2026-07-26T00:05:06Z https://nostr.ae RobJLow https://nostr.ae/npub1dxfpptm696ejdjun36sl8tpac20hs6z4jv92qp4jp5w7666mmq0ss2v5xz https://media.mathstodon.xyz/accounts/avatars/109/376/619/514/804/955/original/467ff4e62f4b8f20.jpg https://media.mathstodon.xyz/accounts/avatars/109/376/619/514/804/955/original/467ff4e62f4b8f20.jpg https://nostr.ae/nevent1qqstffr45trv30rd584yz5e9pgyf50g7zt0xfry3u8e5xmklzhk5xeszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7jqxuh4 In reply to <a href='/nevent1qqs9kj9nmxqj5mmqzqjd8frrassgke8j242cy99eruv5s62c5jd865c3u80pk'>nevent1q…80pk</a><br/>_________________________<br/><br/>Seems they could get round that by paying him to teach the course... 2026-05-29T19:58:55Z https://nostr.ae/nevent1qqsrawze0742dttsmjcw6qp99fzgr88x0qv06p4j44vqs6mxdxnp0wgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7rzr586 In reply to <a href='/nevent1qqsg2psw7aucgm439tu763njtfcedswkvcp09a2rzr8ypr5p2wufuugtzjp47'>nevent1q…jp47</a><br/>_________________________<br/><br/>I managed to get as far as a DPhil without any formal (sorry) education in the foundations of maths. The only times I recall it rearing its head were the passing comments in topology that Tychonoff&#39;s theorem needed the axiom of choice, and likewise in measure theory for non-measurable sets. 2026-03-31T21:19:07Z https://nostr.ae/nevent1qqspckdp3tujk8p9p8jawdkpszau5af2ymclnxljlla6dclppk23g3szyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7d85y4l In reply to <a href='/nevent1qqsf3t5p8aq85hm802mewf5dezyg37mh0q5w8u4hdctn4alm96f9xmgxs7j3r'>nevent1q…7j3r</a><br/>_________________________<br/><br/>I hope we&#39;re not in for some kind of &#39;purity test&#39; era, where if it ain&#39;t formally verified, it ain&#39;t really mathematics. 2026-03-30T07:06:11Z https://nostr.ae/nevent1qqs2qkdasmusthc4qmns8xrgmgcz3ffcaj4ujxnp30kyq7fryymudqszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7lr32r6 In reply to <a href='/nevent1qqswghwap603p9zs7vqjy9qeecnnrwj5uxtlnuuxahdng35rz0e78wqndwwtz'>nevent1q…wwtz</a><br/>_________________________<br/><br/>We&#39;re gonna need a bigger antimatter containment vessel. 2026-03-14T09:06:43Z https://nostr.ae/nevent1qqstuxkef7p2yp9rgk82vxka8xfd5d2q3agmh6pd7704c6apcvuxs0gzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7ag86da In reply to <a href='/nevent1qqs87veza0evam8tcufwxk9pxuzq776dexrzja4xrad04rnwmsda9estvtcx6'>nevent1q…tcx6</a><br/>_________________________<br/><br/>I hope this turns out to be less scary than it sounds! 2026-03-10T15:26:02Z https://nostr.ae/nevent1qqsgjwr3tjnu3a9phnf8l09g9djyc43fqhjf92epqkefxs4cl2wy0dszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp769vxuv In reply to <a href='/nevent1qqsfp7gc6xy83k36955nammpqvxq5lu06rhkstrhl8hwpccyp448fys2gcq9g'>nevent1q…cq9g</a><br/>_________________________<br/><br/>Worked for Biil Werbeniuk, after all :-) 2026-02-23T12:05:31Z https://nostr.ae/nevent1qqszht00fkyjwqd89tw6e4rhm7knpxax708cy0099j9pesrg53rp5pqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7sf4k4d In reply to <a href='/nevent1qqsq8wrwsyuw0s50kgnu5qcjjsj9ywvf3gt7jsla2kwyek2stptzkuc3r2swe'>nevent1q…2swe</a><br/>_________________________<br/><br/>It&#39;s a moderately subtle point, since it&#39;s one of those cases where trying to pass to the limit doesn&#39;t work: you can move to the rest frame of a particle moving at any speed up to, but not including c, where the procedure breaks down. But you need to have some idea of the mathematical structure to see what&#39;s going on, which popular expositions tend (more or less by definition) to lack. 2026-02-20T11:28:09Z https://nostr.ae/nevent1qqsrj7dv2r6jsqcx2dqtetk7efn6s3vmxp703cajd28kau4k0np2awczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7s4606c In reply to <a href='/nevent1qqsf5cvmuu5shqrunj652sz3zwnegenny704ktzdtlq7nsk8942w3egmn2ske'>nevent1q…2ske</a><br/>_________________________<br/><br/>And I thought the taped messages for your survivors in &#39;Things to Do in Denver When You&#39;re Dead&#39; was distasteful... 2026-02-13T12:04:53Z https://nostr.ae/nevent1qqs8vdllmf4gen0una9vck7d49y8clnkkpypptmxphfcdz43drt3cmszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp77c0fzr In reply to <a href='/nevent1qqs2n90pufwn5q96x0vhcxlqd33mtfvlahnx95hthu9wdp3ec85gh2gaavyv2'>nevent1q…vyv2</a><br/>_________________________<br/><br/>Yes - and it&#39;s consequently all too easy to write something that inadvertently comes across as dismissive. 😬 <br/><br/>On the bright side, I&#39;ve now been nerd-sniped into trying to understand Lagrangian mechanics a bit better - it&#39;s been ages since I thought about it. 2026-01-07T14:50:12Z https://nostr.ae/nevent1qqsx7g82l87xa39px3uqkqdtp3ddz4n85vptpfucffkh86wysrs2hwqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7spqtt7 In reply to <a href='/nevent1qqsp8et2auva89lrqpm9mrd22d4nf5v4hdysxn89qaxlp53jz0vrx3q86ss05'>nevent1q…ss05</a><br/>_________________________<br/><br/>This time I can definitely agree with &#39;sure&#39; - and no &#39;buts&#39; at all :-) 2026-01-07T14:44:38Z https://nostr.ae/nevent1qqszjs04xsmrc4xujyx6605szyge85akdx9v6rzg60dxxs4dhk640fqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7muh6rh In reply to <a href='/nevent1qqswtjmxazj90gln8r84y2pdn8mn2dy24uce9hrhzkmna5wxlpgm2jcu3g7ez'>nevent1q…g7ez</a><br/>_________________________<br/><br/>I wasn&#39;t trying to be slippery, but am trying to work out in my mind what I think about this, and what it means for the notion of force to be fundamental beyond a faint nagging feeling at the back of my mind which makes me not too happy with immediately identifying generalized forces with Newtonian forces.<br/><br/>And I&#39;m fairly sure that Newton&#39;s third law (each force having an equal and opposite reaction) is closely tied to conservation of momentum.