tag:blogger.com,1999:blog-5212354357884270733.post9104961065585625843..comments2024-02-13T08:37:46.845+00:00Comments on Shiny Pebbles and other stuff: What does it mean to say that the universe is expanding?Rob Lowhttp://www.blogger.com/profile/01202748963636548483noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-5212354357884270733.post-44008459044838314392019-06-01T15:05:11.655+01:002019-06-01T15:05:11.655+01:00No proper paragraphs (there must be space between ...No proper paragraphs (there must be space between them, not just new lines).<br /><br />Text is not justified (text-align: justify).<br /><br />I refuse to read this.<br /><br />// b.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-5212354357884270733.post-91405769142915652622019-05-31T16:16:33.418+01:002019-05-31T16:16:33.418+01:00I think you could see it that way: you're just...I think you could see it that way: you're just stating a relationship between the dynamics of the geometry and the mass-energy distribution, without saying anything about some kind of force being exerted by the matter. <br /><br />It's a compressible fluid - in relativity, there's no such thing as an incompressible fluid (since that would enable you to send a signal instantaneously).Rob Lowhttps://www.blogger.com/profile/01202748963636548483noreply@blogger.comtag:blogger.com,1999:blog-5212354357884270733.post-69374137746022418452019-05-31T00:39:15.168+01:002019-05-31T00:39:15.168+01:00Very clear thanks. If i think of equations of stat...Very clear thanks. If i think of equations of state ("constitutive") equations, like Hooke's say. By equating Hooke to Newton 2 I eliminate the need for the Force concept, relating acceleration to relative position. Similarly are we eliminating the need to unpick the metric (potential) when we plug in the equation of state for e-m tensor of rhs of Einstein's equations? Also - did you mean compressive perfect fluid- or incompressible?leemcjameshttps://www.blogger.com/profile/02361355053331325032noreply@blogger.com