Beyond Einstein: Physicists solve mystery surrounding photon momentum

Beyond Einstein: Mystery surrounding photon momentum solved
A photo of the COLTRIMS reaction microscope built by Alexander Hartung as part of his doctoral research in the experiment hall of the Faculty of Physics. Credit: Alexander Hartung

Albert Einstein received the Nobel Prize for explaining the photoelectric effect: in its most intuitive form, a single atom is irradiated with light. According to Einstein, light consists of particles (photons) that transfer only quantised energy to the electron of the atom. If the photon's energy is sufficient, it knocks the electrons out of the atom. But what happens to the photon's momentum in this process? Physicists at Goethe University are now able to answer this question. To do so, they developed and constructed a new spectrometer with previously unattainable resolution.

Doctoral student Alexander Hartung became a father twice during the construction of the apparatus. The device, which is three meters long and 2.5 meters high, contains approximately as many parts as an automobile. It sits in the experiment hall of the Physics building on Riedberg Campus, surrounded by an opaque, black tent inside which is an extremely high performing laser. Its photons collide with individual argon atoms in the apparatus, and thereby remove one electron from each of the atoms. The momentum of these electrons at the time of their appearance is measured with extreme precision in a long tube of the apparatus.

The device is a further development of the COLTRIMS (Collision Optical Laser Testing Reaction Interacting Momentum System) principle that was invented in Frankfurt and has meanwhile spread across the world: it consists of ionising individual , or breaking up molecules, and then precisely determining the momentum of the particles. However, the transfer of the photon momentum to electrons predicted by theoretic calculations is so tiny that it was previously not possible to measure it. And this is why Hartung built the "super COLTRIMS."

When numerous photons from a laser pulse bombard an argon atom, they ionise it. Breaking up the atom partially consumes the photon's energy. The remaining energy is transferred to the released electron. The question of which reaction partner (electron or atom nucleus) conserves the momentum of the photon has occupied physicists for over 30 years. "The simplest idea is this: as long as the electron is attached to the nucleus, the momentum is transferred to the heavier particle, i.e., the atom nucleus. As soon as it breaks free, the photon momentum is transferred to the electron," explains Hartung's supervisor, Professor Reinhard Dörner from the Institute for Nuclear Physics. This would be analogous to wind transferring its momentum to the sail of a boat. As long as the sail is firmly attached, the wind's momentum propels the boat forward. The instant the ropes tear, however, the wind's momentum is transferred to the sail alone.

However, the answer that Hartung discovered through his experiment is—as is typical for quantum mechanics—more surprising. The electron not only receives the expected momentum, but additionally one third of the momentum that actually should have gone to the atom nucleus. The sail of the boat therefore "knows" of the impending accident before the cords tear and steals a bit of the boat's momentum. To explain the result more precisely, Hartung uses the concept of light as an electro-magnetic wave: "We know that the electrons tunnel through a small energy barrier. In doing so, they are pulled away from the nucleus by the strong electric field of the laser, while the transfers this additional momentum to the electrons."

Hartung used a clever measuring setup for the experiment. To ensure that the small additional of the electron was not caused accidentally by an asymmetry in the apparatus, he had the laser pulse hit the gas from two sides: either from the right or the left, and then from both directions simultaneously, which was the biggest challenge for the measuring technique. This new method of precision measurement promises deeper understanding of the previously unexplored role of the magnetic components of laser light in atomic physics.


Explore further

Intriguing discovery provides new insights into photoelectric effect

More information: A. Hartung et al, Magnetic fields alter strong-field ionization, Nature Physics (2019). DOI: 10.1038/s41567-019-0653-y
Journal information: Nature Physics

Citation: Beyond Einstein: Physicists solve mystery surrounding photon momentum (2019, October 1) retrieved 20 October 2019 from https://phys.org/news/2019-10-einstein-physicists-mystery-photon-momentum.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Oct 01, 2019
Everybody knew the answer before the question was axed.

It's the Electric Universe®™

Oct 01, 2019
"When numerous photons from a laser pulse bombard an argon atom, they ionise it. Breaking up the atom partially consumes the photon's energy. The remaining energy is transferred to the released electron. The question of which reaction partner (electron or atom nucleus) conserves the momentum of the photon has occupied physicists for over 30 years."

