Light some interesting questions and an observation

[trogan]

This is odd, because (i) this is a classical physics problem and (ii) how do you think we design all those synchrotron radiation facilities?

Zz.

I would settle for an animation of the classical physics problem.

 

[trogan]

1. There ARE visualization tools for physics concepts in education. See the http://phet.colorado.edu/index.php" project for example!

2. "Visualization" is way overblown in this case. I'm NOT saying they aren't important, but trying to visualize 6D phase space, for example, and drawing it in 3D (or 2D as is the case) is a futile attempt and are done only for "public relations" to those who have no clue of the physics.

3. People don't complain about such thing to musicians when they represents their music using music notes. They somehow don't get the idea that when physicists read mathematical equations, those equations can, in fact, give the "music".

Again, simulations and "visualizations" are used ALL THE TIME in physics. It may not be the type of simulations that you think, or what you get out of some silly video game, but it is done!

Zz.

I am being very naive I know. Sorry to annoy you. PhET is great ! Any more sites like it ?

There is a book on amazon that promises to help me with visualisations. Are you aware of it ?
https://www.amazon.com/dp/0387989293/?tag=pfamazon01-20
also
https://www.amazon.com/dp/0387002316/?tag=pfamazon01-20

 

[ZapperZ]

I would settle for an animation of the classical physics problem.

Finding the numerical solutions to differential equations IS one such "animation". This is done all the time!

Zz.

 

[ZapperZ]

Addendum: This is an example of "simulation" and visualization that is done in condensed matter, and one in which anyone who isn't familiar with physics would NOT have realized that these ARE simulations.

http://arxiv.org/PS_cache/cond-mat/pdf/0407/0407555v1.pdf

So no more nonsense about the idea that simulation/visualizations are NOT done in physics. Just because you didn't realize that this is done, doesn't means it isn't.

Zz.

 

[Galap]

I have some very vexing questions regarding light. We seem to know so little about it.

1. What happens to light when it is not traveling ?

2. Does it accelerate in reaching C ? If not does it "jump" to C ?

3. Can it be destroyed ? If not it seems to me that the amount of light in the universe is constantly increasing. Is this a valid statement ?

4. Why does it travel in a particular direction and what determines this ?

5. Two light beams traveling in opposite directions will meet at a speed of 2C (this has to be true if C is a constant). Doesn't this contradict Einsteins theory of relativity regarding C.

6. How is light absorbed into a particle ? ie what is the mechanism.

7. Where does it end up ?

8. On a slightly different topic, I have a question regarding time and the speed of an object. If time slows down for an object as it speeds up, is this not explained by the fact that it also becomes more massive as it speeds up ? As a result of this, interactions with photons will take longer thus causing a subjective slowing down of time as far as the object is concerned. In other words time is about rate of change. Are speed and mass equivalent ?

Tony

1. Light is always traveling. Because it has no mass, it can never stop moving.

2. Light always travels at speed C, unless there is a material in the way to block it or effectively slow it down, but this can be more seen as a time delay between absorbtion and emission.

3. When a photon is absorbed by matter, it ceases to exist. As for the amount of light in the universe increasing, yes. All of the matter in the universe will probably eventually 'evaporate' into light.

4. Well, this question is kind of hard and unanswerable. There is strong evidence that photons are fundamental, and therefore there is no real 'reason' as to why they exhibit the properties that they do. Light travels in one direction because it is an electromagnetic wave that self propegates through space, and the way the oscillating EM field works causes it to travel in a straight line. This doesn't really answer the question.

5. What relativity means is that no matter what frame of reference you are in, the speed of light remains constant. If you are an outside observer, you see the light beams moving at speed C. If you are one of the light beams, you see the other moving at you at C.

6,7. The photon ceases to exist and its energy is converted into energy within the particle. Looking at this from a wave perspective makes it easier to intuitively understand.

