Kyoto Prize Symposium: Engineering Concepts Clarify Physical Law - Carver Mead - 3/15/2023

[Music] it's very humbling to serve as the faculty host for today's Laureate semiconductor technology has transformed our world and this technology rests on many foundational advances made by Professor Carver Mead over the course of his career cover meat gave us fundamental understanding of key semiconductor materials and devices he pioneered the design methodologies and how generations of Chip designers were taught and also the automation tools that

them that three words always come to mind physics the laws that govern transistors or circuits or the universe simplicity that distillation down to a clear essence and scalability to millions or billions or an entire planet today Carver will give us a talk on fundamental physical law the title is engineering Concepts clarify physical law and now let's give our very warmest welcome to Professor Carver Mead [Applause]

good to be here today and I'm especially pleased with them the young people here just starting a career I want to talk to you today the rest of you the rest of you are welcome to listen in but I I want to talk to the young people my uh colleague the late Richard Feynman said something that I think captures what we're about ends fundamental physical law

he said the real glory of science is that we can find a way of thinking such that the law is evident if you look out on our discussions of fundamental physical law today they're in the context of three great theories electromagnetism in the form of Maxwell's equations general relativity which tells us all about gravitation and quantum mechanics and its offshoots that tell us about stuff down

at the bottom when you look a little further at those theories they're all over 100 years old and we've learned a huge amount experimentally since they evolved in any meaningful way so I want to share with you today some experiments wonderful experiments have been done that to me make the law evident [Music] so first of all we should know what it means to be at the

bottom and Quantum things are at the bottom level that we know about and what does it mean for something to be Quantum it means just one thing it means the wave nature of matter and we're celebrating the 100th anniversary of that great Insight by Louis de Briley 100 years ago this year what's down at the bottom is not little grains of sand or little bullets its

waves so it's funny to be talking about waves in San Diego but I mean a little further down from what you could see and I know a lot of you here are experts on that subject but if you could just forgive me for a minute for doing a little primer on what waves are about this is a view of a wave and it's propagating from left

to right and I have it instrumented so over here on the right there's an instrument that measures the value of the wave coming out on the right hand side and down here at the bottom it measures the amplitude of the way looking at it from the side and this is a small chunk out of a wave that's many many wavelengths in dimensions crosswise and what do

we mean by all this the wave has a frequency which we see it's the rate at which this amplitude of the wave Wiggles and it has a wavelength so there's a vector that goes with every wave the vector direction is obvious at the direction of propagation is perpendicular to the wavefronts the way the wave is going the wavelength is just the distance it takes to go

one wave down here but the strength of the wave is actually how many waves there are per unit distance and that's called The Wave vector or in ordinary units it's called the momentum the rate at which the wave Wiggles its frequency is called Energy when it's a matter wave and the number of wavelengths per unit distance is called the momentum and the momentum is a vector

which is in the direction that's a wave is propagating now we're going to be doing some experiments with waves the first thing you do is you put up something that stops the wave this particular one absorbs the wave so nothing gets through it nothing goes on to the other side so you don't see any amplitude coming out here but we can cut holes in it and

you can see the wave propagating and you notice it doesn't keep going straight through like a little bullet would and it spreads out from here and if you cut two slots in the barrier you get the famous two slit experiment it's in all the textbooks about Quantum things and what you notice is that on the other side there are angles like the straight through angle which

there are no waves on the left that go straight through but the effect of these two waves adding up together has a maximum going straight through and then you're going off a little bit and the distance from the top slot it's just 180 degrees out of phase with the wave from the bottom slot so there's another angle here where you get a maximum and in between

they interfere with each other the two waves add up out of phase and so the whole pattern here that you measure out on the edge is called an interference pattern and we'll see a lot of those and the thing you notice about the interference pattern is this is a high frequency wave and it's uh wiggling and fast and this is the angle that it makes for

the first Maximum aside from the one going straight through but if I have a lower frequency wave lower energy wave longer wavelength wave that angle is bigger so it's wiggling slower so it's lower energy longer wavelengths so it's lower momentum and it has a bigger angle you can see it going back and forth between the top one and the bottom one the angle to the maximum

for the low frequency long wavelength wave is higher than it is for the higher frequency higher energy higher wave vector higher momentum wave of course that all works in two Dimensions as well if you shine a wave through a crystal you get Maxima at these Maxima and two dimensions and here's the straight through one down here and here's one where in both directions things add up

