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Article #16193Re: Why does light bend under gravity?
From: The Speaking Clock
Date: Sun, 16 Mar 2008 17:31
Date: Sun, 16 Mar 2008 17:31
49 lines
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4660 bytes
On 16 Mar, 18:14, Tom Roberts <tjroberts...@sbcglobal.net> wrote: > The Speaking Clock wrote: > > On 15 Mar, 08:57, Pentcho Valev <pva...@yahoo.com> wrote: > >> [... his usual nonsense] > > > Would the speed of light be a non wiggly constant at the very edge of > > the universe - bending around it? > > The speed of light is a constant, c, for any LOCAL measurement anywhere > in the universe. I guess that includes "non wiggly". It also includes > essentially all measurements of light speed here on earth. At least that > is what GR predicts, and there are no observations that contradict it. > > [Ignore Valev when he brings up Pound-Rebka and similar > experiments -- they do not measure speed.] > > But if you want to see light "bending around the universe" then that > would certainly require a non-local path, and there's no solid > prediction of the result (given the uncertainties in the physical > situation you have in mind). > > It is rather difficult to perform a non-local measurement of the speed > of light, but it has been done by sending radar waves across the solar > system to reflect back from mars and venus. By measuring the round-trip > delay repeatedly over several years, and fitting to the planetary > orbits, one can deduce the round-trip speed of light for these paths. > That speed varies, depending on how close to the sun the path passes; > look up "Shapiro time delay". The results are in excellent agreement > with the predictions of GR. > > Some people claim this is due to the solar atmosphere. > They are wrong: by doing this for multiple wavelengths the > effect of the solar atmosphere can be identified, and is > found to be negligible. Of course it would be highly > unlikely that such a different effect could mimic the GR > dependence on path. Indeed, measurements using pulsars > agree with the GR predictions for paths that never go > inside earth's orbit, and we know what the solar > atmosphere is out here. > > Tom Roberts Thank you Tom for that excellent explanation. Good ole c is still a dependable non wiggly constant! :) Cheers, TSC
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X-Google-Thread: 10b271,1ea0cb1d54d3d906 X-Google-Thread: 10f545,2d47498f99950055 X-Google-Thread: f6c41,2d47498f99950055 X-Google-Thread: fa4c1,c0039b44052ddae9 X-Google-Thread: f74ae,c0039b44052ddae9 X-Google-Attributes: gid10b271,gid10f545,gidf6c41,gidfa4c1,gidf74ae,public,usenet X-Google-Language: ENGLISH,ASCII Path: arc1-ca.pugleaf.net!g2news1.google.com!postnews.google.com!d21g2000prf.googlegroups.com!not-for-mail From: The Speaking Clock <harlequiness@live.co.uk> Newsgroups: sci.physics,sci.physics.relativity,sci.physics.particle,fr.sci.physique,sci.astro Subject: Re: Why does light bend under gravity? Date: Sun, 16 Mar 2008 10:31:36 -0700 (PDT) Organization: http://groups.google.com Lines: 49 Message-ID: <393163ec-cf49-4e62-806f-b06718a4757d@d21g2000prf.googlegroups.com> References: <1de25376-cbdf-4a88-9c24-635b73e962f0@e60g2000hsh.googlegroups.com> <YpBwj.12517$J41.7185@newssvr14.news.prodigy.net> <pan.2008.02.25.17.17.58@canonicalscience.com> <47C31602.1030806@guesswhatuia.no> <k887s35r0tqpss2mmaj14d9v70qblsjt3v@4ax.com> <7ad9324e-a185-4be5-8d37-36608dda682a@s37g2000prg.googlegroups.com> <6oe7s3t3ffk34ik95onbdq5i7ho1man8vh@4ax.com> <5d081222-5b36-4e82-b8d7-8900c2acbbc4@d4g2000prg.googlegroups.com> <L_mBj.16850$Ch6.2540@newssvr11.news.prodigy.net> <4a84042b-1718-45a4-82f9-0e2b9fa12240@x41g2000hsb.googlegroups.com> <toRBj.16222$xq2.10827@newssvr21.news.prodigy.net> <a2ca4f30-9c55-4fa6-a0a1-cc7ad49e36a4@s37g2000prg.googlegroups.com> <e2b37da4-49a5-40da-95d8-c48add78539d@8g2000hse.googlegroups.com> <350f08c0-cbc4-43ca-9ece-629159f22125@h11g2000prf.googlegroups.com> <OzcDj.20839$Ej5.5102@newssvr29.news.prodigy.net> NNTP-Posting-Host: 80.59.229.37 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1205688697 28722 127.0.0.1 (16 Mar 2008 17:31:37 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Sun, 16 Mar 2008 17:31:37 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: d21g2000prf.googlegroups.com; posting-host=80.59.229.37; posting-account=ye7KpgoAAACBFExrUXaZfsAg3OidUCh9 User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506),gzip(gfe),gzip(gfe)