Your Daily Equation#6: Relativistic Mass

[@Dr10Jeeps]

I'm a psychology professor with an interest in physics. I love these daily equations. Please keep on doing as many as you can. Thank you for your ability to promote and explain the beauty of physics!

[@petergreen5337]

Well said

[@hrshah8260]

Just one request keep this on!

[@navstar7334]

Just happened on this series... A Daily Equation - what a great & practical format for many of us folks. Liked the jousting analogy & KE explanation in this one 👍. Many thanks for the videos Brian😊!

[@rjohn19]

Thanks Brian- I'm 73, never took physics or calculus, and I was able to follow- not saying I could do it but I got the principles and will now watch all of these. Hate being house-bound when you've ignited my inner Cliff Klaven.

[@TheAdithya1991]

Thanks for the explanation! The example, despite being a bit contrived illustrates nicely the need for an increased mass - to conserve momentum. A less contrived way to show that a mass increase is required is to use the impulse momentum theorem viewed from an objects instantaneous rest frame and comparing it with the equation that arrives from a static frame at rest.

[@bluefinance153]

Could we please do the equation of the Wave function or the Harmonic oscillator

[@bobdevos9729]

YES PLZ

[@Eponick]

This series is great! Something to look forward to every day in these stressful times. This made me realize I've never heard a relativistic reasoning of escape velocity. Probably because its simpler in Newtonian terms but this would be much more interesting. For instance: How does the increasing energy/mass of the rocket affect the curve as you accelerate to escape velocity? Would a substantially larger mass have a much higher escape velocity or is it negligible? I know I can look it up but I may try to work it out on paper first. Thanks for everything you and the folks at WSF do! EDIT: Apparently I incorrectly assumed the mass of the escaping object mattered... Not sure how it doesn't matter at thought-experiment level masses, though. Ignoring factors like solar system instability if you were hauling a cube that was equal to the mass of mars it would have to greatly increase escape velocity since the earth would be pulled towards the ship as you accelerated. May try to work this out, but a fun side note (if i'm correct) you weigh approximately 1.6x your weight at 11.186km/s relative to your weight on earth.

[@petergreen5337]

Agreed

[@WalterBislin]

Very nice example with the 2 riders. Never seen before.

[@gachaland1234]

Hi Brian - great show. I would love you to show where in the Einstein equations can be found the singularities that led to the theoretical predictions of the existence of black holes.

[@ffggddss]

That involves some very heavy mathematics! And the Einstein equations you refer to, are the Einstein field equations (EFE) of General Relativity. They are a unified system of partial differential equations, whose solutions are the possible structures of spacetime, given possible distributions of mass-energy. The singularity comes, not directly from the EFE's, but from the Schwarzschild solution to those equations. That solution is the one that governs the gravitational field outside any spherically symmetric mass, including mundane cases, like the Earth, the Sun, planets & their satellites, etc.; as well as extreme cases, like white dwarves, neutron stars, & black holes. In the Schwarzschild solution, which is itself an equation, there is a factor that contains "r" (distance from the center of the body) in the denominator, so that when r=0, that term in the equation "blows up." In every case the Schwarzschild solution applies to, that equation ceases to apply inside the body (just as the Newtonian 1/r² dependence, from Newton's Law of Gravity [NLG] does!), so that the singularity is avoided - except for the black hole solution, in which there is no "body" any more - it's simply a region of extremely curved spacetime with a singularity at the center, where spacetime curvature is infinite. [Incidentally, in both the rel. and non-rel. models, it isn't the EFE or NLG that no longer apply inside a mass - they do! Rather, the solutions of those laws that apply there, are different.] Fred

[@dinghanxue704]

@@ffggddss thanks to your detailed explanation! but can I say it this way, singularity is more of a math object than a physics object because it's where all of our current theory fails.

