Schwarzchild Radius of the Universe












1












$begingroup$


According to the Wiki on the Rs, the Rs of the observable universe is 13.7BLY.
https://en.wikipedia.org/wiki/Schwarzschild_radius
(The observable universe's mass has a Schwarzschild radius of approximately 13.7 billion light-years.[7][8])



The reference for this statement is:



https://arxiv.org/abs/1008.0933 and the Encyclopedia of Distances



Can someone please explain this to me... Is this simply because to get into the non-observable portion of the universe, you have to go faster than the speed of light?






astronomy







share|cite|improve this question











$endgroup$

















    1












    $begingroup$


    According to the Wiki on the Rs, the Rs of the observable universe is 13.7BLY.
    https://en.wikipedia.org/wiki/Schwarzschild_radius
    (The observable universe's mass has a Schwarzschild radius of approximately 13.7 billion light-years.[7][8])



    The reference for this statement is:



    https://arxiv.org/abs/1008.0933 and the Encyclopedia of Distances



    Can someone please explain this to me... Is this simply because to get into the non-observable portion of the universe, you have to go faster than the speed of light?






    astronomy







    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      According to the Wiki on the Rs, the Rs of the observable universe is 13.7BLY.
      https://en.wikipedia.org/wiki/Schwarzschild_radius
      (The observable universe's mass has a Schwarzschild radius of approximately 13.7 billion light-years.[7][8])



      The reference for this statement is:



      https://arxiv.org/abs/1008.0933 and the Encyclopedia of Distances



      Can someone please explain this to me... Is this simply because to get into the non-observable portion of the universe, you have to go faster than the speed of light?






      astronomy







      share|cite|improve this question











      $endgroup$




      According to the Wiki on the Rs, the Rs of the observable universe is 13.7BLY.
      https://en.wikipedia.org/wiki/Schwarzschild_radius
      (The observable universe's mass has a Schwarzschild radius of approximately 13.7 billion light-years.[7][8])



      The reference for this statement is:



      https://arxiv.org/abs/1008.0933 and the Encyclopedia of Distances



      Can someone please explain this to me... Is this simply because to get into the non-observable portion of the universe, you have to go faster than the speed of light?






      astronomy




      astronomy






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited 3 hours ago







      Rick

















      asked 8 hours ago









      RickRick

      620315




      620315






















          1 Answer
          1






          active

          oldest

          votes


















          5












          $begingroup$

          In this paper, the author begins by defining the radius of the observable universe as the radius of the Hubble sphere $r_{HS}=frac{c}{H_0}$, where $H_0$ is the Hubble constant. He then assumes that the universe is a homogeneous and isotropic collection of matter with density $rhoapprox rho_c$, where $rho_c=frac{3H^2}{8pi G}$ is the critical density of the universe at which the curvature of space is zero.



          Since he assumed that the universe is homogeneous and isotropic, the author uses the classical definition of density $rho=frac{3M}{4pi r_{HS}^3}$, where $M$ is the total mass of the observable universe, and with a bit of algebraic manipulation comes up with $r_{HS}=frac{2GM}{c^2}$. The author then asserts that $r_{HS}$ is the Schwarzschild radius of the universe, because what he came up with looks like the formula for a Schwarzschild radius.



          This is where the big problem is: the conditions that the author assumed in the beginning are not compatible with the conditions that admit the definition of a Schwarzschild radius. The Schwarzschild solution of the Einstein field equations requires that all of the mass of the universe is concentrated in a physical singularity at $r=0$, and the rest is vacuum. The author assumes essentially the exact opposite: that the mass of the universe is as spread out as possible, so that none of it is concentrated anywhere, there is no vacuum, and the universe has uniform density. As such, calling this a Schwarzschild radius doesn't really make sense, as it has nothing to do with the Schwarzschild solution besides sharing a superficial similarity in how we express their definitions. Just because he calls it a Schwarzschild radius doesn't mean that it is one.



