I never understood why light has ENERGY but NO MASS... until now!

[@Mahesh_Shenoy]

To try everything Brilliant has to offer-free-for a full 30 days, visit brilliant.org/FloatHeadPhysics/ . The first 200 of you will get 20% off Brilliant’s annual premium subscription You will also support my channel. Thanks in advance!

[@charlesbrightman4237]

E divided by c2. Okay, BUT 'speed' is distance divided by time, distance being 2 points in space with space between those 2 points. And modern science also claims that space can warp and expand and time can warp and vary. So, how could the speed of light be constant if space and time are warping, expanding and varying? Unless the rate of change of space and time were equal in nature, then the speed of light should also vary depending upon what space and time it were in. Also, the singular big bang is a fairy tale for various reasons, the CMBR from the supposed big bang should be long gone by now and should not even be able to be seen by us, and the red shift observations have a more normal already known physics explanation, no dark energy nor dark matter needed. 'Space' is not expanding like modern science claims it is.

[@charlesbrightman4237]

'Speed of causality': 'Speed' is distance divided by time, distance being 2 points in space with space between those 2 points. What exactly is 'space'? What exactly is 'time'?

[@GodSahil]

Finally a sponsor!! Party 🎉

[@rabindranayak4049]

Sir next video on 'What is Energy?' Words like mass, space, energy, time, spacetime, consciousness and reality are too puzzling. So please few videos on these puzzles.

[@charlesbrightman4237]

@@rabindranayak4049 If I may, in the interest of furthering the answers to your request, offer my current views of 'space', 'time', and 'spacetime'. As far as 'reality' goes, my gravity test for my theory of everything idea has to be done, but 'if' true, and I fully acknowledge the 'if' at this time, but 'if' true, then the 'gem' photon would be the energy unit of this universe that makes up everything else in existence, including you, me, our consciousness, memories and thoughts. Please look for more posts to you after this post. 1. Concerning 'space'. 2. Concerning 'space' and 'time'. 3. Some questions that 'if' my theory of everything is really true, could potentially answer in a coherent interrelated way. * I by no way am claiming my views are correct, but for me, they are placeholders until something more correct comes along, if ever.

[@spate7207]

Even as a high school physics student myself, your explanations are never inaccessible and don't assume a heavy background of your viewers, that's quite tricky I'd imagine and admirable! Keep up the great work, you've earned a new subscriber!

[@Mahesh_Shenoy]

Brings me great joy to hear this. Because that’s exactly what I aim for in this channel. Thanks for sharing it :)

[@georgehunter550]

Real

[@EdoAgos-zg4nq]

I have to thank you one more time for your exciting explanations. You are pushing me to study physics at university!

[@flachdenker-O]

I miss the explanation of Emotion. What is with Esquared?

[@effectingcause5484]

Mahesh I am just waiting for you to make the next break through realization that changes the world. I know you’re going to figure something out. I believe in you!

[@rafaelfcf]

I'm a Brazilian learning physics invented by an old German guy in English from a guy I presume (I'm sorry if I'm mistaken) is Indian. The internet can be such an amazing place for humanity. Thanks for sharing and making it easier to grasp.

[@عثمان-م5ع]

and the Iraqi me is reading this comment

[@nullpointerworks4036]

@@عثمان-م5ع And a Dutch guy, me, responding to the Iraqi

[@yaseenmomin3376]

Good from Morocco

[@satheesht]

Internet has become an amazing place for humanity no doubt. Wonderful to have lived in the era of Sal Khan, Andrew Ng and happy to listen to Grant Sanderson, Mahesh and many other brilliant KZbinrs out here.

[@LoveRai-yx6vs]

And indian guy confirming he’s indian😊

[@klosnj11]

You know it is a good explaination when you get to minute 6, haven't learned anything you didnt already know, but still have that eureka moment where the puzzel pieces fall together and you intuit the answer before it is given. Well freaking done, good sir!!

[@Mahesh_Shenoy]

Wow. Glad to hear that :)

[@Poly-Goon]

I agree

[@drsamliveriadis7462]

At 64 I fell in love with Physics Relativity and Cosmology. Your simplified explanations really makes it easy to grasp some very complex and yet fundamentally simple ideas that the Titans of Physics spend a lifetime to discover and formulate. Thank you

[@ineffige]

It's beautiful isn't it? I remember when I first read and understood concept of higher dimensions and it felt like my mind went to a gym and ate LSD. Then Bells theorem. Same thing. I love it!

[@SumitMahtok1z]

How did you fall in love with Physics and Cosmology?

[@ineffige]

@@SumitMahtok1z i realized I find pleasure learning about concepts that bend my mind (I still remember when as a kid I understood concept of dimensions from maths perspective )and require abstract thinking. I find similar pleasure learning about philosophy. I think it's personal proclivity

[@mbchrono3]

I love how you have conversations with Einstein to explain these complex topics! It puts things into a certain perspective unlike that of other educators on KZbin. Great video!

[@Mahesh_Shenoy]

Great to heart that. It also comes pretty natural to me. Used to do this a lot while teaching in classrooms :)

[@davidej9091]

Please explain why they have momentum. Still a bit counterintuitive to me if they’re massless

[@mishtigoel9201]

​@davidej9091 I think its because light has wave nature so that allows it to carry momentum without having any mass

[@dreamdiction]

He externalizes his internal monologue so we know what he's thinking.

[@taylorj6177]

This guy is something else. Truly special intelligence

[@barmalini]

What a great lecture Mahesh, now I know I'm not overweight, I've just become fuller of energy.

[@DerekFullerWhoIsGovt]

😁

[@TeChNoWC7]

Or the gravity of the earth has just increased 😂

[@itzmaailaaaife]

😂mmmm...

