Re: OT: Trivia about clouds
- From: anon1@xxxxxxx
- Date: Mon, 16 Jan 2006 13:29:26 -0800
> >There's no such thing as a cloud.
> Sure there is. I can point to them and use the term "cloud" to convey
> to others the thing I point at.
No, you only believe you are conveying, but in fact the region of
cloudiness you imagine to be a "cloud" doesn't match any region of
cloudiness others believe you are pointing to. You need to do a
scientific experiment to test your claim of conveying: Sit with several
others until you see "a cloud" you wish to convey, then point at "the
cloud" and simultaneously click a digital camera to take a digital
photo of the sky. Then have each of the other people use an
image-processing program to draw an outline around what they think you
pointed at. You of course do the same to show what you were actually
pointing at. Then when everyone is done, you check whether everyone
agrees by having drawn essentially the same outline as you did.
> each droplet is, by your standard, a bunch of water molecules.
True, but those water molecules are connected together in a
well-defined liquid state, whereby it's possibly to rigorously define
which molecules are in the connected set and which are floating free
from it. At any moment in time, the only ambiguity is that some
molecules are at that moment in the process of joining or leaving the
connected set, with an undertainty whether the defined moment of
joining or leaving is before or after the moment.
> >although such objects aren't conserved, because two droplets can merge
> >into one,
> There is no law of conservation of objectness.
Correct. There are very few things in nature which are conserved, such
as charge, mass-energy, spin-half-parity, momentum, ... plus a few
others which are mostly conserved (require weak-force interaction to
violate the conservation, thus remain conserved for long times between
weak interactions).
> >But "clouds" are
> >nothing but apparent clusterings of such separate droplets, and there's
> >no such thing as a cloud then a boundary then another cloud.
> They have as much reality as metropolitan areas, islands, stars, etc.
Agreed about metropolitan areas. In many cases they are completely
arbitrary, more a statement of political authority than fact.
Somewhat agreed about islands. Depending on the tides, two islands
would join to form one, and a whole bunch of islands share a common
underwater shelf, whether they be formed from a single magma chamber
under the crust (as with Hawaii) or whether they be formed from growing
coral.
Mostly disagreed about stars. There's a clear boundary at the
photosphere between the opaque plasma inside and the mostly transparent
corona above. Even in cases of double stars so close that one of the
stars is spilling material past L-1 point into the other, we can make a
fairly clear division between material that hasn't yet spilled and
material that has already.
During the transition from a red supergiant to a planetary nebula,
there may be a period of time when it's not clear where to draw the
boundary between in-star and out-of-star. Do you have any other example
in mind? But there's no problem of counting one or two stars
ambiguously. There's always just one star in each star location, unlike
clouds or islands or metropolitan areas where it's difficult to agree
on a way to count distinct objects.
During formation of stars from diffuse nebula of gas and dust, also
called molecular clouds, pre-stars probably can't be counted in a
well-defined way. Also low-mass stellar objects may be counted as brown
dwarfs or giant jupiters, so it's not a matter of having trouble with
boundaries so much as just knowing whether a discrete object should
count as a "star" or as a "planet". But there is in fact a precise
definition that distinguishes brown dwarfs from smaller or larger
objects, based on what kinds of fusion ever happen during the lifetime
of the object, so technically we can exactly count how many true stars
(regular or brown) have formed after the formation process is well
enough along. So except for predicting the future prospects of
molecular clouds, it's clear how to count present and future stars.
> Countiness (to continue my colbertization of language) is not a
> necessary quality of existence.
Correct. However countiness *is* a necessary prerequisite before the
article "a" or "the" can be used to specify one specific object, or
before using the plural to indicate more than one such object. Thus my
claim of no such thing as a cloud, despite our agreement that
foggy/cloudy parts of Earth's atmosphere do exist, with the caveat that
"part" is not have the countiness property, "part" is just any
arbitrary subset you wish to specify, perhaps with a restriction that
a "part" must be connected.
> Meet my heap of sand.
Heaps of sand on a beach are pretty much meaningless. A "heap" is just
a bunch of grains of sand (rock) whereby the upper ones are supported
(against gravity) by the ones under them. But on a beach, how far down
into the beach do you extend this chain of support?? It's totally
arbitrary. In a sense, the entire beach, extending from Alaska to
Panama and beyond, is a single "heap" of sand.
Now if you pile sand in separate piles on a non-sand surface such as an
asphalt or concrete playground, then you may be able to divide the
sand into separate heaps, where you can actually count the number of
grains in each heap.
> >You want trivia questions about the "cloudiness" property of the atmosphere.
> Well done. And I don't know why I felt like pendanticizing.
You're welcome.
By the way, when the TV weatherman says there's a band of cloudiness
extending from Hawaii to the Pacific Northwest, which is going to be
bringing lots of moisture to already-too-wet Seattle, I wonder if the
word "band" has any precise meaning. Is it possible to delimit one
"band" from another and thereby count how many "bands" of cloudiness
there are worldwide at any instant, or do "bands" have a similar
problem with "clouds" and "heaps of sand" and "metropolitan areas"?
..
.
- References:
- Re: OT: Trivia about clouds
- From: anon1
- Re: OT: Trivia about clouds
- From: Matt Silberstein
- Re: OT: Trivia about clouds
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