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Meteorology By Aristotle

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Bathos
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« on: August 30, 2009, 11:34:46 pm »

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    http://classics.mit.edu//Aristotle/meteorology.html

Meteorology
By Aristotle


Translated by E. W. Webster

----------------------------------------------------------------------

BOOK I

Part 1

We have already discussed the first causes of nature, and all natural
motion, also the stars ordered in the motion of the heavens, and the
physical element-enumerating and specifying them and showing how they
change into one another-and becoming and perishing in general. There
remains for consideration a part of this inquiry which all our predecessors
called meteorology. It is concerned with events that are natural,
though their order is less perfect than that of the first of the elements
of bodies. They take place in the region nearest to the motion of
the stars. Such are the milky way, and comets, and the movements of
meteors. It studies also all the affections we may call common to
air and water, and the kinds and parts of the earth and the affections
of its parts. These throw light on the causes of winds and earthquakes
and all the consequences the motions of these kinds and parts involve.
Of these things some puzzle us, while others admit of explanation
in some degree. Further, the inquiry is concerned with the falling
of thunderbolts and with whirlwinds and fire-winds, and further, the
recurrent affections produced in these same bodies by concretion.
When the inquiry into these matters is concluded let us consider what
account we can give, in accordance with the method we have followed,
of animals and plants, both generally and in detail. When that has
been done we may say that the whole of our original undertaking will
have been carried out.

After this introduction let us begin by discussing our immediate subject.
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« Reply #1 on: August 30, 2009, 11:36:07 pm »

Part 2

We have already laid down that there is one physical element which
makes up the system of the bodies that move in a circle, and besides
this four bodies owing their existence to the four principles, the
motion of these latter bodies being of two kinds: either from the
centre or to the centre. These four bodies are fire, air, water, earth.
Fire occupies the highest place among them all, earth the lowest,
and two elements correspond to these in their relation to one another,
air being nearest to fire, water to earth. The whole world surrounding
the earth, then, the affections of which are our subject, is made
up of these bodies. This world necessarily has a certain continuity
with the upper motions: consequently all its power and order is derived
from them. (For the originating principle of all motion is the first
cause. Besides, that clement is eternal and its motion has no limit
in space, but is always complete; whereas all these other bodies have
separate regions which limit one another.) So we must treat fire and
earth and the elements like them as the material causes of the events
in this world (meaning by material what is subject and is affected),
but must assign causality in the sense of the originating principle
of motion to the influence of the eternally moving bodies.
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« Reply #2 on: August 30, 2009, 11:36:32 pm »

Part 3

Let us first recall our original principles and the distinctions already
drawn and then explain the 'milky way' and comets and the other phenomena
akin to these.

Fire, air, water, earth, we assert, originate from one another, and
each of them exists potentially in each, as all things do that can
be resolved into a common and ultimate substrate.

The first difficulty is raised by what is called the air. What are
we to take its nature to be in the world surrounding the earth? And
what is its position relatively to the other physical elements. (For
there is no question as to the relation of the bulk of the earth to
the size of the bodies which exist around it, since astronomical demonstrations
have by this time proved to us that it is actually far smaller than
some individual stars. As for the water, it is not observed to exist
collectively and separately, nor can it do so apart from that volume
of it which has its seat about the earth: the sea, that is, and rivers,
which we can see, and any subterranean water that may be hidden from
our observation.) The question is really about that which lies between
the earth and the nearest stars. Are we to consider it to be one kind
of body or more than one? And if more than one, how many are there
and what are the bounds of their regions?
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« Reply #3 on: August 30, 2009, 11:36:51 pm »

We have already described and characterized the first element, and
explained that the whole world of the upper motions is full of that
body.

This is an opinion we are not alone in holding: it appears to be an
old assumption and one which men have held in the past, for the word
ether has long been used to denote that element. Anaxagoras, it is
true, seems to me to think that the word means the same as fire. For
he thought that the upper regions were full of fire, and that men
referred to those regions when they spoke of ether. In the latter
point he was right, for men seem to have assumed that a body that
was eternally in motion was also divine in nature; and, as such a
body was different from any of the terrestrial elements, they determined
to call it 'ether'.

For the um opinions appear in cycles among men not once nor twice,
but infinitely often.

