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Physics with Elliot
Приєднався 16 сер 2021
I’m Dr. Elliot Schneider and I want to help you learn physics! Whether you’re a beginner just starting out with your physics studies, a more advanced student, or a lifelong learner, I hope you’ll find resources here that enable you to deepen your understanding of the laws of nature.
Sign up for my newsletter and get the notes for my videos: courses.physicswithelliot.com/notes-sign-up
If you find the content I’m creating valuable and would like to help make it possible for me to continue sharing more, please consider supporting me if you’re financially able. You can set up a monthly contribution at Patreon.com/PhysicsWithElliot, or make a one-time contribution at PhysicsWithElliot.com/support-me.
Me: Elliot Schneider
PhD, Physics, Harvard University
BS, Physics, California Institute of Technology
elliot@PhysicsWithElliot.com
PhysicsWithElliot.com
Sign up for my newsletter and get the notes for my videos: courses.physicswithelliot.com/notes-sign-up
If you find the content I’m creating valuable and would like to help make it possible for me to continue sharing more, please consider supporting me if you’re financially able. You can set up a monthly contribution at Patreon.com/PhysicsWithElliot, or make a one-time contribution at PhysicsWithElliot.com/support-me.
Me: Elliot Schneider
PhD, Physics, Harvard University
BS, Physics, California Institute of Technology
elliot@PhysicsWithElliot.com
PhysicsWithElliot.com
How Feynman did quantum mechanics (and you should too)
Discover Feynman's path integral formulation of quantum mechanics! 📝 Get the notes for free here: courses.physicswithelliot.com/notes-sign-up
👨🏫 Enroll in my course on Lagrangian mechanics!
bit.ly/lagrangian-fundamentals
✉️ Sign up for my newsletter for additional physics lessons: www.physicswithelliot.com/sign-up
📺 My previous video about the double-slit experiment and wavefunctions:
ua-cam.com/video/Se-CpexiJLQ/v-deo.html
📺 My earlier video about the principle of least action:
ua-cam.com/video/sUk9y23FPHk/v-deo.html
🅿 Become a patron to help make videos like these possible:
www.Patreon.com/PhysicsWithElliot
🙋♀️ "What software did you use to make this video?" and other FAQs:
www.physicswithelliot.com/faq
⚛️ Additional links:
- Feynman's 1964 lecture on quantum mechanics:
www.feynmanlectures.caltech.edu/fml.html#6
- Feynman's PhD dissertation can be found in this book:
www.worldscientific.com/worldscibooks/10.1142/5852#t=aboutBook
- Feynman's original paper on the path integral:
authors.library.caltech.edu/records/9h858-5hv71
- Dirac's 1932 paper that inspired Feynman:
www.worldscientific.com/doi/10.1142/9789812567635_0003
- Feynman's Nobel lecture, including the origin story of the path integral:
www.nobelprize.org/prizes/physics/1965/feynman/lecture/
- Feynman and Hibbs's textbook "Quantum Mechanics and Path Integrals" from the 1960s:
books.google.com/books/about/Quantum_Mechanics_and_Path_Integrals.html?id=JkMuDAAAQBAJ
📖 Video summary:
If you've learned some quantum mechanics before, you've probably seen it described using wavefunctions, and the Schrödinger equation, and so on. That's how quantum mechanics was originally constructed by people like Schrödinger, Born, Heisenberg, and many others in the 1920s.
In the 1940s, though, a 20-something-year-old grad student named Richard Feynman discovered another approach. He found that the motion of a quantum particle can be described by taking a sum over ALL the possible trajectories that the particle could conceivably follow. That sum over all quantum paths is what's nowadays called the Feynman path integral, and it's central to our modern understanding of quantum physics.
One of the most important lessons Feynman's perspective reveals is how the usual laws of classical mechanics emerge from this more fundamental, but seemingly very different, quantum mechanical description of nature. In the video, you'll see why a single, special path emerges from the sea of all possible quantum paths when we consider the motion of a big object like a baseball--called the path of stationary action. And that of course is the path that obeys F = ma!
0:00 Introduction
3:12 Quick overview of the path integral
5:46 Review of the double-slit experiment
8:32 Intuitive idea of Feynman's sum over paths
13:27 Why exp(iS/hbar)?
