tag:blogger.com,1999:blog-22973357.post3791480966640633529..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: Guest Post: Tam Hunt questions Carlo Rovelli about the Nature of TimeSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger294125tag:blogger.com,1999:blog-22973357.post-90916202120358403702018-12-06T14:16:38.410-05:002018-12-06T14:16:38.410-05:00bud rap;
“... it is upon you, since you propose t...bud rap;<br /><br />“<i>... it is upon you, since you propose the existence of time, that the burden of proof falls.</i>”<br /><br />So now you’re challenging the very existence of time, a phenomena everyone experiences and which has been the subject of thought and discussion since the beginning of history?<br /><br />“<i>That gets us to this peculiar straw-man argument from authority: ...</i>”<sean s.https://www.blogger.com/profile/04190153587965701495noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-48126799275356100192018-12-05T03:21:25.343-05:002018-12-05T03:21:25.343-05:00@bud rap: "There is no empirical evidence for...@bud rap: <i>"There is no empirical evidence for the existence of a substantival time - none."</i><br /><br />What empirical evidence is there for relational time? And what do you consider empirical evidence?<br /><br /><i>"So from a scientific perspective, the relational interpretation is in agreement with the non-observation of a substantival time, and it therefore follows that Wyrd Smythehttps://www.blogger.com/profile/06694506351266400927noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66492725708395291342018-12-04T17:55:25.217-05:002018-12-04T17:55:25.217-05:00Tam Hunt:
“Does time dilate when an ice breaker t...Tam Hunt:<br /><br />“<i>Does time dilate when an ice breaker travels through ice rather than open ocean? Does time dilate for a spoon when you pass it through molasses rather than air? ... passage of time more generally proceeds exactly the same, but certain physical processes may be slowed.</i>”<br /><br />The breakdown of muons created by cosmic rays is a process that is categorically sean s.https://www.blogger.com/profile/04190153587965701495noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-6931588857806123172018-12-04T13:10:31.238-05:002018-12-04T13:10:31.238-05:00@sean s,
"...you have yet to provide any emp...@sean s,<br /><br /><i>"...you have yet to provide any empirical evidence showing time being derived from other phenomena, or provide examples of “change without time”."</i><br /><br />I do <b>not</b> have to provide evidence for the non-existence of something that cannot be empirically demonstrated to exist. On the contrary, it is upon you, since you propose the existence of time, thatbud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72694455101253728462018-12-03T20:45:30.892-05:002018-12-03T20:45:30.892-05:00Sean S., not so. Does time dilate when an ice brea...Sean S., not so. Does time dilate when an ice breaker travels through ice rather than open ocean? Does time dilate for a spoon when you pass it through molasses rather than air? The point is that the passage of time more generally proceeds exactly the same, but certain physical processes may be slowed. Does such slowing mean time dilates from the perspective of the muon? Considering the larger Tam Hunthttps://www.blogger.com/profile/05919461715412820636noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-3751945218263971872018-12-03T16:19:37.770-05:002018-12-03T16:19:37.770-05:00@Tam Hunt: You may have misread my comment; I didn...@Tam Hunt: You may have misread my comment; I didn't mention any "actual tests." You are correct we assume time dilation occurs due to gravity, but that assumption seems correct. (If it isn't, GPS has a lot of 'splaining to do!)<br /><br />To be clear, the ytterbium clocks just provide <i>better accuracy</i> on tests already made, repeatedly, of GR. (The GPS system tests it Wyrd Smythehttps://www.blogger.com/profile/06694506351266400927noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-37655788218454115452018-12-03T13:03:54.187-05:002018-12-03T13:03:54.187-05:00bud rap; “In other words, Gamow's statement is...bud rap; “<i>In other words, Gamow's statement is consistent with the view that time is just a relational concept, not something in and of itself.</i>”<br /><br />Gamow’s statement is consistent with the idea that time is something in and of itself; Gamow’s statement implies a singular, universal time “flow” instead of one subject to local conditions.<br /><br />Your notion of “relational sean s.https://www.blogger.com/profile/04190153587965701495noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86584006807958122562018-12-03T10:42:17.002-05:002018-12-03T10:42:17.002-05:00It surely is the physical processes that slow down...<i>It surely is the physical processes that slow down, not “time.”