Tim88
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Black Hole: Why do we believe that matter could be such dense?
Tim88 replied to MaximT's topic in Astronomy and Cosmology
That's more to the point. Do you mean that simulations that have particles forever more slowly falling towards the centre, using GR equations from our point of view, do not agree with observations? On second thought, likely you just mean that there is overwhelming support for the gravitational collapse of stars, which is getting back to the topic of this thread. 
Black Hole: Why do we believe that matter could be such dense?
Tim88 replied to MaximT's topic in Astronomy and Cosmology
"It never slowed down"??. Correct is to say that of course from its own frame of measurements, it never slows down. From our frame of reference not only those objects become invisible, anything that would be observed by comoving observers is unverifiable  moot as you say. 
Black Hole: Why do we believe that matter could be such dense?
Tim88 replied to MaximT's topic in Astronomy and Cosmology
"From someone like me"? It's a corner stone of doing science.... Just now I got an email from Qreeus telling me that he found a mistake in that analysis. Indeed, that could hardly have been correct, as it seems obvious that in that region anything has to keep moving at locally c. There is indeed no literal surface; instead, as interpreted by a distant observer, there is the huge gravitational potential that slows down infalling objects so much that their radial speed becomes nearly zero. Further, a growing event horizon will of course displace that "surface" to beyond that position  kind of "burying" the particle inside the zone of extremely high gravitational potential. If I'm not mistaken, the gravitational potential won't be reduced below that "surface"; consequently, such burying cannot make it speed up again. 
Black Hole: Why do we believe that matter could be such dense?
Tim88 replied to MaximT's topic in Astronomy and Cosmology
I meant that he reminded me of it. And oops you are right  thanks! OK that works 
Black Hole: Why do we believe that matter could be such dense?
Tim88 replied to MaximT's topic in Astronomy and Cosmology
Indeed. Although, I find "of having coordinate c > 0 at 'EH" is that'" somewhat poorly phrased, I would say "of having c > 0 at the 'EH' position" ; and it's a bit ambiguous that he referred to the pov of the outside observer, according to whom there would indeed be an "infaller's 'stopped coordinatetime clock'" at that position. Anyway, it makes much logical sense, even in relativity there can only be one single reality! He could be more polite though (not that he's the only one here...). Note: yesterday Qreuss mentioned this forum to me and just now I tried to search his contributions in other threads  but regretfully that became impossible! Apparently that is related to the fact that a few hours ago he was "permanently banned for spamming the forum with nonsense". Well then, ... Good luck. 
No, not those; that's not what is meant with "the predecessors". The comparison is with the simplified calculations for time periods of 100'000 yrs and more, the socalled Milankovitch calculations and variants thereof  http://www.indiana.edu/~geol105/images/gaia_chapter_4/milankovitch.htm .

Apparently the approximate calculations that everyone used until now do not even include the nutation; in other words, those do not "lag" the measurements but simply don't reproduce them  and apparently they were wrong for their intended use as well. The correct and accurately calculated nutation is one of the verifications of the correctness of the new, exact calculations that are discussed in the paper. Regretfully, we cannot directly verify the calculations over 100'000s of years with measurements.

I now got a reply from Smulsky. He points out that in fact there is an additional, astronomical verification: the constant of nutation. That's an oscillation of 9.2'' with a period of 18.6 years  https://en.wikipedia.org/wiki/Astronomical_nutation#Nutation_of_the_Earth.27s_axis As described in Smulsky's fig.10, this observed phenomenon is exactly reproduced by his calculation model  Smulsky J.J. Fundamental Principles and Results of a New Astronomic Theory of Climate Change. He further comments in his email (with a slight correction of his Google Translate Russian>English), with added emphasis: It looks to me that there is no reason to doubt the new calculation results. Thus, the one year silence after his peer reviewed publication suggests to me that people are putting their heads in the sand, in an attempt to just ignore it.

