Welcome to everybody my name is Jeffrey West and I'm on the Faculty of the Santa Fe Institute and it's my real Honor and Distinction To Better Introduce [Wonderful] Speaker Tonight Leonard Susskind I'Ve Known lenny for more Years and I care to think Probably and Likewise no doubt And well [I'll] respond to that in A moment [so] uh you know, We we tried very hard to bring? Provocative Challenging Thinkers That Are Kind of you know Pushing the frontiers and Working on the Edge and There are very Few Thinkers in Today's World More on the Edge in More Ways Than one Probably than our Speaker Tonight Lenny is A distinguished Theoretical Physicist Who has Made Numeral Fundamental Contributions to the Field of Fundamental Physics May Be identified as a high Energy Physicist Or an Elementary Particle Physicist or? Just A fundamental Physical Physicist Working on Fundamental Issues In Physics Conceptual Issues and Tonight's Subject is Obviously Quintessentially One of Those and Lenny is Maybe Best Known of all the Many things that he has Done Because it's sort of in the public eye for on the One Hand being one of the Inventors so to Speak of string Theory the idea that the Fundamental Forces The Fundamental Objects so to Speak of Nature Are Not Little Newtonian Like Point Particles but Are more Little Vibrating strings and Everything Around [us] comes from The Geometry and Dynamics of the Vibrational Modes of Those strings and the Way They Interact and so He, was one of the Founders of that whole Idea and has Been Instrumental in developing it? [but], also he's Known for a dispute that he Had With Stephen Hawking About The Role of Information and Black holes that the idea the black [hole] Swallow everything up Including all Information This was a major dispute Which Lasted Five Hundred Twenty Years Probably in Which Lenny Eventually, was declared the Winner [and] This is no mean achievement and indeed [Len] Lenny Wrote a popular Book On the subject for Which I think you got a prize for that One Actually a Book Prize for that so he's not only Delved Into the depths and Fundamentals of Physics But He's, also been a Popular writer and written Best-Selling science Books Into The Bargain so as I said I've Known lenny for A very Long Time for Probably 40 [Years] and One of our Disputes Mini Disputes Is to do with Time because every Time we meet haha, Every Time We meet Lenny Think that I'm older [Than] he He Knows at the Beginning he Knows that in That when, We first met That he, was? He what he I was Younger Than he and so he has it as you will See tonight [are] very Interesting Ideas About the Concepts of Time That Somehow So, we had Breakfast A week or so ago with our Two? Delightful beautiful Wives with Us in Palo Alto And it Came [Up] again but I did Discover [that] A week or so ago lineage as linda's Birthday so happy Many, Happy returns and I'd like to and Lenny is Now 73 [I] of Course [Have] only 72 so Having Said That I'Ve Known Lenny A long Time and I think you're in For A good Show tonight and Certainly Something that Is going to be very mind Changing and As well as no doubt entertaining as I said we've known each other we done Some? Adolescent Things Together We were Thrown [out] of A bar Together and I? Guess it was Miami when I'm in Coral gables Anyway There was A famous Meeting in Coral Gables? Every Year on some of These Fundamental Areas and We went to [and] he Reminded Me in Set 1975 is the Time? We were Thrown out of A bar it May Be in the Same year that he undressed at a Dinner Party Around a pool And i Say and and Everybody Thought he, was going to be in his underwear but he, was Actually nice ooh, [ah]? He, also A often Claims and I did the Same Thing [but] I'm British Whereas he's From the South Bronx and I'm going to finish Up With Something he Told me Today that I didn't know about him Is that his Name isn't Leonard Lenny Lenny's first Job so to Speak was as a plumber he, was trained as a Plumber by his Father and his Father Was had Great Admiration for Leonardo As an Engineer and Named his son Leonardo so he has an unusual Name May i Say For A jewish Boy [from] the South Bronx Leonardo Susskind and [Burt] Lenny went to City College And as an Undergraduate and was a graduate Student of Cornell Under A man Named Peter Crothers who, also Influenced Me in some Stage [of] my Career and then Was a taught at Yeshiva University in New York [for] several Years before Moving I guess it must have Been Late 70s Maybe Around 8 1980 I don't remember Exactly to Stanford and has Had a glorious Career and Then One of the Main beacons in Terms of Fundamental Questions one of which will be That you will be Exposed to tonight and that is the Nature of Time so that let's welcome lenny You Can Walk Around or up there god the Middle Frankly I Really Prefer to stand Right over Here Okay, i can't they won't let me um? Kurt Vonnegut Once Started a lecture I think he was Addressing some Librarians, oh I'm supposed to oh, no, no i'm supposed to stand Over here [uh] And he Said you know I'M 52 years Old I'm a grandfather and I can get to do Any Damn thing I please And a Piano rolled out and he Started to play Stardust he Said I always Wanted to play Stardust Well I'm not 33 I'M 73? I'm a grandfather 9 Times over I have Three Great-Grandchildren and by Damn i can do Any Goddamn thing I please What I feel like doing Is what my Grandmother Called Catching Fetching Means Complaining and I'm going to Complain right now It's not A very Gracious Thing to Do when you're Invited to give a lecture but I'm going to Complain about the venue for the lecture My Complaint Is that These Goddamn machines Are Ruining my culture in The Old Days When you went to a lecture like this A Physicist Would Get Up and With Nothing but a piece of chalk in his Hand to defend Himself and To attack you and do Whatever it was he was going to do that Professor Would Get Up and There was Body language There were Gestures If He was Any Good There was A Ballet Sometimes They Were Bad There was One Fellow, well don't you know of Course who, was the great Master of This was Declining? An Old friend of mine There, were some People who being at it There was One Guy very very Famous Incidentally I won't Mention his Name and he Would stand at the Blackboard and Little Tiny Thing and he Would [magnet] And then he Would Turn Around and Look at your See He was terrible? But it was a human Thing you Remembered you very, well Remembered who the who the lecturer was? And you Remember what he did then you Remembered how he moved These Days it's Completely Different you stand at a computer like This and all you get [to] do is push Buttons This to me Is an ultimate Degradation of my culture and I am Going to Say the next Time I come Back Here I want a blackboard Okay, i'm [gonna] do What every Old Physicist Does Just Before he Becomes Senile Or just After We become Senile I'm not sure Which I'm Going to Talk [about] Time There Everybody Talks About Time when They get to be a Certain age They Think Maybe they understand it Or. They don't understand it [uh] But They Have this inner Need Somehow to Express Themselves About Time I Didn't Think much about it but it might be Because They don't have Much Time Left I'm not sure but um we're Going to Talk about Today My Transparency is Perfectly Clear it's Perfectly Clear what it Says up there it Says Future Past the Future [This] is not my fault that it's off the Slide and [it's] Probably going to be More off The Slide as far As i can tell in Any case, why is the past Different than the future Now the Past Certainly Is Different than the future ah? Let's See if This Thing will Work Yeah if I show you