Momentum is given by the equation, P = mv, P is the momentum of the particle, m is the mass of the particle, and v is the velocity of the particle, therefore a photon being massless has zero momentum.

"The electron not only receives the expected momentum, but additionally one third of the photon momentum that actually should have gone to the atom nucleus."

Doctoral student Alexander Hartung has not progressed far enough along in his study of nuclear physics to learn that a photon being massless has ZERO MOMENTUM, it has ONLY ENERGY. The energy of the photon is transferred to the atom & electron that causes the ionization, not momentum.

Oct 01, 2019
ER = EPR > EU

Oct 01, 2019
Doctoral student Alexander Hartung has not progressed far enough along in his study of nuclear physics to learn that a photon being massless has ZERO MOMENTUM, it has ONLY ENERGY. The energy of the photon is transferred to the atom & electron that causes the ionization, not momentum.


Wrong. It has zero rest mass.

Oct 01, 2019
...a photon being massless has ZERO MOMENTUM, it has ONLY ENERGY. The energy of the photon is transferred to the atom & electron that causes the ionization, not momentum.
When an incoming photon knocks an electron out of a metal (as per Einstein's photoelectric musing in days of yore), how does the electron know which direction to go, having only the photon's energy to inform it?

Oct 01, 2019
a photon being massless has ZERO MOMENTUM, it has ONLY ENERGY. Energy of the photon is transferred to the atom & electron that causes the ionization, not momentum.


When an incoming photon knocks an electron out of a metal (as per Einstein's photoelectric musing in days of yore), how does the electron know which direction to go, having only the photon's energy to inform it?


Something that is MASSLESS never "knocks" anything out of anything else, it imparts ENERGY causing instability within the particle to change orbital position within the electron shell structure creating the ionization Hartung speaks of: "When numerous photons from a laser bombard an argon atom, they ionise it."

He makes this correct statement: "Breaking up the atom partially consumes the photon's energy. The remaining energy is transferred to the released electron.", then negates it with this:The question of which reaction partner (electron or atom nucleus) conserves the momentum of the photon.

Oct 01, 2019
He makes this correct statement: "Breaking up the atom partially consumes the photon's energy. The remaining energy is transferred to the released electron.", then negates it with this:The question of which reaction partner (electron or atom nucleus) conserves the momentum of the photon.


Wrong. Photons have momentum.

Oct 01, 2019
He makes this correct statement: "Breaking up the atom partially consumes the photon's energy. The remaining energy is transferred to the released electron.", then negates it with this:"The question of which reaction partner (electron or atom nucleus) conserves the momentum of the photon."


Wrong. Photons have momentum.
......there is no basis for such a conclusion, either in reality or in math.

Momentum is given by the equation, P = mv, P is the momentum of the particle, m is the mass of the particle, and v is the velocity of the particle. In this equation, when P= 0 x v the answer is zero, you know, zero times anything is ALWAYS zero, or maybe you don't know that as is most likely the case?

Oct 01, 2019
ohh, my turn
the ubiquitous photon goes in any damn direction it pleases
though usually it prefers traveling with a queue of other photons
but, there's a;ways the outlier,
seeking it's own path with random abandon

especially when it's traveling with an irrational number

Oct 01, 2019
It's an interesting question.
Another I have is why does a photon reflect from a surface with the surfaces colour ?.
I'm betting it doesn't, the "reflection" is another photon that has spent enough time in the atomic trap to normalise it's colour spin.

I.E. The incoming photon is trapped and the reflected photon is ejected from the edge of the atomic trap.

There is no way a photon reflected at C will have enough time to transfer the colour quantum.

Oct 01, 2019
He makes this correct statement: "Breaking up the atom partially consumes the photon's energy. The remaining energy is transferred to the released electron.", then negates it with this:"The question of which reaction partner (electron or atom nucleus) conserves the momentum of the photon."


Wrong. Photons have momentum.
......there is no basis for such a conclusion, either in reality or in math.

Momentum is given by the equation, P = mv, P is the momentum of the particle, m is the mass of the particle, and v is the velocity of the particle. In this equation, when P= 0 x v the answer is zero, you know, zero times anything is ALWAYS zero, or maybe you don't know that as is most likely the case?


