The Evolution of Worlds From Nebulae

CHAPTER I.. Expansion and Contraction.

EXPANSION AND CONTRACTION.

1st. Expansion. It is supposed by the nebular hypothesis that the planets were all formed from rings of condensing vapor thrown off from a contracting sun which once filled space to, and beyond, Neptune’s distance. Let us imagine them again expanded to a like dimension, or even greater, reaching half way to the next nearest sun, Alpha Centauri, whose distance from our sun is computed as about twenty trillions of miles. Assuming this to be the true distance there could be placed between the two stars fifteen septillions of suns, each with a diameter of 800 thousand miles. Were it possible to expand the earth a million and a quarter times its present size, that is as large as the sun now is, it would then be but one fifteen-septillionth the size necessary to fill the space between the sun and Alpha Centauri. What we know of earth, air, water, rocks, and the metals would not lead us to suppose that these substances could be increased by expansion even a million of times. Could there be such an expansion they would then exist as mere atomic particles of dust incapable of holding heat with the outside element space 300° below zero. Nearly all known substances expand on being heated, though not often to any great extent; as, for example, iron and the metals. But anything that is greatly expanded cools rapidly. Then may we suppose that earth to-day could be expanded into a body large enough to fill the great space it must once have occupied in the state of fire-mist claimed for it? or, if thus expanded, that it would take one year, or even one day, to cool such a body?

We have seen thus how improbable it is that the earth could be expanded to fill the space it must once have occupied according to the nebular theory; and as we imagine the denser any volume is the more it will expand can we suppose the other planets, with a volume thousands of times greater than that of earth but a density not averaging one-fourth as much, will expand to a greater degree? Were they all ground to the finest dust, even like the atoms we detect floating in the sunbeams, they would no more than fill a globe, with the sun for its centre, whose circumference reached out to Neptune.

2d. Contraction. It is thought by many that the sun obtains its heat by the contraction of its diameter, and that at the rate of two hundred and twenty feet per year, or four miles a century. Before contraction, then, both the sun and the earth must have been much larger and consequently nearer each other than they are as seen to-day. If the sun’s diameter contracts four miles during a century, to increase its size so as to carry it out to Neptune, 3,000 millions of miles distant, would take 1500 million centuries. But that the sun thus receives its heat is a supposition; for how can any one tell that it contracts each century two miles on its radius, when a second represents four hundred and fifty miles, and two miles would be but one-two hundred and fiftieth part of a second?

Should the earth be cooling by expending more heat than it receives, as some claim, it should contract from the loss of heat as well as the sun. But if earth does thus contract it must be smaller than formerly, the sun must have less hold upon it, and with a varying gravitation, must lose its delicate balance. Yet what proof have we that earth is to-day smaller than it was two thousand years ago?

Further, we find that the more a body contracts the faster it revolves. The sun now revolves in twenty-five days, but when eight million times larger and extended out as far as earth, it must have revolved very slowly; hence with a slow revolution, and at the same time having only four cubic rods of hard substance out of every thirty-three millions of cubic rods, or one cubic mile,—for earth has contracted to one eight-millionth part of the size it then was,—why did not the rocky substance settle to the sun’s centre instead of being thrown off to form earth, especially as the sun’s gravitation was so great at its surface?

Professor Ball tells us that in gaseous bodies the loss of heat involves a corresponding contraction of the volume, attended with a rise of temperature. To quote his words: “As the temperature of the mass increases the rate at which it parts with heat also increases. The contraction of the volume will proceed at an accelerated pace, and the temperature rise with increasing rapidity. Though the temperature of the gas may at first have been extremely low it will gradually rise until it becomes sufficiently high to render the gas visible by actual incandescence. As the process advances still further the body may pass from a mere nebula into a star-like object. With increase of contraction the pressure also increases and materials which were originally gaseous will assume more and more a density resembling that of solid bodies.” He says further that should the sun contract into a globe less its present size by one ten-thousandth part of its diameter it would amount to a shrinkage in its diameter of 87 miles. “But,” he continues, “on so mighty a globe this alteration is relatively insignificant; indeed no measurements that could be made at our observatories would be sufficiently delicate to detect a change of this magnitude. Helmholtz has, however, shown that if the sun were to undergo even this small diminution of volume the quantity of heat that would be thereby liberated for the purposes of radiation would supply the sun’s current rate of expenditure for nearly 2000 years. We have no means of knowing at present whether the actual contraction of the sun takes place at this rate or any other rate.”