Now there are some who maintain that not only the bodies in motion
but that which contains them is pure fire, and the interval between
the earth and the stars air: but if they had considered what is now
satisfactorily established by mathematics, they might have given up
this puerile opinion. For it is altogether childish to suppose that
the moving bodies are all of them of a small size, because they so
to us, looking at them from the earth.
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« Reply #4 on: August 30, 2009, 11:37:05 pm »

This a matter which we have already discussed in our treatment of
the upper region, but we may return to the point now.

If the intervals were full of fire and the bodies consisted of fire
every one of the other elements would long ago have vanished.

However, they cannot simply be said to be full of air either; for
even if there were two elements to fill the space between the earth
and the heavens, the air would far exceed the quantitu required to
maintain its proper proportion to the other elements. For the bulk
of the earth (which includes the whole volume of water) is infinitesimal
in comparison with the whole world that surrounds it. Now we find
that the excess in volume is not proportionately great where water
dissolves into air or air into fire. Whereas the proportion between
any given small quantity of water and the air that is generated from
it ought to hold good between the total amount of air and the total
amount of water. Nor does it make any difference if any one denies
that the elements originate from one another, but asserts that they
are equal in power. For on this view it is certain amounts of each
that are equal in power, just as would be the case if they actually
originated from one another.

So it is clear that neither air nor fire alone fills the intermediate
space.

It remains to explain, after a preliminary discussion of difficulties,
the relation of the two elements air and fire to the position of the
first element, and the reason why the stars in the upper region impart
heat to the earth and its neighbourhood. Let us first treat of the
air, as we proposed, and then go on to these questions.
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« Reply #5 on: August 30, 2009, 11:37:19 pm »

Since water is generated from air, and air from water, why are clouds
not formed in the upper air? They ought to form there the more, the
further from the earth and the colder that region is. For it is neither
appreciably near to the heat of the stars, nor to the rays relected
from the earth. It is these that dissolve any formation by their heat
and so prevent clouds from forming near the earth. For clouds gather
at the point where the reflected rays disperse in the infinity of
space and are lost. To explain this we must suppose either that it
is not all air which water is generated, or, if it is produced from
all air alike, that what immediately surrounds the earth is not mere
air, but a sort of vapour, and that its vaporous nature is the reason
why it condenses back to water again. But if the whole of that vast
region is vapour, the amount of air and of water will be disproportionately
great. For the spaces left by the heavenly bodies must be filled by
some element. This cannot be fire, for then all the rest would have
been dried up. Consequently, what fills it must be air and the water
that surrounds the whole earth-vapour being water dissolved.
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« Reply #6 on: August 30, 2009, 11:37:40 pm »

After this exposition of the difficulties involved, let us go on to
lay down the truth, with a view at once to what follows and to what
has already been said. The upper region as far as the moon we affirm
to consist of a body distinct both from fire and from air, but varying
degree of purity and in kind, especially towards its limit on the
side of the air, and of the world surrounding the earth. Now the circular
motion of the first element and of the bodies it contains dissolves,
and inflames by its motion, whatever part of the lower world is nearest
to it, and so generates heat. From another point of view we may look
at the motion as follows. The body that lies below the circular motion
of the heavens is, in a sort, matter, and is potentially hot, cold,
dry, moist, and possessed of whatever other qualities are derived
from these. But it actually acquires or retains one of these in virtue
of motion or rest, the cause and principle of which has already been
explained. So at the centre and round it we get earth and water, the
heaviest and coldest elements, by themselves; round them and contiguous
with them, air and what we commonly call fire. It is not really fire,
for fire is an excess of heat and a sort of ebullition; but in reality,
of what we call air, the part surrounding the earth is moist and warm,
because it contains both vapour and a dry exhalation from the earth.
But the next part, above that, is warm and dry. For vapour is naturally
moist and cold, but the exhalation warm and dry; and vapour is potentially
like water, the exhalation potentially like fire. So we must take
the reason why clouds are not formed in the upper region to be this:
that it is filled not with mere air but rather with a sort of fire.
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« Reply #7 on: August 30, 2009, 11:37:47 pm »

However, it may well be that the formation of clouds in that upper
region is also prevented by the circular motion. For the air round
the earth is necessarily all of it in motion, except that which is
cut off inside the circumference which makes the earth a complete
sphere. In the case of winds it is actually observable that they originate
in marshy districts of the earth; and they do not seem to blow above
the level of the highest mountains. It is the revolution of the heaven
which carries the air with it and causes its circular motion, fire
being continuous with the upper element and air with fire. Thus its
motion is a second reason why that air is not condensed into water.

