The World We Live In

‘I will speak of the Whole.’ — DEMOCRITUS

THE universe, as we picture it, is a system of thousands of millions of galaxies. Each galaxy is a swarm of thousands of millions of stars. And each star is a stupendous whirl of stampeding atoms in a frenzy of motion, driven by gales of light, now attracted, now repelled, repeatedly smashed and broken and rewelded into new forms — sometimes annihilated, the ultimate fate of all. But the atoms in their turn also are systems; they too contain wheels within wheels — though what may be their inner limit of littleness, or the galaxies’ outer limit of bigness, remains for the present beyond the reach of experiment or observation. Of these extremes we can only surmise, and by inference round out the picture of the Whole.

I

In one of these galaxies, the Milky Way, and situated somewhat toward the outer rim of its vast discoidal swarm, is a star of medium size and moderate temperature, already yellowing into old age — our sun. Until recently it was believed that once upon a time, two or three thousand million years ago, there occurred a rare event in this almost empty universe. Another star passed close by, perhaps within only a few thousand million miles, and the solar surface was troubled by the gravitational disturbance of this massive stranger. Ripples rose to huge waves, the crests broke, and great drops of sun stuff spiraled off into space toward the passing body. Some of these fragments may have been lost, but some were not. Unable to escape the sun’s control, they bent their courses into orbits mathematically ordained by their masses and motions, and so began to revolve round the parent star.

This picture is derived from the well-known planetesimal theory of the origin of the solar system; it seems reasonable and probable on grounds of celestial mechanics, and has been generally accepted. New evidence recently offered by the apparent recession of the remote galaxies has raised serious doubts, if not flat contradictions, of the theory. For, on the testimony of these far-off runaway star systems, the whole universe appears to be of about the same age as the earth. The indicated time scale suggests that the solar system, the sun, and all the stars came into existence simultaneously — whether from condensation of the primordial nebulæ, or from the explosion of a unique massive atom into which was concentrated all the mass of the universe, or from some other cause, we can only guess.

But, whatever the formative process may have been, the earth was one of the fragments which in some way began to revolve round the sun. Gradually it cooled, a crust solidified, and the enclosing cloud of water vapor condensed into oceans. About a thousand million years ago protoplasm appeared, first in the sea, the rocks tell us, then to crawl upon the dry land and spread its web of life over the earth. Sea beds upheaved into mountains, lands subsided into new sea bottoms, ice invaded the temperate zones. Life was pushed upon, crowded, preyed upon. At last came man and the mind of man, with its unique capacity to wonder, to inquire, to seek causes, to meditate on the ineffable mystery of this intricate Whole.

The crust of the earth is only a few miles thick. Beneath it the molten rocks and metals simmer in fervent heat, and are prevented from bursting into flame only by the enclosing shell of granite. Above the granitic and other igneous rocks is an intermediate skin made up of the sedimentary rocks, the covering soil, and other surface minerals, including water, for three fourths of the solid surface is overlaid with ocean. The outer skin is the atmosphere, a layer of nitrogen, oxygen, and other mixed gases which surrounds the globe to a height of more than a hundred miles, though nine tenths of its substance lies within the first six miles.

These surface features — the atmosphere, the sedimentary rocks, the soil, all the growing things that spring from the soil — are products of solar radiation. A permanent change of only a slight percentage in the sun’s energy, either way, would so alter the surface conditions that life as we know it would speedily disappear from the earth.

Between these two fires, then, — the banked embers of the cooling star fragment on which we live, and the flaming incandescence of the star we are hitched to, — stand man and his companions in life, the birds and beasts and other animate creatures. How scant and frail they are — this company of life that could be snuffed out by so slight a change in the solar temperature!

Recently, at the Bureau of Standards in Washington, Dr. Paul R. Heyl set up a balance to weigh the earth, and with that most delicate weighing machine he put the planet on the scales, as it were, and measured its avoirdupois. Never before has so huge a mass been determined within such exact limits. But if suddenly the whole company of life, plant and animal, had been swept from the earth, — if we can imagine them loaded into a fleet of rocket ships and whisked off to Mars or some other asylum, — their departure would have made not the slightest difference in the result. The scales cannot detect so slight a fraction of the earth’s mass.

