Astronomy Question of the Week 01/22/06

[tfwthom]

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[eosophobiac]

I'm no professional meteorologist or astronomer by any means but wouldn't it be blue?<br /><br />(Is this a trick question?)<br /><br /> <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[newtonian]

I thought it would be blue also.<br /><br />I'm going to be blue if I am wrong!<br /><br />Btw - a myriad in the Bible is 10,000 - 10,000 particles is not very many!

 

[newtonian]

TFWThom - Thank you for your thought provoking questions.<br /><br />OK, my skies are grey today here in SE Louisiana - plenty of clouds containing microscopic droplets of water condensing on dust particles.<br /><br />However, these cloud particles when visible are no longer microscopic - no?<br /><br />Also, there are likely billions, not merely myriads - if you mean 10,000's, of dust particles and not quite microscipic water droplets in clouds.<br /><br />The dust is already in the atmosphere before clouds appear. <br /><br />However, the confusing part of your question is that you say water droplets not vapor. <br /><br />I have seen clouds instantly appear on mountains out of invisible air - it is an awesome and amazing sight! But that is blue when vapor, then becomes grey water droplets (due to diffraction of light - it gets as complicated as a rainbow!).<br /><br />Had you said microscopic particles of water (molecules are particles) I would have been sure of the answer.<br /><br />I answered blue, btw - because the sky is blue because of its composition which includes dust particles and water vapor.<br /><br />What makes me unsure is vapor vs. droplets.<br /><br />When water vapor condenses (aka precipitates out) into droplets on dust particles it forms clouds or fog which is grey.<br /><br />Too bad I couldn't give both answers!!!<br /><br />I am obviously having second thougts about my answer - I felt blue.<br /><br />Actually, I'm happy!

 

[dragon04]

The Earth's atmosphere <b> does </b> contain myriads of dust paticles and microscopic droplets of water even on a sunny day.<br /><br />And the sky is blue <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[yevaud]

This question is ambiguous.<br /><br />As noted, the atmosphere does contain vapor and droplets of water, and dust. This then scatters light via either Rayleigh scattering or Mie scattering. And the overall effect is a blue sky, tending towards red at the horizons when the sun is setting (pathway of insolation now travelling through an increased optical depth of atmosphere).<br /><br />The answer would really be determined by the nature and composition of the dust and water. How much? Dimensions are what? Large enough that Rayleigh scattering predominates, or where Mie scattering does?<br /><br />Nevertheless, my answer is <font color="blue"><b>Blue</b></font> since this is what we see with our atmosphere, which already contains what was posted. No further answer is possible without much more information. <br /><br />(Edited to correct boneheaded error of grammar ) <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[CalliArcale]

I agree -- blue, but the answer depends on actual quantity and composition of the dust. And the quantity of the water -- enough water and it might be overcast! <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[tfwthom]

Digging in my hard drive I ran across this...<br /><br />THE PHYSICISTS' BILL OF RIGHTS <br /><br />(Author Unknown) We hold these postulates to be intuitively obvious, that all physicists are born equal, to a first approximation, and are endowed by their creator with certain discrete privileges, among them a mean rest life, n degrees of freedom, and the following rights which are invariant under all linear transformations: <br /><br /><br />1. To approximate all problems to ideal cases. <br /><br />2. To use order of magnitude calculations whenever deemed necessary<br />(i.e. whenever one can get away with it). <br /><br />3. To use the rigorous method of "squinting" for solving problems more<br />complex than the addition of positive real integers. <br /><br />4. To dismiss all functions which diverge as "nasty" and "unphysical." <br /><br />5. To invoke the uncertainty principle when confronted by confused<br />mathematicians, chemists, engineers, psychologists, dramatists, and<br />other lower scientists. <br /><br />6. When pressed by non-physicists for an explanation of (5) to mumble in<br />a sneering tone of voice something about physically naive<br />mathematicians. <br /><br />7. To equate two sides of an equation which are dimensionally<br />inconsistent, with a suitable comment to the effect of, "Well, we are<br />interested in the order of magnitude anyway." <br /><br />8. To the extensive use of "******* notations" where conventional<br />mathematics will not work. <br /><br />9. To invent fictitious forces to delude the general public. <br /><br />10. To justify shaky reasoning on the basis that it gives the right<br />answer. <br /><br />11. To cleverly choose convenient initial conditions, using the<br />principle of general triviality. <br /><br />12. To use plausible arguments in place of proofs, and thenceforth refer<br />to these arguments as proofs. <br /><br />13. To take on faith any principle which seems right but cannot be<br />proved. <br /><br /> <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>

 

[Saiph]

well....Mie scattering is strongest for when particles are ~ the size of the wavelength...<br /><br />So if you load the atmosphere with dust and water droplets...that's closer to the red-wavelength than blue.<br /><br />So it would tend to skew the sky towards red, away from blue.<br /><br />IIRC. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[tfwthom]

(Total Votes: 13) <br />Red <br /> 3 (23%) <br /> <br />Blue <br /> 9 (69%) <br /> <br />Brown <br /> 1 (07%) <br /> <br />Green <br /> 0 (0%) <br /> <br />Black <br /> 0 (0%) <br /> <br />The answer is............. Blue<br /><br />Sunlight is a spectrum of all colors and is thus a mixture of light of many wavelength. The shorter wavelength portion of the spectum entering our atmosphere is scattered evenly by the dust and water particles, so that it is blue light that reaches our eyes from all directions. Above our atmosphere astronauts observe a brilliant white sun against the blackness of space.<br /><br /><br /> <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>