[@joydeepsingh9113]

Hahahaha. Awesome. But excess of everything is bad bro. That applies to too much energy top the excess energy you've got can give rise to bad mass inside your body like cholestrol and triglycerides and that extra energy accumulated inside your arteries in the form of cholesterol can cause heart attack. So lose the extra energy

[@naveenkumarjha5428]

Yes, you will have to burn your inside energy by doing physical.

[@Luis_1605]

Greetings, I am a 16-year-old residing in Germany. Recently, during my astronomy class, we delved into discussions regarding Newtonian principles and the nature of light. Intrigued by the concept of photons lacking mass, I sought clarification from my teacher, only to receive the response that the explanation would delve too deeply into the realm of quantum physics, beyond my current grasp. Undeterred, I turned to KZbin and found the topic elucidated in a manner that was remarkably comprehensible, even for someone of my age. Kudos to the creators for their adept explanation.

[@sevenstarsofthedipper1047]

They are not even studying astronomy in high school in a lot of American schools

[@Luis_1605]

​@@sevenstarsofthedipper1047 While astronomy may not be universally emphasized in American high schools, the German education system tends to prioritize a comprehensive scientific curriculum, providing students with a more robust foundation in subjects such as astronomy.

[@sevenstarsofthedipper1047]

@@Luis_1605 A lot of American schools are anti-science. The Christian Right is systematically dumbing down our population.

[@eyewaves...]

Ich bin Deutscher und habe an der TUM Physik studiert. Unser Schwerpunkt in der Astronomieeinheit lag auf der Atomspektroskopie - was eigentlich eine echte Ausbildung in Astronomie ist. Ich bin ein bisschen neugierig, an welcher Universität Sie studiert haben...

[@Luis_1605]

@@eyewaves... Wie Sie bereits erkannt haben, befinde ich mich derzeit im Alter von 16 Jahren. Ich habe noch kein Studium begonnen und besuche derzeit ein Gymnasium, das mir eine vertiefte Ausbildung in Astronomie bietet. Nach meinem Abitur beabsichtige ich jedoch, ein Studium der Physik zu absolvieren.

[@danieltdp]

I haven't seen this kind of content for 25 years, since I left physics. Really cool to be taken back by this very clear explanation!

[@sqlexp]

He was disappointing. Does he also have a definition of momentum designed for dumb people? Or, is he saying photons have zero momentum? I can't imagine how his hamster is going to spin around for the conservation of momentum involving photons.

[@OrichalcumHammer]

@@sqlexp check his other video for momentum of photon.

[@sqlexp]

@@OrichalcumHammer I already did. That's all just cope, made-up calculation to compensate for the shift to masslessness. He never explains how massless objects produce gravity. Does he have a video with a formula for the gravitational force of massless objects, or a video that argue that photons neither produce nor is affected by gravity? If it behaves in every way like mass, it is mass.

[@TK-zl8fu]

​@@sqlexp Doing the opposite of what a truly intelligent person would do. What is disappointing, at the moment, in the very least, is your behavior.

[@k.vinay.]

For 18 years, I have been trying to understand this. Now, I have gained some real insights into the nature. Thank you; your efforts are greatly appreciated.

[@AG-ig8uf]

Such a long video about nothing. The actual formula for Energy Mass EQUIVALENCE is E2=m2c4+p2c2 where m is rest mass. For photon rest mass is 0, so first factor on the left is also 0. For resting object with mass second factor on the left is zero, so you get famous E=mc2. There is absolutely no such thing as "Has energy but not mass" as the titles states, it is literally called EQUIVALENCE principle. This guy is really confused.

[@bollywongaloid]

@@AG-ig8ufyes we can all do basic math but this video does a good job of explaining why that mass is zero by definition

[@remcovandijk279]

​@@AG-ig8ufif you look at the formula that you wrote down then for a particle travelling at c the rest mass is zero but that doesn't mean it has mass, that's not what 'mass equivalence' means. The second term on the right does not contain mass, it contains momentum and that's not the same. A photon has no mass, it has momentum. P is not equal to mv for photons, it's just p.

[@MaddyIndia]

Similar boat here. Awesome video this.

[@amaze2708]

The algorithm sent me here. All I want to say is what a phenomenal educator/presenter you are. That was truly something special. Now excuse me while I go check out the rest of your videos.

[@thomasendicott4207]

Mahesh, I’ve only seen a few of your videos, and I rarely comment on any video I watch, and I have to say… the energy and enthusiasm you bring to the topics you lecture on are unrivalled. You remind me of my program head during my stint in robotics back in the day. There is an obvious excitement and deep respect for the universe, how it works, the fundamental strangeness and the absolute WONDER to be felt given the slightest understanding of these phenomena. If there is a future I could wish for, it is that all else false aside to truly grasping how incredible this reality we exist in is at a near-fundamental level, and you are making large steps to that reality. I am so excited to see this channel grow, and I truly wish you the best. Cheers.

[@Mahesh_Shenoy]

Wow, that means a lot, Thomas. Thank you for taking the time to share this :)

[@lucialaw4326]

I watch a lot of educational content on youtube, especially math and physics stuff. I haven't encountered someone as exited and engaging as you. The way you ask questions and go about investigating them works so well for my understanding of the topic. Keep up the great work!

[@amolbhatki5278]

I like to think of it this way - E=mc^2 is a simplification of E^2 = (pc)^2 + (mc^2)^2. When things aren’t moving, the momentum half of the equation goes away. When things don’t have mass, the mass part goes to 0. Your explanation made this equation much more intuitive. Thanks for the clarity and insight!!

[@sabiancoomber-nickerson5830]

I came across the full version of e=mc^2 when I was wondering how photons can have momentum despite having no mass.

