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 Tags einstein , gps , gravity , McCoin , relativity , special relativity , time dilation

 28th April 2009, 01:31 AM #121 Thabiguy Muse   Join Date: Feb 2007 Posts: 783 Originally Posted by MacM Show my calculations in error and I'll shut up. Is that a fair offer? Okey dokey. Let's see if you're a man of your word. Originally Posted by MacM GPS satellites have a velocity (V1) of 3,874.5 m/s. A surface clock (at the equator) has an absolute velocity (V2) of 463.8 m/s and "0" m/s at the poles (or earth's center). The "Relative Velocity" between the orbiting clock and a clock at the equator is V3 = (V1 - V2) = (3,874.5m/s - 463.8m/s) = 3,410.7m/s. I bolded the error for you. The relative velocity between the orbiting clock and a clock at the equator is not equal to the difference between the magnitude of the two velocities. This is because velocity is a vector, and so in order to find the relative velocity between two moving objects, you need to do vector subtraction, not scalar subtraction. - This is not even SR, this is plain Newtonian mechanics. In other words (in case you're unfamiliar with vectors), the relative velocity doesn't just depend on how fast the two objects are moving, but also in what direction they're moving. If they're moving in the same direction, you need to subtract the velocities. If they're moving in the opposite direction, you need to add the velocities. If they're moving at an angle, you need to do vector subtraction to get the correct result. Calculating the relative speed as (3,874.5 m/s - 463.8 m/s) = 3,410.7 m/s implies that the satellite and the surface clock are moving in the same direction. But that will practically never be true; they will almost always move in different directions, therefore having a relative speed higher than 3,410.7 m/s. In fact, they will just as frequently move in approximately opposite directions as in approximately same directions, yielding relative speed up to 3,874.5 m/s + 463.8 m/s = 4,338.3 m/s. Because the relative velocity you have calculated (3,410.7 m/s) is wrong (too low), your subsequent calculation of time dilation of 5.58 microseconds per day is also wrong (too low). Specifically, 5.58 is not the result which SR gives, it's an erroneous result that you have arrived to, due to your failure to properly subtract velocities.
 28th April 2009, 03:47 AM #122 nathan Zygoticly Phased     Join Date: Nov 2004 Location: Arkham City Posts: 3,182 Originally Posted by Thabiguy In fact, they will just as frequently move in approximately opposite directions as in approximately same directions Is that true? IIUC satellites (not just GPS ones) orbit in the same direction as Earth's rotation. That just makes sense when launching them -- you need to give them a particular orbital velocity +/-Ws, and it's cheaper to add to Earth's rotation We to reach +Ws than subtract from it to reach -Ws. GPS satellites have orbits inclined to the equator, but the equatorial component of the orbit is always going to be west to east, and be the dominant velocity in the satellite/detector system. Isn't it? I return to __________________ Crank works have one advantage: they don't really lose anything in translation. Skeptic That's the beauty of Paranormal claims - there are no failures, only newly discovered restrictions on the ability. Ashles
 28th April 2009, 04:01 AM #123 ArmillarySphere Muse     Join Date: Jul 2006 Location: London Posts: 713 Well. Seems there are a number of misconceptions here: 1. The friend travelling by car with a slow clock. Surprise, surprise, if the clock runs at a slower speed but the odometer is fine, you will get a higher value for the speed than an observer at rest. However, this is not analogous to an SR scenario - in that case, the odometer would also measure half the distance of the observer at rest. So both will agree on how fast the car was moving, but will disagree on 1) how long it took to drive, 2) the distance driven and 3) the time of arrival, assuming they agreed on when the drive started. Exactly the scenario for SR. 2. The twin non-paradox. Because really, what's the hangup? The amount of time dilation does not depend on acceleration in any way whatsoever, but does depend on the relative speed of the reference frames and how long is spent in each one. You can design the twin scenario so that no acceleration is involved from start to finish, by the way - have the twins start out already in motion when they synchronise clocks, and then introduce a third traveller who will meet and synchronise time with one of the twins and then rendezvous with the other, all without changing velocity. The acceleration is zero throughout, yet SR predicts that the third traveller's clock will lag behind the second one he meets, regardless of which one accelerated initially. There is no paradox.
