HDTenEightyP/NetNews huggingface dataset:
From: platt@watson.ibm.com (Daniel E. Platt)
Subject: Re: How much does fog dampen sound?
Date: Mon, 27 Jul 1992 13:30:24 GMT
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM T.J. Watson Research Center

In article <1992Jul21.021346.18215@ccu1.aukuni.ac.nz>, ecmtwhk@ccu1.aukuni.ac.nz (Thomas Koenig) writes:
|> Wandering around in the fog recently, I wondered wether the apparent
|> dampening of sound was just imagination, because of different visual
|> aspects, or real.
|> 
|> I've got a mechanism for the dampening:  As sound waves move past water
|> droplets, the sound - induced speed difference between the droplets
|> and the air means there is a resulting force on the droplets because
|> of drag effects; they also move a bit, therefore there is energy
|> dissipation.

I have one BIG hint for you:  Water droplets are much smaller than
audible sound waves.  This would be true for very large raindrops much
less fog droplets.

|> 
|> Influences would be the concentration of liquid water in the air,
|> drop size distribution and sound frequency (plus the whole range of
|> physical properties of the two substances involved, which depend
|> on temperature and pressure).
|> 

The density of air will be a bit smaller with the water vapor in it.  The
isentropic compressibility (Bulk modulus) will be somewhat different since
pressure waves are now participating in the equilibrium between water
droplets and water vapor in the air (nucleation, water droplet growth and
shrinking as the wave goes through)(?).  The droplets suspended in the air
are coupled to the air's motion (F=ma where F = a exp(i*omega*t), m = mass
of droplet, F involves coupling between air velocity field and water
droplet).

My guess is the mechanics would be the biggest contributor (droplet growth
given pressure waves wouldn't be a big contributor).

|> Has anybody ever checked this effect?
|> Is it really large enough to be noticable?
|> Failing that, does anyone have numbers on fog drop size distribution
|> so I could do the calculations myself?
|> -- 
|> Thomas Koenig, ecmtwhk@ccu1.aukuni.ac.nz, ib09@rz.uni-karlsruhe.de
|> The joy of engineering is to find a straight line on a double logarithmic
|> diagram.

Dan
From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: Converting the masses
Organization: Simon Fraser University
Date: Mon, 27 Jul 1992 19:12:59 GMT

In article <mcirvin.711904014@husc8> mcirvin@husc8.harvard.edu (Mcirvin)
writes:
>palmer@sfu.ca (Leigh Palmer) writes:
>
>> "Mass" as you use it
>>is equal to neither inertial nor gravitational mass as those terms apply to
>>any system more complicated than a particle at rest! 
>
>Which only illustrates that those concepts are only really useful in
>the context of Newtonian physics, IMHO.
>
>To further confuse the
>>beginning physics student you could explain that the mass of that lump of
>>matter is independent of its temperature. 
>
>Actually, neither definition of mass would be temperature-independent,
>if you define it for the whole lump of coal.  When you raise the
>temperature, the energy in the rest frame increases!  The sum of
>the masses of all the particles is perhaps temperature-independent,
>but as you complained before, that's not the mass of the lump.

Exactly my point. The existence of an internal degree of freedom in a lump
of coal which affects its mass vitiates the particle physicists' definition.
Used outside particle physics this convention has no conspicuous advantages,
and indeed it may lead to conceptual problems of its own.

Leigh Palmer
From: sichase@csa3.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: "What's New" July-24-1992
Date: 29 Jul 92 20:10:49 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: na
Reply-To: sichase@csa3.lbl.gov
NNTP-Posting-Host: 128.3.254.198
News-Software: VAX/VMS VNEWS 1.3-4   

In article <1992Jul29.182755.426@murdoch.acc.Virginia.EDU>, crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes...
> 
>     This 'new engineering' thread is probably not a fruitful thread
>     to pursue since a 'safer design choice' is not well-defined
>     in this context.  I 'know' that a space station can be put
>     in orbit that will satisfy the performance objectives.  I do not
>     'know' that such can be done for the SSC.  Which is 'safer'
>     in this context.
> 

Well, the designers of the SSC claim that their design meets or exceeds all
the design objectives.  Why would you doubt their claim, based upon zillions
of hours of computer simulation, more than you would doubt the designers 
of the space station?  

