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Natural Science Forum / Physics / Relativity / December 2007Animation illustrating time dilation in satellites
This is an applet illustrating time dilation in bodies moving in the vicinity of the Earth. http://home.c2i.net/pb_andersen/Satellites.html Good ol' Newton is used to determine the motion of the bodies, while the Schwarzschild metric is used to determine their proper times. A short comment to the scenarios in the applet: Two ballistic rockets: ---------------------- Illustrates that two inertial bodies may experience different proper times between the same two events. (And the non inertial ground clock yet another.) Geostationary + GPS: -------------------- Illustrates the time dilation in said satellites (Both are 'running faster' than the ground clock) ISS and zero time diff. orbit: ------------------------------ Clocks in the International Space Station are running slow, while clocks in a satellite in circular orbit at just the right altitude are running at the same rate as the ground clock. Rockets in opposite directions ------------------------------ Illustrates that the orbits of two rockets launched at exactly the same way, but in opposite directions, will be different. Two zero time diff. orbits: ----------------------------- Even clocks in elliptical orbit may - on average - run at the same rate as a ground clock. Twin scenario - kind of: ------------------------ Two twins meeting regularly comparing clocks are ageing differently. Missing a scenario? Give me a hint, and I may add it.  SignaturePaul http://home.c2i.net/pb_andersen/ : This is an applet illustrating time dilation in bodies moving : in the vicinity of the Earth. [quoted text clipped - 4 lines] : Two twins meeting regularly comparing clocks : are ageing differently. How come the twins meet at the same place at the same time? : Missing a scenario? : Give me a hint, and I may add it. Yeah, satellites going in opposite directions, same altitude. I wanna see the time dilation of one from the other, never mind the ground time, just make sure they are identical. > This is an applet illustrating time dilation in bodies moving > in the vicinity of the Earth. > > http://home.c2i.net/pb_andersen/Satellites.html Very nice work. I had a look at it on a sandbox office machine. Too bad I can't take a closer look. I have banned that horrible piece of Java RE from my day to day machine. Never understood how the very worst piece of software on the planet managed to become that popular :-( Dirk Vdm In sci.physics.relativity, Paul B. Andersen <paul.b.andersen@hiadeletethis.no> wrote on Fri, 07 Dec 2007 14:55:01 +0100 <475950B5.5000005@hiadeletethis.no>: > This is an applet illustrating time dilation in bodies moving > in the vicinity of the Earth. [quoted text clipped - 4 lines] > while the Schwarzschild metric is used to determine their > proper times. The GUI needs a bit of work but the idea is an interesting one. I'm also curious as to whether there's an explanation of the formulas used; http://relativity.livingreviews.org/open?pubNo=lrr-2003-1 though might be a starting point were I to pursue this as an applet. Unfortunately page 5 warns that Keplerian orbits are a poor approximation at low altitude. It's also not clear what the rotating thing is, unless that represents a spherical planet of about 6378 km in radius, superimposed on a stationary polar coordinate system. > A short comment to the scenarios in the applet: > [quoted text clipped - 35 lines] > Missing a scenario? > Give me a hint, and I may add it. A scenario you might want, if you can get the precise data for it, would be a reprisal of Hafele & Keating. You might also consider a moon shot, though that might complicate things a bit since the moon warps and twists space as well. I have no idea if anyone's pursued time deltas in a modern moon probe. For that matter you could try the moon itself as an orbiting item. You might also want to embed the applet in a Web Page along with these scenarios and the formulas and/or a link, plus the usual disclaimers regarding computer modeling. There's also a typo in "two oppsosite orbits". And of course the results computed here might be compared (via a link) to real-world results. Signature#191, ewill3@earthlink.net Linux makes one use one's mind. Windows just messes with one's head. -- Posted via a free Usenet account from http://www.teranews.com : In sci.physics.relativity, Paul B. Andersen : <paul.b.andersen@hiadeletethis.no> [quoted text clipped - 17 lines] : an applet. Unfortunately page 5 warns that Keplerian orbits : are a poor approximation at low altitude. If Andersen drew a picture of a cat and wrote "woof-woof" beside it that would be as convincing a demo that a cat was a dog as a satellite with the wrong time beside it convinces everyone of time dilation. : It's also not clear what the rotating thing is, unless : that represents a spherical planet of about 6378 km in radius, : superimposed on a stationary polar coordinate system. I just can't see what is supposed to be happening. Hey look, this is length contraction: 0|_______________________|11 See, my 12" ruler has contracted to 11 inches because I wrote 11 at the end instead of 12. Very convincing, I'm sure. : > A short comment to the scenarios in the applet: : > [quoted text clipped - 52 lines] : And of course the results computed here might be compared : (via a link) to real-world results. If he's going to do a demo then he needs to slow down light to a manageable speed as every other demo does. You know full well that all the paradoxes begin with letting v = 0.866c or 0.9c or 0.6c or some such value. I want to see the twins demo kind of where satellite A meets satellite B before satellite A meets satellite B as measured by their own clocks. Y'know, one hour passes for A and it meets B, but two hours pass for B before it meets A. That would be really convincing, especially if they used sundials synchronized to sundials on the ground. In sci.physics.relativity, Androcles <Engineer@hogwarts.physics_a> wrote on Sun, 09 Dec 2007 20:00:42 GMT <KPX6j.20677$kt3.16253@fe3.news.blueyonder.co.uk>: >: In sci.physics.relativity, Paul B. Andersen >: <paul.b.andersen@hiadeletethis.no> [quoted text clipped - 32 lines] > > 0|_______________________|11 There *is* no length contraction in SR. One cannot *measure* length in SR (or any other theory, really). The best one can do is measure *time* contraction, with an accurate velocity determination (which *is* possible if one assumes constant lightspeed), if the moving item is going too fast. > See, my 12" ruler has contracted to 11 inches because I wrote 11 > at the end instead of 12. Very convincing, I'm sure. Affix the ruler to the side of a car moving at 67 mph (30 m/s) and get back to me on how you'd measure it. ;-) >: > A short comment to the scenarios in the applet: >: > [quoted text clipped - 63 lines] > That would be really convincing, especially if they used > sundials synchronized to sundials on the ground. I'll refer you to Hafele-Keating for an experimental verification of a variant of the twin paradox. Signature#191, ewill3@earthlink.net Useless C++ Programming Idea #12995733: bool f(bool g, bool h) { if(g) h = true; else h = false; return h;} -- Posted via a free Usenet account from http://www.teranews.com : In sci.physics.relativity, Androcles : <Engineer@hogwarts.physics_a> [quoted text clipped - 51 lines] : Affix the ruler to the side of a car moving at 67 mph (30 m/s) : and get back to me on how you'd measure it. ;-) A simple engineering technique that has you non-thinking physics types baffled or you wouldn't ask. I'd get in the car. : >: > A short comment to the scenarios in the applet: : >: > [quoted text clipped - 66 lines] : I'll refer you to Hafele-Keating for an experimental verification : of a variant of the twin paradox. More noise than signal. In sci.physics.relativity, Androcles <Engineer@hogwarts.physics_a> wrote on Mon, 10 Dec 2007 01:12:38 GMT <ao07j.22084$kt3.8608@fe3.news.blueyonder.co.uk>: >: In sci.physics.relativity, Androcles >: <Engineer@hogwarts.physics_a> [quoted text clipped - 57 lines] > A simple engineering technique that has you non-thinking > physics types baffled or you wouldn't ask. I'd get in the car. That changes the problem. The requirement is to measure the ruler from a stationary point as the car is moving past that point. Getting into the car allows one to measure the ruler from a moving point as the car is moving past the stationary point. It is naive to think the two measurements will be identical. >: >: > A short comment to the scenarios in the applet: >: >: > [quoted text clipped - 68 lines] > > More noise than signal. Ah, yes, of course. Noted. Signature#191, ewill3@earthlink.net Useless C/C++ Programming Idea #10239993: char * f(char *p) {char *q = malloc(strlen(p)); strcpy(q,p); return q; } -- Posted via a free Usenet account from http://www.teranews.com : In sci.physics.relativity, Androcles : <Engineer@hogwarts.physics_a> [quoted text clipped - 67 lines] : the ruler from a stationary point as the car is moving : past that point. Funny way to attach a ruler, but if you can attach it on the