Speed of Light: A universal Constant?
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From: George Dishman on 6 Apr 2005 14:51 "Henri Wilson" <H@..> wrote in message news:dmq6515nh5ja7it6sljt6bvibl68a7otu3(a)4ax.com... > On Tue, 5 Apr 2005 23:51:10 +0100, "George Dishman" > <george(a)briar.demon.co.uk> > wrote: > >>Henri, there's a lot we have agreed. I've >>trimmed most out to get the size down. >> >>I'm going to try to bottom out this angle >>business, I think we are almost saying the >>same thing and it just needs a little >>clarification. > > OK, it isn't all that easy to understand this. I hope you find the discussion is clarifying some aspects. It has been useful revision for me. <snip> >>Each is a source of spherical wavefronts, just >>the distance between them changes from diagram >>to diagram. Of course the angle changes as a >>function of the point on the screen within each >>diagram but there is no change of angle of the >>laser beams. Each has to be spread wide enough >>to illuminate most of the screen anyway so the >>term "angle between the beams" isn't very well >>defined. > > That's correct. There is a certain amount of dispersion present in the > beams. > > In my sagnac model, there is both sideways displacement AND angular > change. That's why I am trying to make clear what the separate consequences of those are in the easier static case. >>Let me try another way to express this, perhaps >>you can agree this approach instead. I'll be a >>bit vague about the details but hopefully you'll >>allow me a little leeway. Take a point source S >>and a screen and create fringes by reflecting >>the source off a mirror M onto the screen as >>well as the direct beam. I've shown the beams >>as lines though they would need to illuminate >>most of the screen as usual: >> >> >> X S >> /| >> / | >> M / | >> R__|/ | >> |\ | >> \ | >> \A| >> \| >> ---+-- >> D >> screen >> >>There is a detector at point D on the screen and >>the reflected beam hits the mirror at point R >>and the angle between the beams is A at that >>point. >> >>So far, so good. >> >>Now suppose we move and tilt the mirror such that >>the point where the light reflects moves along an >>ellipse with S and D as its foci. The path length >>from S via R to D will remain the same but the >>angle A will change. What I am saying is that the >>brightness at the detector will be unchanged even >>though the angle is changing. What will be >>affected is the fringe spacing either side of the >>detector but that is because the path length >>anywhere else cannot be held constant as well as >>that to point D. >> >>Now consider the converse, suppose we move the >>mirror along the line from D to X (top left) >>again tilting the mirror as required to keep >>the point of reflection exactly on the X-D line. >>This time there will be a change of brightness >>at D due to the change of path length even though >>the angle A is being held constant. > > I undestand the experiment but I cannot see how it > relates to the problem. The question is do you agree with it or do we need to spend more time investigating? It should demonstrate that a change of angle as illustrated in the case of the elliptical motion has no effect on the brightness as long as the path length of both beams remains the same while path length does have an effect even if the angle remains constant. You said "In my sagnac model, there is both sideways displacement AND angular change." but, if you agree, you should now understand that a change of angle cannot cause any effect at the detector. >>I'm sure we are close to a mutual understanding. > > Not all that close yet. Shame. OK, what argument can you offer that my gedankens are wrong if you disagree? <snip> >>.. I have been trying out some new software >>that makes it easy to write Java simulations >>and I'd like to try it out if you are willing. > > Java is terrible. What is the program? It is a code generator. You don't actually write more than a few lines of Java, just the maths equations for the model. All the messy GUI stuff is written for you: http://fem.um.es/Ejs/ >>There is a simulation of the angles here: >> >>http://www.briar.demon.co.uk/Henri/SagnacAngles.html >> >>Can you let me know if you can see it or >>whether you get some horrible warning please. >>It is a Java applet so in theory cannot do >>any harm as it is stuck in a 'sandbox' with >>no access to your system, but some ISPs like >>AOL are a bit overzealous at times so you >>might get some sort of warnings. I don't, but >>then I wrote it :-) > > No, only the text appears. Thanks. I have discovered where the problem probably lies - Microsoft (surprise). The Java Virtual Machine in Internet Explorer is out of date