How can a photon have momentum? 

And of course make it accessible for those of us who struggle with the math. Math doesn't intimidate me, REQUIRING math intimidates me.

AMEN, g! Agreed!

Math is good for calculating, but I hate how math is misused by many to show how physics works; It gives people the illusion of understanding. Same way people nowadays just google whatever they don't know and end up feeling like they know more than they actually do. "Everyone" knows that E = mc². But how many know WHY? That is what's important to me at least; understanding how the universe works. Question your unconscious assumptions.

@Science Revolution because the flame is transparent, and also because the laser used to move drones does it with heat transfer, not momentum.

I was just gonna comment that

According to Wikipedia it's actually mc^2/sqrt(1-v^2/c^2). The approximations given are a Taylor series for the inverse square root

But have you read Landau and Lifshitz Theoretical Physics?!

me too

@pyropulse Yes I learned that in undergrad.

@@chair547 that equation is total energy. Kinetic energy one is mc^2*(1/sqrt(1-v^2/c^2)-1)

So beautifully put!

A great example of Dunning Kruger in action too, especially the ironic certainty about arrogance and looking down on people.

@Science Revolution may be it had thermal convection

@Science Revolution one reply ok but replying on all comments? I'm reporting all of your replies.

@@esajpsasipes2822 spamming can be annoying but at least he'll get a few different replies.

@@alwaysdisputin9930 he is very likely a bot

@@esajpsasipes2822 It's a decent question. I think maybe the flame is made out of plasma & it's mostly empty so the laser does push some particles but only a few.

Dude... you're only 67. Why you think your time is almost up? a PhD in physics only takes 3-4 years... go get one.

Mass is an emergent characteristic of structures in our Universe; analogous to how life is an emergent characteristic of certain configurations of matter. What we refer to as (quantum) particles is a particular kind of fluctuation in a quantum field. Mass emerges as a measurable quantity associated with any structure that forms as a result of interactions between a collection of particles. Even though a single photon is massless, a collection of photons confined within an internally mirrored box adds mass to the box due to the (confinement of) photons. The mass of most quarks and leptons is due to the interactions of their underlying quantum fields with the Higgs field.

@@RockBrentwood I appreciate the detailed response! I was referring to the fact that he says mass is an illusion at 8:20 but thanks for your explanation as well :)

@@RockBrentwood Wow, I hadn't really thought about the math that way, but it's quite illuminating in relation to the ideas behind special relativity. Thank you.

@@RockBrentwood side note: 1. for a photon V is always slower than C (except for an imaginary vaccume) from an outside reference frame. 2. its m=m0/√(1-(v/C)²) NOT (1 + √(1-(v/c)²)) (m0 is the rest mass)

@@Patrik6920 isn't the rest mass of photons equal to zero?

Great point. I wish my instructors would have continued their studies by watching these videos. Then I may have been better informed from the get go.

@Science Revolution Buzz off Bozo

Your instructors probably didn't know in the first place. How can they teach what they don't already know themselves? And by the way, just because you watched a few videos on a subject, it doesn't mean you know anything about it really. In fact, you likely just know enough to make yourself think you know the topic when you really don't. In something like this, it's harmless. If the topic was auto repair, you could easily get yourself in a lot of expensive trouble.

@Science Revolution Dunno but that has absolutely nothing to do with my comment.

@@mugwump7049 yeah I'm wondering if it's a bot. They're putting the exact same reply under people's comments.

Literally, lol

You know how sometimes you wish you could rewatch a movie, reread a book, or go play a game like it was your first time? I kind of wish I rediscover the wonders of science again. For me to get these kinds of wow moments again, I need to really dig into the actual math of wave functions and stuff, and I'm honestly not at that level, either. I'm in this weird in-between.

@@kindlin Read up on biology. Evolution has all these predictions that boggled my mind when I first learned them, well after I finished taking school biology. It's a shame we don't teach it in school. Totally changed my outlook on the living world.

It was indeed very well explained.

@Science Revolution How would it move a flame? What does that even mean? You need to define your question properly before you can get a clear answer.