Thus we see astronomers admit that a contraction of merely four miles of the sun’s diameter would be sufficient to supply its heat for a century, while a contraction of 87 miles, or 1/10,000 part of its diameter, would give to it heat for twenty centuries, were the sun gaseous. This being the case how is it possible to detect in this century, with a contraction of but four miles, whether the sun is growing either larger or smaller, or in any wise changing its volume?

When its diameter was twice as large as now it must have been so much cooler that it moved more slowly and radiated less heat. With a diameter of 10 millions of miles, of 100, 1,000, 3,000, or 6,000 millions of miles even, and the sun then more years than it is now days in turning, can we suppose that it revolved swiftly enough to throw off rings; or, with a surface so expanded, was possessed of heat to any great amount? These are thoughts that should be carefully considered in looking at the theory of the formation of worlds from nebulae; for any explanations concerning the existence of a fire-mist so extensive as to reach Neptune’s bounds are of no small consideration, and should be open to careful scrutiny before absolute acceptance.

FOOTNOTES:

Warren. “Recreations in Astronomy,” p. 182.

“Laplace has given us proof that the period of the earth’s axial rotation has not changed 1-100 of a second of time in two thousand years.”

Warren. “Recreations in Astronomy,” p. 145.

Ball. “In Starry Realms,” p. 31.

CHAPTER II.. Density and Gravitation.

DENSITY AND GRAVITATION.

1st. Density. The sun’s density is one-fourth that of earth, while Mercury’s is one-fifth greater than earth’s, showing that Mercury’s substance must be more than five times denser than the sun’s, whereas it is not 36,000,000 miles distant from it; so near, in fact, and so recently thrown off from the sun as to be thought that human beings could not live upon it. Why is it that this dense substance did not, while a portion of the sun, sink to its centre?

It might be said that on cooling, after being thrown from the sun, the body became more and more dense, the same as is said of earth. But if so why is it that Neptune, seventy-five times farther from the sun, has a density only one-fifth that of earth, and Uranus but a little more; while Jupiter’s density is less than the sun’s, and Saturn’s not even one-seventh that of earth? All of these planets lie in an immensely cold and far away region and were thrown off by the sun, if at all, many years before Mercury, and, according to the supposed theory, should be cold bodies.

Some think, with apparent show of reason, that before planet-making began the heavier materials of the general mass had gravitated toward the centre, while the lighter substances remained near the surface. “If so,” to quote the words of Prof. Winchell, “the first planets separated would contain more of the substances which, at temperatures familiar to us, make gases and water. Similarly, the later planets disengaged would acquire a large proportion of the substances which form solid rocks. In the case of the earth we may suppose that the greater part was rock-making material, since the earth’s specific gravity is so high; but watery stuff in sufficient amount to provide for oceans and rains, went off with the rock-material, and with these, the lighter stuff for an atmosphere. But in the case of Venus, most of the stuff was rock-material, if not the whole of it; while with Mercury it seems probable that little water-stuff was included. In the opposite direction, Saturn, Uranus, and Neptune must have received a large excess of water and atmospheric stuff. It is rational to suppose that their oceans have always covered the whole land, as ours does more than half. In fact, these bodies must be composed chiefly of water and atmosphere; as their specific gravities are low as water and cork.”

Continue reading The Evolution of Worlds From Nebulae free in the Wunder reader →