G4v: An Engineering Approach to Gravitation - C. Mead - 4/21/2015

presented by Caltech when we start I would like to welcome you to today's schedule where seminar it is my pleasure to introduce our speaker today is Carver Mead Gordon and Betty Moore professor emeritus of Engineering and Applied Science here at Cal Tech Carver is one of the pioneers of modern micro electronics and his work underlies most of the technology we enjoyed today including your cell phones and computers Carver founded Cal Tech's own computer science division he worked with Feynman and hob field in neural networks and the physics of computation for all his work this is just a little bit it's impossible to list here his almost infinite accomplishments well because of all of that he was awarded in 2002 the National Medal of Technology Carver also is known for coining the phrase Moore's law which is very funny but he's not going to talk about any of that today he's going to tell you about his ideas about gravity so why don't you show join me in welcoming Carver thank you max it looks good to be here and a Jaguar seminar I um I always thought that was such a great name for a group and a group with that good a name it seems to me should have a logo so I think you should have a competition for the best logo for the cat Jaguar group and since I'm giving a talk today I thought maybe I can put in a couple of early entries so how many here think that one on the left is the best logo maybe three four okay how many think the one on the right is the best logo okay well the one on the right is got it so far and then from now on you're on your own with the rest of the of the competition when we were in grade school or high school we all learned about the two great forces the long-range forces gravitation and E&M and everyone since has been struck by the fact that they're of the same form but of opposite science and what could that possibly mean and could they be related and that's been a recurring theme down through hundreds of years and then you'd have force laws but what good are force laws so there's a force so what good does that do well we're told that Newton said that a force is a thing that changes the momentum okay I guess so we have the two great forces charges attracting each other and massive bodies attracting each other and those forces are supposed to change the momentum of bodies and we've had this beat into us since we were young enough that I can't remember where it came from or what it means we just have it deeply embedded in our psyches so here we are here's here's the thing with momentum and at some point a little guy there pushes on it and applies a force for a long time and the little vehicle gradually gets faster and faster and faster and finally the guy lets go of it doesn't push it anymore and the velocity keeps it just going well that wasn't Newton that was Galileo figured that one out so already we can see there's a little funny thing going on but that's a very old idea and this is all grade school stuff so what's its there any thing more modern that might have something to say about this well here's the thing with inertia and it doesn't look at all like that little car it's a superconducting magnet it's one that I use in a lab it's about two inches across here and about three inches long and it has two wires and between the two wires all wrapped up in that cylinder there's about a kilometer of superconducting wire and the wire has about 10 to the 20th electrons per meter in it so it's a pretty simple thing and if you do the experiment on it you come along and you apply a voltage to those two terminals and you leave it there and you notice that the current which of course is the movement of the electrons goes up and it goes up in a nice steady way just like this was a thing with inertia and then if you take the voltage away by for example putting superconducting short across the two wires then the current just keeps flowing and as far as we know if you do it well it'll keep going the limits on it are very low and still haven't reached where we can actually measure so this is a wonderful inertial system and it's nice to think about in the context of electrons instead of some vehicle with wheels that's right so let's just do a little engineering calculation here since this is an engineering approach I'll see how much force are we applying to each electron well a force per electron is a charge on the electron times the electric field the charge on the electron we know that's this thing over here the field are just a voltage divided by the length we put a half a volt on it so it's half a volt over the length which is a kilometer so this turns out to be 10 to minus 22 Newton's on every electron okay that's just a nice small number well how about the current well the current is the charge on the electron times helmand or there are per meter times how fast they're going in meters per second that's now charged per second which is amperes and with if you put numbers and it turns out to be 16 times the velocity and meters per second gives you the current in amperes so here we are we started down here and we waited for 40 seconds to get these 40 amperes of current and at 40 amperes is two and a half times the 16 there so now we go down here to something that gave us the inertial mass of this system will be the force here divided by a DV DT over here and when you put that in you get one point six times ten to minus twenty-one kilograms and you say oh yeah lectrons are light little things they are light little things a free electron has a mass of 10 o minus 30 kilograms so then of course you go back you say oh I left something out no you didn't leave anything out the inertia of those electrons is 10 to the 9 times the inertia of electron out by itself well that's cause for pause I should remark in passing that our whole electrical technology depends on the fact that the electrons in electrical machinery have vastly more inertia than they do if they're just little things out by themselves we wouldn't have any of our electrical technology today of that we're not true well let's look a little closer at what's going on in there because it'll help us there's as we said the kilometer of wire with ten of xx electrons but the part that nobody knew back in the old days was that when the electrons go into a