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#generalrelativity

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Khurram Wadee ✅<p><a href="https://mastodon.org.uk/tags/Euclid" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Euclid</span></a> <a href="https://mastodon.org.uk/tags/telescope" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>telescope</span></a> captures <a href="https://mastodon.org.uk/tags/EinsteinRing" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>EinsteinRing</span></a> revealing <a href="https://mastodon.org.uk/tags/warping" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>warping</span></a> of <a href="https://mastodon.org.uk/tags/space" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>space</span></a> | <a href="https://mastodon.org.uk/tags/EuropeanSpaceAgency" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>EuropeanSpaceAgency</span></a> | The Guardian</p><p><a href="https://www.theguardian.com/science/2025/feb/10/euclid-telescope-captures-einstein-ring-revealing-warping-of-space" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://www.</span><span class="ellipsis">theguardian.com/science/2025/f</span><span class="invisible">eb/10/euclid-telescope-captures-einstein-ring-revealing-warping-of-space</span></a></p><p><a href="https://mastodon.org.uk/tags/Science" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Science</span></a> <a href="https://mastodon.org.uk/tags/Astronomy" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Astronomy</span></a> <a href="https://mastodon.org.uk/tags/Relativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Relativity</span></a> <a href="https://mastodon.org.uk/tags/GeneralRelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GeneralRelativity</span></a> <a href="https://mastodon.org.uk/tags/ESA" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>ESA</span></a></p>
Jonathan Z Simon<p><a href="https://fediscience.org/tags/DavidLynch" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>DavidLynch</span></a> consistent with his other worldly oddness par excellence , the last strip above contains one of the few examples I know of of a <a href="https://fediscience.org/tags/GeneralRelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GeneralRelativity</span></a> joke.</p>
Droppie [infosec] 🐨:archlinux: :kde: :firefox_nightly: :thunderbird: :vegan:​<p>This article surprised me. </p><p><a href="https://arstechnica.com/science/2025/01/not-just-heat-death-here-are-five-ways-the-universe-could-end/" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="ellipsis">arstechnica.com/science/2025/0</span><span class="invisible">1/not-just-heat-death-here-are-five-ways-the-universe-could-end/</span></a></p><p>It lists &amp; discusses...</p><ul><li>The heat death</li><li>The Big Rip</li><li>The Big Crunch</li><li>The phase transition</li><li>CCC [conformal cyclic cosmology]</li></ul><p>...yet somehow it entirely fails to even mention the most probable scenario of all</p><ul><li>the seven-armed 42-eyed pimply teenage thingie currently running all this shemozzle in its digital simulation VM, gets called by its parents to <em>come &amp; eat dinner then get on &amp; do its homework, so shut that bloody pooter down right now young thingie!</em> </li></ul><p><a href="https://infosec.space/tags/cosmology" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>cosmology</span></a> <a href="https://infosec.space/tags/astrophysics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>astrophysics</span></a> <a href="https://infosec.space/tags/thermodynamics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>thermodynamics</span></a> <a href="https://infosec.space/tags/universe" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>universe</span></a> <a href="https://infosec.space/tags/existentialdread" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>existentialdread</span></a> <a href="https://infosec.space/tags/darkenergy" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>darkenergy</span></a> <a href="https://infosec.space/tags/Hubble" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Hubble</span></a> <a href="https://infosec.space/tags/Einstein" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Einstein</span></a> <a href="https://infosec.space/tags/Penrose" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Penrose</span></a> <a href="https://infosec.space/tags/generalrelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>generalrelativity</span></a> <a href="https://infosec.space/tags/physics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>physics</span></a></p>
