1 HOW TO BUILD A UNIVERSENO MATTER
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A proton is an infinitesimal part of an atom, which is itself of course an insubstantial thing.
Protons are so small that a little dib of ink like the dot on this i can hold something in theregion of 500,000,000,000 of them, rather more than the number of seconds contained in halfa million years. So protons are exceedingly microscopic, to say the very least.
Now imagine if you can (and of course you can’t) shrinking one of those protons down to abillionth of its normal size into a space so small that it would make a proton look enormous.
Now pack into that tiny, tiny space about an ounce of matter. Excellent. You are ready to starta universe.
I’m assuming of course that you wish to build an inflationary universe. If you’d preferinstead to build a more old-fashioned, standard Big Bang universe, you’ll need additionalmaterials. In fact, you will need to gather up everything there is every last mote and particle ofmatter between here and the edge of creation and squeeze it into a spot so infinitesimallycompact that it has no dimensions at all. It is known as a singularity.
In either case, get ready for a really big bang. Naturally, you will wish to retire to a safeplace to observe the spectacle. Unfortunately, there is nowhere to retire to because outside thesingularity there is no where. When the universe begins to expand, it won’t be spreading outto fill a larger emptiness. The only space that exists is the space it creates as it goes.
It is natural but wrong to visualize the singularity as a kind of pregnant dot hanging in adark, boundless void. But there is no space, no darkness. The singularity has no “around”
around it. There is no space for it to occupy, no place for it to be. We can’t even ask how longit has been there—whether it has just lately popped into being, like a good idea, or whether ithas been there forever, quietly awaiting the right moment. Time doesn’t exist. There is no pastfor it to emerge from.
And so, from nothing, our universe begins.
In a single blinding pulse, a moment of glory much too swift and expansive for any form ofwords, the singularity assumes heavenly dimensions, space beyond conception. In the firstlively second (a second that many cosmologists will devote careers to shaving into ever-finerwafers) is produced gravity and the other forces that govern physics. In less than a minute theuniverse is a million billion miles across and growing fast. There is a lot of heat now, tenbillion degrees of it, enough to begin the nuclear reactions that create the lighter elements—principally hydrogen and helium, with a dash (about one atom in a hundred million) oflithium. In three minutes, 98 percent of all the matter there is or will ever be has beenproduced. We have a universe. It is a place of the most wondrous and gratifying possibility,and beautiful, too. And it was all done in about the time it takes to make a sandwich.
When this moment happened is a matter of some debate. Cosmologists have long arguedover whether the moment of creation was 10 billion years ago or twice that or something inbetween. The consensus seems to be heading for a figure of about 13.7 billion years, but thesethings are notoriously difficult to measure, as we shall see further on. All that can really besaid is that at some indeterminate point in the very distant past, for reasons unknown, therecame the moment known to science as t = 0. We were on our way.
There is of course a great deal we don’t know, and much of what we think we know wehaven’t known, or thought we’ve known, for long. Even the notion of the Big Bang is quite arecent one. The idea had been kicking around since the 1920s, when Georges Lema?tre, aBelgian priest-scholar, first tentatively proposed it, but it didn’t really become an activenotion in cosmology until the mid-1960s when two young radio astronomers made anextraordinary and inadvertent discovery.
Their names were Arno Penzias and Robert Wilson. In 1965, they were trying to make useof a large communications antenna owned by Bell Laboratories at Holmdel, New Jersey, butthey were troubled by a persistent background noise—a steady, steamy hiss that made anyexperimental work impossible. The noise was unrelenting and unfocused. It came from everypoint in the sky, day and night, through every season. For a year the young astronomers dideverything they could think of to track down and eliminate the noise. They tested everyelectrical system. They rebuilt instruments, checked circuits, wiggled wires, dusted plugs.
They climbed into the dish and placed duct tape over every seam and rivet. They climbedback into the dish with brooms and scrubbing brushes and carefully swept it clean of whatthey referred to in a later paper as “white dielectric material,” or what is known morecommonly as bird shit. Nothing they tried worked.