superconducting state they make just one big quantum wave function and as long as you don't mess with them too badly it behaves just like a system with one degree of freedom it's like saying I can represent a mass by the properties of its center of mass well the wave function has some envelope that envelope is just the thing that keeps them in the wire and then it's just a propagating wave it has a propagation vector and it has a frequency frequency related to its energy which for in this case is related to the voltage on particular point in a wire and the propagation vector related to its inertia well we're used to electrons being wave this is a particularly nice diffraction pattern that was made by taking a nice collimated beam of electrons and putting it through a very thin crystal and we're reminded that this whole thing started with Max Planck who said that somehow the energy was related to the frequency and gave it a constant and then de Broglie came along 13 or 14 years later and said well if that's true so momentum must be related to the propagation vector then shortly after that Schrodinger came through and said no you left something out the momentum is really and by momentum here he means the mass times the velocity is equal to what you said Debray Li minus the charge times the vector potential so in addition to having a scalar potential it causes these things to attract each other you have this vector potential which interacts only with things moving with respect to each other well that's interesting so let's look at what's going on in the superconducting solenoid it has a current here and that current is just a charge of the electron times how many there are per unit length times the velocity this is what we did before we didn't do is to see what the wave function is doing it has the propagation vector minus the vector potential well what's the vector potential well lo vector potential is proportional to the current which is proportional to the velocity and it's this big integral the current here where it's sensing the vector potential the vector potential is just adding up all the little currents everywhere dividing by the distance they are away and making a single resultant vector out of that that's all it is so this term here the QA part is proportional to the velocity and it's minus which means the harder you push on the thing the more it fights back so there's a built-in feedback loop whenever you have these coupled systems there's a built-in feedback loop that makes the thing that's interacting have a very different inertia than it would have had if it wasn't interacting with other things so that's the big lesson for that we can take away from enam is that you couple a bunch of these things and it really affects the inertia a lot can be huge in this case it was a factor of 10 to the 9 more in the coupled system that would have been in the individual electrons well that's interesting so a lot of people thought about this this is Einstein Einstein in 1912 you can see right here on that make sure I hunted hard to find this picture and you notice he's a very sober very pensive Einstein now why is he so sober and so pensive well you know he had a great year in 1905 he did special relativity and Brownian motion and you know things that people remember and right after that he started working on gravitation the first paper he published on that subject was in 1907 and he struggled with that for four more years and then he wrote his next paper which is actually my favorite of all of Einstein's papers and it was on the influence of gravitation on the propagation of light it was based strictly on the equivalence principle and just using that he reasoned his way to the fact that the speed of light must depend on the gravitational potential it's a wonderful paper and we've gotten a retranslation done in the last few years that's clearer than the original if anybody's interested I can give you the reference to that it's on the web in this paper he made two absolutely remarkable predictions he predicted there would be a gravitational redshift that clocks of any kind would run slower when they're near a massive body and he predicted that light would be deflected as it went around a massive body it turns out we consider these today two of the great triumphs of general relativity this was five years earlier than that so let's see how it works with Einstein's theory his early theory he said that the velocity of light is the velocity out in our part of the universe but not near any local massive bodies so it's sort of the average of the interaction with all the rest of the universe times 1 minus GM over RC squared are being the distance we are from this local massive body and GM over C squared comes up so much we're just gonna call it Delta for now so it makes that well what's the resonant condition for this resonator this was Einstein's favorite clock just two mirrors and light bouncing back and forth between them well it's an integral number of 1/2 wavelengths in the length well K times the length is the total face so that has to be n times pi wavelengths and K is equal to Omega over C that's just because light is non dispersive so that says that the frequencies gonna have this standard constant out in front which you think was constant and it's lessened by this Delta factor so in this theory that he put forth the lengths did not change with gravitational potential gravitational potential is representative are represented by the speed of light and if you work it out this way it turns out that this works for atomic clocks and it works for nuclear energies and all those things this was not observed until 1960 nowadays clocks made with resonators like this are good to a part in 10 to the 16 and a couple of years ago was demonstrated that if you took one of these clocks and synchronize it with another one and then jacked it up one meter you could easily distinguish the frequency difference so we're getting to where we can see effects that we could only dream about in Einstein's age this is one of the dreams he had that turned out to be right on well he also talked about the deflection of light you can see how that works this is just another little engineering calculation it's not as complicated as it looks we say the light's going to propagate from this point over this path