pglpm<p>Can any astrophysicist here tell me whether the blue ring in Webb's image of quasar RX&nbsp;J1131-1231 is also coming from the quasar, or whether it's coming from the lensing galaxy in the centre? I'm reading contradictory information about this on the ESA site</p><p><a href="https://esawebb.org/images/potm2406a/" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="">esawebb.org/images/potm2406a/</span><span class="invisible"></span></a></p><p><a href="https://c.im/tags/astrophysics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>astrophysics</span></a> <a href="https://c.im/tags/quasar" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>quasar</span></a> <a href="https://c.im/tags/gravitationallen" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>gravitationallen</span></a> <a href="https://c.im/tags/webb" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>webb</span></a> <a href="https://c.im/tags/generalrelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>generalrelativity</span></a></p>
In the Dark<p><strong>Newton’s Opticks and a Query about the Bending of&nbsp;Light</strong></p><p>The story of the famous 1919 expeditions to measure the bending of light by the Sun as a test of general relativity has featured many times on this blog (e.g. <a href="https://telescoper.blog/2019/05/29/the-centenary-of-the-1919-eclipse-expeditions/" rel="nofollow noopener" target="_blank">here</a>). I ahve also written elsewhere about it, e.g. <a href="https://arxiv.org/abs/astro-ph/0102462" rel="nofollow noopener" target="_blank">here</a>. One way this is often presented is whether the measurements preferred the “Einstein” prediction or one consistent with “Newton”, there being a famous factor of two between the two.</p><p>In fact the earliest published calculation of the deflection of light by the Sun was not by <a href="https://en.wikipedia.org/wiki/Isaac_Newton" rel="nofollow noopener" target="_blank">Isaac Newton</a> but by Johann Georg von Soldner (<em>Uber die Ablenkung eines Lichstrals von seiner geradlinigen Bewegung, durch die Attraktion eines Weltk¨orpers, and welchem er nahe vorbei geht</em>. Berliner Astronomisches Jahrbuch, 1801: 161-172). This calculation does use Newtonian theory, but as far as I know there is no record tof any calculation of this sort by Newton himself.</p> <a href="https://telescoper.blog/wp-content/uploads/2024/12/opticks-1.jpg" rel="nofollow noopener" target="_blank"></a> <p>There is, however, something very tantalizing in Newton’s 1704 book <em><a href="https://en.wikipedia.org/wiki/Opticks" rel="nofollow noopener" target="_blank">Opticks</a></em>, published almost 20 years after his <em>Principia</em> outlined the laws of mechanics and of universal gravitation. <em>Opticks</em> which (unlike the <em>Principia</em>) was written in English, ends with a series of rhetorical questions called “Queries” which present speculative ideas about light and its interactions with matter. The first of these reads:</p><blockquote><p>Query 1. Do not Bodies act upon Light at a distance, and by their action bend its Rays; and is not this action (<em>caeteris paribus</em>) strongest at the least distance?</p></blockquote><p>This looks very much like a speculation about the bending of light by gravitation. But if that’s what it is, he could have done exactly what Soldner did about a century later. Why then did he never publish the result and why was it never found among his unpublished papers? </p><p>I’ve spoken to several people about this and there are three main ideas. One is that Newton actual did the Soldner calculation, and that the manuscript was accidentally destroyed in a fire caused by his dog, <a href="https://en.wikipedia.org/wiki/Diamond_(dog)" rel="nofollow noopener" target="_blank">Diamond</a>. The other is that he just never got round to it, which seems unlikely because it’s not a difficult calculation and Newton lived over 20 years after the publication of the <em>Opticks</em>. The third possibility is that Query 1 wasn’t about gravity at all. If it had been, wouldn’t he have used the word and wouldn’t he have mentioned the inverse-square law specifically? Perhaps what he had in mind was some kind of refraction. This interpretation is consistent with other Queries where he talks about the “aetherial Medium” through which he supposed light to propagate being distorted by the presence of massive bodies and thus causing refraction. For example, from Query 21,</p><blockquote><p>Is not this Medium much rarer within the dense Bodies of the Sun, Stars, Planets and Comets, than in the empty celestial Spaces between them?