@@kindlin the crackpots are everywhere. Even though it's not 100% perfect, it's best if we take for granted what is consensus first. Very rarely do crackpots have reason. Crackpots don't contradict just this result, there's always a crackpot denying the most basic universally accepted ideas, and when they deny them it's always with a lot of non- sense, like, "hey, I am an uncomprehended genius, I am right while all you doofus are wrong."

i envy you.. i asked all grear channels my question but got no reply so far😔

Someone’s been lying to us? Who woulda thunk it.

@@kwnorton5834 It was funny when he said ThEY'Re LYiNg to YoU SheEPle but then he said we're made out of mass but science has never proven what we are. We could be singularities for all we know.

@@kwnorton5834 science isn't even close to say any absolute truth about the whole universe. But it's not claiming that it does either. It's the best thing we got though.

@Science Revolution what the utter fuck are you talking about...take your nonsense elsewhere

Speaking of total BS...

@Science Revolution I know photons can interact with particles such as electrons, but do photons interact with other photons? I'm genuinely curious, but I somehow doubt you're the right person to ask, given your comment..

@Science Revolution - Let me guess, next you're going to say there's this stuff called "luminiferous aether" that carries the light waves?

@@malachiwiens2455 they don't, at least not directly. There're higher-order mechanisms where they create another virtual particles which can then interact and return into photons, see en.wikipedia.org/wiki/Two-photon_physics

@Science Revolution First, change your handle, because THAT is the only BS around here. Second, stop trolling, because either you know better and are just trying to provoke people into arguments, or you DON'T know better and are too stupid to learn. In either case, shut up.

@Science Revolution What?

E=mc² is very often not clearly communicated. Sometimes people use the m to mean relativistic mass(ym), in which case the equation holds at any velocity below c. In that case one should write E0=m0c² with E0 and m0 being the "rest" energy and mass of an object. But since relativistic mass has fallen out of favor in modern physics the equation m is basically synonymous with m0 and mass is always rest mass. Then the clear way to write the equation would be E0=mc². But people just write E=mc² without specifying what they mean.

Agreed. I had to turn down my volume to comfortable listen to this video. Otherwise the content and presentation is great.

Because mass is concentrated and reconfigured energy and the change in state generates mass.

@Science Revolution Please provide a reference to this. Or start over with whatever you consider is knowledge.

@Science Revolution seriously are you a bot? You just have the same copy/pasted reply under people's comments.

@Science Revolution Because light things that move very fast can have tiny momentum and a crap ton of energy.

@@malachiwiens2455 I've seen that a few times recently, 'regular' comments posted more than once under different names. Science Revolution, tell us if you are human or not

@@alexrobomind yeah, but for EM waves, photons, the energy is directly proportional to their momentum, isn't it?

The story about that picture that I heard is that he was annoyed at always being photographed, so he decided to ruin the picture by sticking his tongue out. He was even more annoyed when the picture became so popular.

Underrated comment

Generally speaking, it’s special!

@Ratnasambhav Sahu relativistic shirt*

@Ratnasambhav Sahu idk just said something.

FLP is pretty much making videos about the feynman lectures at this point. If you'd like a deeper understanding about their topics you can read those.

Ah, the old conflict between quantum physicists who want to understand the fundamentals of the universe, and the other side whose motto is "shut up and calculate".

@Science Revolution Because ... that has nothing to do with it?

Yes, fundamentally mass is a tension- the tension of gluons pulled by quarks. Tension is a very important concept for the imagination, as GR is also the study of tension (although tension of dimensions and time). Indeed, physics is a model. Intuition is the tool to understand the underlying reality. Imagination is the key to intuition. (I enjoyed your post. You're clearly a philosopher in the original context- "lover of knowledge".)