          The moral of the story: though finding similar expressions in different contexts can often be a useful tool to guide intuition, it doesn't actually prove any connection, and isn't a substitute for an actual proof.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            probably_someone is still being kind ... the paper's author does not seem to understand even the basics of Einstein's formulation of general relativity ... the OP should just ignore this paper
            $endgroup$
            – Paul Young
            7 hours ago












          • $begingroup$
            It did not make any sense to me either which is why I posted the question. Thanks for the confirmation...
            $endgroup$
            – Rick
            3 hours ago












          Your Answer





          StackExchange.ifUsing("editor", function () {
          return StackExchange.using("mathjaxEditing", function () {
          StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
          StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
          });
          });
          }, "mathjax-editing");

          StackExchange.ready(function() {
          var channelOptions = {
          tags: "".split(" "),
          id: "151"
          };
          initTagRenderer("".split(" "), "".split(" "), channelOptions);

          StackExchange.using("externalEditor", function() {
          // Have to fire editor after snippets, if snippets enabled
          if (StackExchange.settings.snippets.snippetsEnabled) {
          StackExchange.using("snippets", function() {
          createEditor();
          });
          }
          else {
          createEditor();
          }
          });

          function createEditor() {
          StackExchange.prepareEditor({
          heartbeatType: 'answer',
          autoActivateHeartbeat: false,
          convertImagesToLinks: false,
          noModals: true,
          showLowRepImageUploadWarning: true,
          reputationToPostImages: null,
          bindNavPrevention: true,
          postfix: "",
          imageUploader: {
          brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
          contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
          allowUrls: true
          },
          noCode: true, onDemand: true,
          discardSelector: ".discard-answer"
          ,immediatelyShowMarkdownHelp:true
          });


          }
          });














          draft saved

          draft discarded


















          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f471160%2fschwarzchild-radius-of-the-universe%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown

























          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          5












          $begingroup$

          In this paper, the author begins by defining the radius of the observable universe as the radius of the Hubble sphere $r_{HS}=frac{c}{H_0}$, where $H_0$ is the Hubble constant. He then assumes that the universe is a homogeneous and isotropic collection of matter with density $rhoapprox rho_c$, where $rho_c=frac{3H^2}{8pi G}$ is the critical density of the universe at which the curvature of space is zero.



          Since he assumed that the universe is homogeneous and isotropic, the author uses the classical definition of density $rho=frac{3M}{4pi r_{HS}^3}$, where $M$ is the total mass of the observable universe, and with a bit of algebraic manipulation comes up with $r_{HS}=frac{2GM}{c^2}$. The author then asserts that $r_{HS}$ is the Schwarzschild radius of the universe, because what he came up with looks like the formula for a Schwarzschild radius.



          This is where the big problem is: the conditions that the author assumed in the beginning are not compatible with the conditions that admit the definition of a Schwarzschild radius. The Schwarzschild solution of the Einstein field equations requires that all of the mass of the universe is concentrated in a physical singularity at $r=0$, and the rest is vacuum. The author assumes essentially the exact opposite: that the mass of the universe is as spread out as possible, so that none of it is concentrated anywhere, there is no vacuum, and the universe has uniform density. As such, calling this a Schwarzschild radius doesn't really make sense, as it has nothing to do with the Schwarzschild solution besides sharing a superficial similarity in how we express their definitions. Just because he calls it a Schwarzschild radius doesn't mean that it is one.