And yet, it is in this small living fraction alone that consciousness has arisen. The greater wonder is not the atoms, the stars, the galaxies — it is the mind of man which has perceived these mysteries and traced the thread of law that runs through all. But what is mind? Where does it dwell and under what conditions? With what does it perceive and trace and extend its knowledge?

Such questions as these remind us that man himself is a structure of atoms,

. . . thinking atoms, whose far-seeing eyes, Guided by thoughts, have measured the faint stars.

He too is a bit of star stuff, an animate wisp of the Milky Way.

‘Compound it how she will — star, sand, fire, water, tree, man — it is still one stuff, and betrays the same properties,’ says Emerson.

The universe as a whole includes man.

II

Thus the observer is inseparable from that which is observed. ‘We ourselves are part of nature and therefore part of the mystery we are trying to solve,’ is the way Max Planck puts it. The eye that sees is part of the object it is seeking to perceive — and under the new conception of quantum mechanics this involves complications. The infinitesimal dimensions of the inner structure of things and the swiftness of their motions create serious problems for a detecting instrument so restricted as the human eye, adapted as it is to a narrow range of radiations representing only a small proportion of the actual wave lengths in nature.

The world is real enough, but our fragmentary glimpses of it change, not only with the spectacles through which we look, but also with the scene through which we pass — an ever-shifting panorama that will be different for our children even as our view is different from what our fathers saw.

This is not to say that the obvious aspects of nature have altered conspicuously. They have not. The constellations appear much the same as they were when the Chaldean shepherds began to name them. The firmament seems just as spacious now as it did to the adoring eye of Joseph Addison. Poets still invoke the ‘quiet’ stars as perfect symbols of peace and constancy. And the ‘firm’ earth and the ‘solid’ rocks are not merely figures of speech; they are also brute facts against which we may stub our toes as painfully as any Dr. Johnson.

Toes and eyes, the sights they see and the touches they feel, are the apparent world — the everyday world of sensory impressions. Is that world a dream? Modern science seems to be in process of saying so. The apparent world is the world of ‘as if,’ to borrow Vaihinger’s famous phrase. The rocks act as if they were solid, and we find that by assuming a firm earth we can build our foundations and raise our massive structures, and the casualty companies will readily insure them against all risks, irrespective of Lord Rutherford and the Due de Broglie, who proclaim the hollowness and the immateriality of all things. The stars seem to keep their relative positions when sighted through our sextants, and mariners find that they can still determine longitude and navigate ships by these constant points of light, regardless of the warnings of astrophysicists who declare that there are no constant points of light, no fixed stars, no hitching posts anywhere, at any time.

Behind the apparent world of ‘as if,’ another world is hidden.

III

How deeply it may lie hidden can be illustrated briefly in the case of two familiar objects of the night sky, the famous twin stars, Castor and Pollux.

Dr. Robert G. Aitken, of Lick Observatory, has traced the popular history of these Heavenly Twins in the myths of peoples antedating the Greeks who named them; and always, he finds, they have been recognized as a pair. Even such widely separated observers as the Assyrians of Asia Minor, the Anglo-Saxons of Britain, and the Polynesians of the South Seas, called them twin orbs and celebrated them as such. So close together in the sky, so near the same degree of brilliancy, so unchanging in their attendance on one another, they looked as if they were twins.

But the telescope, the spectroscope, and the photographic plate report differently. They show that the two stars are of different spectral class, and are unrelated in every way. Pollux is situated some 180 million million miles from the earth, and is speeding outward at sixteen and a half miles a second, while Castor is nearly one half again farther away and is whirling a separate course at about nine miles a second.

Clearly they are two strangers that just happen to be near the same line of sight when viewed from our present position in space. Ten million years ago we should never have thought of them as twins, and ten million years hence they will appear so far apart that the name will seem a queer misnomer. But for the fractional moment of eternity during which man has been alert to the stars they have shown no perceptible change, so relatively minute is their motion across the sky in comparison with the depths of space to their great distances. The human eye is not capable of discerning the distinctions wrought by such vastness.