down to the other point along this path and it's going to go some distance D from the massive body and our job is to figure out what D as now we know that the curve isn't exactly this what is not far off the difference between this and the actual curve do it old a little curvature in there it's gonna be second order in fact so let's just find out if you take it too far out if you make a deep too big then the light has too far to go if you make D too small it's getting close to the massive body and the speed of lights getting really slow so it takes too long so there's gonna be a place in the middle where it's just right it'll take the minimum time to get there and that's one we're looking for well here's K it's the one we just wrote down Omega over C zero times one minus this Delta term well we can enter integrate that the phase is just their integral along the path of the propagation vector D distance propagation vector is 1 over length the distance is late so this is a unitless thing like a phase should be and you get what you'd expect you get a our term and an hour to term that's just the length if it went straight but then it's a little further because it has to go up and around so the D term comes in and it comes in a second order just like you'd expect and then there's the part over here we'll do to the slowing of C with the scalar potential and well okay now you take the derivative of the phase with respect to D squared it just because D comes in second order and you get this expression well Einstein considered the case where the since to the star was very long compared to the distance from the Sun to the earth because he was looking at the deflection of light that went around the Sun and so he said well this one over r1 term can be neglected so this is equal to that so D has to be 2 R to Delta and now the angle is just D over r2 so that's just this Delta term over the distance well you've all heard the middle part of this story about how this got the deflection of light wrong and therefore Einstein had to go and find a better theory well that's true but not exactly in the way you've been told well let me tell you what really happened Einstein in this paper in 1911 wrote this paragraph I think it is one of the most amazing predictions ever written by human being said lights gonna go past the Sun and be deflected by almost an arc second it's going to appear if it goes around a massive body to be further out than it really is that's what happens of course if the light bends this way and then he made a pleat of the astronomers please try to see this because when we have a total eclipse stars near the Sun are visible and independent of how much you think this is a crazy theory this is an interesting question that science done well as you know between that and the time there was a good Eclipse to look for this Einstein had gone off in done general relativity found out that gr predicts a factor of two larger and Eddington got funding for a expedition it was quite an ambitious thing they sent a party to northern Brazil and party to an island just off the west coast of Africa and they had enormous practical problems to get anything at all they got a few plates which were of quality enough to actually make this comparison and here's the data this is the prediction of his published 1911 paper this is the prediction of gr and the points or the data well everybody looked at that and said that proves the GRS right and off they went and never turned back but there's a postscript to this story that never gets told Einstein wrote just a year later wrote a very short paper in the most obscure journal you could imagine a journal of sanitization and health something or other and saying is there a gravitational effect analogous to electromagnetic induction this is my second most favorite paper probably should be the first but it relies heavily on the other one and in this paper he made three more absolutely amazing predictions he made the prediction that if a test mass was near a very massive body its inertia increase that if the little test mass was inside a spherical massive body with a massive shell and you move the massive shell the test mass would move with it albeit very slowly but it would have induced in it a fraction of the motion of the large massive shell the reason it was a shell of course was you had to get rid of the scalar interaction otherwise it would go roar roaring off towards it any mass insight and then the last thing which is the one I like the best is it provides you a way to imagine that all of the inertia matter is to do its movement relative to all the stuff in the universe which is an idea that moc put forward and Einstein fell in love with so here's the picture out of that 1912 paper and he makes these predictions just the way it expected flat out the way he got rid of the scalar effect of course was using this result from static electricity that if you're inside an equipotential thing then that 1 over R squared dependence makes it independent of where you are so let's see how it works with light if you include this vector interaction as well as the slowing of C with a lower gravitational potential well here we are K is just Omega over C but it also has this one minus GM over C squared due to the vector coupling remember K got bigger so it's Omega over C times this factor due to director coupling well C is already smaller due to the scalar effect on the speed of light so K ends up big this thing which is just Omega over C where it was out where there was no massive body and then 1 minus this little Delta term so the vector and the scalar effects and and because the things going at the speed of light they're equal in magnitude so the total effect is double so Einstein only had to write this one slide and he would have had it in 1912 that's how close he was so his predicted deflection is exactly what's observed and I don't have to remind you that this is arrived at in a very different way and the standard treatment you see so there's another aspect to this the top parts just what you've seen already but you notice that the little Delta term has doubled because there's the part from the scalar and the part from that the vector effect and remember when we computed it before we got this log term in the delay well if you work it out a little more carefully you get