The Mystery of the Vanishing Universe (Jan, 1949)
This is an excellent article, really not much different from current explanations of cosmic expansion.
Yes, I know the numbers are way off and they’re missing dark matter, dark energy and a host of other things. But from a layman’s perspective, I think it gives a very good understanding of the basic concepts.
The Mystery of the Vanishing Universe
In the case of the disappearing galaxies, the evidence is contradictory and the jury’s hung
by Morton M. Hunt
IN the files of the world’s astronomical observatories there are a number of photographs, enlarged from tiny negatives. They are hazy, smeary pictures, almost formless; all they show are some rather indistinct patches of light. But because these streaky patches of light never quite appear just where they should on the photograph, but are joggled a little bit offside from where all calculations say they should be (a phenomenon known to astronomers as the “red shift”), the photographs form the evidence of the greatest mystery of all science—the beginning of the universe, and its ultimate end.
What the pictures suggest is that the whole universe is blowing up—or rather that all the stars in the universe are scattering out and getting farther from each other. The stars—in fact, the total matter in the universe—are, in the words of the great British astronomer, Eddington, “dispersing as a puff of smoke disperses.”
Knowing the rate of this expansion, scientists can figure backwards to a time when it all started, a time when the universe existed as a ball of unimaginably concentrated fluid matter possibly no larger than a hand—had there been any hands to compare it with. Conversely, the scientists can figure the time when the universe may be so completely dispersed as to be a vast void in which matter, infinitely attenuated and diluted, will be practically non-existent. Doomsday will be hardly a raging fire; it will be more like a slow dissolving into empty coldness.
At least, that’s what some of the astronomical detectives make from the photographic evidence. The trouble is that there are half a dozen conflicting points of view among the stellar sleuths. And to make everything thoroughly confusing, each one of the theories can be proved absolutely inconsistent by its adversaries. If only the photographic evidence weren’t there, everyone might be perfectly happy. But that’s the mystery of it. Something has. to be explained; it can’t be escaped. But the explainers are still groping in the very dark outer spaces for an answer.
Now that the 200-inch telescope on Palomar Mountain in California is busily scanning the deeps of space, the answer soon may be forthcoming—perhaps next year, perhaps in a few years. When it does come, astronomers the world over will heave happy sighs, as they begin to put the universe together in better shape.
Before you can understand what the fuss is all about in this greatest of all mysteries, there are a few words you ought to know, if you don’t already.
First item is the solar system—the sun and the planets that revolve around it, one of which we call Earth.”
Next one is the old familiar word star. A star—any star—is a huge incandescent body in space, like the sun (which, by the way, happens to be a pretty mediocre star, a little above average in size and brightness, and wholly undistinguished from any other star). Most stars are quite far from any other stars. For example, Proxima Centauri, the star nearest the sun, is so far away that its light takes nearly four and half years to reach us—or, as astronomers say, it is four and a half light-years distant. A light-year, if you like big numbers, is about 6,000,000,000,000-six trillion-miles. If both the sun and Proxima Centauri were only as big as Ping-pong balls, they’d be 500 miles apart, on such a scale.
Yet despite this unthinkable order of distances, you haven’t begun to get to the really wide open spaces. For imagine now, if you can, a host of 40 billion such stars, each about as far from its nearest neighbors as the sun from Proxima Centauri. Take this vast aggregation and shape it like a flat cookie, or spiral, somewhat thicker in the middle and tapering off around the perimeter. This vast but thin-spun thing, some- thing like a disk-shaped blob of smoke particles, is about 100,000 light-years wide in diameter, so that a spectator on one rim could see the other rim only as it used to be 100,000 years earlier. The entire thing, when seen from a very great distance away in empty space, would look like this, when all its billions of stars seemed to merge together.
Well, that’s variously called an island universe, an extra-galactic nebula or more simply a galaxy. We live in one, as you might have guessed; we call ours “the Milky Way,” and we can’t see it as a spiral cookie because we’re in it. More accurately, our sun together with its planets is just one of the 40 billion stars, and happens to be about two-thirds of the way out from the middle towards the edge; consequently, we can see the Milky Way as a band pretty much all around us.