[@hoonigan1423]

​@@sabiancoomber-nickerson5830 cause photons have wavelength and according to de broglie eqn p=h/lamda where h is plancks constant nd p is momentum lambda is wavelength

[@hoonigan1423]

​@@sabiancoomber-nickerson5830nd lamda is wavelength

[@Factsbite90]

Same dude i also thought the same thing

[@shancg1]

do u think this is a better explanation?

[@quoenix9340]

You really are the dream explainer/teacher I've always wished for. It's just way too intuitive and interesting to watch your explanations. I've watched your videos on Khan Academy before, to study for 12th exams, and honestly I so wished I'd find you somewhere else just for random science stuff other than studies. I'm so excited to find you here on KZbin now, and I can't stop binge watching all of your videos and shorts. Please never stop making these, and thank you!

[@Mahesh_Shenoy]

Thanks thanks :)

[@grahamnewton4381]

A very useful explanation which clarifies much of what I have not been clear on in the past. One question. Does that mean that a ‘solid’ object eg tennis ball travelling at the speed of light, would have no mass? If that is wrong it still seems to indicate that the actual structure, not just the movement of an object is an indication of mass. Sorry if this is a naive question.

[@anukpersad4808]

Interesting style or method to adapt really like the style of teaching very attractive

[@SpikeDonkin]

@@grahamnewton4381 Very good question. He seems to infer it would have no "extra" mass. I'd like to know the answer as well.

[@CyThirtyFive]

You're the only youtuber that's been able to explain this better than my astronomy teacher... who could respond to my in person questions.

[@Qsderto]

Not all teachers are good teachers.

[@tommurphy1153]

Mahesh, I'm a Mathematics graduate and one of the best things is finding a new way to look at stuff and sometimes that springs whole new inspirations! I love your videos (and your conversations with Einstein) and they bring me many new ways to look at things. Thank you!!

[@transformations1]

This is one of the best explanations for E=MC² come across in 15yrs, simply mindblowing. Your explanation made E=MC² equation much more intuitive and likewise concept of Mass. You could expand further on the "speed of causality" part, that deserves an entire video and somewhat rushed at the end. Without getting too complicated, you could also introduce the idea of Markov blankets and the "inside" and "outside" distinction for the reference frames. I think this is very important today, since many people introduce mysticism and all sorts of nonesense about "everything being energy and One" - which is kind of true in a superficial truism, but ignores the inside/outside Markov blankets - which applies to literally everything from atoms, galaxies, minds and people. (in some respects a refutation of idealism in metaphysics) Excellent work Mahesh !🙂

[@karlmiller5009]

You make a great point about Markov blankets. I’d also love to see him use them for explaining causality. Thanks for suggesting it. However, whether something is inside or outside a Markov blanket wouldn’t refute idealism. A Markov blanket describes how systems exchange information with their environments, not whether those environments are fundamentally mental or physical. Idealism isn’t necessarily concerned with this boundary in the same operational sense, but with the ontological nature of reality - whether it is mind-dependent or not. At best, they could be used in discussions about how the mind interfaces with what it perceives as external reality, which could even be aligned with idealist arguments, but they don’t provide a definitive answer to the metaphysical debate.

[@LoganPEade]

Excellent explanation! For almost 40 years I've been studying thinking and waiting for that one final very small epiphany that causes the light (no pun intended) to switch on and suddenly I get it, E=MC² is in my grasp. This is the closest I've gotten, you actually filled in two parts out of three I needed, alas there's still that one last one! Thank you, I'll keep watching your videos, something in way you break it down will finally work for me! 😁👍

[@khush1894]

how would you describe your third unfilled part to be like? what do you feel is lacking that will finally get you enlightened

[@chaseosburn3012]

@khush1894 Yes! Im curious too

[@gabew3506]

​@@khush1894 I feel the same as the above comment, but my lack of understanding is with why mass has inertia in the first place and why einsteins postulate is true. Obviously everything (large scale) about our universe works out because the speed of light is the same in all reference frames but i dont understand why this is the basis on which all of relativity sits. It seems circumstantial

[@aresjupiter847]

it's amazing how an equation/formula of 3 letters is so complex in details, that someone needs almost 22 minutes to explain it. and it's also amazing how I, someone who just finished HS, someone who just loves physics, came here and watched it all, and actually understood. your explanation is truly captivating and understanding, even for some who doesn't have a degree on physics or something like that. thanks for being and talking so accessible to anyone who just wants to learn something more/new.

[@zosiunias4130]

5:51 - "This is it, this is the climax" - *Ad pops up*

[@kratossmash4209]

Lmaoo literally

[@Doom.00]

Bro, same with me now!!!😂😂 I was like- wt...😬

[@Abdulfarith-ff3rs]

😂

[@fidel_soto]

Yea I felt like commenting that KZbin is diabolical for that.

[@wyrmofvt]

The first use of 'c' as the speed of light predates Einstein use as the speed of causality. Indeed, he only changed the symbol for that to 'c' in 1907 - previously, it was 'V'. 'c" started to be used for the speed of electromagnetic interactions by Lorentz and Plank, Plank using the symbol as early as the 1890s. Also, 'c' was in wide use prior as the speed of sound, where it came from "celeritas" - Euler used 'c' as the speed of wave propagation in a drum as early as 1759.

[@kylelochlann5053]

There is no such thing as a speed of causality.

[@tonyrivera5769]

@@kylelochlann5053 I started scratching my head the moment I heard "speed of causality".

[@kylelochlann5053]

@@tonyrivera5769 You can use "c" to be an upper bound on causal influence, but causal influence, like throwing a rock through a window and talking to someone, also travels along time-like curves, basically everything inside the forward light-cone and including the light-cone.