</p></blockquote><p>I suppose we’ll never know what Newton had in mind. I am split between the first and third explanations above.</p><p>It’s worth mentioning that some of the other Queries are very prescient. Take Query 5, for example:</p><blockquote><p>Do not Bodies and Light act mutually upon one another; that is to say, Bodies upon Light in emitting, reflecting, refracting and inflecting it, and Light upon Bodies for heating them, and putting their parts into a vibrating motion wherein heat consists?</p></blockquote><p>Clever chap, Newton!</p><p><a rel="nofollow noopener" class="hashtag u-tag u-category" href="https://telescoper.blog/tag/1919-eclipse-expeditions/" target="_blank">#1919EclipseExpeditions</a> <a rel="nofollow noopener" class="hashtag u-tag u-category" href="https://telescoper.blog/tag/albert-einstein/" target="_blank">#AlbertEinstein</a> <a rel="nofollow noopener" class="hashtag u-tag u-category" href="https://telescoper.blog/tag/general-relativity/" target="_blank">#generalRelativity</a> <a rel="nofollow noopener" class="hashtag u-tag u-category" href="https://telescoper.blog/tag/isaac-newton/" target="_blank">#IsaacNewton</a> <a rel="nofollow noopener" class="hashtag u-tag u-category" href="https://telescoper.blog/tag/johann-georg-von-soldner/" target="_blank">#JohannGeorgVonSoldner</a></p>
MPI for Gravitational Physics<p>📣 Tiburtius Prize 2024 for Gustav Uhre Jakobsen 🏆</p><p>Recognition award for visiting postdoc at AEI Potsdam</p><p>Gustav Uhre Jakobsen, a postdoc at the Humboldt University of Berlin and in the Astrophysical and Cosmological Relativity Department at the <span class="h-card" translate="no"><a href="https://astrodon.social/@mpi_grav" class="u-url mention" rel="nofollow noopener" target="_blank">@<span>mpi_grav</span></a></span> in the Potsdam Science Park, will be awarded a “Tirburtius Prize – Prize of the Berlin Universities” for his dissertation.</p><p>The reviewer praises not only the impressive wealth of topics in Jakobsen's doctoral thesis titled “Gravitational Scattering of Compact Bodies from Worldline Quantum Field Theory” and the quality of the research results, but also the impact it has had in the research community.</p><p>➡️ <a href="https://www.aei.mpg.de/1202051/tiburtius-prize-2024-for-gustav-uhre-jakobsen" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://www.</span><span class="ellipsis">aei.mpg.de/1202051/tiburtius-p</span><span class="invisible">rize-2024-for-gustav-uhre-jakobsen</span></a></p><p><a href="https://astrodon.social/tags/ResearchAward" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>ResearchAward</span></a> <a href="https://astrodon.social/tags/Berlin" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Berlin</span></a> <a href="https://astrodon.social/tags/PhDThesis" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>PhDThesis</span></a> <a href="https://astrodon.social/tags/PhDLife" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>PhDLife</span></a> <a href="https://astrodon.social/tags/QuantumFieldTheory" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>QuantumFieldTheory</span></a> <a href="https://astrodon.social/tags/GeneralRelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GeneralRelativity</span></a></p>
Boud<p><span class="h-card" translate="no"><a href="https://astrodon.social/@ec_euclid" class="u-url mention" rel="nofollow noopener" target="_blank">@<span>ec_euclid</span></a></span> </p><p>Reminder: in a spacetime A satisfying <a href="https://framapiaf.org/tags/GeneralRelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GeneralRelativity</span></a>, light in a vacuum travels in straight lines, no matter how much mass is nearby. There's *no* bending of light paths.</p><p>Instead, spacetime is curved by mass. If you project from A to a Euclidean 3-space B, with a mapping f:A-&gt;B, then the *projected* paths of light are bent in B. Like the flight paths of planes flying in straight lines are bent when projected onto flat maps of the Earth.</p><p><a href="https://framapiaf.org/tags/LiesToChildren" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>LiesToChildren</span></a></p><p><a href="https://en.wikipedia.org/wiki/Lie-to-children" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="ellipsis">en.wikipedia.org/wiki/Lie-to-c</span><span class="invisible">hildren</span></a></p>