right and in 1927 just four years after de broily said matter was waves the people at Bell Labs went and made a wonderful measurement made a big vacuum Arrangement had an electron beam and and they found out that sure enough here's a Electron Beam that has 65 volts that's 65 electron volts of energy per electron and so the electrons bounced off the planes in the crystal

and the maximum one of those bright spot maximum at 44 degrees but if they lowered the voltage down to 54 degrees then they found that spot went out to 50 degrees sure enough work just like you'd expect for a wave that had a momentum which was how many waves there are per unit distance and at a energy which was the frequency how fast the thing wiggled

well 50 years later there was a amazing experiment done and I want to tell you about experiments that were done in the 60s and 70s because the people that made up our great theories didn't see any of these and these experiments tell us how the waves work we already saw the first one that said that the energy of the wave changed its angle in just the

right way this experiment a little bit harder to explain but let me go through it because it's such a fundamental experiment we'll need to understand it this is a single Crystal silicon which you could get in 1975 and they cut out chunks of it so that you had these three fins sticking up and the fins are just thick enough so a neutron that's coming along Neutron

wave would have a straight through path here that was the center spot that we saw and has a spot off to the side the diffracted spot that goes off at this angle and now we have another part of the neutron this is one Neutron at a time so the neutron wave splits into two it's still the same Neutron nothing funny about that if it was a

particle that would be terribly terribly disturbing it's not it's a wave you can spread out if it needs to this one felt like it so here's the part of the neutron going this way and now it gets diffracted again and here's the straight through path and here's the diffracted path so I have that path ACD ends up at this spot on the right and there's another

path the neutron goes straight through here and then diffraction this one a b d and they both add up here at Point d well when they're adding up they're either going to add up together in Phase means they're twice as big or they can cancel out each other when they're out of phase so the counts you get out here in these counters are going to reflect

how the waves are adding up in or out of face and now the trick here which was so beautiful this whole thing is bounded in a metal box of all nice and rigid so that you can rotate it around this axis shown here at with the angle Phi and when you do that you're in the earth's gravitational field if you turn the thing clockwise like it's

shown there this part of the path up here CD is going to be higher in the earth's field than path a b and so the neutrons are going to have the ones that are diffracted here are going to have to climb the hill of gravitational potential to get to the level up here at CD well if they're going to have to climb the hill their energy

is conserved and they have a kinetic energy coming in that's why they're waving fast so if they're going uphill they give up some of that kinetic energy and turns into potential energy so the gravitational potential higher up is higher that means the kinetic energy is lower which means it'll have a longer wavelength so it'll get out of phase with its partner that came around ABD as

you gradually rotate in the earth's gravitational field you see the waves adding up in Phase here and out of phase here this was a fantastic experiment it directly shows that the neutron wave has as a part of its momentum the gravitational potential and that's a thing we will see over and over again now it gets better than that if that was all there was everyone would

say that's obvious but that's not all there is let's take this path here you have two paths the neutron splits into so there's a path going around a c d and a path going on a b d suppose I kept them flat with respect to the gravitational field but I rotated them well if it's the whole thing's rotating then the neutron the half of the neutron

that goes ACD has got further to go because it's got to catch up with d because it'd be it moves a little bit and the one that's going this way D is Come a Little Closer so this one will take less phase delay and that one will take more so there should be a vector effect well what would the vector effect come from well if you're

in the frame of reference of the neutron there's a big universe out there and the matter in the universe the effect on the potential goes like one over the distance but the amount of matter goes like the square of the distance so the effect on us of matter out in the universe gets bigger as the matter is further away so most of the matter that affects

us here when we do our experiments it is very far out in the universe well they did that experiment how are you gonna arrange it so that you can rotate it so smoothly it's got a big effect of the Earth's gravitational field how are you going to get rid of that well what they did is they mounted it on a post like this and they could

still turn it around if the perpendicular here to this a b d c plane is got a projection on the rotation of the earth you just let the Earth turn it around that's nice and Steady As It Gets and if you have it turned one way if the perpendicular to that plane is aligned with the rotation Vector of the earth then you'll get a phase shift

in One Direction and if you turn it 180 degrees so that perpendicular is anti-aligned with the Earth's rotation you'll get the opposite phase well they did that and here it is right here if you point the the vector North it's aligned with the rotation of the earth and you get a positive phase shift not quite a full cycle but it's 100 degrees and if you point

