The evolution of worlds from nebulae

Front matter

If

QB

Slielf.l!)3__

Introduction

The theory of , world-formation as conceived by the Nebular hypothesis has been briefly stated by Dr. H. W. Warren in the following words : " All the matter composing all the bodies of the sun, planets, and their satellites, once existed in an exceedingly diffused state ; rarer than any gas with which we are acquainted, filling a space larger than the orbit of Neptune. Gravitation gradually contracted this matter into a condensing globe of immense extent. Some parts would naturally be denser than others, and in the course of contraction a rotary motion, it is affirmed, would be engendered. Rotation would flatten the globe somewhat in the line of its axis.

Contracting still more, the rarer gases, aided by centrifugal force, would be left behind as a ring that would ultimately be separated, like Saturn's ring, from the retreating body. There would naturally be some places in this ring denser than others ; these would gradually absorb all the ring into a planet, and still revolve about the central mass, and still rotate on its own axis, throwing off rings from itself.

8 INTRODUCTION.

Thus the planet Neptune would be left behind in the first sun-ring, to make its one moon ; the planet Uranus left in the next sun-ring ; and so on down to Mercury. The outer planets would cool off first, become habitable, and, as the sun contracted and they radiated their own heat, become refrigerated and left behind by the retreating sun. The four great classes of facts confirmatory of this hypothesis are as follows : ist. All the planets move in the same direction and nearly in the same plane, as if thrown off from one equator ; 2d. The motions of the satellites about their primaries are mostly in the same direction as that of their primaries about the sun ; 3d. The rotation of most of these bodies on their axes, and also of the sun, is in the same direction as the motion of the planets about the sun ; 4th. The orbits of the planets, excluding asteroids, and their satellites, have but a comparatively small eccentricity ; 5th. Certain nebulae are observable which are not yet condensed into solids, but are still bright gas." *

The nebular hypothesis above stated was advanced by astronomers early in the eighteenth century, and later established by Laplace on a mathematical basis, who at the same time advocated the theory as materialistic. It is accepted quite generally by astronomers at the present day, though in a greatly modified form ; for there are many difiiculties in the way of a full belief of the theory. Sir Robert Ball in a late work says of Herschel's belief of the transmutation of nebulae into stars ; " To establish

* Warren. " Recreations in Astronomy," p. 182.

INTRODUCTION. r

this theory it would be necessary to watch the actual condensation of one single nebula from the primative gaseous condition down to the stellar points. It may easily be conceived that such a process would require a vast lapse of time, perhaps enormously greater than the period between the invention of the telescope and the present moment. It may at all events be confidently asserted that this condensation of a nebula into a star is a process which has never been witnessed." .Concerning the theory of Laplace he tells us that it is "almost incapable of receiving any direct testimony ;" and gives as the verdict of science, the words of Newcomb ; " At the present time the nebular hypothesis is only indicated by the general tendencies of the laws of nature."

According to this theory, — if all the planets are of the same substance as the earth on which we live, and of the greater sun from which they have ages since been separated, — there must once have been material heavy as rock and earth after condensation, filling the space around our sun in every direction for 3,000 millions of miles. If we could learn how this material of fire-mist originated we could better understand the mystery of world-making. A theory that would explain the formation of our own solar system should explain the formation of all the suns in space, a state of fire-mist for one implying the same for all. Let us consider whether there may not be other explanations of the phenomena in question fully as credible as the one given, and quite as consistent with all the known laws of nature.

Chapter 1. Expansion And Contraction

I St. 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.

I " I/aplace has given us proof that the period of the earth's axial rotation has not changed i-ioo of a second of time in two thousand years."

Warren. "Recreations in Astronomy," p. 145.

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 yo-.Vfo P^^^ ^'^ ^^^ diameter, would give to it heat

1 Ball. "In starry Realms," p. 31.

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 lo millions of miles, of loo, i,ooo, 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.

Chapter II. Density And Gravitation

ist. 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.