the slide no doubt you will Say that's the past and you'll be right that's los Angeles Circa Anybody want to Guess I Would Guess 1939 you think it's 34 With Cars looked to me like 39 but I'm not sure I'm not Sure so Anyway no doubt there's Nobody here who thinks that's the future right Nobody thinks it's the future [and] if I showed you this Well you'd Probably Say? Oh that's a Picture of the future but this big Difference The big Difference is We know the first Picture was the past We have no idea if This is going to be the future? It's a wild speculation it's not going to be very Likely that that will be the future and so, we Can ask the Question Why Is? Why is it so much Easier to know [what] the past was then what the future Is what Is this? Asymmetry Between Time in The Future and Time in the past now no doubt The Ancients Ancients Probably before Maybe before The 19th Century Would Have Said that's a stupid Question Of Course the Past is Different Than the future I we don't have to explain that it's Just Manifestly Obvious Things That Have Happened Have Happened Things That Haven't Happened yet Haven't Happened But as Physics Became more Mature Mature [Err] It Became very Clear that This Was oh I guess I sometimes Incidentally Sometimes I? Blow it on the Transparencies [and] I get Ahead of Myself so i just, did but Let, me come back the Archetypical Example of The One-Way Street, of Time is the Second law of Thermodynamics it's a law of Physics and it Says That Entropy always Increases now you Don't have to know for this Talk what Entropy is with Any Precision you Just have to know that There's This Thing Called Entropy it has to do with Confusion and Chaos and so Forth and it always Increases Entropy always Increases is a basic law of Physics But Where Does it come from the Laws of Thermodynamics [Originate] Out of the Laws of Particles out [of] the laws Newtonian Mechanics [out] [of] the physics of more Elementary Things are the Laws of Nature The very very Basic Laws of Nature The Microscopic Laws of Nature Newton's laws are They [Asymmetric] Like that do they distinguish the past from the future and the answer is no if you have a situation In Which you, oh you see I got ahead of Myself again [I] do this over and over again yeah Let's go back A step Let's go back to einstein Einstein wasn't so much Concerned with the second law of Thermodynamics but he? Was very much Concerned With Space and Time? The Only Thing for This Purpose Today about Space and Time that I want to remind you Of Is that Einstein Said That Space and Time Together Make Up a Common Object Called [Space-Time] and That Time and Space are Deeply Interrelated in Such A way that Space and Time xy and if I had an x the Axis on here I would Draw z x y Z and T From A Common Thing and that Time is Really, no Different than Space Well Nobody Can Nobody Thinks that X to the right is Different Than x to the left The Laws of Physics Are Certainly Symmetric With Moving to the right Or moving to the left then Were the Same for Moving out of the Blackboard and Into the Blackboard so what is it if Einstein Was right and Space and Time are Really of the Same Nature how is it the Time Seems to be so Asymmetric to Us Why, is Time A One-Way Street When Certainly x and y are not One-Way Streets so Let's Look for an answer See, what, we Can find out About it let's go back to the very very basic principles of Newtonian Mechanics Here's a Picture of the solar System and Newton Himself Would Have Told you that you Cannot Tell from this Picture Whether The Planets Are Going to move Clockwise or Counterclockwise If I told you the planets Always Move Clockwise You Would Probably Say to me There's no Reason why Planets Always Move Clockwise if Clockwise is a possible Orbit for a Planet Counterclockwise is also a possible Motion of Planets so The Fundamental Laws of Physics and Particular Newton's laws are not a symmetric With Respect to Time Anything That Can Happen the Opposite Can Happen Any Movie Picture that you Were to Make of this you could run it Backward and you Could not Tell [the] Difference So the Fundamental Laws of Mechanics Newton's laws do not distinguish the past from the Future Likewise The Laws of Quantum Mechanics The Fundamental Laws of Quantum Mechanics the Fundamental Laws of Atoms the Same Thing is true you cannot Take a Picture of an Atom and Tell Whether it's going Backward or Forward The Laws of Physics Are Completely Symmetric, so what's going on why Is it that the World Looks oh Asymmetric As far as I know the first Person who asked This in modern form was a great Hero of mine Ludwig Boltzmann Ii Who Was very Worried About the Second law of? Thermodynamics he Could Not Understand why it Should Be so that of the laws of [Physics] the basic laws of Physics are the Same Forward and Backward How Could it be [That] Entropy Always Increases He Thought about it he Thought about it he Thought about it and in his Profound Wisdom he Came Up and Said Entropy Almost Always Increases That was Boltzmann's Great Contribution to physics, [oh] This was A very big one This was A very Big and Deep insight it was not his Only Contribution to physics But in Many Ways i think this May have been his greatest Contribution to physics To Understand that the Second law of Thermodynamics Is not exactly A law in the Same way as Conservation of Energy in the same way as F Equals Ma it's not always True it's Just Almost always law True it's a statistical, law it's a probabilistic law Doesn't Mean you Can't See Something Crazy happen that Though that you, wouldn't Expect going Backward it Just means Most of the Time you don't Now, we Can Discuss [how] much how Many Times you're Likely to See something crazy what do I mean by something Crazy Going Backward? [You'll] Spill you Spill, you're A bowl of oatmeal on the Floor and goes Plop Onto the Floor Very Rarely Does The Oatmeal assemble Itself Jump Back up Into your bowl the Laws of Physics Permit it Now in Order to have it happen you would have to have all [of] the molecules Both in Me not only in the oatmeal but also in The Floor and all Around the atmosphere and Everything Else Reverse Themselves very Precisely but if that were To happen The Laws of Physics Would Tell Us that oatmeal Would jump Back, Into the bowl Does it happen Well Given Enough Time it will happen But it Hardly Ever happens [as] i said that was Boltzmann's Great insight [or] One of his great Insights Into physics um Boltzmann Went Further he Wanted to Understand Deeply More Deeply why the universe Is [a] One-Way Street Why Entropy Always Increases He was not A cosmologists at that Time There was not the subject of Cosmology? but From From What I understand from what I can glean from Historians from People who have Studied What Boltzmann, did Multiple Had A very modern idea of how to think about this I'm going to put Words in his Mouth I'm going to put Words in his Mouth but I think [They're] Words that he might Have? Said Boltzmann was interested in The Universe he was interested in why The Universe Proceeded in One Direction and? One Model of the Universe that he Made he Really did This exists in the Literature was the Universe in A box A? Closed Sealed Box Like This Room Except Without Doors Without Windows Full of Whatever it. Is it's full of? That was A Model for the Universe That Boltzmann was interested in Now Arm? Let's start here Let's Take Away the Letters and Start With A Completely empty Universe a Completely empty Universe Nothing happens It doesn't go Forward doesn't go Backward it just sits There so it's Completely Symmetric What Boltzmann Said is Let's Start A universe in A very very [unusual] Situation? One