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- Path: sparky!uunet!zaphod.mps.ohio-state.edu!uwm.edu!ogicse!das-news.harvard.edu!offa!love
- From: love@geophysics.harvard.edu (Jeff Love)
- Newsgroups: sci.physics
- Subject: Re: Blue Sky
- Message-ID: <1992Jul27.224915.15755@das.harvard.edu>
- Date: 27 Jul 92 22:49:15 GMT
- Article-I.D.: das.1992Jul27.224915.15755
- References: <Jul.27.14.46.15.1992.6472@ruhets.rutgers.edu>
- Sender: usenet@das.harvard.edu (Network News)
- Reply-To: love@geophysics.harvard.edu
- Organization: Dept. of Earth & Planetary Sciences, Harvard University
- Lines: 48
-
- In article 6472@ruhets.rutgers.edu, bweiner@ruhets.rutgers.edu (Benjamin Weiner) writes:
- >Jeff Love writes:
- >>Ok, so Rayleigh scattering explains why the sky is blue: blue light is
- >>scattered more than red light. I guess I don't like this explanation since
- >>I don't know why Rayleigh scattering preferentially scatters blue light.
- >>Is their a **classical** (i.e. no QM) explanation for this effect? If DaVinci
- >>got it right as Jackson claims in his book, then there must be a classical
- >>arguement.
- >
- >Have you actually tried reading Jackson's explanation? As a hint,
- >Jackson's title is _Classical Electrodynamics_. More to the point,
- >if _Rayleigh_ got it right in 1871 there must indeed be a classical
- >explanation, namely Rayleigh's. [Rayleigh, Phil Mag XLI, 107, 274,
- >(1871), and Phil Mag XLVII, 375 (1899), refs cribbed from Jackson]
- >Basically the assumptions that go into the explanation are that
- >molecules have predominantly electric dipole polarizability, and
- >that they are small compared to the wavelength of the light.
- >Incidentally, I believe that da Vinci understood that blue light
- >was scattered preferentially, causing the blue sky, but didn't know
- >why. (He certainly didn't derive a k^4 dependence). I don't think
- >one can claim that his argument is based on "classical physics" in
- >the usual sense.
- >
- >BTW, to Al Kriman: Perhaps if prophecies of the decline of atmospheric
- >ozone are true, we will eventually see a more violet sky.
- >
- >Ben Weiner
- >
- >I don't think of myself as a classical physicist, rather a
- >twelve-tone physicist.
-
-
- Wow. Okay, maybe I didn't read Jackson's book before I posted my question.
- I guess what I was hoping for was a heuristic arguement as to why blue light
- is scattered whilst red light is not (at least not as much), or maybe a simple
- dimensional arguement could yield the k^4 dependence; I admit that I haven't
- tried to put one together. I see that the stuff in Jackson regarding Blue
- Sky is classical, so I misspoke. But not all of Jackson is classical, despite
- the title ( hbar does appear a times ). I was hoping for a qualitative
- or semiquantitative explanation, not a rigorous explanation.
-
- The "explanation [is] that molecules have predominantly
- electric dipole polarizability, and that they are small compared to
- the wavelength of the light" doesn't really help me. I suppose I could
- go do some research and learn the answer that way, but I thought I'd
- use the net instead.
-
- Jeff Love
-