[@mmotsenbocker]

hmmmmm causality must have a speed, otherwise there can be no cause and effect, time must elapse, speed must occur, this speed is C. or what am I missing that you are considering? @@kylelochlann5053

[@bettafish6]

@@kylelochlann5053 light takes 7 mins from Sun to get to Earth. If the sun dissapears, guess how long till Earth get free of the sun gravity ? ding ding ding 7 mins. speed of casuality

[@shamseroomi]

I watched a gazillions of videos, all explaining vague concepts regarding E=mc². Thank goodness, I finally found yours and it was definitely worth the time. The way you made us understand things through dialogues is truly commendable. I hope you keep working on such informative videos. 🙏😇

[@CalamitousJonathan]

@shamseroomi I was the one that wrote the equation E=MC2 for Albert Einstein. Energy=mass converted twice. It is relative to space travel Using a Warp Drive Engine you need to expand mass behind the spaceship, not just warp space infront of the ship. To do so the equations E=MC2 has to do with using H20 one part hydrogen and 2 parts oxygen as exhaust to convert the gases into water that then converts again to ice and expands allowing forward momentum from the expansion of the ice. Which allows the bent space infront of the shuttle to act as a wave and pull the ship along.

[@atlast7035]

Wouldn't it be 1 part oxygen and 2 parts hydrogen? And E=mc^2 rather than E=MC2? I'm only guessing of course; I don't have a space ship... anymore :(@@CalamitousJonathan

[@user-gv4cx7vz8t]

​@@atlast7035He's obviously using superenergetic oxygen to make the propellant for his ship. The extra oxygen energy is converted to extra velocity as the water becomes ordinary expanded and depleted ice. It's elementary!

[@anusthanbhandari2766]

I am still confused. I thought of energy as like the sum of momentum energy(pc)^2 and "mass" enegy(mc^2)^2. Hence, E^2=(pc)^2+(mc^2)^2. Hence photons have energy when "m" is 0 as then E=pc. so, E=h 𝜆 . so, E=h f c. Hence the energy of photon is just plancks constant times speed of light times frequency. So just higher frequency=higher Energy. So this is complex for my brain aldready. And this video comes in and confuses me more. Can someone elaborate please?

[@anusthanbhandari2766]

@@CalamitousJonathan Welp Im not getting my answers here I see.

[@peachesurf]

The whole dynamic of having a conversation with Einstein himself was a nice touch. Not sure if that was intentional or from the Brilliant course you had mentioned earlier, but this made intuitive sense from a conversational standpoint, which makes this accessible to people who may not share a background of metaphysics. Great work.

[@naufalmEZa]

Pardon, metaphysics?

[@chadlharris]

I’ve watched so many educational physics videos that discuss the speed of light and NEVER have i heard a better explanation of the speed of light. And it didn’t require a bunch of confusing equations. Why aren’t there more people breaking it down as clearly as you have?! Thank you so much for bringing these concepts to a level we can digest. You instantly gained a new fan just from this one video. i will now watch everything you produce! Please keep it coming. i wish you great success on KZbin. You deserve it!

[@bminerrolltide]

The fact that total energy (Et) is the sum of the energy at rest (Er) and energy of motion (Em) reminds me of how the total velocity in spacetime (c) is the sum of the velocity through space and the velocity through time.

[@guizarbayardoemmanuelisaia1718]

Conclusion: photons are muscles

[@SuperLemons-ve69o]

That all makes sense now about why am i so slim..

[@sashimi879]

​@@SuperLemons-ve69oIt's because ur black

[@Rammahuk]

And massive muscles must be travelling at the speed of light :)))

[@DavidMazhambe-r9e]

Muscles or mass less? 🤔

[@jeffcarey3045]

Then why aren't gym bros very bright?

[@edgarkempf3515]

Mahesh, it's such a pleasure to watch your videos after an exhausting day. It brings back all the moving energy to a rest, you open doors in my brain and let me even dream of what e=mc2 can do

[@Tom-zy6ke]

The single best lecture I have heard, probably ever (and I'm quite old). Now all I need to do is watch it a few more times to "inwardly digest" it!

[@bass2564]

This is the single best video on the subject of E=mc^2 I have ever seen. Lot's of handwavy arguments, but with _all_ the correct intuitions (at least as far as a dropout physics major like me can see), and delivered with impeccable rhythm, timing, and artistic flair rarely seen. Thank you! (I'll be heading in the direction of your other videos, and if there's one about gravity, I'll be forever sold.)

[@MTWDD]

Wow, I'm blown away. I clicked on this video thinking I'd not understand a single thing because I'm still 15 and we get nothing like this at school. Have had this exact question in my head for 3 or 4 years now. I'm so happy to have understood this concept with no effort, not wasting too much time and tackling it from different perspectives. Definitely has been a very productive 20 minutes. Big W 💪

[@darkheart5757]

Stop flexing and go do something with the knowledge kiddo

[@MTWDD]

@@darkheart5757 do what? 🤣

[@kaithedoge5861]

​@@darkheart5757where's the flexing lmao

[@nathyatta]

@@MTWDDdon’t worry about him mate. There’s no ‘flexing’ at all what you said. I don’t know what he’s on about.

[@parentfake306]

17:46 beautiful it is. And you made it that way. Thank you for being a great teacher.

[@gameofpj3286]

I really love how you always tackle the exact questions that I have while watching these videos ❤ You're a really good teacher!

[@Mahesh_Shenoy]

Super super glad to hear this :)

[@adlerbrietzke]

I really appreciate that you bring up the thoughts you had before the understanding of the concept and that you walk trough the solution to the problems that show up exploring the possibilities. It does give a better intuition.

