studiot

This is an interesting question that has many ramifications in GeoPhysics, but could you narrow it down a bit ? Also you say conducted, do you know the difference between conductive current and displacement current ? Finally the Earth is far from homogeneous and the values for sigma and epsilon vary with local materials eg seawater v granite.

This next comment is very important. The Physics an Chemistry of how what we call electricity is very difficult and complicated. Futhermore there is not one single mechanism, but several. And they all have a part to play. As a result, abstract models of how thing behave were developed, models that show measurable quantities like voltage, current and so on. These models are called circuit theory and are set in the mathematics of the relationships between the various measurable quantities. Have you heard of Ohm's Law ? Of course since they are both approaches about the same thing there is a lot of overlap and common stuuf involved. But there are also important differences and flow is one of those differences. Flow appears in artificial abstract circuit theory, but not really in a physical description of what is actually happening. And flow refers to flow of charge, as Mordred said, or current which literally means flow of charge in electricity theory. Anyway the important thing to remember is to know which version you are using. You ask about electric and magnetic fields, so it is important to know just what a field refers to. A field occurs in a region of space (along a line, on an area or in a volume) for which some quantity has a single defined value at every point in the region. The defined quantity may belong to matter or be totally abstract. So a temperature field or a density field are both about properties of matter that can vary from point to point. A placement of arrows on a weather chart showing which way the wind is blowing and where is purely abstract and called a direction field. An electric field shows the strength of attraction (as a force) that would be felt by a unit electric charge at any point. A magnetic field shows the strength of attraction (as a force) that would be felt by a unit magnet at any point. Neither of these are used much in circuit theory, but both have lots of different uses in Physics and Chemistry, often where there is no circuit involved at all.

OK so here is a further analogy Take a string and either tie one end to something fixed, and then take the loose end and pull it out straight. The flick the end you are holding up and down. You will cause the flick to travel along the string to the far end. You can also do this without tying one end but is is ahrder to get the flick to go all the way to the other end. Now here is the thing. That flick maintains its shape and size pretty well all the way down the string. That flick is a packet of disturbance that travels along the string. That is what we mean by a photon being a packet, but in a way suitable for EM radiation, not exactly the same as the flick on the string. One definite similarity. Both the flick on the string and the photon packet contain more energy than the undisturbed state. So the travelling pulse (flick) is a method nature uses to tranfer energy from one place to another. The next thing we need to do is to deal with fields, but I will stop there for you to digest this and to point you at your electricity question where the discussion of fields is better placed. Then we can return to this thread and complete it.

It doesn't. The hosepipe analogy is best forgotten.

I think Dima uses a translator. His aim was stated very clearly and coherently, as I have already noted. However the conditions he proposed to achieve this aim were not, in fact I agree that instanteity and simultaneity are both nonsense, quite apart from the 'acceleration into a moving frame a v' whatever that might mean. So I described it as nonsense. Your post was next and it could only have been reply to Dima's opening post as it followed on straight after th op (How I wish this forum would go back to its original format and number the posts). But it made no sense either. The cars couldn't have a reference frame once they started moving, given your stated conditions. So if you were trying to say the same as I am now saying, viz that Dima's original aim meant his conditions were inappropriate that's fine, But I don't see it put very well. BTW who is MD please ? I think most participants is this thread know and agree that these conditions are neither necesary nor possible. Ditto Forgive me, I don't see any explicit reference to such a rod, although rigidity is again not the issue. I respectfully suggest that both of you are getting tangled up trying to square the circle and start accelerating all parts of a train both instaneously and simultaneously, with or without magic signalling. If you want to accelerate a train, just tell tha man to put the engine at the front and pull or at the back and push. No part of the train will ever be moving sufficiently fast, relative to any other part of the train, for either SR or GR calculations to be needed. If you want to introduce an outside observer (which may be what Dima had in mind) then again say so and introduce relativity appropriately.

Thank you Mordred, I downloaded the pdf though I have seen some of this before it is more modern than my knowledge.

Are you going to comment on my reply to this ?

In fairness I don't see that allowing the train to turn makes any difference, except to add needless complications to the mix. I don't know if anyone can remember th slow motion video I posted a while back of a slinky being dropped from a tallish building by first letting go the lowest part of the slinky so it started uncoiling, and then releasing the top from its mounting so the slinky as a whole aquired a downward motion, additional to the stretching of the coils.