But whenever a particle of air grows heavy, the warmth in it is squeezed
out into the upper region and it sinks, and other particles in turn
are carried up together with the fiery exhalation. Thus the one region
is always full of air and the other of fire, and each of them is perpetually
in a state of change.
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« Reply #8 on: August 30, 2009, 11:38:03 pm »

So much to explain why clouds are not formed and why the air is not
condensed into water, and what account must be given of the space
between the stars and the earth, and what is the body that fills it.

As for the heat derived from the sun, the right place for a special
and scientific account of it is in the treatise about sense, since
heat is an affection of sense, but we may now explain how it can be
produced by the heavenly bodies which are not themselves hot.

We see that motion is able to dissolve and inflame the air; indeed,
moving bodies are often actually found to melt. Now the sun's motion
alone is sufficient to account for the origin of terrestrial warmth
and heat. For a motion that is to have this effect must be rapid and
near, and that of the stars is rapid but distant, while that of the
moon is near but slow, whereas the sun's motion combines both conditions
in a sufficient degree. That most heat should be generated where the
sun is present is easy to understand if we consider the analogy of
terrestrial phenomena, for here, too, it is the air that is nearest
to a thing in rapid motion which is heated most. This is just what
we should expect, as it is the nearest air that is most dissolved
by the motion of a solid body.

This then is one reason why heat reaches our world. Another is that
the fire surrounding the air is often scattered by the motion of the
heavens and driven downwards in spite of itself.
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« Reply #9 on: August 30, 2009, 11:38:15 pm »

Shooting-stars further suffix to prove that the celestial sphere is
not hot or fiery: for they do not occur in that upper region but below:
yet the more and the faster a thing moves, the more apt it is to take
fire. Besides, the sun, which most of all the stars is considered
to be hot, is really white and not fiery in colour.
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« Reply #10 on: August 30, 2009, 11:38:29 pm »

Part 4

Having determined these principles let us explain the cause of the
appearance in the sky of burning flames and of shooting-stars, and
of 'torches', and 'goats', as some people call them. All these phenomena
are one and the same thing, and are due to the same cause, the difference
between them being one of degree.

The explanation of these and many other phenomena is this. When the
sun warms the earth the evaporation which takes place is necessarily
of two kinds, not of one only as some think. One kind is rather of
the nature of vapour, the other of the nature of a windy exhalation.
That which rises from the moisture contained in the earth and on its
surface is vapour, while that rising from the earth itself, which
is dry, is like smoke. Of these the windy exhalation, being warm,
rises above the moister vapour, which is heavy and sinks below the
other. Hence the world surrounding the earth is ordered as follows.
First below the circular motion comes the warm and dry element, which
we call fire, for there is no word fully adequate to every state of
the fumid evaporation: but we must use this terminology since this
element is the most inflammable of all bodies. Below this comes air.
We must think of what we just called fire as being spread round the
terrestrial sphere on the outside like a kind of fuel, so that a little
motion often makes it burst into flame just as smoke does: for flame
is the ebullition of a dry exhalation. So whenever the circular motion
stirs this stuff up in any way, it catches fire at the point at which
it is most inflammable. The result differs according to the disposition
and quantity of the combustible material. If this is broad and long,
we often see a flame burning as in a field of stubble: if it burns
lengthwise only, we see what are called 'torches' and 'goats' and
shooting-stars. Now when the inflammable material is longer than it
is broad sometimes it seems to throw off sparks as it burns. (This
happens because matter catches fire at the sides in small portions
but continuously with the main body.) Then it is called a 'goat'.
When this does not happen it is a 'torch'. But if the whole length
of the exhalation is scattered in small parts and in many directions
and in breadth and depth alike, we get what are called shooting-stars.
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« Reply #11 on: August 30, 2009, 11:38:44 pm »

The cause of these shooting-stars is sometimes the motion which ignites
the exhalation. At other times the air is condensed by cold and squeezes
out and ejects the hot element; making their motion look more like
that of a thing thrown than like a running fire. For the question
might be raised whether the 'shooting' of a 'star' is the same thing
as when you put an exhalation below a lamp and it lights the lower
lamp from the flame above. For here too the flame passes wonderfully
quickly and looks like a thing thrown, and not as if one thing after
another caught fire. Or is a 'star' when it 'shoots' a single body
that is thrown? Apparently both cases occur: sometimes it is like
the flame from the lamp and sometimes bodies are projected by being
squeezed out (like fruit stones from one's fingers) and so are seen
to fall into the sea and on the dry land, both by night and by day
when the sky is clear. They are thrown downwards because the condensation
which propels them inclines downwards. Thunderbolts fall downwards
for the same reason: their origin is never combustion but ejection
under pressure, since naturally all heat tends upwards.