to saying West then the thing is just goes around but it doesn't rotate so it doesn't register any fascia and then if you have a thing back up the other way then it's rotating the other way as the Earth rotates relative to the distant Universe in fact in a very rough way we've established that this Neutron wave the vector part that's directional knows where the universe

is well that's a direct message from the neutrons it's telling you it's making its law evident not many of us can afford a source of neutrons and the the setup itself was pretty complicated so we're not going to have one of those in a freshman physics lab but there are things we could do in a freshman physics lab that tell us just as clearly what the

wave nature of matter is doing now you've all seen pictures like this first thing you learn about electricity is you take a battery has some voltage and you hook it up to a chunk of something or other and uh it makes a current go through there and the current is proportional to the voltage divided by the resistance of the stuff so it resists the electrons flowing

and that means the velocity of the electrons is linear in the electrical field electrical field pushing on them and they go at a distance that's thousand year old thinking that's the way they used to think mechanics worked you had to push something along to keep it moving and it wasn't until Galileo had his nice marble slabs but he showed that it still had its kinetic energy

that came from the potential energy of letting it roll down a marble slab so what have you done to the electrons you've put them in something that completely scatters their wave nature makes it all random and so they can't propagate in a nice way that electrons want to do unless you mess them up so a horrible way to learn about what electrons are like the electrons

should its acceleration should depend on the electrical field not its velocity well turns out that's what happens if you make an environment for the electrons that doesn't mess them up that was first done in 1911 in Leiden just a little town south of Amsterdam and a guy by the name of cameronis and he was dutifully measuring Ohm's law here here's a resistance in almost that's how

oh my god there and that's very low you can see it's a 0.15 of an OHM this is a wire of Mercury Mercury of quarters liquid metal at room temperature but you can make it in the shape you want and then cool it and turns into a solid so it's very convenient to use for low temperature measurements because you can make any ring shape you want

and he noticed that he was coming down here cooling he was the first guy that figured out how to liquefy helium which happens around four degrees absolute and so he was bumping on his helium here making it colder and colder and bang the resistance went away well of course he figured out it something in his setup had broken the whole voltmeter wasn't hooked up anymore and

so he was hunting around trying to figure out what had gone wrong and the process he wasn't pumping so much on the helium and it started to warm up a little bang the resistance came back well he's a smart guy so he said if I can go back and forth reproducibly that means it's a real physical effect but it gets to a resistance which is way

lower than anything I can measure so what do I do how would I find out what it is well a smart smart guy he said I'm going to take the Mercury and I'm going to make it into a ring this ring here it goes underneath this apparatus here so that's a continuous ring of mercury that any cool down and he reasoned like this if I can

get a current started in the ring it'll make a magnetic field and I can tell if there's a magnetic field there by putting a compass down there their ordinary old-fashioned magnetic compass so he did he got the thing superconducting he got a current started in it and the compass went from pointing North here to pointing East and he expected it to die out within seconds or

maybe minutes he kept pumping on his helium overnight and it was still going just as strong the most significant physical experiment ever been done this is perpetual motion never been anything like that there to this day isn't anything like that it's a perfect frictionless system people puzzled over this and in a couple decades later the London Brothers said it must be a coherent Quantum system a

macroscopic Quantum system because that's the only way it could work because if it's a Quantum system it's a wave and the wave goes around and it has to come back in Phase with itself so unless you break it and there's 10 to the 23 electrons in it and so the little thermal Wiggles that happen at four Kelvin aren't going to do anything to something with 10

to the 23rd electrons in a coherent Quantum state macroscopic wave of matter unbelievable this teaches us about matter waves in a way that nothing else we've ever had can do well it took another 50 years it's astounding this is an experiment onus could have done and didn't think of it there's a group in Germany and another group in Stanford here in California their findings were published

in the same issue of the journal physical review letters 1961 and what they did is they had a this is a little ring they used lead leads a good superconductor too they found a way to trap a current in it when it went superconducting and then once it had a little current in it instead of using a compass well a compass a big clunky thing but

you do the other thing you turn the little current thing you hang out on a spider web so that it can rotate with a very little bit of force and you put a very weak magnetic field on it so you've turned the sample itself into the needle of the compass so it's not so different from onus's measurement and uh how much that angle changes as you

put the little very weak magnetic field on from outside tells you what the Magnetic Moment is well what's a Magnetic Moment well this tells you in a way that's evident the Magnetic Moment is the wave comes around in Phase with itself well that can be in Phase with no f phase change around the loop or with one cycle phase change around the loop or with two