IRAP<p>[Einstein's theory and <a href="https://astrodon.social/tags/observation" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>observation</span></a> data] Researchers have compared <a href="https://astrodon.social/tags/DarkEnergySurvey" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>DarkEnergySurvey</span></a> data with predictions from Einstein's theory of <a href="https://astrodon.social/tags/GeneralRelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GeneralRelativity</span></a> ... and discovered some <a href="https://astrodon.social/tags/incompatibility" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>incompatibility</span></a> ...</p><p>“We have discovered that very far in the past, 6 and 7 billion years ago, the depth of the <a href="https://astrodon.social/tags/GravitationalSinks" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GravitationalSinks</span></a> is completely compatible with Einstein's predictions. On the other hand, in the period closer to today, 3.5 and 5 billion years ago, they are a little shallower than predicted by Einstein”, reveals Isaac Tutusaus, assistant astronomer at IRAP / Université Paul Sabatier Toulouse III.</p><p>Is the slowdown in the growth of gravitational sinks linked to the acceleration of the <a href="https://astrodon.social/tags/expansion" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>expansion</span></a> of our <a href="https://astrodon.social/tags/Universe" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Universe</span></a>? The answer will undoubtedly be found in a few years' time, thanks to more numerous and more precise data from the <span class="h-card" translate="no"><a href="https://astrodon.social/@ec_euclid" class="u-url mention" rel="nofollow noopener" target="_blank">@<span>ec_euclid</span></a></span> mission.</p><p>Details+: <a href="https://www.irap.omp.eu/en/2024/11/einsteins-equations-collide-with-the-mysteries-of-the-universe/" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://www.</span><span class="ellipsis">irap.omp.eu/en/2024/11/einstei</span><span class="invisible">ns-equations-collide-with-the-mysteries-of-the-universe/</span></a></p>
pglpm<p>Dear geodesists, astronomers, and astrophysicists: Does any of you know of some publication that explicitly reports the expression for the metric in a Geocentric Terrestrial Reference System (GTRS) or in the more specific International Terrestrial Reference System (ITRS)?</p><p>Various publications (eg <a href="https://doi.org/10.1086/378162" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="">doi.org/10.1086/378162</span><span class="invisible"></span></a>) and textbooks (eg <a href="https://doi.org/10.1017/CBO9781139507486" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="ellipsis">doi.org/10.1017/CBO97811395074</span><span class="invisible">86</span></a>) report and discuss the metrics for the Geocentric Celestial Reference System (GCRS), but not for the GTRS. (Even though it seems to me that the expression should be formally identical, as the off-diagonal timelike components take care of rotation).</p><p>Cheers! (Sorry for spamming borderline hashtags.)</p><p><a href="https://c.im/tags/iau" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>iau</span></a> <a href="https://c.im/tags/geodesy" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>geodesy</span></a> <a href="https://c.im/tags/astronomy" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>astronomy</span></a> <a href="https://c.im/tags/physics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>physics</span></a> <a href="https://c.im/tags/generalrelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>generalrelativity</span></a> <a href="https://c.im/tags/astrophysics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>astrophysics</span></a> <a href="https://c.im/tags/internationalastronomicalunion" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>internationalastronomicalunion</span></a></p>
pglpm<p>Does anyone happen to have an e-copy of S.&nbsp;Winitzki's "Topics in General Relativity"? Apparently it was freely available online until several years ago, but now I can't find a copy anywhere. Cheers!</p><p><a href="https://sites.google.com/site/winitzki/index/topics-in-general-relativity" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="ellipsis">sites.google.com/site/winitzki</span><span class="invisible">/index/topics-in-general-relativity</span></a></p><p><a href="https://c.im/tags/physics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>physics</span></a> <a href="https://c.im/tags/generalrelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>generalrelativity</span></a> <a href="https://c.im/tags/icanhazpdf" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>icanhazpdf</span></a></p>