<br/><br/>But, since I&#39;m kind of floundering about in my own mind, I should clam up now ans wait until you write the blog article, and then at least I&#39;ll know if I still think &#39;sure - but&#39;. 2026-01-07T14:29:50Z https://nostr.ae/nevent1qqsqn4273kl920zwwk7ew432zmewjq0ztt3cd9qngtk059hfyk80jlqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7r0v42s In reply to <a href='/nevent1qqsgrz097xfcgrj5u45e3tl7xd5fc9nu5kk45jdlms6vadceql4gm9gpw4wj7'>nevent1q…4wj7</a><br/>_________________________<br/><br/>Sure - but the generalized forces are derived notions (and not always easily identifiable as Newtonian forces) rather than the basic ones of Newtonian mechanics, and the conserved quantities arise from symmetries that are not intrinsic to the Lagrangian framework, so the action/reaction thing must be a consequence of symmetries imposed on the Lagrangian. I&#39;m not saying it can&#39;t be done, just that it looks like significant work is required - which isn&#39;t surprising if you haven&#39;t already done it! 2026-01-07T14:10:03Z https://nostr.ae/nevent1qqsxdr4wnyhvemls9l0lddv6c4cx5vg5v2a0vjmugu6gy22lwve5qeczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp77782ru In reply to <a href='/nevent1qqsvmv840xkrvj9lmld6ap3nnhfecee5ay6g4u4v6es6h3qynxt2kgs2e3a7y'>nevent1q…3a7y</a><br/>_________________________<br/><br/>&#34;I believe this principle is built into the fabric of Lagrangian mechanics&#34; That sounds like a hard thing to make sense of, in that force doesn&#39;t seem to have a natural/fundamental place in Lagrangian mechanics. At least, not as I understand it - though that may just be my ignorance speaking. 2026-01-07T13:43:48Z https://nostr.ae/nevent1qqsrn7w2vq332943ayevhyx427xhmtdu3h0hg26tpvw66ynr3pvv73czyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7ke9lzg In reply to <a href='/nevent1qqsdvau5ntnmd3vy5amt4ujvfgjpk0a04t0545e0fhwrmvm2jhr7u9saf47yr'>nevent1q…47yr</a><br/>_________________________<br/><br/>There must be some nasty subtleties lying around: for a start, there are uncountably many different initial states, but only countably many Turing machines, so in one sense it&#39;s entirely unsurprising that TMs can&#39;t capture the behaviour of billiards. (I guess the trick is to show that it can&#39;t capture the behaviour in an interesting way.) 2025-12-23T12:54:50Z https://nostr.ae/nevent1qqsrm2ltja6jj80ejcxjpstwcrgzkgagnz7k7avcj9znxz6weqg4kwszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7us65hs In reply to <a href='/nevent1qqsyqhqa84gnfszshlcrvs2vaa5lgrdnayfppny6rqqndu8yylvp7eqrk620m'>nevent1q…620m</a><br/>_________________________<br/><br/>Back when I had a web page, I had a list of pet peeves. High on that list was people making nonsense claims in maths or physics based on misunderstandings of Goedel&#39;s theorems. 2025-12-23T11:25:42Z https://nostr.ae/nevent1qqsrcnqj3tpmj37q9gw5ffrjzp5zzwc69mzs4zxsyv0z8qsfldxnjkszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7fq8rdn In reply to <a href='/nevent1qqsyreaaa4jqxnpyt4lc7cffwnnldgs5l36xajp7x8k980zggk2ycdcmld8dn'>nevent1q…d8dn</a><br/>_________________________<br/><br/>It&#39;s hard not to wonder if that&#39;s something to do with which people were attracted to move to Bluesky/Mastodon. (Or, of course, which people you choose to follow...) 2025-12-07T12:15:28Z https://nostr.ae/nevent1qqszhkxl5zcqyexxd7ry0eql8e9xysylhtjqukls5xmj4g6daxe899qzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7nw578z In reply to <a href='/nevent1qqsthzc7fdmrztz6q2drlmh74jcfq6ykl5hzas5kzn9rywxjz7zcy7ss26j50'>nevent1q…6j50</a><br/>_________________________<br/><br/>Arg. They really shouldn&#39;t confuse &#39;can be represented as a set of 3x3 matrices&#39; with &#39;lives in 9 dimensions. :-( 2025-12-05T11:04:42Z https://nostr.ae/nevent1qqs0c94chhc5egws7wgm5hymc3h83tykz7srhfe9d279yysgqrum2mszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp72r496z In reply to <a href='/nevent1qqs2pguffe63nw423srf3ee8efx6d7fjyka2a0rsjc8r28mn3vqe60ce7ekep'>nevent1q…ekep</a><br/>_________________________<br/><br/>Ah, thanks! 2025-12-04T13:29:33Z https://nostr.ae/nevent1qqsdyek3wxk30lqqck9hq8780xffsddytm8335va5jlfgfgh88pqwaczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7pky379 In reply to <a href='/nevent1qqsgv7wq5md5hn66fe6ddhxvyhjsfv7pw4ewtvlexpqn4h3lhqe267c32cker'>nevent1q…cker</a><br/>_________________________<br/><br/>Grumble. I did take a look at a visualization somebody&#39;d uploaded, but after it zoomed out a few times all I could see was a line. (But since I could see it, it must have been quite think really, I suspect.) 2025-12-04T13:16:33Z https://nostr.ae/nevent1qqsy4undzzl04dvmmxfzgnme48t8gze5e9zszfzx9ppntprvaw8cyygzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp70xm7qm In reply to <a href='/nevent1qqsrswd6wldutlvq7xnkt82znwxlq4l0shrp7n8q9uy50jk5vy62c0g63rh73'>nevent1q…rh73</a><br/>_________________________<br/><br/>Any idea how &#39;fat&#39; it gets during the process? 2025-12-04T11:24:23Z https://nostr.ae/nevent1qqsp6ptu8p8y8gk7h3vyg683z20r9vc28hp6qwzm03jyp6dq33nfjqgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp78x2w4k In reply to <a href='/nevent1qqsfwn20pm2jjlmpeh7j6fcng09w6w5c28ydtfqt5j4mfxkvur2hcpg2yc20a'>nevent1q…c20a</a><br/>_________________________<br/><br/>Let&#39;s go for only 6 in 10 hating it, so that a majority like it :-) 2025-11-30T16:22:34Z https://nostr.ae/nevent1qqs0999ueyjlwex7c0kquwqdwczxx08svlts7fs5kcjn2d3tsprduzgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7frezme In reply to <a href='/nevent1qqswvp6qvlyz2r550xj84rp03qdjcw784m8052grvkhym2rsmxza8hcg0az9p'>nevent1q…az9p</a><br/>_________________________<br/><br/>You just reminded me of the time a colleague told me about going to a talk promising an &#39;elementary proof of the prime number theorem&#39;. &#34;At last&#34; he&#39;d thought &#34;a chance to understand that.