How many times do you need to be told to stay away from science? You are crap at it. Stick to mopping floors. See the answers here;

https://physics.s...momentum

Oct 01, 2019
Photons do exist and they have persisted for at least 13.77 billion years.
They don't express any gravity that we can measure.

The current thinking is photons are on the 1C^3 scale in the G space.
This thinking has lead to the redefinition of C because of the LHC and string theory observations.

Oct 01, 2019
He (Hartung) makes this correct statement: "Breaking up the atom partially consumes the photon's energy. The remaining energy is transferred to the released electron.", then negates it with this:"The question of which reaction partner (electron or atom nucleus) conserves the momentum of the photon." Hartung does not understand the photo-electric effect as is found in Einstein's paper on the subject for which paper is found at:

http://astro1.pan..._eng.pdf

Do a document word search for PHOTON MOMENTUM at the above site in the manner Hartung used it in the above article & you will come up empty.

Hartung is basically discussing Einstein's photo-electric effect for which he won a Nobel. In this paper by Einstein he knew better than to assign MOMENTUM to a massless EM Photon Wave, apparently Hartung hasn't gotten this far along in nuclear physics, I see others here in the chatroom have the same problem.

Oct 01, 2019
E² = p²c² + m²c⁴

More familiarly, for a particle at rest in your frame, E = mc². For photons, E = pc.

Of course, for photons, m is 0, and for rest particles, p is 0. But you'd have to be able to do math to see why.

Oct 01, 2019
I find it interesting. Ha, I like the bit '...Hartung used a clever measuring setup for the experiment. To ensure that the small additional momentum...' I think it's all clever stuff...but then being a layman I suppose I would. However, I do remember reading Q & A session a while back where the Japanese Lecturer he was using X-rays and Argon (the question was initially about the Work Function, which gases don't have in the P.E.)

Oct 01, 2019
E² = p²c² + m²c⁴

More familiarly, for a particle at rest in your frame, E = mc². For photons, E = pc.

Of course, for photons, m is 0, and for rest particles, p is 0. But you'd have to be able to do math to see why.
......it's wrong, Einstein never used it & explained why.

How about if you Copy & Paste a link directly from General or Special Relativity if you think otherwise? WikiPedia links by anonymous writers ABOUT Special or General Relativity are of limited value in the world of REAL Scientific endeavor, they are woefully inadequate suppositions for the ORIGINAL documents of writ.

Oct 01, 2019
a photon being massless has ZERO MOMENTUM, it has ONLY ENERGY. Energy of the photon is transferred to the atom & electron that causes the ionization, not momentum.
Let's reset this pinball machine, and forget about the argon for a second. The photon comes in a knocks an electron out of the metal. Which way does the electron go? It has to go in some direction. I'll give you the answer: for a very low energy (long wavelength) photon, it averages off to the sides (but can go forwards or even backwards. This is consistent with the electric field component, and consistent with a rather wishy-washy vector component of some sort, but what? As we increase the incoming photon's energy (keV), we get a sort of two-lobed fan (from a simple top-view) that is pointing forward and its average angular distribution, and the more energetic, the more forwardy-looking the fan. Why? Because of conservation of something maybe? Any guesses what?

Oct 01, 2019
At a more basic level, how can photons knock electrons out of atoms if the photons don't have momentum?

Duhhhh ummmm.

Oct 01, 2019
At a more basic level, how can photons knock electrons out of atoms if the photons don't have momentum?
Yes; the word 'knock' sort of loses a bit of its 'oomph' as it were.

Oct 01, 2019
This is the basic thing the photoelectric effect demonstrates. It's the beginning of the ongoing research into light-matter interactions. What this experiment shows is how the momentum is distributed after the photons interact with the electrons, and these sensitive measurements confirm expected conservation of momentum, and therefore confirm relativity.

Oct 01, 2019
Let's reset this pinball machine, and forget about the argon for a second.The photon comes in a knocks an electron out of the metal.
.....a photon can do no such thing, knocking, because it does not contain Kinetic Energy, only particles of MASS contain Kinetic Energy, a photon is Electro-Magnetic Energy, it is massless.