8. The mass increases in order for momentum to be conserved in all frames of reference. In one frame you see a lighter object moving faster, while in another you see a heavier one moving slower. I wouldn't say that mass and speed are equivalent, but depending on your frame of reference, they seem to interchange.

 

[trogan]

3. When a photon is absorbed by matter, it ceases to exist.

I ahve beeen told in an earlier reply that it exists in matter as a phonon ?

 

[Galap]

I ahve beeen told in an earlier reply that it exists in matter as a phonon ?

Well, as stated in that post, sometimes the energy is absorbed by the electron shells, but most of the time, it simply gives the atom a kick, which, due to the fact that there are probably lots of other atoms nearby/bonded to it, causes the material as a whole to vibrate. Just as photons are units of EM energy being transferred, phonons are units of vibration in a substance (which is more commonly known as sound). But phonons aren't photons.

 

[trogan]

5. What relativity means is that no matter what frame of reference you are in, the speed of light remains constant. If you are an outside observer, you see the light beams moving at speed C. If you are one of the light beams, you see the other moving at you at C.

I am quite familiar with relativity and C. A book, "Why E=MC2 and why should you care" (by two esteemed physicists), gave me some really great insights into the way Albert E. conceived relativity. So, if I (stationary) observe the light beams moving at C then, ipso facto, they will meet at 2C.

 

[Galap]

I am quite familiar with relativity and C. A book, "Why E=MC2 and why should you care" (by two esteemed physicists), gave me some really great insights into the way Albert E. conceived relativity. So, if I (stationary) observe the light beams moving at C then, ipso facto, they will meet at 2C.

I think the error lies in an unintentional shift in reference frame. If you are an outside observer, with two light beams moving towards each other, one is going C (lets say East to make it easy) and the other is going C west. There is no 2C involved. Logically, though, one might think that one would add the speeds, but saying they meet at 2C requires one to shift the reference frame to one beam to assume its speed is 0. I hope that makes sense, because I think I worded it awkwardly.

 

[trogan]

If I properly recall the premise of The Dreaming Universe
What connection is there between your research and the physical properties of light? Are you trying to build a quantum computer that runs calculations with minimal power and time?

I am a software developer who believes we have missed the boat designing operating systems that are functionally oriented. I believe operating systems should consist of interacting state machines. I am looking to extend current UML statecharts to make them more powerful and easier to use. In the process I have decided that the best state machine around is the human brain as you also note. Light, of course, in that system is the means by which events are communicated between neurons. So I am trying to learn as much as I can about it.

 

[trogan]

I think the error lies in an unintentional shift in reference frame. If you are an outside observer, with two light beams moving towards each other, one is going C (lets say East to make it easy) and the other is going C west. There is no 2C involved. Logically, though, one might think that one would add the speeds, but saying they meet at 2C requires one to shift the reference frame to one beam to assume its speed is 0. I hope that makes sense, because I think I worded it awkwardly.

Sorry, no comprendez !

 

[Dale]

So, if I (stationary) observe the light beams moving at C then, ipso facto, they will meet at 2C.

If you are talking about the "closing speed" then yes, it is not limited by c. The closing speed is not the speed of any object or particle. Similarly you can get shadows or dots or "points" that move faster than c without the speed of any particle exceeding c.

 

[trogan]

Scientific computation -- the simulation of physical behavior with computers -- is the world's largest use of computer power. Millions and millions of people spend their entire careers developing and running computer simulations. An absolutely astounding amount of our current scientific understanding was made possible by computer simulations. Your opinion is shared by, well, just about everyone.
- Warren

thx Warren. I am after the simulation of an electromagnetic wave by a traveling electron. With source code, so I can understand what is going on. And with the results 3D animated. Can you assist ?

 

[Galap]

Sorry, no comprendez !

Alright, let's try a different approach. Maybe this time it will come out better...

