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"Babak Sehari" wrote in message ... Hi I recently noticed that the sun is whiter than I used to remember it when I was a child. The sun I remember was yellow. A few weeks ago I was driving with sun in my eyes and the Sun looked very very white. Change in color could indicate many things, among those are change in the temperature of the sun, change in atmospheric condition on earth etc.. I wonder do any body have any data that measures sun's average radiation at any particular frequency or wave length? Does these levels vary with 11 year sun's cycle? This gave me the idea that the sun might have longer cycles than 11 years. These cycles could take say 100s or 1000s of years, and these cycles may have caused the climatological change on earth. Reagrds, Babak Another thing is the fact that you say you noticed this when you were driving with the sun in your eyes. Actually, that's a more likely explanation that atmospheric conditions -- sorry to have overlooked it before. Someone can explain how there is some threshold beyond which your eye and brain cannot decode brightness into meaningful data, and why staring at the sun, in fact, can blind a person entirely. -- ___________________________ Bonnie Granat GRANAT EDITORIAL SERVICES http://www.editors-writers.info Overnight service available |
#23
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"Bill Sheppard" wrote in message...
... ---------------------------------------------------------------------------- Painius wrote, ...i worked on TACANs in the military. It's a very different principle than Doppler's effect, which does not require wave reflections. Yes, TACAN (acronym for TActical Air Navigation, circa 1955) was a ground-based nav system using UHF radio signals to determine distance and bearing of an aircraft from a transmitting station. No Doppler effect involved. Police radar is an entirely different animal from TACAN, and is TOTALLY Doppler-based. A pulse of fixed-frequency RF is sent out, reflected from the target, and received back; if the frequency of the reflected pulse is unchanged, the target is not moving; if the frequency is higher, the target is approaching, and if lower, the target is receding. Software in the unit computes the actual speed of the target based on the frequency shift. It's entirely Doppler based. And it still does not explain how light waves coming from light sources that are moving toward us are scrunched together, or how such waves from sources that are moving away from us are stretched apart. How so? Think of a ripple propagating across the surface of a pond. A water wave is really a transverse wave, albeit in the vertical plane. It's analogous ro a vertically polarized light wave (such as you'd get thru a polaroid filter). Now think of a buzzing house fly or a bee such as Bert might harness in one of his experimentsg; the buzzer is affixed to the end of a BBQ skewer and touched to the water's surface so it sends out concentric waves as it buzzes. Now move the poor buzzing critter across the pond's surface. Note that the waves it radiates are no longer concentric; the waves 'ahead' are compressed while the waves 'behind' are stretched. Pure Doppler. oc To reply by e-mail please use anti-spam address: oldcoot88atwebtv.net Change 'at' to@ ---------------------------------------------------------------------------- Interesting stuff, Bill, thanks! I wasn't aware that Police radar uses the Doppler effect. But it stands to reason because the radar mile produces precise *distance* measurements, while *velocity* measurements appear to require the addition of the Doppler effect for precision. And thanks for the great transverse water wave analogy! Got rid of some of the muddy, mucky water in my brain as regards the Doppler-Fizeau effect. Of course there is still the nebulous part about how the compressing and stretching of radiation waves from moving celestial objects can be represented by the movement of an element's spectral lines to the right or left (toward the blue or red end of the spectrum). This still sounds like a big leap to me. happy days and... starry starry nights! -- Life without love is A lamp without oil, Love without prejudice A world without soil, Tool without toil. Paine Ellsworth |
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Hi oc and Painius The illusion that the original wave made by the rock