</i><br /><br />But then physical processes are the only things we measure when we claim to measure "time". In other words, Gamow's statement is consistent with the view that time is just a relational concept, not something in and of itself.bud raphttps://www.blogger.com/profile/06948881286545517324noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-64266501428399949902018-12-03T09:37:44.228-05:002018-12-03T09:37:44.228-05:00Tam Hunt: “As for muons and time dilation, it'...Tam Hunt: “<i>As for muons and time dilation, it's more sensible to explain the data as interaction with the grav field, and physical slowing of processes, rather than time dilation.</i>”<br /><br />“<i>‘It surely is the physical processes that slow down, not “time.” The process of decay within the atomic particle as it flies through the Earth’s gravitational field is slowed down by its sean s.https://www.blogger.com/profile/04190153587965701495noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-67033578277543995322018-12-02T23:41:41.528-05:002018-12-02T23:41:41.528-05:00As for muons and time dilation, it's more sens...As for muons and time dilation, it's more sensible to explain the data as interaction with the grav field, and physical slowing of processes, rather than time dilation. Bethell explains this well in his book Questioning Einstein as follows: <br /><br />'Actually, another plausible explanation was suggested— inadvertently. George Gamow himself was responsible. As he was a friend of Tam Hunthttps://www.blogger.com/profile/05919461715412820636noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-39615569549405522702018-12-02T23:37:03.434-05:002018-12-02T23:37:03.434-05:00Chris, this is a good example of how easy it is to...Chris, this is a good example of how easy it is to misread papers. The new paper on ytterbium clocks says nothing about actual tests of GR. Rather, it discusses new clocks that are more accurate than today,s best clocks, that could in theory be used to test gravitational fields more accurately -- under the assumption that gravitational fields do in fact lead to time dilation. But no such tests Tam Hunthttps://www.blogger.com/profile/05919461715412820636noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-74987744748826332322018-12-01T13:36:16.632-05:002018-12-01T13:36:16.632-05:00I've been reading about the latest ytterbium a...I've been reading about the latest ytterbium atomic clocks, which have unprecedented accuracy and, importantly, reproducibility (which allows two clocks to be compared usefully). These clocks can detect the difference -- due to GR -- of just one centimeter difference in altitude. That's impressive!<br /><br />https://www.nist.gov/news-events/news/2018/11/Wyrd Smythehttps://www.blogger.com/profile/06694506351266400927noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20288141402401649172018-11-03T11:39:37.343-04:002018-11-03T11:39:37.343-04:00Reimond said You just had a minor typo, it should ...Reimond said <i>You just had a minor typo, it should be: … any gravitational field violates (global) Lorentz invariance …</i><br /><br />Yes, thanks.<br /><br />weristdas, in response to my statement "You overlooked the detection of time dilation for speeds as low as 20 mph", replied <i>I'm sure we are able to detect the Doppler effect at 20 mph.</i><br /><br />Sure, we can detect Amoshttps://www.blogger.com/profile/00595591283398023248noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-65160705154211312622018-11-03T08:01:43.912-04:002018-11-03T08:01:43.912-04:00Amos,
"You overlooked the detection of time ...Amos,<br /><br />"You overlooked the detection of time dilation for speeds as low as 20 mph "<br /><br />I'm sure we are able to detect the Doppler effect at 20 mph.weristdashttps://www.blogger.com/profile/04693023273675933748noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8363872081928599872018-11-03T04:48:28.966-04:002018-11-03T04:48:28.966-04:00Amos,
thanks for the great job you are doing here...Amos,<br /><br />thanks for the great job you are doing here to clarify SR and GR. I still wonder why Tam is not at all reacting to the obvious 2*sqrt(10²-5²)=17.32 or (mc²)² = E² – (pc)².<br /><br />You just had a minor typo, it should be: … any gravitational field violates (global) Lorentz invariance …<br /><br />Maybe this also might help: <br />- The symmetries of GR are local Lorentz and Reimondhttps://www.blogger.com/profile/04669340425105889539noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-57680423042729026952018-11-02T12:43:57.429-04:002018-11-02T12:43:57.429-04:00I think, now I'm understanding Tam Hunt's ...<i>I think, now I'm understanding Tam Hunt's concerns. An observer who is moving with approximately light speed should observe the same universe that we observe...</i><br /><br />No, Tam’s concerns were already answered (several times). Again, local Lorentz invariance is local, not global. For example, we can discern our speed relative to the frame in which the CMBR is isotropic. ThisAmoshttps://www.blogger.com/profile/00595591283398023248noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-78700003110776182042018-11-02T11:54:22.582-04:002018-11-02T11:54:22.582-04:00I haven't followed your discussion but an obse...I haven't followed your discussion but an observer moving at (or near) the speed of light relative to us would of course not observe the universe the same way as we do because the universe is not Lorentz-invariant. It has a preferred frame. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-14774314155584293052018-11-02T10:32:56.978-04:002018-11-02T10:32:56.978-04:00Amos,
