Speed of Light: A universal Constant?
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From: PD on 25 Mar 2005 12:00 kenseto wrote: > "bz" <bz+sp(a)ch100-5.chem.lsu.edu> wrote in message > news:Xns96217F0FC3412WQAHBGMXSZHVspammote(a)130.39.198.139... > > "kenseto" <kenseto(a)erinet.com> wrote in > > news:24Z%d.14316$cC6.10056(a)fe2.columbus.rr.com: > > > > > What you said is hogwash. If we define that the wave length of a > > > specific light source remains constant in all frames then the observed > > > Doppler shift is due to the varying speed of light from these different > > > sources. > > > > > > > Are you going to say that doppler shift of sound is ALSO due to varying > > the speed of sound? A car drops a fire cracker on the ground and sets off > > a fire cracker on the hood of the car at the same time. The 'bang' from > > the fire cracker on the ground and the one on the hood of the car reach me > > at the same time. The bang from the one on the hood of the car is dopplar > > shifted, the one on the ground is not. They both travel through the same > > air. Why should one travel at a different speed than the other? > > I assume that you mean that the fire cracker is at rest wrt the ground when > it goes off. In that case there is no Doppler shift. The fire cracker on the > car would be Doppler shifted. The sound generated by that fire cracker would > be closer to the detector with the passage of incremental time and this is > the cause of the doppler shift. There is no valid way to measure the speed > of sound from a moving fire cracker because there is no valid way to measure > the distance between the fire cracker and the detector at rest when the fire > cracker generate the first sound wave. Oh, good Lord. I can't believe you said such a thing. Never mind light. First pick up a book and learn what causes the Doppler effect in sound. Jiminy. Whoowhee. [snip]
From: bz on 25 Mar 2005 12:38 "kenseto" <kenseto(a)erinet.com> wrote in news:FdA0e.10297$rL3.7707(a)fe2.columbus.rr.com: > > "bz" <bz+sp(a)ch100-5.chem.lsu.edu> wrote in message > news:Xns96217F0FC3412WQAHBGMXSZHVspammote(a)130.39.198.139... >> "kenseto" <kenseto(a)erinet.com> wrote in >> news:24Z%d.14316$cC6.10056(a)fe2.columbus.rr.com: >> >> > What you said is hogwash. If we define that the wave length of a >> > specific light source remains constant in all frames then the >> > observed Doppler shift is due to the varying speed of light from >> > these different sources. >> > >> >> Are you going to say that doppler shift of sound is ALSO due to varying >> the speed of sound? A car drops a fire cracker on the ground and sets >> off a fire cracker on the hood of the car at the same time. The 'bang' >> from the fire cracker on the ground and the one on the hood of the car >> reach me at the same time. The bang from the one on the hood of the car >> is dopplar shifted, the one on the ground is not. They both travel >> through the same air. Why should one travel at a different speed than >> the other? > > I assume that you mean that the fire cracker is at rest wrt the ground > when it goes off. In that case there is no Doppler shift. right, so far. > The fire > cracker on the car would be Doppler shifted. Right. > The sound generated by that > fire cracker would be closer to the detector with the passage of > incremental time and this is the cause of the doppler shift. almost right. > There is no > valid way to measure the speed of sound from a moving fire cracker wrong. You can measure the speed of the car. > because there is no valid way to measure the distance between the fire > cracker and the detector at rest when the fire cracker generate the > first sound wave. wrong. you can measure the speed of the car. > >> >> Why do you think that the sound/light bouncing off of a moving object >> changes speed? >> >> I know that the waves do NOT change speed. > > Yes, waves in a medium do not change speed if you measure speed at the > rest frame of the medium. right. >> >> How do I know that they don't? I can measure their speed between two >> points AFTER they have bounced off of something and come back to me. >> Their transit between the two points will be at the speed of light. > > When you are measuring light speed between two points in your frame you > are not measuring speed from a source moving wrt you. You are measuring > the speed of light in your own frame....one of the point acts as a > source and the other acts as a receiver. Each point is a receiver. Each receives the signal from the moving source. If the light was moving at a speed different than light because it came from a moving source, it either continues to move at the different speed, or you must explain why it changes speed. > This is true no matter where > the source of light is coming from. you always measure things in your own frame. >> >> Their energy is changed by bouncing off of a moving object, their >> frequency has changed, but their speed is not changed. > > There is no valid way to measuring the speed of light between a moving > source and a stationary receiver. Why? Because there is no valid way to > measure the distance between the moving source and the detector when the > first photon is generated. This is wrong. Picture the moving blades of a fan. Why can't I know the exact distance to the fan blade at every instant of time? Why would that knowledge be invalid? -- bz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+sp(a)ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