thrown in a pond travels from when the water is pushed down by the rock,and this same wave goes to the shore of the pond. To be washed up against the sandy shore. When I was a kid I liked watching this illusion. Bert |
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Painius wrote:
Of course there is still the nebulous part about how the compressing and stretching of radiation waves from moving celestial objects can be represented by the movement of an element's spectral lines to the right or left (toward the blue or red end of the spectrum). This still sounds like a big leap to me. Given that blue light has shorter wavelengths than red, why do you find this idea "a big leap"? With regard to your description of the phenomenon as "nebulous", note that the shifts can be measured very precisely. -- Odysseus |
#26
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Bonnie Granat wrote:
"Babak Sehari" wrote in message ... Hi I recently noticed that the sun is whiter than I used to remember it when I was a child. The sun I remember was yellow. A few weeks ago I was driving with sun in my eyes and the Sun looked very very white. Change in color could indicate many things, among those are change in the temperature of the sun, change in atmospheric condition on earth etc.. I wonder do any body have any data that measures sun's average radiation at any particular frequency or wave length? Does these levels vary with 11 year sun's cycle? This gave me the idea that the sun might have longer cycles than 11 years. These cycles could take say 100s or 1000s of years, and these cycles may have caused the climatological change on earth. Reagrds, Babak It is likely your local atmospheric conditions causing you to think the sun has changed color. It was as beautiful a yellow light today as have seen in all my 56 years. It's yellow. You may be viewing it, however, through thin clouds and not realize it. On a day with bad smog here, at midday, it can be red. But on a normal, sunny day, it is yellow, not white. Dear Babak If you go to http://www.spaceweather.com and the follow the link to the soho sattalite site, you will find ample evidence that the Sun's "color" has, in fact, changed. The 11 year "Solar Max", which was in the year 2000, has completed an unprecedented 4th year, and is now going into a 5th year, with a huge number of "Sun Spots", and "Coronal Holes". If you check out the spaceweather archives, you will find that the Earth has been having "Aurora Events" on an almost daily basis, for the last year and one half. Also, about a year and a half ago, the Sun's Magnetic Poles reversed; the South Pole is at the "top", aligned with the Earth's Magnetosphere's North Pole. The meaning of all of the above, is that the Sun is putting out lots more energy in the high-frequency Ultra-Violet, and X-Ray bands, and less in the visable and infra-red; also much stronger Interplanetary Magnetic Field and more Protons which ride that field to the Earth and the other Planets. It's those Protons which cause those beautiful Auroras. Yes people, something strange and unprecidented is going on with the Sun; Jupiter too!! Unfortunaly, the current bunch of "scientists" at NASA, who should be paying attention to this kind of thing, seem to be the same kind of "political scientists" that ignored the Space Shuttle safety issues. My own opinion, with which the NASA scientists disagree, is that the increased energy output from the Sun is the root cause of all that very, very strange weather we've been having for over a year now. Yes, Babak, there are many, many, Solar cycles, within cycles, within.......that's why the ancient Astronomers were so obsessed with Astronomy and spent lots of time and money on such. It didn't have a thing to do with worshiping their "Gods", as the Western, Christian, Archiologists would have us believe; just because said Ethno-Centric Westerners have that obsession themselves. It had to do with the fact, of which the Ancients were well aware, that when certain Celestial alignments occur, the weather changes; crops fail, kingdoms fall, lean hungry barbarians come out of the East! The NASA "Scientists" rely on a data-base, collected since Galeleo first discovered Sun Spots, to correlate Earth's Weather with Solar Events. This "Statistical" approach does not allow for anything not-seen since the collecting of the statistics began; like The Little Ice Age, for instance; or the fact that the Sahara has a wet/dry cycle of about ten thousand years; and a wet period is long overdue! |
#27
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"Odysseus" wrote...
