Why light has energy, but no mass? (Understanding E = mc2)

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.
Chapters:
00:00 Why photons have no mass (vague "explanations")
01:19 What is mass, exactly?
04:33 Understanding E = mc2
05:50 Does kinetic energy add more mass?
07:35 Total energy
09:15 Finding mass of light
10:05 Sponsor shoutout
1107 Photons have no rest frame (hence no mass)
12:32 Relativistic mass?
14:05 Why we don't use relativistic mass anymore
17:48 Speed of causality and massive photons?
20:45 Summarising in 2 lines
Photons have energy. According to Einstein's E = mc^2, they should have mass too. But, photon's are massless. Why? Why E = mc^2 doesn't apply to photons? Why massless particles always travel at the speed of 'c'?
This videos hopes to connect all the pieces together to provide a much more profound understanding of this topic. By the end of the video, you should have clear idea why we say light (or photons) are massless and why any massless particles should always travel at c. We will also see that c is actually the speed of causality.
This video was sponsored by Brilliant
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[@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!

[@xyz32442]

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!

[@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 😂

[@chutii77]

😂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.

[@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!

[@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!

[@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.

[@user-ib1fu6bp9e]

and the Iraqi me is reading this comment

[@nullpointerworks4036]

@@user-ib1fu6bp9e 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 :)

[@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.

[@glasfish]

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

[@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

[@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.

[@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.

[@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.

[@Cy_Guy]

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.

[@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

[@iandonkin3759]

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

[@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!

[@UnLoupEnBleu]

I gotta say (even it's a bit late) but only with the 6 minutes i watched so far you convinced me to subscribed, never have I heard so accessible explanation and I think that's really impressive (given the difficulties of the subject). Congrat on your lecture !

[@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 :)

[@elquesohombre9931]

I’m used to good lecturers on KZbin and I usually don’t leave comments like this but this was INCREDIBLY WELL DONE.

[@ecco256]

Even though I thought I roughly understood this, you have a gift in making topics feel incredibly intuitive that really adds a lot to my understanding. Thanks for making these!

[@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?

[@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

[@gabewotton3506]

​@@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

[@user-qi9bq6oy1t]

You have a gift of explaining things in a refreshing and enjoyable way. I have seen a few videos of you explaining things around relativity etc. and even though I already have a general understanding of these things, you bring everything so much closer. Keep going with these videos, great work, highly recommended for anyone interested in physics!

[@Filip-ci3ng]

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

[@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!

[@raffaelechinotti5244]

Mahesh you're THE MAN I swear thank you for making me understand the fact that speed of light was just an approximation for the speed of causality, I was desperately trying to understand this, this is the best video about E=MC2 just because of this little notion you made clear in your video, you got another sub, thanks Mahesh

[@efebadin1453]

I am currently a senior high school numerical student in Turkey and we have seen in class that there is no way to add mass to light and that such a thing is not possible, but I did not believe that this would be possible and I did as much research as I could on this subject for about 2 weeks, but I could not come to a conclusion. Frankly, I even looked at how the Higgs boson, which gives mass, works, but there was no result. No matter who I share all this with, everyone says you have to go to school first, but I think I can survive if I get enough information. I hope I get something from this video. This video came across me just in time.

[@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?

[@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.

[@TheDjacob]

So my hole life I have been watching this stuff, now I understand it in my head. This stuff was always so perplexing and your videos are helping me comprehend your other videos! I love this guy

[@straightdrive6192]

Bro- your videos are awesome, keep up. I get to learn so much new stuff and different angles to the same known principles in physics.

[@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.

[@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 :)

[@craigsparton]

This was very well explained, and while I had a small grasp of the concept I now understand it much more thoroughly. Thank you!

[@yiannchrst]

this is so good. I've seen other videos about the subject and this one is one of the best i've seen!

[@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.)

[@DinosaurDWPPL]

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.

[@tonyreno3168]

I like the video a lot, but I was hoping you'd have explained how different photons can have different energies. I like the video because you opened a new viewpoint to me. You gave me directions for new questions. I didn't quite buy the argument that photons at < c have rest mass. But everything before that point really gave me a big aha and I'm going to need to think about it a while to answer my new questions. Great insights! You definitely have earned my subscription.

[@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.

[@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!!

[@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.

[@ChrisCM23]

Amazing Mahesh The way you explain things is so intuitive and I’ve learned a great deal from you. Please carry on producing great videos 👍

[@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.

