The Astronomy of Milton's 'Paradise Lost' by Thomas Nathaniel Orchard (read along books .TXT) 📖
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Milton alludes to this theory in the following lines:—
Their starry dance in numbers that compute
Days, months, and years, towards his all-cheering lamp
Turn swift their various motions, or are turned
By his magnetic beam.—iii. 579-83.
An important advance upon this theory was made by Horrox, who, in his study of celestial dynamics, attributed the curvilineal motion of the planets to the influence of two forces, one projective, the other attractive. He illustrated this by observing the path described by a stone when thrown obliquely into the air. He perceived that its motion was governed by the impulse imparted to it by the hand, and also by the attractive force of the Earth. Under these two influences, the stone describes a graceful curve, and in its descent falls at the same angle at which it rose. Hence arises the general law: ‘When two spheres are mutually attracted, and if not prevented by foreign influences, their straight paths are deflected into curves concave to each other, and corresponding with one of the sections of a cone, according to the velocity of the revolving body. If the velocity with which the revolving body is impelled be equal to what it would acquire by falling through half the radius of a circle described from the centre of deflection, its orbit will be circular; but if it be less than that quantity, its path becomes elliptical.’
Newton afterwards embraced this law in his great principle of gravitation, and demonstrated that the force which guides and retains the Earth and planets in their orbits resides in the Sun. By the orb’s attractive influence a planet, after having received its first impulse, is deflected from its original straight path, and bent towards that luminary, and by the combined action of the projective and attractive forces is made to describe an orbit which, if elliptical, has one of its foci occupied by the Sun. So evenly balanced are those two forces, that one is unable to gain any permanent ascendency over the other, and consequently the planet traverses its orbit with unerring regularity, and, if undisturbed by external influences, will continue in its path for all time.
Milton describes the position of the planets in the sky as—
and their motions—
It is evident that Milton was familiar with the apparently irregular paths pursued by the planets when observed from the Earth. He knew of their stationary points, and also the backward loopings traced out by them on the surface of the sphere.
If observed from the Sun, all the planets would be seen to follow their true paths round that body; their motion would invariably lie in the same direction, and any variation in their speed as they approached perihelion or aphelion would be real. But the planets, when observed from the Earth, which is itself in motion, appear to move irregularly. Sometimes they remain stationary for a brief period, and, instead of progressing onward, affect a retrograde movement. This irregularity of motion is only apparent, and can be explained as a result of the combined motions of the Earth and planets, which are travelling together round the Sun with different velocities, and in orbits of unequal magnitude.
In his allusion to the Copernican system the ‘planet’ ‘Earth’ is described by Milton as seventh. This is not strictly accurate, as only five planets were known—viz. Mercury, Venus, Mars, Jupiter, and Saturn; but to make up the number Milton has included the Moon, which may be regarded as the Earth’s planet.
The three motions ascribed to the Earth are—(1) The diurnal rotation on her axis; (2) her annual revolution round the Sun; (3) Precession of the Equinoxes.
The rotation of the Earth on her axis may be likened to the spinning motion of a top, and is the cause of the alternation of day and night. This rotatory motion is sustained with such exact precision that, during the past 2,000 years, it has been impossible to detect the minutest difference in the time in which the Earth accomplishes a revolution on her axis, and therefore the length of the sidereal day, which is 3 minutes 56 seconds shorter than the mean solar day, is invariable. In this motion of the Earth we have a time-measuring unit which may be regarded as absolutely correct.
The Earth completes a revolution of her orbit in 365¼ days. In this period of time she accomplishes a journey of 580 millions of miles, travelling at the average rate of 66,000 miles an hour. The change of the seasons, and the lengthening and shortening of the day, are natural phenomena, which occur as a consequence of the Earth’s annual revolution round the Sun. Precession is a retrograde or westerly motion of the equinoctial points, caused by the attraction of the Sun, Moon, and planets on the spheroidal figure of the Earth. By this movement the poles of the Earth are made to describe a circular path in that part of the heavens to which they point; so that, after the lapse of many years, the star which is known as the Pole Star will not occupy the position indicated by its name, but will be situated at a considerable distance from the pole. These motions, Milton says, unless attributed to the Earth, must be ascribed to several spheres crossing and thwarting each other obliquely; but the Earth, by rotating from west to east, will of herself fetch day, her other half, averted from the Sun’s rays, being enveloped in night. Thus saving the Sun his labour, and the ‘primum mobile,’ ‘that swift nocturnal and diurnal rhomb,’ which carried all the lower spheres along with it, and brought about the change of day and night.
