On the Universe

De mundo (Greek: Περὶ Κόσμου), known in English as On the Universe, is the work of an unknown author who wrote under the name of Aristotle. Because of this, the author is referred to as a Pseudo-Aristotle. The date of the work is uncertain; it has been argued that it was composed before 250 BC or between 350 and 200 BC. It is found under the Bekker numbers 391–401. It should not be confused with On the Heavens.

After its original publication in Greek, the work was translated to Latin by Apuleius, into Syriac by Sergius of Reshaina and three distinct Arabic versions.

de (Neue Jahrbücher, 1905), traced most of the doctrines to Posidonius, a popular philosophic treatise based on two works of Posidonius.

Cosmology

The book De Mundo (1914 translation) begins on chapter 2, with outlining the cosmology:

The Universe then is a system made up of heaven and earth and the elements which are contained in them. But the word is also used in another sense of the ordering and arrangement of all things, preserved by and through God. Of this Universe the centre, which is immovable and fixed, is occupied by the life-bearing earth, the home and the mother of diverse creatures. The upper portion of the Universe has fixed bounds on every side, the highest part of it being called Heaven, the abode of the gods. Heaven is full of divine bodies, which we usually call stars, and moves with a continual motion in one orbit, and revolves in stately measure with all the heavenly bodies unceasingly for ever. The whole heaven and universe being spherical and moving, as I have said, continually, there must of necessity be two points which do not move, exactly opposite to one another (as in the revolving wheel of a turner's lathe), points which remain fixed and hold the sphere together and round which the whole universe moves.

The universe therefore revolves in a circle and the points are called poles. If we imagine a straight line drawn so as to join them (the axis, as it is sometimes called), it will form the diameter of the Universe, occupying the centre of the earth, with the two poles as its extremities. Of these fixed poles the one is always visible, being at the summit of the axis in the northern region of the sky, and is called the Arctic Pole*; the other is always hidden beneath the earth to the south and is called the Antarctic Pole.

In the outer portion of this occurs the substance which is made up of small particles and is fier, being kindled by the ethereal element owing to its superior size and the rapidity of its movement. In this so-called Fiery and Disordered Element flashes shoot and fires dart, and so-called 'beams' and 'pits' - and comets have their fixed position and often become extinguished.

Next beneath this spreads the air, which is in its nature murky and cold as ice. But becomes illuminated and set on fire by motion, and thus grows brighter and warm. And since the air too admits of influence and undergoes every kind of change, clouds form in it. rain-storms beat down, and snow, hoar-frost, hail with blasts of winds and of hurricanes, and thunder too and lightning and falling bolts, and the crashing together of countless opaque bodies.

Next to the aerial element the earth and sea have their fixed position, teeming with plant and animal life, and fountains and rivers, either winding over the earth or discharging their waters into the sea. The earth is diversified by countless kinds of verdure and lofty mountains and densely wooded copses and cities, which that intelligent animal man has founded, and islands set in the sea and continents.

Now the usual account divides the inhabited world into islands and continents, ignoring the fact that the whole of it forms a single land round which the sea that is called Atlantic flows. But it is probable that there are many other continents separated from ours by a sea that we must cross to reach them, some larger and others smaller than it, but all, save our own, invisible to as our islands are in relation to our seas, so is the inhabited world in relation to the Atlantic, and so are many other continents in relation to the whole sea; for they are as it were immense islands surrounded by immense seas. The general element of moisture, covering the earths surface and allowing the so-called inhabited countries to rise in patches as it were of dry land, may be said to come immediately after the aerial element.

Thus then five elements, situated in spheres in five regions, the less being in each case surrounded by the greater — namely, earth surrounded by water, water by air, air by fire, and fire by ether — make up the whole Universe.

Meteorology

The book De Mundo chapter 4, is dedicated to the study of meteorology, i.e. on clouds

Cloud is a vaporous mass, concentrated and producing water. Rain is produced from the compression of a closely condensed cloud, varying according to the pressure exerted on the cloud; when the pressure is slight it scatters gentle drops; when it is great it produces a more violent fall, and we call this a shower, being heavier than ordinary rain, and forming continuous masses of water falling over earth. Snow is produced by the breaking up of condensed clouds, the cleavage taking place before the change into water; it is the process of cleavage which causes its resemblance to foam and its intense whiteness, while the cause of its coldness is the congelation of the moisture in it before it is dispersed or rarefied. When snow is violent and falls heavily we call it a blizzard. Hail is produced when snow becomes densified and acquires impetus for a swifter fall from its close mass; the weight becomes greater and the fall more violent in proportion to the size of the broken fragments of cloud. Such then are the phenomena which occur as the result of moist exhalation.

See also

• Meteorology (Aristotle)