Dancing With Myself
Page 41
The Big Crunch could happen as “soon” as 50 billion years from now, depending on how much the mass-energy exceeds the critical amount. We think we know from observation that the mass-energy density is not more than twice the critical density. That would mean we face about 20 billion more years of expansion, followed by at least 30 billion years of collapse.
Does this mean that life cannot in this case go on forever?
Yes and no. Life cannot survive the Big Crunch. Thus if we continue to measure time in the usual way, life therefore exists for a finite time only. However, it can be shown that there is enough time (and available energy) between now and the Big Crunch to think an infinite number of thoughts. From that point of view, if we work with subjective time then life can survive long enough to enjoy infinite numbers of thoughts—“forever” according to one reasonable definition. It is all a question of re-defining our time coordinates, as we did earlier.
Suppose, however, that the universe is forever expanding, or tends to final flatness. It can still be shown that an infinite number of thoughts can be thought. Curiously enough, in an ultimately flat universe an infinite number of thoughts can be thought with the use of only a finite amount of energy! That’s just as well, because in such a universe, energy becomes less and less easy to come by as time goes on.
Freeman Dyson analyzed the expanding universe situation in detail in 1979, and found that although thoughts can go on into the far future they have to proceed more and more slowly. No more “lightning flashes of wit.” Instead it will all be Andrew Marvell’s: “My vegetable love should grow, vaster than empires and more slow.” All thought must be “cool calculation.”
Meanwhile, such thought goes on against the background of an expanding universe that is radically (but slowly) changing. First, all ordinary stellar activity, even of the latest-formed and smallest suns, will end. That will be somewhat less than a million billion (say, 1014) years in the future.
After that it is quiet for a while, because everything is tied up in stellar leftovers, neutron stars and black holes and cold dwarf stars.
Then the protons in the universe begin to decay and vanish.
That requires a word of explanation. A generation ago, the proton was thought to be an eternally stable particle, quite unlike its cousin, the unstable free neutron. Then a class of theories came along that said that protons too may be unstable, but with a vastly long lifetime. If these theories are correct, the proton has a finite lifetime of at least 1032 years. In this case, as the protons decay all the stars will finally become black holes.
The effect of proton decay is slow. It takes somewhere between 1030 and 1036 years for the stellar remnants all to become black holes. Note that on this time scale, everything that has happened in the universe so far is totally negligible, a tick at the very beginning. The ratio of the present age of the universe to 1036 years is like a few nanoseconds (1 nanosecond = 10-9 seconds) compared with the present age of the universe.
Long after the protons are all gone, the black holes go, too. Black holes evaporate, according to a theory developed by Stephen Hawking, because they have an effective temperature, and quantum theory allows them to radiate to an environment of lower temperature. Today, the universe is far too hot for a black hole of stellar mass to be able to lose mass by radiation and particle production. In another 1064 years or so, that will not be true. The ambient temperature of the expanding universe will have dropped and dropped, and the black holes will evaporate. Those smaller than the Sun in mass will go first, ones larger than the Sun will go later; but eventually all will go.
In this scenario, the universe, some 1080 years from now, will be an expanding ocean of radiation.
Not everyone accepts the idea of proton decay, so we must consider the alternative. Suppose, then, that the proton is not an unstable particle. Then we have a rather different (and longer) future for the universe of material objects.
All the stars will continue, very slowly, to change their composition to the element with the most nuclear binding energy: iron. They will be doing this after some 101600 years.
Finally (though it is not the end, because there is no end) after somewhere between 10 to the 1026 and 10 to the 1076 years,14 a time so long that I can find no analogy to offer a feel for it, our solid iron neutron stars will become black holes.
Is this the end of the road? No. The black holes themselves will disappear, quickly (on these times scales) evaporating to radiation. The whole universe, as in the previous scenario, becomes at last pure radiation. This all-encompassing bath, feeble and far-diluted, is much too weak to permit the formation of particles. So in our distant future, radiation is all.
Or nearly all. Still, by careful use of the tiny amounts of energy available, it is possible that some few corporeal bodies may be preserved, and some form of memory, thought, and intelligence may endure.