Electrons ABSORB Electro-magnetic energy thereby creating ionization of the atom as the newly absorbed photon excites electrons causing electrons to recoil & jump orbital position. An EM Photon Wave has no recoil effect such as electrons do when jumping orbital postions because they are massless.

If you believe you can make a working baseball bat out of a massless beam of light, then you're forever doomed to living in fantasy world of light sabres, you will never apply kinetic energy to any ball you try to hit with your laser bat, you will be an easy strike out.

Oct 01, 2019
What this experiment shows is how the momentum is distributed after the photons interact with the electrons,
......it does no such thing. This is too much like you trying to explain how a solar sail works.

Oct 01, 2019
Let's reset this pinball machine, and forget about the argon for a second.The photon comes in a knocks an electron out of the metal.
.....a photon can do no such thing, knocking, because it does not contain Kinetic Energy, only particles of MASS contain Kinetic Energy, a photon is Electro-Magnetic Energy, it is massless.
I get the impression that you have no idea what the CLASSIC photoelectric effect of over a century ago, that Einstein was the first to fully explain, actually is. Light, typically UV, comes in, and electrons are quite literally knocked flying out of the metal, typically cesium or something with some very loose electrons, like so many bowling pins.

It isn't about solar-cells here, or photocells. We're not talking about an electric-power device.

RNP
Oct 02, 2019
@Benni
Doctoral student Alexander Hartung has not progressed far enough along in his
study of nuclear physics to learn that a photon being massless has ZERO MOMENTUM,
it has ONLY ENERGY.


Not this old chestnut AGAIN! You are utterly wrong and it has been proven to you multiple times.

The article above again proves you wrong (even if you do not want to believe a doctoral student).

The article states; ""As soon as it breaks free, the photon momentum is transferred to the electron", explains Hartung's supervisor, Professor Reinhard Dörner from the Institute for
Nuclear Physics."

So, you are saying that you know better than a Professor of Nuclear Physics!

Well.... You do not!

Indeed, you are clearly both uneducated and uneducable.

Oct 02, 2019
Look, the photoelectric experiment has been out there for over a century and Einstein won a Nobel Prize in Physics for explaining it. This isn't some fringe thing or other like your EUdiocy, @Benni. This is real experiments performed in real laboratories by real physics students in real universities directed by real professors, not people who claim to be "nucular enginers" and can't do math.

Oct 02, 2019
This comment has been removed by a moderator.

Oct 02, 2019
Benni momentum is not "defined" as p=mv. momentum is a conserved quantity of a system due to translation symmetry. for classical matter like you're used to that quantity just happens to be accounted for by p=mv. for a photons its p=h/wavelength.

Oct 02, 2019
OK confession time, I quit reading the comments halfway down.

Thirty years spent researching this problem by those that make these questions their lifework. Results finally start coming in and it turns out all the readers of Phys.org already knew the answer. Not only that but the researchers are clueless and do not even know basic science and have to be corrected by the splendid cerebral musing of our resident experts.

If only the folks here would publish, it would save so much time and money wasted on those idiots that run our research labs at universities.
No satire label, smart folks know how serious I am.

Oct 02, 2019
I get the impression that you have no idea what the CLASSIC photoelectric effect of over a century ago, that Einstein was the first to fully explain, actually is. Light
.....again, here's a link to the actual paper Einstein wrote:

http://astro1.pan..._eng.pdf

......now what YOU should do is Copy & Paste for us where Einstein discusses PHOTON MOMENTUM in the photo-electric effect.

You claim to know so much more than Einstein about what appears in Einstein's writ about the photo-electric effect, then how about if YOU use EINSTEIN'S WORDS from his own treatise to prove that PHOTON MOMENTUM appears in his paper on the Photo-electric Effect?

As I explained above, I did an actual word search for PHOTON MOMENTUM in the paper for which Einstein won the Nobel & it appears zero times, how many times did YOU count just for appearance of the word MOMENTUM? I'll bet you don't even know how to do such a search.


Oct 02, 2019
Benni momentum is not "defined" as p=mv. momentum is a conserved quantity of a system due to translation symmetry.
......only for a kinetic energy system, none of the rest of YOUR math is found in Einstein's treatise on the photo-electric effect, it's only found in knock-off papers like this one that Hartung wrote.