[@ffggddss]

@@dinghanxue704 When one occurs in a physical theory, that theory must either be re-cast so as to eliminate the infinities (as happened in particle physics with "renormalization"), or it must be altered or discarded. Fred

[@michaelwest217]

Love your talks, truly awesome and thanks. This episode reminded me of a question I had ages ago on relativistic mass, which is: does it warp space and bend light with regards to an observer at “rest”? In other words if an object speed by fast enough would we see it shift the observed position of the stars behind it relative to us? Also, since the mass can get arbitrarily large based if velocity and the length is contracting could an object appear to be so massive and dense that it looked like a black hole to an outside observer? This certainly can’t be possible since if it was say a space ship they could slow down and then magically un-black hole themselves, I’m thinking there is something about relativistic mass I’m not getting, lol. Anyway, if you happen to read this any brief insight would be appreciated.

[@BadassRaiden]

I think the biggest thing i like about these, are that, now that school is out for most children and young adults, no one is learning anything. And if worst case scenario the education system falls apart (probably not likely but hey) then we still need not just the information out there to go and find, but we need those individuals who would pull information they know and understand, and instead of just lazying about and being the keepers of that information, they share it like this, often times information most people wouldnt bother to try to understand. This way, the most mind blowing of information, isnt lost in the crisis (again, probably not gonna happen, but i hear a lot of people talk about how thankful they are the internet is still operating). I once heard, maybe NGT talk about it, but something was said along the lines of, "if everyone who was knowledgeable enough to make a cell phone from scratch, how long would it take for us to reinvent it, if all those people disappeared?" Of course we arent only talkin about people disappearing but the information they carry with them being lost in time. It seems many civilizations succumb to this tragedy. Im just saying, teachers and professors, those with knowledge who's profession is to teach others, i think they should all be doing stuff like this, sharing their knowledge freely and openly.

[@irenemedvedev5422]

Thank you very much from New York. Looking forward to new episode every day!

[@petergreen5337]

Thank you very much Professers Greene

[@enotdetcelfer]

Wow, really wish I had learned this in school like this, it makes so much more sense to see the series expansion and to realize all the types of energy that goes into your "total mass" great stuff I hope you do more of these!

[@putinscat1208]

1) Matter warps space. 2) Space warps at the speed of light ( meaning if the Earth moves from point A to B, the space warping around it at those points has the speed of light restriction in the change of warpage ) 3) Now accelerate an object close to the speed of light, and try to see the resistance to change of the space warpage with an object that is moving at almost the maximum limit. This resistance of the entire universe's gravity warping thru very fast moving matter is why mass seems to increase, and why you can't get to speed of light limit. 4) Only by warping space around an object could you move faster.

[@RichardAlsenz]

Read Gauss! Gauss to Bessel Goettingen 9 April 1830 … The ease with which you delved into my views on geometry gives me real joy, given that so few have an open mind for such. My innermost conviction is that the study of space is a priori completely different than the study of magnitudes; our knowledge of the former (space) is missing that complete conviction of necessity (thus of absolute truth) that is characteristic of the latter; we must in humility admit that if number is merely a product of our mind

[@snarzetax]

"Alright, I'm going to have to answer this phone." I felt that. 😆

[@martijn130370]

Can't wait for this. Thx Brian for the stuff you have shared during the years. Amazing how many implications there are for all basic ingredients of physics when relativity is set in motion.. .time, space, and now mass.

[@jamestrexler6329]

"Ah, it stopped ringing, thank god!" - me about my phone regardless of the situation lol In other news, might I suggest Planck's Law of Black Body Radiation?

[@hardlyconfused3541]

Per Einstein: “It is not good to introduce the concept of the mass M = m/(1 v2/c2)1/2 of a body for which no clear definition can be given. It is better to introduce no other mass than the ‘rest mass’ m. Instead of introducing M, it is better to mention the expression for the momentum and energy of a body in motion.

[@hardlyconfused3541]

Disagree. This is what I read from Wikipedia: In Einstein's first 1905 paper on E = mc2, he treated m as what would now be called the rest mass, and it has been noted that in his later years he did not like the idea of "relativistic mass". I know Wikipedia may not be 100% accurate, but please correct me if the references are not correct.

[@kormorany94]

In my post above you will find the answer

[@robhappier]

Hi Dr. Brian Greene PhD! You forgot to mention that this relative mass, only applies to the observable physical universe. Examples where this relative mass wouldn't apply is inside black holes, at the edge of the universe where the expansion rate of space-time is unmeasurable, quantum vacuum energy state (quantum gravity), and inside the vortices on the surface of the Sun (Sun spots).

