Radiation energy of a moving particle

[Arcon]

Originally posted by Sammywu
Arcon, Thank you for your lesson. I just have some questions.
Does this mean we always assume that there is a certain background electric field E in space?

No. This was just one way to explain it and it was the simplest way. The whole notion is the same as it is in Newtonian physics - When a body is accelerated it's kinetic energy increases. For energy to be conserved that energy must come from somewhere else and as such there is a decrease in some other form of energy. Kinetic energy is not conserved. Potential energy is not conserved. Only total energy is conserved. You can push a charged ball by hand and the work you do on the ball is at the expense of the energy which came from your muscle's which comes from [ATP = "Adenosine triphosphate"

For info on ATP see
http://entertainment.howstuffworks.com/sports-physiology2.htm

The magnitude of the eletric field is relative so in some situations there can be an electric field in one inertial frame of referance and no electric field in another frame of referance.

Is it possible we can accelerate an electron by gravity?

Yes.

 

[tenzin]

The magnitude of the eletric field is relative so in some situations there can be an electric field in one inertial frame of referance and no electric field in another frame of referance.

How can this be?

 

[Sammywu]

Tenzin,

I am not sure where you want to lead to. Before I do something, I have a dumb question.

My friend, an EE master, told me that there will be photon ( EM wave ) radiation from a constantly moving free electron.

I thought only acceleration of a free electron can do that.

What do you think? Any answer about that?

Back to your question, are you trying to refer to the effect of magnectic force generated when an electron is in relative movmement which triggered Einstein's SR theory and the main part of ite SR electrodynmamic theory?

 

[Arcon]

Originally posted by tenzin
How can this be?

Think of it like this: Consider an inertial frame, S, in which there is only a uniform magnetic field given by B = B₀ e_x where B₀ = constant. If there is a charge at rest in S then there the force on the charge is zero in that frame. If a test charge, q, is at rest in this frame then the value of the electric field in that frame is E = F/q = 0. Now consider the same test particle moving in S. There is now a force on that charge due to the magnetic field of B = qvxB as measued in S. If there is a force on a particle in one inertial frame then there is a force on the particle in all inertial frames.

Now change your frame of referance to the rest frame, S'. Note that the particle is moving in S and at rest in S'. In S' the force is b]F[/b] and this is non-zero. The electric field in S' is E' = F'/q != 0

Therefore in S there is no electric field where there is an electric field in S'.

Arcon

 

[Sammywu]

Arcon,

Thank you for your lesson.
Apparently, you are very knowlegeable about SR and ED ( Electrodynamitcs).
In another thread titled 'SR and the earth, sun and galaxy' in subsection 'Special & General Relativity' of the section 'Astronomy & Cosmology', Edwin raised a question related to Lorentz force, ED and SR. Would you mind helping me and him there. Thanks

 

[Arcon]

Originally posted by Sammywu
Arcon,

Thank you for your lesson.
Apparently, you are very knowlegeable about SR and ED ( Electrodynamitcs).
In another thread titled 'SR and the earth, sun and galaxy' in subsection 'Special & General Relativity' of the section 'Astronomy & Cosmology', Edwin raised a question related to Lorentz force, ED and SR. Would you mind helping me and him there. Thanks

Sure. I'll give it a try. Glad to help. Can you boil it down to one question since that thread is getting pretty long? I'd rather not have to read that whole thread if I don't have to, especially if you can simplify to a single simple question.

Thanks

 

[Jwprox]

On subject, don't know if this has been posted yet

Conceptually these are some answers to your questions that do not even require math. (Although a thorough understanding of the algebra in special relativity will formally show you)

Think of 3 things:

1. Definition of mass.
2. What happens when a photon hits a massive object.
3. What will never happen when massive object is trailing a photon.

1. Mass is anything with resistance to acceleration, accleration is change in velocity... You can not accelerate something with a constant velocity like light can you?

2. Light is absorbed or reflected by mass, but that does not mean it has changed velocity. Either it gets taken in or spit out. So there is no real way to "push" light around, just abosorbtion or redirection.

3. A massive object can never catch up with light to apply force to accelerate it.

Finally, just use your imagination why something with mass can not reach the speed of light. If the speed of light is always observed to be constant IN EVERY FRAME OF REFERENCE a massive object could possibly have, then how is anything going to catch up with it. To clarify, picture a monkey chasing a dangling banana that is just out of his reach because it's attached to a helmet on his head. No matter how fast that monkey goes he'll never get that banana.

 

[ranyart]

Originally posted by Jwprox
Conceptually these are some answers to your questions that do not even require math. (Although a thorough understanding of the algebra in special relativity will formally show you)

Think of 3 things:

1. Definition of mass.
2. What happens when a photon hits a massive object.
3. What will never happen when massive object is trailing a photon.

1. Mass is anything with resistance to acceleration, accleration is change in velocity... You can not accelerate something with a constant velocity like light can you?

2. Light is absorbed or reflected by mass, but that does not mean it has changed velocity. Either it gets taken in or spit out. So there is no real way to "push" light around, just abosorbtion or redirection.