[@Filip-ci3ng]

You rock bruh, best attempt to explain the topic I’ve heard so far

[@thelordnelson]

I love the style that you have to explain difficult concepts. Not only does you passion and excitement for the subject inspire you challenge the why rather than just replay the theory in an easier language. For everything I learn I come away with more questions than I started with, and you too always pose those questions that people are no doubt asking themselves. That helps to solidify understanding. Thank you. Love it.

[@glasfish]

New subscriber here. The clarity and energy of your delivery is what this subject deserves. You are doing a great job.

[@pedrofelipefreitas2666]

Just found your channel and this is really great work! I've watched countless videos about relativity on youtube, as a physics enthusiast, and your's was the most clear one. Your format of having a virtual conversation is honestly great for learning, because there's a certain narrative behind it, and humans REALLY like narratives, so remembering and understanding are improved significantly.

[@opposite4893]

It would have been helpful to explain that E = mc^2 is not the full equation. The full equation includes momentum of massless particles such as photons. Full equation here: en.m.wikipedia.org/wiki/Energy%E2%80%93momentum_relation

[@superboy3633]

Thanks.

[@enweghikomputa8153]

This is the comment I was looking for! Thank you

[@eclipse369.]

there are no massless particles called photons though its scientists cherry picking stuff take an emr wave, then zoom in at any point and theres your so called photon...even then its not a particle but a measurement

[@BaltazarConejo-uc8ru]

OK but |p|c can still be written in terms of mass p = gamma m v anf still you get 0. Your problem is that you dont know what m=0 even means.

[@cyclopsmouse2247]

exactly~!

[@MerlinSunch]

Such a nice explanation! I just finished my GCSE, but it all made sense because you explained them very simply

[@sabreensameena4967]

Hey Mahesh. First of all, thanks for uploading this video as I was able to understand the relation E=mc^2 after years of trying hard. But I do have a question to ask. The speed of causality, being the ultimate speed limit of the universe, remains as c in water as well. This can be verified by the phenomenon of Cherenkov radiation. But by convention, light travels slower than c in a denser medium like water. Here the speed of photon v

[@eitaje]

No, photons don't acquire mass in water. The apparent slower speed is an emergent property from quantum interactions between photons and the medium, not from any fundamental change in the photon's properties.

[@piotr.ziolo.]

I'm not a physicist but I was always curious about physics and tried to answer some questions that I had, especially about relativity. I read some books, I listened to videos, but found no logically coherent answer. And now with every one of your videos I learn those answers. It's amazing and pretty crazy that the brightest scientists in the world can't properly explain those topics, but you can!

[@piotrek7633]

Horrible explanation and i didnt understand anything sadly

[@piotr.ziolo.]

@@piotrek7633This explanation is perfect because it tackles all potential issues, while no other video does that. In all other explanations one can think of counterarguments. Here all potential counterarguments are covered. You also made a logical mistake - the fact that you don't understand something does not mean it was a bad explanation. There are many splendid videos debunking flat earth claims and yet flerfers still don't understand those.

[@Shrutithenerd]

Sir your passion for teaching us physics and giving us more clear picture of how, why something happens is really amazing, I have never seen someone as excited physics teacher like you who really wants us to know the more deeper mechanics of physics. Thank you so much sir. ☺️

[@Mahesh_Shenoy]

Thanks a ton. Made my day :)

[@888siddharth]

Thanks to your explanation, now I can actually show off my knowledge of speed of light in conversations that will never happen outside my own head.

[@foodisgood17]

I took several physics courses in high school and college (including special relativity) and have watched many videos on this subject. This video is the best, most comprehensible and intuitive explanation of these concepts I have ever seen. If physics had ever been taught to me with this much approachable clarity I'd probably be a physicist now :)

[@LS-jv4uh]

You really are one of the greatest teachers I have ever seen.

[@Swarnim-md7xj]

sir, as a high school student from India, i admire the way you have gone through the analysis and explanation.

[@mike814031]

i just love videos that live up to their expectations! (Near the end of the video) this is one of the best descriptions of light I have ever heard! truly a very good & intuitive description different than anything else Ive heard yet and also superior to anything else, nice job!

[@JmaK17]

You just earned a new subscriber my friend! I absolutely love your energy, enthusiasm and excitement! I also really enjoyed the kind of conversational format of posing each of the questions and then taking us on a journey to discover the answers and reasoning behind them.

[@thedeemon]

Great presentation! For me these things got much clearer when I started learning QFT: Klein-Gordon equation, Dirac and Proca equations, these really show how mass and momentum are related for waves, how those relativistic properties work, how mass works on the level of wave functions. There you see how having or not having rest mass affects wave's group velocity, how it directly affects whether the particle will move at c or less.

[@tempname8263]

Alternative take! Elementary particles, by default, have no mass. They are just waves propagating through space at the speed of light (speed of waves). To tell whether or not a wave has big momentum (energy), you need to take a look at how close it's peaks are. But when those particles interact with one another (meaning, when they attract one another), they stop travelling in straight lines, but take more complex path, thus propagating at less than c. These interactions (that part of momentum that is forced to travel in circles instead of going anywhere) are called mass.

[@jamesbarber5410]

No I don’t know any more about why photons are massless allegedly. However, your concise explanation in the last half of this video enlightened me as to why we use C and what precisely the speed limit is. This honestly was not clear to me for 43 years of my life and now seems obvious, like I always knew it. The distinction between C and the speed of light is more significant than most people give it credit for. Thank you for this simple but profound explanation.

[@rozhjabar729]

So I'm not fat I just have more energy.

[@Piano_Tutorials_2023]

Real 😂

[@Realisation19]

😂😂😂 people stay away from you whenever you quarrel with someone

[@DM-wu5hn]

More fuel.