Now suppose that there are millions— actually millions—of such galaxies. Huge as they are, they are afloat in an immense sea of space, and are scattered out at immense distances from each other. The average distance between neighboring galaxies throughout the universe is about 100 times the diameter of the galaxies themselves. The average distance between any two galaxies is two million light-years, which comes to twelve million trillion miles—12,000, 000,000,000,000,000 in round numbers, if that means anything to you. (To get some idea of what that number means, suppose there were a thousand fast bank tellers who could each count out five one-dollar-bills per second. Working day and night without ever stopping, they would require about 80,000,000 years to count out that many dollar bills.) The broad picture of the universe, then, is that it looks mostly like empty space. Here and there throughout it are wisps of cloudy haze, either floating alone, or in loose clusters. Each wisp is a spherical or spiral cloud of particles, which are incredibly minute in relation to the wisp itself; yet each of these particles is a star probably as large and bright as our own sun.
But even this is not all. For although astronomers already know of the existence of millions of these galaxies (which appear to us as tiny hazy patches in the sky, usually invisible to the naked eye), this whole picture of the universe probably represents less than one per cent of the entire thing. Man just hasn’t been able to see the rest of it as yet.
As far back as the time of the American Revolution, the famous astronomer Sir William Herschel had likened our own system of stars—our Milky Way—to the external galaxies, which in his small telescope appeared merely as hazy specks of light. But not until the early years of this century did the notion win wide acceptance. The main reason was that there was no adequate way to measure their distance, and so be sure they were outside the Milky Way. As a matter of fact, the only method used was triangulation (similar to a Boy Scout’s measuring of the width of a stream), which could measure only those stars less than 100 light-years away—and that took the astronomer only one-tenth of one per cent of the distance across our own Milky Way, to say nothing of getting outside it to check on all the other galaxies.
Then in 1912 astronomer Henrietta Leavitt studied a certain type of star which pulsates, varying in brightness over a period of a few days or a few weeks, and discovered that the slower the pulsation, the brighter the star Harlow Shapley saw in this the key to the distances of the galaxies. Even though great distances could make the pulsating star look dim, he realized he could judge its true or absolute brightness by the rate at which it got brighter and fainter. Knowing its absolute brightness, he could figure its real distance.
By locating such stars in the galaxies —and they were becoming more clearly visible with higher-power telescopes-it became clear that the millions of galaxies actually did lie outside the Milky Way and were, like it, collections of billions of stars. An astronomical free-for-all ensued, with everybody combing the sky and the photographic plates for the tell-tale Cepheid variables, as the pulsating stars were called, and then calculating the distances of the galaxies that contained them.
That’s when the trouble started. An astronomer named Vesto Slipher was working at Lowell Observatory, in Flagstaff, Arizona, trying to learn something about the motion of these galaxies. He wasn’t content to know how far away they were; he wanted to know whether they moved, and if so, how fast they were going.
The method he used was what is called “spectroscopic analysis.” He aimed his telescope at the galaxy, passed its light through a slit and then through a complicated kind of prism. Sir Isaac Newton had first found out two and a half centuries before that a prism would break up light into its constituent colors. Since then, scientists had perfected prism analysis, so that on the spread-out band of colors (or spectrum) yielded by the prism, they could easily identify certain dark lines that revealed the presence of specific chemical elements in the light-source. Best lines of all were the two dark strips crossing the spectrum band, caused by the presence of the element calcium.
Whenever Slipher set up his apparatus on some distant galaxy, he could break up its faint light with the spectrograph and locate the dark lines of calcium every time. Of course, they should always have been in the same spot, if the galaxy were stationary; but if it were moving, those lines would be a little bit off to one side or the other. The reason for this is familiar to everyone who has ever heard a passing train blow its whistle, or a passing auto blow its horn.