this logarithm in addition to just the distance divided by the speed of light out there you get this log term and you say well log terms are always smooth they don't do very much well I'll be careful if D is small this square root gets arbitrarily close to the distance here so this could get very very small so this log can get pretty big and we now call this the Shapiro delay after Erwin Shapiro who predicted it in 1964 he predicted it from general relativity and he had a heck of a fight on his hands to convince people that the light could slow down because after all I'm sitting you know my platform is in freefall and I'm transmitting a signal to another planet and looking at the at the reflection how could that possibly slow down well now everybody has worked it out with gr of course Merlin's a quite remarkable fellow he figured this out in 1964 and then he went and reworked the haystack Observatory completely put on new much higher power transmitter and a much more sensitive receiver and in the last part of 1966 he got his his first bounces off of I think that one was mercury I don't have the data from that one it wasn't very good but by the time he got to early part of 67 he was getting pretty good data remember this would all be totally flat it's the combination of the vector coupling and the scalar coupling that give you the magnitude you actually see so because it's light the vector coupling is a much bigger fraction of its inertia than if it were matter which has a built in mass by 1970 or win' had things working much better and you can see this wonderful wonderful example of the Shapiro delay this time it was with Venus and they got a a nice close superior conjunction so I was able to nowadays this is a binary pulsar that was relatively recently found and identified and it has the great advantage that we're looking at it almost edge-on so when the pulsar is orbiting a white dwarf here the beam to earth comes very very close to the companion and you get this wonderful wonderful big peak which exactly fits that expression that I showed you it's wonderful that expression was another thing he could have had it 1912 with the factor of 2 so what we've really been saying is that the electricity and magnetism taught us that there's a scalar potential which is how charges interact with other charges and there's a vector potential which is how moving charges interact with other moving charges well what's different well the scalar potential for gravitation has the opposite sign so like things attract instead of repelling and the same is true for the vector potential which means if you started out with a little element of matter that wasn't propagating and you move the shell around it the matter would move with it because the difference has to be zero well the frame of reference issue that was brought right to the fore and predicted by the 1912 paper wasn't really found experimentally in its pure form until well the experiment was started gravity probe B was launched ten years ago and we didn't have the final report until three years ago or for what it was was a little free-floating test mass in this case it was spinning and it was in orbit around the earth now they always draw it this way and I think that's a bias that's put on my gr because uh this little ball is in freefall its coordinate system is absolutely as good as anybody else's coordinate system so from its point of view which is the only point of view you carry about because that's what you're measuring the Earth's going around it in a big circle so it's just like Einstein's shell if you move the shell the mass moves if you'll rotate the shell the mass would move inside it's a very small effect because this mass is much less than the rest of the mass in the universe but that's also a little more complicated because this is the magnitude just straight out Einstein's 1912 proposal for this one because the the little test mass is spinning there's a spin orbit coupling it just turns out to be half as big innings of the same sign so you get three halves of this value and the total is called a geodesic effect even though the two effects that you add together are quite different this this one would go away if the little gyroscope for not spinning but the other one would still be there so this experiment would have seen 2/3 the effect if the thing had not been spinning problem is that the spin of the gyroscope was what gave the London moment which allowed the position to be determined very precisely so could do the experiment that way this was a marvelous test a pure test of the vector coupling and we didn't have it till recently I think Einstein would have been very pleased by this well once you know for a fact that there is a vector coupling and you know its magnitude and you believe that the vector and scalar effects are related as a four vector in a region where there's not a big gravitational field you realize that the ratio of these two effects is C squared and the fact that when gravity probe B results were published they were published as agreeing with G R really means that this was the C that we know and love so that means in my book there must be propagating solutions at velocity C and that's the first time that I personally believed it I wasn't at all sure that that's what we'd find I'm delighted that's what we so that brings us to why we're here the vector potential is a propagating solution it depends on the momentum at some time earlier than we're looking for it and it's a 1 over R potential and it has this G over C squared in it so it looks a from the propagating wave perspective it looks exactly like an EMM way the sign doesn't change anything because half the time the mass is moving one way and the other half of the time it's moving the other way so all that is is a phase change so you can think of this as just a different form of electromagnetic wave already at this point by just writing down this green's function we have made a prediction that's different from gr i was when i first started getting into this i was very concerned that what i was coming up with was just a sort of a poor man's rendition of gr so of course I had lunch with Kip Thorne right away and said hey tell me if this is all well known no no no is it this is interesting so that's when I started talking to max and allanon and getting