That must be nice. I wish your deliberate ignorance were amusing to me instead of disgusting. It would sure make reading and responding to your posts more enjoyable. Since you apparently missed it the first time: -Dale
Just to summarize for those that may not have read the other thread. Your objection to using non-inertial frames was that the required frame forces (a.k.a. ficticious forces: http://en.wikipedia.org/wiki/Fictitious_force) do not satisfy Newton's 3rd law. These frame forces (e.g. centrifugal force) are required in order to satisfy Newton's first two laws in the accelerated frame, but there is no reaction force to the frame force. MacM's specific objection to the linearly accelerating frame is less clear. From his recent posts it seems to have something to do with Newton's first two laws (F = m a), but those laws are satisfied in the accelerated frame. -Dale
Not in the case of relative velocity being generated by another object. That is two objects A and B at relative rest and then A accelerates undergoing F=ma. It is inappropriate to claim that B is accelerating just because the relative velocity to A is changing. The relative velocity is not actual velocity regrdless of what current physics and relativity claim. Emperical data nor logic support such conclusions. Your tendancy to call such solidly founded views ignorance, etc., only deminishes your own character.
I must admit that I haven't closely read the thread you refer to, but do you really not accept centrifugal force as a genuine force? As I understood it during classical mechanics, the fictitious forces arise merely by the way F = ma looks in the general (translated and rotated) case. They're no less real than other forces, though the name suggests otherwise.
I do not object to use of non- inertial frames. Only object to considering the "fictitious forces" to be real forces. I prefer to call them frame effects, because they do not satisfy Newton's 3rd law (or F = ma, see my next reply). You may have a point wrt "A body at rest tends to remain at rest unless acted upon by an outside force" (see footnote) if one is unknowingly* using a rotating frame, sort of as I am while writng this on rotating Earth, but I completely miss understand you for the F = ma law. "m" is a scalar. "a" is a vectory pointing at the center of rotation. The centrifugal "force" is in the opposite direction to "a." I do not think Newton forgot the minus sign and meant to write F = - ma, do you? Please Register or Log in to view the hidden image! I like all of his three laws, just the way they are, with no list of exceptions which includes Coriollis and “centrifugal“ forces. _____________ *If while I sleep tonight, I am magically transported to a fast spinning planet an placed in bed in a room that looks just like my bedroom (but unknown to me everything is glued in place), then when I awaken and pull the covers back, (surprisingly hard to do), and start to "float" slowly towards the ceiling, I also notice that the lose part of the cover is now standing straight up, I think I would suspect the truth, not that some unknown real force was pulling me and the lose end of the cover toward the ceiling, but I am not sure. Perhaps I would wonder what was the mysterious force acting on me for a while, at least at first, but most likely I would wonder: “What the hell has happened to the gravity force - I am following a straight line, off towards space - thank God, for the ceiling!” For a few horrible moments, I might even think “My God, MacM may be right and we are running out of uniKEF flux.” Please Register or Log in to view the hidden image!
No, it isn't. That is what acceleration means, by definition. Relative to A, B's acceleration is defined as the time derivative of its velocity (as a function of time) wrt. A. It doesn't matter that B isn't undergoing acceleration due to some force, such as A is relative to B, because neither the definition of position, velocity nor acceleration has anything to do with force. Whadaya mean, not "actual" velocity? You mean, relative to A, B isn't moving? If so, I suggest you go outside, throw a few balls in the air, and convince yourself that from their position you aren't moving, especially when you have to walk twenty meters to pick them up. Or is there also a MacM definition of velocity being something other than the first time derivative of the position function? You mean "Empirical data and logic supports such conclusions." As indeed they do. For a man now disputing Galilean relativity, obviously struggling with simple coordinate system changes, such insults hold no more weight than being character assasinated by a spoilt five-year old. Quit your whining and come back when you've learnt something. Anything.
Hi Billy, In the rotating frame, the acceleration due to the centrifugal force is away from the center of rotation. If something at rest in the rotating frame (except at the centre) is not acted on by any other force, it will accelerate outward. If while you sleep tonight, you are magically transported to room that looks identical to your own bedroom but is inside the outer wall of a huge spinning space station, so large that the curvature of the floor is not measureable (like the curvature of the Earth), and spinning just fast enough that your actual centripetal acceleration is equal to the acceleration due to gravity, would you notice anything different? If you drop a ball, which way does it accelerate in your frame?