-Scott
--------------------
Scott I. Chase			"The question seems to be of such a character
SICHASE@CSA2.LBL.GOV		that if I should come to life after my death
				and some mathematician were to tell me that it
				had been definitely settled, I think I would
				immediately drop dead again."      - Vandiver
Newsgroups: sci.physics
From: mmm@qedqcd.rye.ny.us (Mike Miskulin)
Subject: Re: Blue Sky
Organization: High Energy Concepts
Date: Tue, 28 Jul 1992 02:42:59 GMT

In article <BrzH7H.DJw@acsu.buffalo.edu> kriman@acsu.buffalo.edu (Alfred M. Kriman) writes:

>   It is well known that our eyes are in fact most sensitive in the
>_green_.  My understanding (though I am not a biologist) is that the


I can remember reading somewhere that we are in fact most sensitive to
yellow, at approximately the same wavelenght as light from our sun?

-- 
--------------------------------------------------------------------------------Mike Miskulin		mmm@qedqcd.rye.ny.us	70053,551@compuserve.com
--------------------------------------------------------------------------------
From: bweiner@ruhets.rutgers.edu (Benjamin Weiner)
Newsgroups: sci.physics
Subject: Re: Noah's formation: The rainbow
Date: 22 Jul 92 20:08:44 GMT
Organization: Rutgers Univ., New Brunswick, N.J.

jmc@SAIL.Stanford.EDU (John McCarthy) writes:
>I'm surprised at all of you.  Isn't the rainbow God's warning to Noah that
>
>"It won't be water but fire next time."

Oy vey!  No, it's a promise (the Covenant, natch) not a threat.
Although admittedly the gospel song does go:
"God gave Noah the rainbow sign,
 No more water but the fire next time."

Ben Weiner
applied theologian
From: aephraim@physics.Berkeley.EDU (Aephraim M. Steinberg)
Newsgroups: sci.physics
Subject: Re: Defining Photons
Date: 29 Jul 1992 00:49:39 GMT
Organization: University of California, Berkeley
Distribution: na
NNTP-Posting-Host: physics.berkeley.edu
Keywords: Relating photons E=MC^2 criticism

In article <24990@dog.ee.lbl.gov> sichase@csa2.lbl.gov writes:
%In article <mcirvin.712335342@husc10>, mcirvin@husc10.harvard.edu (Mcirvin) writes...
%> 
%>Or hydrogen, for that matter.  A professor in my department   
%>has discussed the possibility of doing "optics" with atoms.  I
%>don't know how close it is to being feasible.
%
%If I understand correctly, then the recent discussion of atomic "optics"
%does not have anything to do with the statistical properties of atoms, but
%rather that the technology of diffraction gratings has advanced to the 
%point of allowing people to construct atomic interferometers - which among
%other things would provide incredibly sensitive position and motion
%sensors since the de Broglie wavelength of an atom is orders of magnitude 
%shorter than that of visible light.  
%
%This would work for atoms of all spins.


For the most part, what you say is true.  However, recent advances in
laser cooling, optical molasses, etc, have begun to approach de Broglie
wavelengths on the order of the inter-atomic spacing, so there is hope
of studying Bose condensates of cooled atomic vapor, and in these cases,
the spin would definitely play an important factor.

If this thread originated by asking about fundamental differences between
bosonic and fermionic matter, the obvious things to think about are the
much-studied phases of 3He and 4He.

I've heard about atom interferometers being applied primarily for gravity
(or acceleration) measurements, or measurements of gravitational gradients,
but I haven't heard how they would be used as position or motion sensors,
and I have trouble believing they would do better than the Mossbauer effect
on the latter score.

