Your Daily Equation #19 : At the Core of Fundamental Physics: The Principle of Least Action
ฝัง
- เผยแพร่เมื่อ 31 ก.ค. 2024
- Episode 19 #YourDailyEquation: All fundamental laws of physics share a reliance on a single principle: The Principle of Least Action. In this episode of Your Daily Equation, Brian Greene explains this principle in the simplest example and shows how it yields the basic laws of motion introduced by Isaac Newton.
Even if your math is a bit rusty, join Brian Greene for brief and breezy discussions of pivotal equations and exciting stories of nature and numbers that will allow you to see the universe in a new way.
The World Science Festival (WSF) is an innovative multi-media organization that produces original live and digital content straddling the arenas of science, technology, the arts, media, performance and education. With the goal of radically transforming public perceptions of science, WSF creates world-class programming, both live on stage and televised, featuring inspired collaborations, outstanding talent and novel production techniques that bring scientific discovery, insight and perspective to a broad general audience.
Official Site: www.worldsciencefestival.com
Twitter: / worldscifest
Facebook: / worldsciencefestival
Instagram: / worldscifest
Subscribe: / worldsciencefestival - วิทยาศาสตร์และเทคโนโลยี
This has to be the most impractical yet my favorite way to learn English. From Colombia with love.
you can do a mirror class in Spanish to help me with mine!
*with
@@devekhande9204 Thanks, corrected.
Are u serious buddy? 😂😂😂😂
When Professor Greene explains Physics one can literally see the beauty of nature. Thank you for your time and effort Professor.
Thank you again for your time and effort so far professor Greene by putting this show on the road. I can't wait to see this useful equation applied here. So far this has been a wonderful series with the Heisenberg Principle as my favorite of how beautiful math comes miraculously together to show things otherwise unimaginable.
Thank you so much for doing these equations, Prof. Greene. I know simply entertaining yourself or reading War and Peace would be much easier. One of my goals for this home-sheltering. Is to brush up my calculus, and your discussion of the equations is really helpful in putting the whole thing in perspective! I’m learning lots and having fun!
Please post a lecture on 'Feynman's Path Integral'. Atleast tell us about its intuition, motivation with some mathematical detail.
Entire post GRADUATE math condensed in just one talk with a blend of physics like condensed milk. Telomere growth in mind is ensured if this greatest talk once understood. Thank you very much sir.
I've been waiting for this for so long sir. I watched quite a few videos about the topic but yours was the best!! Thank you so much!!
Hobby-ist mathematician/physicist here, have been watching many Euler Lagrange derivation vids lately, this is one is a gem. Thank you so much for making these. Were very fortunate to be taught math and physics by Dr Greene in the comfort of our own home dressed in nothing more than boxers.
Phenomenal as always professor Brian!! Thank you thank you! You make things look so easy! What a great explanation! Always looking forward for your daily equation episodes! This is the best thing that has happened to all of us who enjoys and loves physics!!
Thank You, Professor Greene, Something just Clicked and now, I Thick I am Getting It !!
Excellent! Thank you for presenting a reasonably deep mathematical justification for the equations.
Dr.Greene your lectures are getting better & better. Keep posting!
Def one of the best channels on TH-cam. Thank you to posting these.
Tremendous! What a beautiful explanation. I have not seen this done so elegantly by anyone before. Please keep up these videos
I loved the comparison between the Newtonian and this method, and how they compare to classic and quantum by means of the trajectories. Great explanation!
Salir
This is my second time to watch this episode. I enjoyed and leant so much. Much appreciate it.
So cool, calm and collected, as always. Thanks a lot for this
Nice job. :) Probably the best one of these episodes yet.
Thank you very much again, Prof. Greene.
This is a beautiful explanation Professor Greene, and I really appreciate these videos. It was really valuable for me for you to walk the path from the simple case, and to be very clear that each path produces a single number. Too often, explanations are too abstract, and don't walk the path from simpler cases to more sophisticated ones and as a result, leave gaps of understanding.
Thanks for this video. I really wanted to get a deep insight into this concept from a theoretical physicist. My undergrad teachers did not really teach it in a proper way only doing only equations in boring way rather than in a fun manner. After all I m a huge fan of yours. With love from India ❤️
Keep posting your presentations, pleeeeaaaase
Excellent summary video Brian! Thank you!!
Thank you professor, enjoy learning from you, always.
Thank you sir,we appreciate so much that we can learn such facts that never learn in college...
thank you very much professor for providing us this kind of high quality material
Haha--'wish this was around when I was in school but nonetheless, wonderfully done. I think it would be amazing for you to do some videos on practical math and physics that can and should be used by everyone in everyday life; to spark the intrigue for all the people that feel or have been told that they are not good at math like discrete, linear, optimization, kinematics, and etc. Even if it's just to help people improve their abilities to critically identify, analyse, and break down problems to solve them.
Your work is greatly appreciated. I've always loved your books.
Thank you.
Love this show, derivations and all!
Loved it (as always), thx!!!