You simply do not comprehend the fact an Electro-Magnetic Photon Wave is not Kinetic Energy.

Oct 02, 2019
The article states; ""As soon as it breaks free, the photon momentum is transferred to the electron", explains Hartung's supervisor, Professor Reinhard Dörner from the Institute for
Nuclear Physics."

So, you are saying that you know better than a Professor of Nuclear Physics!
......of course this is what I'm saying, why would you finish that statement up with a question mark?

This guy has no more education in the field of nuclear physics than I do & from all appearances has far less reading capability to prove his suppositions exist within Einstein's treatise on the Photo-Electric Effect.

So come on Pop-Cosmology aficionados, show the chatroom where Einstein discusses PHOTON MOMENTUM in that paper for which he won the Nobel Prize? Can't find it can you? You're reduced to finding others willing to put THEIR words in Einstein's mouth & in what he actually wrote versus what WikiPedia Experts say he wrote.

RNP
Oct 02, 2019
@Benni
......of course this is what I'm saying, why would you finish that statement up with a question mark?


I didn't. So we must now add poor reading skills to your growing list of shortcomings.

This guy has no more education in the field of nuclear physics than I do


Hahahahahahahaha (Oh, stop it, it hurts!!!)

A PROFESSOR of Nuclear physics has no more education in the field than you, an illeducated troll!!

This is one of the funniest things you have said in a long time and it almost makes time wasted reading your constant ill-informed drivel worth while for its entertainment value.

Nevertheless, back onto ignore you go.

Oct 02, 2019
@Benni

......of course this is what I'm saying, why would you finish that statement up with a question mark?


This guy has no more education in the field of nuclear physics than I do


Hahahahahahahaha (Oh, stop it, it hurts!!!)

A PROFESSOR of Nuclear physics has no more education in the field than you,
.......then YOU be the one to put up the math for the equations that refutes Einstein's treatise on the Photo-Electric Effect.........YOU can't find PHOTON MOMENTUM in it so it's time for a name calling rant.


RNP
Oct 02, 2019
For anybody wanting to see more clear evidence that Benni is talking out of his posterior, here are University of Washingtons course notes that lay out the mathematics very clearly; http://depts.wash...u-16.pdf .

Oct 02, 2019
@benji
This guy has no more education in the field of nuclear physics than I do
really? LMFAO
https://scholar.g...mp;hl=en

http://www.uni-fr...Doerner?

https://www.atom....furt.de/

Main Research Topics: Atomic and Molecular Physics. Few-Body dynamics. Ion Atom collisions (keV-GeV) (GSI, IKF), Electron-Atom and Antiproton-Atom collisions (CERN), Atomic and molecular physics with synchrotron radiation (Hasylab Hamburg, Bessy, Berlin , ESRF Grenoble, ALS-Berkeley)
this benji comment is even funnier than this one
the wobble cycle of Earth's rotational axis seems to correlate closely with the time required for our solar system to complete a full orbital passage around the galactic core of the Milky Way.
http://phys.org/n...als.html


Oct 02, 2019
@Benni:
If photons lack momentum, then please explain the well-measured and verified Yarkovsky and YORP effects in asteroids.

I'll wait. But I won't hold my breath.

Oct 02, 2019

Momentum is given by the equation, P = mv, P is the momentum of the particle, m is the mass of the particle, and v is the velocity of the particle, therefore a photon being massless has zero momentum.


Benni, this equation only holds at speeds very much less than the speed of light and does not apply for photons. there is a youtube channel called "Science Asylum" that has a video called "Momentum does NOT require Mass!!" that you would learn a lot from if you watched it.

Oct 02, 2019

Momentum is given by the equation, P = mv, P is the momentum of the particle, m is the mass of the particle, and v is the velocity of the particle, therefore a photon being massless has zero momentum.


Benni, this equation only holds at speeds very much less than the speed of light and does not apply for photons. there is a youtube channel called "Science Asylum" that has a video called "Momentum does NOT require Mass!!" that you would learn a lot from if you watched it.
......I only need to read Einstein's treatise on the Photo-Electric, all the rest of this stuff apart from that is all major head spin distraction.