-- 
Aephraim M. Steinberg                    | "WHY must I treat the measuring
UCB Physics                              | device classically??  What will
aephraim@physics.berkeley.edu            | happen to me if I don't??"
                                         |       -- Eugene Wigner
From: paul@mtnmath.UUCP (Paul Budnik)
Newsgroups: sci.physics
Subject: Watch your language, Was: mind-numbing gedankenexperiment
Date: 25 Jul 92 19:32:09 GMT
Organization: Mountain Math Software, P. O. Box 2124, Saratoga. CA 95070

In article <Jul.24.14.22.06.1992.9421@ruhets.rutgers.edu>, bweiner@ruhets.rutgers.edu (Benjamin Weiner) writes:

> wha?  They do nothing of the sort.  As was best said by somebody else,
If you are referring to <cramer.711988467@dirac> it was said more
carefully as well.
> operators separated by spacelike intervals commute.  They can't
> influence each other.  QED.  (that's quod erat demonstratum, not
> quantum electrodynamics)

Applying everyday language to mathematical results can be a tricky business.
Much of the confusion about Bell's inequality stems from errors of this type.
Bell's inequality will never be violated in a universe in which events
separated by space-like intervals never influence each other. Quantum
mechanics implys the inequality is violated. It is not violated in a way
that the influence is detectable *at the time it occurs* or in a way that
allows a signal to be sent. However space-like separated events are predicted
to *influence* each other instantaneously and this influence is detectable
at a later time.

Paul Budnik
From: vincent@reg.triumf.ca (pete)
Newsgroups: sci.physics
Subject: Re: Noah's formation: The rainbow
Date: 25 Jul 92 12:48:00 GMT
Distribution: sci
Organization: dept. of theophysics and cosmogyny
News-Software: VAX/VMS VNEWS 1.41

In article <-DS-cA@engin.umich.edu>, ewald@math.lsa.umich.edu 
(Brian Ewald) writes...
>In article <2A6DEF17.1804@ics.uci.edu> bvickers@ics.uci.edu 
(Brett J. Vickers) writes:

>>peterk@public.sub.org (Peter Kittel) writes:
>>>Is it only me or does the sky beneath a rainbow also appear lighter
>>>to others than the sky above a rainbow (or wait, was it the other way
>>>around?)? But anyway, for my eye there is definitely a jump in
>>>brightness of the background sky (normally rain clouds) from beneath
>>>to above the rainbow. Any explanation for this?
>>
>>Optical illusion?  Two fields of the same color, separated by a line
>>of a brighter or darker color, give the optical illusion that one half
>>is lighter than the other.  The trick is to cover the line and see that
>>they are the same.  I've never tried this with a rainbow.
>>
> 
>It isn't an illusion.  The darker band of sky between the primary and
>secondary rainbows is called Alexander's Dark Band, after Alexander
>of Aphrodisias who noted it around the year 200AD.  (The secondary
>rainbow is the often seen rainbow above the primary, about twice as
>wide, on average one tenth as bright, and with the colors apparently
>reversed; it is caused by an extra reflection).  The bows themselves
>are caused by the light going through the angle of minimum refraction
>in the water droplets, although some, albeit considerably less, is
>refracted more.  With the primary rainbow, this is beneath the rainbow,
>with the secondary, it is above.  Therefore the sky between the two
>bows is, in fact, darker.
> 
>Brian D. Ewald
>ewald@math.lsa.umich.edu

The sky below the lower rainbow is also actually brighter than the
surrounding sky. I presume this is due to reflection from the front
surface of the drops. I was once on a hilltop in Calgary at sunset,
when a full double rainbow occurred. ( It being flat prairie, the
rainbow was as large as it could be for a ground observer).
The point on the sky exactly opposite the sun, on the horizon, in the 
centre of the semi-circles defined by the rainbows, was suffused by 
golden light, the colour of the sunset. This is also similar to the 
halo one sees around the head of one's shadow on dewy grass. 

===========================================================================
Coming soon! The Maarten vander Loeb              Pete Vincent
Memorial University Bomb Disposal
Correspondence School! 
Newsgroups: sci.physics
From: mazzucch@ghost.dsi.unimi.it (massimo mazzucchi)
Subject: microvawe
Organization: Computer Science Dep. - Milan University
Date: Fri, 24 Jul 1992 16:38:27 GMT

Help me
I want to have information about microvawe for 
telcomunication and space
Who know and work in this sector can write me 
this my aderss

MAZZUCCH@HP1.SM.DSI.UNIMI.IT

thanks for your help
bye


Newsgroups: sci.physics
From: gsh7w@fermi.clas.Virginia.EDU (Greg Hennessy)
Subject: Re: "What's New" July-24-1992
Organization: University of Virginia
Date: Wed, 29 Jul 1992 00:15:51 GMT

In article <1992Jul28.235639.2933@murdoch.acc.Virginia.EDU>
crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes: 
#     P.S. I don't see APS officers testifying before Congress about
#     chiropractors or astrology

Gee, Dale, I was unaware that taxpayer dollars were being spent on
chiropractors or astrology. How much money is being budgeted on these
activities? 