This is a great video. Thank you!
I’m in The Bronx… Thank You so much for such a passionate well structured presentation.
Hi Prof. Greene, I heard you on The Life Scientific with Jim Al Khalili this morning, on BBC Radio 4. It was a very good interview. You didn't say much about your new book though. "Until the End of Time". I am about 20% of the way in and enjoying it immensely. Thanks again. All the best from West Wales (UK).
Hey guys I really like what you do
Im so inspired
Please keep up the good work
Im your biggest fan
You are a gift Dr Green. Subscribed.
This is so interesting! Awesome video, you explained this subject very clearly!
Thank you professor for these videos!
Great explanation...thank you very much.
Would be cool to see something on PDEs like heat equations or fluid mechanics (navier stokes)
You are a true legend. Big fan of yours.
I miss these daily equations, please do more of them!
This is a good video. I got my start with Elegant Universe and String Theory although my focus these days are Loop Quantum Gravity and Supersymetry, M and F Theory. My degree is Liberal Arts but eventually I will get one in Physics. Keep up the good work.
I am learning a lot , many thanks
Feynman thrived on this concept.
Dr. Greene cracks me up sometimes with his subtle jokes . Thanks for the superb content.
Hello sir I am saikat from India...and fan of your teaching style...How you explain complex topic so simply and elegantly.
Thankyou sir once again for all your hard work and for starting this equation series.
Well wishes to You and your family!
I will be waiting for your reply!!
Thanks, Brain!
Good job, Brian
Fantastic!
Excellent Epsiode......
Beautiful deduction of least action in classical mech toward fitting into larger, actual quantum mechanics scenario. Fairly readable presentation with color pens though they got tiny in a couple of spots, but you built it beautifully, rationally how the Euler Lagrangian formula takes us there. Enjoyable. 👋👍
Thank you professor
As soon as I realised that the equation deals with the trajectory at one point in time it made perfect sense what I was looking at - a very roundabout way in classic physics to collapse a wave function. A particle goes from A to B and if you measure it's progress at any point, you measure the trajectory at that single point, and you discard the other data because it isn't relevant to you (and largely unknowable thanks to the uncertainty principle). The wave function collapses because the measurement of a particle in space-time can only take place at a single point in its trajectory.
Thank you so much. 'Classical mechanics is a special case of quantum mechanics.'
Excellent. Please note that at 21:09 the integral for Delta S has an additional dt (one dt before the square brackets and one dt after) as a precursor of using integration by parts. It is corrected in the next minute or so.
FANTASTIC
Good one, once again Sir.
Nice I'm so excited
thank you
Great lecture, very helpfull
I'm not lying: yesterday I was reading On Gravity by A. Zee (a book on GR) which gave only a superficial description of the least action principle, leaving me wanting to know more. Then today this video popped up! The universe is a strange place.
Makes me want to go back to college-enjoyed earnestness. I understand that the Second variation of the Action gives rise to linearised field equations. I would enjoy seeing your take on that -to do so, do we have at the outset to keep second order terms in Taylor expansion ?
Never took a physics class..but I enjoy listening to Prof Greene's talka too much .
Physics is where the Action is!
Good informative video. Thank you
Very good.
Sir, can you please explain why do we exactly need f-throry and extra time dimensions, for understanding of the universe?
Dear Dr. Greene,
Perhaps you could do an episode on the Mass-Superselection Rule or why mass in non-relativistic quantum mechanics does not have an associated hermitian operator?
Will you do a video on the Dirac equation please? And Feynman path integral - oops, never mind I think you will talk about it judging by last comments... anyways, thanks!
Hello professor Greene
An interesting theme is the role of symmetry in
physical laws and especially the various
symmetries in the standard particle model
is very intriguing for me. It
would be nice to hear your insights
about this theme
You have understood the stuff very clearly. I wish if i were your student 😢.
I literally cried of happiness while watching this
*I wonder if you could do a video on Taylor Expansions...............just to give an idea of what it is and how it works..........*
When you approximate by taking the Taylor series up to first order this technique is reminiscent of something I learned in Physics called "perturbation theory". I think that perturbation theory expanded to second order terms. It's been a while 😊
It's incredible how this is the basis of Ted Chiang's short story "Story of your life", which is in turn the basis of the movie "Arrival".
I don't know about Brian Greene, but I definitely wasn't solving differential equations in high school 😂.
Please give examples of the application of the Least Action like with space trajectories, and also the Lagrange Points.of satellites.
Thanks Dr Brian Greene for listening to my earlier request to do episode on principle of least action,my favourite topic.
Could you please describe what app/technology you are using to produce these lectures? I am a high school math teacher who, like many others, needs to provide distance-learning experiences for my students. Thank you.
Hello,
Can you please do an episode on Tensors , General Relativity, and Einstein field equation?
Thank you,
I am Kushaal Kumar Pothula , 14 years old, from India.
Namaskar, yes i want it too
my man study hard you can study it in post grad
U can study that later bro ...I'm an grad student..I don't think they are useful to u now...
