THE SUN is 866,000 miles in diameter, and its mass is 332,000 times as great as Earth. But it is not to be regarded as a mass of inert matter; it is a functioning, delicately adjusted atomic generator, a machine of infinite complexity, titanic size, yet controlling and regulating the vast efflux of energy it pours out with a delicacy and precision utterly astounding in a any machine.
To call the Sun a machine is not metaphor, or allegory; it is a machine in the truest sense. A machine might be defined as a mechanism which integrates a series of natural laws into a sequence of reactions that produces a certain end. The atomic generator which supplies Earth with light and heat, by using a series of very involved physical laws, succeeds first in transmuting matter mass to pure energy, then processing the crude energy released through a long series of reactions to a usable type of radiation; light.
To a certain extent, we know sufficient to draw up specifications on that atomic generator. Its rough dimensions have been given, mass and outside diameter. Its average density is about 1.41 times that of water. Incidental to the vast bulk of that generator is that mass; something of its specifications as a power plant can be given, too.
As a power plant, it is a completely self-contained unit, sealed in with sufficient fuel to last the life of the unit. The mechanism is completely self-maintaining, operating without care, repair or regulation for not less than 30,000,000,000 years. The fuel is automatically fed, and will not require renewing; so carefully and perfectly designed are the multitude of controls placed upon it that despite the fact that fuel is more stupendously explosive than anything known to man, no accident need be feared. Hundreds of thousands of millions of these units in varying sizes and types are in operation, and there is some doubt that any explosions have been observed.
This unit transmutes the mass of matter directly to energy mass. The Einstein formula E-Mc2 gives the figures on that conversion. One gram of matter mass may be transmuted to one gram of energy mass; this latter being equivalent to 9 x 1020 ergs. In more comprehensible terms; a first-rate transpacific liner contains about 1400 tons of steel. One gram of energy would be sufficient to reduce that metal to incandescent, gently bubbling liquid. The atomic-generator unit under discussion converts matter to energy at the rate of 4,000,000,000,000 grams of matter per second, each gram of which is quite capable of the above destruction.
Each second, 4,000,000,000,000 grams of matter are destroyed and radiate away as radiant energy. But the unit is packed with sufficient fuel to last out its life. At that enormous rate of radiation, 4,000,000,000 tons a second, 240,000,000 a minute, at the end of 150,000,000,000 radiation will have carried away all but about 99 per cent of the Sun. Precise instruments could, perhaps, tell the difference.
GASOLINE is not explosive; it won't react unless oxygen is present. Therefore, there is no danger in a full tank of gasoline. But substances such as nitroglycerin[ed. sic] are explosive. Nitroglycerin contains, in itself, all the oxygen and other elements needed for a violent and instantaneous reaction. But it would take just about that 14,000 tons of nitroglycerin to equal in explosive potentialities one gram of atomic fuel. And the Sun is stored with sufficient atomic fuel to last a minimum of 30,000,000,000 years at 4,000,000,000,000 grams a second.
This is in connection with novas. A nova is not a true explosion of a star; it merely represents a slight blow-off, the safety valve pops for a moment, a mere instant of stellar time. The design of that atomic-generator unit of ours is far too perfect to allow an explosion; there is a second line of defenses that keeps it under control. If the safety valve does release for a moment, the powerful controlling forces promptly bring the atomic release back under its sway.
For truly, a nova is an overrated thing. Typically, an ordinary nova flares up swiftly and enormously for not more than a few weeks, then promptly the controls reassert themselves, and the exnova returns to its original delicately balanced rate of generation.
But even that safety-valve blow-off isn't so terrifically violent; it can't be called a genuine explosion, not when the utterly indescribable potentialities for explosion present are taken into consideration. If a star really exploded, released all the stored energy designed to last its Gargantuan furnaces for meaninglessly great periods of time, in a single, brief flare, it would be a shock of energy so vast as to wipe out whole sections of a galaxy. The ordinary nova, at its maximum, releases energy no more swiftly than do certain of the greater stars at their perfectly normal output. Rigel, for instance, is one of the brighter stars of the galaxy, and about equals the average.
No, an ordinary nova cannot be called a true explosion. * The control of that atomic generator is too sound. The exact mechanism of that control? We do not know, nor do we know even approximately the mechanism of the generation (if we did, it might well be that there would be certain lesser generators here on Earth). Certain rough outlines of it we can understand, the method of ignition perhaps, and a possible answer to the control question.
