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Griechenland: Umweltphysik

In his book Metereology, Aristotle described the Northern Lights as a light which resembled the flames of burning gas. If these flames spread and at the same time sent out sparks and rays, they were called jumping goats. Without such rays, they were called simply fire. It is not clear how Aristotle did know about the Northern Lights. But we know that the Arctic and Antarctic were named by Aristotle. The landmass to the north "lay under the constellation of Arktos, the bear; so must the southern lands be under the opposite: Antarktikos," he wrote. Optimists of the 16th Century supposed that the Antarctic would be an idyllic place. At the Ends Of the Earth Kieran Mulvaney, A History of The Polar Regions

Red Aurora seen in Athens Greece, November 2003. © Anthony Ayiomamitis

Climatic Zones according to Aristotle

An explanation for other atmospheric phenomena was given more than two centuries earlier by Xenophanes of Colophon who

“says…the clouds are formed by the sun's vapor [i.e. vapor caused by the heat from the sun's rays] raising and lifting them to the surrounding air”
Diogenes Laertius (A1.24-5).

“...(says that) things in the heavens occur through the heat of the sun as the initial cause; for when the moisture is drawn up from the sea, the sweet portion, separating because of its fineness and turning into mists, combines into clouds, trickled down in drops of rain due to compression, and vaporizes the winds.”
Aëtius (A46)

“The sea is the source of water and of wind,
For without the great sea, there would be no wind
Nor streams of rivers, nor rainwater from on high
But the great sea is the begetter of clouds, winds, and rivers.”
Xenophanes B30

“Flashes of lightning come about through the shining of the clouds because of the movement” (A45).

His comments about the “Iris” or rainbow:

And she whom they call Iris, this too is by nature a cloud. Purple, red, and greenish-yellow to behold.”
Xenophanes B32

Θαύμας δ᾽ Ὠκεανοῖο βαθυρρείταο θύγατρα ἠγάγετ᾽ Ἠλέκτρην· ἣ δ᾽ ὠκεῖαν τέκεν Ἶριν ἠυκόμους θ᾽ Ἁρπυίας Ἀελλώ τ᾽ Ὠκυπέτην τε, αἵ ῥ᾽ ἀνέμων πνοιῇσι καὶ οἰωνοῖς ἕμ᾽ ἕπονται ὠκείῃς πτερύγεσσι· μεταχρόνιαι γὰρ ἴαλλον. Hesiod Theogony

Iris the daughter of Thaumas and the rainbow. Considered to be a messenger of Zeus. Later she was replaced by Hermes, probably because Zeus trusted him more.

Xenophanes comments shows the character of the Ionian ‘intellectual revolution’, the transition from “mythos” to “logos”. A decision to put aside an older way of thinking about events grounded in a belief in divine beings in favor of an approach to understanding the world that employs wide-ranging inquiry and direct observation and resorts to strictly physical causes and forces. Atmospheric phenomena (halos, coronae, etc) commonly have been considered signs of the intentions of the gods such as Iris, the daughter of Thaumas (“marvel”).

The physical theory of Xenophanes appears to have had little impact to other scientists such as Plato and Aristotle.

P.S. The rainbow plays also some role in the Bible in the history of Noah and the flood. The rainbow appears after the flood as a sign that God will not kill again all humans or parts of them as in the case of Onan, the cities Sodom and Gomorrha or with the flood that left only Noah, his family, and a representative set of animals alive. We have to consider that the rainbow was never “produced” before the flood. As an exercise for physicists: Try to find how the laws of Physics were before the flood.

In the sixth century BC, the Greek philosopher Pythagoras recognised the sphericity of the Earth and the dominance of latitude in explaining climate variation (Sanderson 1999). Two centuries later Aristotle expanded on Pythagoras's foundation and introduced five climate zones, ranging from tropical to northern frigid. It is not coincidental that in the early 20th century German scientist Koeppen also used 5 climate zones in his classification, identified with the letters A-E.