[@junisyounice4431]

Thank You for the uploads. I know it doesn't get the funding, or relate to your stringy concepts. Is there anything you can share about loop quantum gravity. Lately it doesn't get the attention it deserves. Keep in mind, this comes from someone, who's strength doesn't lie in mathematics

[@thatemeraldphotographer6003]

Loving this, thanks Brian and WSF!

[@jsbllrt]

Brian, this classes are so amazing! Thank you very much!! Cheers from Buenos Aires!

[@gioivanmijares7787]

After how many videos about mass, finally I understand it now Thank You!!!

[@kdkittehmama9490]

Some questions for a Q&A: 1. Why is c 3x10^8 m/s and not some other value? Not as in a maths derivation, but physically why does it have that particular value? 2. Why are the laws of physics the way they are? Why, for example, does F=ma, or why must matter and energy be conserved? How did these happen? 3. What happens to matter when it falls into a black hole? Where does it go? I assume the black hole gets larger, but how does that physically happen? Thank you!

[@troop4266]

Answer to part 1: The value of c depends on the units used, miles, kilometers , seconds.

[@seamusandpat]

Thanks for this wonderful series. I am enjoying it so much.

[@atridatta9651]

I am a eleventh grade student and I have a keen interest in relativity and particle physics. I do apologize to you sir if I am wrong, if so I would be thankful if you correct me.... E=mc^2 means that E energy is liberated when mass of an object changes by m when it moves with the speed of light c. So when v approaches c , mass tends to infinity(by m=m0/sq root(1-v^2/c^2)). Thus change in mass tends to infinity. So energy liberated will also be infinite!! How is that possible..... Furthermore, in E=mc^2 mass interchanges to energy. So mass of the body must decrease. But when v approaches c, we see relativistic mass is increasing ( mass tends to infinity) by m=m0/sq root(1-v^2/c^2) ....... I am really fascinated by this series and I would like it to continue for eternity....!!! Thank you Prof. Brian Greene.

[@rockinrobin9093]

Could you please do a video on the Heisenberg uncertainty principle?

[@paai74]

Thanks for reaching out to your followers dr green, really cool. I hope you get to the q&a because it would be great to have a chance to get a question in. Wkr rob

[@engnr]

Since we are still wandering around the E=mc^2, could You please, drop in a word about the energy-momentum relation, and how Paul Dirac (this Guy deserves a separate episode on his own..) extended Einstein's approach to include the motion energy? Great series, Professor!

[@aryanbhatt5835]

Equation Request: Hello Professor Greene, I'd love to hear about the wave equation. Thanks for this series!

[@rajgsb]

Hi Brian! Since you introduced the Taylor expansion here for Gamma, could you please do one episode on how that conversion happens from Gamma to the Taylor series? I can do this for my son but he would prefer to hear it from you! Thanks a lot. And please do keep going - I saw you at Fermilab in the early 2000s after you wrote Elegant Universe, and excited to see you do these now at WSF!

[@sethconnor1018]

Reminded me of my dad in this one! good vibes

[@80sLuv]

I have been watching your videos/talks since 2011. Your show on Spacetime, QM, Cosmology, String Theory are just awesome. Are you coming to University of Maryland at College park in future to give a lecture?

[@ibite100]

Thanks for these videos, very well explained, could explain afterward to my daughter who is 9 and she did not get excited by but understood and accepted the consequemces of the relativistic effects and was able to explain it back afterward. Good enough for me.

[@alexanderkrizel6187]

So, the long explanation is absolutely awesome, but a strictly mathematical explanation would be the if V=C, then 1-(V^2/C^2) would be 1-1 or 0. Since it's in the denominator, you can't divide by zero, so V cannot equal C (it can be smaller, or it can be larger????).