From: George Dishman on 25 Mar 2005 14:21 "bz" <bz+sp(a)ch100-5.chem.lsu.edu> wrote in message news:Xns96232DF509270WQAHBGMXSZHVspammote(a)130.39.198.139... > > "Nick" <macromitch(a)yahoo.com> wrote in news:1111644867.340144.91590 > @o13g2000cwo.googlegroups.com: > > [note: I have fixed nicks failure to quote as his comment is meaningless > without context -bz-] > >> Sam Wormley <swormley1(a)mchsi.com> wrote in >> news:EOs0e.98282$r55.61174(a)attbi_s52: >> >>> Subject: Re: Speed of Light: A universal Constant? >>> From: Sam Wormley <swormley1(a)mchsi.com> >>> Newsgroups: sci.physics.relativity,sci.physics,sci.astro <snip> >>> Empirical Data: Speed of light is constant for all observers. >>> >>> >> Not accelerating ones. > > proof? Turn slowly around in a circle, say in ten seconds. The Andromeda Galaxy is about 2 to 3 million light years away. In a coordinate frame that rotated with you, the galaxy and all the light in it moved about 15 million light years in ten seconds. You can get a similar result using linear acceleration but the rotating frame is an extreme and obvious example. HTH George
From: bz on 25 Mar 2005 14:58 "George Dishman" <george(a)briar.demon.co.uk> wrote in news:d21o60$lo6$1 @news.freedom2surf.net: > > Turn slowly around in a circle, say in ten seconds. > The Andromeda Galaxy is about 2 to 3 million light > years away. In a coordinate frame that rotated with > you, the galaxy and all the light in it moved about > 15 million light years in ten seconds. Amazing, and the angular momentum of all that supraluminal mass was concerved too. I suspect that if I was on a rotating platform with equipment to measure the speed of light from the Andromeda Galaxy... I would find that it still moves at c. The earth is such a platform. However, I get your point. It appears that you have just demonstrated that unlike linear motion, where there is no absolute frame of reference, where rotation is concern, there is an absolute frame of reference and radial velocities must be measured with respect to THAT frame of reference. -- bz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+sp(a)ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
From: Henri Wilson on 25 Mar 2005 16:26
On Thu, 24 Mar 2005 23:33:47 -0000, "George Dishman" <george(a)briar.demon.co.uk> wrote: > >"Henri Wilson" <H@..> wrote in message >news:9th441lniu1vqkk2mr2gsrsoutv78lf0oi(a)4ax.com... >> On Wed, 23 Mar 2005 22:59:17 -0000, "George Dishman" >> <george(a)briar.demon.co.uk> >> wrote: >... >>>> You will find that whenever they cannot answer a difficult >>>> question, they will either resort to abuse and ridicule >>>> (...you don't understand relativity!) >>> >>>When it is pointed out that a comment that >>>contradicts what you will find in any textbook, >>>it isn't ridicule, it is merely a statement of >>>fact. Nobody will waste time on such strawmen >>>but it's useful to point out why. >> >> Do you really believe everything in every text book? > >No, I check what I read, and so far all the >textbooks I have seen on relativity explained >it correctly with perhaps a few minor quibbles. >When somebody writes "SR says ..." and goes >on to say something that bears no resemblance >to what SR says, then IMHO pointing that out is >a helpful response and for most reasonable people >will allow them to look for the source of their >misunderstanding. That is not ridicule. > >> If Stan is promoting the ballistic theory of light then >> he is much more likely to be correct than you are. > >See Jim Greenfield's reply, he has explained >Stan's error succinctly. I don't care. > >As we have discussed before, ballistic theory is >disproved by the Sagnac Experiment. Bull. The reason for the fringe shift has nothing to do with light speed. It is due to the fact that the mirrors rotate slightly during the time light travels between them. The two opposite beams are deflected in opposite directions. Note: A fibre ring is like an infinite number of mirrors with an infiniteimal angular change at each one. Same effect overall. > >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. |