serious about gravitational waves and you can see here because this is just a green spot it's Jess the momentum vector by this time well for a binary system one Momentum's always to equal an opposite of the other one because they got nothing around to put the other momentum to so that tells you immediately that if you stay on the line perpendicular to the orbits where the distance between the two is equal the vector potential you will get is zero we can work it out I worked it out here for a circular orbit it's just a little simpler you can do the eccentric orbits they're just more complicated but this is looking down on the orbit here's the two masses equal and opposite momenta and then you're going to look at it at some inclination angle I hear or iota and so we're at way out there someplace and if we're out in the Y direction you can see here that according to g4v there'll be no radiation whatsoever according to GR there'll be a maximum and there radiation so now we know for sure that isn't just the same theory warmed over this is a strong prediction there's also a slight difference in the total radiation from a binary system a Kepler system that has eccentricity that epsilon here as the eccentricity and it turns out the calculations couldn't be more different but when you write them down this one was first written down by Landau and Lifshitz ed later works on pretty heavily by Peterson Matthews here at Caltech and so this is taking a Kepler orbit that you would get just from Newtonian gravity and then using that to calculate the gravitational radiation and when you do that all this stuff is the same and then there's this eccentricity dependence which is very slightly different for g4v that it is for GR and so of course I want to look into this because it would be really neat if we had a good test case well unfortunately almost all the test cases we have are very low eccentricity the pulsars are of course the place you look for this because they're stable enough to really see something we have one good high eccentricity pulsar and that was the first one found in a binary so we were lucky and here's the integrated time difference over the ten years or so since we've been observing it and you see it looks like it fits within very small factor of G R in fact it even says there G our prediction so of course I had to go look that up and figure out what's going on and it turned out that if you look at the data actually coming in referred to the solar system barycentre it matches G for be better than it matches gr but it has to be corrected because it's thought that the part of the galaxy where this object is located is accelerating relative to the solar system very Center I have no expertise in deciding if that's true or not but it's a pretty big correction percent and a half or so and that makes it match with gr better than with t4v I do know one thing and that is both of these expressions come from pure Newtonian Kepler orbits and those are just not right I've worked out pretty good approximation to the corrected orbit in G for B and there are corrections that look like they might be of this order but I haven't gotten good enough to get down there yet so that's work to be done in any case I would say the jury's out on this one I would really love to get a high eccentricity system that's close enough to earth that we can do a long race line interferometry on it and find out if it's accelerating find out really where things are we don't have one of those yet but the astronomers are busy and now there's another way which you would expect from now that g4v is different from gr and that is in the detector remember that the vector potential here is just if you had a little free-floating mass point and you apply to vector potential by like moving at shell Alliance dies the vector potential is just the speed that would be induced in this little free-floating matter well that sounds a lot like a gravitational wave detector so let's look at what it looks like these are free-floating objects massive objects not very massive objects here's a gravitational wave coming along here propagating in the direction R and here's the vector potential it's down here up here down here and so forth so as this wave comes by these two little masses they pick up a velocity due to the vector potential and they're both moving down the same velocity so the distance between them doesn't move okay that was a strikeout well let's put them along the direction of propagation okay now they move in opposite directions one down you know there's up but remember these are very small motions we're looking for you all know just how small the motions they are that we're looking for and so this will be a second-order change in the distance between them not the way to make a detector when I originally started working on this problem I thought that I had a way of showing that it wasn't going to work but one last attempt I actually worked out what the dependence was and of course it's the product of the dot of the cavity onto the vector potential with a dot of the cavity onto the direction of propagation so if either one is zero you get zero but if they're at 45 degrees you get a very nice very nice response this one goes down and that one goes up and they move apart very nicely so you see that all the antenna patterns have this very nice Maxima out at 45 degrees in case of the other polarization the maximum is out 45 degrees in the vertical direction and once again there's zero perpendicular to the plane of the detector and for gr there's a maximum there so max here and Allan have worked out a very nice way of actually seeing if this is going to be detectable as you know we have two of our very own legos went up here at Hanford Washington underneath that cloud and one down here in Livingston Louisiana underneath that cloud and of course as the Earth spins around those antenna patterns are scanning the sky so if you had a pure wave coming in there's this one polarization you'd see this dependence with time of day and you notice it has sign changes and that's in the kind of coherent detection we do you can see the sign changes quite well so well it's still you look at it and you say well it looks like it might be different but this thing looks a whole lot like the upside down saying and well max went and worked out for the