[@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.

[@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.

[@rossk4864]

I'm new to this channel and a new subscriber. This was a very succinct and understandable explanation of E=mc^2. Added to my limited understanding, after taking a course in quantum mechanics a little over 40 years ago, it all makes sense now. You are a fine educator! Great job!! Thank you!!!

[@ronaldorodriguesdasilva4302]

From Brasil, Rio de Janeiro, congratulations, very very good ...the insites of these concepts you give us are truly remarcable ...thanks a lot !!

[@LS-jv4uh]

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

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!

[@thanasisspyropoulos7126]

Great explainer! Amazing break down of complicated concepts with easy to follow examples. You just gained a subscriber!

[@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 !🙂

[@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 ❤

[@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 :)))

[@user-iv9st9ux5q]

Muscles or mass less? 🤔

[@pragyanhazarika2354]

What a great explanation, the way the visuals are shown truly fascinatates every physics lover, hope to get more explanatory videos like this❤️

[@user-qo5wi7pb9m]

I just love how much emotions you put into explaining!!! Instant sub

[@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 :)

[@riodasperolas]

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

[@theodorepage6087]

At 75y old and never studied, you my friend explained it very well, thank you, dublin Ireland 🇮🇪

[@franktothemax]

This should be required viewing for anyone trying to understand this. Incredible work my man! Even better presentation!

[@badbrooko]

The more I understand the more I realise I know nothing 😂

[@sunbeam9222]

That's what understanding does 🎉 a big great lesson in humility and the gift of neverending curiosity.

[@Fluffypotatoes4]

Same

[@IsaacNewton-vn8xc]

Exactly! That's the point brother. knowledge is something which is endless in many aspects you can take a bunch of knowledge about politics,science, engineering, mathematics, information technology, computer programming etc... So the conclusion comes out to be that knowledge is infinite so just be curious about taking as much knowledge as possible!

[@jorgefrade8900]

Wait until you find out about the e^2=p^2 * c^2 + m^2 * c^4

[@badbrooko]

@@jorgefrade8900 And that is the formula too ???

[@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 :)

[@helterskelter416]

17:07 that one sentence you spoke here made everything make so much more sense.

[@mmotsenbocker]

Thank you for this insight: "C is the speed of causality." This is consistent with the view that photons do not exist. When A interacts with B, this happens with the speed of causality. The strength of interaction shows up as frequency of the energy transferred. The interaction itself is termed a photon. Feynman taught us that many, many mulltiples of "photons"are constantly being exchanged between particles. Another intriguing question is the nature of standing wave energy of a mass particle and "traveling wave," which emits as a "photon" . I would love a lecture devoted to this topic.

[@Swarnim-md7xj]

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

[@RajaBabu-ur5kf]

Wow wow finally getting sponsored from brilliant, you deserve it well man!! Great videos as always

[@Mahesh_Shenoy]

Yes, I was so happy when I first received their email.

[@RetiredNavyAO1]

The best explanation of E=MC2 I have ever heard…well done sir

[@chadfrazer4110]

VERY WELL DONE. And I'd like to add, your shirt made me chuckle long enough that I had to rewind your video.

[@swamynathansanthanam1812]

Sir,if you post videos on length contraction and time dilation explanation. It will be very helpful. Please consider this sir

[@cameronhudson1993]

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~!

[@OneTrueBadShoe]

The way you explain things is brilliant.

[@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

[@gualbertovega3218]

Nobody explains this advanced concepts better 👍👏

[@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!!

[@rh5842]

This was very well done and the enthusiasm made a complex topic enjoyable to watch.

[@rickmolchan3421]

I had this epiphany last night thinking about Einstein’s equation….how I found this video. It left me with the conclusion that time and matter do not exist. That there is only energy and movement in a constant present. Mind blowing.

[@Harv72b]

I'm 1:20 into my first ever viewing of your channel. I have no idea if you're going to convince me of anything or even if I'm going to understand all the concepts you're going to dive into, but you're getting the like right now just from your infectiously excited demeanor. It's not that difficult to pick up on "camera personality" vs. somebody who is truly excited about the topic, and it's always refreshing to find a new channel that falls into the latter category!

[@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 :)

[@jasmint6703]

Enthusiasm for this is contagious! I look forward to more of your videos.