that is very very Special It Didn't much Matter what the special Situation. Is but it Should Be special here was a special Situation that he Imagined A Large Number of Molecules 10 to the 80th of them that's about the number of Protons in the Visible Universe Start With A large Number of Molecules or atoms or Whatever it Is All in The Corner of The Room all in The Corner of the Box the black Rectangle Here is the Boundaries of Box and Boltzmann Said put All the Particles Into the Corner start it that Way What will happen next, [well] you can guess what will happen next ah? If You're a little bit Perverse you might Say, oh? They're Going to Squeeze Themselves Even Tighter Into the Corner of the Room doesn't Sound right Much more Likely Although they Could do that it could happen but [much] more Likely Most of the Times if You found molecules like this You Would find them Streaming away from that Point? You will find them Streaming away from that point and Here's something That Boltzmann imagined I imagine Boltzmann Imagined it Boltzmann imagined That The Molecules Would swarm Away and in The Process of Swarming, away during the Time that they Were Flowing away from the Corner In the Process of Flow some Turbulence might Happen the turbulence might Create Little Eddy Currents Little swirls Tornados Hurricanes Whatever and These Swirls Might Have structuring Them I it's not by Accident that These Look, like Galaxies I meant them to look like Galaxies Again I get ahead of Myself but [okay], let's go? Let's go There he Said during the Process of Moving away from this very special State Things Can Happen Structures Can Form Eddy Currents Can Form and During That Period Is When everything Interesting in The Universe must have happened Ultimately if You Wait Long Enough everything Evaporates Everything Turns Into Evaporation Products Photons and Elementary Particles Nothing is Left but Particles in Thermal Equilibrium Particles and Thermal Equilibrium Means Particles Uniformly Filling the Box Randomly Moving Around and that's it that's the end Game Just what a physicist, Would Call thermal Equilibrium Boring it lasts Forever and Nothing Else Happens so there's A short Period in Boltzmann Box During Which some Interesting Things Happened and Then Nothing Just Heat death heat Death who Call Heat Death or entropy Death Entropy Death everything fades Into A meaningless Boring Uniformity But Boltzmann Knew This wasn't Quite right In italy he Knew This wasn't Quite right and what he Said is if You Wait Long enough Just by Accident by the laws of large Numbers Just by Statistical Probabilities if You Wait Long Enough I won't tell you how long it [is] far far longer than the age of our Universe But if You Wait Long Enough By Accident the Molecules will Just Accidentally reassemble Themselves in The Corner of the room and The Whole Thing will Happen, over again So the end Game was not Really the end Game it's Just The end game for A long Long Time These Are Called, Recurrences They're Called Plonker a, recurrences but I think the idea, was first due To Boltzmann Things will Recur if You Wait Long Enough Now Boltzmann Formalized This Idea in the Following Way he Said Let's Take the Space physicists and Mathematicians Are Always Putting Everything in a space not Space not our Space but in a space Let's Take the Space of all Possible Configurations all Why Does this Happen I'm going to go back yeah all right the Space of all possible Configurations This Region Here The Back Inside the Black Region that's not the Universe it's all Possibilities for All [Where] all the molecules could be Now Up in the Center There you see a little pink Dot I will not try to aim This Thing at it because it will Just Flip the Transparency There's a little Pink Dot in The Center of the blue Region Think of the Little Pink Dot as the very Special Starting Point it could be the place where [all] of the molecules are in the Corner of the Room The Blue Region Is all the possible Region Where There's Interesting Structures Galaxies Planets All Those Sorts of Things and The White Region Is Just a boring Equilibrium the dull Boring Equilibrium Where Nothing happens and Boltzmann Said Look if You start if for some Reason Unknown Reason We don't know who put the molecules in the Corner of the room? But if You [start] There and you let the system run it will Move out [of] that Region Into The blue Region that's the Molecules Forming Clusters Forming Eddies Forming Galaxies Forming Whatever it Is they Form People But if You Wait even Longer and that's Good that's A good Theory that's a nice Theory it tells you that With A starting point Which Is special you can get Where you want to go where you want to go is where Boltzmann Found Himself in A world Full of Structure But he, Also realized Something Else he Realized if You Keep Going and Wait and Wait and Wait The Universe will Pass Through Every Possible State Many Times Just Statistically it will Wander Around in This Space over and Over and over again Every Now and then Passing Through the blue Region Sometimes Most of the Times it will Pass Into The blue Region Without going Through the Pink Region The Pink Region Is a little Tiny Dot With Almost no Probability at all The Blue Region is Bigger Technically We Would say it has More Entropy? The White Region is the biggest of all it's the most Probable and The Universe Wanders Around in The Space of Possibilities Every Now and then Passing, Into the blue Region when it's in the blue Region People Can, exist Planets Can Exist and so Forth but [When] it does so most of the Times it doesn't Pass Through the pink Region That Means Most of the Times Almost all the Times if you find Yourself in A world More Or less similar to Ours [the] [Past] History Does not Look, [like] what you might Have Expected Namely All the Molecules Coming out of the room in fact you might find [Yourself] in A universe This is a universe Born out of Fluctuation A Universe Born out of Random Fluctuation Just by Accident [a] universe Formed This is something Deep That Boltzmann realized but he Also realized That Most of the Times That Universe Is not going to Look like what you Would Have [expected] in A theory [an] Ordinary Theory Where the molecules Flowed out of the Corner of the room? More Flowing out of the Corner of the Room is just a substitute for the big Bang The Big Bang The Universe Started Small it Started Concentrated it Started very Special and it leaked out Think of it that Way Where Both [Mom] Understood Is that most Universes That are Created out of Fluctuation Don't Look Recognizable They Have Properties that don't Make sense They They might Look, like this Just as likely as they, Would look like [a] bunch of Galaxies so Boltzmann Understood that he Rejected This as a possible Explanation of the World He Understood that the World was not a world in A Box but he Didn't know what Else to, do he Didn't know how to How to think About it he Didn't know how to Understand The fact That The Universe in Our Past Does Look special You See the Problem here was? Only The first Time if The Universe Drops out of the Corner of the room only the first Time Does it Look like Something, We Recognize Galaxies so Forth Most of the Times? Endlessly Endlessly Endlessly it Looks Like Random Garbage Random Garbage But Good Enough for us [to] live in so you, Ought to Predict in A universe like that Not that There was A big Bang Not that the cosmologists who Study Cosmology got it right But you Should Predict a random past which doesn't Look Anything recognizable Now that's Crazy Boltzmann as I said Knew it was Crazy fact He Understood but We are A modern