New video coming out soon! Kindly requesting feedback
Added 2024-10-26 23:01:17 +0000 UTCComing soon: our video on one of the most fundamental principles in all of physics - The Principle of Least Action.
This is a work-in-progress version. We'd love to hear your feedback and suggestions as we finalize this video.
Thank you so much!
Casper and Team Veritasium
Comments
Derek, please contact me. I know how to measure speed of light in one direction.
Иван
2024-12-14 22:44:23 +0000 UTCNo problemo! Keep up the great work
Shiroyasha
2024-10-30 19:03:27 +0000 UTCSo sorry, Shiroyasha! I'll make sure your name appears in the next video.
Veritasium
2024-10-30 17:44:17 +0000 UTCWe've added the parentheses, thank you for the suggestion! - Casper
Veritasium
2024-10-30 17:38:52 +0000 UTCWe made this change, thank you so much Bahman! - Casper
Veritasium
2024-10-30 17:38:16 +0000 UTCThank you! We fixed this - Casper
Veritasium
2024-10-30 17:36:19 +0000 UTCLooks promising and will be easier to follow with animations - It is really great to see a historical approach, in that most people (I believe) simply learn the formulas/techniques to be able to apply them. My experience (mostly in statistics) is learning some of the history really helps understand the math/methods. I look forward to seeing the animations added in. I'm not sure you're going to do this, but it would be really helpful if you could add some cites in a linkable document that people with different familiarities with the math could follow up on (e.g. Paul Nahin). Finally, when I learned some of this in a math of optimization class (taught by Euler- just kidding), we learned it as calculus of variations, which to me is a commonly used term but not mentioned here (at least I think not).
Dan Sherman
2024-10-30 01:30:02 +0000 UTCLooks like my name didn't get tagged in the end 🤔
Shiroyasha
2024-10-29 12:24:54 +0000 UTCGreat video as always! 1. I don't think it is clear what Bernoulli's solution was. It seems like you mention his creative solution, and then jump ahead to future discoveries and innovations. I feel like that thread was lost somehow. 2. I think idea of setting the derivative to 0 vs a true minimum should be fleshed out with some intuitive examples like a hill. It is an important and big idea to just throw out some terms and then end the video without explanation. 3. I think you should at least mention that you are using the tools of calculus with some brief explanation of what they are for those not familiar. Thanks!
Benyomin Walters
2024-10-28 19:57:10 +0000 UTCAt 14:00, the character's costume changes were very distracting, and the clock's hands seemed to be going in opposite directions. I was also disappointed at the end that tying least action to modern physics would wait for the next video, because the intro implied it would be covered here. I think the intro should state that this is the first video in a series, and this one covers the classical groundwork of least action.
Chris Mullin
2024-10-28 14:35:31 +0000 UTCAt 25:39 you label the entire set of two terms in brackets as F(t) and then a few seconds later you identify the second term as the force F(y). That’s not an ideal choice of variable names :-)
TTST
2024-10-28 00:42:44 +0000 UTCAnother awesome video of physics history! I used Euler-Lagrange equations in my PhD, where I had to model a multy-body system. It's infinitely easier to work with energy and scalar quantities than forces and vector quantities. Moreover, in a multi-body system, the kinetic and potential energy can be computed for each moving body independently and then added together to form the energy of the complete system. This is a dense topic (physically and mathematically) for a more restricted audience, but I think you did a great job in making it playful and didactic. Congrats!
Fabio Bobrow
2024-10-27 19:40:21 +0000 UTCFascinating topic but for those of us whose calculus is in the rear view mirror, that is a lot of math to follow visually as it speeds to its path of least action. If you want to reach and retain your largest audience, I would eliminate a lot of the onscreen math and have it available on the website as maybe an in-depth video.