&#34;<br/><br/>He left thoroughly traumatised. 2025-11-24T09:28:03Z https://nostr.ae/nevent1qqsdlmg9hn5yzweluxad0ugpz85uu5drawwe86mp99dpthxvahw904gzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp73088yz In reply to <a href='/nevent1qqs079td449q4qnglum0qqhspx7lc5uf6f7htavj8n2xn09ksaqpfcg98eq9l'>nevent1q…eq9l</a><br/>_________________________<br/><br/>Some of us would settle for &#39;interesting&#39; :-/ 2025-11-22T22:20:30Z https://nostr.ae/nevent1qqsxfzsuf3n7mvkr7cejqrs3hp9h9acstaatwe66py2h09uwf7g00pgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7e4tp4v In reply to <a href='/nevent1qqs05yt2yvj664qrgkqp25p8dd0jxre38unjyrd0czet9nh9c7uqtsgz7uzwe'>nevent1q…uzwe</a><br/>_________________________<br/><br/>&#34;could one day&#34; doing some pretty heavy lifting there. 2025-11-17T13:26:41Z https://nostr.ae/nevent1qqs2w32zrg9wmazueqzctrgg48x5w02jh9x30ahaetrqsst8p3jrnzszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7kdqyhs In reply to <a href='/nevent1qqsfw6yanh4da203tgux6y737hax0xg65gnrfhwm87zvsdq037wy95qlap3uh'>nevent1q…p3uh</a><br/>_________________________<br/><br/>I&#39;d be careful... I think HP Lovecraft wrote a story about that colour. 2025-11-12T10:51:29Z https://nostr.ae/nevent1qqs0v5vcmeytu8e04y29yaymluj7nhz4hm0zlcuxutaxjyxncmuehzgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7lv09zj In reply to <a href='/nevent1qqs2mk2kfyqhxgnavjdu04stwqx34z7cp3khznfsy9vacn7dw4mrlegydfvfy'>nevent1q…fvfy</a><br/>_________________________<br/><br/>A very interesting book. I remember reading it (well, looking at the words in it) when I was trying to get to grips with quantum logic. Not exactly light reading though, or at least, not for me. 2025-11-11T14:26:19Z https://nostr.ae/nevent1qqs9ugzlqj9lxkk3v6d5pke0v7r2n8cwzpr8ymqsql30ctxlze46p3qzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7tphwws In reply to <a href='/nevent1qqsvl6jdspe77jcgs47c45fsgkujqshtq9w6e83ysg7kvsss6mtevnqtzc6rj'>nevent1q…c6rj</a><br/>_________________________<br/><br/>Well actually, that was Aristotle, not Einstein. 2025-11-09T17:06:18Z https://nostr.ae/nevent1qqsfpdp6a84szvngmmv38v87wpy09qmgqzs0737suce89twmexcmqkszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7fgykhj In reply to <a href='/nevent1qqsv9xckr8dftm4jw7lvh9uq9cwaq4d080stmfa60c05a90nzhvp7fc60kdg7'>nevent1q…kdg7</a><br/>_________________________<br/><br/>Maybe also a kind of reductionist assumption that everything (interesting?) can be broken down into a combination of binary operations, so it&#39;s all implicit. (Which might a bit like saying that chemistry is implicit in quantum mechanics - sort of true, but not usefully so.) 2025-10-30T11:49:51Z https://nostr.ae/nevent1qqsxlea9l34fn2uefz0c8yz42xuzzqhawmkkj8yar3dm7zhlzf28y6gzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7eegt76 In reply to <a href='/nevent1qqs2u3gdnn3mx83g330tks49g29dn6zmslwzq2en4f8sve8v0xxyqssxn26xx'>nevent1q…26xx</a><br/>_________________________<br/><br/>This is maybe politer than I deserve for jumping in in the middle of a conversation without checking what&#39;s already been said 😳 2025-10-27T21:44:23Z https://nostr.ae/nevent1qqsf9tf54zjt9dpaj9n5amvqmjmnv47z488ngnl6gfhpxdqq9x66grgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7kuj463 In reply to <a href='/nevent1qqs9kmztuvmdrzlx3pr9g80fla2quhmhhyuty24wa8wcw3raf5lq0dq0443p6'>nevent1q…43p6</a><br/>_________________________<br/><br/>But couldn&#39;t you also just invert the usual stellar collapse (on account of the laws of physics being time reversible)? Then you&#39;d have a white hole that spews out matter with empty space to its future, and no black hole.<br/><br/>i.e. turn this upside down.<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/448/272/780/156/792/original/e63b91294acdeb4b.jpg"> <br/> 2025-10-27T21:39:54Z https://nostr.ae/nevent1qqs2a0vt8q2zm6ntmdkdstftj3t0cca36p54gj3ufdgxz0vezhnlclszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7gxcstu In reply to <a href='/nevent1qqsgntuf6xuncmzv2hl3eywknsqn2vjcz7e6gkxe9xjag83jxx0qftqr400u7'>nevent1q…00u7</a><br/>_________________________<br/><br/>I heard it claimed (and it sounds reasonable) that the absurdly high prices on some second hand books are because they&#39;re being used in a money laundering scheme. 2025-10-15T14:50:09Z https://nostr.ae/nevent1qqsq4exxq0hwtpk4077uuftwwrdyg946s60gc4dtcvmdncrt8rf6dgszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7nn3urw In reply to <a href='/nevent1qqswusgljftcmtf7z5hv7fc48fv6hp867p7qppa09fk6s3he2j5840qjq96gz'>nevent1q…96gz</a><br/>_________________________<br/><br/>A tsunami of intimidating maths... 2025-10-09T10:17:21Z https://nostr.ae/nevent1qqs074ktfup66dn9c7258qcup2tvgqadsmufgrplf75vfvn2htu355szyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7hfllt5 In reply to <a href='/nevent1qqszzsxneskdcrcqd66hzhwt5k7nuelzdrfdupdm4ke2xfujrx90mvqw6c50r'>nevent1q…c50r</a><br/>_________________________<br/><br/>Not having an exam looming on the horizon makes a big difference to how much pleasure you can get out of organic chemistry :-) 2025-10-04T12:37:43Z https://nostr.ae/nevent1qqswac7fm25hzhwxhm6hghfuaznu645zm3lxz39v6zuenph5a4fahnczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp73nacl8 In reply to <a href='/nevent1qqszycuqkytqgunjtm6tkq5yljt0vh9twyz2gkqnw9hrgygdt5nsrzsew9yzn'>nevent1q…9yzn</a><br/>_________________________<br/><br/>That would be a very safe bet :-) 2025-10-01T09:52:04Z https://nostr.ae/nevent1qqsgtcz54gq2prpt66200tpxpadw4shq6dxwlvd27ttlxr8jc9dxu3gzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp76llnjf In reply to <a href='/nevent1qqsvzzngcjuwpw668y7v5fp8c4026re4qq0rpt2zlrx8czdvymf42rcpy54cx'>nevent1q…54cx</a><br/>_________________________<br/><br/>Decided to take another bite at this stuff, and hoping to have at least some idea what forcing is before I crash and burn..