I thinks it's funny that he goes into such great mathematical depth on some of the most complicated topics in physics yet still takes the time to explain what the chain rule is lol

"Light is the laziest object in the Universe". Ah, so I have a rival then.

Mark my words...this series of videos will one day be archived as a lecture collection for a comprehensive Physics course. Excellent way of explanation.

Next video after only 4 days? Let's go!

Even more weird when you consider light does not experience time, yet it takes the path of least time.

I felt in love with physics at an early age, just learning the concepts. At highschool I had an awesome professor that presented to me all the mathematics to understand and enjoy classical physics. Sadly, I was unable to study it at university level. Finding your channel almost 15 years later helped me a lot to reconnect with the joy of understanding nature. Thanks for all the work you put on this material.

Content from this channel doesnt only answer scientific questions using concise explainations and equations, but it also gives historical perspective as well.

Explaining Snell's Law was great and all, but the highlight was explaining mirages. That was amazing!

as a non-English speaker, i can easily understand what you are saying. very glad to get find your channel

I think we all need to appreciate how you manage to create such high quality content with PowerPoint and a microphone.

Sir, you are a legend and I thank you deeply. I only found this channel recently and studied physics until leaving university at the end of the first year but you have already taught me so much, so many details and key pieces of the logical puzzle that were never made clear to me. For example, I had known that the principle of least time was somehow due to the interference of the various wave functions contributions from the possible paths, and heard that it was a result of the non-optimal paths somehow cancelled out, but I didn't understand the mechanism. I assumed it was too complicated for my level and accepted that I would come back to it later. I now see that the reason is straightforward, simple and elegant. No more difficult to grasp than the rest of the math we had to learn. This is about the 10th time you have done this for me already... pointed out a key piece of the puzzle. Sometimes it can be annoying or feel patronising when you take the time to explain/recall things that like Pythagorean theorem or the chain rule, but when I think about it I realise what you're doing is providing the whole argument from first principles, with every detail necessary to understand, so that no one gets left behind no matter their level. It is humbling and wonderful to get to understand something a little deeper, thank you.

I love these videos... Your clear, simple explanations of each step of the derivation process is inspiring. I see people with all levels of mathematical experience in the comments; the care you put into fostering genuine curiosity in each of them is a work of art to me. thank you

Beautiful description - Feynman would be proud of you!

I appreciate you taking your time to explain more 'simple' concepts, such as trigonometry. It gives everyone a chance to follow your contents, and even if some information ends up getting lost, it also provide a clear path on what to check further. Your videos contain an amazing amount of information and I wish to thank you again for making them.

I’m glad to know you’ve managed to find a way to share your amazing explanations with everyone! It’s not quite the same as your in class lectures, but maybe I won’t have to miss your Physics classes as much!! Thank you.

It's not lazy, it's in a hurry. Excellent video

I understand QED in simple terms! That's amazing! You're the one of the best physics explainers in the field!

As usual, an amazing way to convey different mathematical perspectives about key physical phenomena. It's worth emphasizing the conceptual clarity, the mathematical rigor, and the understandable explanation. Great work!!! Please keep going!!!

This is brilliant, maybe the first time I'm actually understanding the connection between qed, defraction and Snell's laws. Awesome!

So elegant and simple... and the derivation of Snell's law is something anyone with calc 1 under their belt.

This is absolutely magnificent! I love how easy it was to understand the begining, deriving snails theorem, and using functional analysis to find the least time. But the quote by feynman at the end was so stunning. Truely awesome to understand reality

This channel is just so awesome. I really enjoy every video despite the fact that there are sometimes topics that I do not understand. Thanks for the videos and keep up the good work

Great video again! I suppose one thing I would add is that another consequence of the probability amplitudes being like you describe is that if we were able to conduct an experiment where we measured the x position at which the photons cross the air-water boundary to within some degree of accuracy, far from the position of minimum time, the probability would be very small as all of the amplitudes at nearby x positions would sum destructively, while the probability near the minimum would be large as the amplitudes would sum constructively :)

woah, it all made perfect sense. I knew about Snell's law and that in some sense light took the path of least time, but I never quite understood it. And the best part was how easily it was all merged with qed, given that I was also vaguely aware that it also worked in quantum mechanics but in an even more nebulous way (I remember my professor saying something along the lines of light sort of 'looking ahead' in a causality breaking way, but honestly I can't remember much).

