studiot

I'm sorry Robin, there can be no other explanation. You must work for British Rail! Points failure due to icing : 'The 'Wrong kind of snow' Trains running slow : 'Wrong kind of leaves' Water in signal box : 'Wrong kind of rain' and now, ................wait for it..............., the 'Wrong kind of change' Wow.

Exactly. There is another kind of change that does not involve time. Ergo you can have change without time. There is nothing more to be said.

I'm sorry. how did this add value to the discussion? Here is a field plot. Prove the charge distribution to be unique. I apologise in advance if you have more sophisticated drawing facilities than I do.

David, I like it. +1 Short and logically coherent. A clear simple example of change without time, I didn't think of. I have been wondering about the word 'abstraction' since it was introduced here. Thanks. One question: Nnouns can be 'concrete' or 'abstract'. Abstract (the adjective) in this sense has a more restricted meaning than in abstraction (the noun), which can be 'abstract' as we are using it or concrete as in the syrup which is an abstraction from sugar cane. What do you think?

The links are unavailable. Can you post the equations?

Robin, I said that change and time are different and that you can have one without the other (both ways). I also posted some examples somehwere in the depths of this or another long thread, I will try to look them out for you, but it will take me some time. Note that there is a difference between saying that some changes could still occur without time, and that time is not involved since time does exist so actual changes may occur over time. I would certainly grant that the majority of change needs different times for the two states involved in a change to occur.

Click on your user name in the top right of the screen. Choose 'Settings' from the drop down box' Choose 'Notifications' from the list on the left hand side (second from bottom in list). It is a good idea to monitor all the threads you start since folks will start to ignore you if you don't acknowledge their input as in this thread http://www.scienceforums.net/topic/86967-is-the-charge-distribution-for-an-electric-field-unique/ You have asked quite a few interesting and disparate questions over a wide range of topics in a short space of time. Might I ask where they are all coming from? And where the answers are all going to?

Better thought of as Force = mass x acceleration but acceleration = rate of change of velocity so Force = mass x rate of change of velocity = rate of change of {mass x velocity} (since mass does not change) and mass x velocity = momentum So Force = rate of change of momentum. It is the changing momentum that generates the force. They are simultaneous and the force is applied for as long (or as short) as the momentum is changing. Can you complete your question, now?

If you substitute the equation of the linear regression line into the defining formula for the coefficient of determination and play with the algebra for about a page you arrive at the definition formula for the coefficient of correlation.

I think I posited that you can have change without time so perhaps I ought to provide some examples. Any system that has multivalued outputs (so hated by mathematicians) such as step functions, parallel computing, quantum distributions which can be in more than one state at the same time. The change is clearly embodied in the selection process to obtain a particular output.

The answer is still No, even if the OP thinks he wishes to consider only the charges within the region since it is entirely possible to have zero charges within the region and the entire field and boundary conditions produced by an external charge distribution, even if there is an 'internal' charge distribution that could produce the specified conditions.

Be careful with this one, as many get it wrong since strictly the question is meaningless. See this thread. http://www.scienceforums.net/topic/86381-basics-of-batteries/?hl=anode#entry835998

Progress, so try reading my post#18 again and then ask questions about it. I can expand the bits you need further detail on.

Another situation is embodied in the method of (virtual) images, much beloved of textbooks for illustations and exercises in plotting fields. Textbooks usually tonly treat symmetrical situations, but the mehtod has application in the practical world in the estimation of work functions.

Aw swansont, you spoilt my surprise. Take any (isolated) point, P, in space. Let the Field region be specified as the space between a sphere centered on that point of radius R and infinity. For any charge Q the field is the same whether it is located at P or on any sphere, also centered at P with radius < R . I was careful before because I don't know if the OP has to find an example or counterexample for homework.

It would be interesting if you were to elaborate and confirm whether you think the answer to the OP is yes or no.

Agreed, those ignorant of the English Language are ignorant of the difference between ignorant and ignoramus. +1

No, but the converse is true. Classically, there is only one field configuration generated by a specific charge distribution, within a specified region of space. Is this a question about classical physics or otherwise? If you know and understand Poisson's and Laplace's equations, you should have come across Gauss's Flux Law, which provides any number of simple examples. Is this homework? I would also like to point out that as Laplace's and Poisson's equations are partial differential equations, their general solutuons contain arbitrary functions so cannot be unique. Particular solutions are extracted by means of the boundary conditions.

Well if you tell us what molecules you wish to sort, perhaps the chemists will scratch their heads and help. You can use electric and or magnetic fields to separate polar from non polar molecules or other particles for instance. Electrostatic dust precipitators are a good example.

What is energy? Beginners all too often get sidetracked by such questions as what is time? what is space? or what is energy? Any technical discipline follows the pattern of resting on a number of fundamental definitions and a some propositions. The propositions are called axioms in mathematics and principles in physics. Whatever the discipline, they are open ended. That is they are accepted without proof and rest upon nothing else. This does not mean to say that they are not the result of intense thought and practical investigation and also subject to revision in the light of better information. Further we can provide descriptions to gain an intuition of where, when, why and how these are used. Not making these basics open ended results in the sort of pointless disputes about circular arguments currently being enacted in the sister thread what is time? It should be noted that the structure of scientific disciplines is open at both ends. That is not only in its foundations but also to allow for future development. There is always something left to be discovered. This does not only apply to scientific disciplines. For instance you have probably changed money to go abroad. But what is money? What is value? what is price? They are basic definitions in economics. Money is not a thing in itself. It is a means to compare. A convenient container or wrapper to hold all the paraphanalia and processes associated with exchange of things. Energy too is not a thing, it is a wrapper to hold all the paraphanalia and processes associated with certain interactions of real physical things.

Uh?

You have certainly fooled our esteemed moderator with your pretty colours. Boring black is best for most purposes. You said and from your second post it seems that that actually want to separate molecules, not split them. Please confirm. If this is the case then boiling of the water in a microwave oven is a simple example.

A good start would be to understand what a black body is, and the tems emissivity and absobtivity. http://en.wikipedia.org/wiki/Black_body Are you up to speed on this first?

Even if you don't lock this thread, you should make at least this useful explanation a sticky.

I already showed one way to do that, and I believe others have also showed ways. It follows inescapably that since we are agreed time and change are not the same, there must be some area of non-overlap ie somewhere where they are different. Whatever that difference may be is a way to consider and even observe time without change. I'm glad you asked for more information. Comparison of actual events, of course. I was trying for a light hearted illustration of a situation where only one event actually occurs and this will be a different event in different circumstances. Since there is only one event there can be no change. Nevertheless we can use the mouse run times to compare possible events. So we are using time for a different purpose from measuring change. I did not say that temperature worked the same way as time, just that we could also use it to make comparisons. I should have perhaps said comparisons of mutually exclusive events. In fact temperature is defined for such non material things as empty space and therefore a particle kinetic energy explanation is incomplete.