Version of it is if you ask the question what Is the most likely thing the most likely Configuration That Would Form out of Chaos in This way by Fluctuation by Randomness What's the Most Likely Thing? Given that it has to be that it [has] to have Intelligence so that it Can ask about the World Well the answer Is the most likely Thing to form Would [be] One Brain and Nothing Else One Brain and Nothing Else Because to take two but to Make two brains Is Much less Probable Than to Make one Brain out of chaos the most likely World That Would Contain an intelligent Creature That Could Ask Questions Would Contain One Brain This Is These Days Call it a boltzmann Brain This is Called a boltzmann Brain and of Course this is not the right Theory of the World We don't live in A world with only one Brain so this Theory is not the right Theory It's Clearly wrong that's what's wrong with it Okay so now the Question Is what does modern Cosmology have to Say About it Wouldn't it be Better to have a one-Shot World or One-Shot World Means the molecules Come out of the Corner of the room? They do Their Thing and then They go off [and] We Never hear about them again no Possibility of These Recurrences Going on and On and On and Telling Us that the most likely Thing in the World Would be a single Boltzmann Brain A One-Shot World Is a kind of goal of Cosmology By one Shot that i mean the whole Thing Happens Once and it doesn't Recur and it's not it's not a universe in A Box it doesn't come to Equilibrium The Molecules Flow out Once Produce Tornadoes and Whatever it Is they Produce and then go Off and They're Gone That [You] Would Still have a problem you Would Still have to explain Why They Started in This very Special Configuration but Maybe someday We'll Understand why, They Started in The very special Place Okay so is that Consistent With modern Cosmology? Let me Talk a little bit very very Quickly about Both Yesterday's Cosmology and By Yesterday's I mean 25 Years ago Versus Today's Cosmology and We'll See what what we've learned? [Twenty-Five] Years ago There Were Three Actually two cosmologies Two Versions of Cosmology one of Which nobody knew which, was right but it was believed that one of them, was right they, were Called big Bang Cosmology and There were Two Versions Open and Closed an Open Cosmology The Universe Was Infinite but More Than that it Continued to be Infinite and Continue to expand A closed Cosmology had the Property that are Expanded and Contracted and Crunched Ended in A big Crunch now This Picture Here this is A Graph and The vertical Axis is the Radius of the Universe at any given Time and on the Time Axis is the Time The Left-Hand Side the Left-Hand Corner Is the Starting Point the special starting Point The Universe Starts very Small it Begins to expand Interesting Things Happen during the Expansion Interesting Things Mean Putting us Down Interesting Things Mean all the good things that we're Looking for and then it Comes Back and Dives and Crashes Crunches The Universe Just Crunches to a point and it's over That's Clearly a one-Shot Universe you get one Chance that's The end it's fine except you have to explain why you Started in The special State The other Version Which is also fine Is called The open Universe and it's a universe which Just Continues to expand so the radius of the Universe Just Expands and Expands and Expands Now Because it Expands all the particles Fly Apart if They Fly Apart it's Still True [that] you only Get one Shot They Fly Apart Once They've Flown Apart Too far They Can not Interact with each other Anymore they, don't form Galaxies They're finished, They May Still Be There But They're Flying Apart from each other and not Useful [for] Making Even A Boltzmann Brain so again an Open Universe is also a [One-Shot] Universe And so this is good We Have an Explanation of the World One-Shot Universe except that We have to Understand? The Starting Point all of This Was Understood? It was thought to be The Solution of the Problem? Until About 15 Years Ago ten [Years] Ago and so Forth Dark Energy was Discovered? To a physicist Dark Energy is called Lambda It's called the cosmological constant it doesn't Matter whether you call it the cosmological constant or you call it Dark energy It's a condition in Space Whose effect for our Purposes Is One of Two effects Either it Accelerates The Expansion and Makes it even Faster than it Would be Without the cosmological Constant in fact it creates Accelerated Expansion Which Keeps, Accelerating and Accelerating Accelerating That's if Lambda Is positive if Lambda Is negative it Does Exactly the Opposite it Accelerates The Crunch it Kills The Universe Even Faster Think of the Crunch as being The Universe being Killed and Ended The other Possibility Lambda Positive is the universe Accelerated Ly Expanding Now Either One of These There's a Picture for Lambda positive Incidentally This Is to be Compared With the open Universe Which I described before Where the curve [Just] went off Into the Upper right Hand Corner Without Curving Upward like that positive Lambda positive Cosmological Constant Positive Dark Energy Makes The Universe expand Even Faster At an Exponential [Rate] an Exponential Growth of The Universe That Actually Sounds very Good for One-Shot Universes The other Possibility as I said Is the negative Lambda and that Causes the Universe to Crash e Faster Than it Would Have If if in the in the closed Universe So it's sudden, Death to the Universe Both of Those Sound as I said like reasonable Candidates for One-Shot universes Everything Interesting Starts in The Beginning of That Curve and then the Universe is finished With its Thing Well In our Universe Lambda is Positive It's exponentially Expanding that's an Observed fact That's not a Conjecture it's not a theory it'S an Observed fact our Universe is Expanding At an Exponential [Rate] and This Sounds Great for One-Shot Theories but it's not so Let me Explain What's wrong With Thinking of the Accelerated Universe as a One-Shot Universe [This] is a picture of Hubble's law Most of you know Probably most of you know First of All i'm sure Most of you know the Universe is Expanding and? You know it's Expanding According to hubble's law Which Says that the velocity of Recession away that the Center is the sun The Galaxies Are Moving away from us the Further away, they are the faster they Move That was Hubble's Discovery Edwin Hubble he Discovered that the Velocity of Recession is proportional With A constant Called Hubble's Constant Times The Distance The Further away, you are the Faster you're Moving and is A constant of Proportionality between Now this constant Is not Really A constant in Most Cosmologies it Decreases With Time But in an Accelerated Universe The kind with A cosmological kind constant the kind that We know that We live in That? Hubble Constant Really is A constant Now that in Turn Means That if You go far Enough away There is a place Where Things are Receding away from us with the Speed of light How Can We find out How far We Just Substitute for V the Speed of Light and? Solve The Equation and That tells Us that Equation tells Us how far away, We have to go until We come to the place where things are Receding away from us with A? Light if They're Receding away from us with the Speed of Light then Anything that's Further away from that Cannot be Seen The light with them the Recession Overwhelms The Velocity of Light and Prevents even A light ray Which is trying to get Back Into That Circle it Swept away with the Expansion so nothing Outside That Region Can Ever Be Seen in an expand and Accelerated Universe the circle Where that happens is Called the