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Post by abacus9900 on Mar 1, 2011 21:25:27 GMT 1
Ok, let's take the idea of gravitation.
Now, the usual analogy for beginners is to imagine a sheet of rubber with a heavy metal ball in it representing a mass, distorting space. Also, further imagine a much smaller metal ball 'orbiting' around the dip created by the much heavier one and this then may represent a gravitational attraction of a large body on a smaller one. Now, this is just an analogy and therefore not to be taken literally, however, it provides a basic framework that can be refined, if so desired, this is the point. This is something you do not seem very good at, STA. When I see documentaries on the telly (as I often do ) about some scientific subject, the 'experts' don't seem to have much of a problem getting over the basic concepts, so why can't you? You seem to assume that people want an advanced description of a subject but this is not necessarily the case. Different people require different levels of understanding, at least to begin with.
The upshot of all this is that it is pretty daft for an expert to talk to ordinary people as though they were also experts! See?
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Post by speakertoanimals on Mar 1, 2011 22:00:37 GMT 1
I think your mistake is in assuming that you can be judged to be a 'normal person' for the purposes of this experiment...................
And using the rubber-sheet analogy for relativity doesn't actually address the issue of gravitational potential and gravitational field strength. Or address the issue of the equivalence principle and WHY gravitational time dilation occurs in the way it does.
SO, in terms of time dilation, rubber-sheet is USELESS because time-dilation, by definition, involves time stretching as well as space, which makes your example useless.
Stop introducing irrelevant examples when you have got yourself stuck in a corner -- it impresses no one.
The rubber-sheet is a pretty useless analogy anyway, which is why I try to avoid using it.............................
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Post by abacus9900 on Mar 2, 2011 10:43:36 GMT 1
I think your mistake is in assuming that you can be judged to be a 'normal person' for the purposes of this experiment................... And using the rubber-sheet analogy for relativity doesn't actually address the issue of gravitational potential and gravitational field strength. Or address the issue of the equivalence principle and WHY gravitational time dilation occurs in the way it does. SO, in terms of time dilation, rubber-sheet is USELESS because time-dilation, by definition, involves time stretching as well as space, which makes your example useless. Stop introducing irrelevant examples when you have got yourself stuck in a corner -- it impresses no one. The rubber-sheet is a pretty useless analogy anyway, which is why I try to avoid using it............................. How on earth can you expect people to understand what gravitational potential and gravitational field strength is before they have a fundamental idea of what gravitation is? You keep putting the 'cart before the horse', trying to make people 'run before they can walk', not allowing the 'dog to see the rabbit' and any other analogies one may care to think of. Would you seriously expect high school students to tackle calculus before they had a good grasp of arithmetic, algebra, functions, and so on? Course not, and the point is in studying each aspect of a subject it has to be treated separately at first and then and only then developed to incorporate more sophisticated concepts. Even our most advanced scientific ideas are probably wrong in the sense that they are incomplete, so come off it STA, this is how knowledge progresses - by stages. This is what you keep getting wrong. You try to present knowledge in one big dollop, so much so that it is indigestible to people and simply turns them off. If you were to teach a foreign language to a beginner's class how would you do it? By trying to make them understand advanced biology? No, you would not. So stop being a silly girl and start behaving like a grown woman, ok? 'Nough said.
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Post by speakertoanimals on Mar 2, 2011 13:17:24 GMT 1
Except you don't NEED curved space and general relativity to understand gravitational field strengths (weight), and gravitational potential energy -- the energy that is converted to kinetic energy when I drop a stone.
Easy, job done, and something I've already explained, as you well know............
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Post by abacus9900 on Mar 2, 2011 13:24:15 GMT 1
So let me get this straight.
To understand gravitational field strength and gravitational potential energy you don't need to know about gravity?
This is just banal now to suggest that you can study something completely out of context. Is this a wind up, or are you serious?
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Post by speakertoanimals on Mar 2, 2011 13:38:59 GMT 1
You don't need to know about General Relativity to understand what they mean, do keep up and stop pretending to be even more stupid than you actually are, because not even you could be that dim (although you seem to be having a damn good try!)
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Post by abacus9900 on Mar 2, 2011 14:46:27 GMT 1
You don't need to know about General Relativity to understand what they mean, do keep up and stop pretending to be even more stupid than you actually are, because not even you could be that dim (although you seem to be having a damn good try!) I think you know I'm right which is why you are being so spiteful.
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Post by speakertoanimals on Mar 2, 2011 17:35:52 GMT 1
Not spiteful, just truthful.
Why do you seem to be more intersted in continually having a go at me, than actually trying to learn any physics? Because so far, you seem to find the simple concepts of weight and gravitational potential energy an insurmountable hurdle.....................
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Post by abacus9900 on Mar 2, 2011 18:08:13 GMT 1
Not spiteful, just truthful. Why do you seem to be more intersted in continually having a go at me, than actually trying to learn any physics? Because so far, you seem to find the simple concepts of weight and gravitational potential energy an insurmountable hurdle..................... STA, I'm sorry, but you have not yet managed to explain what gravitational potential energy is in any clear way to me. I'm not having a go at you and you are probably doing your best but you will have to dumb down your explanations before anyone of average intelligence can understand them.