<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/297/690/117/960/760/original/ba763e81ec2e41fb.jpg"> <br/> 2025-10-01T07:19:54Z https://nostr.ae/nevent1qqsyrne5prksalt47jpwzr0kf6ku3rw6k0nmn6ak9lfmvgda7k3lj0czyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp788jjpq In reply to <a href='/nevent1qqsdmlq76ucm5sans2mh6aqj36pslvqksvqckz8qpnyu77rjjh3q47s8kp2tt'>nevent1q…p2tt</a><br/>_________________________<br/><br/>Argh, I think I was talking nonsense. By the same calculation as in normal Schwarzschild, we must have<br/>\[<br/>\frac{d^2r}{d\tau^2} = -\frac{M}{r^2}<br/>\] <br/>for a radial timelike geodesic, so for negative M the particle is repelled harder and harder the closer it gets to the singularity. After a finite amount of proper time it must reverse and head back out again. <br/><br/>And of course, no orbits, so no precession of perihelion. 2025-09-28T19:44:41Z https://nostr.ae/nevent1qqswqlrsr004pd8446vsksspplumg47e92hph7e5gc2dxq945u6tyqczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7lv4k5k In reply to <a href='/nevent1qqsqsguf844ede9yay557qdae50zy4pn3twrnu7n6p9ngj8wm9lthfqx3v88t'>nevent1q…v88t</a><br/>_________________________<br/><br/>I think that infalling radial geodesics should get to the singularity, but others will go near then come out again, a bit like for a point source in Newtonian gravity. (Of course, since exactly infalling ones are very scarce, even if I&#39;m right about this, you can still argue that the central singularity is physically inaccessible.) 2025-09-28T15:22:12Z https://nostr.ae/nevent1qqsfq652mk76s25csmsd63sltxz7w3araesa2muycez8jfhsnhvuw8gzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp77wc22v In reply to <a href='/nevent1qqsw4unv99h0rczsk48dqp877435mr6l774rwhuz8jh46chpcgcwj8qg50qtr'>nevent1q…0qtr</a><br/>_________________________<br/><br/>I haven&#39;t though about it enough yet either, but it seems pretty plausible that (in the usual spherical polar coordinates) since the connection coefficients are algebraically just the same as before, but there&#39;s no Schwarzschild surface event horizon at which t and r swap over which is spacelike and which is timelike, we have a timelike naked curvature singularity at r=0 that things can fall into, surrounded by an asymptotically flat space-time. So if you&#39;re reasonably far away from the singularity, gravity behaves pretty much like Schwarzschild, but with some sign changes (orbital precession, angle of light deflection) but if you&#39;re close in things are rather different in ways I don&#39;t propose to work out before sending this.<br/><br/>And of course, now there&#39;s no Cauchy surface or well-defined initial value problem, so a lot of stuff must fly out of the window. 2025-09-28T11:56:25Z https://nostr.ae/nevent1qqspsvsnnvh5xr5jgzqkhyd2w20vqpl04q8tcluxulrqlzqt84ghhtczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp77gq8fu In reply to <a href='/nevent1qqsfeqxx6h3pc8ch0zvgkfhfvkdwkdtf6937mhjuzezswf9w3y383asxp7dy8'>nevent1q…7dy8</a><br/>_________________________<br/><br/>I seem to recall that it&#39;s got undesirable global properties - in particular, it&#39;s not globally hyperbolic, and has a naked singularity. There&#39;s more detail than I&#39;ve chased through in<br/><br/><a href="https://arxiv.org/pdf/2001.11376">https://arxiv.org/pdf/2001.11376</a> 2025-09-27T12:36:22Z https://nostr.ae/nevent1qqsg345rlwnvgu2t95k02xq5jldhw3f463al7trjljnr4myylff2m8czyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7gzar94 In reply to <a href='/nevent1qqswtrwancfrdqvp39el87y83dh52ss2ggs2dz2nqz7zavx9lrru9yckw3w3p'>nevent1q…3w3p</a><br/>_________________________<br/><br/>&#34;True is top is ⊤ because truth implies anything; false is bottom is ⊥ because anything. &#34; <br/><br/>I think something went astray between brain and typing fingers there. 2025-09-25T07:40:51Z https://nostr.ae/nevent1qqsyngl49tm70j22ur20nq85nn02w7lns80r5mk0tr0hxnlf7kty7ggzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp74q4t83 In reply to <a href='/nevent1qqsvhu92pr4qr54rj00sj0aa60dymf5anm2rj08tmm7rekaledvq59c2a6rvz'>nevent1q…6rvz</a><br/>_________________________<br/><br/>I sometimes feel like there&#39;s a tiny Platonist living on my shoulder whispering &#39;But *really*...&#39; in my ear. Maybe I need to cultivate a formalist on my other shoulder. 2025-09-21T11:45:45Z https://nostr.ae/nevent1qqsyp0c7qqpqfe4xq762wf89ce74ctt8guh2ncwxk4vqjrfra8r8kgszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7rgse8d In reply to <a href='/nevent1qqs0x5wuw7644dwwwwk0pktaty4rpu5frf55l53gfkreelnfdltue4cu6dvhf'>nevent1q…dvhf</a><br/>_________________________<br/><br/>I kind of know this: I&#39;m just also kind of uncomfortable with the notion that a very large cardinal might be &#34;really&#34; countable. I know just enough model theory to get myself into (self-inflicted) trouble. I suspect it&#39;s a matter of getting used to it (as von Neumann said :-)) 2025-09-21T10:42:38Z https://nostr.ae/nevent1qqs9htjumagptn7anrvs8w4z7jp88dmr59pfrhrkj8d56w6kzgqmjtgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7gqf6qx In reply to <a href='/nevent1qqsralhwhrhpa2n4j3dy6u83xqrtuznm5u8u040420jvccd86l3xwtguske3w'>nevent1q…ke3w</a><br/>_________________________<br/><br/>Here is where my head explodes (or possibly implodes). The cardinal has to be really, really large - but the Skolem-Lowenheim theorem tells us that it can still be (externally) countable. I suspect I&#39;m just not cut out to understand logic and set theory (though I would like to). 