Unknown to them, just thirty miles away at Princeton University, a team of scientists led byRobert Dicke was working on how to find the very thing they were trying so diligently to getrid of. The Princeton researchers were pursuing an idea that had been suggested in the 1940sby the Russian-born astrophysicist George Gamow that if you looked deep enough into spaceyou should find some cosmic background radiation left over from the Big Bang. Gamowcalculated that by the time it crossed the vastness of the cosmos, the radiation would reachEarth in the form of microwaves. In a more recent paper he had even suggested an instrumentthat might do the job: the Bell antenna at Holmdel. Unfortunately, neither Penzias andWilson, nor any of the Princeton team, had read Gamow’s paper.
The noise that Penzias and Wilson were hearing was, of course, the noise that Gamow hadpostulated. They had found the edge of the universe, or at least the visible part of it, 90 billiontrillion miles away. They were “seeing” the first photons—the most ancient light in theuniverse—though time and distance had converted them to microwaves, just as Gamow hadpredicted. In his book The Inflationary Universe , Alan Guth provides an analogy that helps toput this finding in perspective. If you think of peering into the depths of the universe as likelooking down from the hundredth floor of the Empire State Building (with the hundredth floorrepresenting now and street level representing the moment of the Big Bang), at the time ofWilson and Penzias’s discovery the most distant galaxies anyone had ever detected were onabout the sixtieth floor, and the most distant things—quasars—were on about the twentieth.
Penzias and Wilson’s finding pushed our acquaintance with the visible universe to within halfan inch of the sidewalk.
Still unaware of what caused the noise, Wilson and Penzias phoned Dicke at Princeton anddescribed their problem to him in the hope that he might suggest a solution. Dicke realized at once what the two young men had found. “Well, boys, we’ve just been scooped,” he told hiscolleagues as he hung up the phone.
Soon afterward the Astrophysical Journal published two articles: one by Penzias andWilson describing their experience with the hiss, the other by Dicke’s team explaining itsnature. Although Penzias and Wilson had not been looking for cosmic background radiation,didn’t know what it was when they had found it, and hadn’t described or interpreted itscharacter in any paper, they received the 1978 Nobel Prize in physics. The Princetonresearchers got only sympathy. According to Dennis Overbye in Lonely Hearts of the Cosmos, neither Penzias nor Wilson altogether understood the significance of what they had founduntil they read about it in the New York Times .
Incidentally, disturbance from cosmic background radiation is something we have allexperienced. Tune your television to any channel it doesn’t receive, and about 1 percent of thedancing static you see is accounted for by this ancient remnant of the Big Bang. The next timeyou complain that there is nothing on, remember that you can always watch the birth of theuniverse.
Although everyone calls it the Big Bang, many books caution us not to think of it as anexplosion in the conventional sense. It was, rather, a vast, sudden expansion on a whoppingscale. So what caused it?
One notion is that perhaps the singularity was the relic of an earlier, collapsed universe—that we’re just one of an eternal cycle of expanding and collapsing universes, like the bladderon an oxygen machine. Others attribute the Big Bang to what they call “a false vacuum” or “ascalar field” or “vacuum energy”—some quality or thing, at any rate, that introduced ameasure of instability into the nothingness that was. It seems impossible that you could getsomething from nothing, but the fact that once there was nothing and now there is a universeis evident proof that you can. It may be that our universe is merely part of many largeruniverses, some in different dimensions, and that Big Bangs are going on all the time all overthe place. Or it may be that space and time had some other forms altogether before the BigBang—forms too alien for us to imagine—and that the Big Bang represents some sort oftransition phase, where the universe went from a form we can’t understand to one we almostcan. “These are very close to religious questions,” Dr. Andrei Linde, a cosmologist atStanford, told the New York Times in 2001.
The Big Bang theory isn’t about the bang itself but about what happened after the bang.
Not long after, mind you. By doing a lot of math and watching carefully what goes on inparticle accelerators, scientists believe they can look back to 10-43seconds after the moment ofcreation, when the universe was still so small that you would have needed a microscope tofind it. We mustn’t swoon over every extraordinary number that comes before us, but it isperhaps worth latching on to one from time to time just to be reminded of their ungraspableand amazing breadth. Thus 10-43is 0.0000000000000000000000000000000000000000001, orone 10 million trillion trillion trillionths of a second.