Two cars are driving on opposite sides of the road. Let's call them car A and car B. car A is moving at 50kph east and car B is moving at 50kph west. You are standing on the side of the road. Car A approaches you at 50kph. So does car B. You say that they meet at 100kph relative to each other, and that makes sense, but how did you arrive at that conclusion? You added the speeds. Why? Well, we know that if we're in car A, what car B does doesn't change, right, but if you're in car A, it looks like you're not moving at all. Look at the guy in the passenger seat. He doesn't seem to be moving. But does car B approach at 50 kph? No. Why? Because you changed your reference, you had to subtract out your speed and add it to the outside world, yielding 100kph.

Does this work with photons? No. You needed to change your reference frame to add the speeds, and changing your reference frame alters your perception of distance, time, and speed, so it doesn't hold for photons (of course, it isn't exactly right for the cars either, but it's close enough that it would be silly to use GR arrive at your answer).

I hope this is clearer :)

 

[trogan]

Your "problem" is a common one. Most people naturally wish to make sense of the subatomic world by using concepts that they understand from the macroscopic world. You're familiar with billiard balls and pendulums, and you naturally want those concepts to apply universally -- but they don't. A vast amount of evidence -- compiled by millions of people over hundreds of years of study -- indicates that the behavior of very small things differs from the behavior of large things. If you apply macroscopic concepts to microscopic experiments, you get the wrong answers, after all.

- Warren

This is quantum theory's biggest problem isn't it ? Namely the inability to explain reality via sub-atomic phenomena. Actually I put that badly. I am referring to wave/particle duality which is just not evident at the macroscopic level.

 

[trogan]

If you are talking about the "closing speed" then yes, it is not limited by c. The closing speed is not the speed of any object or particle. Similarly you can get shadows or dots or "points" that move faster than c without the speed of any particle exceeding c.

so information can be transmitted at 2C ? Is this consistent with relativity ?

 

[Dale]

No, information is not transmitted at the closing speed in any frame. Similarly with dots or shadows or points, none of them can be used to transmit information at greater than c in any frame.

 

[Born2bwire]

thx Warren. I am after the simulation of an electromagnetic wave by a traveling electron. With source code, so I can understand what is going on. And with the results 3D animated. Can you assist ?

The radiation from a moving charge is given by the Lienard-Wiechert formulas: http://en.wikipedia.org/wiki/Liénard–Wiechert_potential

EDIT: Crappy article, why the hell don't they bother to work out the fields? Anyway, if you're lazy and do not want to work out the fields yourself, Jackson's Electrodynamics text has the full formulas I believe.

 

[trogan]

I am getting the feeling that no animation of an electron generating an electromagnetic wave exists. I am also discovering that no visualisation of a photon is available in physics (ie 3d shape(s), size etc.). It seems to me that the two facts are related !

 

[Integral]

Not sure why, if you want to model "reality", what ever that may be, you would be spending so much time on Quantum effects. We do not live in a quantum world we live in the world of classical physics. While quantum physics can explain why something is the color it is or explain the chemical reactions which effect our existence, awareness and knowledge of these effects have little to do with our day to day lives.

At any rate, your goal to "model" reality seems undoable at the very best. Each to his own.

 

[trogan]

Not sure why, if you want to model "reality", what ever that may be, you would be spending so much time on Quantum effects. We do not live in a quantum world we live in the world of classical physics. While quantum physics can explain why something is the color it is or explain the chemical reactions which effect our existence, awareness and knowledge of these effects have little to do with our day to day lives.

At any rate, your goal to "model" reality seems undoable at the very best. Each to his own.

I don't want to model "reality". I want an animation. I want it so that I can better understand quantum physics. As a side effect if you like, if something is animated then a computer program will have generated it. I can read computer programs better than I can do maths. In any case I find maths is very limited in what it can describe.

My ultimate aim is to transfer ideas in quantum physics to state machines in computers. For example there are "events" in state machines that closely correspond to bosons in physics. This morning I discovered that virtual photons can "tunnel". So I will consider using virtual events in state machines in cases where no time is involved (ie in state "leaps").