The sound, as you remember, goes something like this: be-e-e-e-y-ou-ou-ou. The sharp drop from high pitch to low pitch occurs as the car or train passes you and starts going away from you. Sound depends on a number of vibrations reaching your ear each second. If, say, 440 sound waves hit you in a second, you hear a note that corresponds to A in the middle of the piano’s range; if more hit you, you hear a higher note. When the auto comes at you, even though its note may be a pure A, more than 440 waves hit you per second and you hear a higher note; when it goes past, it is still blowing an A, but each wave is released a little farther away and takes longer to get back to you, so that less than 440 hit you each second. The sound drops down in pitch. This is the well-known Doppler effect, first analyzed by Christian Doppler of Prague, back in 1841.
Light, of course, consists of vibrations, too (though not air vibrations, like sound). Many more of them hit you per second—500 trillion per second for yellow light, for example. The color you see is like the note you hear: If more vibrations hit you per second, you see a “higher” color—a bluer one. Fewer vibrations produce a redder color.
But let’s get back to Dr. Slipher, whom we left in the Arizona desert. He hoped to learn whether the galaxies were moving, by passing their light through his spectroscope. If the dark lines of calcium didn’t appear where they should, but were shifted toward the blue end of the spectrum—the higher frequencies—he would know that the entire galaxy was moving toward our own galaxy. If the calcium footprints were shifted towards the red end of the spectrum, the galaxy was moving away from our own. And by some fine measuring of the distance on the photographic plate, and some careful computations, he would even know how fast it was going in miles per second.
The strange thing, he found, was that in nearly every case the calcium lines were shifted toward the red end of the spectrum, meaning that almost all the several dozen galaxies he had observed were moving away from us rather than toward us. But he didn’t probe much further into the matter, and beyond thinking it definitely odd, didn’t suggest that a larger mystery was contained in these observations.
Along came the astronomer Edwin Hubble (SI, Nov., 1947) of California. With keen mathematical insight he probed into Slipher’s figures, and noticed an extremely odd thing: The farther away the galaxy, the faster it was running. If this were true, and if it checked for the other galaxies yet to be examined, it could mean—the most ridiculous notion ever to arise in astronomy—that every other galaxy was fleeing our own, as though we had some kind of colossal cosmic b.o.
But astronomers have learned humility in the face of the great things they see every day, and it was altogether too presumptuous to suppose that our own galaxy—no different from millions of others—should be the center of the retreating universe. Rather, it might be that the whole universe itself was expanding, and hence all particles in it were getting more distant from all other particles. In an explosion, for instance, where a mass of grains is shot outward, each grain gets farther from every other grain as the explosion moves outward. To an observer on such a grain, every other grain would seem to be moving away from him—and the farther away the other grain, the faster it would be moving. So we needn’t be the center of the universe. Instead, the entire universe might be expanding, and all the galaxies in it might be spreading out farther from each other in a huge cosmic dilution of matter.
The whole thing seemed absurd-absurd on a grand scale. Sir Arthur Eddington said of it that it was “so preposterous that I feel almost an indignation that anyone should believe in it except myself.” But plenty of evidence was there, and more was piling up fast.
The Night Watch In a grand rush to understand this greatest of all facts about the realm of creation, astronomers the world over swung their telescopes on the-galaxies. Night after night they would huddle in their fur robes in the chill domes of mountain-top observatories. The telescope would follow a galaxy slowly across the sky, picking up a wisp of light so faint it hardly made a mark upon the photographic plate. Often the plate would have to be covered after the night’s work and re-exposed the next night and the next, sometimes for eight to ten nights, before one readable spectrogram was obtained.
And what was it like? A tiny smeary photograph, such as was described at the beginning of this article. Back in the early 1930’s, before better techniques were perfected, the photo negatives were only a tenth of an inch long, and had to be magnified and then measured with great precision, before the calculations of the galaxy’s speed could be made. A difference of l/50th of an inch would have tremendous significance.
But the evidence was overwhelming. After years of this work, and after the accumulation of hundreds and thousands of records, it was found that only five galaxies were moving toward us— and these were near ones—while all the rest were moving away. The farther they were, the faster their apparent speed. Out at the sublime distance of 240 million light-years there were galaxies streaking away from us at .25,000 miles per second—one seventh the speed of light. And at 500 million light-years we could see galaxies too faint to be spectrographed, which were probably moving at one-third the speed of light.