[@manzcube]

Brilliant video! The exampled explanations and how conclusions are made are great

[@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

[@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

[@user-xe4fm1sr7r]

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

[@Donnouri1]

Really good content mate! So difficult and know i understand it much better, why i always thought i understand it 😅 Combined with the sincere passion on the topic this is great content. I think if you make more of these on fundamental topics (QM?) Would be awesome and you could really blow up 👍🏼 grtz from Netherlands

[@SuperImPrOv]

I am actually cry laughing here at 7:14, that tennis ball analogy made so much sense and it all hit me instantly. I could almost instantly see the relativistic point of view. Bravo.

[@yungchoppa391]

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

[@pauls5745]

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

[@brodhuppe1592]

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

[@Apollocreed2076]

You explained this so beautifully! THANK YOU!

[@MicrowaveOvenVideo]

absolutely incredible explanation and insight on the actual practical application of models and why we are particular with them

[@abrsih]

Truly one of the most beautiful explanations of this formula i ever heard. Not only was it clear, but the excitement of you teaching it made me excited to learn it. Keep up the good work. 👍

[@Mahesh_Shenoy]

Thank you, thank you :)

[@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.

[@sexyndead]

You are so passionate about physics. It's fascinating!

[@SevAngelo0316]

I watched the whole video and it gave me a way deeper understanding of physics in general (unintended pun) (hey dont look at me look at his shirt) as much as a mark rober or veritasium video would teach me and the best part is not only he summarized this video but he also gave it chapters.

[@varsha_1703]

Quantum realm is really mysterious 🤫mahesh can you make video about recent physics noble prize topic" attosecond pulses of light " why it so significant... atleast make a short video about that❤

[@Mahesh_Shenoy]

Yea, I'll have to read up on it, though 😂

[@alindegren6144]

This isn't the quantum realm. Relativity is a classical theory.

[@davidwuhrer6704]

​@@alindegren6144No one said otherwise.

[@alindegren6144]

@@davidwuhrer6704 It's literally the first word of the comment.

[@user-kq2rp6nv6b]

As always your explanations are just delicious 😋😋❤❤

[@Mahesh_Shenoy]

Like a cookie?

[@user-kq2rp6nv6b]

@@Mahesh_Shenoy yeaaaa💕💕💕

[@mhorset]

wooow, maybe the first physics video that I feel proud of understanding at the ending, you are great

[@warrenharrison5572]

I have a book on understanding e= mc². I watched this before i read the book. Im still going to read the book but i feel you explained it simply enough I think when physics are taught or talked about we should be stating whether were assuming light has mass or not at rest.

[@TrungNguyen-io5ro]

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

[@IsaacNewton-vn8xc]

Let's understand it with the help of an example: Say, you have got a spaceship which can travel at the speed of light now here I'm not approximating it to be 99.99% of the speed of light I'm taking it to be the exact value i.e. 3 × 10^8 m/s. Once you reach that value your mass gets to infinity now that's exactly your question why mass goes to infinity see it's because according to Albert Einstein and many other great scientists nothing can travel at the speed of light and it is nearly impossible to reach the exact speed of light with a spaceship but still I'm imagining stuff out there so once you reach that speed, time on your watch slows down as compared to the Earth's watch now here starts the time dilation concept given by Einstein. If you have watched Interstellar you may know that when Cooper, Amelia and other crew members got to the Miller and man's planet orbiting a black hole, every hour they spent on that planet was equivalent to 7 years back on earth. Now that's because the intense gravitational pull of the black hole makes time extremely slow down. And in the last when Cooper returned after the whole mission 'Murph' ( Cooper's daughter) had become old and Cooper remained the same as he was when he had left for the mission. Let's say that you are the group of photos constituting the light all together so when you are at rest, you would be massless but when light starts travelling at the speed of light, photons have the mass which is known as motion mass. So photons have rest-less mass. The explainer in this video says that at the speed of light, your body will have infinite mass but photons integrating the light will have finite mass. Because photons are the ones which constitute the light so it's pretty obvious that they have finite mass but our body will have infinite mass because our body is not made up of photons, it is made up of cells. Now mass literally means the amount of matter present in a body now we know that mass can be converted into energy with the E=mc^2 equation. So when he says that mass goes to infinity he actually means it with the energy at light speed, your mass gets converted into energy now that's what we call is infinite now once you reach the normal velocity, that energy gets converted into mass again but to the original mass.

[@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

[@antitactic2994]

Just found your channel today. Lovin' the talks with ol' Alby!