C_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." ^^

Now if this is a good explanation what shall we say of the sun from which these planets were separated ? If it grew more and more solid as it contracted until Mercury, nearly ten times denser than Saturn, was thrown off, why is not the sun denser than Mercury ? whereas we find It with but one-fourth the density of earth.

I Winchell, "Walks and talks in the Geological Field," p. 217.

When the sun reached out to earth it must have had a diameter of nearly 200 million miles, but having now contracted to a diameter of less than one million of miles, should it not have a density ten times greater than earth's, instead of one so much less ? For if the solid parts when out at Neptune began to fall toward the sun's centre, they should have continued to fall until they reached it, or until they had met a density greater than their own. We must remember even at the sun's present surface a body would fall with much greater velocity than on earth's surface because of its greater weight. With the density of our earth more than five times that of water, and twice that of solid rock, all heavy substances must gravitate toward its centre ; whereas on the surface of the sun the gravitation is more than 27 times stronger. If then the sun were ever a fire-mist reaching out to earth, it would seem that nothing should have prevented the earth from falling with lightning-like speed to the sun's centre, as its volume was 8,000,000 times larger than now, and even its present volume would hold 900 thousand worlds like ours before it would have a like density.

2d. Gravitation. We see the sun to-day as a perfect sphere, but does a body that is a sphere ever throw off rings by rotary movement ? When a body in its revolutions throws off rings by rotating, instead of being spherical it is of a flattened, or grind-stone shape, and the rings are hurled from it by the centrifugal force overpowering the gravitation ; hence we cannot think that the sun's rings, — being of enormous circumference and neces- 2 sarily of a light or fluid substance in order to be thrown off, — could form into spheres unless the centrifugal force was extremely great.

Let us suppose that Neptune was thrown off from the sun as a ring, like those we see around Saturn ; and, as it is now about 3,000 millions of miles distant from the sun's centre, before it was detached it must have had a diameter of about 6,000 millions of miles, with a circumference of over 18,000 million miles. Now, as Neptune has about 100 times the volume of earth,^ its ring could have been no more than 40 miles square ; for 1600 square miles multiplied by 18,000 million miles, the distance around that ring, will give more than Neptune's volume. How then could any substance so exceedingly thin draw to itself this enormous distance of 18,000 millions of miles, any more than a thread a thousand miles in length could draw itself together into a ball, without the thread's breaking into a million pieces ?

Or, take another theory, and instead of supposing that the sun threw off rings, suppose that its surface cooled and formed into a hard crust. Had the inner sun then shrunk away from the outer could that crust have ever formed into a globe that would rotate around the inner sphere, and if not how could Neptune have been formed ? Should such a crust have extended around the sun while spread out to Neptune it must have had a circumference of over 18,000 million miles, as did the ring, with a surface of 108

I Steele's " New Descriptive Astronomy," p. 174.

quintillions of square miles ; so the crust could not have exceeded one-sixtieth of an inch in thickness. If, then, Neptune's substance in any way resembles earth's, with a crust of that thickness upon the sun's surface, it must have collapsed in millions of places instead of having broken away from the sun and formed the globe that we now behold. Chambers tells us : "At the surface of the earth a body set free in space falls 16.1 ft. in the first second of time, with a velocity increasing during each succeeding second. A body similarly set free at the surface of the Sun would start with a velocity 27.4 times as great as that of a body falling at the surface of the Earth. This is equivalent to saying that a pound's weight of anything on the Earth would, if removed to the Sun, weigh more than 27 lbs. The centrifugal force, due to the rotation of any body diminishes gravity at its surface. At the Earth's equator the total diminution is ^-J-g- part ; whilst at the Sun's equator the centrifugal force is only about y^.o^o^ part the force of gravity. It would be necessary that the Sun should turn on its axis 133 times quicker than it does, for the force of gravity to be neutralized. In the case of the Earth, however, a speed of rotation 17 times as great as it is would suffice to produce the same result." ^

By this it is seen the centrifugal force is comparativelyinsignificant with the sun revolving faster than ever before ; for, on the principle that the more a body contracts, the swifter it revolves, it must revolve several hundredl

1 Chambers' " Hand Book of Astronomy," p. 6.

times faster now than it did when its circumference was at Neptune's bounds. If this be the case it is difficult to believe there was ever a time that the sun could have been larger than at the present, and have had centrifugal force enough to throw off rings from its surface.