@Science Revolution What is a flame? A flame is not a "thing", but individual atoms at high velocity (plus light). "Lasers can't move a flame"? Well, that's not correct. Lasers are how we trap individual atoms, and move them around. All we need do is match the frequency of laser light to the absorption frequency of the atom. When those frequencies match, the atom slows it's motion toward the laser. Add lasers from multiple directions, and you have an "atom trap". Magnets then help contain that atom from hitting the container when it loses momentum. You want to stop a "flame"? Well, that's a motion stream of many individual atoms. Can you stop a river by throwing a tennis ball into it? Nope. So let's do apples to apples: Can you lower the temperature of specific atoms in that stream with a laser? You bet 'cha. Just find the absorption frequency, point 'n shoot- voila. Yes, lasers can "move" a flame by transferring their momentum. You just need the right frequency of laser light.

@@onebylandtwoifbysearunifby5475 No, I am no philosopher, however it can be fun. I would describe myself as a self educated budding fundamental physicist by necessity (there is a bigger story here). The reason that my comments seem philosophical is because I cannot discuss what I know publicly. My comments are designed to capture Don's attention as I know that he has a security clearance and I would know with whom I am talking to. My knowledge has the potential to transform human society with exponential speed, however it cannot fall into the wrong hands due to potential of misuse. I have a problem of not being able to pass this information to liberal democracies, including my own country, because I am thwarted by a 'party' who has already achieved this and is in manipulative control of governments and its agencies. Hence, my condition of passing the information is through intelligence agencies with at least six individuals face to face and repeated for at least three consecutive days. Some authority needs to be ceded to me in case of unexpected circumstances. Verification of credentials is essential. Warning: all means of electromagnetic communication is manipulated or prevented. Problem for me: the more I warn you about the said third 'party' the more you consider me a conspiracy theorist, and the less I tell you about the third 'party' the easier you will be manipulated and the communication effort derailed. My personal information: Jerry Mlinarevic 9 Dryden Court Bundoora Victoria 3083 Australia Mob. +61 403 447 155 VoIP. +61 3 9466 8023 email. jerry.mlinarevic777@gmail.com Remember that just as I am being thwarted that you too will be manipulated to ensure that your effort to communicate with me or an attempt to inform others about this will be interfered with. This has been painstakingly typed on a TV set top box which is more secure than computers or phones.

If you want to watch math vids go watch redpenbluepen He's pretty good and you can work on the problems with him.

No... Math is not the language of the cosmos. It is our language. Do not think for a second that the universe "communicates" or "orchestrates" through math. The universe just is what it is, and WE use math to describe what we see. And it's flawed too. Just take a common example of pi. We will never be able to calculate pi to perfection. We can get it "good enough" for our engineers, but we'll never be able to describe it perfectly. Our numbers, our math, falls short and the universe clearly hasn't ordained itself such.

Kinetic energy is the sum of KE's of all molecules in a gas enclosed in a container. This ultimately results in pressure of gas in the container. P= 1/3( Rho).(c squared). Hope it is now clear

@@krishnaraolingam4812 Bazinga

Same here..... at fundamental level if Atoms are made up of quarks then why they derive most of their mass due to some kind of elusive binding energy.... just beyond my capacity to grasp

@@rajkumardhakad8773 Maybe it's like trying to comprehend infinity, we're not really wired up to truly understand it ....

Idk, I have been watching these videos for years and things make a lot of sense now. Still mind blowing but more in an “of course” way. What helped me to get into the right mindset was the video about quantum field theory, always by dr. Lincoln. When you grasp and keep in the back of your mind the idea that what we perceive as reality at the fundamental level is just a cobweb of buzzing energy fields everything else, not only is not so surprising, but gets easier to understand.

Of course speed is important niels borh was waiting for als traffic Light and investeren the atom bomb danish he was yunis

Yes, I was thinking this would be easy to explain. Just use E=MC^2 which says that mass and energy are equivalent. Solve the equation for mass and you get M=E/(C^2). So a photon has energy and is moving at the speed of light. If you know the energy of the photon then you can calculate the mass equivalency and proceed to use this value to calculate momentum.

@@perrygershin3946 yeah, so I guess that the momentum of a photon is dependent of it's energy instead of it's mass, since it doesn't have.

Or you can just take E=pc which gives you the momentum of the photon rather directly.

@@tarmairon431 i don't understand where this comes from. Can u explain pls?