2025-09-21T09:59:52Z https://nostr.ae/nevent1qqs25nftdxgd3egx75h4xahwvs92nycagw7tfhqzahc36dgzzak6unszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7whf737 In reply to <a href='/nevent1qqspfg2mrnyfrsgplg5dwkttqlpp3699ugx4cqx8tte2q88jlsn9kmc2w8qr7'>nevent1q…8qr7</a><br/>_________________________<br/><br/>A tiny bit of information in <br/><br/><a href="https://en.wikipedia.org/wiki/Axis_of_evil_(cosmology)">https://en.wikipedia.org/wiki/Axis_of_evil_(cosmology)</a><br/><br/>As far as I know (which is not very far) there&#39;s no compelling evidence for cosmological anisotropy, where by &#39;compelling&#39; I mean &#39;generally accepted&#39;. 2025-09-21T09:02:47Z https://nostr.ae/nevent1qqsyylglyxrj92rt0kh9k5en522uu2cjrxnyp8k78hugvydn5n4lr9szyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7mnj42j In reply to <a href='/nevent1qqs9p50t2tppd0duk9avgmramxu6qsh9fhvxkdskql8thekuqhfsqwsfxu25d'>nevent1q…u25d</a><br/>_________________________<br/><br/>I&#39;ve only come across &#39;bottom&#39; for ⊥ and &#39;top&#39; for ⊤. (I&#39;m pretty sure this is standard in logic/Boolean algebra, but then I haven&#39;t seen them in other contexts.)<br/><br/>Also, the LaTeX commands are \bot and \top respectively, so that should be enough reason for everybody to stop calling them up/down and down/up rather than bottom and top. 2025-09-19T15:35:36Z https://nostr.ae/nevent1qqsrlp67jsqwlmeuknnxmlttsxxh8hml4wjqgevj5qxctcp3vr48lsqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7f5vq4z In reply to <a href='/nevent1qqsrymep8r484pwkemdxf9lvf2wpch4j3q3gywtfv447chatdp2h58cg057en'>nevent1q…57en</a><br/>_________________________<br/><br/>I remember trying to read Segal&#39;s cosmology book years ago, and failing to make sense of it. Is it (has it ever been) a serious competitor to the standard cosmology? (I ask because of him being your doctoral supervisor---and I may have asked you this before, but can&#39;t remember.) 2025-09-19T10:04:23Z https://nostr.ae/nevent1qqsvy7agkpldzkt825uflweceh98z5mqwwaq9j7nhwuhceunpsq6h6szyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7w7q9zc In reply to <a href='/nevent1qqsphcpdndvryf5hwdu74czvuv2pam6ulr3nmv0fjv7hdqjfnndc0esh4gjcd'>nevent1q…gjcd</a><br/>_________________________<br/><br/>Oops. I wasn&#39;t actually *trying* to make a claim that was wrong in as many different ways as possible, but if I had been trying, it would have been a good attempt. 2025-09-18T09:02:07Z https://nostr.ae/nevent1qqs88y83r7hqqqvn39jsja2qy30g5gc4hu7egqh38zwqc632tzgef7szyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp703dmzc In reply to <a href='/nevent1qqs8vqd9umnw2fx5j8wshkczkqhfjzeup0r69sth6su29fntp94f40grmugug'>nevent1q…ugug</a><br/>_________________________<br/><br/>We have to have some faith in humanity, or at least that segment of it that might see that little bit of whimsy. (Though on twitter I&#39;m sure I&#39;d have at least one person yelling that I&#39;m a complete idiot and explaining why it&#39;s wrong.) 2025-09-18T06:08:11Z https://nostr.ae/nevent1qqsrvk036lqlu8svw6em6dt9ameq6dkmrx5wcrsthxwkath5crg3yxczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7r3cl4s In reply to <a href='/nevent1qqs9jexlgn92a3dkmn3hx8h56zfa38yqv88f6mjuss40743en2pvwlgwz539e'>nevent1q…539e</a><br/>_________________________<br/><br/>&#34;In 2017, the magnetic fields near its event horizon were spiraling around one way. By 2018 they settled down. But by 2021, they were spiraling in the opposite direction! &#34;<br/><br/>The galaxy must have crossed the universe&#39;s equator... 2025-09-17T10:00:55Z https://nostr.ae/nevent1qqspl34wgw8jqm6pd5g56d2v766qetzq0la9h89dss3gz5x0fdjchfgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7s2rrmh In reply to <a href='/nevent1qqsydxjj2k7l4a9slyngr0d0j9ce2zlvm7nmd3hzegp5p4p8xtjck4gsqexrd'>nevent1q…exrd</a><br/>_________________________<br/><br/>What I&#39;ve found on Bluesky is that when I follow people I see a lot more political content than I&#39;m interested in, so I tend to use feeds more (eg #Mathsky for maths stuff). <br/><br/>Also I usually don&#39;t follow people on Bluesky if they&#39;re posting just the same stuff I see in other places, and I doubt I&#39;m alone in that. 2025-09-14T07:46:22Z https://nostr.ae/nevent1qqstrl0tt68glawsmxcfaufyehcw7estdsym0580ylf3vl6azsa34mgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7e7jldr In reply to <a href='/nevent1qqsq8prvv8ch7dq54atu6lw840e65uzr7mg9pxkhaylnzfp3lhv9hfc978fsq'>nevent1q…8fsq</a><br/>_________________________<br/><br/>Sure - I just find it interesting that you can (kind of) do cosmology on a surface of revolution, and there it&#39;s essentially Clairault. (OK, you have to use the right metric, and trig functions become hyperbolic ones, but if you squint hard enough it makes sense.) 2025-06-20T10:32:32Z https://nostr.ae/nevent1qqsxjrw8smlcfup87rwk9emfdch5k82ljxa59e9czegkj973wyj0cfqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7te5tfm In reply to <a href='/nevent1qqspp9hhrurwkr66c7lq3yek2u5clttkz74v2rum8y6mxc3mjykf0zqprxrp9'>nevent1q…xrp9</a><br/>_________________________<br/><br/>I think It&#39;s all Clairault&#39;s theorem, really. 2025-06-20T10:23:30Z https://nostr.ae/nevent1qqs9cmfs7xhp749gemnwvwxx04gf9c8ypwyh28fkvfvhwuperznv06czyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp762hnvx In reply to <a href='/nevent1qqs99z607f0jptjwxm0rp53yh9n53pfmm7feftyzztsqsjva6vrmxeqtggh7v'>nevent1q…gh7v</a><br/>_________________________<br/><br/>As any fule know, they&#39;re doing dismal science.