Chapter III. The Cooling Of The Planets

ist. If the sun was once so much greater that it reached out to Neptune, — as it must have done if Neptune was cast off from it, — would not its poles have flattened like those of Earth, and have cooled first, and any matter thrown off from the globe have been at the poles? Yet the poles of Earth seem scarcely to change as it turns on its axis, and a body thrown off from them would not go around the planet ; but, on cooling, fall back to the liquid centre. Such being the case why has earth a density greater than the sun, and what was the power that kept, and still keeps it, from sinking into the sun ? Knowing as we do the power of gravitation, we should suppose these masses to be so held that they could not escape from the sun. Saturn, with its three glowing rings, we behold as a blazing star,*

* "Saturn has a mean diameter that is about nine times that of Earth while his volume exceeds hers more than 700 times. Within an extreme span of upwards of four millions of miles on either side of Saturn's globe there circle eight satellites and two millions of worlds, the least of which is probably as large as Mars. Then within the path of the innermost of these moons there is the wonderful ring system of Saturn. The span of this sj'^stem of rings amounts to about 176,000 miles ; that is its outermost edge lies about 88,000 miles from Saturn's centre, while the complete system has a breadth of 37.600 miles, but the innermost part, to a breadth of nearly 9,000 miles is dark- Through this dark ring the outline of Saturn's disc can be clearly perceived. In fact this wonderful dark ring is transparent. The bright parts of the system form two rings, separated from each other by a dark, but not perfectly black, circular division about 1700 miles broad."

Proctor, " EJxpanse of the Heavens," p. 96.

22 THE COOLING OF THE PLANETS.

but why has it not cooled ? The sun must have thrown off the planet millions of years ago, for it now lies about 900 millions of miles distant, and the contracting of the sun on its radius would make it 450 millions of centuries since it spread out as far as Saturn. Hence, if Earth is cold Saturn should be the same in that far-away, colder region ; and being ten times farther from the sun than the earth, it should have been formed ten times as long ago, according to the nebular hypothesis.

If Saturn yet throws off rings may not the sun do the same until cool as Saturn and reduced to a like size ? At the time the sun spread out to that planet its diameter must have been 1800 millions of miles, whereas now it is about 900,000 miles. With such a diameter shrunken to less than one million of miles we would ask why Saturn is not yet cool ? Should we extend the sun's diameter again to reach Saturn, it would have, as stated, a radius of 900 millions of miles ; giving 10,000 million times its present volume. By contracting the same at a like rate it would be 450 millions of centuries ago that Saturn was thrown off from the sun. Now, as Saturn has only ytV^ part of the sun's volume, with a density much less, and lies far out in space ; why in all these millions of years has it not cooled instead of holding heat and continuing to throw off rings? If it possesses the exceedingly light density sometimes claimed for it, ^ and has a gravitation at its sur-

I ''Its mean density is less than that of any known planet, being less than

one-seventh of the earth."

Proctor, " Expanse of the Heavens," p. 97.

THE COOLING OF THE PLANETS. 23

face but little more than that of Earth, one would suppose to find it a much colder object than the earth.

2nd. The little planets called asteroids take somewhat the form of a nebula and are distant from. the sun from two to three hundred and fifteen millions of miles. Yet these planets, numbering some three hundred, do not, if taken all together, form more than one-fourth the size of Earth, yet they must be older than either Earth or Mars, according to the above hypothesis, and should likewise be cold. For a time the explosion of some planet was thought to have formed them, but the great number since discovered, and their position and movements, give no credence to the belief that they are fragments of a shattered planet ; for Vesta as seen by the naked eye, and Ceres and Pallas, show by their orbits that to be an impossibility. They are now thought to have been thrown from the sun as a ring, and that the ring, instead of forming into one planet, has been broken up into these numberless asteroids. If this supposition be true we should expect to find them all at about the same distance from the sun. Instead we find that their distances vary millions of miles, making nearly as great a difference between them as is their distance from the sun. What, then, must that ring have been when it is claimed that the combined mass of the asteroids would not exceed over 400 miles ! Proctor tells us : " The asteroids themselves supply an argument in favor of the nebular theory rendering its probability so strong as practically to amount to certainty ; for the antecedent probability against the observed uniformity