Naturally, then, as bigger telescopes would be built, they would rapidly approach the distance at which galaxies would be moving away at or above the speed of light. And, therefore, they would be invisible. They would, in fact, be to all intents and purposes non-existent. And even those we could see would be approaching that vanishing point continually. In fact, after a while there would be no galaxies visible at all except our own Milky Way. In a few billion years all others would have vanished beyond the speed of light. “Let us make haste to study them before they disappear!” exclaimed Eddington.
At any rate, the red shift exists beyond any shadow of doubt. And it implies motion—fantastically fast motion. That much is agreed. But from that point the difficulties begin.
First of all, if everything is expanding at a rate we can measure, then it is a relatively easy matter to figure out how long ago it all started—with everything all in a heap, so to speak, before the big blow-out. Every astronomer calculates the beginning of the expansion a bit differently; some place it at about two billion years ago. But Hubble, who spotted the whole business in Slipher’s figures, has refined the calculations and believes that it all started only one billion years ago.
That means that one billion years ago —if the red-shift evidence is correct—all the galaxies and all the suns within them were one mass of super-concentrated, super-hot matter. No solids or compounds existed then in that pre-explosion fluid. It might have been something like an incredibly dense star; or it might even have been nothing but an infinitely small point of infinitely concentrated something-or-other.
Flatly contradicting this, however, is the undeniable truth that life existed on earth more than a billion years ago, on a crust and in an atmosphere not too unlike our own today. In addition, there’s the evidence of uranium, which acts as a kind of cosmic clock to belie the red-shift timetable. Uranium imprisoned in the earth’s rocks slowly disintegrates, leaving behind in the rock both helium and lead. Laboratory experiments have been made to measure the rate of decay of uranium; half of it is gone in about 4.5 billion years. So by delicate tests on the uranium-bearing rocks, we can tell how long the uranium has been there, breaking down into lead and helium.
The evidence is simple: it’s been there two billion years. That means that the earth was a solid, relatively cool mass two billion years ago. Some even put it higher; Harlow Shapley puts the earth’s formation at somewhere about three billion years ago.
How Old Is the Universe?
Furthermore, there are all sorts of stars in the sky—young ones, middle-aged ones, senile ones. From what we know of the sun, it will require many billions of years to go through its whole life-cycle. But then how about the older stars now in existence? Where had they been when the lid blew off? Are they young, but prematurely aged? If so, why? Or are they really old? If so, how could they have been in the midst of the primal blast, only one billion years ago? Some astronomers insisted that this kind of evidence showed the universe was far older even than three billion years. Sir James Jeans figured it as being at least 10,000 billion years old. The conflict seems irreconcilable.
Another question arises about all this outward motion of the galaxies: Where are they going to, anyhow?
Once upon a time men might have believed that the universe extended out infinitely in all directions, and that the galaxies were simply moving out into empty space. But Einstein changed all that. His theories—amply proved by astronomical observations—pictured space as consisting not of straight lines or straight distances, but as being curved. Wherever matter existed in space, it bent or misshaped the space as a flaw in steel might distort and create strains in the metal all around it. Space curvature accounted for the motion of bodies and the motion of light with greater accuracy than Newton’s theory of gravitation. Einstein’s concept explained the actions of the universe with the most satisfying accuracy.
But the curved-space concept did away with the idea of an infinite universe. What happened was that the total amount of matter in the universe caused its space to keep bending on around until it closed up and returned on itself. Don’t try to picture that. You can’t do it any more than you can visualize a minus quantity of anything. It’s mathematically true; the proof lies within the view of telescopes when they observe certain strange gravitational effects, and certain minute irregularities in the orbits of heavenly bodies. But to picture such a universe, round and finite, yet without any external boundary around it, is not for our minds.
James Jeans, the English man-of-all-science, said that “it becomes a bewildering paradox as soon as we try to grasp it in terms of a mechanical model.” His compatriot, Lord Bertrand Russell, added, “It is the privilege of pure mathematicians not to know what they are talking about.” Russell, needless to say, is a pure mathematician.