**A word on scientific notation: Since very large numbers are cumbersome to write and nearly impossible to read, scientistsuse a shorthand involving powers (or multiples) of ten in which, for instance, 10,000,000,000 is written 1010 and 6,500,000becomes 6.5 x 106. The principle is based very simply on multiples of ten: 10 x 10 (or 100) becomes 102; 10 x 10 x 10 (or1,000) is 103; and so on, obviously and indefinitely. The little superscript number signifies the number of zeroes followingthe larger principal number. Negative notations provide latter in print (especially essentially a mirror image, with thesuperscript number indicating the number of spaces to the right of the decimal point (so 10-4 means 0.0001). Though I salutethe principle, it remains an amazement to me that anyone seeing "1.4 x 109 km3’ would see at once that that signifies 1.4 Most of what we know, or believe we know, about the early moments of the universe isthanks to an idea called inflation theory first propounded in 1979 by a junior particlephysicist, then at Stanford, now at MIT, named Alan Guth. He was thirty-two years old and,by his own admission, had never done anything much before. He would probably never havehad his great theory except that he happened to attend a lecture on the Big Bang given bynone other than Robert Dicke. The lecture inspired Guth to take an interest in cosmology, andin particular in the birth of the universe.
The eventual result was the inflation theory, which holds that a fraction of a moment afterthe dawn of creation, the universe underwent a sudden dramatic expansion. It inflated—ineffect ran away with itself, doubling in size every 10-34seconds. The whole episode may havelasted no more than 10-30seconds—that’s one million million million million millionths of asecond—but it changed the universe from something you could hold in your hand tosomething at least 10,000,000,000,000,000,000,000,000 times bigger. Inflation theoryexplains the ripples and eddies that make our universe possible. Without it, there would be noclumps of matter and thus no stars, just drifting gas and everlasting darkness.
According to Guth’s theory, at one ten-millionth of a trillionth of a trillionth of a trillionthof a second, gravity emerged. After another ludicrously brief interval it was joined byelectromagnetism and the strong and weak nuclear forces—the stuff of physics. These werejoined an instant later by swarms of elementary particles—the stuff of stuff. From nothing atall, suddenly there were swarms of photons, protons, electrons, neutrons, and much else—between 1079and 1089of each, according to the standard Big Bang theory.
Such quantities are of course ungraspable. It is enough to know that in a single crackinginstant we were endowed with a universe that was vast—at least a hundred billion light-yearsacross, according to the theory, but possibly any size up to infinite—and perfectly arrayed forthe creation of stars, galaxies, and other complex systems.
What is extraordinary from our point of view is how well it turned out for us. If theuniverse had formed just a tiny bit differently—if gravity were fractionally stronger orweaker, if the expansion had proceeded just a little more slowly or swiftly—then there mightnever have been stable elements to make you and me and the ground we stand on. Had gravitybeen a trifle stronger, the universe itself might have collapsed like a badly erected tent,without precisely the right values to give it the right dimensions and density and componentparts. Had it been weaker, however, nothing would have coalesced. The universe would haveremained forever a dull, scattered void.
This is one reason that some experts believe there may have been many other big bangs,perhaps trillions and trillions of them, spread through the mighty span of eternity, and that thereason we exist in this particular one is that this is one we could exist in. As Edward P. Tryonof Columbia University once put it: “In answer to the question of why it happened, I offer themodest proposal that our Universe is simply one of those things which happen from time tobillion cubic kilometers, and no less a wonder that they would choose the former over the in a book designed for the generalreader, where the example was found). On the assumption that many general readers are as unmathematical as I am, I will usethem sparingly, though they are occasionally unavoidable, not least in a chapter dealing with things on a cosmic scale.
time.” To which adds Guth: “Although the creation of a universe might be very unlikely,Tryon emphasized that no one had counted the failed attempts.”
Martin Rees, Britain’s astronomer royal, believes that there are many universes, possibly aninfinite number, each with different attributes, in different combinations, and that we simplylive in one that combines things in the way that allows us to exist. He makes an analogy witha very large clothing store: “If there is a large stock of clothing, you’re not surprised to find asuit that fits. If there are many universes, each governed by a differing set of numbers, therewill be one where there is a particular set of numbers suitable to life. We are in that one.”
Rees maintains that six numbers in particular govern our universe, and that if any of thesevalues were changed even very slightly things could not be as they are. For example, for theuniverse to exist as it does requires that hydrogen be converted to helium in a precise butcomparatively stately manner—specifically, in a way that converts seven one-thousandths ofits mass to energy. Lower that value very slightly—from 0.007 percent to 0.006 percent,say—and no transformation could take place: the universe would consist of hydrogen andnothing else. Raise the value very slightly—to 0.008 percent—and bonding would be sowildly prolific that the hydrogen would long since have been exhausted. In either case, withthe slightest tweaking of the numbers the universe as we know and need it would not be here.
