No more debate with you Thomas. How can there be a sensible debate with a person who says that the moon coalescing with the Earth is acceptable, but derides the notion of a planet without one? And to boot calls it silly.<div>Goodbye,</div><div>Tom.<br>
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----Original Message----<br>From: thomas@flyingkettle.com<br>Date: 15/11/2016 11:17<br>To: <physics@tuks.nl><br>Subj: [Physics] Clocks in relativity<br><br>On 15 Nov 2016 at 12:00, physics-request@tuks.nl wrote:<br><br>> We can dispense with the qualification "with reference to<br>> frame ??" can we not, as it it is well understood by<br>> anyone on this forum. <br><br>No, we can't, because many people misunderstand the <br>situation.<br><br>> > This behavior<br>> > is a brute fact.<br><br>> By using the phrase "this behaviour is a<br>> brute fact" do you mean it is physically real?<br><br>It depends what you mean by "physically real". Each one of <br>two moving observers, when he looks at (considered in his <br>own reference frame, of course) the clock of the other <br>observer, sees that it is running slower than his clock. <br>That is the brute fact. I don't know whether you would <br>consider that fact to be "physically real" or not; but <br>anyway, it's what is always actually observed in that <br>situation. <br><br>> Einstein himself said (and I am not going to look it up<br>> to reference it) "It does not matter what type of clock<br>> is used." <br><br>But obviously he meant, an accurate clock. If the clock is <br>bad, and its running speed fluctuates widely, nothing <br>whatever can be said about it. Of course. For example, if <br>you use your heartbeat as a clock, you will not reach any <br>physically meaningful results.<br><br>> The point I was making is that a light based clock<br>> (cesium / atomic) is not a supremely accurate clock, it<br>> is subject to errors, just the same as the pendulum<br>> clock. <br><br>Not just the same. Very much less accurate. In fact, if you <br>accept the modern SI definition of the second, which you <br>must do, the cesium clock (when perfectly implemented) has <br>no errors. The fact that two cesium clocks do not agree <br>with one another exactly, implies that at least one of them <br>is only imperfectly implemented. Probably only slightly <br>imperfectly.<br><br>I repeat, in the context of a changing gravitational field <br>(changing acceleration), a pendulum clock is a very poor <br>clock. <br><br>> Saying that the meridian passes the fixed star is bantering<br>> semantics.<br><br>No, it isn't, because rotation is absolute. The fixed stars <br>definitely do not rotate around the earth!<br><br>> The rate of the meridian clock changes by the same <br>> amount for the person at the top of the mountain and the<br>> person at the bottom, so is unnoticeable to either and<br>> they are still in the same time frame. <br><br>They are not in the same "time frame", whatever that means. <br>The clock at the bottom of the mountain will run slow as <br>compared to the clock at the top. Of course a person next <br>to the clock at the bottom will notice nothing when looking <br>at his own clock (and the same for a person at the top).<br><br>> Also we are here conducting a thought experiment, so we<br>> can find a planet without a moon, or simply assume that<br>> the moon does not exist. <br><br>Again, this is irrelevant, indeed frankly silly.<br><br>Thomas Goodey<br>****************** <br><br>But remember, please, the rules by which we live. <br>We are not built to comprehend a lie. <br>We can neither love, nor pity, nor forgive. <br>If you make a slip in handling us you die. <br><br>Rudyard Kipling, 'Secret of the Machines'<br><br><br>_______________________________________________<br>Physics mailing list<br>Physics@tuks.nl<br>http://mail.tuks.nl/cgi-bin/mailman/listinfo/physics<br><br><br>
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