crab pulsar which is a highly likely thing to be giving us gravitational waves and he said okay if I put in a synthesised gr wave and look at it with a gr matched filter of course I'll get more output from the filter when I put a louder wave yet if I look at it with a g4v filter you have to be awfully loud to see anything at all so they're highly distinguishable and vice versa this is if I look for Ag for V wave with a g4v filter and if I look for a G for view a with a gr filter well until this work was done people were looking with this green filter so if we'd have had a really loud G for every wave we would deceit it there's a whole new light coming up now and we all hope we see a lot of things Maxon allan also worked out a very nice way that's agnostic as to the theory of gravitation at any polarization that could possibly be present will be detected and the penalty of pay in sensitivity is not much at all so that was a beautiful piece of work built into the LIGO library down well here's here's Einstein everybody said he had a wonder year in 1905 I personally think my personal wonder year from Einstein was a summer of 11 the summer of 12 was an absolutely amazing thing he predicted these post-new things gravitational redshift the slowing of light with gravitational potential deflection of light with a massive body an Ursa due to an object being close to other massive bodies and the vector influence on the frame of reference the fig unfortunately the only one that was done in time to be absorbed in any of this was the deflection of light and in many ways it's the hardest from our present perspective with our present radars and our present antennas that pick up pulsars that's the hard way to figure out the speed of light out there and how it's affected by the gravitational potential the Shapiro delay is a much much easier way to do that so what's Defour V well g4v is a continuation of einstein's early gravitation in 1911 1912 work just putting in the context of electromagnetism and what we've learned about that finding a clean way of representing it treating massive objects with their wave functions which of course wasn't known at all when all of us theory was put together and the coupling here is this think a zero that's the Compton wave number and that's the thing that stays constant when you change the speed of light and a representation at all particle physicists know and love when you do the coupling this way you don't need a force law so there's all sorts of arguments why you can't do a theory this way because it does work where the force loss we have well you don't need a force law to do this sometimes handy but you don't need it so the good news is it works with all the tests of gravitational theories that have been done it's in violent disagreement with respect to both sources and detection of gravitational wave about as far off as you could get and the things I like about it in addition are it naturally encompasses machs principle that inertia comes from any interaction with other stuff and that's true of electromagnetism and it's true of gravitation and that means that all of our local physics has a cosmological origin now cosmology is a big subject and this is how obvious or not to place to do it but I have done a little try cosmology and the surprising thing is you can do a very simple cosmology with very few assumptions and you get a consistent cosmology namely the machs principle integral form of the cosmology agrees with the differential equation formulation and when you do that you get a value for the energy density in the universe and it's about a factor - higher than you get from the standard lambda-cdm models and it works without dark energy in fact it's agnostic as to what form of energy there is whether it's matter or other stuff what kind of matter doesn't matter it's just energy so I think Einstein's 1911 1912 thought process there worth following whichever way it comes out it's gonna be decided it's going to be decided right here with this group Jaguar will bite so good luck with that we will take a couple questions and then there will be refreshments outside I'm sure Kara can stick around yes they're g4v is inherently an integral formulation so there's no there's no equivalent fudge factor to to play with it's just you add up all the stuff that's out there take one over R and that's what you have yeah there's there's no equivalent thing and it's a good thing because it wouldn't work if there was it it's one vector but people because it's a transverse vector people typically break it down into like if you have a binary system they break it down into the the vector in the direction the thing is rotating and the vector along the inclination Direction it's just habit it's just what people do so I broke it down into those two things but really at any one place it's just a vector varying with time yeah there's lots of lore for waves like this there's a lot known it snowed no different than the antenna pattern you get with standard Maxwell's equations it's just a lot easier to get when you use a green's function than it is if you have to go through all the matching boundary conditions and all that stuff so as a matter of fact I um I spent 10 years of my life doing E&M over again just because it's so much easier to do and that's for any of you're interested in this it's in this little green book and that was what got me started doing in MO ver because I was interested in this line of thought that Einstein it had gone down and I realized that no way with Maxwell's equations is there anything going to be obvious and it better be pretty obvious if you're going to believe it so that's why I went down that vector potential path and it's amazing to me how much easier it is especially for antenna problems yeah it I don't know enough gr to answer that question a hundred percent I've seen it applied to the radiation field of gravitational radiation and as you could see this kind of a theory gets a different polarization than I yeah yeah so I've never I've never understood how far it goes and and what it's really good for and I do know that they start with Maxwell's equations like things and of course that makes it ten times more complicated it has to be and also leaves you with some some dangling constants like you pointed out so let's think Carver again you

