Hi Mark Thanks for your explanation on the speed of electricity, as distinct from the speed of a signal - the analogies are very helpful, but I also don't know anything, just teach electronics, thermodynamics and aerodynamics where all analogies are interwoven - indeed as I look deeper into the natural world I see a great deal of commonality. I also read Bill Beaty's contribution and agree with you - however a site that size needs constant maintenance and I guess he has some stuff that disagrees with other stuff he has written. He does make a good point about current and the fact that it isn't the factor that controls a bipolar transistor (though I am now unsure again--help!) Anyway, thanks again kind regards ---------------------------------------------------------------- Hi Mark, You say, "But nobody ever makes the mistake of supposing that the center of gravity has any objective reality in the physical universe. Everyone understands that it is merely a mathematical fiction" Maybe its my understanding of English that is at fault, but the centre of gravity of an aeroplane is extremely important in its design if it is to be able to fly with any stability. The CofG may actually "be" located in an airspace somewhere in the cabin and is not material, but it does have coordinates and therefore exists in reality. It is a location rather than an item. Coordinates on a map exist for every portion of a map, whether there is something at that location or not. The tail plane of an aeroplane maintains the angle of attack by rotating the body about the CofG - this CofG can move (as people move around inside, or fuel is used etc) so aeroplanes require trimming to adjust control surfaces to compensate. But maybe I misunderstood your sentence...still reading Thanks for publishing your thoughts -they are useful ---------------------------------------------------------------- Dear Mark, I have copied and pasted your riddle here, but ask the question that immediately springs to mind; can an electron exist without the rest of its atom? I know we suppose that free electrons are detached from their parent atom and move along a conductor, occupying vacant spaces left by the previous occupant. But your question seems to imply that it can exist independently. If it is the case that it cannot, then the movement of the electron in the varying magnetic field is also influenced by the presence of it's other components of the atom, viz nucleus, (protons neutrons) etc. In other words, is your question too hypothetical? It's, to me, like the question "What if...., as applied to an historical event. Once we say that we can fill in the rest with anything we like, since we cannot know. [question #6 from http://blog.plover.com/physics/em-questions.html omitted - mjd ] As discussed above, we might not get the same answer because the question might be flawed e.g. can an electron exist independently of the rest of the material of which it is a part? kind regards ---------------------------------------------------------------- > can an electron exist without the rest of its atom? Of course it can! How does a van de Graaf generator work? How did the Millikan oil-drop experiment work? What is beta decay? What is happening in a vacuum tube? ---------------------------------------------------------------- Hi Mark But in those instances the electron is en route from one atom to another - yes it can exist, but not independently, as your original question seemed to imply - there are other forces at work in your examples, which would mess up your maths, when asking the question. The electrons in a vacuum tube are no less traveling from one atom to another than they are in a conductor - just the spaces are bigger...I had supposed you had meant a free electron hovering alone near a current carrying conductor... ---------------------------------------------------------------- Hi Mark You say, "The theory of evolution is certainly one of the most important ideas in all of science." I beg to differ. It makes no difference to anybody on the planet. It can't be used in any medicine, scientific research, invent things or improve life. I happen to live quite close to Darwin's birthplace near Shrewsbury England and there is a shopping centre named after him so I suppose somebody is getting rich from it, but the extremely flawed theory, which lacks any real plausible evidence to support it (see http://www.creationresearch.net/research/research.htm for a fuller account of this) but does, of course, discount God, thus also discounting any fundamental moral law, and leaving every moral concept to the vagaries of popes and politicians. We can see the result of that, can't we? I can detect you are a deep thinking man and as such a companion, so I dare to say that maybe you could spend more time researching into exactly what evolutionists claim, that a creature effectively changes itself. This takes more faith, in my opinion, than to believe in intelligent design, since at least anyone who studies the universe can see a pattern, where evolution is random. I have already mentioned that I have discovered so much commonality between aspects of physics in aerodynamics, thermodynamics, electronics etc which all have deep mathematical explanations all signifying order - to sum up, a colleague of mine once observed that it would be a madman that proposed DNA resulted from an explosion (Big Bang) where in all other understandings of random explosions things are destroyed, not put into the most beautifully exact pattern of molecules that contain the very essence of you! kind regards ---------------------------------------------------------------- > I beg to differ. It makes no difference to anybody on the planet. It > can't be used in any medicine, scientific research, invent things or > improve life. You are mistaken. > exactly what evolutionists claim, that a creature effectively > changes itself. This is a completely incorrect characterization of the theory of evolution by natural selection. ---------------------------------------------------------------- Natural selection without intelligent thought and design is an impossibility - you wouldn't countenance such a suggestion for any other thing on the planet - how did water, air, sunshine, electricity etc "evolve"? ----------------------------------------------------------------