          The moral of the story: though finding similar expressions in different contexts can often be a useful tool to guide intuition, it doesn't actually prove any connection, and isn't a substitute for an actual proof.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            probably_someone is still being kind ... the paper's author does not seem to understand even the basics of Einstein's formulation of general relativity ... the OP should just ignore this paper
            $endgroup$
            – Paul Young
            7 hours ago












          • $begingroup$
            It did not make any sense to me either which is why I posted the question. Thanks for the confirmation...
            $endgroup$
            – Rick
            3 hours ago
















          5












          $begingroup$

          In this paper, the author begins by defining the radius of the observable universe as the radius of the Hubble sphere $r_{HS}=frac{c}{H_0}$, where $H_0$ is the Hubble constant. He then assumes that the universe is a homogeneous and isotropic collection of matter with density $rhoapprox rho_c$, where $rho_c=frac{3H^2}{8pi G}$ is the critical density of the universe at which the curvature of space is zero.



          Since he assumed that the universe is homogeneous and isotropic, the author uses the classical definition of density $rho=frac{3M}{4pi r_{HS}^3}$, where $M$ is the total mass of the observable universe, and with a bit of algebraic manipulation comes up with $r_{HS}=frac{2GM}{c^2}$. The author then asserts that $r_{HS}$ is the Schwarzschild radius of the universe, because what he came up with looks like the formula for a Schwarzschild radius.



          This is where the big problem is: the conditions that the author assumed in the beginning are not compatible with the conditions that admit the definition of a Schwarzschild radius. The Schwarzschild solution of the Einstein field equations requires that all of the mass of the universe is concentrated in a physical singularity at $r=0$, and the rest is vacuum. The author assumes essentially the exact opposite: that the mass of the universe is as spread out as possible, so that none of it is concentrated anywhere, there is no vacuum, and the universe has uniform density. As such, calling this a Schwarzschild radius doesn't really make sense, as it has nothing to do with the Schwarzschild solution besides sharing a superficial similarity in how we express their definitions. Just because he calls it a Schwarzschild radius doesn't mean that it is one.



          The moral of the story: though finding similar expressions in different contexts can often be a useful tool to guide intuition, it doesn't actually prove any connection, and isn't a substitute for an actual proof.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            probably_someone is still being kind ... the paper's author does not seem to understand even the basics of Einstein's formulation of general relativity ... the OP should just ignore this paper
            $endgroup$
            – Paul Young
            7 hours ago












          • $begingroup$
            It did not make any sense to me either which is why I posted the question. Thanks for the confirmation...
            $endgroup$
            – Rick
            3 hours ago














          5












          5








          5





          $begingroup$

          In this paper, the author begins by defining the radius of the observable universe as the radius of the Hubble sphere $r_{HS}=frac{c}{H_0}$, where $H_0$ is the Hubble constant. He then assumes that the universe is a homogeneous and isotropic collection of matter with density $rhoapprox rho_c$, where $rho_c=frac{3H^2}{8pi G}$ is the critical density of the universe at which the curvature of space is zero.



          Since he assumed that the universe is homogeneous and isotropic, the author uses the classical definition of density $rho=frac{3M}{4pi r_{HS}^3}$, where $M$ is the total mass of the observable universe, and with a bit of algebraic manipulation comes up with $r_{HS}=frac{2GM}{c^2}$. The author then asserts that $r_{HS}$ is the Schwarzschild radius of the universe, because what he came up with looks like the formula for a Schwarzschild radius.



          This is where the big problem is: the conditions that the author assumed in the beginning are not compatible with the conditions that admit the definition of a Schwarzschild radius. The Schwarzschild solution of the Einstein field equations requires that all of the mass of the universe is concentrated in a physical singularity at $r=0$, and the rest is vacuum. The author assumes essentially the exact opposite: that the mass of the universe is as spread out as possible, so that none of it is concentrated anywhere, there is no vacuum, and the universe has uniform density. As such, calling this a Schwarzschild radius doesn't really make sense, as it has nothing to do with the Schwarzschild solution besides sharing a superficial similarity in how we express their definitions. Just because he calls it a Schwarzschild radius doesn't mean that it is one.



