Timeline for Reference frame doubts about isotropy
Current License: CC BY-SA 4.0
21 events
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| Nov 5, 2023 at 12:14 | comment | added | Giorgi Lagidze | even in newtonian, if you consider ground frame as non-inertial, then his statement is not false in which case the statement holds true in any inertial frame(whether it's GR or newtonian or whatever). In this case, since earth is non-inertial, it's true it's non-isotropic, but that doesn't make landau's statement false as he is talking about inertial frames while earth frame is not. This is all clear. I will confirm some details though | |
| Nov 5, 2023 at 12:06 | comment | added | Valter Moretti | ALMOST does not mean that IT IS. A reference frame at rest with the centre of sun and axes oriented according to the "fixed stars" is a much better approximation for instance. | |
| Nov 5, 2023 at 12:05 | comment | added | Giorgi Lagidze | He is not the first though, I always heard that in newtonian, earth frame is almost considered inertial :P let me wait for his answer. | |
| Nov 5, 2023 at 12:04 | comment | added | Valter Moretti | I do not know, ask him! :) Maybe Newton wrote it, but that notion has changed and improved several times in the history of physics. In particular by Mach and other people. | |
| Nov 5, 2023 at 12:03 | comment | added | Giorgi Lagidze | Why does John say that in newtonian, ground frame is inertial ? :) | |
| Nov 5, 2023 at 12:02 | comment | added | Valter Moretti | An inertial frame is a reference frame where any body, sufficiently far from the other bodies of the universe, appears to have a motion with constant (possibly zero) velocity. It is a theoretical notion evidently. | |
| Nov 5, 2023 at 12:00 | comment | added | Giorgi Lagidze | In newtonian mechanics, the way I understand "inertial frame" definition is if you can explain the mechanics without fictitious forces, then it's an inertial frame. if you're on ground and observe an accelerating frame where pendulum is hung, to you, you can explain its behaviours without fictitious forces. That's why it's inertial frame. Not only that, see John Rennie's answer on this question below which says: "However in Newtonian mechanics we can say it is an inertial frame with gravitational forces acting" | |
| Nov 5, 2023 at 11:58 | history | edited | Valter Moretti | CC BY-SA 4.0 |
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| Nov 5, 2023 at 11:58 | comment | added | Valter Moretti | Certainly! I don't understand why you think the contrary. | |
| Nov 5, 2023 at 11:56 | comment | added | Giorgi Lagidze | so, ground frame is not "inertial frame" even in newtonian mechanics ? | |
| Nov 5, 2023 at 11:55 | comment | added | Valter Moretti | Well it is false: earth's surface does not define an inertial frame at all. | |
| Nov 5, 2023 at 11:54 | comment | added | Giorgi Lagidze | you, being on earth's surface(as you're currently). in newtonian, it's considered inertial frame, but if you conduct experiments, you will see that space to you is non-isotropic | |
| Nov 5, 2023 at 11:53 | comment | added | Valter Moretti | What do you mean for "ground frames"? | |
| Nov 5, 2023 at 11:50 | comment | added | Giorgi Lagidze | Thanks for the answer. Yes, I understand the definition of homogeneity/isotropy, but if ground frame is inertial(in newtonian, which we know it is), how is space in it isotropic ? we know it's not isotropic. i don't know how landau's statement holds true in newtonian mechanics. maybe i misunderstood your answer :( | |
| Nov 5, 2023 at 11:45 | history | edited | Valter Moretti | CC BY-SA 4.0 |
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| Nov 5, 2023 at 11:31 | history | edited | Valter Moretti | CC BY-SA 4.0 |
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| Nov 5, 2023 at 11:23 | history | edited | Valter Moretti | CC BY-SA 4.0 |
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| Nov 5, 2023 at 11:17 | history | edited | Valter Moretti | CC BY-SA 4.0 |
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| Nov 5, 2023 at 11:06 | history | edited | Valter Moretti | CC BY-SA 4.0 |
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| Nov 5, 2023 at 11:01 | history | edited | Valter Moretti | CC BY-SA 4.0 |
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| Nov 5, 2023 at 10:56 | history | answered | Valter Moretti | CC BY-SA 4.0 |