 

[ZapperZ]

I am getting the feeling that no animation of an electron generating an electromagnetic wave exists. I am also discovering that no visualisation of a photon is available in physics (ie 3d shape(s), size etc.). It seems to me that the two facts are related !

Ah, so then those people who designed the undulator and wigglers in synchrotron light sources were doing it blindly. It's amazing how often they got so lucky, especially at the LCLS, considering that they had tolerances on the order of microns!

And your question on the visualization of a photon is strange, considering that a photon is define as a quanta of energy, and NOT as a clump of stuff in space like a ping pong ball. You might as well ask for a visualization of pain.

This whole thread appears to be built on quite a bit of ignorance on what is meant by modeling and "visualization" in physics. You appear to want certain things on your own terms, and when you don't find it, you draw up the conclusion that such a thing isn't done in physics, or that "math is very limited", forgetting the fact that there has been nothing that has been shown to describe physics better than mathematics, or that the computer you're using is described using math! You use the word "boson" without realizing that it isn't some handwaving entity, but something that is clearly described in physics using mathematics! If you have something, and it doesn't behave exactly as described in physics, then it isn't a boson!

I think we have given this thread a very long leash, and it is appropriate at this time to remind you of the https://www.physicsforums.com/showthread.php?t=5374" that you had agreed to. Pay particular attention to our policy on speculative, unverified posts. At some point, this has turned from wanting to learn about something (which we encourage) to promoting some strange and unverified idea. Unless the direction changes, this thread will end very soon.

Zz.

 

[trogan]

Ah, so then those people who designed the undulator and wigglers in synchrotron light sources were doing it blindly. It's amazing how often they got so lucky, especially at the LCLS, considering that they had tolerances on the order of microns!

And your question on the visualization of a photon is strange, considering that a photon is define as a quanta of energy, and NOT as a clump of stuff in space like a ping pong ball. You might as well ask for a visualization of pain.

This whole thread appears to be built on quite a bit of ignorance on what is meant by modeling and "visualization" in physics. You appear to want certain things on your own terms, and when you don't find it, you draw up the conclusion that such a thing isn't done in physics, or that "math is very limited", forgetting the fact that there has been nothing that has been shown to describe physics better than mathematics, or that the computer you're using is described using math! You use the word "boson" without realizing that it isn't some handwaving entity, but something that is clearly described in physics using mathematics! If you have something, and it doesn't behave exactly as described in physics, then it isn't a boson!

I think we have given this thread a very long leash, and it is appropriate at this time to remind you of the https://www.physicsforums.com/showthread.php?t=5374" that you had agreed to. Pay particular attention to our policy on speculative, unverified posts. At some point, this has turned from wanting to learn about something (which we encourage) to promoting some strange and unverified idea. Unless the direction changes, this thread will end very soon.

Zz.

It is good to see you so “animated” in your defense of physics.

I find it difficult not to speculate a little and, indeed, it seems to me that so much of mainstream physics is speculation (eg the various interpretations of wave/particle duality). Being a software developer I tend to look at “reality” as an information processing system and this colours my view on quantum physics. I have been a developer for over 40 years and am really, really good at it. Any speculation I engage in will, I think, tend to be insightful and (possibly) helpful. In any case I am guessing that many people in these forums will be interested in a software developer’s views on physics. I know I would if the opposite were the case.

I am sure rampant speculation is not good for the forums. I have also been following another thread regarding the nature of the photon and it seems to be largely speculation. https://www.physicsforums.com/showthread.php?t=104657". I found a lot of it it to be fascinating and helpful.

I am not saying that maths is inappropriate in describing physical phenomena and I use maths all the time when I program (I did maths at uni). I am of the opinion that state machines are the best way of describing reactive systems.

I agree with you that this thread has outlived its original purpose and intend that this is my last post. Thanks to all who contributed.

 

[Born2bwire]

It is good to see you so “animated” in your defense of physics.