From Epicurus we have the following comments in one of his letters:

Clouds may form and gather either because the air is condensed under the pressure of winds, or because atoms which hold together and are suitable to produce this result become mutually entangled, or because currents collect from tile earth and the waters ; and there are several other ways in which it is not impossible for the aggregations of such bodies into clouds to be brought about. And that being so, rain may be produced from them sometimes by their compression, sometimes by their transformation; or again may be caused by exhalations of moisture rising from suitable places through the air, while a more violent inundation is due to certain accumulations suitable for such discharge. Thunder may be due to the rolling of wind in the hollow parts of the clouds, as it is sometimes imprisoned in vessels which we use; or to the roaring of fire in them when blown by a wind, or to the rending and disruption of clouds, or to the friction and splitting up of clouds when they have become as firm as ice.

As in the whole survey, so in this particular point, the facts invite us to give a plurality of explanations. Lightning too happens in a variety of ways. For when the clouds rub against each other and collide, that collocation of atoms which is the cause of fire generates lightning; or it may be due to the flashing forth from the clouds, by reason of winds, of particles capable of producing this brightness; or else it is squeezed out of the clouds when they have been condensed either by their own action or by that of the winds; or again, the light diffused from the stars may be enclosed in the clouds, then driven about by their motion and by that of the winds, and finally make its escape from the clouds; or light of the finest texture may be filtered through the clouds (whereby the clouds may be set on fire and thunder produced), and the motion of this light may make lightning; or it may arise from the combustion of wind brought about by the violence of its motion and the intensity of its compression; or, when the clouds are rent asunder by winds, and the atoms which generate fire are expelled, these likewise cause lightning to appear.

And it may easily be seen that its occurrence is possible in many other ways, so long as we hold fast to facts and take a general view of what is analogous to them. Lightning precedes thunder, when the clouds are constituted as mentioned above and the configuration which produces lightning is expelled at the moment when the wind falls upon the cloud, and the wind being rolled up afterwards produces the roar of thunder; or, if both are simultaneous, the lightning moves with a greater velocity towards its and the thunder lags behind, exactly as when persons who are striking blows are observed from a distance. A thunderbolt is caused when winds are repeatedly collected, imprisoned, and violently ignited; or when a part is torn asunder and is more violently expelled downwards, the rending being due to the fact that the compression of the clouds has made the neighboring parts more dense; or again it may be due like thunder merely to the expulsion of the imprisoned fire, when this has accumulated and been more violently inflated with wind and has torn the cloud, being unable to withdraw to the adjacent parts because it is continually more and more closely compressed [generally by some high mountain where thunderbolts mostly fall]. And there are several other ways in which thunderbolts may possibly be produced. Exclusion of myth is the sole condition necessary; and it will be excluded, if one properly attends to the facts and hence draws inferences to interpret what is obscure.

Fiery whirlwinds are due to the descent of a cloud forced downwards like a pillar by the wind in full force and carried by a gale round and round, while at the same time the outside wind gives the cloud a lateral thrust; or it may be due to a change of the wind which veers to all points of the compass as a current of air from above helps to force it to move; or it may be that a strong eddy of winds has been started and is unable to burst through laterally because the air around is closely condensed. And when they descend upon land, they cause what are called tornadoes, in accordance with the various ways in which they are produced through the force of the wind; and when let down upon the sea, they cause waterspouts.

Winds arise from time to time when foreign matter continually and gradually finds its way into the air; also through the gathering of great store of water. The rest of the winds arise when a few of them fall into the many hollows and they are thus divided and multiplied.

Hail is caused by the firmer congelation and complete transformation, and subsequent distribution into drops, of certain particles resembling wind : also by the slighter congelation of certain particles of moisture and the vicinity of certain particles of wind which at one and the same time forces them together and makes them burst, so that they become frozen in parts and in the whole mass. The round shape of hailstones is not impossibly due to the extremities on all sides being melted and to the fact that, as explained, particles either of moisture or of wind surround them evenly on all sides and in every quarter, when they freeze.

Snow may be formed when a fine rain issues from the clouds because the pores are symmetrical and because of the continuous and violent pressure of the winds upon clouds which are suitable; and then this rain has been frozen on its way because of some violent change to coldness in the regions below the clouds. Or again, by congelation in clouds which have uniform density a fall of snow might occur through the clouds which contain moisture being densely packed in close proximity to each other; and these clouds produce a sort of compression and cause hail, and this happens mostly in spring. And when frozen clouds rub against each other., this accumulation of snow might be thrown off. And there are other ways in which snow might be formed.