3. A massive object can never catch up with light to apply force to accelerate it.

Finally, just use your imagination why something with mass can not reach the speed of light. If the speed of light is always observed to be constant IN EVERY FRAME OF REFERENCE a massive object could possibly have, then how is anything going to catch up with it. To clarify, picture a monkey chasing a dangling banana that is just out of his reach because it's attached to a helmet on his head. No matter how fast that monkey goes he'll never get that banana.

There are monkeys that eventually give up chasing dangling banana's, they get together and some of them obstruct the banana's path by forming a perfect circle around the monkey that has a banana dangling from its helmet, one monkey take's position at the centre of the circle of monkeys, then as the monkey with the nana rebounds off the circle, eventually the monkey with nana will cross the central monkey's path, he then just picks the fruit when it comes to him!

 

[Jwprox]

Stupid Monkeys

If only we could explain the whole of physics using monkeys and bananas.

You can quote me on that.

 

[raptor5618]

I read this thread with a great deal of amazement. To think that someone would ask a question, get an answer and then say that's not it stupid is just a bad joke. Ok maybe the answer did not seem right but they did not counter it with reasons for feeling they were wrong and in some cases just saying why which is very much like a child. A discussion does not include ridicule or personal insults. To ask for help and receive it only to personally put down the person trying to help shows that this person is totally without class. They have worked on this for 10 years so why are they not explaining the answer to his own questions. Also I was just reading that a theory or proof cannot come to be unless there is a way to try and prove it wrong. So to say that the laws that have been created might be wrong well my thought on that is NO Kidding. Based upon what was observed and studied to day they seem pretty good and may continue to be good but who knows what the future will hold that may explose errors in what today seems perfect. He wants logical proof well protons go the speed of light. Why because they can. Why can't an object with mass go the speed of light. Never saw any going that fast so it must be impossible. No math not fancy manipulations.

Yep he may know more, be smarter, have the formulations that will turn physics on it head and you know what I think about that. Good for you. Because if you act in your life like you do here my guess is that you never have talked to anyone for more than a few moments where they were not trying to get away from you. There is far more to life than what degrees you hold, how high your IQ is and all the books your read and understand no matter how easy or hard. I am thankful that there are people who put forth this effort and work to understand the world around us. But at this point in time I think that it is foolish to think that we know more than a tiny bit of how everything works. So in the scheme of all knowing we know very little. even you.

I would think you are a self proclaimed teacher as no real teacher would use your techniques. Ridicule is not a motivator. I also have seen a total lack of reasoning behind why you feel an answer is flawed. Kind of remindes me of the old skit from Monty Pythong. "Yes it is, no it isnt"

 

[ranyart]

Originally posted by Jwprox
If only we could explain the whole of physics using monkeys and bananas.

You can quote me on that.

 

[motai]

Originally posted by raptor5618
I read this thread with a great deal of amazement. To think that someone would ask a question, get an answer and then say that's not it stupid is just a bad joke. Ok maybe the answer did not seem right but they did not counter it with reasons for feeling they were wrong and in some cases just saying why which is very much like a child. A discussion does not include ridicule or personal insults. To ask for help and receive it only to personally put down the person trying to help shows that this person is totally without class.

I have to agree with you. I read this article with complete shock. There were so many people in this article who tried to help answer Tenzin's question. He, however, rejected the help because it was not in the right format. Others tried and were shot down as well, even though they meant good intentions. These people were taking time out of their day to try to explain concepts, and they should at least deserve at least some respect. When I don't understand something, I accept all the help I can get, whether it be mathematical or philisophical-ish concepts. Its kind of a shame when these discussions turn into flame wars.

 

[lethe]

Tenzin on renormalization:

Originally posted by tenzin

Don't worry your level of math does not impress me. I know more than I have let on. I learned QED renormalization in about 15 minutes of reading a book I just picked up off the shelf.

Tenzin on why the speed of light is invariant:

Originally posted by tenzin
Lethe had nothing to do with my thinking. I have been considering this for over 10 years.

i especially liked how it takes him 15 minutes to learn renormalization (which is a pretty hard subject!), but after 10 years of thought, he still can't grasp special relativity (which is not very hard!)

but yeah, i agree with your sentiments. i was quite shocked when i spent time on what i thought were informative and helpful comments, only to be insulted and accused of ignorance.

just imagine, this guy is a teacher!

 

[Adrian Baker]

Originally posted by tenzin

The electron is a particle. It is not a wave because something can not be both.

Well I was diffracting some electrons the other day and when I turned up the accelerating Potential , the diffraction increased... How do particles do that then?

An electron may perhaps not 'be both' but that doesn't mean it must be a particle either!

 

[GRQC]

I found the following particularly amusing, in re: learning renormalization:

Any person who inderstands the probablity of coin flips can understand QED.

Apparently he didn't catch the fact that renormalization really has nothing to do with probability, showing a bit of confusion with the notion of probabilitic dynamics (basic quantum mechanics) and convergent Feynman integrals...

Also, anyone who claims to be an excellent teacher -- and in the same breath calls their audience stupid -- is really demonstrating their true colors.