Im 14 as well
Awesome handwriting 😁👍
Does the action approach to reach equation of motion works when non-conservative forces like friction are involved ?
9:16 the potential is your forcing function and the kinetic energy is your 'velocity' the path only resolves because the kinetic and potentials are wholly defined - as such the work along that path is of course at a minimum because it is an integral over a closed domain and as such diverting from the defined path will require additional work and therefore leave with a path that is not consistent with the problem definitions. As such the motion or trajectory is defined by the potential and kinetic terms and as such the 'least action' is certainly an obvious outcome. The idea is that it is the inter-dependencies between potential and kinetic energy determine any dynamic trajectory and that is the insightful take away.
Hi Brian what app are you using to write on your iPad.
How about the Riemann zeta hypothesis ?Does it play any part in physics?
I realize this is an older video, but I do have one question. Is there supposed to be two dt’s in the dS equation around time 20:15? If so, why is there a second dt?
I was initially confused, by your use of "v" for velocity, in dealing with it in the context of v(0) when you then introduced "V" as the value of the potential field of a conservative force, in the partial differential (because only x dimension being considered) ∂V/∂x. From out here we can't tell "V" from "v".
Thanks for all you are doing.
Yes, this choice of variable was very confusing.
@@robotickilldozer The variables are standard. But don't worry, when you do this for real, you don't use _x_ and _v,_ you use generalized coordinates _q_ and _q_ dot.
Dr. Green, in your Light Falls video you were talking about how long would it take for us to feel if the sun suddenly disappears and then you discussed about speed of light and speed of gravity. BUT, I don't understand what is speed of gravity? Gravity is a force so how it can have speed?
It is about the speed of information transmission, it is the time that takes for you to Feel the gravitational effect of, in this example, the sun disapearing. Everything in the universe takes a time to get to you even the forces themselves not only light. You can think that it is Light that travels at the "speed of information" as well as the forces, thats the limit speed of things.
(That is what goes kinda weird with quantum mechanics, when two entangled particles far away from each other are measured they "comunicate" at once, faster than the speed limit of the universe (Its not preciselly like that but they violate this speed in a way, search about Locality/non-Locality in QM) )
For Einstien gravity is not a force but the curvature of space, so when the sun disappears, the gravitational wave ( or curvature will flatten) will travel with the speed of light and reach the earth and the time it will take will be close to 8 min to reach the earth. So the earth will continue to revolve the sun till 8 min after its disappearance.
Electrons when they are bound they are not static but involved in stabilising the structure of the atoms of which they are bound too - they are oscillating / resonating within a potential field in fact all matter is subject to a field that determines the outcome in any physical process. It is the probabilistic consideration that really sets the classical and the quantum applications apart - as such the classical application can easily consider multiple paths if uncertainty in the system is translated into the problem definition. But there in lies the game because probabilities are abstractions in themselves - a resolution of an unknown phenomena - my philosophy when it comes to the nature of the universe in that sense all has to do with your awareness - of course if we are lacking data we are confined to formulate problems that are subject to uncertainty leading to consideration of probabilities and errors - however should we possess all the characteristic data of any 'system' that characteristic data completely determines that system by definition. This is the difference between a probabilistic and a deterministic universe - unknowns! With unknowns you will exist in the probabilistic realm however should you be lucky enough to know everything you will live in a deterministic universe - it is the same thing just two different levels of awareness. As such this paradox is simply an issue of self awareness. In conclusion I am happy to draw a line and claim the universe is deterministic when it comes to probabilities you are trying to interpret the unknown in the first instance and as such the existence of unknowns do not disprove the existence of a deterministic universe - however the counter argument would disprove the existence of a probabilistic universe???
Can two different path give the same action?
I didnt get where did you get the expression of substraction of kinetic energy and potential energy
Simple answer: L=KE-V gives the Newtonian equation of motion. Take a look at 24:40 and you will see that KE+V would give the wrong sign for the Newtonian eom.
You can find more sophisticated justifications, but I don't think they would help you.
Learned from the others, I was exercising for past years and years , to be useful, by short & effective action, do not act in rush , every one should get your massage easily that’s why I’m not publish a book,,by the information of the others, the short act , easy to publish, and also you targets quality people, because your assets always with you,classical putting their feet on the hard floor
Thank you, great video. Correct me if I'm wrong, Feynman mentioned in his post-Nobel speech that the concept of principles of least action is a retired cow we can't milk anymore. Nevertheless, I'm curious, is there a book I can read on about expanding this principle for cases with dimensions above the usual 3?
Please explain Avogadro’s Number.
"Variation of function was equal to zero to first order" - what does this mean?
Poisson's Equation!
Please teach me dirac's equation
I wish there was some way to see this stuff on a graph, perhaps this way I might have the first clue about what is happening..........n_.:-) .......supposed to be a question mark on top of my head.
In the neighborhood of the local minima?
Sir I want attend your live class.
How many of you spotted the luminosity drop at the instant it did?
What if you have multiple local minimums?