Dew is formed when such particles as are capable of producing this sort of moisture meet each other from the air: again by their rising from moist and damp places, the sort of place where dew is chiefly formed, and their subsequent coalescence, so as to create moisture and fall downwards, just as in several cases something similar is observed to take place under our eyes. And the formation of hoar-frost is not different from that of dew, certain particles of such a nature becoming in some such way congealed owing to a certain condition of cold air.

Ice is formed by the expulsion from the water of the circular, and the compression of the scalene and acute-angled atoms contained in it; further by the accretion of such atoms from without, which being driven together cause the water to solidify after the expulsion of a certain number of round atoms.

The rainbow arises when the sun shines upon humid air; or again by a certain peculiar blending of light with air, which will cause either all the distinctive qualities of these colors or else some of them belonging to a single kind, and from the reflection of this light the air all around will be colored as we see it to be, as the sun shines upon its parts. The circular shape which it assumes is due to the fact that the distance of every point is perceived by our sight to be equal; or it may be because, the atoms in the air or in the clouds and deriving from the sun having been thus united, the aggregate of them presents a sort of roundness.

A halo round the moon arises because the air on all sides extends to the moon; or because it equably raises upwards the currents from the moon so high as to impress a circle upon the cloudy mass and not to separate it altogether; or because it raises the air which immediately surrounds the moon symmetrically from all sides up to a circumference round her and there forms a thick ring. And this happens at certain parts either because a current has forced its wry in from without or because the heat has gained possession of certain passages in order to effect this.

Epicurus of Samos, Letter to Pythocles.

Demetris Koutsoyiannis, in his lectures of “Water resources technologies in the ancient Greece”, School of Civil Engineering National Technical University of Athens provides the following information:

The Pythagorean philosopher Hippon (5th century BC) recognizes that all waters originate from the sea.

Anaxagoras, who lived in Athens (500-428 BC) and together with Empedocles, is recognized as the father of experimental research, clarified the concept of hydrological cycle: the sun raises water from the sea into the atmosphere, from where it falls as rain; then it is collected underground and feeds the flow of rivers. He also studied several meteorological phenomena, generally supporting and completing Anaximenes’s theories; his theory about thunders, which fought the belief that they are thrown by Zeus, probably cost him imprisonment (430 BC). In particular, he correctly assumed that winds are caused from differences in the air density: the air, heated by the sun, moves towards the north pole and leaves gaps that cause air currents. He also studied Nile’s floods attributing them to the snow melt in Ethiopia. The “enigma” of Nile’s floods (which, contrary to the regime of Mediterranean rivers, occur in summer) was also thoroughly studied by Herodotus (480-430 BC), who seems to have clear knowledge of hydrological cycle and its mechanisms.

Aristotle (384-323 BC) in his treatise Mereorologica clearly states the principles of hydrological cycle, clarifying that water evaporates by the action of sun and forms vapor, whose condensation forms clouds; also, he recognizes indirectly the principle of mass conservation within hydrological cycle.

Theophrastus (372-287 BC) adopts and completes the theories of Anaximenes and Aristotle for the forming of precipitation from vapor condensation and freezing; his contribution to the understanding of the relation between wind and evaporation was significant.

Epicurus (341-270 BC) contributed to physical explanations of meteorological phenomena, contravening the superstitions of his era.

Archimedes (287-212 BC), among other significant contributions, founded hydrostatics introducing the principle named after him.

Hero of Alexandria (after 150 BC) is recognized (U.S. Committee on Opportunities in the Hydrological Sciences, 1992) as the first who formulated the discharge concept and made flow measurements.

References

U.S. Committee on Opportunities in the Hydrological Sciences (1991) Opportunities in the Hydrologic Sciences. National Academy Press, Washington, DC.

Sanderson, M., 1999. The classification of climates from Pythagoras to Koeppen. Bull. Amer. Meteor. Soc., 80, 669-673

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