fly I expect you can measure it just as easily. : Getting into the car allows one to measure the ruler from : a moving point as the car is moving past the stationary : point. Yeah, it does. : It is naive to think the two measurements will be identical. It is naive to think you can attach a ruler to a car travelling past you at 67 mph (30 m/s). It is even more naive to suggest that would change its length. : >: >: > A short comment to the scenarios in the applet: : >: >: > [quoted text clipped - 70 lines] : : Ah, yes, of course. Noted. Always is in "relativistic" measurements. If a twin leaves Earth and travels some distance xi while his clock slows because of his relativistic velocity, then without changing the coordinates his clock speeds up on the return journey, the Andersen Transforms prove it. "That is, we can reverse the directions of the frames which is the same as interchanging the frames, which - as I have told you a LOT of times, OBVIOUSLY will lead to the transform: t = (tau-xi*v/c^2)/sqrt(1-v^2/c^2) x = (xi - v*tau)/sqrt(1-v^2/c^2) or: tau = (t+xv/c^2)/sqrt(1-v^2/c^2) xi = (x + vt)/sqrt(1-v^2/c^2)" -Paul B. Andersen t has some amount added and then that is divided by something less than one. Hence tau > t on the return trip. The faster you go, the longer it takes to get there. Either that or Tusseladd is a Norwegian troll. Oh, wait... that's what tusseladd means. > This is an applet illustrating time dilation in bodies moving > in the vicinity of the Earth. > > http://home.c2i.net/pb_andersen/Satellites.html Time dilation is not measured through the proper time but coordinate time. <shrug> Although it is very nicely done, I do not find your fancy applet serving any useful purpose. <shrug> Notice even if all the satellites in the same altitude have faster passage of time compared with the ground, a simple synchronization among these satellites should render any rate in passage of time irrelevant for GPS applications. This once again proves that engineers are smarter than physicists. <shrug> >> This is an applet illustrating time dilation in bodies moving >> in the vicinity of the Earth. [quoted text clipped - 12 lines] >irrelevant for GPS applications. This once again proves that >engineers are smarter than physicists. <shrug> Fortunately you are neither an engineer nor a physicist. : > This is an applet illustrating time dilation in bodies moving : > in the vicinity of the Earth. [quoted text clipped - 3 lines] : Time dilation is not measured through the proper time but coordinate : time. <shrug> Aether is not measured at all. <shrug> Like time dilation, it doesn't exist. <shrug> You are an idiot. <shrug> >> This is an applet illustrating time dilation in bodies moving >> in the vicinity of the Earth. [quoted text clipped - 12 lines] > irrelevant for GPS applications. This once again proves that > engineers are smarter than physicists. <shrug> That you find a synchronization among 24 satellites in different orbits simple, proves that engineers are smarter that you. They synchronize each individual satellite to GPS-time from the ground. SignaturePaul http://home.c2i.net/pb_andersen/ In sci.physics.relativity, Paul B. Andersen <paul.b.andersen@hiadeletethis.no> wrote on Fri, 28 Dec 2007 13:32:37 +0100 <4774ECE5.1080809@hiadeletethis.no>: >>> This is an applet illustrating time dilation in bodies moving >>> in the vicinity of the Earth. [quoted text clipped - 19 lines] > They synchronize each individual satellite > to GPS-time from the ground. I'm not sure they even bother with that. As I understand it, a time check is uploaded daily to each satellite; that time check, along with the current satellite time, the time the satellite received the time check, and a satellite ID, are what the ground-basd GPS receiver receives. I don't see this as synchronization, but it is of course necessary in some form. Signature#191, ewill3@earthlink.net Linux. Because it's there and it works. Windows. It's there, but does it work? -- Posted via a free Usenet account from http://www.teranews.com > As I understand > it, a time check is uploaded daily to each satellite; that [quoted text clipped - 4 lines] > I don't see this as synchronization, but it is of course > necessary in some form. This is indeed clock synchronization, but in keeping with the GPS design, it happens in the receiver, not in the satellite. That's merely an engineering decision, and does not affect the principle that the receiver needs clocks synchronized in the ECI frame to determine its position and time. Tom Roberts |
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