Stellar Evolution and Its Relations to Geological Time

PART I.. _the Impact Theory of Stellar Evolution._

THE IMPACT THEORY OF STELLAR EVOLUTION.

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CONSIDERATION OF THE FACTS WHICH SUPPORT THE THEORY, AND OF THE LIGHT WHICH THE THEORY APPEARS TO CAST UPON THE FACTS 12

I. Probable Origin of Meteorites 12

II. Motion of the Stars; how of such different velocities, and always in straight lines 14

III. Motion of the Stars not due to their mutual attractions 14

IV. Probable Origin of Comets 17

V. Nebulæ 18

1. Origin of Nebulæ 18

2. How Nebulæ occupy so much space 18

3. Why Nebulæ are of such various shapes 19

4. Broken fragments in a Gaseous mass of an excessively high temperature the First stage of a Nebula 19

5. The Gaseous condition the Second stage of a Nebula 24

6. The Gaseous condition Essential to the Nebular Hypothesis 25

7. The mass must have possessed an excessive temperature 26

8. Gravitation could, under no possible condition, have generated the Amount of Heat required by the Nebular Hypothesis 27

9. Condensation the Third and last stage of a Nebula 30

10. How Nebulæ emit such feeble Light 30

VI. Binary Systems 32

VII. Sudden Outbursts of Stars 33

VIII. Star Clusters 34

IX. Age of the Sun’s Heat: a Crucial Test 34

PART II.. _evidence in Support of the Theory

EVIDENCE IN SUPPORT OF THE THEORY FROM THE AGE OF THE SUN’S HEAT.

TESTIMONY OF GEOLOGY AND BIOLOGY AS TO THE AGE OF THE SUN’S HEAT 37

Testimony of Geology: Method employed 39

The Average Rate of Denudation in the Past probably not much greater than at the Present 44

How the Method has been applied 47

Method as applied by Professor Haughton 50

Method as applied by Mr. Alfred R. Wallace 51

Method as applied directly 52

Evidence from “faults” 53

Time required to effect the foregoing amount of Denudation 62

Age of the Earth as determined by the Date of the Glacial Epoch 64

Testimony of Biology 65

PART III.. _evidence in Support of the Theory

EVIDENCE IN SUPPORT OF THE THEORY FROM THE PRE-NEBULAR CONDITION OF THE UNIVERSE.

Professor A. Winchell on the pre-nebular condition of matter 71

Mr. Charles Morris on the pre-nebular condition of matter 75

Sir William R. Grove on the pre-nebular condition of matter 78

Evolution of the Chemical Elements, and its Relations to Stellar Evolution 80

Sir Benjamin Brodie on the pre-nebular condition of matter 84

Dr. T. Sterry Hunt on the pre-nebular condition of matter 85

Professor Oliver Lodge on the pre-nebular condition of matter 87

Mr. William Crookes on the pre-nebular condition of matter 90

Professor F. W. Clarke on the pre-nebular condition of matter 98

Dr. G. Johnstone Stoney on the pre-nebular condition of matter 99

THE IMPACT THEORY IN RELATION TO THE FOREGOING THEORIES OF THE PRE-NEBULAR CONDITION OF MATTER 102

The Theories do not account for the Motion of the Stars 105

The Theories do not account for the Amount of Heat required 106

Evolution of Matter 107

Objection considered 109

Can we on Scientific grounds trace back the Evolution of the Universe to an Absolute First condition? 110

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STELLAR EVOLUTION.

PART I.. _the Impact Theory of Stellar Evolution._

THE IMPACT THEORY OF STELLAR EVOLUTION.

Upwards of twenty years ago the theory—or, I should rather say, the hypothesis—was advanced that our sun was formed from a hot gaseous nebula produced by the colliding of two dark stellar masses; and that, as the stars are suns like our own, they in all likelihood had a similar origin. The probability of this theory has been very much strengthened by the facts, both astronomical and physical, which have accumulated since the theory was enunciated. Before proceeding to the consideration of these facts, and the conclusions to which they lead, it will be necessary to give a statement of the fundamental principles of the theory.

