tag:blogger.com,1999:blog-8148573551417578681.post5186241296549705083..comments2020-02-18T23:15:04.706-08:00Comments on Dark Buzz: History of SpacetimeRogerhttp://www.blogger.com/profile/03474078324293158376noreply@blogger.comBlogger18125tag:blogger.com,1999:blog-8148573551417578681.post-14203221799948231062017-07-18T04:57:15.058-07:002017-07-18T04:57:15.058-07:00It looks like you have re-discovered the old disti...It looks like you have re-discovered the old distinction between the map and the territory. Imaginary numbers and curved space are just conventions, like Poincare always said. See geometric algebra, for instance. The notion of dimension doesn't have to conform to your notion of "symmetry." The arrow of time and entropy are an assumption. I think your problem is essentialism about physics. Physics doesn't really explain anything and is a rather dull subject. It will always be an infinite regress of whys. Autistic people and people with left-hemisphere lateralization find simple physical things interesting, while most human beings find them quite literal minded and not very interesting.MD Coryhttps://www.blogger.com/profile/05342743632013663077noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-49492664822308862562017-07-16T18:24:01.015-07:002017-07-16T18:24:01.015-07:00"Yes, time coordinates are very different fro..."Yes, time coordinates are very different from space coordinates."<br /><br />Yes! So many "physicists" and "philosophers" are fond of saying "Einstein showed that space and time are the same thing." Wrong.Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-10750963782105947802017-07-16T16:33:48.256-07:002017-07-16T16:33:48.256-07:00Yes, until someone observes a graviton, quantum gr...Yes, until someone observes a graviton, quantum gravity is a silly subject, guaranteeing tenure, titles, and tax dollars for thousands of "physicists".Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-33015775683010445382017-07-16T14:36:56.746-07:002017-07-16T14:36:56.746-07:00Yes, time coordinates are very different from spac...Yes, time coordinates are very different from space coordinates.<br /><br />The Bee article is amusing. Nature mag publishes an article about speculation on impossible experiment, and she says that 100s of physicists have doing such untestable speculations for years!Rogerhttps://www.blogger.com/profile/03474078324293158376noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-355239893310983082017-07-16T13:48:25.704-07:002017-07-16T13:48:25.704-07:00Dear Roger,
You'll enjoy this one--quantum gr...Dear Roger,<br /><br />You'll enjoy this one--quantum gravity theorists publish article stating that "quantum gravity" is not really science, and a quantum gravity theorist gets upset for ignoring her non-existent meaningful non-*physical* "research."<br /><br />http://backreaction.blogspot.com/2017/07/nature-magazine-publishes-comment-on.html<br /><br />lol!!!Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-64690915440109577662017-07-16T13:00:52.099-07:002017-07-16T13:00:52.099-07:00A remarkable property of spacetime is that while o...A remarkable property of spacetime is that while one can stand still in space (x1, x2, x3) in an inertial frame, there exists no frame in which one can stand still in x4. Why is that? What causes this *foundational* difference between the dimensions?Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-63639783503281999092017-07-16T12:46:16.676-07:002017-07-16T12:46:16.676-07:00Yes I know that. But the question remains--"...Yes I know that. But the question remains--"What is the *physical* meaning of x4=ct?"<br /><br />One can write x4=ct instead of x4=ict, as Wheeler et al. did in their text.<br /><br />But then "What is the *physical* meaning of x4=ct?"<br /><br />Why does x4=ct, while x1 is not related to the velocity of light nor time?<br /><br />How is x4 physically different from x1, x2, x3?Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-40953070424817074382017-07-16T12:41:27.500-07:002017-07-16T12:41:27.500-07:00No, that is not what I mean. You can define the Mi...No, that is not what I mean. You can define the Minkowski metric using ct or ict. Those are just 2 ways of saying the same thing. Using ict instead of ct is the mathematical trick, with no physical significance.Rogerhttps://www.blogger.com/profile/03474078324293158376noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-79675637405250470852017-07-16T12:34:36.201-07:002017-07-16T12:34:36.201-07:00Or would you agree with the statement, "Using...Or would you agree with the statement, "Using E=hf is a mathematical trick that has some advantages in some formulas, but it is just a trick. Theoretical physics papers still use it sometimes today."?Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-67574400282105280932017-07-16T12:33:54.147-07:002017-07-16T12:33:54.147-07:00Would you agree with the statement, "Using F=...Would you agree with the statement, "Using F=ma is a mathematical trick that has some advantages in some formulas, but it is just a trick. Theoretical physics papers still use it sometimes today."?Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-66937872958312117092017-07-16T12:32:30.348-07:002017-07-16T12:32:30.348-07:00When Planck first wrote E=hf, he considered it a m...When Planck first wrote E=hf, he considered it a mathematical trick sans any physical meaning. Would you say that E=hf is a mathematical trick? :) Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-50604850989030574632017-07-16T12:22:33.516-07:002017-07-16T12:22:33.516-07:00Using ict is a mathematical trick that has some ad...Using ict is a mathematical trick that has some advantages in some formulas, but it is just a trick. Theoretical physics papers still use it sometimes today.Rogerhttps://www.blogger.com/profile/03474078324293158376noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-84693866476275701522017-07-16T12:19:51.383-07:002017-07-16T12:19:51.383-07:00Dear Roger--what's your interpretation of the ...Dear Roger--what's your interpretation of the physical meaning of x4=ict? What does it signify? Why does x4=ict? Why the relationship between the fourth dimension, the velocity of light, and time? We don't see this with x1, x2, or x3. Why only x4=ict?Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-10822217473413722982017-07-16T11:56:53.508-07:002017-07-16T11:56:53.508-07:00Thanks Roger!
What's your take on the below c...Thanks Roger!<br /><br />What's your take on the below comment, Roger?<br /><br />I think I found the answer to my own question! <br />https://www.researchgate.net/post/By_dismissing_Minkowskis_notation_x4ict_are_we_not_losing_an_essential_aspect_of_space-time_structure<br /><br />John Frederick Barrett · University of Southampton<br />Only recently I became aware of the interesting discussion here and shall try to answer the original question, comments welcome.<br /><br />Poincaré (1906) introduced the ict coordinate so that Lorentz transformations could be visualized as Euclidean rotations of the sphere<br /><br />x²+y²+z²+(ict)²= const.<br /><br />Then Minkowski (1908) took up the idea and made it into a powerful method for calculations in electromagnetic theory but he also applied it generally in SR. Sommerfeld (1909) further developed it for addition of velocity vectors in SR.<br /><br />The method was often used for many years but gradually went out of use in theoretical discussions largely due to the influential book 'Gravitation' of Misner, Thorne & Archibald (1973) attacking it strongly because of incompatibility with GR.<br /><br />I think that to understand the situation it is first necessary to understand why the ict method was so successful for SR. My explanation is as follows. The constant in Poincaré's sphere may be positive or negative depending on whether<br /><br />x²+y²+z²><(ct)².<br /><br />I think it is correct to make it negative which is the condition for the event (x,y,z,t) to be accessible with a velocity less than that of light either from or to the observer at (0,0,0,0). The sphere then has imaginary radius which means that is a hyperbolic (Lobachevsky) space. This conclusion follows more directly from the differential form when there follows directly using Minkowski's proper time τ (>0)<br /><br />dx²+dy²+dz²+(icdt)²=(icdτ)²<br /><br />Consequently the ict method enables us to do calculations in hyperbolic space, which is the correct formulation of SR (though still not generally recognized), by working in more familiar Euclidean space. When written<br /><br />(cdτ)² = (cdt)²-dx²-dy²-dz²<br /><br />the equation is in the form to correspond to the GR metric which is known to reduce to the Minkowski metric for linear approximation and weak gravitational fields. So the GR metric is basically the SR form plus nonlinear terms. It is these nonlinear terms which stop the ict method being used although for weak gravitational fields (e.g. for gravitational waves) it could still be used. The GR metric is in no way positive definite although usually represented as such. It is therefore of the type of a space of negative curvature."<br /><br />https://www.researchgate.net/post/By_dismissing_Minkowskis_notation_x4ict_are_we_not_losing_an_essential_aspect_of_space-time_structure<br /><br />What's your take on it Roger?<br /><br />Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-50943204043003756632017-07-16T11:55:35.281-07:002017-07-16T11:55:35.281-07:00What's your take on the below comment, Roger?