Cosmic Horizon It is very Much like [a] black hole Horizon Except the Black hole Inside out You don't lose Things, Into the Black hole in This case you lose things to the outside [Because] they, Pass out of the Cosmic Horizon so The Accelerated Universe Has a Horizon, no big deal Here's a Picture of the Accelerated Universe everything out Behind the [Horizon], We Can Never See so I've Painted it black Cannot Be Seen Inside There's our Galaxy There's the Andromeda There's all the distant Galaxies There We are But They're Moving away from us they're Rushing away and They're Rushing? Away so fast that when They get to the Edge They're Moving With the Speed of Light and then Faster Than the Speed of light and We cannot see Them That's The Picture of the Accelerated Universe the classical Standard Picture [it's] Called the sitter state [The] sitter Space and That's what it looks like Now if You Wait [awhile] all Those other Galaxies will Pass out Through the Horizon and We won't See Them That's Probably in Our Future not only That There are personal Futures? but the future of our Galaxy in Time About [a] trillion Years from Now Or. Maybe it's a hundred Billion I don't remember [Two] Hundred Billion Years from now all of the Galaxies Most of Them will Have moved out Through the Horizon and We will truly Be Alone There will be Nothing in our Astronomical Sky other Than Just Plain? Emptiness Or Almost emptiness Still Sounds Pretty Good for One But if You even Wait longer The [Galaxy] Itself will Evaporate The Protons That Make up the Galaxy will Probably Disintegrate They will Form Radiation the Radiation will Pass out Through The Horizon and There will be Nothing Left That's The Standard Picture of the Accelerated Universe and I'm going to emphasize Once More that sounds Awfully good for one Shot Universe it only happens Once and then it's Gone but Quantum Theorists Know Better They Know and This is Largely the Work of Hawking and and It's Largely the [Work] of Hawking Hawking Understood that The Horizon of A black hole or the Horizon of the Cosmic Horizon of the Universe Is Not A cold Dead Place it has Quantum Energy and That Quantum Energy Gives it a temperature it Behaves as Though There Actually, were Particles in A box Now Most of Those Particles are Concentrated near The boundaries of the Box near the Cosmic Horizon but They're Constantly Fluctuating They're Constantly in Thermal Motion and Guess what Every so often Boltzmann Rears his Head Boltzmann Rears his Head and Says Every so often Those Particles will assemble Themselves Into a structure of some Sort if You Wait Long Enough Over oh of Course Boltzmann Brain It too will Evaporate and Disintegrate But Wait a little longer not a little longer a lot longer and Another One will Help Repair and then Another one so We haven't Escaped From the Conclusion that in This Kind of Universe Almost everything that ever Forms? Overwhelmingly Probable That if You find an intelligent Object That intelligent Object will be Something very very Different than Us This believe it or not cosmologists and Physicists, worry About This They worry About it not because They're Worried that, we are Both Brains were not But when You have a theory Which gives Predictions Which are absurd you Can Ask Yourself The Question is your Theory right your Theory is Probably Wrong There's Something Wrong With a theory that Says that the universe Simply Forms A Box With Thermal Particles in It and Unfortunately That's Exactly Where modern color Cosmology [has] Led Us By virtue of the Dark Energy Which Makes The Universe expand in an Accelerated way it has Led us literally right back The Boltzmann Box It has Led Us right back to boltzmann's Box Something [Is] Wrong With our Cosmology okay I Could Leave it There I could Say that's the great Puzzle of Time in Our Time We've Gone Through some Cycles and that's Where it's Left but I won't i will try to take you a little Further and Tell you a little more you know I was going to use the blackboard but you Know I am 73 years Old and I'm getting tired so I'm going to use the machine as much as I hate to use a machine I'm going to use it I'm sorry Jeffrey that I made you bring this Thing Here I know you carried it on your back Yourself I Know Jeffrey Carried it he Walked From the Institute it couldn't fit in his car He Carried on his back and I'm sorry and I said Jeffrey you have to do this for Me and Jeffrey Said Well yes all right! If you Promise if you Promise not to tell what Happened in Miami Beach in 1975 I will Carry beer and I Promised But i can't do it I'm too tired so i'm going to go on with the with a [slideshow] All right The Next Step in Cosmology and One Which Is speculative Honestly Speculative, We do not know if it's correct We Some of Us Suspect it's correct Some People are very derisive About it and Say it's Silly it can't be Confirmed I'm Not going to try to Convince you that it's correct but it may be a Component in Solving This Funny Problem about Boltzmann's Problem About Time so I will tell you what it Is the Multiverse Theory Begins With a spacetime that Space and it's empty Space it's Completely empty Space But it's Rapidly Expanding Space it's Space With A cosmological Constant it's Space With A lot of Dark energy and Although Because it's empty you can't see what it's doing but it's Expanding like A bat out of Hell It's Growing very Rapidly and in an Expanding Universe Expanding That fast Fluctuations Happen Things do Happen even Though it's [Completely] empty, one of the things that Can happen which was Discovered in 1970s By Sidney Coleman and his Collaborators Sidney Coleman, was One of the great Physicists of our Generation of my Generation and My Younger [Friends] Generation over There Sidney Coleman Discovered that a universe like this from Time [to] Time will boil a Bubble Just like Boiling Water will Create a little Bubble Now it'S an Unlikely Thing to happen but that Just means it Takes A long [Time] and when it happens A Bubble Forms in That Bubble The Properties of Space and Time are a little bit Different or maybe a lot Different Than in The blue Region Space and Time and Physics and Particles The Constants of Nature Are Different in The red Region [and] The blue Region The Red Region Starts to Grow and it Grows and it Becomes in Itself in its Own Right [a] Growing Universe We could live in There Maybe Maybe We Could live in There but in That Universe Another Little Bubble Can Form and This Goes On and On and on It's A free Lunch There's Nothing To Prevent This Thing from Going on and on and on Forever That's The Mathematics of it the Mathematics of it Keep Boiling often When I say the Mathematics of it I mean the Quantum Mathematics of it Keep Boiling off Bubbles Bubbles Bubbles Bubbles each one of them Could Be a little Universe in Which We could live and each one Is Different from the other? I'm going to show you a way of Thinking about it and then I'm going to tell you a little [bit] About the Mathematics of it I See, we still Have About 15 Minutes is all right yeah, okay? All right so this Is what I was Going to Draw on the Blackboard? What is it? The Starting Point Down at the Bottom is a Growing Universe but it hasn't grown very much yet Can you See the colors are There colors on There From Where I'm Standing if There's no color at all The Colors Are Fine okay, what's the color Down the Bottom Red it Should Have been Blue Because it Should Have Matched my Previous Color That's The Starting Universe it's Starting to expand Every Time it Expands it doubles [Lets] They Have a Certain period of Time it doubles Whenever it doubles I'Ll represent that by the Universe Growing, Into