<br/><br/><a href="https://en.wikipedia.org/wiki/The_dismal_science">https://en.wikipedia.org/wiki/The_dismal_science</a> 2025-06-05T15:55:32Z https://nostr.ae/nevent1qqs8qeaf8h4zwtdhn4e08tppxp6kxxgff7qzplvtvrz4nvt62fp560szyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7azaynp In reply to <a href='/nevent1qqsfq7qhmthp573nyq9gd45cxmy5skjg2yk9ll8f0qu9lus5ampsdacdyc38w'>nevent1q…c38w</a><br/>_________________________<br/><br/>Yeah, I remember trying to read some of Wald&#39;s work in this area some years ago. I think I had an accurate-as-far-as-it-went-but-it-didn&#39;t-go-very-far fairly vague idea of what was going on, but never closed in on the detail. <br/>That said, the whole endeavour - to extract the equations of motion of an idealised point particle - might be open to criticism along the &#39;there ain&#39;t no such animal&#39; lines. You pays yer money and you takes yer chances. 2025-06-05T12:42:08Z https://nostr.ae/nevent1qqs9m3fwvj57zpmysg086eu0wdl07u0tv2uwzwuzvpgcunn8fy2lf3gzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7exhg0p In reply to <a href='/nevent1qqsdlgy7pfa23ysxrxy8fgpy4xrkd96v5x7tkdgaefnv9uz8hf3hsacrgu5vr'>nevent1q…u5vr</a><br/>_________________________<br/><br/>Yes, you&#39;re right, I should never have been impressed by the glibness of LLMs. My mistake, and I&#39;ll try not to make it again in future. 2025-06-04T06:40:23Z https://nostr.ae/nevent1qqs093t9ckkvsf6djwrsamuvy69ecus6k8q4fnqtlzs5qe36edc4jlczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7etk5q5 In reply to <a href='/nevent1qqsfev5dwzqapug4cg6mamg67uhq46trl6ryxgxcdec7rhyqrxp5u8c8klcat'>nevent1q…lcat</a><br/>_________________________<br/><br/>Yes, what I meant was that their mistake was writing total nonsense instead of abstract nonsense. 2025-06-01T13:27:03Z https://nostr.ae/nevent1qqsd5dqppuy7vmgcrqmj0t27dmjlgpqpyf2pel8mysl227u0faj5j7gzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp78tj4sg In reply to <a href='/nevent1qqszd479vq9xr8vgp7wc4hp7sl2d8z8gjlw6s6kmda3zgd9m5l87m0srdw6d3'>nevent1q…w6d3</a><br/>_________________________<br/><br/>A small mistake: it should have been abstract nonsense, not total nonsense. 2025-06-01T13:23:22Z https://nostr.ae/nevent1qqs93pht4dk3ay3nazu5w5tz447zuhea7lun5z0ez2574q9e695fppczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7nvc6w7 In reply to <a href='/nevent1qqspzacfdcs44rqfwhjczmt356zqdhfzwm2f3x4wqnjuhsxcylkgf0c72fw09'>nevent1q…fw09</a><br/>_________________________<br/><br/>I know I&#39;m older than mud, but I kind of like the fact that I can slow down at the hard bits and re-read until it makes sense, if necessary with a kind of spiral approach. <br/>Yes, I know videos can be paused and rewound. It&#39;s not the same. 2025-05-15T12:17:10Z https://nostr.ae/nevent1qqspag7fzpf4ae677yz2pyyckll6tpk6kds3hw4xx6dx8hadx604llczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7cq2y5h In reply to <a href='/nevent1qqs0atxl4cneedkt4560mn9u0hrx4ghq3887f20u0klz2w80qzv98dcfpyj6m'>nevent1q…yj6m</a><br/>_________________________<br/><br/>It looks a bit like earlier stuff of his (which I hadn&#39;t initially realized was the same guy), rational trigonometry. It&#39;s not that it&#39;s wrong, just that it doesn&#39;t live up to his claim of being a better way of doing trig. Proof (if proof were needed) that you can be a professional and still be a crank in (at least some aspects of) your own field... 2025-05-05T18:29:31Z https://nostr.ae/nevent1qqst5lm670gt2q9s50fxj74qcg2n5skdmrqv62p7u83qse79kz3ayfgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7jvtztx In reply to <a href='/nevent1qqs8emfjh324yll4eagmmeln6sfjcy3a4r8a6qzjx5pj6nmnm3v2v3gxz0u7h'>nevent1q…0u7h</a><br/>_________________________<br/><br/>Hype can make it around the world before informed commentary has got its boots on.<br/><br/>(I suspect that these articles are eating and regurgitating each other, without anybody actually looking at his paper.) 2025-05-05T15:05:36Z https://nostr.ae/nevent1qqs9vedc97ey8vq3rrveymjm7r3mg8fa788ewtyqpku4t53sucsnstqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7vg2zqg In reply to <a href='/nevent1qqstghjvdhpgwf587wmyzcpxy5nvnnqf85w8sn6mckwa4ez98zmp3ucgt36u6'>nevent1q…36u6</a><br/>_________________________<br/><br/>Is it nonsense though? I mean, any more than any other strongly finitist approach to maths. I ask because I understand even less about finitism than I&#39;ve just said, and I said nothing... 2025-05-04T15:16:55Z https://nostr.ae/nevent1qqsvm9ar80nyvssvfu7g0whpq6cf6sfhlgaenp94pfwt98yln6udr6czyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7fqgp0d In reply to <a href='/nevent1qqsr520cuwc072rxzuh7evztuh6kneme4lu0deyndljsx3e4ew75nfch67mte'>nevent1q…7mte</a><br/>_________________________<br/><br/>I think I actually started to understand tensors a bit when I realised that the &#39;transformation&#39; rules were actually a very unhelpful way of saying that tensors don&#39;t depend on the choice of coordinate system. 2025-04-27T13:53:51Z https://nostr.ae/nevent1qqs9ft2nfz5pdq8m74kmq3l0uz24mc8w3ncue3aalcyskhrw7z8de2czyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp76en7d8 In reply to <a href='/nevent1qqsv3xr0rvgwsd34aepp0rjuk97x80surfyeyhftgemmy0tlrszp07csrqty3'>nevent1q…qty3</a><br/>_________________________<br/><br/>That&#39;s the catch, of course. What people (think they) want and what they get can spectacularly fail to coincide. 2025-03-19T10:12:56Z https://nostr.ae/nevent1qqsvfgnk57lx93w74uxvx70vqgw0fq9npgs9sp4mxnue2wanmwjt4sczyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7fn2qy7 In reply to <a href='/nevent1qqs2vlqx5wea07ryw0jn03mz9tfxf7qd854cmqrypmz47sycq7yq23s5vm8le'>nevent1q…m8le</a><br/>_________________________<br/><br/>I strongly suspect that a poll would show quite a lot of people would prefer a benign dictatorship to a democracy. Of course, that word &#39;benign&#39; is quite important there. 