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Keywords: Caltech, science, technology, research, Carver Mead, Gravitation (Literature Subject), Computer Science (Field Of Study), Engineering (Industry), Physics (Field Of Study), innovation

Id: XdiG6ZPib3c

Length: 65min 19sec (3919 seconds)

Published: Tue Jun 02 2015

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[u/ZephirAWT]

Earlier this year, Carver Mead of CalTech published a paper which garnered a lot of attention: Gravity with 4-Vector Potentials - A Theory Revolution? The theories with gravitational four-potencial are close to gravitomagnetism, which handles the linear weak approximation of gravity field in similar way, like the electromagnetic field at shorter distances. In relativity theory, gravitomagnetic effects are inertial or gravitational field effects that might be expected when there is relative motion between bodies. Some of these effects are currently included within standard "core" physics, some aren't. In general, at large scales the gravitomagnetism exhibits lack of invariance and it violates the postulates of standard general relativity, namely the equivalence principle and as such it has been ignored for decades. What is bad for general relativity it may be good for experimental physics, because many dark matter effects seem to violate the equivalence principle as well. But it's also the reason, why the Carver Mead's ideas get handled in the same way, like the gravitomagnetism with mainstream physics, i.e. with polite disinterest (1, 2, 3, 4, 5, 6...).

homomorphism of fluid, gravitomagnetism and Maxwell's theory

I do share Carver Meads opinions about nature of photons, role of scientific establishment, etc. Both gravitomagnetism, both G4v theory are well motivated within AWT framework, but they also represent ad-hoced, reductionistic formal half-way approach. Actually I don't think, that G4v theory describes gravitational waves substantially better, than the vanilla general relativity, but many other predictions of G4v theory could be way better. That is to say, the G4v theory has much better ways for its falsification, than the shape of gravitational waves.

(not a final version yet)

"It is my firm belief that the last seven decades of the twentieth century will be characterized in history as the dark ages of theoretical physics. Physics that does not make sense, that defies human intuition, is obscurantist: It balks thought and intellectual progress. It blocks the light of the age." Carver Mead – from his book Collective Electrodynamics

[u/quuxman]

For me this article explained everything in the video in laymen's terms and was a lot more useful:

http://www.npl.washington.edu/AV/altvw180.html

Note that Mead's G4v also applies to electromagnetism, which I find much easier to think about. This approach ignores the concept of E and B fields in some arbitrary (to space time) plane, and treats the force as a 4 (space+time) vector field. Three of these vectors are the magnetic potential in space, and the remaining scalar is "time-like" electric potential.

The exact same concept can be apparently be used to describe all the observed predictions of general relativity without using space-time curvature or dark energy, but I don't understand general relativity so can only repeat explanations I've read.