But if Einstein’s universe can’t be pictured, an analogy may help you to understand it. If you lived on the surface of a globe, and if you could understand two dimensions but were a perfectly flat creature unable to comprehend “up,” you would think your universe infinite because no matter how far you looked around it, or how far you crawled, you never came to an edge. Yet, with good instruments, you’d be able to measure curvature, and your brain would tell you that somehow the universe closed around on itself and was really finite. You’d know it was so; but you wouldn’t be able to draw a picture of it.
Now on the surface of such a sphere— or let’s make it a rubber balloon—put a number of spots, each spot made up of a billion little points. The spots are galaxies, the points their stars. They are a certain distance from each other. Now let some great cosmic breath blow the balloon up slowly. Each spot will be- gin to get farther from each other spot, though none of them is actually moving across the surface of the balloon. And from any one spot the law of motion will be simple: The farther away another spot is, the faster it will seem to be running away. That’s the expanding universe in which we live. And now that you’ve seen it, forget it. That’s only an analogy, and the universe probably isn’t like that at all.
Getting back to the troubles of the expanding-universe theory, if space isn’t infinite, then the galaxies aren’t expanding into it. Rather, space is finite and it is expanding, like the rubber balloon. That accounts for where the galaxies are going quite nicely. One problem, at least, seems to be solved.
But another leaps up to take its place. Let’s grant the universe is as Einstein says; and let’s grant the red shift really shows an expansion, despite the contradictory evidence as to how old the universe is. But if the galaxies are assumed to be receding, there arises a trouble called the “dimming effect.”
If a small boy were blowing beans at you through a beanshooter, from the back of his father’s open car as it sped away, the beans that hit you wouldn’t have as much force or energy as they would if the car were standing still. Likewise, light coming from a receding source will have less energy—that is, will look dimmer—than the same light coming from a stationary source.
It’s Closer Than You Think Therefore, each galaxy is not as far away as we think. The Cepheid variables within each galaxy, whose brightness was the key to the galaxy’s distance, are actually brighter than they seem. All the measurements are wrong. But they can be corrected mathematically.
Applying this correction, astronomers suddenly got a strangely lop-sided picture of the universe: The farther away from our own galaxy you went, the more densely you found other galaxies concentrated in space. There seemed to be, in fact, a bunching-up of galaxies, a thickening shell of matter, all around the margins of space—and beyond would lie even greater concentrations.
That’s a disturbing and unnatural picture, to physicists and astronomers. Matter ought to be pretty uniformly distributed through space, just as air is uniformly distributed in a room.
How to get rid of this bunching effect? Einstein himself had an answer. The bunching-up, he felt, was purely an observational error due to the curvature of space. Einstein then calculated just how much of a curvature the universe would have to have (what its radius would be) in order to produce such an error. It came out to be only six times as great as the distance the 100-inch Mount Wilson telescope could see (the 200-inch telescope on Palomar Mountain should see one-third the way around the universe).
Einstein’s solution to the bunching-up difficulty sounded fine. Then along came Hubble once again, to check on it. He performed an astounding feat-he counted all the matter in space; he added it all up. He did this by photographing a piece of sky bit by bit on 1,283 negatives, and counting the galaxies that appeared on the pictures. The total came to about 44,000. Multiplying this figure to extend it over the whole sky, this meant there probably were 100 million galaxies within the range of the 100-inch telescope.
That’s quite a lot of matter. But it’s afloat in quite a lot of space—so much so, in fact, that averaged out, the density of matter throughout the universe is comparable to about one hydrogen atom per cubic meter—a vacuum surpassing by far the best that could ever be produced in an earth-bound laboratory.
Another Impasse The trouble with all this is that, according to Einstein himself, the curvature of space is caused by the density of the matter in it. And the amount of matter that Hubble had counted in space just wasn’t nearly enough to make Einstein’s curvature the right one. Space did curve, Hubble agreed, but not at the rate Einstein had called for. And only that wrong rate could explain the bunching-up effect. So once again astronomers wound up in an impasse.