[@ffggddss]

"Relativistic mass" is a broken concept, because it works only for the special relativistic (SR) formula for momentum, p[rel]. When learning relativity, it is a mental crutch that attempts to preserve the Newtonian form of momentum by making mass depend on velocity. In fact, it isn't that the mass is changing; it is that the functional dependence of momentum on velocity, differs from the Newtonian p = mv; namely, p[rel] = mv/√(1-[v/c]²) = m(γv). And it is this change in the formula for momentum that makes attaining v=c impossible for any body with non-zero mass. The culprit is still that factor, "γ," but it is properly attached to the "v," not to the "m." That this is so, can be seen by trying to plug this "relativistic mass" into the Newtonian formula for kinetic energy, KE = ½mv². It gives the wrong result. The actual formula is KE[rel] = (γ - 1)mc² = (1/√(1-[v/c]²) - 1)mc² ≠ ½γmv². (Dr. Greene's derivation of the Newtonian KE from E = mc² is exactly right, however.) "Mass of a body" is a property of the body itself, not of its state of motion - or, in fact, of the state of motion of some arbitrary observer! Because it is a central principle of SR that physics "looks" the same in any inertial frame of reference. Two observers in uniform relative motion to one another should assign the same value to the mass of a body. Fred PS. See the excellent, less technical explanation of this by Dr. Don Lincoln on the Fermilab channel.

[@rajbhatta5595]

E2=(mc2)2+(pc)2. What does this equation mean? Please make a video on it.

[@rajbhatta5595]

@@ananyaraghuvanshi8699 As far as I know mc2 is the term that can be used for objects at rest(so not for light), and pc2 can be used for those in motion : for photons. Correct me if I'm wrong.

[@rajbhatta5595]

@@ananyaraghuvanshi8699 I am not talking about cases, but as a whole, what does the equation E2=(mc2)2+(pc)2 mean?

[@abdullahtareq8841]

Thank you for your time🙏Giant Scientist 👍👍

[@musicoscope]

Excellent! look forward for the next episodes... bravo

[@SerDunk]

Hehe love the home phone ringing. Think we all in quarantine can relate

[@raeddiab5571]

At 7:33.... why is the thrust speed is decreased by a factor of gamma?

[@rushi1306]

Sir always wondered why the mass of the electron don't get huge in the particle accelerator ? And really appreciate you for giving your precious time.

[@maulikparekh776]

The concept of relativistic mass isn't a real phenomenon unlike time dilation and other consequences of relativity. It is a mathematical construct. As he said in the video, it's a concept that can help people get an intuitive understanding of why particles with mass can't reach the speed c. In Newtonian mechanics we write momentum as 'p=mv' but with relativistic corrections to the equation, we get the equation as 'p=mv/√(1-v²/c²)'. Now just to keep the Newtonian form of the equation intact (and also the reason mentioned above) we group the 'm/√(1-v²/c²)' together and call it 'relativistic mass M' so that we can now once again have the 'p=Mv' form of the equation. Many people argue against doing this because with its uses it also brings in a lot of confusion especially for people who are just starting to learn the concepts.

[@maulikparekh776]

As for the electron (or more likely to be used proton) in a particle accelerator, the force required to get it to speeds closer to c does increase. The energies that the LHC is capable to produce now (about 6.5 TeV for each proton) can get them to a speed that is about 3m/s slower than c.

[@wayneyadams]

If you notice, he keeps using the term heft when talking about mass. The one thing he did not make clear is that the amount of matter does not change, in other words, it does gain matter and thus increase its gravitational force. That is a point that confuses people because Physicists decided to use the word mass when they really meant inertia (or as he says, "heft").

[@AditiSingh-en7fr]

Hello Professor Greene Love your series. Could u do a series on the millennium problems??

[@aremijfaye5160]

What 's wrong with this: E=gamma*m*c^2 With a bit of manipulation we can get E^2 -v^2*E^2 /c^2=m^2 c^4 When v increases, the left hand side term decreases, which means the right hand side (m^2c^4) is decreasing. Which simply means the rest mass decreases. Does it mean an increase in velocity implies a decrease in rest mass?