Apparently no body more than about 30,000 times as massive as the Earth can exist without becoming self-luminous. The immense pressures exerted on the atoms at its core by the thousands of miles of overlying material stress atoms beyond their ability to resist through structural, static strength; only by adding to this static strength the kinetic resistance of immensely high temperatures can the pressures be supported.
THOSE TEMPERATURES in the Sun at its core run to immense intensity. Whatever the figure may be, all authorities agree on one thing; it is measured in millions of degrees. Eddington proposes a temperature of about 10,000,000° C., while Milne believes it to be many times higher. (Jeans suggests 32,000,000° as a working basis; other astrophysicists vary their estimates from Eddington's conservative figure up to 500,000,000° C.) At such temperatures bodies do not radiate heat; they give off X rays and they give them off with an intensity and fervor that is quite incomprehensible to ordinary life. Even at 1,000,000° the radiation would be X-ray energy, albeit somewhat soft rays, but the intensity is -- beyond conception.
The Sun is, really, too immense to be pictured as a whole. However, the distance from even Earth to Moon is an interplanetary distance, too great for humans to negotiate to-day. The distance from Earth to Venus is a vaster gulf of interplanetary space. Yet Earth, as the Sun's center, would find the Moon in its orbit still 200,000 miles beneath the Sun's surface. The distance from Earth to Venus is only a bit more than twoscore times the Sun's diameter. The sun, in other words, is practically of interplanetary size itself; beings theoretically imagined as capable of living on it would find themselves faced with interplanetary distances of millions of miles in visiting "neighboring" cities. And that interplanetary-sized surface is about twice as hot as a tungsten lamp filament, even at its cold outer surface.
This to illustrate the meaning of a million degrees centigrade. For a body 28 miles in diameter, equal to one of the lesser asteroids, astronomically microscopic, would outshine the Sun, give off more energy than all that colossal thing, if its surface temperature were only 1,000,000 degrees. At 10,000,000 equal to the most conservative estimates of the Sun's interior temperature, a body with a diameter of 2000 feet would radiate as much energy as all the vast 866,000-mile Sun. The radiation jetting out from such a surface would be more solid than any material we know. An imaginary (and physically impossible) opaque surface exposed to the full brunt of that solid radiation would be subjected to a radiation pressure of 140,000 tons per square inch. (Steel of the best kind resists almost 250 tons per square inch).
Stated in terms of the Sun's interior, the terrific pressures there are borne by ions (atoms stripped of their electrons), by the electrons from those atom cores, and by driving, mad quanta of radiation seeking escape into space. This radiation alone would sustain an immense pressure, and any increase in the temperature there would increase its driving force.
Have you seen a Kipp gas generator? Essentially it consists of 2 flasks: a lower one filled with, say, marble chips that will release carbon dioxide on contact with acid; and an upper flask filled with dilute acid. A rubber tube connected with the lower flask leads that gas away. The 2 flasks fit hermetically; the only escape for the gas is through the tube, or by forcing the liquid back up the tube into the upper flask. If gas is drawn off through the tube, the pressure in the lower flask falls; acid runs down from above, releases gas, and the gas so generated creates pressure to force the acid back up. Fresh acid can enter at only such a rate as to balance the withdrawal.
AS THE SUN throws out energy, it tends to cool, but cooling would mean less radiation pressure, less heat movement of ions and electrons to hold up those outer, pressing layers. They squeeze inward, perhaps feeding fresh fuel to that atomic reaction -- and a new violence forces them outward again. Long since, a balance has been reached, a steady state where fuel leaks inward slowly to that internal destruction, its entry neatly and exactly balancing the outpouring radiation.
What that fuel is, we do not know. There is a present, widely considered theory that it may be hydrogen atoms, the energy release resulting from the "packing" of hydrogen atoms to make more and more complex atoms, first 4 hydrogens being forced together to make 1 helium, then more and more atoms packing in to produce heavy atoms such as iron. That could account for it, but present knowledge is far too limited to say it does. It may be such a process as that, or it may be that total annihilation of atoms takes place, utterly destroying all trace of the atom involved to leave only pure radiant energy. This theory has met difficulties in the last few years. Originally, it seemed that the combination of a positive proton and a negative electron might lead to such a destruction and release of radiant energy. Now, we know it does not; it leads to the production of a neutron instead.
