the way we all think about space and time here is space it's just this environment where things happen and time is this relentless thing that ticks forward on our watches our clocks taking us moment after moment second after second into the future in a completely uniform absolute and unchanging way in special relativity Einstein said that's not right he said space and time can change depending upon how you move he showed that if you're moving relative to somebody else time for you slows down Einstein was the master of what we usually call the thought experiment he didn't go out into the world and actually do experiments where he would measure things and try to determine how a given experiment would turn out instead he would sit more or less at a desk or work at a blackboard and through the power of thought recognize that there were certain puzzles that needed to be resolved and the one that really was vital to his understanding of special relativity as this he recognized that previous work that came to him from the late 1800s works of someone named James Clark Maxwell that work showed that the speed of light seemed to be constant that it seemed to be unalterable now many people struggle with that how could the speed of something be unalterable and you take a baseball you can change its speed you throw it fast you threw it slow it can go at different rates why would light have a fixed speed Einstein took that little puzzle very seriously and realize well if speed is a measure of how far something goes space it covers divided by how long it takes to get there a duration of time he realized that if speed was constant for light then space and time had to adjust themselves in order that speed stayed fixed space and time had to behave in a way that was unfamiliar I'm gonna thought that through in detail he realized that space can shrink and time can dilate depending upon how you're moving and that's how he came to these rather shocking realizations about space and time as you move time for you slows down relative to somebody who is watching you that is not moving with you time is relative space is relative if I'm watching you speed by me you look shrunken in space compared to how you would look if you weren't moving motion affects time motion affects space a completely new understanding of these very basic entities that since the time of Newton we thought were absolute and unchanging they're not their relative and they are changing and these kinds of revolutionary ideas are not simply esoteric pen and paper type understandings of the universe you can take a little particle called a muon which if it's sitting in front of you will self-destruct in about a millionth of a second it will fall apart you take that particle and you make it go fast in one of these particle accelerators it zips around near the speed of light because it's moving time for it slows down it doesn't just live for a millionth of a second it lives for a second or longer a million times longer than it would if it was sitting in front of you if you could put a person in one of these accelerators they wouldn't live 80 years they might live 80 million years as we're watching them because time for them slows down so why don't we ever see this in everyday life well at the slow speeds we move here on earth motions impact on time is so tiny we don't experience it but the effect is real and can be measured to do this all you need are a couple of atomic clocks and a jet airplane and this experiment was carried out in 1971 when scientists flew an atomic clock around the world and then compared it to one on the ground as Einstein predicted the two clocks no longer agree they differed by only a few hundred billions of a second but that was very real proof motions effect on the passage of time Einstein's theory has been tested again and again and again and all hangs together it really forms the basis for the way we understand much of the way nature works these effects which used to be considered sort of obscure and very small or very in-your-face with today's technology with the discovery of this unexpected link between space and time Einstein realized that the two could no longer be thought of as separate things instead space and time are fused together and what came to be called space-time Einstein unified the idea of space with an idea of time into this four dimensional structure called space-time normally when we think about space or time in the conventional Newtonian classical intuitive perspective we view them as two completely separate things space is the environment where things take place time is the marker of duration it measures the duration over which a given kind of change takes place separate ideas but with Einstein we learned that space and time are not separate they are profoundly connected and that's what this notion of the melding together comes from and you see that in relativity because for instance if you get up and start to move through space Einstein shows that your motion through space affects how quickly you age it affects your passage through time who would have ever thought that whywould motion through space effect - anything to do with time but with Einstein and relativity the melding together of space and time which he established shows that indeed that's the case move through space it affects your passage through time space and time are not separate they are intimately connected and to reflect that intimate connection a new term was coined space-time which linguistically puts space and time together in much the same way that Einstein physically put space and time together with special relativity and this fusion of space and time would lead Einstein to perhaps the most mind-bending realization of all the sharp difference we see between past present and future may only be an illusion when Einstein came along with the special theory of relativity he showed that past present and future that kind of way of dividing up our understanding of time that isn't as fundamental as you would think it is in our day-to-day lives we experience time as a continuous flow but it can also be useful to think of time as a series of snapshots or moments and everything that happens can be thought of as the unfolding of moment after moment after moment and if we picture all moments or snapshots lined up every moment here on earth every moment of Earth orbiting the Sun and every moment throughout the entire universe we would see every event that has ever happened or will ever happen every location in space and each and every moment in