cycles crazy that's what these are [Music] the flux is quantized the Magnetic Moment is quantized what that is is the wave vector of the electron condensate this magic perfect frictionless phase of matter the phase comes around and it must come around in Phase with itself and that phase is quantized so this is where the term quantum comes from it's the reason that that energy levels of

an electron a single electron in an atom comes around in Phase with itself and that gives it can be one phase zero no electron can't be zero because it's got this complicated thing called spin that we still don't understand very well so all of the quantum levels of things come about because matter is waves and the waves have to come around and phase for themselves well

that last experiment could have been done by camera link onus and you can certainly do it in a freshman physics lab here's another one you can do in a freshman physics lab the London's predicted if you had a ring of superconductor and you spun the ring you would get a magnetic field what in the world is that about here I have this fictionless stuff and it's

in a ring that has positive charges because of course those electrons came with atoms that made the ring and they just happen to get free and gang up and make this wonderful condensate and that's fictionless thing but there's still a positive charge is there so when you spin the ring you have the positive charges go around well now if the electrons that go exactly with the

positive charges they wouldn't be any current because electrons going that way would be a negative current positive charge that's going that way it'd be a positive current they cancel out but that's not what happens as you spin this ring faster the magnetic flux gets bigger what in the world is that about I have a perfect electron condensate frictionless and it's got no flux in it no

twist in its wave function as it goes around so the wave has same phase all the way around what's in the world is it doing that it becomes a magnetic field well think about it this way if I start the ring rotating I start the positive charges the electron condensate is a free-floating thing but it feels the magnetic Vector coupling with the positive charges going around

so it has to speed up to keep up with the positive charges well you would think then it's perfect so it ought to just keep up perfectly what doesn't it lags behind so as you accelerate to make the ring spin it has to accelerate relative to the universe so when you're not moving you're not spinning a ring relative to the universe there's no magnetic flux the

electrons are perfectly lined up with the positive charges but when you spin them there's no mechanical complaint though the condensate is a perfect thing but it's charged and it has mass it has the quantity of matter that couples gravitationally so this is a perfect experiment that has the vector coupling of the positive charge is moving which we call magnetism and it has the vector coupling from

the point of view of the electron condensate it's the universe out there going around so it induces what we call inertia in the matter and here's a perfect example where there's no friction to get in the way and this can be done in a freshman physics lab well those are experiments that make the law evident what about light lights just matter wave one place that's charged

talking to a matter wave someplace else that's charged maybe it will have some coupling to gravitation it's funny Einstein struggled with this question never quite settled to the end of his life in 1911 he had a wonderful simple clear Theory where the velocity of light was a function of the gravitational potential interesting then in 1915 he crafted with a lot of help a very much more

complicated and very much more obscure theory of gravitation called general relativity general relativity has two things it has an equation uh a sort of wave-like equation for the gravitational potential which is reasonably easy to understand if you take the simple case and it has a stipulation that you guess what function light speed is of the gravitational potential and that's something you have to put in in

addition to the theory it's just a the math doesn't tell you that you just have to guess it well he changed his mind and he guessed that it was going to be independent of gravitational potential and that statement that choice has doomed us to work in curves face time ever since so if you put matter in your space a meter isn't a meter anymore it's a

nightmare you can do it the smartest people of the world I know I've conveyed that work but you have to change the coordinate system in order to do it from the coordinate system that says light is constant speed no matter where you are in a frame of reference which isn't accelerated or rotating well I'm an engineer let's do the measurement Erwin Shapiro in the late 60s

was it MIT and they had a an old radio astronomy antenna there that wasn't used very much it's called the haystack Observatory and he was good at doing experiments so he got put together a real high power radar yeah the antenna you shoot out a microwave signal out of the antenna and you'll wait for an Echo to come back and he got good at getting Echoes

from Mars and Venus well Mars and Venus have their inner planets so they have faster periods in the earth and so when we watch them they occasionally Go real close to the Sun and so when they do uh he measured the delay and there's this huge increase in the delay when the radar signal goes next to the Sun and guess what it's exactly the form that

you would calculate if the speed of light was proportional to the gravitational potential very interesting now you can either calculate that curve the hard way by assuming the speed of light is constant and then changing into a coordinate system where it's doing what it's doing really and physically or you can just say I'm going to work in a system where it's doing what it's doing makes

