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Arago vs Vogel
"OG" napisal w wiadomosci ... On 30/10/2011 20:31, Szczepan Bialek wrote: napisal w wiadomosci ... On 30/10/2011 15:37, Szczepan Bialek wrote: It seems to me that the only way to measure the angle of refraction is to measure the absorption line position. You are mistaken. Arago's experiment simply looked at the angle or refraction. But the line position was the same for stars: "http://www.archive.org/stream/spectrumanalysis00esterich/spectrumanalysis00esterich_djvu.txt "Indeed, these observations would scarcely be possible, were it not that in the dark lines crossing the spec- tra of the sun and fixed stars, the places of some of which may be accurately ascertained, we have fixed positions in the spectrum, the degree of refrangibility or wave-length of which may be determined beforehand, both for the sun and terrestrial substances, and also for the stars or other sources of light supposed to be at rest. " What you can't see, because Fig X is not included, is that the positions of the lines is displaced because of the relative movements. So, the line position was NOT the same. The following text makes this clear. Below is the problem of the radial speeds of planets. Also the result is null: http://articles.adsabs.harvard.edu//...00243.000.html You are mistaken. That experiment was to detect oxygen lines in the atmosphere of Venus. You are right. The Vogel's result do not fit to them. Why not? In all textbooks is wrote that Arago, Mchelson-Morley and Truton-Noble fit together. So what (in your own words) is the problem with Vogel's result? The problem will appear if it is confirmed. What problem? Now it is mentioned only in Wiki. Without any comments. If it is right than: "This experiment, which demonstrated the effect of the earth's orbital movement on refraction is of great historical interest. " Arago's result yes. I still don't know why you think there's a problem with Vogel's result. I know that in the whole World students are told that at measuring of the radial speed of stars they should take into account the orbital speed of the Earth. Yes. The reason is the Vogel's result. Sort of. More accurately, Vogel's result is a measurement of the earth's orbital speed, hence, it needs to be taken into account. Arago's result is "yes" and Vogel's result is "yes". Is it possible? Of course it's possible. The speed of the incoming light is not changed by the relative motion of the source and detector (Arago), but the frequency of the spectral feature is changed (Vogel). It is some problem because in 1905 Einstein wrote that it is impossible to detect the orbital speed. So are the two possibilities: 1. Brace and Einstein did not know about Vogel's result. 2. Vogel's result become wrong. You are mistaken. Einstein wrote no such thing. What he wrote (in effect) is that the earth's orbital speed has no effect on the measured speed of light, which is the explanation behind Arago's null result. For me refraction = line position ("the dark lines crossing the spectra of the sun and fixed stars"). That's a mistake. The only detail which can be measured are the position of that dark lines. Arago used the achromatic prism. So you agree he couldn't have been looking at spectral lines if he was using an achromatic prism. What he measured was the simple angle of refraction. He tried to see if the different speed of the Earth relative to the source star made a difference to the angle of refraction. It doesn't But the next used the dark lines. But is possible that Arago's measurements and that to 1904 were not accurate. No, they were accurate enough - Why than the Vogel's result is totally unknown? Because he measured something that was not unexpected. The spectra methods are a little mystery. And what with the radioscopy: "In 1931, a Bell Telephone engineer, Karl Jansky (1905-1950), was trying to find where the interference disrupting transatlantic radiophone circuits came from. He discovered that some of the radio noise was not from the Earth--it was extraterrestrial. The primary source was the center of the Milky Way, in the constellation of Sagittarius. In 1936, an Illinois radio engineer, Grote Reber (b. 1911), pursued the phenomenon farther." From: http://physics.gmu.edu/~jevans/astr1..._txt.htm#5.2.1. The radio frequences are easy to measure. Are there the diurinal and annual effests? S* |
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