time from the birth of our universe at the Big Bang some 14 billion years ago to the formation of stars in the Milky Way galaxy to the creation of Earth four-and-a-half billion years ago to the time of the dinosaurs two events happening on earth today like me working in my office thinking about space-time like this that is time to overturn our everyday picture of past present and future to get a feel for this you have to think about the seemingly simple concept of now for me a list of things that I consider to be happening right now might include the tick of noon on my office clock my catch just now jumping from the windowsill things happening far away like a pigeon in Venice taking flight at this very moment a meteor just now hitting the moon an explosion of a star at the far reaches of the universe these and all other events that I think are happening at the same moment in time but in different regions of our universe make up what I intuitively think of as now you can picture them as lying on a single slice of space-time let's call it a now slice common sense would say that you and I and everyone else will agree on what's happening work what exists right now moment after moment after moment that is we would all agree on what lies and a given now slice but Einstein showed that strangely when you take motion into account this common-sense picture of time goes out the window you see what I mean think of space-time as a loaf of bread Einstein realized that just as there are different ways to cut a loaf of bread into individual slices there are different ways to cut space-time into individual now slices that is because motion affects the passage of time someone who's moving will have a different conception of what's happening right now and so they'll cut the loaf into different now slices their slices will be at a different angle that person who's moving look will tilt the knife will be carving out these slices at a different angle they won't be parallel to my slices of time to get a feel for the bizarre effect this can have imagine an alien here in a galaxy 10 billion light-years from Earth and way over there on earth the guy at the gas station now if the two are sitting still not moving in relation to one another their clocks tick off time at the same rate and so they share the same now slices which cut straight across the loaf but watch what happens if the alien hops on his back and rides directly away from Earth since motion slows the passage of time their clocks will no longer take off time at the same rate and if their clocks no longer agree there now slices will no longer agree either the aliens now slice cut through the loaf differently it's angled toward the past since the alien is biking at a leisurely pace his slice is angled to the past by only a miniscule amount but across such a vast distance that tiny angle results in a huge difference in time so what the alien would find on his angled now slice what he considers is happening right now on earth no longer includes our friend at the gas station or even 40 years earlier when our friend was a baby amazingly the aliens now slice has swept back through 200 years of Earth history and now includes events that we consider part of the distant past like Beethoven finishing the fifth symphony even at a relatively slow speed we can have actually tremendous disagreements on our labeling of now what happens at the same time if we're spread out far enough ahead space and if that's not strange enough the direction you move makes a difference to watch what happens when the alien turns around and bikes toward Earth the aliens knew now slice is angled toward the future and so it includes events that won't happen on earth for 200 years perhaps our friends great-great-great-granddaughter teleporting from Paris to New York different observers in the world moving with respect to one another different speeds won't agree on what is past present and future what's past for me might be future for someone else what's present for me might be past for someone else so when you take it all together past present and future are not a kind of demarcation that's universal once we know that your now can be what I consider the past or your now can be what I consider the future and your now is every bit as valid as mine now then we learn that the past must be real the future must be real they could be your now that means past present future all equally real they all exist before Einstein the thought was everyone agrees on what's past everyone agrees on what's happening now and everyone agrees on what hasn't yet happened the future but that's not true one of the most surprising insights from Einstein is that time is not what we intuitively think it is right most of us have this sense that time for you is the same as time for me in some sense there's this cosmic clock that's out there ticking second after second after second dragging us all in exactly the same way into the future Einstein found that if you and I are moving relative to each other however our clocks don't take off time at the same rate our watches if they were once in sync if we're moving relative to each other they fall out of synchronization now what does that mean well that means that what I consider to be happening right now at a given moment from your perspective that might be the past or it might be the future what you consider to be happening right now to me that maybe the past or the future now since your view of reality is every bit as valid as my of reality that means you can't really say the past is gone because that might be your now your reality you can't really say the futures yet to be maybe the future to me it might be your now your reality at that given moment so in a sense past present and future are all equally real they all exist they're all out there so what this collectively tells us is that the traditional way that we think about reality the present is real the past is gone the future is yet to be that is without any real basis in physics what we're really learning from these ideas is that the past the present and the future are all equally real if you believe the laws of physics there's just as much reality to the future in the past as there is to the present moment the past is not gone and the future isn't non-existent past the future and the present are all existing in exactly the same way any given individual can certainly speak of their past or their present or their future the key realization of relativity is that they are really speaking only for themselves if there are