In the theory here discussed the truth of the nebular hypothesis, which begins by assuming the existence of a solar nebulous mass, is taken for granted. The present theory deals not so much with the nebulous mass itself as with the formation of the nebula, and with those causes which led to its formation. For convenience of reference, and to prevent confusion, I have called it the “Impact Theory,” by which name it may be distinguished, on the one hand, from the nebular theory, and, on the other hand, from the meteoric theory, and all other theories which regard gravitation as the primary source of the solar energy.

The theory starts with the assumption that the greater part of the energy possessed by the universe exists or is stored up in the form of the motion of stellar masses. The amount of energy which may thus be stored up is startling to contemplate. Thus a mass equal to that of the sun, moving with a velocity of 476 miles per second, would possess, in virtue of that motion, energy sufficient, if converted into heat, to maintain the present rate of the sun’s radiation for 50,000,000 years. There is nothing extravagant in the assumption of such a velocity. A comet, for example, having an orbit extending to the path of the planet Neptune, approaching so near the sun as to almost graze his surface in passing, would have a velocity within 86 miles of what we have assumed. Twice this assumed velocity would give 200,000,000 years’ heat; four times the velocity would give 800,000,000 years’ heat; and so on.

We are at perfect liberty to begin by assuming the existence of stellar masses in motion; for we are not called upon to explain how the masses obtained their motion, any more than we have to explain how they came to have their existence. If the masses were created, they may as likely have been created in motion as at rest; and if they were eternal, they may as likely have been eternally in motion as eternally at rest.

Eternal motion is just as warrantable an assumption as eternal matter. When we reflect that space is infinite—at least in thought—and that, for aught we know to the contrary, bodies may be found moving throughout its every region, we see that the amount of energy may be perfectly illimitable.

But, illimitable as the amount of the energy may be, it could be of no direct service while it existed simply as the motion of stellar masses. The motion, to be available, must be transformed into heat: the motion of translation into molecular, or some other form of motion. This can be done in no other way than by arresting the motion of the masses. But how is such motion to be arrested? How are bodies as large as our earth, moving at the rate of hundreds of miles per second, to have their motion stopped? According to the theory this is effected by collision: by employing the motion of the one body to arrest that of the other.

Take the case of the formation of our sun according to the theory. Suppose two bodies, each one-half of the mass of the sun, moving directly towards each other with a velocity of 476 miles per second. These bodies would, in virtue of that velocity, possess 4149 × 10^{38} foot-pounds of energy, which is equal to 100,000,000,000 foot-pounds per pound of the mass; and this, converted into heat by the stoppage of their motions, would suffice to maintain, as was previously stated, the present rate of the sun’s radiation for a period of 50,000,000 years. It must be borne in mind that, while 476 miles per second is the velocity at the moment of collision, more than one-half of this would be derived from the mutual attraction of the two bodies in their approach to each other.

Coming in collision with such a velocity, the result would inevitably be that the two bodies would shatter each other to pieces. But, although their onward motions would thus be stopped, it is absolutely impossible that the whole of the energy of their motions could be at once converted into heat; and it is equally impossible that it could be annihilated. Physical considerations enable us to trace, though in a rough and general way, the results which would necessarily follow. The broken fragments, now forming one confused mass, would rebound against one another, breaking up into smaller fragments, and flying off in all directions. As these fragments receded from the centre of dispersion they would strike against each other, and, by their mutual impact, become shivered into still smaller fragments, which would in turn be broken up into fragments yet smaller, and so on as they proceeded outwards. This is, however, only one part of the process, and a part which would certainly take place, though no heat were generated by the collisions.

A far more effective means of dispersing the fragments and shattering them to pieces would be the expansive force of the enormous amount of incandescent gas almost instantaneously generated by the heat of collision. The general breaking up of the two masses and the stoppage of their motions would be the work of only a few minutes, or a few hours at most. The heat evolved by the arrested motion would, in the first instance, be mainly concentrated on the surface layers of the broken blocks. The layers would be at once transformed into the gaseous condition, thus enveloping the blocks and filling the interspaces. It is difficult to determine what the temperature and expansive force of this gas would at the moment be, but evidently it would be excessive; for, were the whole of the heat of the arrested motion distributed over the mass, it would, as has been stated, amount to 100,000,000,000 foot-pounds per pound of the mass—an amount sufficient to raise 264,000 tons of iron 1° C. Thus, if we assume the specific heat of the gas to be equal to that of air (viz. ·2374), it would have a temperature of about 300,000,000° C. or more than 140,000 times that of the voltaic arc.

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