 28th April 2009, 04:04 AM #124 Thabiguy Muse   Join Date: Feb 2007 Posts: 783 Originally Posted by nathan Is that true? IIUC satellites (not just GPS ones) orbit in the same direction as Earth's rotation. That just makes sense when launching them -- you need to give them a particular orbital velocity +/-Ws, and it's cheaper to add to Earth's rotation We to reach +Ws than subtract from it to reach -Ws. What happens when you successfully launch a satellite and it makes it through half its orbit? Originally Posted by nathan GPS satellites have orbits inclined to the equator, but the equatorial component of the orbit is always going to be west to east, and be the dominant velocity in the satellite/detector system. Isn't it? West to east in the US is opposite to west to east in China. Last edited by Thabiguy; 28th April 2009 at 04:13 AM.
 28th April 2009, 04:41 AM #125 nathan Zygoticly Phased     Join Date: Nov 2004 Location: Arkham City Posts: 3,182 Originally Posted by Thabiguy What happens when you successfully launch a satellite and it makes it through half its orbit? Ah, I realized that, but forgot to mention why I thought it immaterial to GPS. There's the rather obvious problem of a big rock in the way blocking the photons. The GPS calculations only have to work for satelites above the horizon. __________________ Crank works have one advantage: they don't really lose anything in translation. Skeptic That's the beauty of Paranormal claims - there are no failures, only newly discovered restrictions on the ability. Ashles
 28th April 2009, 04:57 AM #127 sol invictus Philosopher     Join Date: Oct 2007 Location: Nova Roma Posts: 8,435 Originally Posted by MacM Show my calculations in error and I'll shut up. Is that a fair offer? Yes. Quote: Were you one that asserted GPS used SR? Hmmm. I seem to remember posting how GPS actually worked and demonstrated how the application of SR was wrong. You are doing some fuzzy math here. Get on track. You said some wrong things. GPS of course does "use SR". You have a very basic misconception about what SR is. Essentially, SR is the claim that all the laws of physics are invariant under Lorentz transformations. Time dilation, Lorentz contraction etc. are all consequences of that claim. GR, and the relativistic field theories used to describe particle physics, are examples of such Lorentz invariant theories. Every time we use them or test them, we are using and testing SR, because SR is intrinsic to them. So if you use GR to calculate something, you're using SR (just like you're also using multiplication and addition). Quote: I have said relativity is useful and highly precise when properly applied but my point is it is an invalid physical theory. See above - you don't seem know what it even is. It's not really a theory - it's a symmetry, or a class of theories. Quote: Go ahead dispute that the apparent accelerating expansion of the universe must be a deceleration IF you accept relativity. Go ahead. I'm the dummy (according to you and others here) show me how dumb I am by properly showing the falicy of my claim. Very well, I dispute it. It's wrong. Here's a relativistic theory in which the universe's expansion accelerates: positive cosmological constant. You're wrong (and I can prove it mathematically if you'd like). So now will you live up to your end of the bargain and "shut up"? Last edited by sol invictus; 28th April 2009 at 04:59 AM.
 28th April 2009, 05:01 AM #128 sol invictus Philosopher     Join Date: Oct 2007 Location: Nova Roma Posts: 8,435 Originally Posted by MacM Show my calculations in error and I'll shut up. Is that a fair offer? Yes. Quote: Were you one that asserted GPS used SR? Hmmm. I seem to remember posting how GPS actually worked and demonstrated how the application of SR was wrong. You are doing some fuzzy math here. Get on track. You said many wrong things. GPS of course does "use SR". You have a very basic misconception about what SR is. Essentially, SR is the claim that all the laws of physics are invariant under Lorentz transformations. Time dilation, Lorentz contraction etc. are all consequences of that. GR, and the relativistic field theories used to describe particle physics, are examples of such Lorentz invariant theories. So if you use GR to calculate something, you're using SR (just like you're also using multiplication and addition). Quote: I have said relativity is useful and highly precise when properly applied but my point is it is an invalid physical theory. See above - you don't seem know what it is. SR is not really a theory. It's a symmetry. It's a big class of theories. It's a general claim about the world. Quote: Go ahead dispute that the apparent accelerating expansion of the universe must be a deceleration IF you accept relativity. Go ahead. I'm the dummy (according to you and others here) show me how dumb I am by properly showing the falicy of my claim. Very well, I dispute it. It's wrong. Here's a relativistic theory in which the universe's expansion accelerates: de Sitter space at late time. You're wrong (and I can prove it mathematically if you'd like). So now will you live up to your end of the bargain and "shut up"?