[@trendingmekal]

Damn

[@a5cent]

😂😂🎉

[@Delta0030]

Just completed a course on General Relativity in uni (man what a final). Was following along well with everything and enjoying seeing familiar concepts, but the speed of causality revelation was so amazing. Tied it all up and taught me something my prof and textbook never mentioned when we were going through SR. Thanks!!

[@riodasperolas]

Brilliant lesson! Communication at the speed of brilliance. Congratulations squared! And thank you

[@a5cent]

Ok. Best introductory lecture on e=mc^2 ever made. Hats off to you sir!

[@k_a_bizzle]

First video, hit the sub button probably 2 minutes in. I love the mock Socratic dialogue you have going with the ghost of Einstein haha. You have a REAL gift for teaching! Looking forward to more.

[@TheCoolcaspar]

Fantastic video, you really have an absolutely amazing way of describing all these inherently very difficult concepts to grasp, that even me a 25 year old who have never really really studied physics can follow it and be engaged and entertainer. Diffently adding you to me subscribtions. Keep up the amazing work my friend, I cannot wait to see more from you ❤

[@autismuskaefer]

Your videos are always so good. I haven't seen any other science KZbinr with better explanations, especially with these Quantum-Topics. Thank you so much!

[@alindegren6144]

What was quantum about this?

[@autismuskaefer]

@@alindegren6144 Any small particles (even light) can be described as quantum-objects in physics. Of course we haven't discussed any quantised energy states or used the mathematical formalism used in quantum mechanics but it's kind of heading in this direction right?

[@alindegren6144]

@@autismuskaefer They can indeed, but that's a completely different field (no pun intended).

[@Mahesh_Shenoy]

Thanks :)

[@obliviouz]

8:00 - this is similar to the best way it's been explained to me: speed (c) and mass (m) are the same thing and all objects have a certain combined [mass plus speed] value. So that means - most objects have 99...% of that value as mass because they're moving either not at all or at very small speeds. But a photon has all of that value as speed, so that they have zero of that value as rest mass.

[@colorx6030]

This is really amazing. I would've never thought I'd watch a video where it could replicate the excitement I get whenever I understand a new concept.

The way you explain things is remarkable. Can't wait to watch the rest of your videos. You have a new subscriber and keep up the great work!

[@Mahesh_Shenoy]

Thank you, and welcome to the community :)

[@TheEtbetween]

Uhm I not sure I agree! If a photon interacts within a material it would slow down. At that time then base on theory it should have weight!

[@unitedstatesCIA]

What a great video I wish that my teachers taught us like this

[@pauls5745]

recalling how dry and boring physics was in high school...

[@bobthebomb1596]

As a chemist who could never get his head around physics, I gained more understanding of Einstein's equation from that video than my entire time in formal education! Well done sir.

[@jura3760]

You earned yourself a new subscriber. This video was probably the best explained physics video i have ever seen, i really liked that you tried to debunk what you said a minute ago but then clarified why that wouldtn work

[@MerlinsDrAgon]

Let me share my one-sentence explanation to this video’s question, I’m sure the post dives deeper into ample reasoning to substantiate the claim.. but if you’re like me with limited time for learning after work, and would like to avoid investing 22min on a single-source explainer, this small answer should suffice - Photons travel at the speed of light, and for this to be true, they MUST BE MASSLESS - You’re free do some basic googling as to why this is the case, but reading the aforementioned (rather vague) sentence is all you need to know to get you started in the right direction. Sometimes doing the digging yourself allows for a better understanding of the concepts and insights than a singular video can, and in a fraction of the time.

[@brodhuppe1592]

Finally a video that explains e=mc^2 for normal people. Great job

[@_notch]

One small comment about the energy of of a moving object: Motion is relative. If two people who felt like they are stationary where to slam into each other, it doesn't matter who was moving. What matters is how fast the both of you were moving towards each other. In our daily situation where we are used to everyone comparing everything to the large (very much in motion) planet we're on, so we often think of "motion" as being stationary in reference to the earth, but when someone hits you with a car, the definition that includes motion in the math equation, says that BOTH of you get higher mass, much like some planet we smack into would. Because who's to tell which one was stationary? It was just orbiting something far away and our paths crossed.

[@JakubS]

Einstein wouldn't have told us about the Higgs field, because he didn't know the Higgs field exists. He died a decade before the Higgs boson was suggested to exist.

[@geneticjen9312]

When people say "Einstein says" or "Everett says" etc they're talking about their ideas and theories. It's not a literal quote from the person. You might hear someone say "Newton says we can't do that" even if they're talking about technologies that existed after Newton's lifetime

[@JakubS]

@@geneticjen9312 yeah, but those technologies would still abide by Newtonian physics, meanwhile the Higgs Field doesn't obey any physics that Einstein knew

[@JohnMatylonek-h1o]

Could it also be said, in a simpler explanation, that the photon just does not interact with the Higgs field?

[@kevinbeazy]

Actually he did. Black holes weren’t found until after his death either.

[@ohlookadandelion]

​@@JohnMatylonek-h1othat is such a good question that I want an answer to as well :(

[@guydude3320]

So at 21:46 @Mahesh_Shenoy does that mean photons travel in water , they have mass ? Because it is lesser than speed of light in vacuum

[@shreekararaghavan1471]

No, light travels at c itself, it just goes zigzag bouncing off water molecules so it appears to be moving less than c

[@gravit8378]

@@shreekararaghavan1471 he is referring to the phenomenon called refraction and yes when light passes through the water it's speed decreases significantly roughly 1 /3 of its speed gets affected. In vaccum it's 3 lakh km per second in water it's 2 lakh km per second

[@AryanBanyal-g3j]

​@@gravit8378 It just appears that way in macro scale. On a micro scale the distance traveled by photon is more than the distance traveled in vaccum because the photon is bouncing back and forth between molecules before actually moving "ahead".