I should say that everything is just right so far. In the long term, gravity may turn out to be alittle too strong, and one day it may halt the expansion of the universe and bring it collapsingin upon itself, till it crushes itself down into another singularity, possibly to start the wholeprocess over again. On the other hand it may be too weak and the universe will keep racingaway forever until everything is so far apart that there is no chance of material interactions, sothat the universe becomes a place that is inert and dead, but very roomy. The third option isthat gravity is just right—“critical density” is the cosmologists’ term for it—and that it willhold the universe together at just the right dimensions to allow things to go on indefinitely.
Cosmologists in their lighter moments sometimes call this the Goldilocks effect—thateverything is just right. (For the record, these three possible universes are known respectivelyas closed, open, and flat.)Now the question that has occurred to all of us at some point is: what would happen if youtraveled out to the edge of the universe and, as it were, put your head through the curtains?
Where would your head be if it were no longer in the universe? What would you find beyond?
The answer, disappointingly, is that you can never get to the edge of the universe. That’s notbecause it would take too long to get there—though of course it would—but because even ifyou traveled outward and outward in a straight line, indefinitely and pugnaciously, you wouldnever arrive at an outer boundary. Instead, you would come back to where you began (atwhich point, presumably, you would rather lose heart in the exercise and give up). The reasonfor this is that the universe bends, in a way we can’t adequately imagine, in conformance withEinstein’s theory of relativity (which we will get to in due course). For the moment it isenough to know that we are not adrift in some large, ever-expanding bubble. Rather, spacecurves, in a way that allows it to be boundless but finite. Space cannot even properly be saidto be expanding because, as the physicist and Nobel laureate Steven Weinberg notes, “solar systems and galaxies are not expanding, and space itself is not expanding.” Rather, thegalaxies are rushing apart. It is all something of a challenge to intuition. Or as the biologist J.
B. S. Haldane once famously observed: “The universe is not only queerer than we suppose; itis queerer than we can suppose.”
The analogy that is usually given for explaining the curvature of space is to try to imaginesomeone from a universe of flat surfaces, who had never seen a sphere, being brought toEarth. No matter how far he roamed across the planet’s surface, he would never find an edge.
He might eventually return to the spot where he had started, and would of course be utterlyconfounded to explain how that had happened. Well, we are in the same position in space asour puzzled flatlander, only we are flummoxed by a higher dimension.
Just as there is no place where you can find the edge of the universe, so there is no placewhere you can stand at the center and say: “This is where it all began. This is the centermostpoint of it all.” We are all at the center of it all. Actually, we don’t know that for sure; wecan’t prove it mathematically. Scientists just assume that we can’t really be the center of theuniverse—think what that would imply—but that the phenomenon must be the same for allobservers in all places. Still, we don’t actually know.
For us, the universe goes only as far as light has traveled in the billions of years since theuniverse was formed. This visible universe—the universe we know and can talk about—is amillion million million million (that’s 1,000,000,000,000,000,000,000,000) miles across. Butaccording to most theories the universe at large—the meta-universe, as it is sometimescalled—is vastly roomier still. According to Rees, the number of light-years to the edge ofthis larger, unseen universe would be written not “with ten zeroes, not even with a hundred,but with millions.” In short, there’s more space than you can imagine already without going tothe trouble of trying to envision some additional beyond.
For a long time the Big Bang theory had one gaping hole that troubled a lot of people—namely that it couldn’t begin to explain how we got here. Although 98 percent of all thematter that exists was created with the Big Bang, that matter consisted exclusively of lightgases: the helium, hydrogen, and lithium that we mentioned earlier. Not one particle of theheavy stuff so vital to our own being—carbon, nitrogen, oxygen, and all the rest—emergedfrom the gaseous brew of creation. But—and here’s the troubling point—to forge these heavyelements, you need the kind of heat and energy of a Big Bang. Yet there has been only oneBig Bang and it didn’t produce them. So where did they come from?
Interestingly, the man who found the answer to that question was a cosmologist whoheartily despised the Big Bang as a theory and coined the term “Big Bang” sarcastically, as away of mocking it. We’ll get to him shortly, but before we turn to the question of how we gothere, it might be worth ta