Joachim<p><span class="h-card" translate="no"><a href="https://troet.cafe/@Hasecaesar" class="u-url mention">@<span>Hasecaesar</span></a></span> <span class="h-card" translate="no"><a href="https://pfalz.social/@DePaelzerBu" class="u-url mention">@<span>DePaelzerBu</span></a></span> <span class="h-card" translate="no"><a href="https://hessen.social/@eichkat3r" class="u-url mention">@<span>eichkat3r</span></a></span><br /> <br />Nehmen wir FAIR ( <span class="h-card" translate="no"><a href="https://helmholtz.social/@FAIR_GSI_de" class="u-url mention">@<span>FAIR_GSI_de</span></a></span> ): 0,99c</p><p>Da würden während 17min an Bord im Labor 2h vergehen.</p><p>m_0=110*80kg; m=gamma*m_0=7,1m_0;<br />E_kin=(m-m_0)*c^2=4,8*10^21J oder<br />E_kin=7,4*10^17*E_AAA. Man braucht etwa 7,4*10^17 Stück oder 9,6*10^12 Tonnen AAA-Batterien. :D</p><p>Allerdings müssten wir eigentlich angesichts der extremen Beschleunigung von großen Massen allgemeinrelativistisch rechnen... :D</p><p><a href="https://mastodon.social/tags/Physik" class="mention hashtag" rel="tag">#<span>Physik</span></a> <a href="https://mastodon.social/tags/PhysikEdu" class="mention hashtag" rel="tag">#<span>PhysikEdu</span></a> <a href="https://mastodon.social/tags/gravitationswellen" class="mention hashtag" rel="tag">#<span>gravitationswellen</span></a> <a href="https://mastodon.social/tags/generalrelativity" class="mention hashtag" rel="tag">#<span>generalrelativity</span></a></p>
Kemal ASLAN<p>1 dakikada Genel Görelilik Teorisi</p><p><a href="https://mastodon.online/tags/generalrelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>generalrelativity</span></a> <a href="https://mastodon.online/tags/physics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>physics</span></a> </p><p><a href="https://www.youtube.com/shorts/-MP7f_IwM68" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://www.</span><span class="">youtube.com/shorts/-MP7f_IwM68</span><span class="invisible"></span></a></p>
Steven Carneiro<p>The black hole information paradox:<br><a href="https://social.vivaldi.net/tags/blackhole" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>blackhole</span></a> <a href="https://social.vivaldi.net/tags/quantumphysics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>quantumphysics</span></a> <a href="https://social.vivaldi.net/tags/generalrelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>generalrelativity</span></a> <a href="https://social.vivaldi.net/tags/thermodynamics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>thermodynamics</span></a> <a href="https://social.vivaldi.net/tags/informationtheory" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>informationtheory</span></a> <a href="https://social.vivaldi.net/tags/research" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>research</span></a> <a href="https://social.vivaldi.net/tags/science" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>science</span></a><br>🕳️</p><p><a href="https://bigthink.com/starts-with-a-bang/black-hole-information-paradox-solved/" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="ellipsis">bigthink.com/starts-with-a-ban</span><span class="invisible">g/black-hole-information-paradox-solved/</span></a></p>
Steven Carneiro<p>Not the "theory of everything"?<br><a href="https://social.vivaldi.net/tags/physics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>physics</span></a> <a href="https://social.vivaldi.net/tags/quantummechanics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>quantummechanics</span></a> <a href="https://social.vivaldi.net/tags/generalrelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>generalrelativity</span></a> <a href="https://social.vivaldi.net/tags/theoryofeverything" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>theoryofeverything</span></a> <a href="https://social.vivaldi.net/tags/scientificresearch" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>scientificresearch</span></a><br>🤓</p><p><a href="https://www.popularmechanics.com/science/a62505507/incorrect-unified-theory/" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://www.</span><span class="ellipsis">popularmechanics.com/science/a</span><span class="invisible">62505507/incorrect-unified-theory/</span></a></p>
