Darling Deep Time

1. Auflage 2013
ISBN: 978-1-62287-322-7
Verlag: First Edition Design Publishing
Format: EPUB
Kopierschutz: Wasserzeichen (»Systemvoraussetzungen)

E-Book, Englisch, 100 Seiten

What would it be like to see the whole history of the universe, from the moment of creation to the farthest future? Deep Time shows us – through the eyes of a single particle that emerges from the fires of genesis then journeys across countless billions of years to glimpse the ultimate fate of the cosmos.

Autoren/Hrsg.

Darling, David

Leseproben

Chapter 3: Kinds of Flowers
  The most beautiful experience we have is the mysterious. It is the fundamental emotion that stands at the cradle of true art and true science. – Albert Einstein     Already fading are those strange, shifting impressions of Time Zero, those half-glimpsed images culled from the scientific lore of genesis. With a single instantaneous leap we have returned to a more familiar place: the one-second-old cosmos, with its thick, pervasive stew of protons, neutrons, electrons, photons, and neutrinos, simmering at ten billion degrees. From this point a new phase of our adventure begins. Inevitably, mysteriously, the path to the future winds away into the gray, misty distance. And even as we strain to see where it may lead, our particle hero, restored to its protonic form, approaches once more out of the bright chaos around. *** Urgently, unpredictably, our proton moves, as of old, from one brief encounter to the next. Rebounding from an electron, now from a fellow proton, it seems engaged in an endless, apparently aimless game of subatomic billiards. Not for the last time do we ponder the prospects for this mad jumble. And yet we recall, too, that the universe has already passed through a bewildering series of transformations – in a single second! So how much more might it not evolve in the billions upon billions of years to come? Still, factored in must be the rate of cosmic metamorphosis. And that now is noticeably on the wane. The next ten seconds bring no fresh revolution, no great new surprise. At the fifteen-second mark, though the temperature has dropped to a balmy three billion degrees, the particle mix remains the same. A full minute goes by. And more. So that, half seriously, we begin to doubt whether nature has any creative power left following the first frenetic second. Two minutes AG. Three minutes. (The doubt grows.) Three minutes 45 seconds AG: And now, as it has many times before, our proton draws near to another tiny islet of matter – a neutron – collides with it, and scatters. Yet, for a lingering instant, the proton and neutron remain attached. Like two drops of liquid that touch, the nucleons momentarily fuse. Only barely is the vigor of their impact enough to prevent the strong nuclear force – operating between the proton and neutron at close range – from binding the two particles permanently together. But even as our proton flies off, its independence narrowly preserved, the neutron from which it has just pulled free strikes another proton nearby. And this time there is no subsequent scattering. Instead, the neutron and its new partner remain tightly, securely bound together – as a nucleus of deuterium, or heavy hydrogen (H2). At last, it seems, the temperature has fallen sufficiently for this new stage of cosmic synthesis to begin. Alongside those most primitive of nuclei, the protons (the nuclei of ordinary hydrogen), small quantities of deuterium start to appear. And not only that. Some deuterium nuclei quickly go on to collide with and absorb an additional neutron and thereby change into tritium (H3), the heaviest form of hydrogen. Others, by chance, acquire an extra proton and so transmute into a lightweight variety of helium, helium 3. In either case the normal mode of helium is but a short step away. Tritium swallows a proton and becomes helium 4 (two protons plus two neutrons); helium 3 swallows a neutron and does the same. At three and three-quarter minutes AG vast quantities of helium 4 are being produced rapidly all over the universe. And yet therein lies a puzzle. For the fact is that helium 4 is sturdy enough to survive at temperatures of around three billion degrees. In other words, it was sufficiently cool much earlier, at only fifteen seconds AG, for ordinary helium to exist. Why then did it take so long to appear? The answer lies with the temperature stability of the middlemen: deuterium, tritium, and helium 3 – especially deuterium. Three billion degrees is still far too hot for these weaker-bound nuclei to hold together, so that they are simply blown apart the instant they form. Although the end product, helium 4 is stable at much higher temperatures, its formation is delayed by the more fragile nature of its intermediaries. Only as the temperature slides down to around 900 million degrees, at about 225 seconds, do deuterium and tritium and helium 3 each manage to cling together long enough for the final jump to helium 