The problem with novices like you is that you're just too damned lazy to study the actual contents of Einstein's paper, why is that? The answer being that it does not contain any reference to PHOTON MOMENTUM & isn't it Interesting that so far not a one of my detractors has thus far has done a Copy & Paste proving just the opposite.

Oct 02, 2019
The problem with novices like you is that you're just too damned lazy to study the actual contents of Einstein's paper, why is that? The answer being that it does not contain any reference to PHOTON MOMENTUM & isn't it Interesting that so far not a one of my detractors has thus far has done a Copy & Paste proving just the opposite.


Einstein's paper also has no references to the spherical shape of Earth, so I guess that means it's flat, right?

Oct 02, 2019
@Benni:If photons lack momentum, then please explain the well-measured and verified Yarkovsky and YORP effects in asteroids.I'll wait. But I won't hold my breath.


"According to the concept that the incident light consists of energy quanta of magnitude Rßv/N, however, one can conceive of the ejection of electrons by light in the following way. Energy quanta penetrate into the surface layer of the body, and their energy is transformed, at least in part, into kinetic energy of electrons. The simplest way to imagine this is that a light quantum delivers its entire energy to a single electron ; we shall assume that this is what happens. The possibility should not be excluded, however, that electrons might receive their energy only in part from the light quantum."

.....right here is the answer to your question directly from Einstein's paper on Photo-Electric Effect:

http://astro1.pan..._eng.pdf

Page 373 right hand column.

Oct 02, 2019
The problem with novices like you is that you're just too damned lazy to study the actual contents of Einstein's paper, why is that? The answer being that it does not contain any reference to PHOTON MOMENTUM & isn't it Interesting that so far not a one of my detractors has thus far has done a Copy & Paste proving just the opposite.


Here you go, sport: Einstein derived the momentum of a photon in a paper in 1916: http://web.ihep.s.../eng.pdf

Oct 02, 2019
@Benni

If the electron receives kinetic energy from the photon the electron's momentum increases.
Therefore, the photon transferred some of it's momentum to the electron.

The recoil of the atoms nucleus is also due to the transfer of momentum from the photon as well.

Oct 02, 2019
"According to the concept that the incident light consists of energy quanta of magnitude Rßv/N, however, one can conceive of the ejection of electrons by light in the following way. Energy quanta penetrate into the surface layer of the body, and their energy is transformed, at least in part, into kinetic energy of electrons. The simplest way to imagine this is that a light quantum delivers its entire energy to a single electron ; we shall assume that this is what happens. The possibility should not be excluded, however, that electrons might receive their energy only in part from the light quantum."

.....right here is the answer to your question directly from Einstein's paper on Photo-Electric Effect:

http://astro1.pan..._eng.pdf

Page 373 right hand column.


So, you're suggesting that the Yarkovsky and YORP effects are because light is liberating electrons from asteroids' surfaces via the photoelectric effect? Wow.

Oct 02, 2019
Doctoral student Alexander Hartung became a father twice during the construction of the apparatus.

And, he named them Photon and Momentum. Now, every evening you can here him shout -
"Dinner is ready! Photon get Momentum..hurry up before it gets cold. Now chew your food slowly, I can't understand why you're not gaining any weight"

Oct 02, 2019
@Benni

Straight from Einstein himself

"If a beam of radiation effects the targeted molecule to either accept or reject the quantity of energy hv in the form of radiation by an elementary process(induced radiation process), then there is always a transfer of momentum hv/c to the molecule,..."

Doc. 38 On the Quantum Theory of Radiation
Volume 6: The Berlin Years: Writings, 1914-1917 (English translation supplement) Page 232
https://einsteinp...rans/244

hv/c can be written as h/wavelength


Oct 02, 2019
yhhmm, being practical from real life experience

yes, it is fun to piss off the looneyticks who live in fairytale castles in the sky
& have no real world experience

ahem... a light sail gains acceleration when photons strike
giving up momentum as the photon vanishes from existence

thus, i would presume,
fulfilling the Law of Conservation of Energy

Oct 02, 2019
Let's reset this pinball machine, and forget about the argon for a second.The photon comes in a knocks an electron out of the metal.
.....a photon can do no such thing, knocking, because it does not contain Kinetic Energy, only particles of MASS contain Kinetic Energy, a photon is Electro-Magnetic Energy, it is massless.
I get the impression that you have no idea what the CLASSIC photoelectric effect of over a century ago, that Einstein was the first to fully explain, actually is. Light, typically UV, comes in, and electrons are quite literally knocked flying out of the metal, typically cesium or something with some very loose electrons, like so many bowling pins.