There it is, the Universe, as far ahead as we can see or imagine.
How good is this long-term projection? Well, the events and the times are as good as today’s science can offer. But why do I keep thinking of Archbishop Ussher, and 4004 B.C.?
10.FAR-OUT THINKING
Some readers may still be feeling that I have not made good on my promise of Section 1, where I said I would offer “amazing new revelations.” All right then. Try this:
The existence of God depends on the existence of a sufficient amount of missing matter in the universe.
That ought to be amazing enough for anyone. Yet it is proposed, as a quite serious physical theory, by Frank Tipler. I’m going to butcher his argument when I offer it in brief summary, but anyone who wants the full development can find it in Tipler’s paper: “The Omega Point as Eschaton: Answers to Pannenberg’s Questions for Scientists,” published in Zygon, Volume 24 (June 1989). I don’t think you will find the word “eschaton” in a standard dictionary, but it means the final state of all things, and therefore includes the final state of the universe.
Tipler argues that only certain types of possible universes allow a physicist to deduce (he says prove) the existence of a God with the powers of omnipresence, omniscience, and omnipotence. The key ideas are that:
(1) the universe must be such that life can continue for infinite (subjective) time,
(2) spacetime, continued into the future, must have as a boundary a particular type of termination, known as a c-boundary, and
(3) the necessary c-boundary must consist of a single point of space-time.
Then, and only then, according to Tipler, God with omnipresence, omniscience, and omnipotence can be shown to exist. I will not try to reproduce his logic, which is difficult but not implausible. I will only point out that his arguments require that the universe be closed. It cannot be expanding forever, or even asymptotically flat, otherwise his theories will not work.
But as we saw in Section 6, there is not enough visible matter to close the universe. Even if we throw in the invisible matter that seems to control the galaxies gravitationally, we are still short by a factor of five to ten.
In Section 6, the question of the missing matter and the closed or open universe seemed like an interesting one, but not one that could say anything about religion. Now Tipler has raised the stakes. He argues that the existence of a God, including the concepts of resurrection, eternal grace, and eternal life, depends crucially on the current mass-energy density of the universe.
We saw, earlier in this article, the curious way in which observation of the remote patches of haze known as nebulas showed that the universe began a finite time ago. That was a striking conclusion: simple observations today decided the far past of the universe.
I leave you with a far stranger notion to contemplate: The search for and measurement of “hot” neutrinos and “cold” photinos and axions tell us about the far future of the universe; and those same measurements may have application not only to physics, but possibly to
theology.
11.SOME READING
Gamow, G. Thirty Years That Shook Physics. Dover reprint of Doubleday text, 1966.
Gribbin, J. In Search of the Big Bang. Bantam Books, 1986. The most complete popular work around on this subject, and the most readable. What more can I say, except perhaps that I go to this book (and borrow from it) early and often?
Gribbin, J., and M. Rees. Cosmic Coincidences. Black Swan Press, 1991. This is an English edition, and I don’t know if there is an American one. Just to complicate life further, the book was first published in 1990, by Heinemann, with a different title: The Stuff of the Universe. This book tackles the problems of the origin and large-scale structure of the universe with hair-raising panache.
Weinberg, S. The First Three Minutes. Basic Books, 1977. This was the first book to tackle the early history of the universe for a broad audience. Although fourteen years old, the material in it is still valuable and informative.
Kippenhahn, R. 100 Billion Suns. Basic Books, 1983. Originally published in German in 1980. Kippenhahn spent his life in the middle of stellar evolution research, and his book shows the realism and recognition of difficulties of one “who was there?”
Mitton, S. Exploring the Galaxies. Scribner, 1976. This book, because it describes the galaxies more than their origins, has dated very little although it is fifteen years old. The author refuses to talk down to the audience, uses “boring detail” and equations when they are necessary, and is to be commended for it.
Eiseley, L. Darwin’s Century. Doubleday, 1958. A relatively old book, but since it is describing events that happened a century or more earlier, that doesn’t really matter. Great coverage of the Darwin and Kelvin argument on the age of the Earth and Sun; beautifully written, too.