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Post by Progenitor A on Mar 2, 2011 18:39:50 GMT 1
Not spiteful, just truthful. Why do you seem to be more intersted in continually having a go at me, than actually trying to learn any physics? Because so far, you seem to find the simple concepts of weight and gravitational potential energy an insurmountable hurdle..................... STA, I'm sorry, but you have not yet managed to explain what gravitational potential energy is in any clear way to me. I'm not having a go at you and you are probably doing your best but you will have to dumb down your explanations before anyone of average intelligence can understand them. Gravitational potential and gravitational force are simply alternative ways of measuring the same thing - a gravitational field There is nothing mumbo-jumbo about it - STA simply obfuscates things in her inimitable fashion; how invaluable it is in a lecturere to make simple things complex!
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Post by speakertoanimals on Mar 2, 2011 18:52:57 GMT 1
WRONG!
As I said before, take an analogy -- the shape of a hillside. The elevation of a point is like gravitational potential energy. The maximum slope at a point is like gravitational field strength.
Knowing your elevation at a point DOESN'T tell you which way you will roll, doesn't tell you about the shape of the hill locally. FOr that, you need the slope at that point.
If you know the elevation across a region, you can compute the slope, and if you know the slope over a region, you can work out the elevation (up to a constant). But at a POINT, knowing one doesn't tell you the other.
There is an important distinction, because as on a hill, youn can have HIGH gravitational potential/HIGH elevation, but the local landscape can still be flat as a pancake (ZERO gravitational field strength). Ditto, you can be near the bottom of a deep valley (LOW elevation, LOW gravitational potential), but still have a whacking big slope.
So, what effects time dilation, the slope or the elevation? Turns out it is elevation that does it, NOT field strength/slope.
If you think the difference is unimportant, explains why so many people get the basics of gravitational time dilation utterly wrong, which was the supposed topic of this thread...............
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Post by Progenitor A on Mar 2, 2011 19:09:57 GMT 1
Hi Abacus
Here she goes again on her mad ambition to make complex the simple
There is a something that we call gravitational field.
A Gravitational field can be measured in 2 ways
1 Gravitational potential 2. Gravitational force
Naturally, because they are alternative ways of measuring the same thing, one can be derived from the other
Dr Tong (thank goodnes that some clever people can explicate the simple as the simple!) explains that Gravitational force is the derivative of Gravitational potential (and Gravitational potential is the integral of the gravitational force)
Simple Two alternative ways of measuring gravitational field
You will find that this mad woman contradicts herslf frequently on this point ;D
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Post by abacus9900 on Mar 2, 2011 19:46:03 GMT 1
Ok, I 'get' what you mean but may I ask you to explain, in as simple terms as possible for the hard of thinking, what these two concepts are about? STA began in a promising way but then started get too wordy and to sound like a physicist! No maths please.
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Post by Progenitor A on Mar 2, 2011 20:20:09 GMT 1
Ok, I 'get' what you mean but may I ask you to explain, in as simple terms as possible for the hard of thinking, what these two concepts are about? STA began in a promising way but then started get too wordy and to sound like a physicist! No maths please. There is this 'thing' a property of mass that has certain effects. No-one knows why mass should have this effect, but it does. (Just another big hole in our 'knowledge') But, although we do not know why mass has this effect, we can neverthelss measure the effect (That is pretty obvious really as if we cannot measure things then they do not exist -or do they?) So we set about measuring this thingBut before we meaure it we had better give it a name So we call it a field - a gravitational field (just like the nice Mr Tong does) We know (because Newton told us so) that this gravitational field gives us the effect of weightWeight is simply the effect of one mass pulling on another We call that pull gravitational forceWe can measure that force exerted by the gravitational field (just as Newton described F=ma) Fine - we have measured Force. The stronger the gravitational field then the bigger the force exerted on another mass. We can also measure the gravitational potential. That tells us that we must do some work to get a mass into a certain position in a gravitational field The stronger the gravitational field then the more work we must do to move the mass that same distance as in the weaker gravitational field! So Gravitaional force, depends on the intensity (or strength) of the gravitational field And Gravitational potential also depends upon the intensity (or strength) of the gravitational field So you can see that gravitational force and gravitational potential are related and are simply alternative ways of measuring the same thing - the thing that is being measured is the gravitational field (that something which we do not really know what it is!)! Now; as we are simply using alternative ways of measuring the same thing then we should be able to fiind out the one thing if we know the other; And that is so For Gravitational Force = d(gravitational potential)/ds and Gravitational potential =(Integral)Gravitational Force (ds) + k Simple really? (I think I have explained it correctly!) ;D
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Post by speakertoanimals on Mar 2, 2011 20:26:37 GMT 1
What part of derivative is suposedly simpler than my description using SLOPE.......................
Stop pretending! And stop repeating yourself, we've been through ALL this before, and it just reduces to the usual rant -- everything I say is crap, everything everyone else says is clear as crystal.
Nope, it IS the strength of the gravitational field (despite your earlier claims that the potential could measure the strength, you could at least try and be consistent in your ramblings).
I've got better things to do than talk to sock-puppets.............
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