[@mrsvspin]

oh my goodness... wonderful... want... new focus ...to get it... thank you so much

[@Petrov3434]

This was wonderful !! Thank you

[@louisegch9710]

amazing brian thankyou

[@tjk3022]

thank you for uploading this valuable lecture in this hard situation~ everybody Cheer up~

[@sibiramm6107]

So deep explanation...❤️❤️❤️

[@vinuraj8832]

Hi sir I have a doubt By this equation if we are travelling with velocity v our mass increases but car, bike travells everyday thay also have thier mass but how thier mass dosnt increase ?????

[@akosbakonyi5749]

Thanks, great episode! How does the potential energy appear in e=mc2? Does the relativistic mass depend on the gravitational field?

[@frede1905]

That is a very good question, and something that I also asked myself. I might be wrong, but the conclusion that I got was that the mass of an object doesn't depend on the gravitational field/potential energy. Therefore, your mass won't change even though you change your distance to the center of the earth (the PE changes). However, the mass of the gravitating system as a whole will change. This is the reason why for instance the mass of a hydrogen atom is slightly less (PE is negative) than the sum of the masses of the electron and the proton.

[@omsingharjit]

You are going great work during pandemic . Pro

[@si_monster7365]

Where can I start learning a lot of math? And I’m not talking about only some beginner course. I’d like to start from the beginning but become really good at it in some years. Any advice would help! I have some mathematical knowledge from high school.

[@siddharthchavan910]

Woohoo having fun!!! Boltzmann equation 🥳🥳

[@crocaduck]

Thanks for the daily equation series! I have a related comment regarding relativistic mass. When I read Susskind's book, Black Hole Wars, I started thinking that there might be a nonequivalence between gravitational mass and inertial mass when comparing massive objects such as stars. For example, if we take an eight solar mass star, it will evolve and eventually undergo a supernova explosion resulting in a neutron star I'm guessing. But if we take a one solar mass star and accelerate it to .9928 the speed of light (which increases its inertial mass to about eight times), it will continue to evolve normally and eventually becomes a white dwarf. Even though the two stars' masses are the 'same,' the outcomes and evolution of them are quite different. So it seems that the equivalence between inertial mass and gravitational mass are not quite the same. Is this correct or is something missing? Ciao

[@martijn130370]

Super video, thx again. Curious what tomorrow will bring.

[@wayneyadams]

16:20 Since the Taylor expansion is used for low speeds, i.e., small values of v, the effects of the second, third, and so on terms is negligible. As Klaatu said to Dr. Barnhard in "The Day the Earth Stood Still." BARNHARDT: Yes -- that will reproduce the first- order terms. But what about the effect of the other terms? KLAATU: Almost negligible... With variation of parameters, this is the answer. BARNHARDT: How can you be so sure? Have you tested this theory? KLAATU: I find it works well enough to get me from one planet to another.

[@Earth4Mars]

Do you think that we subconsciously take advantage of this time dilation and perform better by the slow input of events I perceive from a moving object?

[@rogerman65]

Einstein, or someone, figured out an example with two lightclocks with a lightbeam reflecting perpetually between mirrors at the tops and the bottoms of two individual boxes and one of them was moving and you are sitting on it. Albeit the box can only travel up to a certain speed still below lightspeed, thus light can always intercept the mirrors in the box from within at the speed of light but with redshifting. The maximum speed of an object is apparently approximately three quarters of the speed of light. The distance the light is perceived to travel may vary depending on the observers motion and viewpoint, but the speed of light is always a constant in vacuum as confirmed in numerous experiments. I contend that when light reflects off an object it gets redshifted, i.e. its energy level is fading for each reflection. It might thus be correct to imagine that in Einstein’s particular example a lightbeam inside the box gets redshifted and scattered bit by bit for each reflection. It might be that the box riding gentleman (you) doesn’t perceive the light beam as if it was slowing down inside the fast moving box. It might be that he is only experiencing an increasing redshift of the lightbeam, up to a certain point on his course when what’s left of the lightbeam dissolves. Sorry Einstein, but you have no experimental evidence to support your intriguing example. Time perception though is another matter altogether, just not for measuring the speed of light at any other speed than the speed of light.

[@hinamiemad6981]

Very nice explanation professor. Can you explain how the concept of blackholes came into Einstein's mind?