I find it difficult not to speculate a little and, indeed, it seems to me that so much of mainstream physics is speculation (eg the various interpretations of wave/particle duality). Being a software developer I tend to look at “reality” as an information processing system and this colours my view on quantum physics. I have been a developer for over 40 years and am really, really good at it. Any speculation I engage in will, I think, tend to be insightful and (possibly) helpful. In any case I am guessing that many people in these forums will be interested in a software developer’s views on physics. I know I would if the opposite were the case.

I am sure rampant speculation is not good for the forums. I have also been following another thread regarding the nature of the photon and it seems to be largely speculation. https://www.physicsforums.com/showthread.php?t=104657". I found a lot of it it to be fascinating and helpful.

I am not saying that maths is inappropriate in describing physical phenomena and I use maths all the time when I program (I did maths at uni). I am of the opinion that state machines are the best way of describing reactive systems.

I agree with you that this thread has outlived its original purpose and intend that this is my last post. Thanks to all who contributed.

Physics isn't about speculation. Nobody publishes or seriously proposes speculation. Physics requires that the theories and ideas put forth produce results in line with current and previous observations. Our "speculations" on the properties of a photon as you have put it have very precise consequences that result in theoretical results that match experimental results to a very high degree. Quantum field theory/Quantum electodynamics is one of the most successful and accurate theories to date.

You ask for visualizations yet I do not think you understand what you are asking for. You are suprised that there are no visualizations for the radiation of a charge, but I doubt you looked at the equations that I gave you because if you had done so you would have realized how fruitless such an idea is. The radiation is dependent upon the velocity, acceleration, and relativistic speed of the particle. It is a complicated task to just talk about specific types of trajectories but it is done in any graduate level electrodynamics text like Jackson's. We can talk about linearly accelerating charges and synchrotron radiation easily enough but to ask for a generalized description is pointless because it differs for each possible trajectory.

You ask for visualizations of quantum mechanics but you haven't asked for anything. What do you want to visualize and why? As it has been stated previously, quantum mechanics is not a direct describer of the macroscopic world. It describes, indirectly, the behavior in the microscopic, "quantum," world and only connects to our macroscopic world through observables and statistical measurements. We cannot give you a direct visualization of a physical process in quantum mechanics. So what is your goal with these visualizations? If we gave you plots of the wavefunction, do you understand what information would be implied by such plots?

 

[trogan]

Physics isn't about speculation.

Maybe “hypothesize” is a better word. Or possibility “Interpretation” (as in Copenhagen). I realize quantum physics has had great success in predicting physical phenomena. Yet there is much about it that defies explanation and as such it is tempting to speculate. For example many knowledgeable people would say that wave/particle duality and the collapse of the wave function is not a correct theory. An article in your forums proposing a new explanation of the double slit experiment (https://www.physicsforums.com/showthread.php?t=199598") suggests strongly that this is the case ... and my understanding is that this is the very basis of quantum physics.

You ask for visualizations yet I do not think you understand what you are asking for. You are suprised that there are no visualizations for the radiation of a charge, but I doubt you looked at the equations that I gave you because if you had done so you would have realized how fruitless such an idea is.

I am quite happy to accept (but surprised) that what I am asking to be visualised, namely a traveling electron generating an electromagnetic field, cannot be done. Unless I have misunderstood some previous replies this is the first time that anyone has admitted this.

If we gave you plots of the wavefunction, do you understand what information would be implied by such plots?

Yes, sort of.

 

[trogan]

For animations/simulations of electromagnetic fields you can try http://www.vectorfields.com/".

 

[trogan]

7. Where does it end up ?
Tony

It seems to me that, unless absorbed by a particle, light will end up at the edge of the universe. Could it then be converted to space thus causing the expansion of the universe ? (and incidentally indicating that space is base state energy). Thus the breakdown of matter would be fueling the expansion of the universe. Which would be increasing over time if the number of stars in the universe is increasing.

Actaully, it seems better to say that the light is converted into an expansion force that is applied to the edge of the universe and this is the way the universe expands.