due to legal arguments with Sun (MS wanted to add "extensions" which broke it for evry other browser) and the MS version is no longer supported. This will show you your current version: http://www.javatester.org/version.html It also gives links for getting the Sun version such as this: http://www.java.com/en/download/ I just followed the defaults and it worked fine. >>If it works, switch on one beam at a time >>using the check boxes and move the location >>of the detector using the slider. Wiggle it >>about and see if you agree with the beam >>paths. Then switch both on and look at the >>angle between the beams at the detector. Let >>me know what you think. > > Have another attempt. The program seems OK having tested from another site. If you install the JVM from Sun, it should solve the problem. > I gave up on Java. There has to be an easier way. > > Visual basic is SO simple. It is, but you have to pay for it :-( The Java SDK is free :-) More importantly, most people are sensible enough not to load an unknown exe file and run it. To run my sim, you get the JVM direct from Sun and when you view the applet, it cannot touch your machine. Also, once you fix IE, you can see any applet just by visiting the web page without downloading any program. There are pros and cons as always but so far I think Java has the edge. If it weren't for the MS installation problem, it would win hands down. >>p.s. I should add a circle to the diagram >>showing the edge of the turntable but I haven't >>found out how to do that yet :-( > > Keep at it George. You'll get there eventually. Certainly, but I've written the sim for this discussion in less than four hours starting from scratch with a new tool. George
From: Henri Wilson on 6 Apr 2005 16:47 On Wed, 6 Apr 2005 19:51:08 +0100, "George Dishman" <george(a)briar.demon.co.uk> wrote: > >"Henri Wilson" <H@..> wrote in message >news:dmq6515nh5ja7it6sljt6bvibl68a7otu3(a)4ax.com... >> On Tue, 5 Apr 2005 23:51:10 +0100, "George Dishman" >> <george(a)briar.demon.co.uk> >> wrote: >> >>>Henri, there's a lot we have agreed. I've >>>trimmed most out to get the size down. >>> >>>I'm going to try to bottom out this angle >>>business, I think we are almost saying the >>>same thing and it just needs a little >>>clarification. >> >> OK, it isn't all that easy to understand this. > >I hope you find the discussion is clarifying >some aspects. It has been useful revision for >me. > ><snip> >>>Each is a source of spherical wavefronts, just >>>the distance between them changes from diagram >>>to diagram. Of course the angle changes as a >>>function of the point on the screen within each >>>diagram but there is no change of angle of the >>>laser beams. Each has to be spread wide enough >>>to illuminate most of the screen anyway so the >>>term "angle between the beams" isn't very well >>>defined. >> >> That's correct. There is a certain amount of dispersion present in the >> beams. >> >> In my sagnac model, there is both sideways displacement AND angular >> change. > >That's why I am trying to make clear what >the separate consequences of those are in >the easier static case. > >>>Let me try another way to express this, perhaps >>>you can agree this approach instead. I'll be a >>>bit vague about the details but hopefully you'll >>>allow me a little leeway. Take a point source S >>>and a screen and create fringes by reflecting >>>the source off a mirror M onto the screen as >>>well as the direct beam. I've shown the beams >>>as lines though they would need to illuminate >>>most of the screen as usual: >>> >>> >>> X S >>> /| >>> / | >>> M / | >>> R__|/ | >>> |\ | >>> \ | >>> \A| >>> \| >>> ---+-- >>> D >>> screen >>> >>>There is a detector at point D on the screen and >>>the reflected beam hits the mirror at point R >>>and the angle between the beams is A at that >>>point. >>> >>>So far, so good. >>> >>>Now suppose we move and tilt the mirror such that >>>the point where the light reflects moves along an >>>ellipse with S and D as its foci. The path length >>>from S via R to D will remain the same but the >>>angle A will change. What I am saying is that the >>>brightness at the detector will be unchanged even >>>though the angle is changing. What will be >>>affected is the fringe spacing either side of the >>>detector but that is because the path length >>>anywhere else cannot be held constant as well as >>>that to point D. >>> >>>Now consider the converse, suppose we move the >>>mirror along the line from D to X (top left) >>>again tilting the mirror as required to keep >>>the point of reflection exactly on the X-D line. >>>This time there will be a change of brightness >>>at D due to the change of path length even though >>>the angle A is