Path: csiph.com!news.mixmin.net!weretis.net!feeder1.news.weretis.net!news.solani.org!.POSTED!not-for-mail From: Thomas 'PointedEars' Lahn Newsgroups: sci.physics Subject: Re: 'Dark Matter' Date: Thu, 13 Aug 2015 13:41:03 +0200 Organization: PointedEars Software (PES) Lines: 86 Message-ID: <3395304.78prYaifWP@PointedEars.de> References: <641d58f0-2a64-46cb-a16e-24a2bb4133a3@googlegroups.com> <19e0d7fa-fc7e-4e76-996b-c8b0f034bf68@googlegroups.com> <6afb63b8-f5b8-455e-bd45-0b8f719c0d20@googlegroups.com> <1457970.BsSg34WjJe@PointedEars.de> <7461341.L6YsdKe0aM@PointedEars.de> Reply-To: Thomas 'PointedEars' Lahn Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8Bit X-Trace: solani.org 1439466277 19086 eJwFwQkBwDAIA0BLCX/lMFr8S9idazAmLTzM1/fAWuoTH3XOrULd6Ua8eXqksc1kCRMmIH4UJBBP (13 Aug 2015 11:44:37 GMT) X-Complaints-To: abuse@news.solani.org NNTP-Posting-Date: Thu, 13 Aug 2015 11:44:37 +0000 (UTC) User-Agent: KNode/4.14.2 X-User-ID: eJwNwoERACEIA7CVrKWA4wCe+4/wf4no8Alzuen9umrxSGbIixzW2VwCbx7ItnKuceDZHdluEcUXGG091Ach8BQ+ Cancel-Lock: sha1:uhCPWOSHvWVzEnscgBWjVi58ZMA= X-NNTP-Posting-Host: eJwFwYEBwCAIA7CXBEur5wiD/09YEpvGEhhETMwcp+2Cv8elKUrZaORNl/BNsg+LHLO8q38cWxE/ Xref: csiph.com sci.physics:513222 Michael Moroney wrote: > Thomas 'PointedEars' Lahn writes: >> Michael Moroney wrote: >>> Since the sun is spherically symmetric with photons going in all >>> direction, it all pretty much adds up to zero, and the sun doesn't move. >> The Sun is not a solid body. Since the two of you are arguing based on >> Newtonian mechanics (which is interesting to say the least, given the >> nature of the photon), if the Sun recoiled in all directions >> simultaneously, it >> would have to shrink. However, no shrinking of the Sun due to recoiling >> from photon emissions has been reported to date. > > Newtonian mechanics works well enough for the emitting plasma particle's > behavior, or the sun as a whole. Utter nonsense. Stellar dynamics is the quintessential evidence that both special and general relativity are correct, and that classical mechanics suffices as an approximation only for *low* speeds, *low* energies and so on. In particular, E_kin = mv²∕2 and p = mv from classical mechanics *do not hold* for massless photons: their kinetic energy is _not_ zero, and their momentum is not zero; they are moving at *the speed of light* instead. > The (slight) force trying to shrink the sun is counterbalanced by its heat > trying to expand the plasma and it's in steady state. You wish. > You are probably right that it's best to consider just the emitting plasma > particle There you go again: “the emitting plasma particle”? Do you even know what a plasma is? >> Or, because the Sun is basically *a ball of hot plasma*, it does not >> recoil at all, in any direction, but rotates slower and cools down >> instead as it loses momentum by emission of electromagnetic radiation. > > If you add the sum total of the motion of all the zillions of > ions/electrons that compose the sun before and after there will be a > very slight net shift. Cite evidence. > Momentum is conserved. Of that there is no doubt. However, I debate that any momentum is transported by any recoiling of stellar matter. Photons are _not_ like little energetic cannonballs as (the two of) you like to believe. > The energy of the photon, of course, does cool the sun slightly. Nonsense. If you knew what a plasma is in the first place, you would know that its temperature is more or less equivalent to the velocity of its constituents, and that E² = (pc)² + (mc²)² (1) whereas E is energy, p is momentum, c is the speed of light in vacuum, and m is mass. As for the photon (which, I should add, is not a “plasma particle”, as you apparently believe), m = 0, and so E = pc (2) = ℎc∕λ = ℎf. (3) IOW, the “relativistic mass”, which is equal to its energy, and the momentum, of a photon all depend only on the wavelength/frequency of the electromagnetic radiation it emerges as a constituent of under collision conditions [Einstein confirmed this in 1905 in his work on the photoelectric effect, and later showed the relation between Planck’s equation (3) and mass–energy equivalence (1)(2)]. And it is the momentum that a photon (or rather, zillions of photons per second) carries away from the Sun that causes the Sun either to cool down or its rotation to become slower. It is the energy that it carries away that causes the Sun to shrink; _not_ because of any recoiling, but because of the mass–energy equivalence it thereby loses mass as well (fear not: calculations show that the mass of the Sun is so large, it will not shrink considerably during its lifetime merely due to emission of radiation or other particles). PointedEars -- “Science is empirical: knowing the answer means nothing; testing your knowledge means everything.” —Dr. Lawrence M. Krauss, theoretical physicist, in “A Universe from Nothing” (2009)