But more is hidden. Suppose we dismiss the misnamed twins, and concentrate attention on Castor. Through the telescope it shows itself to be not one star but two, a binary system consisting of a massive inner sun and a fainter companion revolving round a common centre of gravity. The two stars are separated by a distance more than a hundred times the distance between the earth and the sun. Nor is this all. When the more discriminating eye of the spectroscope is added to that of the telescope, it is seen that each of these constituents of Castor is in its own right a double star. Strange!

But wait, we are not yet done with these stellar subtilities, for under more powerful glasses still another star, faint and red, shows itself as part of the Castor system; and under a Mount W ilson spectrograph it too has photographed itself as a binary.

Thus what appears to the eye as a single fixed star, the steadfast white Castor of the constellation Gemini, is in reality a cluster of six stars grouped in three pairs, each star revolving in an orbit and with a velocity peculiar to itself, and yet all traveling persistently in a southwesterly direction at a constant speed of nine miles a second. What mariner, knowing the true inwardness of Castor, — its interior whirligigs, its gyrations, its headlong flight from its ancient accustomed place on the star map, — would ever rate it a steadfast mark to steer by?

Castor is not the villain of the piece, however, but only a shining example of the inevitable complexity that lies within things. The placid sky is revealed by modern astrophysics as a vast heterogeneity in which innumerable suns, singly or in multiples, are darting about in almost all directions like the excited molecules of a gas.

Vega is approaching at eight miles a second, Aldebaran is receding at thirtythree miles a second, Arcturus is crossing at eighty-four miles a second. The two end stars of the Big Dipper are moving in one direction, while the other stars of this constellation are pulling away at enormous velocity in the opposite.

Nor is our star an exception: the sun is spinning a dizzy course toward the outer rim of the Milky Way at twelve miles a second, trailing the earth and all the other planets with it, and at the same time the solar system is being swung in a gigantic arc at two hundred miles a second as the Galaxy itself rotates like some colossal stellar pinwheel. From this shifting, whirling, fleeting mote among the stars, this ‘ firm ’ earth, man has essayed to survey the cosmos and to appraise of what and how the world is made.

The panorama continually changes. We can get no contemporary scene.

Everything is us it was, never as it is. We see the sun as it was eight minutes ago, Sirius as it was nine years ago, the Pleiades as they were five hundred years ago.

On a clear moonless night in autumn and winter the eye may distinguish a cloud of pale light no bigger than the moon in the constellation Andromeda. This spiral nebula, one of the nearest of the outer galaxies, appears to us as it was 800,000 years ago — and what may have happened since then to its uncounted stars and star systems our grandchildren must wait another 800,000 years to behold, if they can.

The Andromeda Nebula is at about the outer limit of naked-eye visibility, but with a telescope we may reach millions of years into the past of the universe. And when the sensitive photographic plate is harnessed to the most powerful telescope, hundreds of millions of years are bridged. The rays of these remote bodies have been called fossil light, and indeed they antedate most of the fossils that have been found in the earth. One wonders how so frail an entity as light, which can be stopped by a film of gas or a particle of dust, can t ravel at its constant velocity 186,000 miles each second for hundreds of millions of years without deterioration. Of course, some rays are stopped; we see and photograph only those that get through, but they are so numerous as to demonstrate the relative emptiness of space and suggest the commodious scale of its architecture.

IV

In considering the scale of the physical world, we distinguish two categories: (1) the known and measurable, and (2) the unknown or as yet immeasurable, which, however, we apprehend or infer and are able to estimate by a judicious extension of the known data.