...What's your take on the below comment, Roger?<br /><br />I think I found the answer to my own question! <br />https://www.researchgate.net/post/By_dismissing_Minkowskis_notation_x4ict_are_we_not_losing_an_essential_aspect_of_space-time_structure<br /><br />John Frederick Barrett · University of Southampton<br />Only recently I became aware of the interesting discussion here and shall try to answer the original question, comments welcome.<br /><br />Poincaré (1906) introduced the ict coordinate so that Lorentz transformations could be visualized as Euclidean rotations of the sphere<br /><br />x²+y²+z²+(ict)²= const.<br /><br />Then Minkowski (1908) took up the idea and made it into a powerful method for calculations in electromagnetic theory but he also applied it generally in SR. Sommerfeld (1909) further developed it for addition of velocity vectors in SR.<br /><br />The method was often used for many years but gradually went out of use in theoretical discussions largely due to the influential book 'Gravitation' of Misner, Thorne & Archibald (1973) attacking it strongly because of incompatibility with GR.<br /><br />I think that to understand the situation it is first necessary to understand why the ict method was so successful for SR. My explanation is as follows. The constant in Poincaré's sphere may be positive or negative depending on whether<br /><br />x²+y²+z²><(ct)².<br /><br />I think it is correct to make it negative which is the condition for the event (x,y,z,t) to be accessible with a velocity less than that of light either from or to the observer at (0,0,0,0). The sphere then has imaginary radius which means that is a hyperbolic (Lobachevsky) space. This conclusion follows more directly from the differential form when there follows directly using Minkowski's proper time τ (>0)<br /><br />dx²+dy²+dz²+(icdt)²=(icdτ)²<br /><br />Consequently the ict method enables us to do calculations in hyperbolic space, which is the correct formulation of SR (though still not generally recognized), by working in more familiar Euclidean space. When written<br /><br />(cdτ)² = (cdt)²-dx²-dy²-dz²<br /><br />the equation is in the form to correspond to the GR metric which is known to reduce to the Minkowski metric for linear approximation and weak gravitational fields. So the GR metric is basically the SR form plus nonlinear terms. It is these nonlinear terms which stop the ict method being used although for weak gravitational fields (e.g. for gravitational waves) it could still be used. The GR metric is in no way positive definite although usually represented as such. It is therefore of the type of a space of negative curvature."<br /><br />https://www.researchgate.net/post/By_dismissing_Minkowskis_notation_x4ict_are_we_not_losing_an_essential_aspect_of_space-time_structure<br /><br />What's your take on it Roger?<br />Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-83651411461471984242017-07-16T11:52:53.840-07:002017-07-16T11:52:53.840-07:00Poincare first wrote x4=ict in his long 1905 paper...Poincare first wrote x4=ict in his <a href="http://blog.darkbuzz.com/2017/05/einstein-did-not-find-group-or.html" rel="nofollow">long 1905 paper</a>. Minkowski wrote the same thing in 1907. Minkowski cited Poincare in the references, but does not explicitly say whether he got the concept from Poincare or independenly found it. It seems likely that he got it from Poincare. Einstein did not use it until 1910 or so.Rogerhttps://www.blogger.com/profile/03474078324293158376noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-38244274222723553352017-07-16T11:43:36.677-07:002017-07-16T11:43:36.677-07:00What year did the concept of x4=ict first appear?What year did the concept of x4=ict first appear?Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-90056613091909336292017-07-16T11:41:19.153-07:002017-07-16T11:41:19.153-07:00Great post!
Who was the first to write x4=ict. W...Great post!<br /><br />Who was the first to write x4=ict. Was it Minkowski? Or Poincare? Or someone else? I think Minkowski did it before Einstein adopted it. But did Poincare do it even earlier?Anonymoushttps://www.blogger.com/profile/11811856497202846228noreply@blogger.com