Could relativity be incorrect
Tim88 replied to PrimalMinister's topic in Modern and Theoretical Physics
Probably you misunderstood him. He was comparing constant straight line acceleration with constant centripetal acceleration (= in a circle, or "rotational"): In contrast to rectilinear acceleration, there is no energy input.for the simple case of a body that is freely rotating at constant centripetal acceleration (constant rotation speed). 
Could relativity be incorrect
Tim88 replied to PrimalMinister's topic in Modern and Theoretical Physics
mistermack didn't say "rigid body"... anyway, that's an interesting assertion; please clarify! 
Any Anomalies in Bell's Inequality Data?
Tim88 replied to TakenItSeriously's topic in Quantum Theory
I now found it back: https://arxiv.org/abs/1112.2629 In a nutshell, the authors conclude that the experimental data by Weihs et al are not in agreement with the predictions of QM: "It is highly unlikely that quantum theory describes the data of the EPRB experiment that we have analyzed." As it's apparently only in ARXIV, it's definitely a discussion item  up to TakenItSeriously if he's interested! 
As I now understand it, the approximate and the accurate calculations are all accurate (agreeing with each other and with measurements) for the time of human history. Consequently, it is necessary to compare the calculated variations with the geological record. In the paper a comparison is made with the ice ages, as established with dating techniques.

Could relativity be incorrect
Tim88 replied to PrimalMinister's topic in Modern and Theoretical Physics
Indeed accelerating frames are for local use; that was already done in classical mechanics but GR extended it for all physical phenomena. There's another issue that none of us addressed but is coming back every time: there is no "moving faster than light eventually" involved. Accelerating objects as measured with a "stationary frame" (also called "coordinate acceleration") accelerate less and less fast as they reach high speed. That was even one of the first predictions of SR, about the fact that electrons cannot be accelerated to the speed of light. Note also the subtle difference with proper acceleration, which is the acceleration relative to instantly comoving reference frames.The fact that nothing can break the speed of light is true for someone who has a constant proper acceleration of 9.8 m/s2. 
Any Anomalies in Bell's Inequality Data?
Tim88 replied to TakenItSeriously's topic in Quantum Theory
Hi Mordred, thanks for the wealth of references. I doubt that Bayesian vs Gaussian statistics matters here, as I cited how Bell did not even pretend to give a rigorous proof of his starting equation. Nevertheless, since I have the statistics book of Jaynes [PS I'm well beyond chapter one lol] and still plan to work my way completely through it one day, your references are appreciated and maybe one day I'll contact you with questions about a certain chapter. Also, I agree that the "particle" approach is probably a dead end  just for the record, as we're drifting away from the topic (sorry TakenItSeriously!). More on topic, I recall that I read somewhere that the results of some well known Bell type measurements do not agree well with the predictions of QM, but that this fact was overlooked in the first article on those experiments (sometimes one only sees what one is looking for). I will try to find that back. 
Any Anomalies in Bell's Inequality Data?
Tim88 replied to TakenItSeriously's topic in Quantum Theory
That's a good one! In fact there seems to be something of a mathematical "anomaly" here. That equation is according to Jaynes an unproven simplification of locality in Bell experiments. According to him, "fundamentally correct" would be (in his notation): P(ABabλ) = P(ABabλ) P(Babλ) Now, I'm not 100% sure that he was right, but I suppose that an expert like him would not make a mistake about such a fundamental issue. And as a matter of fact, even Bell admitted that his simple equation is not based on mathematical rigor but instead, it is based on plausible looking assumptions ("It seems reasonable to expect that"  Bertlmann's socks). As the result led to extraordinary claims, extraordinary evidence is required. Reasonable seeming expectation does not suffice. 
Could relativity be incorrect
Tim88 replied to PrimalMinister's topic in Modern and Theoretical Physics
What does that obvious fact have to do with the issues that PrimalMinister and mistermack have with interpretations of relativity by certain writers? As I understand their issues, they are struggling with a mixup that happens at the source of information. The issue here, I think, is not that writers are unclear or confusing about their definitions. All too often even in textbooks metaphysics is sold as physics, sometimes even accompanied by misleading or false information. That causes the most confusion. Let's wait for their comments. 
Could relativity be incorrect
Tim88 replied to PrimalMinister's topic in Modern and Theoretical Physics
How about this: Einstein speculated in 1916 that "The general theory of relativity renders it likely that the electrical masses of an electron are held together by gravitational forces." (in Relativity: The Special and General theory, English translation of 1920).  https://en.wikisource.org/wiki/Relativity:_The_Special_and_General_Theory/Part_I#cite_note14 Once more (sticking to the topic), it's all a matter of interpretation and definitions, quite independent of the mathematical theory. 
Could relativity be incorrect
Tim88 replied to PrimalMinister's topic in Modern and Theoretical Physics
Adding to that, it depends on one's definition of "force" if we call it a force or not. In fact, Einstein still called it a force in 1916 when he explained GR. Plays on words should not hinder our understanding! 
Hi bvr, that's a nice "light clock" gif!
t looks like a lot of work... maybe you had a trick or tool for that?