OMG You are uploading so fast! Appreciated man!

Just found this channel and now I'm hooked on these videos! As a creator, I felt truly inspired by how you took the time to explain even the simplest things before diving into the advanced stuff.

This is unquestionable the best channel of youtube.. Kids, just skip college and watch this.. I am on the floor in awe..

That's the kind of channel that I don't miss a single video! Always a beautiful dive in nature

much appreciated for going into the mathematical bit for the theory. often, the other yt educators skip the math part. QED, quantum mech, trig, calculus everything in 20 min video and yet comprehensible to people like me who have been away from the field. great work.

This is an excellent video, I thought it had been available for a long time but I see it's just been posted last week. Thank you. Your walkthrough of the minimization problem is inspirational.

Loving all these vids you're making! They're all so good and clear. Thanks

Can't get enough of this great content! Amazing work!

Glad to see another video so quickly. Hello from Toronto 🇨🇦

Another great video, honestly made Schnells law interesting, and it makes me wonder why I didn't learn about this. Keep it up!

One if the best videos I seen in a long time. As someone who hasn't sat in a calulus or physics class in a very long time, I found the math was presented with a perfect amount of explanation.

This channel is such a gem. I'm glad I found it.

it's also a quite nice illustration to lay sine waves over all paths from A to B, because they tend to cancel out (meaning that they have destructive interference at B) for most paths except around the optimum. the most intuitive way to explain Fermat's principle imo

This is a nice condensed adaptation of some of the arguments from QED. It's nice.

I am very excited for the next videos!! Great job

how you managed to compress so much knowledge into one video is mindblowing..QM is a gift that keeps giving :)

Superb video. You pack in so much vital, and fascinating, material - and do it so clearly. It makes me want to go back and re-read Feynman's wonderful little QED.

You are actually forcing me to pass my physics exams with how easy these are to understand! Thank you!

This was one of the best explanations I have ever gotten for this principle. You are a GENIUS!

Out of all the great physics KZfaq channels available yours is the best. Keep up the amazing work!

As always love your videos, I do not understand maths as well as I would like but you are helping so much. I value so much what you do and have just one wish that you keep making video. Excellent work .

Superb content ! As per usual. The 1st time I seen Feynman explain QED, it blew my mind. Still does actually.

Its channels like this that make me reconsider the idea of a flipped class room. Flipped meaning, students watch video at home and when they arrive in the classroom they can ask as many questions as they like. Typically this doesn't work because students can tend to be undisciplined and won't watch the videos at their leisure, but this video series plus many other physics channels do such a great job at explaining stuff that its making me think that such a configuration would work very well in this new era. Anyway, love your stuff, I try and always watch your content the moment it is released (hit the bell). Keep it up!

Light isn't lazy. Its efficient. Excellent content. Respect.

a flavor-full mix of physics, maths, and history that delivers a clear and helpful explanation of some complex concepts. Thank you for your effort. i enjoyed and i learned and i will watch again🙏🏼🙏🏼🙏🏼

It helped indeed! This video gave me a deeper understanding of how things really work. You accidentally explained Feynman path integrals. But there is more. Much much more.

This is a superb video. Certainly one of the best if not the best on principle of least action and its connection to quantum physics

I guess the fastest path principle also explains why light is curved by masses, if time is slower close to a mass.

You’ve helped me become a physics person where not even 6 months ago I self admittedly hated the subject. Thank you so much.

3:56 to 4:48 has a wonderfully visualized explanation involving a Geometric Wavelength.

Amazing work as always!

"Pink Expression" is a perfect album name. Great vid, btw.