Milton’s allusion to the occurrence of natural phenomena in the Moon similar to those which happen on the Earth is in keeping with the opinions entertained regarding our satellite, Galileo having imagined that he discovered with his telescope continents and seas on the lunar surface, which led to the belief that the Moon was the abode of intelligent life.
With their attendant moons, thou wilt descry
Communicating male and female light.—viii. 148-50.
Milton in these lines refers to Jupiter and Saturn, and their satellites, which had been recently discovered; those of the former by Galileo, and four of those of the latter by Cassini. The existence of male and female light was an idea entertained by the ancients, and which is mentioned by Pliny. The Sun was regarded as a masculine star, and the Moon as feminine; the light emanating from each being similarly distinguished, and possessing different properties.
Milton supposes that, as the Earth receives light from the stars, she returns light back to them. But in his time little was known about the stars, nor was it ascertained how distant they are.
The Angel, in bringing to a conclusion his conversation with Adam, deems it unadvisable to vouchsafe him a decisive reply to his inquiry regarding the motions of celestial bodies, and in the following lines gives a beautifully poetical summary of this elevated and philosophic discussion:—
Whether the Sun, predominant in Heaven,
Rise on the Earth, or Earth rise on the Sun;
He from the east his flaming round begin,
Or she from west her silent course advance
With inoffensive pace that spinning sleeps
On her soft axle, whilst she paces even,
And bears thee soft with the smooth air along—
Solicit not thy thoughts with matters hid.—viii. 159-67.
In this scientific discourse between Adam and Raphael, in which they discuss the structural arrangement of the heavens and the motions of celestial bodies, we are afforded an opportunity of learning what exact and comprehensive knowledge Milton possessed of both the Ptolemaic and Copernican theories. The concise and accurate manner in which he describes the doctrines belonging to each system indicates that he must have devoted considerable time and attention to making himself master of the details associated with both theories, which in his time were the cause of much controversy and discussion among philosophers and men of science.
The Ptolemaic system, with its crystalline spheres revolving round the Earth, the addition to those of cycles and epicycles, and the heaping of them upon each other, in order to account for phenomena associated with the motions of celestial bodies, are concisely and accurately described.
The unreasonableness of this theory, when compared with the Copernican, is clearly delineated by Milton where Adam is made to express his views with regard to motion in the heavens. His argument, declared in logical and persuasive language, demonstrates how contrary to reason it would be to imagine that the entire heavens should revolve round the Earth to bring about a result which could be more easily attained by imparting motion to the Earth herself. The inconceivable velocity with which it would be necessary for the celestial orbs to travel in order to accomplish their daily revolution is described by him as opposed to all reason, and entailing upon them a journey which it would be impossible for material bodies to perform. None the less accurate is Milton’s description of the Copernican system. He describes the Sun as occupying that position in the system which his magnitude and supreme importance claim as his sole right, having the planets with their satellites,
circling in majestic orbits around him, acknowledging his controlling power, and bending to his firm but gentle sway. Their positions, their paths, and their motions, real and apparent, are described in flowing and harmonious verse.
CHAPTER IV MILTON AND GALILEOAfter the death of his mother, which occurred in 1637, Milton expressed a desire to visit the Continent, where there were many places of interest which he often longed to see. Having obtained the consent of his kind and indulgent father, he set out on his travels in April 1638, accompanied by a single man-servant, and arrived in Paris, where he only stayed a few days. During his residence in the French capital he was introduced by Lord Scudamore, the English Ambassador at the Court of Versailles, to Hugo Grotius, one of the most distinguished scholars and philosophic thinkers of his age. From Paris Milton journeyed to Nice, where he first beheld the beauty of Italian scenery and the classic shores of the Mediterranean Sea. From Nice he sailed to Genoa and Leghorn, and after a short stay at those places continued his journey to Florence, one of the most interesting and picturesque of Italian cities. Situated in the Valley of the Arno, and encircled by sloping hills covered with luxuriant vegetation, the sides of which were studded with residences half-hidden among the foliage of gardens and vineyards, Florence, besides being famed for its natural beauty, was at that time the centre of Italian culture and learning, and the abode of men eminent in literature and science. Here Milton remained for a period of two months, and enjoyed the friendship and hospitality of its most noted citizens, many of whom delighted to honour their English visitor. He was warmly welcomed by the members of the various literary academies, who admired his compositions and conversation; the flattering encomiums bestowed upon him by those learned societies having been amply repaid by Milton in choice and elegant Latin verse.
Among those who resided in the vicinity of Florence was the illustrious Galileo, who in his sorrow-stricken old age was held a prisoner of the Inquisition for having upheld and taught scientific doctrines which were declared to be heretical. After his abjuration he was
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