Thanks Tim88.
I didn't use a special tool, just Gimp and an online tool: http://gifmaker.org
It took me several hours and some patience, there are 84 frames.


What exactly do you understand with "absolute time", and why do you think that it has been shown not to exist? Negatives are generally hard to show! Note the subtle difference with the fact that time is not absolute. Maybe that is what you meant?

Could relativity be incorrect
Tim88 replied to PrimalMinister's topic in Modern and Theoretical Physics
"Bending and warping spacetime" is in fact a geometrical description of the mathematics. You definitely don't have to that literal, as a description of "hidden reality". Here, just do a word search in one of the most famous papers, and see if you can find "bending and warping spacetime", or something equivalent : http://fourmilab.ch/etexts/einstein/specrel/www/ Special and General relativity are in fact mathematical models that make, for the time being, rather satisfying predictions about natural phenomena; they do not pretend to tell us "what really happens". However they do strongly limit the options of what may be "really going on", or "under the hood" so to say. I have no idea if your "cellular automata" are compatible. But that brings us out of the realm of physics in the narrow sense of the word. Happily we have an appropriate sub forum for that. For a discussion of two historical interpretations that work, see http://www.scienceforums.net/topic/98845modelsformakingsenseofrelativityphysicalspacevsphysicalspacetime/ 
From my side I also have some difficulties with posts by different people, for example I can guess what bvr may have meant with "measuring light with light", but I'm not sure. Probably it's an oversimplification; remember the intended level of this thread. I hope that he'll clarify that as geordief already asked for. Concerning time dilation, the simplest illustration is the light clock  which is a very nice illustration of time dilation at a beginners level and appropriate for this discussion. It illustrates something similar as what bvr may have had in mind (again simplifying). As determined in the "rest" frame, the light clock's "time" is indeed "dilated" because the signal trajectories between "moving" atoms (mirrors in this case) are increased. That's the first stepping stone towards understanding the MichelsonMorley experiment. It may be useful for geordief to have a look at it.  https://simple.wikipedia.org/wiki/Light_clock  https://en.wikipedia.org/wiki/Time_dilation#Simple_inference_of_velocity_time_dilation (not sure that "simple wikipedia" is the easiest to understand)

That's probably the same misunderstanding: what I quoted from Bell was about length contraction (the LorentzFitzgerald kind) related to internal EM fields. That's part of a more "constructive" approach to teaching SR. PS: that is exactly what bvr meant with the remark that you claimed to be wrong, as we see just now in his latest post. If you think that you can disprove Bell's "How to teach relativity" then please start it as a new topic, so as not to hijack the discussion here about understanding light propagation in SR. It would certainly deserve a discussion thread on its own, and it can be interesting.

Huh? "in its own frame" the object is of course not moving; that's besides the point. Similarly, a fast moving object has increased kinetic energy compared to rest; the objection that this is wrong because "in its own frame" this is not so, is irrelevant. Maybe I overlook some big error but more likely you misunderstand what bvr is saying here. Bell explained in his famous "How to teach relativity" the implications of the Maxwell equations as follows: "The magnetic field is transverse to the direction of motion and, roughly speaking, the system of lines of electric field is flattened in the direction of motion (Fig. 4). In so far as microscopic electrical forces are important in the structure of matter, this systematic distortion of the field of fast particles will alter the internal equilibrium of fast moving material. It is to be expected therefore that a body set in rapid motion will change shape."

As I understand it, they only compared different accurate calculations with each other and with the old ones, which most others still use. Apart of that, they obtained a better match with the historical ice ages  but that is of course very indirect. Thus I like your reference to direct measurements thanks! I may write to the author and ask if they considered comparing with such direct measurements. However it may be that the time frame is much too short. And I do not quite understand that picture: "a reference frame which is defined by the adopted locations of terrestrial observatories. The coordinate x is measured along the 0o (Greenwich) meridian [..]". I thought that the North Pole defines that reference frame  in which case it cannot move relative to it, right??