One effect of the new physical theories and discoveries has been to delimit the scale of the latter category, and actually to restrict the possible range of the unknown. The old idea was infinity; a ray of light traveled in a straight line, and unless stopped by some obstructing body it would go on forever, ploughing an endless path through infinite space. Science has had to give up that conception as the powerful instruments of modern astronomy, by their very act of plumbing deeper into space, have adduced evidence in favor of the idea that the world is finite — a quite definite quantity, not only of matter and energy, but also of space. There is small probability that man will ever be able to construct an optical instrument powerful enough to photograph the image of a star situated at the opposite side of the universe, but it is quite possible to compute the approximate distance of such a star.

When we come to the first category, that of the known and measurable entities, the effect of recent research has been enormously expansive. ‘ Mill ions ’ and ‘billions’ have been so bandied about of late that few readers, I think, are aware how new the actual attainment of immense distances is. As recently as 1925 the two most remote objects known were two outside galaxies — the Andromeda Nebula, at a distance then estimated as 952,000 light-years, and another designated as N.G.C. 6822, which was rated at about 1,000,000 light-years distance. These distances were staggering to the imagination of 1925, and Professor Jeans (not yet Sir James), commenting at the time, suggested that they probably indicated the approximate limits of the universe.

‘We may suppose,’ he said, in a paper published in December of that year, ‘although it is little more than a guess, that the most remote objects of all in our universe are at four times the distance of these two remote objects, and so at 4,000,000 light-years from us.’

This was in 1925, less than ten years ago. Man had seen a million lightyears into the abyss, and one of the leading cosmologists estimated that we might expect eventually to penetrate four times that far. But 4,000,000 was at that time deemed the outer limit.

To-day? The spectra of objects believed to be 150,000,000 light-years distant have been photographed at Mount Wilson Observatory with the 100-inch telescope, and for straight photography under the most favorable conditions the reach of this instrument is said to be effective out to 350,000,000 light-years. Thus by 1934 the astronomer was able to look more than three hundred times as far as the astronomer of 1925 had looked. And there is assurance of three times yet deeper soundings when t he 200-inch telescope, now under construction, is completed.

Much of our recent gain in space penetration must be credited to the astronomers’ gain in powers of interpretation. Astrophysics to-day has a surer grasp of its materials and technique. Photographic images that were attained ten years ago, but were little understood then, have meaning now; we are more familiar with the earmarks of great distances, t herefore are able to recognize them when they appear. This added knowledge and increased facility in reading observational results — along with the instrumental gains contributed by improvements in the sensitivity of photography and by new optical and electrical devices auxiliary to the telescope — have, in a sense, multiplied seeing power.

It is this recent multiplication of our seeing power that has provided the data on which cosmologists have founded their current estimates of the extent of the Whole. In the present state of universe building, when, as Harlow Shapley points out, ‘there is an overpopulation of hypotheses,’ it is necessary to allow for a wide margin of probable error in citing the authorities. Cosmical statistics are not quoted dogmatically, like the price of Steel or the claimed vote of a candidate for public office. The figures are given cautiously as ‘of the order of,’ by which is meant a liberal plus-or-minus tolerance.

By photographing representative sections of the sky, it is possible to take a census of the stars. At the Harvard College Observatory I saw one photograph which includes the images of more than two thousand outside galaxies — two thousand Milky Ways imprisoned on a single plate of fourteen by seventeen inches dimensions! It’s a rare quadrilateral that will yield so rich a harvest, but, taking all the results that have been gathered, it is estimated that the number of galaxies composing the universe is of the order of 500 million million.

How many stars to the galaxy? Counts have been made of selected patches of the Milky Way, — one young observer at the Harvard southern station has actually counted more than two million individual stars, — and from these and on dynamical considerations it is estimated that our Galaxy is of the order of 100,000 million suns. The outside galaxies are not so large, however. For, whereas the Milky Way diameter is of the order of 100,000 light-years, the Andromeda Nebula measures only about 80,000 light-years across, and some of the other spirals are considerably smaller. It is possible, however, to apply statistical methods and arrive at safe averages.

From all the data available it is estimated that the total mass of the universe is of the order of 1.08×1022 suns. Eddington, with his mathematical equations, has dissected these suns into their ultimate particles, and estimates that in the whole world there are 1.29×1079 particles.