being held constant. >> >> I undestand the experiment but I cannot see how it >> relates to the problem. > >The question is do you agree with it or do we >need to spend more time investigating? > >It should demonstrate that a change of angle >as illustrated in the case of the elliptical >motion has no effect on the brightness as long >as the path length of both beams remains the >same while path length does have an effect even >if the angle remains constant. In the elliptical case, the intensity of the beam will remain constant only in a plane perpendicular to the beam direction. In your example, a cosine correction needs to be applied to compare intensities AT ANY POINT on the target. I'm not sure if tat is relevant. It might only affect the contrast of the fringes. > >You said "In my sagnac model, there is both >sideways displacement AND angular change." but, >if you agree, you should now understand that a >change of angle cannot cause any effect at the >detector. > But there is also a path length difference. Put it another way, when the apparatus is rotating, the sections of the two beams that arrive simultaneously at any point did not leave the source at the same instant. >>>I'm sure we are close to a mutual understanding. >> >> Not all that close yet. > >Shame. OK, what argument can you offer that >my gedankens are wrong if you disagree? What I just stated above. There is both a path difference and an angular change. > ><snip> >>>.. I have been trying out some new software >>>that makes it easy to write Java simulations >>>and I'd like to try it out if you are willing. >> >> Java is terrible. What is the program? > >It is a code generator. You don't actually >write more than a few lines of Java, just >the maths equations for the model. All the >messy GUI stuff is written for you: > >http://fem.um.es/Ejs/ > >>>There is a simulation of the angles here: >>> >>>http://www.briar.demon.co.uk/Henri/SagnacAngles.html >>> >>>Can you let me know if you can see it or >>>whether you get some horrible warning please. >>>It is a Java applet so in theory cannot do >>>any harm as it is stuck in a 'sandbox' with >>>no access to your system, but some ISPs like >>>AOL are a bit overzealous at times so you >>>might get some sort of warnings. I don't, but >>>then I wrote it :-) >> >> No, only the text appears. > >Thanks. I have discovered where the problem >probably lies - Microsoft (surprise). The >Java Virtual Machine in Internet Explorer is >out of date due to legal arguments with Sun >(MS wanted to add "extensions" which broke it >for evry other browser) and the MS version is >no longer supported. This will show you your >current version: > >http://www.javatester.org/version.html > >It also gives links for getting the Sun >version such as this: > >http://www.java.com/en/download/ Their web page is as hard to understand as their program. > >I just followed the defaults and it >worked fine. > >>>If it works, switch on one beam at a time >>>using the check boxes and move the location >>>of the detector using the slider. Wiggle it >>>about and see if you agree with the beam >>>paths. Then switch both on and look at the >>>angle between the beams at the detector. Let >>>me know what you think. >> >> Have another attempt. > >The program seems OK having tested from >another site. If you install the JVM from >Sun, it should solve the problem. My Java was not enabled but your applet still wont appear. > >> I gave up on Java. There has to be an easier way. >> >> Visual basic is SO simple. > >It is, but you have to pay for it :-( True > >The Java SDK is free :-) But the free version is very difficult to use. > >More importantly, most people are sensible >enough not to load an unknown exe file and >run it. To run my sim, you get the JVM direct >from Sun and when you view the applet, it >cannot touch your machine. > >Also, once you fix IE, you can see any >applet just by visiting the web page >without downloading any program. > >There are pros and cons as always but >so far I think Java has the edge. If >it weren't for the MS installation >problem, it would win hands down. > >>>p.s. I should add a circle to the diagram >>>showing the edge of the turntable but I haven't >>>found out how to do that yet :-( >> >> Keep at it George. You'll get there eventually. > >Certainly, but I've written the sim for >this discussion in less than four hours >starting from scratch with a new tool. Java code itself is pretty easy. Getting the thing to run is the hard part My daughter who is a programer is currectly learning Java. She agrees it is very confusing and hard to use. > >George > HW. www.users.bigpond.com/hewn/index.htm Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong.