 28th April 2009, 05:03 AM #129 Dancing David Penultimate Amazing     Join Date: Mar 2003 Location: Central Illinois Posts: 34,931 MacM, I note a common misconception here in your post and it is a very common one about the nature of science and reality: Quote: Unfortunately yours is a very typical attitude. You don't care about the physical reality but only that relativity has mathematical utility. I don't dispute it's value or utility. I do dispute it physical correctness and believe that the far to common attitude limits our ability to make progress to greater understanding hence discoveries. Now this is a rather common mistake (from my POV) All human thoughts, ideas, words and theories are abstracted metaphors, they are semantic idiomatic and self referencing, they are maps that approximate the terrain of experience and observation. All human thoughts, ideas, words and theories are equally true and equally false. They only have meaning through the application of self reference, all of them are approximate placeholders used to make use of common reference. None of them are true in and of them selves. The concept of 'tree' only has meaning in reference to an idiomatic and self referencing set of communications between people. The term 'tree' has no validity in and of itself, it is never absolute, a 'yew' might be a 'tree' or a 'shrub', but a 'japanese split leaf maple' is always a 'tree' although it is often smaller than a 'shrub'. So when it comes to theories, none of them are real, just as words are never real. they only are approximate models of reality. the utility comes in the ability to approximate reality and model it. Further demonstration, 'matter' is mostly empty space, it is not 'solid' (it is made non-penetrable by the repulsion of electrons. But the word electron is what? A model, you can not say that 'electrons' have a physical reality, they are just a word reference and short hand for a bunch of math and thought models. __________________ Hell, dynamiting fish in a barrel is more challenging. - Ladewig I suspect you are a sandwich, metaphorically speaking. -Donn And a shot rang out. Now Space is doing time... -Ben Burch You built the toilet - don't complain when people crap in it. _Kid Eager
 28th April 2009, 06:42 AM #131 MacM Muse   Join Date: Apr 2009 Posts: 683 Originally Posted by MattusMaximus MacM, for you to flatly state that time dilation due to SR isn't real is pretty laughable to me. I have observed it for myself. In fact, I have my high school AP physics students do a lab on this very thing every year... Ever hear of the famous muon time dilation experiment? Why is it that educated people can be so hard headed and refuse to see the forest for the trees. I clearly have stated that muon time dilation is real but you ignore that it has been found that muon ansitrophy in their velocity relative to earth is a valid basis to calculate our motion in the universe at large i.e. - let me clarify "Demonstrates muon velocity has an absolute motion component" and that time dilation is not just relative to the observer, otherwise you would be required to demonstate the reciprocity mandated by the relative velocity view of Einstien's SR. The elimination of reciprocity by declaring who has velocity removes the "Relative Velocity" component of the theory. You and most others still srongfully assert that relative velocity causes time dilation. You operate in a void of emperical data to support that assertion.
 28th April 2009, 06:48 AM #132 D'rok Free Barbarian on The Land     Join Date: Dec 2006 Posts: 6,250 Originally Posted by MacM You and most others still srongfully assert that relative velocity causes time dilation. You operate in a void of emperical data to support that assertion. See post #126. __________________ "War exists within the continuum of politics, in which play is continuous, and no outcome is final, save for a global thermonuclear war, which might be." - Darth Rotor "Life, like a Saturday afternoon, finds its ruination in purpose." - MdC
 28th April 2009, 07:03 AM #134 dahduh Critical Thinker     Join Date: May 2006 Location: Cape Town Posts: 360 Originally Posted by MacM Why is it that educated people can be so hard headed and refuse to see the forest for the trees. MacM, perhaps you should look up the Dunning-Kruger effect.
