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A Laboratory Experiment for Astronomers ("Look-Back")
(Pursuant to my posting immediately above)
Ah no, the momentum should be the same because both photon speed and wavelength are half of what we think, if the z=1 photon is travelling at c/2. So the momentum equation yields the same result, darn it. Modelling the z=1 photon as travelling at c/2 is (so far as I can tell) consistent with all other observed photon properties. So we need to do that occultation-based observation -- or whatever other physical property that would be affected by photon speed. By the way, I need to mention this: most people model the photon as a physical object which travels continuously from A to B. With that model, people might find problems with a universe in which photons are whizzing around at different speeds. The reason I'm agnostic about that is because I don't believe photons exist in mid-flight -- John Wheeler's delayed-choice experiments have specifically excluded such photons, I believe. I've occasionally posted my photon model on these newsgroups, and it's posted at http://quasars.org/photon.txt . The model is, of course, consistent with all observed photon properties. Eric |
#12
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A Laboratory Experiment for Astronomers ("Look-Back")
2.11.2014 18:53, Eric Flesch kirjoitti:
Yes, and aberration was mentioned although I'm not seeing how that would work. The observed direction of an astronomical target will move to the direction of the observers movement by the quantity: a = (v/c')*sin(theta) whe v is observers velocity [km/s] c' is the speed of light [km/s] theta is the angle between the observers motion and the true position of the object [radians]. When using the speed of light (c' = c approx 3*10**8 m/s) the maximum aberration due to motion of Earth around the Sun is approximately 21''. This can be readily detected and indeed has to be accounted for in some observations. If for some targets c' = c/2 they would show aberration that would be twice larger than for target for which c' = c. Thus extragalactic targets would dance around closer objects in the same exposure to the rythm of Earths seasonal movement. No such effect is observed. H Tavaila |
#13
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A Laboratory Experiment for Astronomers ("Look-Back")
On 11/4/14, 11:26 AM, Steve Willner wrote:
In article , Eric Flesch writes: If Barbour's well-published "relative scale" is operative, then z=1 photons were emitted under an earlier "scale" state, ald it is possible that they are travelling at speeds slower than c I think this is pretty much ruled out by existing observations. Optical spectrographs measure wavelength. Radio spectrographs measure frequency. Both methods give the same redshift for high-z galaxies; therefore the photons have to be traveling at the same speed as any other photons to within the combined measurement uncertainties. Further: This is inherent in the photon gas model Black Body expression of observed universe CMBR where wavelength and frequency calculation are dependent on c within the Stefan constant 2*pi^5*Boltzmann^4/(15*c^2*hbar^3) Richard D Saam |
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A Laboratory Experiment for Astronomers ("Look-Back")
On Wed, 05 Nov 14, Harri Tavaila wrote:
If for some targets c' = c/2 they would show aberration that would be twice larger than for target for which c' = c. Thus extragalactic targets would dance around closer objects in the same exposure to the rythm of Earths seasonal movement. No such effect is observed. Thanks for that excellent explanation, Harri. So if the light from z=1 quasars travel at c/2, then their maximum aberration would be 40 arcsec instead of the 20 arcsec of stars. So we would see z=1 quasars move as much as 20 arcsec against the stellar background. Gosh, can't say I've noticed that! Before I raise the white flag all the way up the pole (it's mostly up :-), one anomaly stands out in my cataloguing, and that is there is a patch of sky at about -30 Dec covered by the 2QZ survey where DSS plots the quasars about 4 arcsec from the 2QZ-given co-ordinates -- with plenty of scatter. I need to check that place to see if there is any support there for my hypothesis, i.e., that the positional variance is proportional to redshift. I'll report back if it does, but otherwise it is my hypothesis which is stone cold dead. Thanks very much Harri and all. Eric |
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A Laboratory Experiment for Astronomers ("Look-Back")
In article ,
Eric Flesch writes: Therefore if Neptune occults a z=1 quasar, the entire occultation would be seen after Neptune has passed. Less dramatic than an occultation timing event, but 3C 273 passes behind the Sun each year. Its position as affected by gravitational light bending has been used as a test of GR. I wouldn't expect that test to agree with GR if the speed of radio waves from 3C 273 differs from c. Aberration, as others have mentioned, also provides a strong test. The radio astrometric reference frame is defined by quasars at a wide range of redshifts. If they moved with respect to each other at different times of year, that would be noticed. (Measurement precision is at the micro-arcsec level.) An optical spectrograph measures the wavelength of received light relative to the grating spacing. Speed of photons doesn't matter; it's just geometry. (Wavelengths will, of course, change between air and vacuum, but that's known and accounted for in the calibration.) -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
#16
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A Laboratory Experiment for Astronomers ("Look-Back")
On Fri, 07 Nov 14 12, Steve Willner wrote:
An optical spectrograph measures the wavelength of received light relative to the grating spacing. Speed of photons doesn't matter; it's just geometry. (Wavelengths will, of course, change between air and vacuum, but that's known and accounted for in the calibration.) I must confess I didn't realize they worked like that, thought prisms were used. Still unsure about detaching wavelength from c, but it doesn't matter since aberration shows my hypothesis is false. So whatever "spatial expansion" consists of, it overtakes whatever came before (outside of gravity-bound galaxy groups etc). |
#17
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A Laboratory Experiment for Astronomers ("Look-Back")
In article ,
Eric Flesch writes: I didn't realize they worked like that, thought prisms were used. Nearly all astronomical spectrographs operating today use diffraction gratings, which allow much higher dispersion than prisms can produce. Prisms are sometimes used as cross-dispersers in "echelle spectrographs," which spread several orders of grating spectra over a 2-d focal plane. Prisms are also used when low resolution but wide wavelength coverage (more than an octave) is needed. Still unsure about detaching wavelength from c Not sure what you mean here. A grating (plus geometry) directly measures wavelength at the grating location. For any wave, product of frequency and wavelength is speed. -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
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