Forgetting all this, and merely agreeing that the evidence seemed to show an expanding space, astronomers still couldn’t agree on what it meant. Some insisted that it meant the universe started as a concentrated cloud of galaxies. Others—including Canon Lemaitre, the Belgian priest-physicist—pictured the genesis of the universe as an explosion of some primordial “atom” of supercompressed matter. Only this past year, three American scientists described what may have happened during that explosion. Alpher, Bethe and Gamow (whose collaboration, Bethe has con- fessed to SI, was inspired by the pun their names made on the alpha, beta, and gamma rays of radium) even calculated that five minutes after the explosion started, the elements began to form from the separating matter; and about ten minutes later the whole process of building all the universe’s elements had been virtually completed.
It’s an exciting idea, even if a bit stiff for the average mortal mind to visualize. But, of course, the biggest question is entirely unanswered by it: How did the original “atom” get that way? What super-compressed it? And what set off the explosion that made the universe?
Others, such as the physicist Millikan and the Anglican clergyman-scientist, Bishop Barnes, avoided this problem by deciding that the expanding universe was really a pulsating universe. It expanded for a while, and then the forces became unbalanced and sent it back in the other direction. The conversion of matter into radiation, occurring in each star, and the re-creation in space of matter out of that radiation, could be connected with the forces that alternately expanded and contracted the universe.
As a minor matter of interest, if their theory were true, the galaxies might not now be running away from us at all. We think they are because we are looking at light which left them as much as 150 million or even 500 million years ago. In the meantime, the universe may have started back, and the galaxies may now be bearing down on us—or rather on each other—in a deflating-balloon effect. But we won’t be able to see this for millions of years.
It’s a striking notion. And it certainly by-passes the uncomfortable question of what caused the primal atom to explode into this universe. The universe, Barnes and Millikan might say, just always was. But there’s trouble even with this answer; the uranium which dates the earth and causes difficulties in the atom-explosion theory, causes the opposite kind of difficulties here. For a pulsating universe would be infinitely old; all the uranium would have long since broken down into helium and lead. The timetables are still out of order, somewhere.
Another try at escaping the whole mess was to explain the red shift as not even indicating expansion, but something else altogether. Einstein’s theories had shown that matter and energy are not different things, but different states of something basic. Matter could turn into energy—as in the stars or in the atom bomb—and back again. Consequently, when light passed through the gravitational field of a large star—or through an area of bent space, in the Einstein way of thinking—the light would be deflected or bent, just as though it had weight. This was proved in 1919 during an eclipse, when stars near the sun were shown to appear a little out of place.
Maybe and Perhaps Now if light traveling through space is held back a little by each particle of dust—and the great “empty” black spaces actually have vast quantities of such dust in them—then maybe the light would be gradually slowed down by the total gravitational force of all the dust. The farther it had come, the more dust it had passed through—and the slower it would be, and hence the more red shift it would show.
That could explain everything and do away with the expanding universe idea altogether. But who turns up to slaughter this excellent suggestion? Hubble, of course. For his calculations on the total amount of matter in space show that there just isn’t one hundredth the amount necessary to produce the red shift on this basis.
Wistfully, some bedraggled theorists have wondered if maybe light doesn’t just get “tired” while traveling through space and time. They don’t know why it should; they haven’t a scrap of evidence to prove that it ever does. But wouldn’t it be nice if it did? That could explain everything. But alas, there just isn’t anything to base this supposition on except wishful thinking.
Something Is Happening The mystery, therefore, remains. One thing is clear: There is undeniable evidence that something is happening. And perhaps the discrepancies and contradictions will disappear as scientists perfect their equipment and smooth out their theories. Almost every major astronomer in the world has said, or believes, that the new 200-inch telescope on Palomar, peering twice as far into space and seeing about eight times as much of the universe, will solve the mystery. It will look beyond to the faster-receding galaxies, it will look for more of the “bunching-up” effect, it will remeasure the curve of the universe, it will see if there are perhaps any great holes of truly empty space outside the present limits of observation, and it will make possible better calculations as to the rate and duration of the universe’s expansion.
And the answers to this great riddle should also answer the greatest questions man can ever ask: When and where did the universe begin, and when and how will it end?