15:00 How F = ma emerges from quantum mechanics
23:15 Lagrangian mechanics
24:34 Feynman's story
25:22 Next time: how to compute the path integral?
If you find the content I’m creating valuable and would like to help make it possible for me to continue sharing more, please consider supporting me! You can make a recurring contribution at www.Patreon.com/PhysicsWithElliot, or make a one time contribution at www.physicswithelliot.com/support-me. Thank you so much!
About me:
I’m Dr. Elliot Schneider. I love physics, and I want to help others learn (and learn to love) physics, too. Whether you’re a beginner just starting out with your physics studies, a more advanced student, or a lifelong learner, I hope you’ll find resources here that enable you to deepen your understanding of the laws of nature. For more cool physics stuff, visit me at www.physicswithelliot.com.
👨🏫 Enroll in my course on Lagrangian mechanics!
bit.ly/lagrangian-fundamentals
✉️ Sign up for my newsletter for additional physics lessons: www.physicswithelliot.com/sign-up
📺 My previous video about the double-slit experiment and wavefunctions:
ua-cam.com/video/Se-CpexiJLQ/v-deo.html
📺 My earlier video about the principle of least action:
ua-cam.com/video/sUk9y23FPHk/v-deo.html
🅿 Become a patron to help make videos like these possible:
www.Patreon.com/PhysicsWithElliot
🙋♀️ "What software did you use to make this video?" and other FAQs:
www.physicswithelliot.com/faq
⚛️ Additional links:
- Feynman's 1964 lecture on quantum mechanics:
www.feynmanlectures.caltech.edu/fml.html#6
- Feynman's PhD dissertation can be found in this book:
www.worldscientific.com/worldscibooks/10.1142/5852#t=aboutBook
- Feynman's original paper on the path integral:
authors.library.caltech.edu/records/9h858-5hv71
- Dirac's 1932 paper that inspired Feynman:
www.worldscientific.com/doi/10.1142/9789812567635_0003
- Feynman's Nobel lecture, including the origin story of the path integral:
www.nobelprize.org/prizes/physics/1965/feynman/lecture/
- Feynman and Hibbs's textbook "Quantum Mechanics and Path Integrals" from the 1960s:
books.google.com/books/about/Quantum_Mechanics_and_Path_Integrals.html?id=JkMuDAAAQBAJ
📖 Video summary:
If you've learned some quantum mechanics before, you've probably seen it described using wavefunctions, and the Schrödinger equation, and so on. That's how quantum mechanics was originally constructed by people like Schrödinger, Born, Heisenberg, and many others in the 1920s.
In the 1940s, though, a 20-something-year-old grad student named Richard Feynman discovered another approach. He found that the motion of a quantum particle can be described by taking a sum over ALL the possible trajectories that the particle could conceivably follow. That sum over all quantum paths is what's nowadays called the Feynman path integral, and it's central to our modern understanding of quantum physics.
One of the most important lessons Feynman's perspective reveals is how the usual laws of classical mechanics emerge from this more fundamental, but seemingly very different, quantum mechanical description of nature. In the video, you'll see why a single, special path emerges from the sea of all possible quantum paths when we consider the motion of a big object like a baseball--called the path of stationary action. And that of course is the path that obeys F = ma!
0:00 Introduction
3:12 Quick overview of the path integral
5:46 Review of the double-slit experiment
8:32 Intuitive idea of Feynman's sum over paths
13:27 Why exp(iS/hbar)?
15:00 How F = ma emerges from quantum mechanics
23:15 Lagrangian mechanics
24:34 Feynman's story
25:22 Next time: how to compute the path integral?
If you find the content I’m creating valuable and would like to help make it possible for me to continue sharing more, please consider supporting me! You can make a recurring contribution at www.Patreon.com/PhysicsWithElliot, or make a one time contribution at www.physicswithelliot.com/support-me. Thank you so much!
About me:
I’m Dr. Elliot Schneider. I love physics, and I want to help others learn (and learn to love) physics, too. Whether you’re a beginner just starting out with your physics studies, a more advanced student, or a lifelong learner, I hope you’ll find resources here that enable you to deepen your understanding of the laws of nature. For more cool physics stuff, visit me at www.physicswithelliot.com.