MacM has special magical powers. He just knows when things actually occur or actually move. I have twice asked him to share them with us. He told me I did not know when the explosions (in thread "is time universal No and its proof") just because adjacent to the explosion was a stop watch stopped by the explosion. Likewise, just because you carefully measure the rate of position change in your frame of reference, and think that is the velocity, it is not, if that results disagrees with MacM's current* special powers results for what is the Actual velocity. Don't think MacM is one of those fools who believes in an absolute reference frame. He will assure you that he does not and then argue as if he does. ____________________________________ *You must be a little sympathetic to MacM. He has been posting here for years, and it is hard to avoid being inconsistent, when you are making it up as you go along, instead of using physical laws and standard definitions. Please Register or Log in to view the hidden image! PS get him to explain an “elastic scattering collision” to you some time for some real fun. Last time I heard, it was when the incident particle did not lose any energy, but that may have changed by now. Only the inelasting scattering events of uniKEF flux heat stars as the flux passes thru, but they are rare and “elastic scattering” events dominate. Etc.
As usual, you are right Pete. I should have made it clear that I was still speaking of the case MacM brought up earlier. He had suggested that the "equal and opposite force" to the real centrifugal force was the wall pressing against my body as I was pressed against the rim of a rotating cylinder, or something like that. Thus according to MacM my dislike for centrifugal "forces" violating the third law was unfounded, but he put it a little more strongly than that. (I forget his exact terms, fortunately.) I.e. what I said, and was talking about, was only this case with NO* motion in (wrt) the rotating frame. I.e. object is, to use your words, "acted on by any other force" that supplies its real acceleration, or keeps it motionless wrt rotating frame. ___________ * this critical word was accidently left out priot to edit. (I am tired and dyslexic. going to bed now.)
On first guestion, I strongly doubt it if still in bed, but possibly if I stand up, certainly if I can carefully jump to the ceiling and touch it. On second ball question, it will not fall straight down as it should, but hit the floor a little behind that spot, by {1- (r/R)}R, I think, quickly done, so may not be correct. R is the floor distance from center of rotation, and r that of the ball when released.
Now if you are through babbeling, THINK. You just said the magic words "first time derivative of the position function". Make a graph showing A & B at rest (position A1 and B1). Now plot A & B after A has undergone F = ma acceleration and where A and B have had relative velocity. Hmmm. We now have A2 and B2. Guess what B1 and B2 are in the same location. B did not move. Yet you want to argue that it accelerated and that it had velocity. That defies your own criteria. More importantly I know and don't care what is the commonly accepted view. I'm trying to educate you and others to think. Only when you have enough knowledge and understanding to form your own opinions independant of what anybody else says can you claim to understand reality. You may or may not be right but you will at least be stating your own view and not merely being a parrot. They damn sure do not. Please post for us ONE case of recorded reciprocity of time dilation. Please post evidence, much less proof of length contraction. The fact is if I place meter markers between earth and Alpha Centuri (4.3 lyr) and then fire a rocket and accelerate to 0.866c. (Note 0.866c = 259,620,268.6 m/s). You would argue (if you accept Special Relativity) that the clock aboard the rocket was only ticking at 1/2 the rate of your earth based clock. According to your earth clocks it would take the rocket 4.965 years to make the trip (excluding acceleration and deceleration times). But the clock aboard the rocket would have recorded only 2.4826 years and you claim since he was traveling at 0.866c that he therefore could only have traveled 2.15 lyr. Hence space was contracted by 1/2. That however is not logical nor justified since you are ignoring the dilated clock tick rate used to measure the distance via d = vt. The reality is that if you observed the meter markers along the way and with the rocket moving at 0.866c relative to earth observers, since the rocket clock was ticking slow he would see markers passing by at the rate of 519,240,537.3 m/s. That means the rocket pilot would conclude he was moving at 1.732c!!!. That is what actual physics and logic support. Not spatial contraction per SRT. At v = c space does not contract to zero, velocity aboard the rocket appears to be infinite and travel to anywhere instantaneous because clocks have stopped. That is what any rational person should conclude and why relativity should be abandoned (or substantially modified). Ditto. Lets see you satisfactorialy argue length contraction to the contrary.
