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#31
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"James R. Freeman" wrote in message ...
He is right. Gravity is not constant from one location to the next. For example if we look a W. 105 and move to W. 15 we have moved from a gravity hole to a gravity peak.The core of the Earth is like spinning a egg, in our case the core has not come up to the speed of the surface and locations of higher mass move but give us the 2 valley 2 peak problem in mass/gravity. It is very much to note if You are doing station keeping on a geo-syn sat. . You can also stay at the same location and exoperience varions in the _apparent acceleration_ do teo gravity. I wouldn't call that Gravity not being constant. For Gravity to be inconstant would require that the Gravitational constant vary. -- FF |
#33
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Gene Nygaard wrote in message . ..
On 12 Dec 2003 09:05:15 -0800, (Fred the Red Shirt) wrote: [I probably snipped a bit too much. If the proper attribution is unclear, just go back to the earlier articles.] What you address here is an vagueness in human language, not an ambiguity in natural law. Good grief. What in the world do you think we've been talking about. Of course, it is linguistics. Evidently that is what you have been talking about, not I. I thought this was clear, but let me carify it now. When I refer to weight, without modifier, I refer to weight as defined by Newton's Law of Gravitation and that definition can be written thus: W = Gp * (m) / (r^2) Where Gp = G * mp. G is the gravitational constant mp is the mass of the planet to which the weight is referred m is the mass of the body whose weight is in question r is the distance from that body to the center of mass of the planet in question (assume a spherical cow, er planet) * is multiplication / is division ^ is exponentiation 2 is an integer greater than one but less than 3 W is then the weight of that body. One could define weight using different symbols and explain those symbols in a different language and that would be the SAME definition of weight, not a different one because scientific definitions are conceptual, not linguistic. What's really strange is that there are always some fools who will insist that when we buy and sell goods by weight, we'd want to measure some quantity that varies with location. How stupid can some people be? I never found any who wanted to do that, nor anyone who does because on a practical level wherever the measurement is made, even if it is made by actually measuring force, the variance is so small that most normal folks consider in negligible, or rather it IS so negligible that no one has any reason to consider it at all. I'll be damned if I can understand why you find that miniscule variance to be so disconcerting. It is a whopping 0.53%, even if you limit yourself to SEA LEVEL. Throw in Mt. Chimborazo, the highest mountain on Earth, and it gets close to 3/4 of a percent; more than 1 part in 140. Now, if you have a standard 400 oz t bar of platinum, do you suppose it would make a difference if they were units of force rather than units of mass? Would three ounces at $600/oz matter? I sincerely doubt that I shall ever be trading in precious metals let alone doing so at the summit of Mt Chimborazo. I repeat that for most folks any difference that results from neglecting the issue is insignificant. Get it through your thick skull that "weight" is an ambiguous word, I understood that already and am quite prepared to explain it. In Newtonian Physics, 'weight' is a force. Mass OTOH is the factor of proportionality between force and acceleration. In General Relativity, 'weight' is a geometrial distortion of space-time due to the presence of mass. So weight is either a force or a geometrical effect, depending on which model you happen to be using at the time. Those models only explain weight AFTER you have chosen to define it as the effect of gravity. They do not 'explain' weight. They define weight. If it [the pound] was defined as a unit of weight then it was simultaneously defined as a unit of force without regard to whether or not the person(s) defining it UNDERSTOOD that they were doing so. Bull****. The meaning of "weight" which is a synonym for "mass" in physics jargon Can you state the formal name any internally consistant physical theory in which weight and mass are synonyms? As illustrated above, that is true of neither Newtonian Physics, nor General Relativity. There are different quantities involved here. But there is no "natural law" which tells you what word you should be using for any of them. Agreed. You can choose to call a certain quantity "weight." Your doing so, however, does not magically erase other meanings which the word already had. Nor do those other meaning prevent you from using that same word to represent a different concept. It is those concepts I discuss using (or at any rate attempting to use) language to discuss those, rather than simply dicussing the language with no regard for concept. I know of no physical theory, nor any physicist that uses the words weight and mass interchangeably within the discipline of physics itself. In the first place, what in the world gave you the idea that