It isn't about solar-cells here, or photocells. We're not talking about an electric-power device.
says DanR

Benni said "SOLAR SAIL", not solar-cells.

Oct 02, 2019
There is a lot more than one photon, in these experiments.

Oct 02, 2019
I see that IdahoAstro and Will999 have just opened the new account here in physorg TODAY. I would ordinarily say 'welcome to physorg', but for the fact that they seem to be very familiar with the denizens of this website. And so I've come to the conclusion that they are "socks" for the purpose of down voting, as well as arguing about things they barely know anything about.

But this is what physorg has become. A science website for non-discourse and ad hominem by those who really don't like others talking about the science in the article, and who only wish to disrupt the discussions.
And CaptStrumpy STILL doesn't, and has never exhibited science knowledge of his own, nor maths, but only refutes and argues against the science knowledge of others. And if he doesn't succeed in driving anyone away from this site -- he sends out his attack dogs such as kl31415 and the other loony toons like 1208.

Sad that phsorg has come to this type of existence.

Oct 02, 2019
@Benni

If the electron receives kinetic energy from the photon the electron's momentum increases.
Therefore, the photon transferred some of it's momentum to the electron.
......you totally made it up that an "electron receives kinetic energy from the photon", a photon HAS ZERO CONTENT OF KINETIC ENERGY, it cannot pass on that which it doesn't have.

The recoil of the atoms nucleus is also due to the transfer of momentum from the photon as well.
RECOIL be it that of an electron or atoms nucleus is all about KINETIC Energy, not the VELOCITY (which you confuse as being MOMENTUM) of a massless EM Wave which raises the energy level of a particle to create motion.

Oct 02, 2019
@Benni

This is from your own quote
"Energy quanta penetrate into the surface layer of the body, and their energy is transformed, at least in part, into kinetic energy of electrons."

Your own quote!!

Oct 02, 2019
"According to the concept that the incident light consists of energy quanta of magnitude Rßv/N, however, one can conceive of the ejection of electrons by light in the following way. Energy quanta penetrate into the surface layer of the body, and their energy is transformed, at least in part, into kinetic energy of electrons. The simplest way to imagine this is that a light quantum delivers its entire energy to a single electron ; we shall assume that this is what happens. The possibility should not be excluded, however, that electrons might receive their energy only in part from the light quantum."

.....right here is the answer to your question directly from Einstein's paper on Photo-Electric Effect:

http://astro1.pan..._eng.pdf

Page 373 right hand column.


So, you're suggesting that the Yarkovsky and YORP effects are because light is liberating electrons from asteroids' surfaces via the photoelectric effect? Wow.
.....not me, Einstein.

Oct 02, 2019
Putting this up again because you have a habit of not reading posts, even your own Benni.

@Benni

Straight from Einstein himself

"If a beam of radiation effects the targeted molecule to either accept or reject the quantity of energy hv in the form of radiation by an elementary process(induced radiation process), then there is always a transfer of momentum hv/c to the molecule,..."

Doc. 38 On the Quantum Theory of Radiation
Volume 6: The Berlin Years: Writings, 1914-1917 (English translation supplement) Page 232
https://einsteinp...rans/244

hv/c can be written as h/wavelength

Oct 02, 2019
There is also the fact that the entire EM field trapped at the top of the atomic structure is what we call "electron potential" and adding energetic photons to this mix is guaranteed to transfer energy into the heavier regions of the EM field (i.e. Electrons).

Oct 02, 2019
Also, wave/particle duality implies kinetic transfer as well.

Oct 02, 2019
I see that IdahoAstro and Will999 have just opened the new account here in physorg TODAY. I would ordinarily say 'welcome to physorg', but for the fact that they seem to be very familiar with the denizens of this website. And so I've come to the conclusion that they are "socks" for the purpose of down voting, as well as arguing about things they barely know anything about.
Sad that phsorg has come to this type of existence.