Actually, no, I didn't. But no matter. Ok. So the coordinate system we're in has A & B at rest. Fine. No, it doesn't, because you conveniently left out the final, and vital part of the sentence: "wrt. A". Come on, Mac. This is Galilean relativity - a simple coordinate change. You must be able to understand this. And in the coordinate system that has A at rest (which is what "wrt. A" means) B of course accelerated. MacM, this isn't philosophy. There's no value to be gained in arguing over such simple concepts as position, velocity and acceleration functions. If you want to abandon the usual definitions, fine, but don't presume that anybody will agree that they are somehow "wrong", because of your personal (and strange) dislike of them. Nobody has been able to get you to conjure up a definition of this reciprocity, so I'll merely remind you that I have in fact posted an article (from PRL) on length contraction in the past. No. In my frame of reference he traveled 4.3 light years. The space that was moving at 0.866c with respect to the rocket is contracted to half it's rest length, correct. See, you keep bringing this up as if it's profound. It's not; it's just wrong. Here's the thing: Even in Galilean relativity, mixing measures between coordinate systems is nonsensical. Let's go back to the A/B example. Your using the dilated clock time in the frame it doesn't belong to is equivalent to me stating that since from A's viewpoint A has no velocity, B can't possibly have A moving, because d = 0*t = 0. It's nonsense, nothing more. Only if he accepts that those markers are a meter apart, something that he could easily measure to be false - in his frame. See, you're implicitly assuming that length is absolute, and that simply isn't true. I'll not argue the wrong points here. MacM, when will you get it through your thick skull that nature doesn't care how you think it ought to behave?!
************************* Extract ************************* Oh really? [post=944646]Here[/post] Or is there also a MacM definition of velocity being something other than the first time derivative of the position function? ********************************************************* No it doesn't. What about your view is invalid physics do you not understand. I am not saying it is not what is generally done or accepted. I am saying it is BS and needs to be changed. You can lead the horse to the water but you cannot make him drink. Your refusal to acknowledge the merits of the arguement doesn't alter the merits. I have posted the Special Relativity description of "reciprocity" many times. You can choose to continue to ignore it but that doesn't make it go away. Yes, having to do with changes in magnetic fields as I recall. What does that have to do with "Spatial Contraction"? Remember I maintain dimensional contraction of material objects even in my own work. It is spatial contraction which is not valid. Yes. I said that. But your assertion that distance contracted because he clocked the trip in one half the time is bogus. If you maintain that clock A ticks at 50% the rate of your clock and you are computing distance by d = vt, where "t" is the accumulated time indicated on the clock then it is assinine to not retain the respective tick rates of the clocks. The correct formula must be d = v * t*gamma; in which case it can be seen distance did not change at all and the differance is indeed in the tick rate of the clocks. Not correct. As I have stated above. It is the error advocated by SR but it is not correct. What? Try again. This is nonsense. It is true and length only changes in your theory because you alter the units of measure (time) and disregard that you did so. Call time a ruler, now artifically expand the ruler compared to the standard against which you are comparing. Certainly the distance measurement changes but distance didn't. Don't be so thick headed. Ditto. One day you and many others will have to wipe the smirk off your faces when it becomes apparent SR can no longer be sustained becuase of its internal construct conflicts. Actual physics doesn't have infinite densities, singularities, reciproicty of time dilation, relavistic mass changes or spatial dimenional change (spatial length contraction). It all works just fine (in fact far better) without them.