Barrow, J.D., and F.J. Tipler. The Anthropic Cosmological Principle. Oxford University Press, 1986. Tipler is the foremost advocate of the “We are alone” school, and he is thus at odds with all the SETI (Search for Extraterrestrial Intelligence) believers. Tipler says, and this book argues at length (you might say extreme length—it’s over 700 pages) that humans are probably the only intelligent species in the universe; and in the long run we and our descendants (who will probably not be flesh and blood, but our descendants nonetheless) will take over the universe.
Tipler, F.J. “The Omega Point as Eschaton: Answers to Pannenberg’s Questions for Scientists.” Zygon, Volume 24 (June 1989). Seeks to prove the existence of God by arguments drawn from today’s physical theories. I break my usual rule and include an article (and one that is not easy to find) simply because I know of no reference to it in a book. This is also the perfect choice for a final reference.
* * *
1It is awkward to express very large or very small numbers without using scientific notation. In such notation, the number written as, for example, 1036 stands for 1 followed by 36 zeros, i.e., a million million million million million million. The number 10-36 is one divided by that. I will usually employ scientific notation for any number more than one billion (109) or less than one-billionth (10-9).
2Termed states in the vocabulary of quantum theory; any possible unique situation in a system forms one state.
3Einstein, writing in 1926 of Dirac, whom he came to admire greatly, said, “I have trouble with Dirac. This balancing on the dizzying path between genius and madness is awful.”
4This idea has been challenged recently by Roger Penrose, in his book, The Emperor’s New Mind. See the final section.
5Why a comet, and not an asteroidal meteorite? Because no metallic or stony fragments were found at the scene of the impact.
6“I could more easily believe that two Yankee professors would lie than that stones would fall from heaven.”—Thomas Jefferson
7The Sun has actually been getting brighter. Over the past three and a half billion years it is estimated to have increased in energy production by 30 percent.
8I say shines, rather than appears to shine, because the brightness of the stars we see depends on how far away they are. The absolute magnitude of a star means its brightness as it would appear from a standard distance. The mass-luminosity law works in terms of the absolute magnitude.
9So after 26 minutes, three neutrons out of four will have decayed; after 39 minutes, seven out of eight, and so on. You might think that would mean that neutrons ought to have disappeared early in the history of the universe. However, that rapid decay only happens to isolated neutrons. Bound inside a nucleus a neutron is quite stable, and most elements have more neutrons inside the nucleus than they have protons.
10This is a little bit of an overstatement. Actually, a smidgeon of deuterium and lithium can be produced, too, but not enough to make a difference.
11Subrahmanyan Chandrasekhar, one of the great men of modern astrophysics, did his first analysis of white dwarf structure in 1930, on the ship that took him from India to England. He shared the 1983 Nobel Prize for physics (with William Fowler) for his work on stellar structure.
12“Super-rapid” is an appropriate description, because during the inflation period the universe was expanding in size millions of times faster than the speed of light.
13Specifically, between the fermions, particles such as protons, neutrons, and electrons, and the bosons, particles such as phssotons.
14We have raised the stakes again. 10 to the 1026 is the number 1 followed by 1026 zeros. The possible future is not just longer than the past. It is unimaginably longer. To my knowledge, nothing in physics involves numbers as large as the possible future of the universe.
Table of Contents
Copyright
Contents
Introduction
Story: Out of Copyright
Story: Tunicate, Tunicate, Wilt Thou be Mine?
Article: Counting Up
Story: A Braver Thing
Story: The Grand Tour
Article: Classical Nightmares…and Quantum Paradoxes
Story: Nightmares of the Classical Mind
Story: The Double Spiral Staircase
Article: The Unlicked Bear-Whelp
Story: The Seventeen-Year Locusts
Story: The Courts of Xanadu
Story: C-Change
Article: Unclear Winter
Story: Godspeed
Story: Dancing With Myself
Article: Something for Nothing
Landmarks
Cover