Two pieces But then Because Those pieces separate from each other Because They're Growing They separate From each other They get too far from each other to Communicate and so I'll just represent that by the Universe Bifurcating Now it doesn't Really Bifurcate that so this is A this is what you Would Call A? Idealization Or Simplification The Universe Bubbles and Then it doubles Again and doubles Again What is the Color Coding the Color Coding is Exactly the colors of the Bubbles that We started With in The Previous Slide? Different Properties Each One, of These lines is A Universe in Which Somebody Could live Maybe They Could live Maybe The Properties Are Appropriate [to] live in and it just Keeps going on and on Growing and Growing and [Growing] as it Grows [it] Produces More Little Pockets More Little Pockets it's Diverse Different pieces Are Different Than other Pieces and There is a Probability Distribution of Some Kind Telling you how probable it Is as you move up That You're in A red Universe or a blue Universe or a green Universe These Different Colors Could Just Stand for Whatever Different Properties you like Whatever They happen to stand for Different Properties and Notice that There Are places Where the colors Change Those Are These Coleman de Lucha processes Which boil off Bubbles of A Different type That's Kind of what that's not Kind, of that Is very much? Like what an inflating Universe Looks like if We Take Into Account That [These] Bubbles Can Happen that the Coleman de Lucha Bubbles Can Happen Looks Pretty Much Like that that's a Fairly good guide to it [Alright] Let's [Imagine], [oh] Here is Where [I] was going to Write some Equations Let Me write the Equations okay You Could ask the Question what's the Person Number What's the mean Number the average Number of? Lines Bubbles Universes Whatever you want to Call them of A given color at. A given Time as you move up Time Moving Up Comes in discrete [Steps] the Bottom the next layer [the] next layer in the next layer and you Could ask what Is Can tell me if You can't See This and I'll Make [it] bigger what is the average Number Can that Be Seen Yes Good what's the average Number of? Universes Or Bubbles of Type M [M] could stand for red Blue Green Whatever it Stands for at Time T plus [1] What's the average number at Time T [plus] 1 in other Words when you grow Up a level of? Bubbles of Type M and that is equal to The [Average] Number of Bubbles at Time t twice the Average number at, Time T Why Twice Because it doubles at every Stage at every Stage it doubles so there's a source of new Things The Source of New Things Is this doubling That's The first Term Now you lose some Lines of Type m a blue Line Can Turn Into A red line so you lose some so you have to subtract And what you have to subtract Is a Certain number Which Is called Gamma and It's the Probability That a Universe of Type m. Will spit off A Bubble of type in Times the Probability or Times the Number of Things of Type m This is Summed over N Don't worry if You don't know I'll explain what this Is but I just Flipped Just Tojust for The Experts in The [Audience] and There are Experts in The Audience on These kind of Equations I'm going to write the Equations and then I'm going to tell you what they Mean All Right and Then There's Another Term Which Increases This This Is loss Things of Type m Become Things of Type n so you lose things of type m All Right but you, also gain Things of Type m if in Becomes M and that's N Sub in Also [sum] [Summed], over [Ya] [sum] over N That's an Equation it's got a Name it's Called a markov Process [I] wanted to show you a picture of Markov who, was A very very Famous Method Russian Mathematician And it was Responsible for These kind of Equations [I]? Couldn't I looked on the Internet and I finally Found a picture of Andrey Markov and [Upend] out to be a Russian Not a Soccer Player you know Those Guys Would beat each other up with sticks Hockey, Player yeah I'll Just tell you Briefly what this Equation Says is the number of each [Type] and A given Level Is first of all a number that, were There before that but Double Because each Time it doubles Plus Some Loss Because you lose some of that type when they when They become other Types? Plus again When other Types become the type you're interested in so the balance Things Things a balance of Statistical Balance Anybody who Knows This Kind of Equation Knows how to solve it and what Guess what you find when you solve it you find That If you, were to look if you, were to follow one of These tracks Branches You are Somebody who lives in this you Don't get to See the whole [Thing] all you get to do is follow Along the line a branch Leading to a branch and a branch [and] These Equations Simply Tell you what the [Probability] Is [that] you See Different things as you move Along the Branches Guess what it Says it gives Exactly the Same [answer] as Boltzmann's Box Exactly the Same Kind of answers The Wrong Kind of answers The kind of answers Which Say you come to a dead end of Equilibriums and Fluctuations Equilibriums and Fluctuations and This Kind of Universe you lose again [You're] Back in Boltzmann's Box Even Though it doesn't Look Anything like a simple Static Box It doesn't Look Anything like it and yet it comes Back to Exactly the Same Thing The Simple Static Box if You Follow your Way Along There and What you find is a universe Dominated by Fluctuation where Almost all [of] the Time if you saw something It Would not Look like what you Would Expect to see because it Grew out of Fluctuation Rather Than The One-Shot Kind of in Those Point Is You Keep Going Up and Up that doesn't terminate like that it Goes Up and up up and Up and Up and Up and If you Keep Following it up you Eventually Just Discover That There are Recurrences Back and Forth and Back and Forth [Boltzmann's] Brains Are normal Universes and You haven't you haven't [won] you Still have not Understood why, Time is a one-Way Street That Goes from Something very Simple to something Complex and that's it end of Story you have not explained that Well I Like to describe This by Saying that it's led to a stagnant Pool It's led to a Stagnant Pool in which the only things that ever Happened Happen by Random Fluctuations If A little Vortex happens it happens not Because [There's] a flow of Water But Because Just by Random Accident some Molecules might assemble Themselves Into A vortex That Vortex Is very Unlikely to Look like The kind of Vortex that you Would get from A flow of Water The Universe Expanding out of the Corner of the Room, is like a flow This is Like a dead end So Almost every Theory, We know of the Universe Either Is Empirically Wrong Or Ends in This Kind of dead end Where The Things That Happen are Just Random Fluctuations However Remember I told you about the Crunches if There are cosmological Constants Which are negative The Universe Can Crunch Well That Means These Bubbles have the Potential Possibility of Dying? This Is very Much like a tree of life and the dead Ends Are like species Which Just died out To some extent Red might Correspond to the kind of Universe That Crunches it Ends if it Ends it doesn't Continue to branch it doesn't Continue to Grow You'll Have to modify the Equations the Modification of the Equations Involves One New Term Here The One, New Term is the Custody with a probability of Dying And that just gives you A - why A - Because it removes Probability A Constant Doesn't Matter what it's called Gamma em Puns in em don't worry about it what about the Equation The Main Point Is it changes The Equation and what does it Change the Equation - Let me Just Look at These Terms this Term is a