what physicists do has anything whatsoever to do with "baggage weight"? Nothing. I was refering back to your statement: 'The meaning of "weight" which is a synonym for "mass" in physics jargon' In the second place, it isn't true. Ever heard of atomic weight? Molecular weight? Those are not weights. That the word weight appears in those terms does not make them weights any more than the use of the word force in the term 'corriolis force' makes it a force. Do you remember the days when atomic weight in physics was different from atomic weight in chemistry? When one of them defined it based on oxygen-16 being 16.0000, and the other defined it based on the natural mix of oxygen isotopes being 16.00000? No, I learned the formal defintion of the mole after it had been restated based on C-12. is quite proper and legitimate, well justified in history and in linguistics and in the law. Have you never heard the adhomition, 'The law cannot change a fact'? Surely the same is true of language, see below. No "facts" are being changed. My point exactly. Back to your boheaded pedantistic statement that so many authors have 'got it wrong' (my paraphrase) when they define the pound mass to be the mass of an object that weighs one pound. Surley a liguist such as yourself has sufficient cunning to understand that authors of textbooks often nay, typically employ esotheric defintions of terms in common usage for the the purposes of the curriculum. Thus if within that curriculum the pound force is defined first then the pound mass may be defined as the mass of an object which weighs one pound. Now mind you, I never had a course nor saw a text that actually bothered to formally define either the pound mass or the pound force. My physics texts only dealt with formal defintions of SI units and my engineering texts generally assumed a practical understanding of units of measure. But in what order an author chooses to introduce units and therfore which are derivative of the others may be based, or dare I say SHOULD be based on the approach the author wishes to take in teaching the material in question. An engineering text or physics text is not a text in the history of commerce, in the history of the standardization of units of measure by government burocracies, nor of lingusitics and the author need not slavishly adhere to such histories or histrionics so long as the bridges designed by his students do not collapse. These texts are not 'wrong'. Your arguemtn would only show show them to be wrong if they attributed the author's defintion's to a standards organisation. Here's a FAQ by the NPL, the national standards laboratory of the U.K.: http://www.npl.co.uk/force/faqs/forcemassdiffs.html Weight In the trading of goods, weight is taken to mean the same as mass, and is measured in kilograms. Scientifically however, it is normal to state that the weight of a body is the gravitational force acting on it and hence it should be measured in newtons, and this force depends on the local acceleration due to gravity. See? I'm right. About which of those two definitions? About the ambguity. There are TWO defintions. That IS just what I wrote befor, pounds are ambiguous, slugs are not. Can you get that through YOUR thick skull? No, you went beyond that, and claimed that pounds force came first. No I claimed that the pound mass could be losely defined based on the pound force. That is true. I can define pound force first and pound mass second, as perhaps is done is some texts or more importantly, I can assume that the reader is famliar with the pound force and not the pound mass and thus inform the reader that the pund mass may be define loosely, as the mass of an object that weighs one pound. What they measured and what they wanted to measure are in total agreement. So there is no room for you to claim this ambiguity in ancient times--that only shows up after we start getting engineers in the modern sense. I agree that in ancient times the issue was one of vagueness, not ambiguity. I will add, at the risk of causing you a stroke, that the distinction between mass and weight exists regardless of the language being used or even if language exists at all. Should we all be struck dumb, we would not simultaneously become weightless. Quite the contrary, this problem is very much a language specific problem, one that English shares with some other languages such as French. But it doesn't have to be that way. I'll stick to my statement that depriving us of language will not render us weightless. For example, when physicists using the Norwegian language were shopping for a word to use in their jargon for the same things for which those using English use "weight," they did not choose "vekt" (various spellings such as vikt, wægt, etc. over time), which is the cognate of "weight" in English. Instead, they choose an entirely different word, "tyngde." So Norwegian doesn't have the same ambiguities that English has. You can't get a much better indication that the only science involved here is linguistics, can you? I suppose linguistics is a 'science' in the same sense as library science, political science or (shudder) computer science. And, yes, I agree that your arguments are entirely linguistic. -- FF |
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