other individuals that are in the world and there are who are moving at different rates who are spending time near a black hole for instance then their conception of past present and future won't agree with any given other individuals conception of past present and future that's the real break the interesting thing which Einstein in a very poetic way captured is that if you really take the ideas of time from physics very seriously then it's not as though the past is gone the past in some sense will always be its eternal and Static and what that means is that the way in which we typically view life past is gone futures yet to be that needs to be jettisoned from our thinking as Einstein said the distinction between past present and future is only an illusion however persistent which in a sense means that when we live we live forever at the moment where we existed not that we live for all of time but when we do live the interval during which we lived that's always there just as we think of all of space as being out there we should think of all of time as being out there to everything that has ever happened or will happen it all exists from Leonardo da Vinci laying the final brushstroke on the Mona Lisa to the signing of the Declaration of Independence to your first day at school two events that from our perspective are yet to happen like the first humans landing on Mars with this bold insight Einstein shattered one of the most basic concepts of how we experience time the distinction between past present and future he once said is only an illusion however persistent Einstein summarized this to the widow of a close friend of his by trying to console her by saying that past present and future that's only an illusion however persistent but if every moment in time already exists then how do we explain the very real feeling that time like this river seems to endlessly rush forward well maybe we've been deceived and time does not flow perhaps the river of time is more like a frozen river with every moment forever locked in place the most vivid example about the way the world is has to do with this flow of time physics does radical violence to this everyday experience of time our entire experience of time is constantly in the present and all we ever grasp is that instant moment there is nothing in the laws of physics that picks that one now over any other now and it's just from our subjective viewpoints that it feels like things are changing just the way an entire movie exists on a reel of celluloid think of all moments of time as already existing - one of the most basic human experiences is the flow of time right we all have the sensation that we're all kind of on a river of time that's taking us from moment to moment to moment endlessly rushing forward toward the future however common that experience may be I have that experience that's how I think about time and everyday life but when we look at the equations of physics we don't find any evidence for a flow of time all we find in the equations of physics is that there's moment after moment after moment but there's no sense in which those moments flow into each other it's as if that river of time is more like a frozen river where every moment is forever locked into one location and it's just out there all of time being out there it's as if you know none of us have a problem with the idea of all of space being out there we can picture that in our minds I all of space out there this way of thinking about time suggests that we should also think that all of time is out there - well we've all experienced as the flow of time really maybe nothing more than an illusion the time that we seem to experience as a continuous flow is actually not a flow at all in other words I've always spoken on the radio and I always will speak on the radio each moment just exists you will always be listening eternally if you will you always have been listening it's not that the moment comes to life at one moment in time that we call the present and then somehow drifts away into the past every moment is and is forever but you understand that concept do you understand the concept that's too weird it's a tough idea let me just make it even tougher okay imagine if I go and just hold my breath that moment which I just thought up I think that moment could last in Brian's world forever have you exhaled yet no and the exhale could last forever somewhere you're always inhaling and somewhere you will be forever exhaling this very very strange notion the moments are they just exist and somehow it's the human mind in each moment that makes each moment seem real December 31st 1999 I was at a New Year's party and according to this way of thinking but I'll always be at that New Year's party because that moment is it exists it's not that it somehow goes away my mind seems to organize things into moments that are gone in moments that have yet to be but I think that's my mind organizing things I don't think that's how though universe is put together the moments just are but look where that leaves us that leaves us with everything that you've done in your life exists already yeah everything yeah you're beginning your middle and your end every moment of time is out there your dot your dead somewhere you're almost dead somewhere yes there's no special now you're saying to me that there is no time as I understand it no time every moment of your life is already there eternally frozen every moment of my life is frozen every moment of my children's life is frozen and every moment of my great-great-great-great grandchildren's lives are already there and frozen and so the universe is a vast collection of nows now that's right I just pawned everything I believe to be reality wasn't reality of it wasn't reality at all you

Channel: Zehadi Alam

Views: 806,743

Rating: 4.6668096 out of 5

Keywords: Brian Greene, Nova, The Illusion of Time, The Fabric of the Cosmos, Time, philosophy, Max Tegmark, David Albert, James Gates Jr., Dimension, spacetime, Albert Einstein, special theory of relativity, space, gravity, flow of time, eternalism, presentism, philosophy of time, World Science U, World Science Festival, Isaac Newton, classical physics, Newtonian physics, mechanistic, Sean Carroll, arrow of time, river of time, past, present, future, determinism, block universe

Id: H1WfFkp4puw

Length: 32min 42sec (1962 seconds)

Published: Sat May 03 2014

Reddit Comments

[u/JesusAndFriends]

I know right? Its all just one big smear of everything at once... oddly enough the "True Detective" plot touches on this.