What do you think the OP's original intention was? He presented a scheme for accelerating all the cars of a lengthy train together, and in another post he explicitly said it would need to be done without signals being sent between cars. I addressed that implicitly in my second post. In order to keep the cars all spaced properly as they get length-contracted, the rear cars have to initially accelerate faster than the forward cars, and then the forward cars have to catch up later. Actually he didn't. What he actually said, in a rather strange style, was If we want to accelerate a very long train. which makes sense. The next part was nonsense. So we are left with wanting to accelerate a conceivable physical object to whit one very long train. Perhaps that is what led you to make the next post which also seemed nonsense to me The differential timing of the motions between adjacent parts or sections of the train in the limit tends zero as the initial distance between the sections of the train tends to zero. This is the condition that allow the train to move as a whole. This will happen quite naturally in an orderly fashion without all the paraphnalia later described. It is also the 'long rod' example as Mordred has pointed out.

I feel this train is running further and further down the track of fancy, rather than fact and further and further from the OP original intention. This is another way of putting what I said earlier, though I didn't know it was called Born rigidity I can well believe that this line of thought was started by Max Born, he certainly discusses it in his book. No one has yet replied to it.

Kinematic treatments are point particle by nature. Furthermore in both SR and GR, as far as forces can be considered at all, the Newtonian condition that internal forces cancel out when considering systems, does not apply.

That's a good way to confuse you readers, but thank you for the reply. Talking of reading, I listed four undefined terms, you have only answered about one of them. No they can't be. Dates have a reference zero. It is one of the basics of relativity that there is no such thing as a reference zero. By the way, welcome and please note new members are allowed a total of 5 posts in their first 24 hours as a very effictive anti spam measure. So use your last one wisely, (I can happily wait another day for my next answer).

Nice point +1

Thanks for the reply, but you seem to have missed the point of the article and my headline question. The sham they called the recent climate conference (COP27 I think) produced at least one good result. Namely that richer nations are putting some resources into helping poorer ones play their part. To me at any rate an, I would think it would not take much of this money to help extend seagrass and also mangrove margins. It is also true that the oceans were and still are the largest carbon sinks on the planet, so it make real sense to promote their function.

interesting. +1

You first asked about packets, so let's deal with that first. When you switch on a lightbulb, the lightbulb sends out the beginning of a pulse or stream or whatever you like to call it, of 'light'. When you switch it off again there is an end to the light. That large chunk of light is a large packet in very crude terms. Now it turns out that a stream of light is composed of very much smaller chunks of light, rather like a chunk of copper wire is composed of very much smaller chunks of copper, called atoms. These smaller chunks of light are not atoms so they are called 'packets' and they share, with the copper atoms, the property that they are the smallest chunks of that particular type of light. These small packets have a beginning and an end, just like the big one you generate with the lightswitch. Does this help and are you ready to move on to the rest of your questions ?

This problem is a classic example of forgetting that both SR and GR are point function theories. Difficulties can easily arise if you try to apply either to 'bodies' or systems that are too large to be considered as 'point partcles'.

This is a classic fallacy / 'paradox', due to trying to combine too many mutually statements into one. If you break down statement A into singleton statements you can see this.

Can you please explain what you are trying to do here?

Mechanical wear by friction and by impact against the end stops is by far the biggest culprit, because such processes are much faster than long term deterioration. Components are normally (or should be) made of materials that can resist the acceleration/deceleration stresses they encounter in normal operation.

I fail to see a definition or explanation of what you mean by any of these four terms you are playing with words with. You start of with the premise that spacetime and by implication time exists. Yet in your second post you claim You need to post proper derivation and discussion of this claim here not on any linked website - Those are the rules here. Are you claiming that time does not exist ? What is the difference between what you call 'time' and what you call 'physical time' ? Since you have distinguished 'physical time' are there any other sorts of time and, if so, are they relevant to your argument ?

https://www.bbc.co.uk/news/world-africa-63901644

Very interesting comparison. +1

Noted thanks. Yes, I am watching with interest and learning lots as I don't really know much about AI.

Thanks for the info. So am I right in assuming that Your red box denotes an input question and your green box denotes the AI response ? It seems to me that the AI is conditioned to always give an answer, unlike a human. Isn't this a drawback ?