 28th April 2009, 07:09 AM #135 drkitten Penultimate Amazing   Join Date: Mar 2004 Location: Wits' End Posts: 21,647 Originally Posted by MacM Ah. We are not completely in disagreement. The gibberish part is because you apparently are unfamiliar with the Taylor series Actually, I have taught Taylor series. I'm not sure how the gibberish can be because I'm unfamiliar with a part of my professional specialization that you didn't put in the post at all. I stand by my statement. Your math is gibberish. I further submit that YOU are unfamiliar with Taylor series.
 28th April 2009, 07:11 AM #136 drkitten Penultimate Amazing   Join Date: Mar 2004 Location: Wits' End Posts: 21,647 never mind.
 28th April 2009, 07:12 AM #137 drkitten Penultimate Amazing   Join Date: Mar 2004 Location: Wits' End Posts: 21,647 Originally Posted by nathan Ah, I realized that, but forgot to mention why I thought it immaterial to GPS. There's the rather obvious problem of a big rock in the way blocking the photons. The GPS calculations only have to work for satelites above the horizon. The clock still ticks even when the satellite is under the horizon.
 28th April 2009, 08:08 AM #138 dasmiller Just the right amount of cowbell     Join Date: Oct 2008 Location: Well past Hither, looking for Yon Posts: 3,504 Sheesh, doesn't anyone here sleep? Anyway- Originally Posted by MacM I'm not sure we are communicating here. I gave Two process in my GPS disertation. I specifically pointed out the one trying to apply an SR type relative velocity between clocks yields an incorrect value of -5.58 usec/day due to velocity compensation. The actual net adjustment is about 38usec/day including GR and LR (not SR). But I also gave the correct result using the actual process GPS uses which involves the ECI reference frame. So why are you affixed to the incorrect calculation.? I believe that your example misrepresents how SR would be calculated by the "relativists." Evidently you agree: Originally Posted by MacM Now I'll now say much beyond just correcting the record here but only to note the arguements against using the SR form of mathematics of V2 - V1 where V2 is orbit velocity to the ECI and V1 is clock surface velocity to the ECI, is not well supported but I choose to not argue the issue of inertial condition and that it would disprove SR because I do agree that vector is an important component part of such calculation. Any conclusion you draw from this misrepresentation is necessarily flawed. Originally Posted by MacM Can we move on? If you stop saying that your example proves that GPS doesn't validate SR, then yes. __________________ "In times of war, we need warriors. But this isn't a war." - Phil Plaitt
 28th April 2009, 08:20 AM #139 nathan Zygoticly Phased     Join Date: Nov 2004 Location: Arkham City Posts: 3,182 Originally Posted by drkitten The clock still ticks even when the satellite is under the horizon. of course it does. __________________ Crank works have one advantage: they don't really lose anything in translation. Skeptic That's the beauty of Paranormal claims - there are no failures, only newly discovered restrictions on the ability. Ashles
 28th April 2009, 08:21 AM #140 dasmiller Just the right amount of cowbell     Join Date: Oct 2008 Location: Well past Hither, looking for Yon Posts: 3,504 Originally Posted by MacM No I'm saying GPS uses over a dozen computations but the ONE that involves orbit velocity is based on the ECI frame which is a common locally preferred rest frame for both the orbiting clocks and surface clocks. Are you really so familiar with the GPS CS Kalman filter that you know how the coordinate systems are represented internally? __________________ "In times of war, we need warriors. But this isn't a war." - Phil Plaitt
 28th April 2009, 09:07 AM #141 Thabiguy Muse   Join Date: Feb 2007 Posts: 783 Originally Posted by nathan Ah, I realized that, but forgot to mention why I thought it immaterial to GPS. There's the rather obvious problem of a big rock in the way blocking the photons. The GPS calculations only have to work for satelites above the horizon. No. That's not how GPS works. Time dilation is not compensated for with respect to those observers that see the satellites above the horizon. First, it would not be possible, because the satellites are simultaneously visible by many observers with quite different relative velocities, so no matter what you did, someone would always see the GPS clock ticking at an incorrect rate. But there is a more fundamental reason why GPS clocks can't be set to tick at - even approximately - correct rate with respect to those who see them overhead. The reason is that the atomic clocks in GPS are not there just to measure time intervals during the period you see them above the horizon. The clocks have to keep precise time. They need to be able to tell with great precision what the current time is. And that is in order to tell where exactly they're located at any given moment - in order to allow you to tell where you're located. If you set the clocks to tick at the correct rate when they're passing over your head, they would not be able to keep correct time, because they would inevitably tick incorrectly whenever they drop below the horizon, and the next time they pass over your head, the clock would be off. So what is done is that the GPS time is defined in an inertial system, and corrections are then done to account for distortions due to Earth-based observations. The role that time dilation plays in the accuracy of GPS is that it needs to be accounted for to maintain the time kept by the clocks accurate in the long run, orbit after orbit after orbit. The relative velocity of the satellite when it passes overhead is quite irrelevant to this. If you want to calculate by how much the clock drifts in a day, the whole orbit matters. Last edited by Thabiguy; 28th April 2009 at 09:17 AM.