The difference is, however, fundamental and important in cosmology. If atoms are annihilated, then, presumably, a large portion of the Sun's mass might ultimately be consumed in that reaction. If instead, the hydrogen reaction is the power source, then only the small proportion of the mass represented by the so-called "packing fraction" of hydrogen is available, a quantity probably of the order of one one-hundredth of the energy available on the other scheme. That difference means an immense foreshortening of the Sun's total life.
In one respect the 2 energy releases are identical: they would release energy in the Sun's heart as a crude, savage type of radiant energy of unbearable concentration. Such energy released to space would destroy any exposed living matter instantly; life on Earth would be starkly impossible.
But our atomic generator ages and refines that crude energy into a more usable form.
The exact type of energy released at the Sun's heart depends on the type of annihilation taking place; but whatever it may be, it represents quanta of immensely penetrant and energetic type, more deadly than X rays certainly. This radiation, released 430,000 miles beneath the Sun's surface, savagely seeks a way of escape. Driving outward at 186,000 miles a second, it is nevertheless stopped almost instantly by absorption in one of the savagely battered atomic nuclei packed to enormous density there at the Sun's heart. For a moment of time -- perhaps a hundred-millionth of a second -- it is held trapped, before the nucleus discharges it again. But probably its release (which may be in any direction) is not in the original outward direction; it may be forced to retrace its course. In any case, it is reabsorbed, reradiated, time after time, each absorption and release occupying that brief fragment of a second.
What infinities of absorption and radiation it undergoes in its near half-million-mile journey to the far surface, no one can guess. But each absorption takes its minute fraction of a second, and in the countless repetitions of that process, ages pass countless centuries, myriad of milleniums. Probably that aging and refining process that each quantum of energy must undergo takes in all millions and tens of million of years, all that vast aging being made up in units of hundred-millionths of a second.
THE OUTPUT terminal of that atomic generator has an area of something like 3,000,000,000,000 square miles, the Sun's surface. It's "potential" is its temperature; about 6000° C. It is impossible to give an accurate temperature, such as 6115° C., because there is nothing that can be pointed out and labeled: "This is the radiating surface of the Sun." The "surface" is a radiating layer, the photosphere, probably thousands of miles in depth. The temperature of this layer varies widely with depth, so that 6000° represents the effective temperature of the effective surface.
That temperature is high enough to volatilize all known substances; it is higher than any chemical reaction can produce (most reactions known on Earth run the other way there: water yields hydrogen plus oxygen). Obviously the, this output terminal represents a higher concentration of energy than we can produce on Earth to-day.
Even on Earth, where the energy concentration has been diluted by nearly 100,000,000 miles of distance, the density is still nearly 650,000 horse power per square mile. Probably the greatest concentration of man-made power plants is centered about Manhattan Island; one plant alone generates 1,000,000 electrical horse power. Yet in all the clustered plants in that concentratedly developed little district, the most highly developed area on Earth perhaps, the electrical and steam-power plants could not equal the Sun's concentration of energy. And the Sun is working on the hard end of the inverse square law, so the tune of 100,000,000 miles.
At the Sun's surface, the power concentration is 70,000 horse power per square yard (enough to run an ocean liner). 3,970,600 square yards make one square mile. And about 3,000,000,000,000 square miles makes one Sun surface. The Sun, in other words, radiates about 450 million million million horse power. One two-billionth of that is sufficient to warm all Earth, for of all that vast flood Earth intercepts only that microscopic fraction.
But to astronomy, the Sun has yet other meanings. First, it is the lord and ruler of the solar system by its immense gravitational attraction, almost 1000 times the mass of all other members of the system combined. Second, historically, and first in interest now, the Sun is the only example of those monstrous atomic generators that sprinkle space that is close enough for detailed study -- the only available star. And, third, it is not only the ringmaster of the system, but almost certainly the place of origin of the other members; from it, the planets were almost certainly torn.
And that last is one of the most absorbing mysteries of all; for though dozens of theories have been advanced as to the mechanism of that creation, each has its difficulties, not the least of which is the absolute iron grip the Sun has on its surface matter. There are disruptive forces enough at work, space knows, but there is one titanic intergrative[ed. sic] force at work that paralyzes them all. Heat, expansive power of super-heated gas, the pressure of those driving floods of radiation, the wild, mad tornadoes of electromagnetic energy known as Sun spots, all tend toward disruption and dispersion.