I bragged way above that I only read half of the comments so guilt had me finish them all. Silly me never thought about the driving need for acceptance, it is what makes humans the social animals they are.

Threads that devolve into what his one has become do not usually merit a comment. No longer referring to the article itself, only to each other.
So I comment on that fact, killing two avatar birds with each stone. Or more, snicker.

Wheee...

Oct 02, 2019
@IdahoAstro
The problem with novices like you is that you're just too damned lazy to study the actual contents of Einstein's paper, why is that? The answer being that it does not contain any reference to PHOTON MOMENTUM & isn't it Interesting that so far not a one of my detractors has thus far has done a Copy & Paste proving just the opposite.


Einstein's paper also has no references to the spherical shape of Earth, so I guess that means it's flat, right?
You missed the deep irony of the comment you quoted: The word photon first appeared in the lexicon in 1926.

Oct 03, 2019
You dont understund that Nucleus of atoms expanding and recycling dark expanding pushing force which have example nature of expanding light.

Expanding light waves is dark for us, but we know, there is waves because we can register photons.

But almost all expanding light mass is in dark expanding waves.

Expanding lights interactive with eachother and get eachother expanding faster and faster. So expanding light moving faster and faster same way what matter and light expanding.


Oct 03, 2019
If anyone is interested the actual paper is here - https://arxiv.org...7278.pdf

Oct 03, 2019
.....right here is the answer to your question directly from Einstein's paper on Photo-Electric Effect:
http://astro1.pan..._eng.pdf

Page 373 right hand column.


Benni stubbornly reinforcing, what everyone else already knows, that he does not and cannot understand the paper he keeps referencing.

Even when presented with other papers by the same author which utterly invalidate all the faux science drivel Benni generated. :)

How does it feel to be caught in your own idiocy ?
Cause apparently you are not even capable of following your own gibberish and completely disproving your previous statements. :D

Let's try with this, I believe someone linked this on another thread a few weeks ago...

https://study.com...ons.html

Oct 05, 2019
I'm just a random passerby with no dog in this fight. My thanks go first to phys.org for providing this open platform. Next to Benni for determination and grit. But most importantly to the commenters who keep pointing out Benni's many mistakes and back it up with sources and argument.

Oct 05, 2019
Be careful of the equalism fallacy. All arguments are not equal; some (like those supported by evidence) are better than others. "Determination and grit" are not evidence.

Oct 06, 2019
I had a hard time understand from Hartung's own simplified explanation what was going on, but of course the paper was more informative:

"In the region of small momenta, the experimental (|pz| < 0.1 a.u.) and more clearly the theoretical (|pz| < 0.36 a.u.) Gaussian fit centers become negative, indicating a counter-intuitive "backward" shift of the peak of the momentum distribution against the laser propagation direction, as reported in previous experiments 6,7 and theory4. The electrons in the narrow central peak with nearly no kinetic energy are initially accelerated in the laser electric field with a slight forward push in laser direction by the magnetic field, but subsequently when returning to the parent ion scatter from it, resulting in an overall backward shift. At higher momenta (|pz| > 0.5 a.u.), no significant Ip-dependent offset can be seen ..." [ https://arxiv.org...7278.pdf ].

Oct 06, 2019
these sensitive measurements confirm expected conservation of momentum, and therefore confirm relativity.


Nitpick: The model used is classical physics momentum and so non-relativistic quantum mechanics.

But of course the pre-relativity troll is incorrect, his explanation for uneven radiated photon momentum spinning up asteroids in YORP cannot work. The process of photoelectric emitted electrons builds up a net positive charge on the asteroid in order to maintain charge balance, i.e. as much electrons return as is emitted - little to no net momentum (which is why YORP dominates).

Oct 11, 2019
@Benni
I found these 3 links that seem to correspond to what you were saying above after I googled the words" Einstein "photon momentum". Perhaps it isn't exactly the same, but here they are:

https://www.scien...0826.htm
(This one is the same as the one from physorg)

https://www.scien...2635.htm
From 2017 - "Hollow atoms: The consequences of an underestimated effect". More interesting.

https://www.scien...1429.htm
The practical use in Medicine for that 'little-observed effect'

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