From: Henri Wilson on 6 Apr 2005 17:08 On 6 Apr 2005 07:41:52 -0700, "PD" <pdraper(a)yahoo.com> wrote: > >kenseto wrote: >> "PD" <pdraper(a)yahoo.com> wrote in message >> news:1112731023.977565.318940(a)z14g2000cwz.googlegroups.com... >> > >> > Jim Greenfield wrote: >> Absolute Motion" >> http://www.erinet.com/kenseto/book.html > >Uh-huh. And the observed fringe pattern that occurs with sound waves or >water waves in a ripple tank, also using a diffraction grating, is also >not due to constructive interference, but is due to the absolution >motion of the grating with respect to the sound or water waves? > >So light's wave behavior and observed wavelike phenomona, stem from >completely different origins than what is seen in other wave phenomena? >Is that really what you want to maintain? Why shouldn't he? The classical wave theory of light breaks down in other respects. It is obviously inadequate. Light cannot be treated like water waves or sound. > >PD HW. www.users.bigpond.com/hewn/index.htm Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong.
From: Henri Wilson on 6 Apr 2005 17:23 On Wed, 6 Apr 2005 06:13:06 +0000 (UTC), bz <bz+sp(a)ch100-5.chem.lsu.edu> wrote: >H@..(Henri Wilson) wrote in >news:evs651539amj4j22e859p0euniifcdttrq(a)4ax.com: > >> Do you claim that light emitted from a remote star is initially >> traveling at c relative to every object in the universe? > >yes. > >> Does that require an infinite number of discreet speeds? > >A large number of indiscrete speeds. :) (don't tell any one that they have >been indiscrete). > >There are a finite number of objects in the universe. > >Emission is discrete. The wavelengths SEEN by observers are NOT discrete, >they depend on the RELATIVE motion of source and observer. So if a photon that travels through space for eons suddenly comes across an observer, it somehow 'knows' how much it should doppler shift? Does it carry information about its original source's speed wrt the ultimate random observer? Photons must be pretty clever little things if they can do that. I think they just move at c wrt their source. > >Emission lines, even from the gas in the neon sign in the bar's window, >will show the doppler effect, as the atoms/molecules (the same thing in >neon's case) are in motion. > >Absorption by another molecule of neon can only occur when the receiver is >going the right velocity so that the wavelengths match. OK answer this. Consider two photons that were emitted in a neon transition from quite separate and relatively moving sources. By chance, they end up traveling together through space. They eventually strike the same observer. How do they carry the information required to cause the correct doppler shift to take place? HW. www.users.bigpond.com/hewn/index.htm Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong.
From: PD on 6 Apr 2005 17:47
Henri Wilson wrote: > On Wed, 6 Apr 2005 06:13:06 +0000 (UTC), bz <bz+sp(a)ch100-5.chem.lsu.edu> wrote: > > >H@..(Henri Wilson) wrote in > >news:evs651539amj4j22e859p0euniifcdttrq(a)4ax.com: > > > >> Do you claim that light emitted from a remote star is initially > >> traveling at c relative to every object in the universe? > > > >yes. > > > >> Does that require an infinite number of discreet speeds? > > > >A large number of indiscrete speeds. :) (don't tell any one that they have > >been indiscrete). > > > >There are a finite number of objects in the universe. > > > >Emission is discrete. The wavelengths SEEN by observers are NOT discrete, > >they depend on the RELATIVE motion of source and observer. > > So if a photon that travels through space for eons suddenly comes across an > observer, it somehow 'knows' how much it should doppler shift? You have it in your mind that the wavelength (or frequency) is an inherent property of the photon, independent of the observer. This is not the case. > > Does it carry information about its original source's speed wrt the ultimate > random observer? It carries its wavepacket with it. The wavelength (or frequency) is not information that is carried inherently with it, any more than length is carried along with a physical rod. However, when the observer measures the wavepacket, that measurement is made in the observer's rest frame. > > Photons must be pretty clever little things if they can do that. > > I think they just move at c wrt their source. > > > > > > >Emission lines, even from the gas in the neon sign in the bar's window, > >will show the doppler effect, as the atoms/molecules (the same thing in > >neon's case) are in motion. > > > >Absorption by another molecule of neon can only occur when the receiver is > >going the right velocity so that the wavelengths match. > > OK answer this. > > Consider two photons that were emitted in a neon transition from quite separate > and relatively moving sources. By chance, they end up traveling together > through space. > They eventually strike the same observer. > > How do they carry the information required to cause the correct doppler shift > to take place? Because they are different wavepackets. The wavepackets do not have to do anything to change at the moment of observation. > > > HW. > www.users.bigpond.com/hewn/index.htm > > Sometimes I feel like a complete failure. > The most useful thing I have ever done is prove Einstein wrong. |