[@physicsorbit8373]

Greetings Brian Greene. It has been more than a year i have been trying to get a grasp of the concept of the sum 1+2+3+...= -1/12. ( Ramanujan's Sum). Also i have heard that this series is a fundamental theorem in STRING THEORY ,so i feel its the best if i ask you ! I hope you answer me !

[@DANGJOS]

I'm remembering this stuff from classes. Been awhile

[@ryguy9664]

Is there anyway you can elaborate more on the Higgs field decaying and quantum tunneling described in chapter 10 of “Until the end of time?”

[@sarthakbose722]

Brian is love♥️😊

[@rogerman65]

There is much more I have to say about things. I cannot explain Quantum entanglement, but I know where to start to clew in on the problem.

[@santabanter]

BrIan Greene for President!

[@ohp9220]

great format!

[@santhoshv6233]

@Brian Green Does rest mass change with temperatures???

[@istvanszennai5209]

which app are you using to draw on the iPad?

[@Valdagast]

I thought the complete equation was E^2=m*c^4+p^2*c^2

[@mahadlodhi]

That is called "the relativistic energy-momentum relation", if im not mistaken. First derived my paul dirac. What makes it stand out from (mc^2*gamma factor) is that it relates the relativistic energy of a particle directly with its momentum particle involving the velocity of the particle. Both eqs are essentially equivalent. And as far as i know the momentum one is derived from (mc2 times gamma factor)

[@Taqu3]

Yes, but the mass term in "E^2=m0*c^4+p^2*c^2" is the rest mass. You can rewrite E^2=m0*c^4+p^2*c^2" as E^2=m^2 c^4 where m is the relativistic mass.

[@mahadlodhi]

@@Taqu3 indeed

[@mahadlodhi]

@@Taqu3 how would you get the relativistic mass though in the end when the momentum would be zero meaning the object is at rest relative to the reference body thus "m" being the rest mass?

[@benno365]

Don't forget to square the mass! The correct formula is E² = (m0)²·c⁴+p²·c². When at rest (p=0), you then get back E=(m0)·c², by taking the square root. This form was known long before Dirac (I would guess already in the 1905-paper), but the formula was used in attempts to make quantum mechanics consistent with special relativity. In that context it is known as the Klein-Gordon equation. Cheers, Martin

[@ethancolbert4070]

How would the equations shared towards the end of this video relate to E^2 = (mc^2)^2 + (pc)^2 ? I know very little about this equation (or any relativistic equations) and I'm wondering how it fits into the story.

[@SimonTiger]

E^2 = (mc^2)^2 + (pc)^2

[@Mamosta.Amanj_physics]

Great teacher be continued please

[@tarunparia8981]

Make a video explaining fourier series.

[@amreshyadav2758]

respected sir, please make an episode on bells enequilty. regarding EPR paradox. thank you.

[@kain1638]

greetings from Italy, we love you!

[@atridatta9651]

Sir I would like to have your views about the heisenburg uncertainty principle I request World Science festival to upload it soon.......

[@orelfrank9567]

wouldn't you get a different result if you used the kinetic energy instead of momentum because the speed would have been squared?

[@vanzilar]

I love it. Yaay yaay yaay.. review time!

[@Scynthius137]

How does the uncertainty principle interact with the speed of light. Can you get going fast enough so you don't know if you are exceeding the speed of light?

[@Martvandelay]

I love this!

[@nadersalehi191]

Consider a long bridge which can marginally tolerate the weight of a car when it is parked on it. If this car has to go over this bridge with relativistic speed which increases its mass/weight above what the bridge can hold, what would happen? Will the bridge collapse (pedestrian view) or remain intact (driver view)?

[@travelingchris86]

Man I ove that these shows are on at this time, thak you! I have a question, is there any link between e = mc squared and e = hn? does mass also equal frequency? This is probably a stupid question if there is such a thing, but hey,,, anyway thanks Brian!

[@dankuchar6821]

You are looking at two equations that are over simplified. E is not just mc squared since that only applies to objects that are stationary and have mass. The full equation includes additional terms. Also E=mc^2 is the low-momentum approximation, the full equation is E^2 = m^2 c^4 + p^2 c^2 where p is the relativistic momentum. Using the full equation, you can then compare to hn.