everything a lot simpler so we've discovered that light has an effect on gravitation or said the other way gravitation has an effect on light this is a scalar effect it's a gravitational potential changes the speed then if all is like the neutrons should have a vector effect well guess what right now inertial navigation is not done with old mechanical hurling gyroscopes anymore it's done with fiber

optic gyroscopes because you can start light this is a wonderful device you start with a laser and this thing called B here is a beam splitter it spits half the light 45 degrees and the other half goes straight through so this beam comes in it goes up half of it goes up half of it goes straight so now we have two halves of the light beam

going in opposite direction around these many turns of the coil and when they get to the other end they come back and they combine here the one from the top goes straight down the one from over here bounces off and goes down and so they add up as a detector just like the neutrons did and guess what you get a really nice pattern an interference pattern

if you rotate this so you can buy these things here's a commercial one that has one coil of fiber optic it's just what's shown here and this is a complete three axis gyroscope so it has three of these things and mounted on three orthogonal axes and so what you can do is you can put this on your the mounting surface of your astronomical telescope and it

has motor drives so you can tune the motor drives until all three axes read zero and then you go look through your telescope and the distant galaxies are stationary don't try to tell me that's an accident that's the vector coupling of the distant universe well you've all been told [Music] that there is no preferred frame of reference and that's just wrong looking at the experiments it's

clear there is a frame of reference and that's the distant Mass from the universe well then how can special relativity work Einstein made very clear if you're moving in a straight line not rotating and not accelerating you can be any velocity in any direction and you get an equivalence in the results that you get in a local experiment how can that possibly be true when we're

moving in a vast potential of the universe well let's look at the universe we're living in an expanding universe and by now we know a lot about that by observing one of the things Hubble figured out in 1922 is that the things furthest of away are moving away from us the fastest that Hubble's Law well if you take that literally you go further and further and

finally you get to where they're moving away from us at the speed of light well that means that we can't see them anymore I can't get back to us and gravitational interaction can't get back to us that means that all cosmologies have a horizon it's that distance when the stuff is moving away from that velocity of light well what does that actually mean well what it

means is if I look in any direction that stuff's moving away and it looks like it's for this stuff is moving faster so suppose I'm moving towards one of the Horizons in a straight line not accelerary it means that Horizon moves away from me I'm catching up with the matter so the Horizon moves away from me and the one behind moves it so it means that

the effect of the universe as long as it's pretty much the same Beyond the Horizon as it is this side of the horizon it means that if you're moving at any velocity The Horizon just moves around a little bubble with you that's why special relativity works it's not just a mathematical thing it's physics in it coupling with the universe that's moving away and most of it's

moving at near the velocity of light then you get that the local experiments don't know about moving in a straight line because the universe that you can feel and see moves with you it all makes sense it's a way of thinking that makes a law evident so let's think about the history of the universe it started out much denser than it is now and so it

had a lot of kinetic energy otherwise it wouldn't be continuing to expand but gravitation is an attractive thing so it means that to separate matter takes energy so as you're separating the elements of matter like they have little rubber bands between every two elements of matter and as you Universe expands a stretch in those rubber bands is that gravitational potential due to the attraction of all

matter with all other matter within the horizon that's the potential of every element of matter guess what Einstein said the energy is MC squared that's the rest energy of matter 100 of that rest energy is gravitational potential and every element of matter has inertia you have to put energy into accelerate it 100 of that inertia is a gravitational Vector coupling so if we just take what

the universe is telling us the fundamental laws are evident now I'm talking to the young people here today you won't hear this very many places but compared with wading through the layers and layers of opaque mathematics in the three great theories that are out there it's vastly easier you can do everything I've talked about today with trigonometry and first-year calculus you're the ones that can find

a new way of thinking and turn it into a real theory that makes real predictions one of the things you'll find right away as you see questions that make sense in this way of looking at it that you can't even ask in the traditional theories to try to find something new to do with the traditional theories 100 Years of the smartest people in the world working

on them they've worked most of the problems not much left for you to do you look at things in a new way there's a huge number of things we don't understand but the big theories Shield them from you in quantum mechanics when you ask about well what makes the wave function collapse they say oh you can't ask that question I remember being told that when I

was an undergrad I said what do you mean I can't ask that question I just did well you could ask questions you can become leaders in learning about the results of looking at physical law Through The Eyes of these wonderful experiments that make the laws evident so go out there and do it bless you [Applause] [Music]