Miriam Block
2024-10-27 16:06:48 +0000 UTCDuring the discussion of Fermat, there's an opportunity to segue into the history of the speed of light. If Fermat solved Snell's Law in 1657, then why are the first estimates of the speed of light attributed to Romer in 1676? You've called out that Snell's law identifies the _ratio_ between speeds of light in the different materials, but you could draw attention to the fact that if you don't have an estimate for any of them, then you can't directly calculate the others. But another interesting conclusion: this implies that the speed of light must be finite - this was already consensus at the time, but this interpretation of Snell's law is another effect that requires it.
John Zila
2024-10-27 14:13:05 +0000 UTCI really enjoyed this - I cannot wait until it is as complete as possible. Your actions.
Donald J Arndt
2024-10-27 13:58:53 +0000 UTCA great, fun video, beginning to end. I especially love the end. Thank you for this one.
Dave Muth
2024-10-27 13:47:50 +0000 UTCSo thankful there are people who understand this stuff cuz I sure don’t. I wish I did but my brain is just not wired for it. About every minute in this video I’m thinking: “Wait. What?” Especially when shifting through the equations. I’m simultaneously lost and fascinated. Its humbling.
H C Adams
2024-10-27 12:37:42 +0000 UTCGreat storytelling as always
Shiroyasha
2024-10-27 10:01:54 +0000 UTCLike it. (Again) this video has it all: History (fastest descent experiments, competition between scientists) simple physics that 'everyone' recognizes (Snell's law), and you don't 'dumb it down' by avoiding formulas (the reason I canceled my subscription to Scientific American), and then questions like: "Is there an intuitive way to think about action?" BTW at 17:33 and 19:32: "Animation placeholder" ;-)
Jan Doggen
2024-10-27 09:00:59 +0000 UTCIn the begining of the video I thought that this apply only on earth... Do you think there is some easy explanation of kinetic and potential energy in the space or water? Anyway good work as all of your content is great.
Norton Slovak - ElonClub
2024-10-27 07:58:35 +0000 UTCThis is another great topic... thank you Suggestions: The following is an example which I am most familiar… which I think most people can relate… unless wanted to use a different example. The following is via Google search: (Note: I have seen it also used for explaining Richard Feynman’s “sum-over-paths (or sum-over-histories) approach” Light's path is similar to a lifeguard's path: The path of a lifeguard to save a swimmer is similar to the path of light traveling from air into water. The French mathematician Pierre de Fermat discovered that light takes the path of least time in 1657. The least path for a lifeguard to save a drowning swimmer is to run to the water's edge at the point closest to the swimmer and dive in. This is because running is faster than swimming, so the lifeguard should spend as little time swimming as possible. In addition, here are some of my observations: 00:00:32:00 The phrase “It may, in fact, explain the behavior of life itself” was stated, however, this was not described in more detail later in the video (unless it is going to be in part 2?) 00:08:15:00 it is a little distracting to have the ball repeatedly move (animation), from A to B, while trying to look/concentrate at the equations that are being given. 00:11:06:00 maybe add to the writing… the summation at the beginning of each of the three lines which show the following: ∑MVS(↑) for further distance ∑MV(↑)S for faster velocity ∑M(↑)VS for more massive 00:11:39:00 maybe add to your statement “… to see the principle in action” the following “… to see the principle of action in ‘action’ ” 00:20:04:00 it is not clear, to me, how you went from (2T dt) to (T + T dt) 00:24:51:00 I like the use of equations, however, just as Patreon member @AW, mentioned, this was too in-depth, too fast, and too hard to follow. And, I am also not sure how to best to go from Maupertuis formulation to Newton’s equation
Greg Scopel
2024-10-27 07:17:23 +0000 UTCReally liking the timeline showing this research through history. @20:05 Suggest parentheses to group order of operations. Aligning everything to the equals sign is appreciated, and now I want more clarity what is substituting for what and when, what is inside the integral and what is outside, and what values are multiplied by ds and dt. @20:09 Clarify notation: Are these variables from another language? You use "T" as "kinetic" (not "total"), "V" as "potential" (which has no letter "v"), and "E" as "total". @21:03 "This looks like lot like some other minimization principal" Such as? This is first equation of this sort depicted in this video. @24:38 Define new notation: "S". This was not introduced previously. @25:18 What happened to "m*(dy/dt)*eta" from the 2nd line to the 3rd line? It disappeared. Does it evaluate to 0?