--
-Greg Hennessy, University of Virginia
 USPS Mail:     Astronomy Department, Charlottesville, VA 22903-2475 USA
 Internet:      gsh7w@virginia.edu  
 UUCP:		...!uunet!virginia!gsh7w
Newsgroups: sci.physics
From: jtyrkko@vipunen.hut.fi (Juha-Petri Tyrkk|)
Subject: Re: Blue Sky
Reply-To: jtyrkko@vipunen.hut.fi (Juha-Petri Tyrkk|)
Organization: Helsinki University of Technology
Date: Thu, 23 Jul 1992 12:50:05 GMT

In article <BrrMJB.Brv@acsu.buffalo.edu> Matthew J. Bernhardt writes:

> 	On Mars, the atmosphere is different, and acts to produce a pink
> sky.

  I remember having heard that if there was not so much red dust in the
Martian atmosphere, Martian sky would be blue, too, looking about the
same as Earth sky at the altitude of 30 or 35 kilometers.

  Are there any gases that would scatter long light waves more than the
short ones?

                                                    Juha-Petri Tyrkko

                                                    jtyrkko@vipunen.hut.fi

Newsgroups: sci.physics
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Subject: Re: ZERO Nuclear impact (was: Is car pooling for real? etc)
Organization: University of Virginia
Date: Sat, 25 Jul 1992 19:52:46 GMT

In article <1992Jul25.194003.6019@murdoch.acc.Virginia.EDU> gl8f@fermi.clas.Virginia.EDU (Greg Lindahl) writes:
>In article <1992Jul25.192603.5892@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>
>> Usually, I'll just stick to making and rebutting arguments presented.
>
>Please rebut all the Scientific American articles that people have
>been refering to.

     Sure, if you'll rebut every argument made in AEC-NRC documents over
     the last 40 years.  I'll even tell you where they are.  Most of the NRC 
     stuff is strewn all over the floor of the journal floor of Clark Hall
     in the room in front of the copier (though the BNL and ANL stuff
     is in the remaining fiche cabinets).  Most of the AEC documents are 
     on microcard in the back room near the bathroom.  The microcard reader
     is in the room with the SAE fiche. 

     I'm not holding my breath.

     However, feel free to present in this forum what you think valid 
     arguments against what I have said, or for some position you think
     plausible, and I will be sure to consider a response.

                                 dale bass


--
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.physics
Subject: Re: Solar Concentration limit ?
Date: 25 Jul 92 05:08:06 GMT
Article-I.D.: u.1992Jul25.050806.2371
Organization: University of Washington, Seattle

> Let us consider a black surface exposed to the solar radiation (say f.i.
>F=1000 W/m2).

> Without concentration it reaches an equilibrium temperature calculated by :
>                    4
>             sigma*T  = F   (about 100 deg. Celsius)
>
> In a perfect concentrator, with a given concentration factor f, we have :
>                    4
>             sigma*T  = f * F
>
>For a given (great but non infinite) value of f, we can then obtain very great
>calues of T (we know that temp. > 3000 K are "easilly" obtained) but the
>problem is that in the formula herover it is theoretically possible to obtain
>for T a value of f.i. 7000 K, i.e. a temperature wich is over the sun
>temperature.

>We know on another hand that this is strcitly impossible due to the 2nd
>principle of thermodynamics.

        If one looks at the object and image of a simple lens system,
the brightness (watts/sq.cm/steradian) is the same.  Concentrating
by making a smaller image area increases the steradian measure of
the incident light cone.  Conversely, concentrating by reducing
the solid angle of incident light results in a larger image area.