 28th April 2009, 09:17 AM #142 theprestige Philosopher   Join Date: Aug 2007 Posts: 8,905 Originally Posted by MacM I have said no such thing. Oh, but you have. In your very first post on this thread, no less. Shall I quote it again? Yes. Yes I shall: Originally Posted by MacM ... we are dealing with some form of universal absolute velocity change relative to the other observer. See that bit right there? That bit about an "absolute velocity change relative to the other observer"? The terms "absolute" and "relative" are mutually contradictory. This is, what, the fourth time I've brought this up in one form or another? It's the third time I've stated this was a problem for your claims. And it's now the second time I've told you that it needs to be resolved before you can arrive at a correct conclusion.
 28th April 2009, 09:20 AM #143 ben m Illuminator   Join Date: Jul 2006 Posts: 4,714 Originally Posted by MacM it has been found that muon ansitrophy in their velocity relative to earth is a valid basis to calculate our motion in the universe at large i.e. - let me clarify "Demonstrates muon velocity has an absolute motion component" That's not true. It has not "been found that muon ansitrophy in their velocity relative to earth is a valid basis to calculate our motion in the universe at large". Either you just made that up, or you calculated it incorrectly, or you're citing an incorrect source. If you disagree cite your sources.
 28th April 2009, 09:25 AM #145 Belz... Fiend God     Join Date: Oct 2005 Location: In the details... Posts: 28,980 Originally Posted by MacM Hello Ben, Thanks for your comments. It is a fudge factor in that relativists still want to claim mere relative velocity causes relavistic changes. Clearly relative velocity doesnot and cannot do anything in terms of physical change. And yet it does. In a battle against reality, you are bound to lose. __________________ The Onmyouza Theatre, An unofficial international fanclub forum dedicated to the Japanese heavy metal band Onmyo-Za. "In the interests of time and space, it is not unreasonable to cite one point at a time. Citing 30 is the equivalent of citing none. Obviously." - Robert Prey
 28th April 2009, 09:29 AM #146 nathan Zygoticly Phased     Join Date: Nov 2004 Location: Arkham City Posts: 3,182 Originally Posted by Thabiguy No. That's not how GPS works. Time dilation is not compensated for with respect to those observers that see the satellites above the horizon. First, it would not be possible, because the satellites are simultaneously visible by many observers with quite different relative velocities, so no matter what you did, someone would always see the GPS clock ticking at an incorrect rate. But there is a more fundamental reason why GPS clocks can't be set to tick at - even approximately - correct rate with respect to those who see them overhead. The reason is that the atomic clocks in GPS are not there just to measure time intervals during the period you see them above the horizon. The clocks have to keep precise time. They need to be able to tell with great precision what the current time is. And that is in order to tell where exactly they're located at any given moment - in order to allow you to tell where you're located. If you set the clocks to tick at the correct rate when they're passing over your head, they would not be able to keep correct time, because they would inevitably tick incorrectly whenever they drop below the horizon, and the next time they pass over your head, the clock would be off. So what is done is that the GPS time is defined in an inertial system, and corrections are then done to account for distortions due to Earth-based observations. The role that time dilation plays in the accuracy of GPS is that it needs to be accounted for to maintain the time kept by the clocks accurate in the long run, orbit after orbit after orbit. The relative velocity of the satellite when it passes overhead is quite irrelevant to this. If you want to calculate by how much the clock drifts in a day, the whole orbit matters. Hm, I thought that the receiver applied relativistic calculations using ephemerides transmitted by the satellites themselves on the timing data that is being received. Someone upthread mentioned there are a set of 6 classical parameters and a set of 3 relativistic ones. Is that not the case? From that it can determine satellites' locations and then determine the distance it is from them, and then determine it's own position by triangulation. Are you describing the calculation done to determine the ephemerides? __________________ Crank works have one advantage: they don't really lose anything in translation. Skeptic That's the beauty of Paranormal claims - there are no failures, only newly discovered restrictions on the ability. Ashles
 28th April 2009, 09:33 AM #147 Thabiguy Muse   Join Date: Feb 2007 Posts: 783 Originally Posted by nathan Hm, I thought that the receiver applied relativistic calculations using ephemerides transmitted by the satellites themselves on the timing data that is being received. In order to transform ephemerides into a location, you need time. Not interval between two events. Current time.