          The moral of the story: though finding similar expressions in different contexts can often be a useful tool to guide intuition, it doesn't actually prove any connection, and isn't a substitute for an actual proof.






          share|cite|improve this answer









          $endgroup$



          In this paper, the author begins by defining the radius of the observable universe as the radius of the Hubble sphere $r_{HS}=frac{c}{H_0}$, where $H_0$ is the Hubble constant. He then assumes that the universe is a homogeneous and isotropic collection of matter with density $rhoapprox rho_c$, where $rho_c=frac{3H^2}{8pi G}$ is the critical density of the universe at which the curvature of space is zero.



          Since he assumed that the universe is homogeneous and isotropic, the author uses the classical definition of density $rho=frac{3M}{4pi r_{HS}^3}$, where $M$ is the total mass of the observable universe, and with a bit of algebraic manipulation comes up with $r_{HS}=frac{2GM}{c^2}$. The author then asserts that $r_{HS}$ is the Schwarzschild radius of the universe, because what he came up with looks like the formula for a Schwarzschild radius.



          This is where the big problem is: the conditions that the author assumed in the beginning are not compatible with the conditions that admit the definition of a Schwarzschild radius. The Schwarzschild solution of the Einstein field equations requires that all of the mass of the universe is concentrated in a physical singularity at $r=0$, and the rest is vacuum. The author assumes essentially the exact opposite: that the mass of the universe is as spread out as possible, so that none of it is concentrated anywhere, there is no vacuum, and the universe has uniform density. As such, calling this a Schwarzschild radius doesn't really make sense, as it has nothing to do with the Schwarzschild solution besides sharing a superficial similarity in how we express their definitions. Just because he calls it a Schwarzschild radius doesn't mean that it is one.



          The moral of the story: though finding similar expressions in different contexts can often be a useful tool to guide intuition, it doesn't actually prove any connection, and isn't a substitute for an actual proof.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered 7 hours ago









          probably_someoneprobably_someone

          18.8k12960




          18.8k12960












          • $begingroup$
            probably_someone is still being kind ... the paper's author does not seem to understand even the basics of Einstein's formulation of general relativity ... the OP should just ignore this paper
            $endgroup$
            – Paul Young
            7 hours ago












          • $begingroup$
            It did not make any sense to me either which is why I posted the question. Thanks for the confirmation...
            $endgroup$
            – Rick
            3 hours ago


















          • $begingroup$
            probably_someone is still being kind ... the paper's author does not seem to understand even the basics of Einstein's formulation of general relativity ... the OP should just ignore this paper
            $endgroup$
            – Paul Young
            7 hours ago












          • $begingroup$
            It did not make any sense to me either which is why I posted the question. Thanks for the confirmation...
            $endgroup$
            – Rick
            3 hours ago
















          $begingroup$
          probably_someone is still being kind ... the paper's author does not seem to understand even the basics of Einstein's formulation of general relativity ... the OP should just ignore this paper
          $endgroup$
          – Paul Young
          7 hours ago






          $begingroup$
          probably_someone is still being kind ... the paper's author does not seem to understand even the basics of Einstein's formulation of general relativity ... the OP should just ignore this paper
          $endgroup$
          – Paul Young
          7 hours ago














          $begingroup$
          It did not make any sense to me either which is why I posted the question. Thanks for the confirmation...
          $endgroup$
          – Rick
          3 hours ago




          $begingroup$
          It did not make any sense to me either which is why I posted the question. Thanks for the confirmation...
          $endgroup$
          – Rick
          3 hours ago


















          draft saved

          draft discarded




















































          Thanks for contributing an answer to Physics Stack Exchange!


          • Please be sure to answer the question. Provide details and share your research!

          But avoid …



          • Asking for help, clarification, or responding to other answers.

          • Making statements based on opinion; back them up with references or personal experience.


          Use MathJax to format equations. MathJax reference.