        This implies that an imaging optical system consisting of simple
lenses doesn't break the second law of thermodynamics with respect
to radiant heat flow.  I suspect that generalizing to non-imaging
optics is possible, but the more puzzling case is nonlinear optical
effects (like holograms).  I think the second law of thermodynamics
is rather easier to apply than a full analysis of possible optical
concentrators!

        John Whitmore
From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Newsgroups: sci.physics
Subject: Re: Gyromagnetic ratio of the proton
Date: 27 Jul 92 23:51:47 GMT
Distribution: na
Organization: University of Virginia

In article <1992Jul27.205616.26838@murdoch.acc.Virginia.EDU> gsh7w@fermi.clas.Virginia.EDU (Greg Hennessy) writes:
>In article <1992Jul27.204759.26632@murdoch.acc.Virginia.EDU>
>crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes: 
>#     It also does not appear to be inside the Macintosh downstairs
>#     (we had all the protons removed during the last maintenence).
>#     By the way, does anyone know how to put it back together ...
>
>Well, of course Dale, if you remove all the protons from your Mac it
>then has a rather large negative charge, so all the peices are
>electrostaticaly repelling each other.

    I'm not using electrons either since the they were giving me
    a jolt every time I touched the keyboard.

                             dale bass
--
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926
From: stone@ccwf.cc.utexas.edu (WeiKai Shih)
Newsgroups: sci.physics
Subject: Digitizer or V-F converter
Date: 29 Jul 92 01:26:04 GMT
Reply-To: stone@ccwf.cc.utexas.edu (WeiKai Shih)
Organization: The University of Texas at Austin, Austin TX
Originator: stone@sleepy.cc.utexas.edu


      Does anyone happen to know where to find a commercial digitizer or vol-
tage to frequency converter which can take in the DC voltage and output a pulse
train with frequency proportional to the input voltage? I've tried many companies and most of them offer chips. It's not a big deal to build a NIM or CAMAC module by ourselves, however, a commercial one can save time. Any info is appreciated. Thank you! 

                                                      Victor Stone, 
                                                      UT-Austin
Newsgroups: sci.physics
Subject: Re: A long-winded primer on four-vectors (part 1)
From: mcirvin@husc8.harvard.edu (Mcirvin)
Date: 23 Jul 92 00:27:14 GMT

gast@next.ben-fh.tuwien.ac.at (Gast) writes:

>The article was a prety good overview about the subject of four-vectors.  
>Yet, two short remarks:

>Remark 1:
>If you don't set c=1, the coordinates of a point in a Minkowsky-space are  
>(if any doubt, consider the units):

> a
>x = (ct,x,y,z)  (a is an upper index)

>Therefore the transfromation above has to be

>   x -> x' = x cosh phi   + ct sinh phi
>   t -> t' = x/c sinh phi +  t cosh phi 

Right... I should have been more explicit about that.
Through the whole article I'm setting c=1 except where I explicitly
put it in.  But I put it in when I discussed the values of cosh
and sinh phi, which was a little inconsistent.

>Remark 2:
>Because of the metric there are two kinds of coordinates neccessary.
[description of covariant and contravariant vectors]

Right again... *that* I was omitting intentionally for simplicity;
what I call four-vectors are always "upper-index" or contravariant
vectors, in the article, except in the one spot where I define
a lower-index vector.

This becomes far more important in GR.

-- 
Matt McIrvin   mcirvin@husc.harvard.edu   Long live short .sigs
Newsgroups: sci.physics
From: vincent@reg.triumf.ca (pete)
Subject: Re: Blue Sky
News-Software: VAX/VMS VNEWS 1.41    
Organization: dept. of theophysics and cosmogyny
Distribution: na
Date: Sat, 25 Jul 1992 12:03:00 GMT

Andrew Mullhaupt writes:
> Why is the sky blue?

How about (implicitly assuming that our experience of `blue' is
common):

Blue is a very benign colour to have dominating your field of
view, as is green. So we evolved to see the sky as blue and vegetation
as green because those of our potential forebears who saw the
sky as brown and the leaves as orange got massively depressed
and died without leaving progeny.  (^:
===========================================================================
A cynic's world is comprised                          Pete Vincent
of fools and other cynics