 28th April 2009, 09:37 AM #148 nathan Zygoticly Phased     Join Date: Nov 2004 Location: Arkham City Posts: 3,182 Originally Posted by Thabiguy In order to transform ephemerides into a location, you need time. Not interval between two events. Current time. yes. still not understanding your point. __________________ Crank works have one advantage: they don't really lose anything in translation. Skeptic That's the beauty of Paranormal claims - there are no failures, only newly discovered restrictions on the ability. Ashles
 28th April 2009, 09:37 AM #149 Belz... Fiend God     Join Date: Oct 2005 Location: In the details... Posts: 28,980 Originally Posted by MacM Wholly crap. An actual intelligent member here. Translation: "Holy crap! Someone who agrees with me!" Quote: common sense Woo talk. I knew this would come up, eventually. Quote: Not required That's another thing I expected. Quote: Another JREF member's credability bites the dust. So shut up and listen now. You have made it clear I am more knowledgeable about this than yourself. Why do some people insist that the whole world is wrong ? It's the Galileo complex, all over again. Quote: SR is not used in GPS. Do you every get something right ? __________________ The Onmyouza Theatre, An unofficial international fanclub forum dedicated to the Japanese heavy metal band Onmyo-Za. "In the interests of time and space, it is not unreasonable to cite one point at a time. Citing 30 is the equivalent of citing none. Obviously." - Robert Prey
 28th April 2009, 09:43 AM #150 drkitten Penultimate Amazing   Join Date: Mar 2004 Location: Wits' End Posts: 21,647 Originally Posted by nathan yes. still not understanding your point. The clocks in orbit need to know what time a ground based observer thinks it is in order to transmit the proper data to them. Which means the satellites need to know "proper time" in the ground-based frame. So their clocks are tweaked to run slowly (or so that they would run slowly if they were on the ground) so the time signals they send are synched with what the ground-based clocks expect.
 28th April 2009, 09:49 AM #151 dasmiller Just the right amount of cowbell     Join Date: Oct 2008 Location: Well past Hither, looking for Yon Posts: 3,504 Originally Posted by nathan Someone upthread mentioned there are a set of 6 classical parameters and a set of 3 relativistic ones. Is that not the case? The other 3 terms aren't generally considered relativistic AFAIK. They're used to to correct for the perturbations caused by the moon, sun, Jupiter, Earth's actual shape, solar wind, etc. There are so many things that impact the GPS orbit (or any other orbit) and so little space in the GPS downlink datastream that it's really not possible to downlink the zillion correction terms you'd need to fully represent the orbit. And, for that matter, some of the terms aren't known that well (you should see all the papers on GPS solar pressure models), and there's not much point in downlinking a zillion little tiny correction terms when you're fuzzy on the big corrections. But by adding 3 more terms, they can give a much more accurate representation than they get from just the 6 Keplerian elements. __________________ "In times of war, we need warriors. But this isn't a war." - Phil Plaitt Last edited by dasmiller; 28th April 2009 at 09:51 AM.
 28th April 2009, 10:05 AM #152 Thabiguy Muse   Join Date: Feb 2007 Posts: 783 Originally Posted by nathan yes. still not understanding your point. My point is, as I said already, that the atomic clocks in GPS are not synchronized to tick at a "correct" rate with respect to an observer that sees them overhead. They are instead synchronized to keep accurate time over extended periods of time (many orbits). This is because they need to be able to tell the current time according to some standard, rather than just measure time interval between two events. For this reason, your earlier assumption that Quote: The GPS calculations only have to work for satelites above the horizon. is incorrect. For the purpose of accurately keeping time (which is essential to GPS operation), time dilation over the whole orbit matters, not just the part when the satellite is above the horizon. What do you still not understand?