kind, of Source it's Creating new [Things] This is a sink It's eating up things The Equation has Turned Into an Equation Which Is Very very similar to the Equation Which you Would have if you had a source of Fluid on one end and A sink Down at the other end so that the Fluid, Flowed Fluid Flew Floated the Fluid Fluid The Fluid Flowed From Left to right from source to sink Well Guess what happens when a fluid Flows from source to sink It creates Eddie's Endlessly it Creates vortices Endlessly Those vortices, however have a very Definite sense of Time Time Does run from Left to right Somebody in Living in One of Those vortices Would Realize the Vortex, was Born Somewheres and Would run out of Steam Somewheres very Unlikely To See A Vortex Propagating in The Opposite Direction [A] Flow Like This is Exactly what you need to understand why, Time is a One-Way Street the Multiverse The Idea of a fractal Flow These Equations here Appear to be Possible To [Give] you universe which runs in One Way. now is this going to run Into Trouble Are People Going to Analyze it and Discover again that it leads you back Into Boltzmann's Box [I] don't know But at. The Moment this is the State of the art this is as much [as], [We] know I'Ve Taken you through all the Various Cosmological Assumptions from Boltzmann's Box The Fractal Flow and Told You what they have to [Say] about the Arrow of Time I Don't Think we're Finished This May, or May not, be the right answer and if You Invite Me Back with a blackboard in About Five Years from Now and I will be 78 I Well I will try to tell you the answer Thank you? so, well the only Problem is [a] [moment] Glass so thank you Learning for a Wonderful Talk very Stimulating and They're very Provocative very Challenging so We have Time For A few Questions? [I] think [I'll] Let since He's up there at the [Conference] I can't See it on [my] glasses, oh okay I'll See Why i can't See either it? So let's See I saw a lady over here yes and Speak Up stand up Young and it's Importantly to Speak Loud because Both [Geoffrey] and I are Both Deaf We both Definitely, we can't See? I Don't Have an Explanation for that but I think I could Concoct an Explanation why, some Brains Think They Can do that lovers cannot But I will not i i I am not going to tell you that I know that People cannot do that I Once Watched a man do A very Amazing thing he Do We have a match two minutes [I] saw him do Esp tricks the Esp tricks Were Absolutely Remarkable Somebody Got Behind Him and By Pure Process of Thought I was the one Behind Him in fact my pure Process of Thought I? Guided Him Forward and Told Him what to do [I] May be the Guiding, was go Forward go Forward go Forward go Forward go Left go Left go left go left Raise your arm Take the Chalk [and] Write A vertical line on the Blackboard and he did it and He did it nine Times out of ten and I was the only one in The Audience who knew what he? Was supposed To do I? Said [To] Him Afterwards Small his Name, was Small Gurewitz he? was a physicist right he did This i said the math was smooth this Is Crazy do you have Any idea what you do He Said, no I don't know what I do but I'D be Willing to try to find out so we Did some Experiments We did This over and Over again until I Began to realize that he [was] Picking up on the Tiniest Little Body Gestures [of] mine as, We went Forward I would go go left go left go Left and he Was his eyes Were Going back and Forth and he was Picking up on this he was Hypersensitive in A crazy Kind of way um? I asked him Small where the hell did you learn how to do this and he Said, well it was in the Russian Army The Russian Army was trying to Detect submarines in The Ball in The [Baltic] and So they got a whole Bunch of extremely sensitive People who Showed an Extraordinary Ability to do This and [They] Started Training Them to try to Detect Submarines in The baltic They Didn't They Didn't Detect Submarines in The baltic but the moral of the story Is that some People are extremely sensitive to Certain Small Signals and so Forth so wouldn't [Funny] Would? Surprise Me if There Are People who Can pick up on things that most of Us can't that's all I'll Say ghosts no but Let's do This Gentleman in The Back Speak up [It] doesn't Allow Bubbles to collide [With] each other and If Bubbles Collide if A Bubble Collided With our Bubble Assuming We live in A Bubble it Could Conceivably be an observable Event it Could that Could Have an Observable Imprint on the Microwave Background, on the Sky At the moment People Have looked for it this is a this [Is] was our A reasonably High Priority Thing that cosmologists Search for observational cosmologists and They Did not find it However Theoretically it's a highly improbable Thing so but They Can, They Can, collide with each other Cuddles [Lock] Hubble's law We're not at the Center everybody Sees the Same Thing but for that I suggest you Take my Cause my online Cosmology [Chorus] No it's good it's good it answers all Questions Like this and then it's Called the theoretical Minimum Their online Cosmology Courses [and] The Books will Come out and the Books will be Cheap and you Can you Can Buy them and go Along with the Course But the answer is Nobody Sees [Anything] Different Than everybody Else Everybody's Separating from everybody Else But you have to draw the Picture and the only way to draw the Picture [is] to pick a Center and Say Somebody's at the Center That's The Question are you Around you and and I have to Say Personally I'm Confused by it and I [think] everybody who does this is a little bit Confused [ok], yes you're Picking [the] Time you're Picking the [vert] you're Picking the Direction that you're Calling up you could turn the whole thing Over and Call The Big Growing Tree the past But it Would Just be A word You Would Just be Calling it the past something the diagram is Breaking the Symmetry is what physicists Would Say? and I Think you might Say it's Either one Or the other Both Can happen but They Would be Essentially Identical and you couldn't People who lived on it Couldn't Tell the Difference But I think you've Asked the key Question Have you! By Drawing The Picture the way I drew it Prejudiced it so that There's Already in Our Earth Time and That's that's a that's a that's A good Question [to] which I won't try to answer I think I think the answer May be, no We May be Lucky but but it's Unclear oh my Have Different Constants of Physics The Fine-Structure Constant Might be twice As Big Where the cosmological Constant might be A [ten] to the Hundred Times Bigger [or]? Might Have Different Particle Content? The Proton Might Be Heavier Than [the] Neutron [the] [Fall] of The Equation [Principal], well You could have you could you, could imagine the Form of the Equations that [We] use Today? Being Different but You Could ask Whether [There] be underlying Equations Which could govern the whole thing and for which These were Different Solutions Yes very much so and that's What's one of the things We learned from string Theory? Is that string Theory Does Have the Capacity to describe Many Many Different Things so you know Whether The Equations that We Use are sort of A temporary [Thing] that depends on the age which, we're using them Yes you Can Imagine you Can Imagine that in Each One of These Boxes the Equations We use Today Would be Different but the thing Which governs the whole Thing Would be the Same? Pick Up Yeah Yeah Exactly Yeah That's that's A good Point um There were These Long Long Periods When Nothing happens When [i] say Nothing happens the molecules move Around but They Just Look, like Random Thermal Equilibrium They last Enormous Ly Long Times but Nothing