[@fidel_soto]

🤯

[@TrungNguyen-io5ro]

I don't get it at 15:00 why m goes to infinity at c. Can someone help me with that?

[@2losersplayingroblox]

because you have infinite kinetic energy when moving at the speed of light. Your mass is also infinite

[@CB256]

m=m0/√1-v^2/c^2

[@CB256]

But how we have finite mass for photon according to this equation as he says as the rest mass would be zero right?,0/0???

[@HarshavardhanGavicherla]

"Physics is not about understanding reality. It is about creating models that simulate reality." OMG. You have no idea how much of an existencial crisis burden you have took of my shoulders. I am watching your channel since last 10 hours, it answered so many of my burning questions in my brain and more importantly gave an intuitive sense of the reality.

[@quantenschaum]

The Tennis ball thing is wrong. It gets heavier due to kinetic energy, but kinetic energy is relative. This happens in particle accelerators when getting close to light speed, particles get heavier not faster. Total energy = total mass.

[@skitzcrasher]

You are incorrect sir.

[@nopphanmajaric5488]

But photon travels slower than c almost all the time (only in perfect vacuum that it can go as fast as c). Still it has no mass. ? ? ?

[@nitansh.]

i had the same doubt, even my school physics teacher had no answer

[@boonheeliew2488]

You can refer to "Science Alert, current research in Physics" for the answer.

[@mush10]

Same question

[@boonheeliew2488]

you can see mass when light is stopped, you see mass on the screen. During light massless traveling , it is momentum instead of mass. you will not see light, you will not sense light, unless you stop it, then you will have both mass and momentum. Momentum is because of reflection, refraction, diffusion ..... of light. You can refer to "Science Alert, current research in Physics" 1. no light interference, 2. light speed remains

[@parentfake306]

Why should I never trust an atom?

[@joshmilne1268]

Because they make up everything!

[@mrinaldbhat9921]

Because they make up everything.

[@skitzcrasher]

Because they make up everything 😏

[@GOREilla.]

Hm, actually the moving mass of the tennis ball does indeed has an increased energy considering the friction with the air outside and also the movement of the air molecules inside the tennis ball.

[@bhuerrorinsights]

"Never trust an atom"

[@RandomMe93]

A friend brought this topic to me as well, "if E=mc² is true, how can light have no mass?" I have a hypothesis but this video does a great job explaining the things that i was thinking of in a way that is understood by others. Thanks and keep making this videos👍🏽👍🏽

[@abovetheriver]

I have been trying to wrap my mind around these concepts for years. Never had it explained this ways which really helped me so much in my understanding. Thank you very much for this fantastic presentation. 😁

[@scrwd8301]

This video and explanation are so good! I don't usually watch physics videos outside of lectures, but I couldn't stop watching this one. I can feel my love for physics sparking again (even though im struggling with it ) 💡⚛️

[@surbhisareen6695]

Hi Mahesh .. KE is actually differnece of energy in motion minus energy at rest, We can prove mathematically that it comes out to be 1/2 mv2 if v

[@narfwhals7843]

We can. That's relativistic mass. It's sometimes convenient because it allows us to use p=mv without modification. But it also leads to misunderstandings, like thinking fast objects should form black holes because their mass increases. So, this concept is largely abandoned in contemporary physics, and mass just means "rest mass".

[@subcitizen2012]

I moved states once and my dad came and helped move me with his full sized van. Being that I was up in the mountains and in a part of the country that was high altitude and the return trip was mostly a long slow gradient back down to the plains, the added inertial mass from all of my furniture acted like a stored battery of mass energy that was fully charged once we were at max speed. This full sized van, fully loaded, on that first tank of gas was getting almost 6 times better mileage. Shocking. Once the object was in motion, the engine and energy in the gasoline didn't have to work as hard to maintain the highway speeds. That tank of gas was around 70mpg. Amazing physics lesson, as terrible as I am at repeating it in a technical sense. My dad couldn't believe it and thought something was mechanically wrong lol.

[@Bouda_sr]

That’s why when things hit at a moving speed they feel heavier or hit harder than it weighs. The energy adds the weight when it’s brought to a stop! I don’t know if that’s right. But I know nothing about physics. But I think this made sense. Great video!

[@Sadlander2]

*_Mass = Happiness_* I'm not trying to be funny, just bear with me... At some point in my life, nothing seemed to make me happy anymore. I tried medication, drugs, entertainment and many other things but nothing worked (or it worked for a minute or two). I even went to therapy, read a lot and learned a thing or two about depression and happiness and feeling OK. This video reminded me of what people say: happiness must come from the inside. They also say that humans need connections with other humans and this video is a great analogy for that: You apply force to a spring, so you add to its mass because you changed its inside. You heat something up, same thing happens but if you throw a ball, you don't change the ball, you only change what surrounds it, its outside. In other words, using drugs or alcohol or entertainment or anything superficial will only last for so long, just like a ball that you throw. However, if you have interactions with people and they change you, inside of you, that's like adding mass, that's adding happiness inside of you.

[@endycaceres7327]

So much for objective reality 😭 the deeper I delve into physics , the more subjective reality seems. Great explanation. Please do more ! (The Heisenberg principle preferably if you can , thank you in advance if you already have)

[@Chrisl2551]

Wow - this is a revelation! The speed of light being a fundamental limit and the same from all frames of reference seemed arbitrary and never made sense to me (just something I had to simply accept). However the speed of causality being the same makes every sense. That sort of insight is just mind blowing and an absolute joy. I have been bouncing around (metaphorically!) ever since I watched your video and will continue doing so until I can bounce no more!

[@worldnotworld]

VERY well done! Showed this to my private students: they needed just such a nudge as yours, followed by a follow-up nudge from me, and voila! REALLY good. Thank you.

