2026-04-14T19:51:12Z https://yabu.me undrendo https://yabu.me/npub138sk0lzh3gten0ghz0sjvl8pgxtd5yfldxpnt2yshwr3u2vh78qsjcydzl https://s3.c.im/accounts/avatars/110/627/962/899/182/804/original/5a907732ac8249f7.png https://s3.c.im/accounts/avatars/110/627/962/899/182/804/original/5a907732ac8249f7.png https://yabu.me/nevent1qqspsjv9huvrtf0ykzpylynuas6j6dx3sfv7lqz7u79sjw6ddcd2wegzyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuznfvf29 In reply to <a href='/nevent1qqs2xczd2tnq7m480ndjqeg0t7wzu92gg8wy0f6jtenjfzvnn2s5p3cpaa846'>nevent1q…a846</a><br/>_________________________<br/><br/>There&#39;s a great guide here: &lt;<a href="https://www.big-8.org/wiki/Getting_Started_with_Usenet&gt">https://www.big-8.org/wiki/Getting_Started_with_Usenet&gt</a>;, it worked for me. 2025-05-25T11:11:04Z https://yabu.me/nevent1qqs8gmwlp7gg0shscsfddfau505praf0ryrfdkdqluv9ft0cf9mf4yqzyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuzvusw0r Through the pages of John Baez &lt;<a href="https://math.ucr.edu/home/baez&gt">https://math.ucr.edu/home/baez&gt</a>; (see also &lt;<a href="https://johncarlosbaez.wordpress.com&gt">https://johncarlosbaez.wordpress.com&gt</a>;) I&#39;ve seen that the sci.physics usenet newsgroup, especially sci.physics.research, always had quite interesting physics discussions; see for instance &lt;<a href="https://math.ucr.edu/home/baez/physics&gt">https://math.ucr.edu/home/baez/physics&gt</a>;.<br/><br/>Finally I managed to join, but it looks like I&#39;m late to the party. Lots of spam and very insulting posts on sci.physics, and sci.physics.research (luckily a moderated group) seems to have very little activity – unless I&#39;m misjudging the levels of activity of some years ago.<br/><br/>So I&#39;d like to ask <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1nf4p4rh06z6n6lsvje4txk7eqs23y3hs8vd7nraq6tgwady5qvsqy3nqe4" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>John Carlos Baez</span> (<span class="italic">npub1nf4…nqe4</span>)</a></span> (when/if he has time): what happened to these newsgroups? I&#39;d be curious to hear the story. And which other similar newsgroups or venues are available today? Probably I&#39;m not the only one with these wonderings. Cheers!<br/><br/>#usenet #johncarlosbaez 2025-05-25T08:06:52Z https://yabu.me/nevent1qqsfmkhtzz69843tqa38jj90j4az0f66mrnhrjutmjvk9k4c356gskszyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuzv9vwa6 In reply to <a href='/nevent1qqs043ss3vdnvdwvp0g7m4fyzr76tmfhj30yrd78m2928lg8sfk4seqp9e58g'>nevent1q…e58g</a><br/>_________________________<br/><br/>Well, there are also positive sides. Edwin T. Jaynes &lt;<a href="https://bayes.wustl.edu/etj/etj.html&gt">https://bayes.wustl.edu/etj/etj.html&gt</a>; had notorious difficulties in getting his Bayesian-theory papers published, because the &#34;establishment&#34; was largely anti-Bayesian at the time. Luckily he could get published at conference proceedings though.<br/><br/>...Which is a reminder that, in Galilean science, peer-review should be left to the reader – that&#39;s why it&#39;s called &#34;peer&#34;. Otherwise we&#39;re back to pre-Galilean times with their Index Librorum Prohibitorum (which included important works by Kepler and Kant). Reviews and commentaries are welcome, but &#34;rejection&#34; (by two or three unknown people, which can scarcely be a representative sample of the whole scientific community) is anti-scientific. Luckily the internet has changed this situation. 2025-04-15T16:39:27Z https://yabu.me/nevent1qqsg6qrd2e8xmpj8enrv8fdns7g94ks7u98n7c8ccwavr2hlj8yaayszyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuz65vn8u In reply to <a href='/nevent1qqsvjkpnkjapl2t4gvl00sx33k3zkcrquerh7tupyde0unem3k097zqc9cltd'>nevent1q…cltd</a><br/>_________________________<br/><br/>There are several steps that look strange:<br/><br/>- eqn (13): the notation &#34;d/dτ&#34; stands for a covariant derivative &#34;u⋅∇&#34;, but it isn&#39;t clear which connection they&#39;re using for the &#34;∇&#34;, if it&#39;s the same described in the previous lines. But then how is the proper time τ modified, given that they modify the metric to include an electromagnetic potential?<br/><br/>- eqn (24): they define the norm ρ of the charge 4-current to be equal to &#34;-A⋅u&#34;. Something feels wrong about the degrees of freedom here. In principle there can be other forces, which means that &#34;A&#34; and &#34;u&#34; can be independent; and we know that &#34;ρ&#34; is independent as well – you can put any charge in any electromagnetic field. This equation instead makes ρ dependent. But maybe I&#39;m miscounting the degrees of freedom.<br/><br/>I think they should have proceeded in a less nonchalant way in their steps and explanations, though, given the potential novelty of this result.