"and half a meter of elevation"
...Amos,<br /><br />"and half a meter of elevation"<br /><br />I've never questioned graviatational time dilation.weristdashttps://www.blogger.com/profile/04693023273675933748noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-35849789338072725932018-11-02T10:30:09.479-04:002018-11-02T10:30:09.479-04:00I think, now I'm understanding Tam Hunt's ...I think, now I'm understanding Tam Hunt's concerns.<br /><br />An observer who is moving with approximately light speed should observe the same universe that we observe. But his universe is e.g. only 300 million years old. That's impossible in the view of the necessary time of development. (Implying "big bang theory")<br /><br />In particular, if natural constants as weristdashttps://www.blogger.com/profile/04693023273675933748noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-36266126230247626152018-11-01T13:32:26.573-04:002018-11-01T13:32:26.573-04:00weristdas said I can't understand, why gravita...weristdas said <i>I can't understand, why gravitation and motion produces two different measurable and distinct effects, but acceleration and motion not.</i><br /><br />You’re confusing accelerating objects and accelerating coordinate systems. Again, the elapsed proper time along any path is the integral of sqrt(g_mn x^m x^n) along that path, where the x^m are any system of coordinates (Amoshttps://www.blogger.com/profile/00595591283398023248noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-51035716986276063942018-11-01T08:04:57.801-04:002018-11-01T08:04:57.801-04:00Amos,
I can't understand, why gravitation and...Amos,<br /><br />I can't understand, why gravitation and motion produces two different measurable and distinct effects, but acceleration and motion not. As I had thought, a clock above another clock in an accelerated system should show time dilation, compared with the lower clock, as in the case of two clocks in gravitational field and constant motion.<br /><br />But okay, you are totally weristdashttps://www.blogger.com/profile/04693023273675933748noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12779205178670145192018-10-31T00:37:07.575-04:002018-10-31T00:37:07.575-04:00weristdas said I wonder why there should be a diff...weristdas said <i>I wonder why there should be a difference by the way we "treat" the case, or look at the case.</i><br /><br />You misread. The sentence you quoted was “When we treat acceleration as a pseudo-gravitational field, we get <b>the same</b> results as we would get in a corresponding real gravitational field for the same difference in potential energy.” (This is just the Amoshttps://www.blogger.com/profile/00595591283398023248noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69069974210420763162018-10-30T12:46:56.591-04:002018-10-30T12:46:56.591-04:00Amos,
"Yes, when we treat acceleration as a ...Amos,<br /><br />"Yes, when we treat acceleration as a pseudo-gravitational field, we get the same results as we would get in a corresponding real gravitational field for the same difference in potential energy."<br /><br />I wonder why there should be a difference by the way we "treat" the case, or look at the case.<br /><br />Question: If we observe a displacement of an weristdashttps://www.blogger.com/profile/04693023273675933748noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-31802315115072772032018-10-21T14:19:02.897-04:002018-10-21T14:19:02.897-04:00I wonder why the answer to my question concerning ...<i>I wonder why the answer to my question concerning time dilation by acceleration usually leads to answers with circular motion examples. Why that complication?</i><br /><br />Examples can be given for paths of any shape, not just circles. It so happens that circular paths are simple to describe because the distance is constant (strange that you regard them as a “complication”), but if you Amoshttps://www.blogger.com/profile/00595591283398023248noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-76651022919718695282018-10-21T06:52:00.487-04:002018-10-21T06:52:00.487-04:00Amos, 2:20 PM, October 17, 2018
I wonder why the ...Amos, 2:20 PM, October 17, 2018<br /><br />I wonder why the answer to my question concerning time dilation by acceleration usually leads to answers with circular motion examples. Why that complication?<br /><br />I have discussed that aspect elsewhere, and the advocates of relativity theory had stated, that it is possible to speak about "acceleration time dilation" analogue to "weristdashttps://www.blogger.com/profile/04693023273675933748noreply@blogger.com