Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ucbvax.BERKELEY.EDU Path: utzoo!watmath!clyde!burl!ulysses!ucbvax!brahms!weemba From: weemba@brahms.BERKELEY.EDU (Matthew P. Wiener) Newsgroups: net.physics,net.origins Subject: Re: Bogus physics reamplified Message-ID: <12400@ucbvax.BERKELEY.EDU> Date: Sat, 15-Mar-86 03:08:22 EST Article-I.D.: ucbvax.12400 Posted: Sat Mar 15 03:08:22 1986 Date-Received: Sat, 15-Mar-86 22:42:05 EST References: <368@ihnet.UUCP> <2057@jhunix.UUCP> <2874@sjuvax.UUCP> <446@3comvax.UUCP> <424@lanl.ARPA> Sender: usenet@ucbvax.BERKELEY.EDU Reply-To: weemba@brahms.UUCP (Matthew P. Wiener) Distribution: net Organization: University of California, Berkeley Lines: 85 Keywords: general relativity, justifying assertions, name-calling Xref: watmath net.physics:3936 net.origins:2952 Summary: The National Enquirer rides again. In article <424@lanl.ARPA> jlg@a.UUCP (Jim Giles) writes: >In article <446@3comvax.UUCP> michaelm@3comvax.UUCP (Michael McNeil) writes: >>Returning to Ken's original point, which started off this whole series >>of articles, in the above reference Bertrand Russell writes as follows: >> >> But in the modern theory the question between Copernicus and >> his predecessors is merely one of convenience; all motion >> is relative, and there is no difference between the two >> statements: `the earth rotates once a day' and `the heavens >> revolve about the earth once a day.' The two mean exactly the >> same thing, just as it means the same thing if I say a certain >> length is six feet or two yards. Astronomy is easier if we >> take the sun as fixed than if we take the earth, just as >> accounts are easier in decimal coinage. {Signet, pp. 13-14} > >Whatever Bertrand Russell's qualifications in mathematics are, no one >would ever accuse him of being a great physicist. So? BR's statements were essentially correct. The only possible point to challenge is his assertion that there is 'no difference', but that is a matter of semantics, not physics. > One of the paramount >features of General Relativity is that the laws of physics should >appear the same in ALL reference frames. The laws that are invariant are the ones in covariant form, which is essentially a circular definition. The essence of General Relativity is that space-time is a four-dimensional manifold with a Lorentzian metric, that the laws of physics hold on the manifold in an invariant way, and that local observers can put local frames on the manifold and make measurements that way. The local observers can put ANY coordinate frame they want on it, "rotating" or not. > In a reference frame which >is fixed with respect to the average motion of the nearby stars, those >stars all appear to be traveling with low (relatively) velocities. In a >'reference frame' which is fixed to the spinning Earth, the nearby stars >appear to be traveling MUCH FASTER than the speed of light. (Consider A- >Centauri: radius of 'orbit' around Earth is 4.2 light years, it 'orbits' >once per day, total distance traveled per day is 2*4.2*PI light years or >about 26 light years per day.) This is complete nonsense. The nearby stars in the rotating frame are travelling at a NUMBER which is much larger than the number obtained by measuring light in an inertial rectangular coordinate frame. The fact that the one number in the one frame is bigger than another number in another number is meaningless. Is Alpha Centauri suddenly whipping 9490 times faster than the photons it is omitting in the (apparent) direction of motion? Of course not. The fact that Alpha Centauri is seen moving slower than light in ONE frame means it moves slower than light in ALL frames. > The consequences of stars being tachyons in >one 'frame' and not being tachyons in the other would cause the observers >in the two frames to come to different conclusions about the laws of >physics in Earth local space (that is, the only way to reconcile the two >observations is to assume that there is a space-time singularity between >the two observers, but when they go to look they won't find one). It also leads to natural explanations of the Bermuda triangle, I'm sure. >The bottom line is that rotation is LOCALLY discernable and is therefore >NOT a property of Einstein's reference frames (whether they are lorentz >frames or not). One way of locally measuring rotation is with a foucault >pendulum (which you even mentioned). Meanwhile ALL Einstein frames are >LOCALLY indistinguishable from lorentz frames. The first two sentences are correct. The last one is completely wrong. Frames locally indistinguishable from Lorentz frames are called inertial. In such frames, special relativity as standardly presented is valid. SR can be done in accelerated frames, but care must be taken. But rotation can be detected more generally. For example, in a universe with just one rotating black hole, ie, a Kerr metric, the local geometry is a Kerr geometry, no matter WHERE in the universe you measure. And given enough local information (a Cauchy surface), the entire metric is determined uniquely. >For the definition of 'frame' and 'local' I suggest you read the first few >chapters of MTW ('Gravitation') again. I just did - fascinating stuff! I suggest YOU read the first few chapters again. ucbvax!brahms!weemba Matthew P Wiener/UCB Math Dept/Berkeley CA 94720