<br/><br/>Maybe <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1nf4p4rh06z6n6lsvje4txk7eqs23y3hs8vd7nraq6tgwady5qvsqy3nqe4" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>John Carlos Baez</span> (<span class="italic">npub1nf4…nqe4</span>)</a></span> has some comments on this paper as well. 2025-04-15T12:40:33Z https://yabu.me/nevent1qqs9pdrx08z4khyatm7n2p22sew2v2wpqdlxwp33d82rw065yh4n88czyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuzlm0gd9 In reply to <a href='/nevent1qqs05w5x2tnegjgear96ur40hlphp85e0j4jx3watg0tedv3clu0ccqyxyw5v'>nevent1q…yw5v</a><br/>_________________________<br/><br/>Interesting article and approach. From what I see there&#39;s no *general* relativity there yet – they are modifying the (Minkowski) metric of flat spacetime. Looking forward to seeing how a general pseudoRiemannian metric and therefore gravity gets integrated into this picture. 2025-04-15T06:11:18Z https://yabu.me/nevent1qqsyas3cyjwm5ukn04k74sn0gxuke6e36pjpxq58azx5vd244llk0egzyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuzdn4e60 In reply to <a href='/nevent1qqs2uw8wtcuycd4el4vquvv5v8m2ku559yrj06huae2xap6487n4mkcs2np22'>nevent1q…np22</a><br/>_________________________<br/><br/>According to Weinberg &lt;<a href="https://www.harpercollins.com/products/to-explain-the-world-steven-weinberg&gt">https://www.harpercollins.com/products/to-explain-the-world-steven-weinberg&gt</a>;, Ptolemy used just one epicycle+referent(+equant) for all planets, except Mercury which needed more. I don&#39;t remember if the book discusses Copernicus. 2025-01-06T19:27:23Z https://yabu.me/nevent1qqsqd5caly7l4a52nu7xgf3c8cayq0hvz9fkpyj7udd5sa6856s68wqzyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuzqltns7 In reply to <a href='/nevent1qqszqytz0rl69qsspyslkydmzxx9xmf8szf33knvn7s3cst90nngekqeulskz'>nevent1q…lskz</a><br/>_________________________<br/><br/>Enclosing relevant pages from Gingerich&#39;s book. It&#39;d be cool to redo the calculations Gingerich made.<br/> <img src="https://s3.c.im/media_attachments/files/113/653/397/778/986/514/original/5ec19213909443b8.jpg"> <br/> 2024-12-14T21:57:21Z https://yabu.me/nevent1qqsq0jldugu00qnpy6glpn5xt4s8u2gjsrxf4wtr5d94ng8k95snqjqzyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuzwp34yn In reply to <a href='/nevent1qqs9dpthvfvvraaz6yh579kmv7s3cgs0w0ytyfdeyg94yqkf627kzzgpqn7d0'>nevent1q…n7d0</a><br/>_________________________<br/><br/>I&#39;d love to see references where I can verify either claim! 2024-12-14T19:24:27Z https://yabu.me/nevent1qqsdjdvrp2s4ruwguj2gxa4h0kjvxxwy53y98fhnyrsrap7dp8l6t5qzyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuz4g0y7m In reply to <a href='/nevent1qqspkhejs46pz9xvv4qvqm67hvkne9gyj7wmfmunep9nqrvexd43k0s358dk0'>nevent1q…8dk0</a><br/>_________________________<br/><br/>Mine is a firm – and of course personal – idea. I don&#39;t see any divisions of subjects either, and in principle I don&#39;t care about Nobel prize and similar fluff.<br/><br/>But I&#39;m noticing an increasing problem (a problem from my point of view), which I could express this way: there may be fewer and fewer people who want to hear about ideas from statistical mechanics that underlie machine learning. Because, why bother about statistical mechanics? Just put the data in a machine learning algorithm, and let it make the prediction.<br/><br/>I&#39;m noticing this in my university department and others. As a physicist/mathematician, my deepest pleasure comes from trying to understand a phenomenon, in a combination of physical-geometric visualization and maths; hopefully in a way that leads to new physical-geometric ideas and even new maths. But in many new physics projects there is opposition to this: more and more people push to just put measurement data in machine-learning algorithms, train them, make them predict the quantities of interest. And they may well succeed. But what about the physical understanding of the phenomenon?<br/><br/>Maybe the idea of the Nobel Prize committee was to emphasize the importance of physics to computer science. But I think the result will be the opposite, leading to an increase in the problem above.<br/><br/>Maybe this is just a passing phase. Maybe not. And of course there&#39;s no &#34;right&#34; or &#34;wrong&#34;. Who says how &#34;physics&#34; should be done? Still it makes me deeply sad. 2024-10-08T20:37:37Z https://yabu.me/nevent1qqsfth6j8d2hluthaepy2sf38xp4nmrzc39gmnuhnkdvqrug9wrn8xgzyzy7zelu279p0xdazuf7zfnuu9qedks38a5cxddgjzacw83fjlcuzd0pd7s In reply to <a href='/nevent1qqsysvzgwcvzhvdkq6mc429rcx8x7r064rfkzwjzk62tpx2ajgtu3qczs3j6x'>nevent1q…3j6x</a><br/>_________________________<br/><br/>Agree. Physics ideas have entered in so many different fields. Then one can give a Nobel prize in physics for basically anything. I&#39;d be happy if the Nobel Foundation instituted a Nobel prize in computer science instead. 2024-10-08T19:32:43Z