chromicacid
2024-10-27 03:35:06 +0000 UTCActually, Adam Savage did the tachystochrone a few years ago, but the beautiful part is variational calculus. Most of us did not work with variational calculus in college, but I was fortunate enough to have a math teacher who at least told us "hey, this is the way to calculate things: everything always follows the path of minimum work" and I have hence declared to the four winds that the universe is esentially as lazy as I am. Not lazy enough to not tell you this: edit the bit when the expert says "Maupertuis, I've done a lot of physics and math and you may be the first person I hear pronounce it" (at 13.20). It looked as if he was praising your acumen on this, and it is a gratuitious but useless tour de force to just say he is not mentioned. We your viewers are mostly college graduates, and we've never heard of Maupertuis before, that's for sure. Now, I've reached 24:56 and honestly, the integrals are visually cluttered and meaningless. I can't imagine a better way myself, but I'd try and research deeper into variational calculus with experts; there must be a less painful way to graph this. And finally, you had to mention the UV catastrophe. I'd rather not. Go with "explaining why the sun shines as it does" or something more mundane but appealing. You're going ballistic on the viewer, specially knowing that the continuation is esentially the explanation of why we have quantum mechanics, something that you assume everybody knows, so, Ouroboros, you're eating your tail there.
A W
2024-10-27 01:22:01 +0000 UTCPerhaps walk through an orbital mechanics problem explaining the concept of slingshot boosting of vehicles around planets using this concept? That idea makes no sense on its surface because you should use up any energy you gain dropping into the gravity well when the vehicle climbs back out, until you consider using the thrusters at different speeds results in differences in total kinetic energy. On a related but more basic note, I don't know if you have any videos using physics examples to explain derivatives or integrals conceptually to lay people, e.g. 8th graders, but I think you could do it technically very well and provide some great historical context. I also read a great biography of Fourier at one point and realized you can describe what he is doing using trigonometry or calculus, which was very refreshing and might deserve it's own explanation video. The relationship between calculus and trig.
Karl W
2024-10-27 01:09:02 +0000 UTCYou omitted the negative sign in 1/2 v^2 = –gy. So v^2 = 2gy is not quite correct. Best write v^2 ∝ 2gy instead.
Bahman Engheta, PhD
2024-10-27 01:02:01 +0000 UTCThis is great. Well explained, I never knew the history of the principle of least action with all the European people history (Voltaire, Maupertuis etc) and I am French. The derivation of the math (step 2) could probably be a bit clearer. Using the same variables v and V, s and S while consistent with usual terminology can be confusing Similarly, missing parenthesis (T-V) dt, although likely voluntary to keep it simple may confuse some younger math-inclined viewers in HS and early undergrad that have not been introduced to the derivation of the Lagrangian already.
Jean-Manuel Izaret
2024-10-27 00:38:39 +0000 UTCI can't help but think that Veritasium is trying to apply the Principle of Least Action by crowd sourcing advice on this video :) Just kidding, the preliminary cut tells a good story and has a nice pace. I particularity like the historical references and quotes. Perhaps you could more closely describe the relationship between the Least Action constraint and conservation of energy or the concept of entropy.
Dubman
2024-10-27 00:34:18 +0000 UTCDerek, the video was an absolute banger. As a physics nerd it's one of your best IMO. At 20:46, there is a slightly funny edit (cutoff?) of your voice.
Jonathan Fuzaro Alencar
2024-10-27 00:06:30 +0000 UTCThis definitely needs more parts!
Adam Foreman
2024-10-26 23:54:39 +0000 UTCAm I the only sod in the room (AGAIN?) thinking this problem is perfect for a fully developed, and operational #QuantumComputer? #JustSayin 🤔
Hacim Llih
2024-10-26 23:46:21 +0000 UTCWait, what about the rest of the Thermite series?
darkwater4213
2024-10-26 23:12:33 +0000 UTC