Steven Carneiro<p>Black hole entropy:<br><a href="https://social.vivaldi.net/tags/blackhole" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>blackhole</span></a> <a href="https://social.vivaldi.net/tags/spacetime" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>spacetime</span></a><br><a href="https://social.vivaldi.net/tags/quantumphysics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>quantumphysics</span></a> <a href="https://social.vivaldi.net/tags/quantummechanics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>quantummechanics</span></a> <a href="https://social.vivaldi.net/tags/quantuminformation" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>quantuminformation</span></a> <a href="https://social.vivaldi.net/tags/thermodynamics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>thermodynamics</span></a> <a href="https://social.vivaldi.net/tags/generalrelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>generalrelativity</span></a> <a href="https://social.vivaldi.net/tags/quantumgravity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>quantumgravity</span></a> <a href="https://social.vivaldi.net/tags/stringtheory" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>stringtheory</span></a><br>🕳️</p><p><a href="https://www.quantamagazine.org/the-1-clue-to-quantum-gravity-sits-on-the-surfaces-of-black-holes-20240925/" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://www.</span><span class="ellipsis">quantamagazine.org/the-1-clue-</span><span class="invisible">to-quantum-gravity-sits-on-the-surfaces-of-black-holes-20240925/</span></a></p>
Steven Carneiro<p>Testing quantum gravity in the lab:<br><a href="https://social.vivaldi.net/tags/quantumphysics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>quantumphysics</span></a> <a href="https://social.vivaldi.net/tags/quantummechanics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>quantummechanics</span></a> <a href="https://social.vivaldi.net/tags/gravity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>gravity</span></a> <a href="https://social.vivaldi.net/tags/generalrelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>generalrelativity</span></a> <a href="https://social.vivaldi.net/tags/model" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>model</span></a> <a href="https://social.vivaldi.net/tags/research" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>research</span></a> <a href="https://social.vivaldi.net/tags/science" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>science</span></a><br>🥼</p><p><a href="https://phys.org/news/2024-09-theoretical-physicists-method-central-theory.html" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="ellipsis">phys.org/news/2024-09-theoreti</span><span class="invisible">cal-physicists-method-central-theory.html</span></a></p>
Les capsules du prof Lutz<p><span class="h-card" translate="no"><a href="https://masto.ai/@GM7077" class="u-url mention" rel="nofollow noopener" target="_blank">@<span>GM7077</span></a></span> Y'a Véritassium qui avait visité une des installations <a href="https://youtu.be/iphcyNWFD10?t=63" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="">youtu.be/iphcyNWFD10?t=63</span><span class="invisible"></span></a> C'est hallucinant comme mesure. </p><p>Aveu: j'ai un bac+M.Sc en physique et je n'ai toujours pas compris comment on peut mesurer une contraction de l'espace en étant _dans_ l'espace...😜 À ma défense, je n'ai suivi aucun cours de <a href="https://mamot.fr/tags/GeneralRelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GeneralRelativity</span></a> </p><p>PS: le 'bouiip' qui débute le video "LIGO: Detection" précédent est le signal lui-même, imité par le physicien interviewé, à l'endroit où j'ai référé ce clip-ci)</p>