in message ... Painius wrote: Of course there is still the nebulous part about how the compressing and stretching of radiation waves from moving celestial objects can be represented by the movement of an element's spectral lines to the right or left (toward the blue or red end of the spectrum). This still sounds like a big leap to me. Given that blue light has shorter wavelengths than red, why do you find this idea "a big leap"? With regard to your description of the phenomenon as "nebulous", note that the shifts can be measured very precisely. -- Odysseus Thanks, Odysseus... i'm not sure i can put it into words... So if we look at the light from a star, and if we analyze the spectrum to get, say, a hydrogen signature, then we can expect that if the star has a radial velocity in our general direction the compressed light waves will be expressed by a spectral shift of the hydrogen signature away from the red end and toward the blue end. And if the star has a radial velocity going away from us, then the stretched out light waves will be expressed by a spectral shift of the hydrogen signature away from the blue end and toward the red end. While these basics appear to hold water, the leaps come when we delve a little deeper... Some questions i have are... can an *acceleration* of a celestial object either toward us or away from us be detected using the spectral shift? can the spectral shift be used some way to determine the precise *direction* of the celestial object (to include its radial *and* transverse vectors)? is the spectral shift just confined to velocity with no acceleration and to just the radial velocity without being able to account for transverse velocity? how do we know that, say, an increased red shift means that the object is farther away going at an increased radial velocity? Couldn't an object that has a small red shift actually be farther from us than one with a large red shift if the nearer object is going more directly away from us? What if the farther object has much more of a transverse motion than the near object? Wouldn't the farther object's radial velocity be much less, thereby giving us a smaller red shift? And yet it is still farther away? Carpenters! happy days and... starry starry nights! -- "Oh give me please the Universe keys That unlock all those mysteries!" You pay your fees, you find some keys That keeps you always groping. "Oh give me please the Happiness keys That ease the pain of biting fleas!" Today you seize you need no keys, That door is always open. Paine Ellsworth |
#28
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Painius wrote:
While these basics appear to hold water, the leaps come when we delve a little deeper... Some questions i have are... can an *acceleration* of a celestial object either toward us or away from us be detected using the spectral shift? can the spectral shift be used some way to determine the precise *direction* of the celestial object (to include its radial *and* transverse vectors)? is the spectral shift just confined to velocity with no acceleration and to just the radial velocity without being able to account for transverse velocity? Good questions. As far as I know, the answers are no, no, and yes ... but then again, I have only the barest grasp of relativity between "inertial frames of reference", so where accelerations are involved I get out of my depth. I'm pretty sure, though, that there's no way to 'read' tangential velocity from a spectrum. how do we know that, say, an increased red shift means that the object is farther away going at an increased radial velocity? Couldn't an object that has a small red shift actually be farther from us than one with a large red shift if the nearer object is going more directly away from us? What if the farther object has much more of a transverse motion than the near object? Wouldn't the farther object's radial velocity be much less, thereby giving us a smaller red shift? And yet it is still farther away? Certainly. Stars in our own galaxy have all manner of red and blue shifts as viewed from our particular moving platform, and they're more or less independent of distance. But we only know the true velocities of the comparatively few nearby stars that have exhibited measurable "proper motion" over the course of the paltry few centuries we've been observing them, providing a tangential component to go with the radial one seen in their spectra. When it comes to "cosmological" red-shifts of distant galaxies, though, it's thought -- or assumed -- that the 'true space motions' are comparatively small, because to the extent we're able to cross-check the red-shifts against other means of estimating distance (i.e. the "standard candles" of cepheids and supernovae) they increase fairly uniformly with distance, the trend overwhelming individual motions once one looks far enough away. The explanation for this trend is, of course, space expansion. But in a sense it's only Occam's razor -- or as Einstein put it, the idea that "God is subtle but not malicious" (read "nature" for "God" if you prefer) -- that inclines us to rule out individual space motions as the cause of galactic red-shifts, until someone can come up with either a reliable independent means of measuring the distances or the motions, or OTOH a different explanation for the "Hubble constant" that's consistent with observations. It's hard to imagine another reason for everything back to the cosmic microwave background to seem to be running away from us, and it only makes matters worse if we picture the vectors randomly filling the 'far' hemisphere but never pointing into the 'near' one! Note that a large tangential velocity combined with a large red-shift would imply a still larger 'net' velocity (Pythagoras' theorem), so one would have to explain why all these objects should be moving so rapidly *through* space if they're not moving *with* it, so to speak. However, there are a few 'anomalous' cases of galaxies with red-shifts very different from those of what appear to be other members of their cluster, so we still have a lot to learn about galactic motions. See http://www.astroleague.org/al/obsclubs/arppec/arphalt.html for an account of Halton Arp's criticism of the space-expansion explanation of cosmological redshifts; other researchers point to correlations between galactic types and their redshifts (independent of distance) that they claim to indicate that the 'conventional wisdom' is wrong or seriously incomplete. It's depressing to consider that it will take many thousands or millions of years of observations to detect any tangential motion at all in extragalactic objects, which might settle some of these questions -- someone needs to find a way to look further into the past than astronomical distances take us or, alternatively, the universal 'fast forward' button! -- Odysseus |
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