Relativistic Doppler shift
in [Relativity]
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From: I.N. Galidakis on 24 Jul 2010 11:11 Does anyone know if there's any relativistic Doppler shift on a rotating source of EM radiation, at a distance where the linear velocity becomes close to c? In other words, if I rotate a 532 nm laser beam with a given angular frequency omega, what would be the Doppler shift for an observer at radius ~r, where omega*r=c? Thanks, -- I.
From: Androcles on 24 Jul 2010 11:38 "I.N. Galidakis" <morpheus(a)olympus.mons> wrote in message news:1279984306.163903(a)athprx03... | Does anyone know if there's any relativistic Doppler shift on a rotating source | of EM radiation, at a distance where the linear velocity becomes close to c? | | In other words, if I rotate a 532 nm laser beam with a given angular frequency | omega, what would be the Doppler shift for an observer at radius ~r, where | omega*r=c? | | Thanks, | -- | I. I know. I also know you are attempting to exceed c and start a debate; you can't succeed, idiot Einstein's 1/sqrt((c+v) * (c-v) /c^2) had to have a c+v to begin with, so go back to sleep on your mountain, morpheus van Winkle.
From: dlzc on 24 Jul 2010 12:33 Dear I.N. Galidakis: On Jul 24, 8:11 am, "I.N. Galidakis" <morph...(a)olympus.mons> wrote: > Does anyone know if there's any relativistic > Doppler shift on a rotating source of EM > radiation, at a distance where the linear > velocity becomes close to c? We cannot get an object to rotate anywhere near even 0.1c. The binding forces are not enough to hold it together. We can "crash" a laser beam headon into a high speed electron stream, and the laser photons end up with energies of up to gamma^2 (with gamma being for the electron's in the stream). > In other words, if I rotate a 532 nm laser > beam with a given angular frequency omega, > what would be the Doppler shift for an > observer at radius ~r, where omega*r=c? You'd have a redshifting of the light source, due to time dilation, then you'd have whatever classical Doppler effect you'd see based on the relative motion. Similar to an SR-only problem, only with the time dilation being more complex due to acceleration. David A. Smith
From: I.N. Galidakis on 24 Jul 2010 12:58 dlzc wrote: > Dear I.N. Galidakis: [snip] >> In other words, if I rotate a 532 nm laser >> beam with a given angular frequency omega, >> what would be the Doppler shift for an >> observer at radius ~r, where omega*r=c? > > You'd have a redshifting of the light source, due to time dilation, > then you'd have whatever classical Doppler effect you'd see based on > the relative motion. Similar to an SR-only problem, only with the > time dilation being more complex due to acceleration. Thanks. The time dilation I was able to calculate, but I cannot seem to see why I'd get a red/blue-shift (relativistic or not). The way I understand it, the _linear_ velocity at the tip of the beam (at distance r) is perpendicular to the tip's orbit (circle of radius r), so I cannot see how it contributes to a Doppler shift for an observer that gets hit by the beam head on. Any help? I need the actual calcs for the red/blue-shift for an observer that gets hit by the beam once for every period of the rotation. Thanks again, > David A. Smith -- I.
From: dlzc on 24 Jul 2010 23:56
Dear I.N. Galidakis: On Jul 24, 9:58 am, "I.N. Galidakis" <morph...(a)olympus.mons> wrote: > dlzc wrote: > > Dear I.N. Galidakis: > > [snip] > > >> In other words, if I rotate a 532 nm laser > >> beam with a given angular frequency omega, > >> what would be the Doppler shift for an > >> observer at radius ~r, where omega*r=c? > > > You'd have a redshifting of the light source, > > due to time dilation, then you'd have whatever > > classical Doppler effect you'd see based on > > the relative motion. Similar to an SR-only > > problem, only with the time dilation being > > more complex due to acceleration. > > Thanks. The time dilation I was able to > calculate, but I cannot seem to see why > I'd get a red/blue-shift (relativistic or not). > > The way I understand it, the _linear_ velocity > at the tip of the beam (at distance r) is > perpendicular to the tip's orbit (circle of > radius r), so I cannot see how it contributes > to a Doppler shift for an observer that gets hit > by the beam head on. How do you *not* see a case for classical Doppler shift? It works for cars at much less than c... even though that is a two-way trip. > Any help? I need the actual calcs for the > red/blue-shift for an observer that gets hit by > the beam once for every period of the rotation. Sorry, I just don't see where you'd have a problem here. Not sure if you are looking at light as particles, or light as a wave, or how you'd like to treat it. David A. Smith |