Matt Hodgkinson<p>A physics paper with an official publication date of Jan 2025, "On the same origin of quantum physics and general relativity from Riemannian geometry and Planck scale formalism", already has an expression of concern. If a paper is retracted before it is published, does the journal vanish in a catastrophic spacetime paradox?<br><a href="https://www.pubpeer.com/publications/EC8B4C9BB47F33E3A30B7E443028F3" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://www.</span><span class="ellipsis">pubpeer.com/publications/EC8B4</span><span class="invisible">C9BB47F33E3A30B7E443028F3</span></a><br><a href="https://scicomm.xyz/tags/PublicationEthics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>PublicationEthics</span></a> <a href="https://scicomm.xyz/tags/ResearchIntegrity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>ResearchIntegrity</span></a> <a href="https://scicomm.xyz/tags/Retractions" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Retractions</span></a> <a href="https://scicomm.xyz/tags/Elsevier" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Elsevier</span></a> <a href="https://scicomm.xyz/tags/AstroParticlePhysics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>AstroParticlePhysics</span></a> <a href="https://scicomm.xyz/tags/QuantumPhysics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>QuantumPhysics</span></a> <a href="https://scicomm.xyz/tags/GeneralRelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GeneralRelativity</span></a> <a href="https://scicomm.xyz/tags/QuantumGravity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>QuantumGravity</span></a> <a href="https://scicomm.xyz/tags/PhysicsMastodon" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>PhysicsMastodon</span></a></p>
KilleansRow 🇺🇲 🇺🇦🍀<p>Strange But Not Our Fault Dept : <a href="https://mastodon.online/tags/GeneralRelativity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GeneralRelativity</span></a> gaves us one of the keys to the kingdom wrt to time and so we can calculate time dilations in near Earth orbits and correct frame differences enough to make <a href="https://mastodon.online/tags/GPS" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GPS</span></a> work. We can use the same math around <a href="https://mastodon.online/tags/BlackHoles" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>BlackHoles</span></a> and so huge displacements in time are no longer sci fi, just a consequence of the math.We probably need to know the intersection of <a href="https://mastodon.online/tags/QuantumMechanics" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>QuantumMechanics</span></a> and <a href="https://mastodon.online/tags/Gravity" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Gravity</span></a> to understand how <a href="https://mastodon.online/tags/UAP" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>UAP</span></a> are doing what they're doing....</p>
In the Dark<p>In <a href="https://telescoper.blog/2024/07/27/four-new-publications-at-the-open-journal-of-astrophysics-6/" rel="nofollow noopener" target="_blank">Saturday’s roundup of the week’s publications at the Open Journal of Astrophysics</a> I mentioned a paper entitled “<a href="https://astro.theoj.org/article/121868-what-no-one-has-seen-before-gravitational-waveforms-from-warp-drive-collapse" rel="nofollow noopener" target="_blank">What no one has seen before: gravitational waveforms from warp drive collapse</a>” by Katy Clough (QMUL, UK), Tim Dietrich (Potsdam, Germany) and Sebastian Khan (Cardiff, UK).&nbsp; </p> <a href="https://telescoper.blog/wp-content/uploads/2024/07/clough_overlay.jpg" rel="nofollow noopener" target="_blank"></a> <p>Looking at the title of this paper you might be tempted to dismiss it on the grounds that warp drives are the stuff of science fiction (which they are), but this paper is really a rigorous technical study of the dynamical evolution and stability of spacetimes that violate the null energy condition, inspired by the idea of a warp drive. As soon as I announced this paper on social media it started to get attention. That will probably increase because there is now <a href="https://www.qmul.ac.uk/media/news/2024/se/new-study-simulates-gravitational-waves-from-failing-warp-drive.html" rel="nofollow noopener" target="_blank">a press release</a> to accompany the paper. I’ve taken the liberty of reproducing the text of the press release here:</p><p>–o–</p><p>Imagine a spaceship driven not by engines, but by compressing the spacetime in front of it. That’s the realm of science fiction, right? Well, not entirely. Physicists have been exploring the theoretical possibility of “warp drives” for decades, and a new study published in the Open Journal of Astrophysics&nbsp;takes things a step further – simulating the gravitational waves such a drive might emit if it broke down.&nbsp;</p><p>Warp drives are staples of science fiction, and in principle could propel spaceships faster than the speed of light. Unfortunately, there are many problems with constructing them in practice, such as the requirement for an exotic type of matter with negative energy. Other issues with the warp drive metric include the potential to use it to create closed time-like curves that violate causality and, from a more practical perspective, the difficulties for those in the ship in actually controlling and deactivating the bubble.