But the gravitational grip of the Sun's enormous mass is not easily broken. Were the Sun as dense as Earth, the surface gravity would be even greater than it is, but with the low density of 1.41 times that of water, the surface gravity is still 28 times that of Earth. This high surface figure alone is not as important as the second fact, that at 2,500,000 miles, the gravitational force still exceeds Earth's surface gravity. Escaping matter must fight an intense field of millions of miles.
THE RESULT is that even driven by the wild heat motion of 6000°, hydrogen, lightest and most volatile of substances, is helplessly bound. Heat motion alone is incapable of lifting matter any great distance against that colossal, dragging force. But light pressure -- the intense, driving force of light quanta -- trapped by atoms and giving to the atom the momentum that would have permitted the light to escape. Riding on that jetting, almost tangible force atoms are carried up as individuals for millions of miles. Immense volumes of matter are sometimes caught up in a jetting blast of light and whirled out in immense prominence to distances of hundreds of thousands of miles. Calcium, hydrogen, helium, iron, sodium and other metallic atoms in gaseous state are hurtled out at speeds of a hundred or more miles a second.
Mice fleeing the cat's claws. Even should they attain 200--300 miles a second, the Sun's grip would be merely playing with them. 600 miles a second is the velocity required to escape that grip. Occasional bursts do reach immense speeds, approaching that velocity of escape sufficiently closely to recede to the distance of the planets before the burst of light that drove them outward fades away to normal intensity. It is these bits of matter, so driven out that, it is believed, may collect to form meteoric and cometary material. But it has not escaped from the Sun; it still must yield to his sway.
Those bursts of light that drive out the flaming, prevailing red eruptive prominences seem to be associated with Sun spots. A second, less spectacular type, the quiescent prominences, are not associated with those vast electromagnetic storms, but act more like Terrestrial clouds, vast incandescent masses of hydrogen, helium and calcium floating in the Sun's outermost, and strangest atmosphere, an atmosphere of light. Held up, apparently, by the steady drive of light from the surface below, they hang quietly, without much motion, changing but slowly in form.
The Sun spots themselves range in size from the limit of observability with a telescope to monstrous holes 100,000 kilometers in diameter, easily visible with the eye shielded by smoked glass or layers of exposed camera film. The disturbed surrounding surface may have a diameter 2 or 3 times as great, making the total area of disturbance often 100 times the area of all Earth. The spots appear as black holes on the Sun's bright surface. That blackness is due to their far lower temperature, often as much as 1000 degrees below the general surface. The resulting less-intense radiation makes it appear black. So cold and dim is this Sun-spot area, in fact, that the positive crater of a carbon arc is in comparison about -- say, twice as black. Black it may be against the Sun's incandescent surface, cold in comparison, but it is still far hotter than any source of light we use, on Earth.
When light moves through a magnetic field the spectrum lines are powerfully affected, depending on the relationship between direction of light and magnetic field; the light is plane or circularly polarized, and the lines of the spectrum are doubled or tripled. This gives a means of determining the nature and strength of Sun-spot magnetic fields. The spectrum shows them to be enormous, and intense, and in a line perpendicular to the Sun. These magnetic fields are, apparently, caused by a vast whirlwind spinning of the ionized gases of the Sun.
These vast magnetic storms on the Sun (only a hundred diameters of that body from Earth) not unnaturally cause powerful disturbances on Earth, greater auroras, magnetic storms, and floods of electrons. Radio and all electrical communication is frequently violently disturbed. Fortunately, the huge cyclones act like immense gun barrels, squirting their disturbing influences in a definitely aimed direction. Only occasionally, in consequence, is one of the greater storms so situated as to point directly toward Earth, and then, due to the Sun's rotation, it is not long so situated.
For the Sun rotates, and in that rotation, curiously, is one of the greatest stumbling blocks to theories that seek to explain creation. Once in 25 days at the equator, once in 34 at the poles. In consequence of this slow turning, the Sun, with 999 out of 1000 parts of the system's mass, possesses but 20 out of 1000 parts of the rotary momentum of the system! That fact, more than the constitution of the planets, is the stumbling block of theorists.