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Відео
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great channel, great content, great presentation and explanations and graphs.... A++
The prime requirement of physics is that you should extremely good at mathematics.....even very basic level physics may need you to use extreme mathematics 😂😂😂........and higher physics is out of the scope of the present available mathematics 😂😂😂
I think there was one similar question in the past Physics Bowl exams
The "parabola" examples, are, ofc, wrong.
31 minutes of absolute brilliance
I think that Newton had the idea that gravity bends light through a simple thought experiment: Bob, standing next to a wall of a free falling elevator shoots particles of lights towards the opposite wall. While Bob determines that the particles moved in a straight line, Alice on the ground, does not see the same. Instead, she sees the particles moving on a curved trajectory! Therefore, they conclude that light moves on straight lines on frames free from the action of forces, but not when moving in a gravitational field. Therefore, gravity should bend light! Furthermore,they conclude that the greater the gravity, the more curved will be the trajectory.
What app do you use to write?
Rings with all nonzero elemnts invertable go brrrrrrrr
Replace Laplace transform with Fourier transform and your video might actually be good
But isn't the real challenge in finding the potential energy in a specific problem?
Just do static analysis and oversizing comes with experience dont need differential equations
0-0
i love you
beautiful! thank you for making this
I wish my professors were this good at explaining
Why should we take 2nd derivative??
great remedy of insomnia
Can you explain why the standard Lagrangian is T-U? Intuitively, why that specific form (other than 'because it works')? Thanks
Thats just fcking great!
One of the best explanations on this topic
Thanks a lot, sir!
"There's a good chance you've run into this equation before." My man, its 11PM and I'm eating a donut on my kitchen counter. Not only have I not run into that equation before, but in an hour it is going to be replaced with more math I can't do, a video about a cool rock, or documentary about a country I ain't ever gonna go to. Simple Harmonic Oscillators look like they kick all kinds of ass but I am up too late looking for answers to problems that differential equations can't solve. Do not underestimate how dumb I am.
Here before this channel gets millions and millions of subscribers. Keep doing these animations, they are invaluable when you show the concepts. It really helps visualising the physics and the math.
My teacher said I dont need to study lagrangian until I can get into APhO😂
E=mc^2 Schwarzschild radius
It seems I can win Nobel prize if I take your course.
I have just found this channel, weeks before QM exams. Your videos really helps to patch the fragments. Thank you the video!
Anyone else still have no clue?
Probability of finding an orgasm in Ex
Great1
im starting quantum theory 1 now and the next video could really help!
Wolframalpha
The only problem is that the hamiltonian is not always equal to the total energy.
What are you talking about?
Why do we use dot notation to regard n-th order differentials instead of the standard apostrophe "prime" such as f'(x)?
Man this is high quality, easy some of the best physics educational content on youtube. Do you still plan on uploading any problem sets for this video? Thanks a lot for the notes btw
You got to be some kind of big idiot to be surprised still how nature works!
This just made my head hurt
Im fking enlightened
Thank you so much sir for this video ❤✨
Why normalised wf is required??
It isn't, really. The normalization is merely an expression that we are dealing with an ensemble (i.e. an infinite repetition of the same experiment). It works well for closed systems with finite volume and it doesn't work, at all, for scattering problems. It's kind of the toy version of the real theory.
ah, yes, one of the most known engineering theorems: sin T = T
Amazing, thank you so much. It was music to the ears listening to you!
MashaAllah
So... You don't need calculus unless you want to find a particle. Ok, wasted a year in school 😂😂😂
Great video thanks, very clear and engaging
Lagrangian is sick
I'm gonna do u the good of telling u why I can't hang: u called Newton's interpretation of his share of facts "nonsense", as if u with the same facts could've done better. Look up the words "intellectual" and "hubris", then have a think.
Hate to be a hater, but I find the explanation in this video to be lacking and circular. Okay, so we're going to pull out this factor (1/ih_bar) and this here is a quantum generator(because it just is), and now that we've pulled out of our hat that it's the quantum generator, it should be momentum. For me, Dirac's approach of getting the quantum Poisson bracket from the classical one is much more satisfying and then using the canonical commutation relations you got from that you find the translation operator and all the other stuff you want.
On a xyz graph, a point is potential energy. Time is kinetic energy when going to another point. This existence is amplitude and is nested between another reality made up of shattered pieces.