@@dinaangelia5145 It was in the video, but I can repeat it if you want. I assume you've heard E= mc^2 ? That's a simplified version for particles at rest. The complete equation is E^2= (mc^2)^2+(pc)^2 Since photons don't have mass the equation for them is E^2=(0c^2)^2+(pc)^2 The first half is all equal to 0 which leaves E^2=(pc)^2 That also can be written as E=pc Sidenote: Mathematically you would also get E=-pc as a solution, but that doesn't make any sense in physics so it can be discarded.

You can also get the momentum from the de broigle relation p=h/wavelength.

I don’t understand how this is an explanation: If you put p=E/c in the first equation you end up with E^2 = E^2. What am I missing in the thought process ?

I think this is how our alien friends are getting around

@@Wolfman4Jack There aren't two equations, just one equation rearranged. By doing that substitution, all you did was rearrange it in a different way. The fact that you got E^2 = E^2, which is definitely a true statement, just shows that the arrangement he gave you is consistent with the original equation. It doesn't "prove" anything, its just writing it in different ways that may or may not be easier to understand.

The problem with you suggestion is that not all energy is mass (all mass is energy) and keep the definition of mass as is (m^2=E^2-p^2). Not sure why you think the hills are nothing.

@@kylelochlann5053 Thank you very much indeed. About the hills, .. I first thought about Rutherford, Atoms are nearly empty. Through this Video I thought that I learned that even the nucleus is not entirely a true mass, but derives its mass from Quarks on a somewhat confined race track. Kind regards, Carl

@@carlbrenninkmeijer8925 When we look into the nucleus (deep inelastic scattering) we see that quarks are point particles no different than electrons so the fundamental particles do not occupy any volume at all. However, these particles do interact and it's in the interaction is what we mean by existing and "being there".

I may guess there is a mass of the earth that is including us and everything else.

@@vitr1916 True, you are right, but I was suddenly realising that matter is empty, the atom is empty having only a tiny nucleus and now I learned that even the nucleus is almost empty.....

the photoelectric effect yes

@@orgaynigga8425 yeah that is included but i think for high energy photons like uv and above. radio photons cant knock electrons but merely vibrate the molecules causing heating effect

Thats not a loop. Or m=p/v is also a loop. You can solve the equation for p if you know E (for example from E=hf) or for E if you know p, for example by measuring it. The same goes for the Newtonian equation. We just usually expect to know m. So by that token we should expect to know E.

@@narfwhals7843 I still don't get that. In the classical sense that wouldn't solve for m=0 because you can't divide by 0. Math was never my strong point but I still can't get that m out of the equation. ( I know, physics isn't wrong, my understanding of it is wrong but I hoped I would understand after this video and I'm still stuck in the same place)

@@rienkhoek4169 If you know the E for E=pc (which only specifically applies to massless particles) you can solve for p=E/c . There is no mass there anywhere. You can also get p from another relation, p=h/λ where h is plancks constant and lambda is the wavelength of the photon. There is also no mass in there. Momentum is the ability to exert a force. And that does not require mass. The issue is that the special case p=mv is so ingrained in our intuition that our brains often refuse to let go of it. But our intuition is built on our extremely limited experience in the everyday world.

@@narfwhals7843 thanks. Appreciate it. According to Wikipedia p is in kg*m/s. Or is this also limited to non-zero mass?

@@rienkhoek4169 No, but the units don't matter. Units are essentially arbitrary historical artifacts. In SI units momentum is given in terms of kg*m/s and the unit for energy, joule, is given as kg*m²/² . Both of them are "derived" units from the base units we chose. We could also chose a different system of units in which they are given as different basis or are base units themselves. We can chose units where velocity is a base unit and the speed of light is set to 1 to simplify our equations. en.wikipedia.org/wiki/Planck_units

Electron is not accelerated by the photon, but it goes to a higher energy state. (Its simplified representation in school is that it goes to a higher orbit).