happens so if you use some kind of Clock Which Is not geared to the Time the Microscopic Time of the Motion of Particles Which Which is geared the things Happening Practically No Time Takes Place During, over That Course of A so it depends on how you keep Time If you Keep Time my Events Which Happen and Change the system [from] one Time [to] another Nothing happens during Those Periods it's A tiny Tiny Time If You Follow each Molecule and ask how Many Times it actually is banged Into Every one it's A Huge amount of Time Is the first Time I've Ever Been on twitter No more no more, hmm to [phil] [mahre] not Bill Moyers, oh? Well That depends on how big a Scale you Look at Fractal Dimensions Are Always things Which depend on Scale I? Don't know what it is on [the] super Microscopic Scale some People Think it's [too], [I] don't really understand why There might not even Have be Meaningful on super Microscopic Scales in Our on our Scale [I] know Exactly what it Is it's Three Dimensions of Space One Dimension of Time There's no Question of that On very Small Distances it might be Larger than [Our] string theorists Think the Universe has more Dimensions at Small Distances [at] very very large Distances This Fractal Flow Does have A concept that they mentioned associated With it But it'S an Odd concept of Dimension House dorf Dimension the House dorf Dimension Can be Fractions and The irrational Numbers and it Would Be irrational Numbers Here Typically, less Than about Three I think the Speed of [Light] It doesn't Make sense to ask Whether it's Constant it is to speed flight how fast does light go it goes As fast it's like Those That's it that's Another Way of Saying that the Speed [of] Light has Dimensions The Right Thing to ask About is dimensionless Things All right so you Could ask for example what's the ratio of the Speed of light to the Speed of Gravitons That As far as. We know is Exactly one Everywhere's in The Universe Throughout? You Could ask the the so Called [Fine-Structure] [Constant] That's A dimensionless constant which has to do with the Probability that if A Electric Charge, Accelerates that it Radiates a Particle That Radiates a Photon That's A, dimensionless Number You Could ask Whether that's the Same everywhere's and You Could ask Whether it Depends on Time? Now as far as, We know it does not depend on Time in our Bubble There's No Evidence Whatever that it depends on Time in our Bubble in This kind of Picture it Would Make sudden jumps Every Time The Bubble Changed it Would Make Sudden Jumps and We have no evidence against that We have no evidence Against sudden jumps of it We do Have evidence Against? Gradual Changes, Over Long Long Periods of Time in our Bubble in our World So, we have Never Seen Experienced Any EVidence? For A Time Dependence of What We normally Call [the] Constants of Nature? At least at the [Moment] Well Jeffrey was Really Saying Is that he's getting Tired
I did a degree half taught by the school of physics and half by the school of maths and this was 10x worse in physics. Most of my math professors ( primarily theoretical / mathematical physicists) used the board while every physics professor used slides. Those lectures as Susskind says leave very little impression on you. We had to give exit interviews after we graduated and I just complained about this issue for 20 mins.
I think that it is hard to be a good lecturer. In many ways, a lecture is like a performance. The best lecturers not only understand the material, they also understand the performance aspect. With academic careers becoming more and more competitive (or so I've heard), it's possible that the next generation of faculty simply doesn't have the time to invest in teaching duties.
However, I don't believe the problem stems from technology. Technology allows us to teach like never before. We can store and transfer information quickly and with high accuracy, we can utilize visualizations to understand complex problems more intuitively and more rigorously, etc. Additionally, we now have a vast and ever increasing wealth of knowledge concerning behavior modification. These advances should allow us to create the best learning experience we've ever had.
For example, if an instructor doesn't want to learn how to lecture, she could simply assign lecture videos as homework. And she can choose the very best lecture videos available for that particular topic. Then the instructor can invest that extra time into parts of the learning experience that can't be solved in such an easy fashion, and the students still receive high quality lectures. This idea of a "flipped classroom" isn't brand new, and it's just one way that technology can enhance the learning experience.
Of course, we have to be wary of the "new is better" mindset. We've all heard the saying, "If it's not broken, don't fix it". There is evidence that some old fashioned technology might help retention rates more than its modern technological analog (ie handwriting vs typing). So it's possible that using chalk is better than clicking through a PowerPoint of the same proof (and if I had to guess, I'd say chalk is better). But that doesn't mean we have to reject all new technology. Maybe the instructor lectures on the symbolic, representative side of the proof with chalk, and then she shows a PowerPoint visualization of the geometry or of real life examples. Personally, I'm excited to see what augmented and virtual reality can do for the learning experience.
The point is that technology should enhance our capacity to teach, but teachers still need to invest the time to learn how to teach with that technology! We have to get rid of the false dichotomy of chalk or PowerPoint and apply different technologies for different learning problems. It may be that this isn't feasible with the current education paradigm (esp. with university structuring), and so that may have to change if we want to continue raising the bar.
I'd like to see evidence rather than anecdotes when deciding upon the academic fate of our students.
Physics major here, most of the people here seem to feel like the math teachers tend to be better about lecturing and i'm inclined to agree with that. I would add that within physics the experimental physicist tend to be the bad lecturer's while the theoreticians tend to be better.
Also, Does anyone know who Leonard was talking about when he talked about the guy who would get super close to the board a mutter things like a crazy person? My only guess is Pual Dirac, but he seems kinda old for Susskind to be talking about.
I completely disagree. Important to me has always been the content not the body language, austerity or whatever nostalgic arguments he tries to summon. No student will learn more just because you swap your computer by a chalk.
And considering the time wasted in filling the blackboard, the time students might need just to decode the (occasionally) bad handwriting, and the visualization posibilities to help understanding that computers bring... It's honestly hard to me to justify austerity. Lack of body language? If you do nothing but press a button and read from the screen you are as bad as an old-school lecturer doing nothing but writing on the blackboard (and speaking aloud) his notes. It's not about technology, it's about the lecturer's aptitude.
Again, without trying to offend anyone, it sounds to me like another "winge winge, the past was better, young folks are wrong" case. Times have changed, (sometimes for the worse) this time for the better.
PS: Just personal opinion.
His hunched over lecturer speaking quietly reminds me of my algebra professor. Lectures to the board and speaks softly! No big stick.