You are exactly correct about the source of the frame forces (http://en.wikipedia.org/wiki/Fictitious_force). As to wether or not the frame forces are "real" that is a bit more difficult to pin down. On the other thread 2inquisitive made the excellent point that frame forces are required to explain some very real physical effects in the accelerated frame (e.g. earth's equatorial bulge or stress in turbine blades). In the accelerated frame they can accelerate objects, do work, cause stress and strain, etc. All very real and measurable effects. Therefore 2inquisitive (and NASA) did not like the term "ficticious" force. (That is why I have been using the term "frame" force because it emphasizes the source without de-emphasizing the very real effects it can have.) Can something that is not "real" be used to explain such real effects? On the other hand BillyT made the equally excellent point that frame forces do not follow Newton's third law. In other words, they accelerate objects, do work, cause deformations, and otherwise follow F = m a like real forces do, but they do not have an equal and opposite reaction force. Can you call something a "real" force if it does not follow all the laws governing forces? I can see the argument either way, however, as an engineer I am very fond of coordinate transformations. They vastly simplify so many problems that I would not want to get rid of them. So I prefer to treat the frame forces as real in the non-inertial frame, with the understanding that "all forces are real but some are more real than others". Although BillyT does not like the idea of making this list of "reaction exempt" forces, I think it is not too difficult since the list has only one entry: frame forces. In any case, if you are talking only about the acceleration of two non-interacting bodies then there are no reaction forces to consider so there is no conflict (other than semantics) between BillyT's and 2inquisitive's positions. -Dale
No Newton did not miss a minus sign. The point is that in the non-rotating frame the centripetal force causes you to accelerate towards the center of rotation. There is an acceleration and there is no centrifugal force. But in the rotating frame the situation is different: you are not accelerating at all. Therefore in the rotating frame there must be a centrifugal force in the opposite direction to balance out the centripetal force. This is the source of the minus sign for the centrifugal force. If you look at http://en.wikipedia.org/wiki/Fictitious_force you will see the general derivation of the minus sign in the "general definition" section. -Dale
The Coriolis force could eventually give it away, but with a sufficiently large and slowly rotating space station it would be very difficult to detect inside a normal-sized bedroom. I haven't done the math, so I could be wrong, but I believe that there would be one particular radius that would even give the exact same Coriolis force as experienced at any given lattitude. Then you could be completely fooled into thinking that you were still in your room on earth. Hmm, sounds like great fodder for an alien-abduction novel. The protagonist woke up during the abduction and is having flashbacks. Meanwhile everyone thinks he is crazy and he is trying to prove he is right. You would have to do some real literary work to make the physics experiments interesting. -Dale
Hmm, perhaps he has shared them with us. I don't know if any blood or hair etc. is required for the spell, but apparently "first time derivative of the position function" is the magic phrase for his powers. It's a bird, it's a plane, it's Big Mac! Please Register or Log in to view the hidden image! -Dale
Fair enough. I thought you meant acceleration, in which case it would be wrong. Sadly for you, the only arbiter on what is, and what is not, valid physics, is nature. If we use relativity theory to predict how nature behaves we get good predictions, whether you like it or not. Of course, in your case the merit of the argument is null. Humour me. Do it again, and we'll see whether we can agree that str does indeed predict what you think. Because, oddly enough, I don't think we will. Why? He can measure the speed of the star to be 0.866c, and the time it takes to reach him as 2.4826 years (your numbers). Now, d = vt = 2.15 light years. You're saying that becuase he accelerated in the past then he can't use d=vt to calculate distance anymore. But that begs the question of just who can! Which leads to an absolute reference frame. Which is inconsistent with the way the universe is known to behave. No, it isn't. There's no way to distinguish which is the "true" clock rate. From the rocket's point of view the time elapsed on the Earth clocks will be 1.2423 years when the star reaches it. gamma times that gives a "true" time of 2.4846 years. Who is right? How do you know? How do you know the Earth wasn't accelerated far in the past? How would you find out? But that gamma must mean that there is some frame in which gamma is zero. An absolute reference frame. If you don't agree then try your thought experiment without knowing which of A and B accelerated, such that you only know there's relative velocity (such as is our situation with everything in the universe). Whom of A and B has the "true" measure of distance and time? For which we have your word against 100 years of experiments. Forgive me if I don't agree. Or don't, I really don't care either way. No more so than your claim that we have to factor in clock rates to calculate distances. You're pulling a quantity (time dilation) from one frame, and using it in a frame it doesn't belong in. This is exactly the same I did to "prove" that the rocket doesn't move. I just went ahead and took velocity instead of time. If you can say that in "reality" gamma*t (which is the time elapsed in the Earth frame) elapsed instead of the measured t in the rocket, then I can say the velocity of the rocket in it's own frame can be used to calculate distance in the Earth frame: You can't change the rules to allow you to mix frames, and then forbid me to do so. From the rockets point of view, a meter is still a meter, and a second is still a second. There's no way to check that we've "altered" the measure! Furthermore, if we return the rocket to Earth, and line up the respective meters and clocks, they'll be one-to-one. How will you ever know which distance is the "true" one? As I've stated many times str is just a 4D spacetime with the Minkowski metric. The Minkowski metric is easily verified to be an actual metric and we model spacetime by R<sup>4</sup>. You may not know much about metric or vector spaces, but the strange term "internal construct conflicts" simply doesn't apply. Again, nature doesn't care if you think it's irrational.