Thank you! Remarkable clarity. I really wish I had grown up with access to brilliant work like this. I still remember being the one to stick my hand up to ask "how light knew before it setoff how dense the water would be".. he said "all you need to know is it just does ok" 😂

i think it could be like so: light does take all the routes between A and B, but since the route thats the shortest time "gets there" first, it has a roll of probablility, so a chance to collapse the wavefunction. as more time elapses, more and more rolls are happening. and as only the rolls that are near the fastest route happen, theyre the ones "racking up" the tries, making it more and more likely the actual route will be near shortest time

Wow, this quality content so frequently? Good work man keep it up!

Great topic can't wait to watch

You are answering questions I never asked n I love it. 😂

As is usual for Feynmann, his explanation, which is the one used in this video is the simplest and most intuitive I have seen that explains how this phenomenon is explained using QED. I recommend that anyone interested in learning more about QED read this book. It is a transcript of a series of talks he gave to non-scientists and is designed to present a complex subject in an understandable manner. You will not be an expert in QED who can do complex calculations, but you should have a good basic understanding of what it is all about.

Another great video. One of the best science channels there is!

A great video for understanding these staffs! Thanks. Take love ❤️

I still can't get over how good this guy is. Every video i watch is 10/10 gold dust.

one of the best physics videos I have ever seen on KZfaq 🔥

I was waiting for the day where you would talk about the Feynman QED description in his marvelous book ("All we have to do is simply to trace arrows !"). This book is very dear to me, by far my favorite scientific book. It has been a revelation when I first read it and no other physics book came close since then. But Feynman purposely did not go too much into the details, essentially the mathematics of QED. This is sort of a missing piece for me so I can not wait to see your future detailed video about QED ! Thank you always for this great video, for you work and clarity.

Gosh, what a well thought explanation. I wish that this was around when I was studying this stuff. Cheers.

Loving the quantity of videos recently! :D

Oh boy. This is so well explained - incredible. Very clear.

Simply brilliant (again).

Finally!!! Someone made an explanation vid on Fermat's principle

Amazing content, crystal clear.

This is a very nice derivation of Snell's Law as well as a quick and simple explanation of why Snell's Law works.

Superb Explanation. Anyone can fall in love with physics if explanation is like this.

SIncerly one of the best videos I've ever seen

Very nicely explained.

You keep making me accidently learn stuff from my A-Level physics.

Thank you. This was a very clear explanation.

This was awesome! please continue and dont stop.this was greatly explained .thank you

Excellent video.

Very interesting explanations, incredibly intuitive

brilliant exposition!

Oh yes so excited for this one

Great explanation

Excellent video! Thanks!

Thx. Very enjoyable indeed😊 @ 18.22 curve goes ( continuing its own path ) like going under ground ( below the X-Axis ) than comes up again to the Eye-Level of Observer. Cheers🍻

Class, Class ...Classic expression. Nice ......I enjoyed this video in full. What I understood in half becomes full now. Deliver more videos.

I really like the fact that you explain some of the thought processes of discoverers.

Wow! Another great video...nice job

Thank you so much for this brilliant video

Excellent video! Thank you.

Man I friggin love your videos so much!! Thank you for these!!

@Physics Explained Your videos are a real treasure for youtube. Honestly, you should be given an award for the best physics video content creation in youtube. You breathtaking high quality presentation in your videos and unambiguous in depth and detail formal explanations and physical interpretation given, is leaving really no room for misunderstanding and is an amazing achievement. Be sure your videos are not only educational but are being used also as a review material by scholars and academics. People watching your videos not only appreciate more physics but also mathematics and how these two are entangled together the one pushing forward the other and controlled by logic. Really, best physics scholar literature content in long memory currently on KZfaq or any other public electronic media. You have risen the bar to a much higher new level . Bravo!

Video was made with high quality and good explications ! I really enjoyed this video, thank you so much

Bro! This is fantastic! Please never dumb it down! A little math never hurt anyone!

Excellent explanation! Thanks a lot.

Just found this channel and you earned yourself a sub. Fascinating stuff also glad you don't skip the math even tho I don't understand it it's cool to see for some reason :)

Early for once! Looking forward to the rest of video.

Awesome channel thank you just got done watching all the videos and left wanting more.