2025-03-19T08:13:49Z https://nostr.ae/nevent1qqstasp576prmulrhn9w3wlhlrn42fys8ryf8d3c2w5ud8kwf96atjgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7s52zlc In reply to <a href='/nevent1qqsq5xcxm00j3v8j48ylhj8ayk94n7v894n9tkwpkasm9sc4eu5lpeg5dss5u'>nevent1q…ss5u</a><br/>_________________________<br/><br/>I (very) vaguely recall it was something to do with the geometry not having sufficient smoothness properties, so that there is no uniqueness theorem for the time evolution. 2025-01-05T19:29:05Z https://nostr.ae/nevent1qqs2e5grgp05huz967fpqw55yfghkq2nsk37wmltmj82ktal6ulv9pqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7gqlqj5 In reply to <a href='/nevent1qqswcgk7w2qcdwpmfu3mky4kyj0paeyz0q7an9mphjhj6nyhwrlam6cv82r45'>nevent1q…2r45</a><br/>_________________________<br/><br/>I think you&#39;re being unnecessarily fair here. But I can&#39;t really disagree with any of it. 2025-01-04T19:32:48Z https://nostr.ae/nevent1qqsfax5d7f9ujr60r7whdp6ad28wmu5zeh223cm5uw46dr2v4k47fugzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7px8rkv In reply to <a href='/nevent1qqsrllmw3fwrnzvahtvppejhlxcdq5q3kmrrg9z3wceptzypz862rrgrh5chm'>nevent1q…5chm</a><br/>_________________________<br/><br/>The big difference between them is that relativity makes sense and QFT doesn&#39;t. (This may be biased by my long standing utter failure to understand QFT, of course.) 2025-01-04T15:14:58Z https://nostr.ae/nevent1qqs0afp78e3p7nrqysw0lc6fa38maeja7dfau609l72k9ngr4wadmfgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7mdwkwm In reply to <a href='/nevent1qqsvy9vvhjhmp5dqns8wejfu4e88sugex0megnsduv8xcy4j9ztcdpchawa4s'>nevent1q…wa4s</a><br/>_________________________<br/><br/>A lot of the time people believe what they want to be true. I guess these people want to believe that they&#39;re victims of a conspiracy. 2024-12-17T18:42:23Z https://nostr.ae/nevent1qqsvw5ex700r8da9r9d6nyt7n7p3jgm9z7val777nkvvnc6favtna6gzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7jvyznn In reply to <a href='/nevent1qqs9dpthvfvvraaz6yh579kmv7s3cgs0w0ytyfdeyg94yqkf627kzzgpqn7d0'>nevent1q…n7d0</a><br/>_________________________<br/><br/>I wouldn&#39;t be entirely surprised if <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1wspt7d66rkz4ekxqjp7ndssvzlxqz2ehaz6f8mjv3krr2ew5ujnq93rhgk" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>Thony Christie</span> (<span class="italic">npub1wsp…rhgk</span>)</a></span> had a blog post (possibly even more than one) about this he could point us at. 2024-12-15T09:16:39Z https://nostr.ae/nevent1qqsve3sumh30gmyucu8fncqlum9mhx2cwht8ft37lqetdgge8fef7qqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp70t44sx In reply to <a href='/nevent1qqsf57qlyesveqjkfex69hca53sxj578c2krfk29tvjys2xs0ttxfzcka2fvg'>nevent1q…2fvg</a><br/>_________________________<br/><br/>Alas, incompetence prevents me from having a proper opinion. 2024-12-06T17:22:46Z https://nostr.ae/nevent1qqsfwua74pq6p3updr47jw5u3ag6vtn5u2k2wfkd6ugeq6hgp95h5zqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7r8wat5 In reply to <a href='/nevent1qqsy3rz2syy5uf2ztd7qdt8v4tpjmf5g2f0g07z04s4fpgf8tkes9fc8mvhcy'>nevent1q…vhcy</a><br/>_________________________<br/><br/>I am confused (not that that&#39;s unusual). If you have an isolated (let&#39;s say spherically symmetric) object, and classically it sits in a static, asymptotically flat space-time, then don&#39;t past and future null infinity have to disagree about the vacuum like they do in a Schwarzschild space, so that it will also radiate (but maybe much more slowly)? (It doesn&#39;t help my floundering much that the original calculation is based on a static space-time but concludes that there&#39;s no such thing...) 2024-12-06T17:15:08Z https://nostr.ae/nevent1qqswhc8xven8jqv4rzwz8hjpnjha8w7nyhschwthxw2yv3jxq543xrqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7y96n8f In reply to <a href='/nevent1qqst7xyf3eddeqt970gu2v8f9gep25akpp0xk2tg2mv20kujfpt8ywgysyewn'>nevent1q…yewn</a><br/>_________________________<br/><br/>&#34;In short, I don&#39;t think being a math whiz is just about math being easier for some than others.&#34;<br/><br/>This is, I think, an important point. Some people get farther faster for the same effort than others - but if you give up easily then you hit your ceiling sooner. Aptitude and determination both matter. 2024-12-04T18:30:02Z https://nostr.ae/nevent1qqsd3z5fze68rgre9qvr4grpggnw9wrjvsd3nhmn4p568as3lf5saggzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7wln7fl In reply to <a href='/nevent1qqsgncw62pgfxnv4um77nq53znra0twspu27eepyplsqg5u55yv5qqcm4r6z5'>nevent1q…r6z5</a><br/>_________________________<br/><br/>Kind of weird, because you can see the white hole (but you can&#39;t go there) and you can&#39;t see the black hole (though you can go there). 2024-11-25T08:32:15Z https://nostr.ae/nevent1qqsys6q5lwt7ty5r3e9quk2xlclhg87vwqd5v3yt0j6h8mfnup6zwtgzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7np8rmw In reply to <a href='/nevent1qqszhhskzt229n000aynpywcy7z3xyhlaquv7jpsexrn9mew2z7yzacre3wf8'>nevent1q…3wf8</a><br/>_________________________<br/><br/>Oh no! I&#39;d no idea that had happened, that&#39;s terrible. 