4 to occur. And then, quite suddenly, it happens: The universe is 10 percent helium, and the dramatic moment passes at which deuterium finally achieves stability. With the chain reaction process from individual neutrons and protons to helium 4 no longer chocked off at the second level (deuterium), virtually all the remaining free neutrons are gobbled up into helium nuclei. And our proton? Despite some close shaves, it has retained its liberty throughout this early phase of cosmic nucleosynthesis. Though one in ten of the nuclei around it are now of helium 4, almost all the remainder are free protons like itself. A tiny fraction endure as deuterium and helium 3 (though not as tritium, since this is radioactive and quickly breaks up). And there is a small but dwindling tribe of nomadic neutrons. Unlike the proton, the neutron cannot live indefinitely on its own. Bound up within a nucleus, it is secure. But alone, unattached, it must, as if it were a live grenade, quickly split apart – another strange idiosyncrasy of nature. Isolate any neutron at random and the chances are fifty-fifty that it will decay – into a proton, an electron, and an antineutrino – within just twelve minutes. Every 100 seconds from now on the remaining population of free neutrons will decline by 10 percent, until the only neutrons remaining will be those enclosed within nuclei. *** Four minutes after the Big Bang: Blindingly intense radiation bathes every corner of space. The photons swarm, 100 million of them for every proton and neutron. Electrons and their antiparticles, the positrons, continue their inevitable annihilation, until all the positrons have gone and the residual electrons are roughly equal in number to the protons. There are the ghostly neutrinos and antineutrinos. And, at the other extreme of materiality, there is this new, complex thing called helium. But why should the universe stop at the helium stage? Why not go on immediately to build still more complicated nuclei, perhaps those of carbon, oxygen, silicon, or even iron? The reason is the same as that for which the formation of helium 4 was delayed. Even when the final product was stable, certain intermediate nuclei – vital stepping-stones in the process of nucleosynthesis – were still highly unstable. Deuterium's temperature sensitivity caused the hold-up in helium 4 manufacture. Now, for anything heavier than helium, such as lithium 6, beryllium 9, boron 10, or carbon 12, it is the unstable nuclei with five and eight nuclear particles that are the stumbling block. Only in a very different environment, in the dense, central furnaces of stars-to-come, will nuclei more elaborate than helium be able to take shape. A half hour slips by. Our proton moves within a cosmos cooled to 300 million degrees – just fifteen times hotter than the core of the future sun. Less often now does it collide with other particles. The average density of matter has dropped to just one tenth that of water. Nucleosynthesis has come to a virtual standstill. And again there is apparent quiescence. Again, after a sudden, frenzied burst of change and synthesis, the anxious waiting for some new, unknown step toward greater cosmic complexity. Only this time the waiting seems longer – interminably long, even by human standards. Gone forever is the Golden Age of ultrafast transition, when the character of the whole universe could alter beyond recognition within the smallest fraction of a second, or within a few seconds, or a few minutes. An hour elapses. A day. A year. A thousand years! And, all the while, space relentlessly expands, stretching further the kinetic pattern on its multidimensional surface. The density of cosmic matter, along with its temperature, continues steadily to fall. And yet, apparently, there is no change in matter's quality. Ten thousand years go by. And even though our proton, like the countless other protons and heavier nuclei around it, often passes close to an electron, it forms no partnership with it. Even though the proton and electron have equal and opposite charge, and are therefore powerfully drawn to one another, they fail to come together in stable alliance. X-ray and ultraviolet photons – bullets of high-grade energy – strafe the fledgling cosmos, instantly stripping away any electrons that dare to enter bound states around a nucleus. Laser-intense, ubiquitous, the young electromagnetic field tears apart anything resembling an atom. And so, for millennia upon millennia, while the universe burns this bright, there is only a writhing, thinning, electrically charged mist – a plasma – of loose nuclei and electrons. Or so it had seemed. And yet there may be more to this young universe than simply a hot, spreading fog of particles and blazing light. For now the saga of our proton is beginning to take a strange new turn. And the prospect is slowly emerging that there may have been other things born of the Big Bang, bizarre, almost indescribable things, that have surreptitiously...