          To learn more, see our tips on writing great answers.




          draft saved


          draft discarded














          StackExchange.ready(
          function () {
          StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f471160%2fschwarzchild-radius-of-the-universe%23new-answer', 'question_page');
          }
          );

          Post as a guest















          Required, but never shown





















































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown

































          Required, but never shown














          Required, but never shown












          Required, but never shown







          Required, but never shown







          -

          Popular posts from this blog

          Ponta tanko

          Image
          Usona ponta tanko M60A1 Ponta tanko estas, simile kiel kirasita savveturilo, inter specialaj kirasitaj transportiloj. Kiel pontaj tankoj eblas konsideri ĉiujn memmovigaj rimedoj ebligantaj superi obstaklojn ĝis larĝeco 24 metroj rekte en spaco de bataloperacoj. Ties ĉefa tasko estas ebligi al la propraj taĉmentoj daŭrigi en rapida antaŭenirado sen senbezona reteniĝo. El tio pli-malpli rezultas taktikaj-teknikaj postuloj, kiujn ili devas plenumi. Precipe temas pri kapablo operacii komune kun unue-sinsekvaj taĉmentoj kaj transpontigi obstaklojn dum kelke da minutoj. This page is only for reference, If you need detailed information, please check here
          Read more

          Tantalo (mitologio)

          Image
          Ĉi tiu artikolo temas pri mitologio. Por aliaj signifoj vidu la paĝon Tantalo (apartigilo) . Tantalo , laŭ Gioacchino Assereto. Laŭ la helena mitologio, Tantalo (el la greka Τάνταλος , ŝancelanta aŭ tre malfeliĉa ) estis filo de Zeŭso kaj la oceanidino Pluto, laŭ la plej divastigata versio. Li estis reĝo de Frigio [1] aŭ de la monto Sipilo, en Lidio (Malgrandazio) [2] kaj post sia morto li suferis eternan torturadon ĉe la Tartaro, la plej profunda parto de Hadeso, rezervita por la plej perversaj homoj. Tamen, kelkaj rakontoj asertas ke li estis reĝo de Argo aŭ de Korinto [3] , aŭ ke li migris norden el la monto Sipilo por akiri la tronon de Paflagonio, el kie Ilo forpelis lin pro tio, ke Tantalo forkaptis kaj seksperfortis lian fraton Ganimedon [4] , kaj tiel ofendis la diojn. Verŝajne li ankaŭ regis urbon en okcidenta Anatolio, kiun oni nomis Tantalis [5] pro li, aŭ Sipilo , pro la monto sur kies flanko ankoraŭ staras ĝiaj ruinaĵoj [6] . Laŭ la geografiisto Strabo,...
          Read more

          Erzsébet Schaár

          Image
          Erzsébet Schaár Memportreto de Erzsébet Schaár en Pécs Personaj informoj Naskiĝo 27-an de julio 1908 ( 1908-07-27 ) en Budafok Morto 29-an de aŭgusto 1975 ( 1975-08-29 ) (67-jara) en Budapeŝto Ŝtataneco Hungario Profesio skulptisto Familianoj Edz(in)o Tibor Vilt v   •   d   •   r Erzsébet Schaár [erĵEbet ŝAr], laŭ hungarlingve kutima sinsekvo Schaár Erzsébet estis hungara skulptisto. Ŝia edzo estis Tibor Vilt. Déryné Széppataki Róza en Miskolc fare de Erzsébet Schaár Erzsébet Schaár [1] naskiĝis la 27-an de julio 1908 en Budafok, ŝi mortis la 29-an de aŭgusto 1975 en Budapeŝto. Enhavo 1 Biografio 2 Elektitaj solaj ekspozicioj 3 Elektitaj kolektivaj ekspozicioj 4 Elektitaj skulptaĵoj 5 Elektitaj disĉiploj 6 Fontoj 7 Referencoj Biografio | Erzsébet Schaár studis en Industriarta Lernejo, poste en Reĝa Belarta Altlernejo (1924-1926). Ŝia ĉefinstruisto estis Zsig...
          Read more