2024-11-24T09:19:55Z https://nostr.ae/nevent1qqsff2hz9jlvs5t6m02ks8yrcqu38t8c2laf9svy6h0ty6f5lp6lrngzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7caqftc In reply to <a href='/nevent1qqsfjnav5n3p7gn2gxsjrhh5ulwprse0tkrr9m57j9wevfxdeuhespspvsg4t'>nevent1q…sg4t</a><br/>_________________________<br/><br/>It&#39;s well worth going to Wald after MTW (or some other first GR book). The effort will repay itself. Wald&#39;s semi-popular book &#39;General Relativity from A to B&#39; is (I think) an excellent non-technical approach to give you some kind of orientation for the technical literature, and well worth looking at before gritting your teeth and braving MTW.. 2024-11-23T21:33:13Z https://nostr.ae/nevent1qqsrjynskw2cz7ddaspctdtg7wux9znwup4jaal4zt5sc2gcuc35tugzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7a9c4ru In reply to <a href='/nevent1qqspejjsrhs4ts454hdj7jy4dg86z3m59napezjlwpt0y09akecjq5c6pxe4l'>nevent1q…xe4l</a><br/>_________________________<br/><br/>This is why I have problem with the firewall idea. (I&#39;ve tried to understand the justification, but all I hear is &#34;mumble mumble boundary conditions mumble mumble and then a miracle happens&#34;.) 2024-11-22T19:38:21Z https://nostr.ae/nevent1qqsduxkf93d0zud4jqk36y6ewtaejjl3fej5e3rnp7gkwdpdkxg5vsqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7gq7kzl In reply to <a href='/nevent1qqswt0ewuvg3hwrh9r2u4r2yfq0wue6xmys9gs3jmtvrzwwsmfqxagg97aru7'>nevent1q…aru7</a><br/>_________________________<br/><br/>Well, it might not be top of the list of things to worry about:<br/><br/><a href="https://en.wikipedia.org/wiki/Seveneves">https://en.wikipedia.org/wiki/Seveneves</a> 2024-11-21T19:43:58Z https://nostr.ae/nevent1qqsf533wtxwt0yp6c9mx0c3asasuasa3upkgcvy4yhzyc3zy7nqfuaqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp77zzl0u In reply to <a href='/nevent1qqs0m4gwv6n92ge3tawfutkdn8tpx5kq29sxm2kvett84kly9equm0cang08u'>nevent1q…g08u</a><br/>_________________________<br/><br/>So cool, isn&#39;t it! 2024-11-21T19:24:48Z https://nostr.ae/nevent1qqs0q6k285hasqvaajx7wwqe0y6d5mrwz40w6rurq2gqpz8gnj4knqqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7ktzjze In reply to <a href='/nevent1qqsvkn50svv7n8qns4hfxtg2whequ5jkm3x0ggesz96jq5kpufq9aes8rsl0t'>nevent1q…sl0t</a><br/>_________________________<br/><br/>Just to add some quantitative pedantry, the tidal force due to the sun is about half that due to the moon, which is why spring and neap tides are so different.<br/><br/>(I still remember how surprised I was when I first did the calculation to see the relative sizes of the effects, so now I take every opportunity to share the information, however marginally relevant it might be.) 2024-11-21T18:58:58Z https://nostr.ae/nevent1qqsdpz380r2rap639v0el9qzjday67v6p0gzhqg59l4na0h9h02hxeszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7wfut4t In reply to <a href='/nevent1qqs0mrh5gd6nruht75hnf85f8580vsskgwfjvaw3st7hf04z6j4xafqefeayw'>nevent1q…eayw</a><br/>_________________________<br/><br/>I&#39;m sure I remember one of my physics lecturers claiming to have seen a paper titled &#39;Degenerate star has dwarf companion&#39;. But now that it&#39;s many years later and google exists, I&#39;m sad to report that I can&#39;t find any such thing. Maybe it was just a paper he wanted to write. 2024-11-11T21:23:17Z https://nostr.ae/nevent1qqsg8nmr8rly0clyl3dpz5nwmhludp5wzjxywpf8rq4mfasp8rltl6szyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp762qpxk In reply to <a href='/nevent1qqs05j4uwkm98ye2z2ahjq73nkwvv0jwh4yuetzk4z8pkpwx7eknz0s8yj363'>nevent1q…j363</a><br/>_________________________<br/><br/>Yes, I just took a look. It reminds me of my old suspicion that schoolbooks which insist &#39;there&#39;s no such thing as centrifugal force, it&#39;s centripetal force&#39; have a lot to answer for. (To be fair, when you start thinking harder about Newtonian mechanics you realise that the elementary treatments do gloss over quite a lot of hard stuff.) 2024-09-18T20:11:49Z https://nostr.ae/nevent1qqst624rpqxvyluqe6whs55204uu5xezmlz3j7xv3r4uyunaacsjprqzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7ky38d4 In reply to <a href='/nevent1qqsg55tg9qqzxcxjz38u9rts8qsazr9vdjz4u5vkehj6sfzyu3rjptsuhcedx'>nevent1q…cedx</a><br/>_________________________<br/><br/>Just to be contrary: when you&#39;re sitting &#39;still&#39; in the chair, you&#39;re accelerating at about 9.8m/s/s, and when you jump off it and are in free fall, you aren&#39;t accelerating at all. (Well, a little bit because of drag.)<br/><br/>The difference between the Newtonian and Einsteinian pictures is conceptually huge, even though for almost all practical purposes equivalent. 2024-09-18T19:42:32Z https://nostr.ae/nevent1qqsyxtnw2xvh0zh043u0gxcytlm4767hru2xzvccuzk4h05r49cvhygzyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7s083zn In reply to <a href='/nevent1qqswg0g7s62z6aa490xcrh0c4hrg5yq2pkpj2rchwyjpmfqszdvdphqph2w0w'>nevent1q…2w0w</a><br/>_________________________<br/><br/>I tried, but to be honest I found it really hard going. For somebody complaining about other peoples&#39; assertions, he seemed to make an awful lot of his own, and too much of it just came across as crotchety (at best). I have no doubt his computations are correct, it&#39;s what he says about them that is really hard to follow. (And the singularity theorem proofs have been looked at by people much more careful than me without anybody pointing out lacunae.)<br/><br/>I&#39;m mostly now waiting for the dust to settle, and trying to to dig myself into any holes about it... 2023-12-21T20:54:18Z https://nostr.ae/nevent1qqsdchvlzwkld8vgq58h3jh5274y8e9m5v9lnqjpm8rfh3sregrp0uszyp5eyy900ghtxfktjw82ruav8hpf77rg2kfs4gqxkgx3mmttt0vp7a0jva2 In reply to <a href='/nevent1qqsxe2wlm3mgh3v2jq046udfc8txrrapgfxy2ch83xr3vmqa523ulug4n6yct'>nevent1q…6yct</a><br/>_________________________<br/><br/>I found it particularly strange that he says in the abstract that Hawking and Penrose just claim that an incomplete geodesic must end in an &#34;actual&#34; singularity, when in fact they are careful to point out specifically that they don&#39;t claim the geodesics end at a strong curvature singularity. &lt;shrug&gt; 2023-12-21T20:00:39Z