Oh, I heard from some where that accelerating charges make light and vice versa

Nothing happens instantaneously. If a free electron (one not confined in an atom) absorbs a photon it will accelerate over a time period that is proportional to the energy of the photon. The higher the energy, the quicker the change of momentum (acceleration). For example, an electron at rest absorbing a photon of visible light with a wavelength of around 600 nanometres (red light) would accelerate in the time the photon would take to cross that distance which is around 10^-15 seconds, which is also the inverse of the frequency of that photon. An electron moving to another energy level in an atom will also take some time. What I've written above is a classical explanation (and so a rough estimate) but they are quantum objects and so the real answer is more complicated, but the general rule is that nothing can change faster than light takes to travel across the distance of the interaction.

@@tonywells6990 isn't there a whole conundrum about light itself being instantaneous in the absence of other mass? It's not proven, because we can never examine it, since everything we are, and could create would have mass. So we can't create a device to measure the speed of light in the absence of it. But it is the natural outcome of taking the idea of relativity into account. Since mass causes gravity, and gravity distorts time. Greater gravity= greater time distortion. Then the inverse is also true. Less gravity = less time distortion. And in the complete absence of gravity time doesn't exist, and everything happens all at once. But the only thing that can exist in the absence of gravity is light due to its lack of any mass, and therefor all light travel occurs instantly under these conditions.

@@anthonypolonkay2681 Light still travels at the speed of light in a flat region of spacetime, and in our universe gravity exists everywhere.

Next step: There are no particles. It's just a wave, until it hits something.

@@Mp57navy not a wave. Physics deals with fields. Particles are perturbations in the field. Collisions are incidental I accept your apology

@@PetraKann that's.. a stupid distinction... That's like saying sound isn't a wave, it's perturbation in the atmosphere.

Groan.

@@a0cdhd Yeah, I know, they are real groaners. LOL

ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-oupevm2Q7yU.html

Wowsers! Go search for those never ending pockets of Discovery within this universe, that our minds couldn't even begin to fathom to be real.... Until we discover it. Then we know it's real...🙏🌿

@Science Revolution Explain how light gets to earth from the sun....I showed light particles in my experiments ...On my YT channel watch this video...it explains the Quantum Foam Don talks about and why we are overheating. "Cataclysmic pole shift hypothesis seems Likely Soon"

That's awesome. In a similar fashion, I learned as a programmer that the compiler is always right. When it seems as though it's wrong, it's because you didn't tell it to do what you thought you told it to do, or you assumed a variable would have a value that turns out to be missing at run time because you missed an edge case, etc. The compiler didn't make the mistake; the programmer did.

@Science Revolution Anyone who looks at your channel can see how full of misinformation you are. Please go away.

I don't understand the question.

Up quarks and Down quarks are pretty stable, but we don't find individual quarks because they bind together by the strong nuclear force. A proton is 3 quarks (two Up quarks and one Down quark) bound together. What kind of hydrogen bond are you asking about?

First of all if the speed of electron is more than that of a proton then it's relative mass should also be larger than the proton then why don't proton revolves around the electron ...

@@brothermine2292 If force between two charge particles is independent of mass that is given by F=kq1q2 divided by the square of distance Then electron should also exert same force on proton as proton exerts on electron in Hydrogen atom where there is only one Proton and and one electron Why don't protons revolve around the electron in an Hydrogen atom ....

@@brothermine2292 If magnetism and electricity are two different sides of a coin then why positive and negative charges exists independently more accurately electric charge exists happily but in case of magnetism why don't monopoles exist or why don't South pole and North pole exist independently or why Magnetic Charges don't exist ... Why Universe breaks symmetry of electromagnetic force .... If according to special relativity magnetism and electricity are the same thing from different frame of references then why don't magnetic charge or monopoles exist ... Or in other words if Magnetism is Electricity from a different frame of reference then why don't.... If they both coexist as electromagnetic force then why don't ....

We live in a holographic universe and the UFO’s we see are the high tech kids on the block using photon energy and antigravity to go inter dimensional

an honest answer leads to real learning.

"thanks for your illuminating explanations" I C what you did there.

p is _not_ equal to mv. That is a low velocity approximation. For massless particles you can either use p=E/c and find the energy from Planck's relation E=hf, or directly use p=h/wavelength.