24 THE COOLING OF THE PLANETS.

of direction of the 175 asteroids by chance, or in any conceivable way except as the result of some process of evolution is equal to that of tossing either ' head ' or ' tail ' 175 times running, or about 23,945,290,000,000,000,000,- 000,000,000,000,000,000,000,000,000,000,000 to i."^ Notwithstanding the above statement we would argue that when those asteroids were formed the sun must have reached out to them, if they were cast off from it ; whereas we see them distant from the sun only from two to three hundred million miles, while Jupiter is 480 millions of miles distant from it, so that to-day the asteroids are about as far from one as the other. How could they thus get away from the sun's gravitation when it is still a thousand times larger than Jupiter and at the time they were thrown off — or detached — must have been much more than that. It is claimed that Jupiter has still great power over these asteroids, and if so the sun should have a much greater power because of its size and proximity.

I Procter, " Poetry of Astronomy , " p. 366,

Chapter IV. Space

If all the stars that we now see in space were once fire-mist, there must have been another region equally large filled with some substance of a temperature 600° below zero, in order to equalize the heat of the fire-mist and leave space 300° below zero, as it now is in the vast region that surrounds existing stars." What must that cold of 600° have been, for what is that of 300° even when water freezes at 32° above zero and mercury at 30° below ! Where that cold space was we know not, neither do we know what was in space before the fire-mist. ^

If the nebular theory will sufficiently account for the throwing-off and cooling of the planets, will it likewise account for the millions of suns disseminated throughout space? In the first place, let us suppose that all these suns were made at the same time and filled space with the same substance as our earth, only in a diffused state. In

1 For example : Take two rooms and heat one as hot as the sun now is what must the cold in the next room be to equalize the heat to 300° below zero ?

2 "We do not inquire how the original nebula came into being ; our history must commence with the actual existence of this nebula. There is, let it be confessed, a great deal of obscurity still clinging to the subject. Though we may be sure, that the great neblua once existed we cannot with much confidence trace out the method by which the planets were actually formed.

Sir Robert Ball, " In Starry Realms," p. 348.

such a case I cannot conceive how it could break up and resolve into stars, for there being no space to turn in all would revolve together. The pulp within the rind of an orange could not be cut into circles and caused to revolve inside of that rind ; so fire-mist once filling the immensity of space must have continued to revolve in an unbroken mass. Secondly ; If the stars were formed at different periods of time should" not many be still forming ? whereas space appears wondrously clear. We would think if all this great space were to-day filled with nebulae composed of material similar to that of earth, we could not see ; for our vision of the heavens would be obstructed thereby, and we should know nothing about the counties^ numbers of stars that, with the aid of the telescope, now make the very heavens to blaze with light. Why is it that the space about all, or nearly all, of the suns has thus cleared if a state of fire-mist is common to all of them ? It is true Nebulae are seen that appear like vast fields of dim light, but they are often resolved into stars when examined with powerful instruments, and the nebulae that cannot be thus resolved into suns occupy but a small portion of the heavens. Less than one cubic foot is now left out of the 147,200 millions of cubic feet in every cubic mile of fire-mist that the sun's sphere must have contained when it reached out to the planet Neptune, and what has become of it all ? If it is not in our system it must have gone into others. Again ; if among the stars that we now see there are a million, or even a thousand times as many dark bodies as luminous ones, they must in a measure obstruct the light of the glowing suns. But were this known to be true it would not prove that these bodies were not originally formed dark objects; and who but an omnipotent and omniscient Ruler could prevent repeated collisions among them ?