When the phenomenon is formed in the upper region it is due to the
combustion of the exhalation. When it takes place at a lower level
it is due to the ejection of the exhalation by the condensing and
cooling of the moister evaporation: for this latter as it condenses
and inclines downward contracts, and thrusts out the hot element and
causes it to be thrown downwards. The motion is upwards or downwards
or sideways according to the way in which the evaporation lies, and
its disposition in respect of breadth and depth. In most cases the
direction is sideways because two motions are involved, a compulsory
motion downwards and a natural motion upwards, and under these circumstances
an object always moves obliquely. Hence the motion of 'shooting-stars'
is generally oblique.
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« Reply #12 on: August 30, 2009, 11:38:58 pm »

So the material cause of all these phenomena is the exhalation, the
efficient cause sometimes the upper motion, sometimes the contraction
and condensation of the air. Further, all these things happen below
the moon. This is shown by their apparent speed, which is equal to
that of things thrown by us; for it is because they are close to us,
that these latter seem far to exceed in speed the stars, the sun,
and the moon.
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« Reply #13 on: August 30, 2009, 11:39:13 pm »

Part 5

Sometimes on a fine night we see a variety of appearances that form
in the sky: 'chasms' for instance and 'trenches' and blood-red colours.
These, too, have the same cause. For we have seen that the upper air
condenses into an inflammable condition and that the combustion sometimes
takes on the appearance of a burning flame, sometimes that of moving
torches and stars. So it is not surprising that this same air when
condensing should assume a variety of colours. For a weak light shining
through a dense air, and the air when it acts as a mirror, will cause
all kinds of colours to appear, but especially crimson and purple.
For these colours generally appear when fire-colour and white are
combined by superposition. Thus on a hot day, or through a smoky,
medium, the stars when they rise and set look crimson. The light will
also create colours by reflection when the mirror is such as to reflect
colour only and not shape.

These appearances do not persist long, because the condensation of
the air is transient.

'Chasms' get their appearance of depth from light breaking out of
a dark blue or black mass of air. When the process of condensation
goes further in such a case we often find 'torches' ejected. When
the 'chasm' contracts it presents the appearance of a 'trench'.

In general, white in contrast with black creates a variety of colours;
like flame, for instance, through a medium of smoke. But by day the
sun obscures them, and, with the exception of crimson, the colours
are not seen at night because they are dark.

These then must be taken to be the causes of 'shooting-stars' and
the phenomena of combustion and also of the other transient appearances
of this kind.
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« Reply #14 on: August 30, 2009, 11:39:26 pm »

Part 6

Let us go on to explain the nature of comets and the 'milky way',
after a preliminary discussion of the views of others.

Anaxagoras and Democritus declare that comets are a conjunction of
the planets approaching one another and so appearing to touch one
another.

Some of the Italians called Pythagoreans say that the comet is one
of the planets, but that it appears at great intervals of time and
only rises a little above the horizon. This is the case with Mercury
too; because it only rises a little above the horizon it often fails
to be seen and consequently appears at great intervals of time.

A view like theirs was also expressed by Hippocrates of Chios and
his pupil Aeschylus. Only they say that the tail does not belong to
the comet iself, but is occasionally assumed by it on its course in
certain situations, when our sight is reflected to the sun from the
moisture attracted by the comet. It appears at greater intervals than
the other stars because it is slowest to get clear of the sun and
has been left behind by the sun to the extent of the whole of its
circle before it reappears at the same point. It gets clear of the
sun both towards the north and towards the south. In the space between
the tropics it does not draw water to itself because that region is
dried up by the sun on its course. When it moves towards the south
it has no lack of the necessary moisture, but because the segment
of its circle which is above the horizon is small, and that below
it many times as large, it is impossible for the sun to be reflected
to our sight, either when it approaches the southern tropic, or at
the summer solstice. Hence in these regions it does not develop a
tail at all. But when it is visible in the north it assumes a tail
because the arc above the horizon is large and that below it small.
For under these circumstances there is nothing to prevent our vision
from being reflected to the sun.
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