[@patriciolutteral2334]

What happens if the object/particule in question has no mass? A foton, for example.

[@kellymantei7465]

The speed of light is a constant in our spacetime gravity well.

[@iMushroomify]

Einstein always talked about persepctive, would it not be that from the perspective of the viewer that mass approching the speed of light would appear to gain in mass, but from the subjects perspective there would be no change?

[@pandabearguy1]

Would love to see something on the schroedinger equation, and interpretation of the paradoxical results and implications of it. Is (the absurd) schroedingers cat analogy really a message that quantum mechanics is not quite right etc.

[@carlosovi1]

First of all thank you for doing this dis videos, really enjoy them specially in this days, it gets my mind thinking in something else besides the pandemic. A dough come to me while I was watching these video and that is: does the photon have mas? And if it has, how does it overcome the infinite force it would need to get to the speed of light? Again thank for shearing your knowledge, looking forward to see your next videos

[@maulikparekh776]

No, a photon does not have mass (so its m.= 0) and hence it's possible for light to move only with the speed c (in vacuum). Any particle that has m.= 0 will always move at the speed c (in vacuum).

[@rogerman65]

@@maulikparekh776 Correction, a photon does not have REST mass.

[@maulikparekh776]

@@rogerman65 It does have 0 rest mass. We can't experimentally check that because a photon is never at 'rest', it always moves at the speed c. But, mathematically the equation is 'p=vm./√(1-v²/c²)' which can also be written as 'p√(1-v²/c²)=vm.'. Now when you put v=c in the equation, you get LHS = 0. Hence, the RHS must also be 0 for the equation to be valid, which is only possible when 'm.=0' where 'm.' is the rest mass. The same reasoning is true if we use the equation 'E=c²m./√(1-v²/c²)'. The most general form of the mass energy equation to include photons along with everything else is given as ' E²=(m.c²)²+(pc)² ' There's also QFT where what we call rest mass is a result of interaction with the Higgs field, and photons and gluons do not interact with the Higgs field and hence have no mass. But I haven't studied the theory in detail yet and only have knowledge about it from KZbin channels like this, so I am not sure about the mathematical details for that. PS: sorry I read your comment as "a photon does not have 'zero' rest mass. " Anyway, I was mentioning rest mass when I said mass in my 1st comment. That's why I mentioned m.=0 in the bracket.

[@ayushdubey295]

Please do some complex equations as well...

[@xspotbox4400]

So it's impossible to change speed of light, but what about mass, could we accelerate an object almost to a finite speed, than detach large chunk of it and give additional push to the rest of mass?

[@wwaqashussain]

Thankyou very much , Pakistan

[@ANUJYADAV-rm7em]

Respected sir please make videos on quantum physics so that student like myself could easily understand the true nature of reality. Thank you sir.

[@lattoufe]

Any updates on Q&A?

[@taylorfredrickson7750]

A bit confused. In the second scenario the velocity of the lance of evil Brian is slower than good Brian, this is the only difference. So why is good Brian's Mrel the same and why doesn't he win?

[@YTAliasJoeCool]

The velocity of anything is different, when measured from different spots, e.g. from the earth, from the sun (adding earth's speed round the sun), from the center of the galaxy (adding the sun's speen round the galaxy)... This leads to the relativistic mass and also the energy being different also for different "observers" ?

[@rogerman65]

This is how crazy I am; 1. I contend that mass for an object with momentum is not absolute, especially at extremely high speed. Check! 2. I contend that there are absolute motion for mass within a speed scale up to the maximum speed of 3/4 of the speed of light. Check! 3. I contend to that it is the speed as such, in which an object travels, that determines how slowly or rapidly it ages in relation to other objects. It is not because objects move away from each other or move towards each other that makes them age differently, but all objects are always in relation. Check! 4. I centend that time dilation for light is only a mathematical somersault except in the sense that a frequency may vary depending on whether the emitting object is approaching, or distancing from, another object. An emitting object cannot travel at the speed of light and therefore there is no time dilation for emitted light, there are only frequency variations. Check!