Funkstar, Sadly for you I haven't seen you or any of the other relativists post data showing SR reciprocity of time dilation or spatial length contraction. Ok. ********************* Extract ************************* http://www.mathpages.com/home/kmath307/kmath307.htm A Primer on Special Relativity ........................................................................................ ......................................................................................... Given this definition of inertial reference frames, the principle of relativity asserts that for any material particle in any state of motion there exists an inertial reference frame - called the rest frame of the particle - with respect to which the particle is instantaneously at rest (i.e., the change of the spatial coordinates with respect to the time coordinate is zero). This principle is usually extended to include reciprocity, meaning that for any two systems S1 and S2 of inertial coordinates, if the spatial origin of S1 has velocity v with respect to S2, then the spatial origin of S2 has velocity -v with respect to S1. The existence of this class of reference frames, and the viability of the principles of relativity and reciprocity, are inferred from experience. Once these principles have been established, the relationship between relatively moving inertial coordinate systems can then be considered. ******************************************************** Now given that both frames have equivelent rest and both frames see the other frame as having all velocity, SR mandates that each clock ticks slower than the other - A physical impossibilty and not what data shows happens. If you have two clocks at inertial rest and then you accelerate one clock producing relative velocity. Subsequent comparison of the clocks shows that only the clock that accelerated has accumulated less time. Relative velocity had no impact on the clocks. Of course he can use d = vt but he would be foolish to not understand that his units of measure have changed, not the physical distance. It is really amazing to see such educated people that don't realise if you change the ruler, measurement changes, but distance didn't. The distance is universal and DID NOT CHANGE. Undersand yet? I didn't say anything about "True" clock rate. That is assinine. I said retain the comparative tick rates in your measurement. You are changing the ruler. Distance is not changing. Wake up. The only thing you can know and the only thing ever demonstrated by data is that ONE clock may become dilated. In every case of record the clock that dilated is the one that accelerated and experienced F=ma. Relative velocity has not once been the cause of a clock dilating. Therefore given a case of unknown origin of motion between two objects a comparision of tick rates will only tell you which accelerated more. See above. A or B may tick slower. It is the one with the most historical acceleration. Perhaps it is time you should care because my words are absolute fact. NOT ONCE IN YOUR 100 YEARS OF EXPERIMENTS HAS SR BEEN DEMONSTRATED AS ADVOCATED. ONLY A ONE WAY GAMMA FUNCTION HAS BEEN DEMONSTRATED AND IT ONLY AFFECTS ACTUALLY ACCELERATED (F = MA) OBJECTS. NEVER RELATIVE VELOCITY. One way gamma suggests an absolute system not relative system. False. You are ignoring the change in your ruler being used to measure distance (t). Surely you have enough brains to understand if you change your measurement standard then the measurement changes. This is no different than making a ruler two foot long marked off as 12 inches. I'll measure distance to be half what it was but distance didn't actually change did it. Using time (at 1/2 tick rate) is the same as the two foot ruler. That should be obvious by now. There is only ONE distance. It is only the units of measure which changed. Universal, physical distance, did not change. In other words if you see the size of the moon from earth in the night sky while at relative rest and then you fly past the earth looking toward the moon, in the same comparative postion, at high relavistic speed, the fact is you will not see any change in the size of the moon as you pass earth. It is not as though you have shrunk the distance in half. The distance did not change, the size of the moon is not changed, only the calculated measurement has changed. All these computer generated movies of what the universe would look like at relavistic speeds is outright fraud. Given the case I stated where there are meter sticks between points in space, at relavistic speeds the ONLY affect would be to see the meters pass by faster. i.e. - You would conclude you had a higher velocity. There are no distortions or curving of space around you as taught. Since you don't seem to understand what those conflicts are I doubt you can make such statements with any authority. Nor does it care that you believe in relativity. It continues to repeatedly show you that relativity is flawed but you choose to ignore what it (and I) tell you.