&nbsp;</p><p>This new research is the result of a collaboration between specialists in gravitational physics at Queen Mary University of London, the University of Potsdam, the Max Planck Institute (MPI) for Gravitational Physics in Potsdam and Cardiff University. Whilst it doesn’t claim to have cracked the warp drive code, it explores the theoretical consequences of a warp drive “containment failure” using numerical simulations.</p><a href="https://telescoper.blog/wp-content/uploads/2024/07/clough.jpg" rel="nofollow noopener" target="_blank"></a><p><strong>Dr Katy Clough of Queen Mary University of London</strong>, the first author of the study explains: “Even though warp drives are purely theoretical, they have a well-defined description in Einstein’s theory of General Relativity, and so numerical simulations allow us to explore the impact they might have on spacetime in the form of gravitational waves.”&nbsp;</p><p>Co-author Dr Sebastian Khan, from Cardiff University’s School of Physics and Astronomy, adds: “Miguel Alcubierre created the first&nbsp; warp drive solution during his PhD at Cardiff University in 1994, and subsequently worked at the MPI in Potsdam. So it’s only natural that we&nbsp; carry on the tradition of warp drive research in the era of gravitational wave astronomy .”</p><p>The results are fascinating. The collapsing warp drive generates a distinct burst of gravitational waves, a ripple in spacetime that could be detectable by gravitational wave detectors that normally target black hole and neutron star mergers. Unlike the chirps from merging astrophysical objects, this signal would be a short, high-frequency burst, and so current detectors wouldn’t pick it up. However, future higher-frequency instruments might, and although no such instruments have yet been funded, the technology to build them exists. This raises the possibility of using these signals to search for evidence of warp drive technology, even if we can’t build it ourselves.&nbsp;</p><p>Dr Khan cautions “In our study, the initial shape of the spacetime is the warp bubble described by Alcubierre. While we were able to demonstrate that an observable signal could in principle be found by future detectors, given the speculative nature of the work this isn’t sufficient to drive instrument development.”</p><p>The study also delves into the energy dynamics of the collapsing warp drive. The process emits a wave of negative energy matter, followed by alternating positive and negative waves. This complex dance results in a net increase in the overall energy of the system, and in principle could provide another signature of the collapse if the outgoing waves interacted with normal matter.&nbsp;</p><p>This research pushes the boundaries of our understanding of exotic spacetimes and gravitational waves. Prof Dietrich comments: “For me, the most important aspect of the study is the novelty of accurately modelling the dynamics of negative energy spacetimes, and the possibility of extending the techniques to physical situations that can help us better understand the evolution and origin of our universe, or the avoidance of singularities at the centre of black holes.”</p><p>Dr Clough adds: “It’s a reminder that theoretical ideas can push us to explore the universe in new ways. Even though we are sceptical about the likelihood of seeing anything, I do think it is sufficiently interesting to be worth looking!”&nbsp;</p><p>The researchers plan to investigate how the signal changes with different warp drive models and explore the collapse of bubbles travelling at speeds exceeding the speed of light itself. Warp speed may be a long way off, but the quest to understand the universe’s secrets continues, one simulated crash at a time.</p><p><a href="https://telescoper.blog/2024/07/29/gravitational-waves-from-failing-warp-drives/" class="" rel="nofollow noopener" target="_blank">https://telescoper.blog/2024/07/29/gravitational-waves-from-failing-warp-drives/</a></p><p><a rel="nofollow noopener" class="hashtag u-tag u-category" href="https://telescoper.blog/tag/general-relativity/" target="_blank">#generalRelativity</a> <a rel="nofollow noopener" class="hashtag u-tag u-category" href="https://telescoper.blog/tag/warp-drives/" target="_blank">#WarpDrives</a></p>