V

According to the theory of relativity, this universal mass of matter gives to space a certain shape and size. Einstein assumed that the world was as full of matter as it could conveniently hold, and the picture he derived was of a universe in equilibrium, a stable system of certain fixed shape and size. But recent astronomical observations reaching out to 150 million light-years have made it difficult to accept any longer the original Einstein World, and to-day we are asked to accept the picture of the cosmos in process of expansion. This means, of course, that its size is continually changing. The present radius of curvature is reckoned by various authorities to lie between 2000 million and 20,000 million light-years.

This is a wide range of tolerance, even for a universe. But it must be remembered that here we are groping through an enormous shadow of uncertainties; we have actual spectral data out to only 150 million lightyears, and beyond that must extrapolate. Not only must we take into account the galaxies and their constituent stars and nebulæ, but also the dark nebulæ of whose extent we can only guess, and the invisible dust between the stars and perhaps between the galaxies. This invisible matter may possibly outweigh the total mass of the stars; and in any event its mass, though unseen, directly affects the size of the universe. The latest estimate of size is that published by Edwin Hubble, of Mount Wilson Observatory, in 1934. Assuming that what we see through the largest telescopes is a fair sample of the Whole, and that the density of space is uniform throughout, Hubble figures that the universe has a present radius of curvature of the order of 3000 million lightyears.

The biggest thing in the world, then, is the world itself, with an estimated radius of about 3000 million light-years, or approximately 18×1021 miles.

The smallest particle of matter for which we have physical measurements is the nucleus of the atom. Its size may vary slightly from one element to another, but in general the nuclear diameter is found to be of the order of 10-12 centimetre — approximately 1/400,000,000,000 inch. The smallest nucleus would seem to be that of the hydrogen atom, but in all experiments it behaves as though it were a massive point of zero dimensions, therefore one cannot speak with any precision of the diameter of the hydrogen nucleus. Quite accurate measurements have been made of the nuclei of helium, nitrogen, aluminum, and other elements, and they all show about the same dimensions, ranging in diameter between 10-13 and 10-12 centimetre.

The nucleus itself, in the case of most atoms, is made up of subsidiary particles. We have no knowledge of the sizes of these interior bodies, for we know them only after they emerge from the atomic centre, when they seem to take on different properties and, perhaps, different dimensions. This nuclear region is the frontier of atomic exploration to-day — as the region beyond the known galaxies is the astronomical frontier. Thus, at either end of the scale of things, the known blurs into the unknown.

But the known is vast and wideranging. To get some suggest ion of its reach, let us make an assumption and derive some comparisons. Imagine the earth reduced to the size of the period at the end of this sentence. The dot of ink measures about a fiftieth of an inch in diameter. With our planet thus shrunk from its mean diameter of 7918 miles to one fiftieth of an inch, — a reduction to less than 1/25,000,000,000 of itself, — and all the other dimensions of the universe deflated proportionately, we arrive at these interesting contrasts: —

Distance, earth to sun — about 19 1/2 feet
Distance to nearest star — about 1005 miles

Diameter of Milky Way — about 23,380,000 miles

Distance to farthest photographed galaxy — about 81,830,000,000 miles
Radius of universe — about 701,400,000,000 miles

We are still faced with incomprehensible millions. To glimpse the infinitesimal littleness of our scale at one extreme, and its vastness at the other, let us focus our imaginary optic glass to the very limit of its reducing power — that is, shrink the image of the earth to the size of the smallest thing we can measure, the atomic nucleus. Everything else in the world contracts in the same ratio, and we now have these magnitudes: —

Distance, earth to sun — about 1/34,000,000 inch

Distance to nearest star — about 1/125 inch
Diameter of Milky Way — 15 1/2 feet
Distance to farthest photographed galaxy — about 10 1/4 miles
Radius of universe — about 88 miles

Dimensionally, then, the earth is to the atomic nucleus as the universe is to 88 miles.

That is the present range of dimensions, the scale of physical things, so far as science has been able to gauge them with its new eyes.