[@Nter10-ut2iz]

Wow! Your explanation is so pure. I have seen the best explanation and it's really so understandable. Even, high school students can easily get it. Thanks for the video. You earned me as a subscriber.

[@mikaelfoster9726]

17:10 Rupert Sheldrake points this out as a major flaw with modern science, weve abandoned understanding for models because we "cant understand", but science is based on the idea we can.

[@Dayjob351]

62 years old and finally got a great representation and explanation, thank you.

[@Beatyofeet32]

This video is incredible. You explained something that's not at all "easy" in such an easy to understand way and there wasn't a single cut that I noticed. To maintain such a perfect pacing for over 21 minutes without editing is mind-blowing. It's rare to see a video run for 10 straight seconds without a cut these days and they're usually not covering anything half as difficult. Instant sub.

[@kylec4103]

Could not agree more!!

[@SpiritofPluto]

Excellent video, excellent. It took me a while to get that point about light "never being at rest". Really, really nice. I've been watching your videos for a while now, you are an excellent teacher, no doubt whatsoever-

[@abucs]

Your presentation style is brilliant. Upbeat, informative and i like your self-deprecating humour. The idea to have mock conversations with Einstein makes the whole presentation easy to listen to. I particularly found interesting the words you put in Einstein's mouth that physics was not about understanding reality but building models to approximate and mimic reality. Very profound.

[@nariminator8337]

I just recently found your channel and am extremely happy about this find. Your INSANELY GOOD ... Like unimaginably good really ... at explaining these more complex concepts in more simple technical language ... Well simple enough for a master's mechanical engineer from my perspective at least 😅. And your passion and love for science, which is clearly visible, just makes the process of learning with you a tremendously joyful ride! Keep up the great work my friend.

[@deo-ni7kz]

This is so far the simplest and understandable explanation I have ever come across. Thank you

[@8532556]

excellent line of questioning to get to the bottom of the problem, I’m not exaggerate saying that this kind of video is what push humanity forward

[@tomasbielak5411]

First time watching your videos, and I must say you are awesome, I didn’t like physics that much, but your enthusiasm makes me wanna reconsider that. Great work.

[@jayb5596]

A deeper look into the equation E=MC² to begin, we will denote M as total mass and m1 dark m2 light as fractional representations of total mass M. This allows m1 and m2 to function as fractions of M and multiply as such. Space: Variations in spatial coordinates affect how 𝑐1 and 𝑐2 are perceived. For example, the distribution of mass or energy in space can change how these quantities are measured. Time: Time variations can affect 𝑐1 and 𝑐2 as the system evolves. For example, kinetic and potential energies change over time. In relativity, measurements of time and space depend on the observer’s frame of reference. This means that 𝑐1 and 𝑐2 can vary based on relative motion and gravitational effects. Dynamic Adjustment: c1(x,t) and c2(x,t) where x represents spatial coordinates and t represents time. Sum and Product Relationships: c1(x,t) + c2(x,t)=C c1(x,t) × c2(x,t)=C² Here, 𝐶 and C² are constants, while 𝑐1 and 𝑐2 vary with space and time. Kinetic and Potential Energy: In a system with varying spatial distribution, 𝑐1 and 𝑐2 represent different forms of energy. As the system evolves in time and space, these energies adjust while maintaining their sum and product relationships. Gravitational Effects: In a gravitational field, mass distribution affects the measurements of energy and can cause 𝑐1 and 𝑐2 to vary depending on location and time. Relativistic Variations: For different observers in relative motion, c1 and c2 might be perceived differently due to time dilation and length contraction. Despite these variations, the fundamental relationships 𝑐1+𝑐2=𝐶 and c1×𝑐2=C² hold true within each observer’s frame. Spacetime Interactions: Changes in spacetime curvature and metric can affect 𝑐1 and 𝑐2, but their interactions still reflect the underlying constants. Functions of Space and Time: Define c1(x,t) and c2 (x,t) such that: c1(x,t)+c2(x,t)=C c1(x,t)xc2(x,t)=C² Consistency: Ensure that as x and t vary, c1 and 𝑐2 adjust dynamically but satisfy these equations at every point. Observer Frames: For different frames of reference, adjust c1(x,t) and c2(x,t) based on the observer’s motion and gravitational field. The relationships c1+c2=C and c1×c2=C² remain consistent in each frame, reflecting how energy and mass interact in spacetime. Quadratic Relationship: The relationship between 𝑐1 and c2 can be framed as roots of a quadratic equation: x2−Cx+c2=0 where 𝑐1 and c2 are the roots. The dynamic nature means that for different values of t, 𝑐1 and 𝑐2 adjust accordingly but still satisfy the equation Consider a specific example where C and C² are given: Let C=5 and C²=6. The quadratic equation becomes: 𝑥2−5𝑥+6=0 factoring this, (x−2)(x−3)=0 so the roots are c1=2 and c2=3. Sum: c1 + c2 = 2 + 3=5 Product: c1 × c2 = 2 × 3=6 If 𝑐1 and 𝑐2 are dynamic functions of a parameter t, then they can adjust while maintaining the sum and product relationships. For example suppose 𝑐1(𝑡)=𝛼(𝑡) and 𝑐2(𝑡)=𝛽(𝑡) you could define, 𝛼(𝑡)+𝛽(𝑡)=𝐶 & α(t)×β(t)=C² as t changes α(t) and 𝛽(𝑡) adjust, but their sum and product still match the specified C and C².

[@veritas932]

thank you for your channel. It has helped me understand particle physics from a layman point of view. A lot of the questions you asked are the same questions I asked but never found an answer.

[@inanovalisinc.2855]

Excellent video explaining this misunderstood concept. Being a retired electrical engineer, I congratulate you for your excellent presentation -:)