 28th April 2009, 11:17 AM #153 Pantaz Muse     Join Date: Feb 2008 Location: Van Nuys, CA Posts: 906 Originally Posted by Thabiguy West to east in the US is opposite to west to east in China. Huh?
 28th April 2009, 11:22 AM #154 Thabiguy Muse   Join Date: Feb 2007 Posts: 783 Originally Posted by Pantaz Huh? Get a globe and try it.
 28th April 2009, 11:36 AM #155 Dorfl Muse   Join Date: Jun 2005 Location: Sweden Posts: 523 Originally Posted by Thabiguy Get a globe and try it. I too was confused at first, since China tends to be used as the proverbial place on the other side of the Earth here as well, as in "dig a hole to China" or "run away to China". But checking a globe it turns out to be only about 90 degrees off from Sweden, and about opposite to USA. Figures of speech are wierd. Last edited by Dorfl; 28th April 2009 at 11:55 AM. Reason: 90°, not 45°
 28th April 2009, 11:37 AM #156 Molinaro Illuminator     Join Date: Dec 2005 Location: Toronto Posts: 3,053 Originally Posted by Pantaz Huh? I think you need to read it as: The vector representing W to E in NA is opposite in direction to the vector representing W to E in China. Picture the direction the vectors would be pointing, not along the surface of the globe, but as a vector suspended in empty space. __________________ 100% Cannuck!
 28th April 2009, 11:43 AM #157 Skwinty Illuminator     Join Date: Jun 2008 Location: The far side Posts: 4,972 Originally Posted by Dorfl I too was confused at first, since China tends to be used as the proverbial place on the other side of the Earth here as well, as in "dig a hole to China" or "run away to China". But checking a globe it turns out to be only about 45 degrees off from Sweden, and about opposite to USA. Figures of speech are wierd. Stand in front of a mirror and raise your left hand. Now imagine the mirror image was actually some one else looking at you. they would have their right hand raised. __________________ What is reality? Nothing but a collective hunch. --Lily Tomlin
 28th April 2009, 11:44 AM #158 Pantaz Muse     Join Date: Feb 2008 Location: Van Nuys, CA Posts: 906 Originally Posted by Molinaro I think you need to read it as: The vector representing W to E in NA is opposite in direction to the vector representing W to E in China. Picture the direction the vectors would be pointing, not along the surface of the globe, but as a vector suspended in empty space. Ah! Thank you!
 28th April 2009, 11:54 AM #159 Dorfl Muse   Join Date: Jun 2005 Location: Sweden Posts: 523 Originally Posted by Skwinty Stand in front of a mirror and raise your left hand. Now imagine the mirror image was actually some one else looking at you. they would have their right hand raised. What I hadn't figured out is that the US and China are in fact on opposite sides of the Earth. I had pictured them as being more like 90-135° apart, since we tend to speak of China as though it were 180° away from Sweden, which in turn is quite far from America.
 28th April 2009, 12:09 PM #160 jsfisher ETcorngods survivor     Join Date: Dec 2005 Posts: 11,624 Originally Posted by MacM FYI: To those that might actually care here is a link to GR: http://books.google.com/books?id=-8P...esult&resnum=3 Which states on page 223: Astronauts in a spaceship orbiting the Earth are in free-fall...." Yep, this is true. Quote: On page 224 states: The Einstein form of the principle of equivelence states that inertial and free-falling systems are entirely equivelent." Well, ignoring the misspellings, this is also correct. Gravitational systems and inertial systems are equivalent according to Einstein and GR. But the original point was about inertial frames of reference. Why did you bring up this other stuff? __________________ As long as Comparison is sunk in the urine of one's mind, new glasses will not help. --Doronshadmi. A proud member of the Simpson 15+7, named in the suit, Simpson v. Zwinge, et al., and founder of the ET Corn Gods Survivors Group. By the way, the Nominate button is to your right left, sort of..

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