Universes

John Leslie

• Publisher: Routledge
• Year: 2002
• Print ISBN: 9780415041447
• eBook ISBN: 9781134770663
• Topic: Philosophy
• Subtopic: Philosophy History & Theory

Universes discusses the alleged evidence of fine tuning; mechanisms by which a varied set of Universes might be generated, and whether belief in God could be preferable to accepting universes in vast numbers.

Chapter One
World Ensemble, or Design

(i) Did God create a universe specially suited to life’s evolution? (ii) Alternatively, Do there exist vastly many universes with very varied properties, ours being one of a rare kind in which life occurs? (iii) Or again, May there be nothing too surprising in our universe’s life-containing character? (Perhaps more or less any universe would be life-containing, or perhaps there is some other ground for us to feel no surprise. Might we reason that if the cosmos weren’t life-containing then nobody would be around to ask whether to be astonished, and that this shows there is nothing to be astonished at?) The chapter introduces some main arguments in reaction to these, the book’s three main questions. ‘God or Multiverse’ is a phrase taken from Henry Adams.¹

God or Multiverse

1.1 The Argument from Design is an argument for God’s reality based on the fact that our universe looks much as if designed.

The Argument for Multiple Worlds starts from the same fact. But it concludes instead that there exist many small-u universes—Soviet cosmologists sometimes call them ‘metagalaxies’—inside the capital-U Universe which is The Whole of Reality.

These ‘universes’, ‘mini-universes’, ‘Worlds’ with a capital W to distinguish them from mere planets, can be of immense size. There may be immensely many of them. And their properties are thought of as very varied. Sooner or later, somewhere, one or more of them will have life-permitting properties. Our universe can indeed look as if designed. In reality, though, it may be merely the sort of thing to be expected sooner or later. Given sufficiently many years with a typewriter even a monkey would produce a sonnet.²

Suppose there existed ninety-seven trillion universes, all but three of them life-excluding. Obviously, only the three life-permitting universes could ever be observed by living beings. This suggests that an interesting kind of observational selection effect could underlie our seeing of a world whose conditions permit life to evolve. (Recognizing this is not the same as proposing paradoxically that the world is a causal consequence of human existence.)

1.2 While the Multiple Worlds (or World Ensemble) hypothesis is impressively strong, the God hypothesis is a viable alternative.

Rightly or wrongly, however, this book shows no interest in the kind of God who designs the structures of individual organisms, plague germs perhaps, or who interferes with Nature’s day-to-day operations. If God exists then of the various ways in which he may act on the universe there are only two which will be considered in these pages.

First, he makes the universe obey a particular set of laws (I prefer to think of them all as laws of physics), also ‘sustaining’ it in existence if this is necessary: recreating it, so to speak, from moment to moment, to prevent it from vanishing.

Second, he creates its initial state in such-and-such a fashion. He starts it off with this or that many particles in this or that arrangement; or at least he does this just so long as it has not been done already through his specifying what Nature’s laws are to be. It might be that the laws themselves dictated the number and arrangement of the particles.

If the universe has existed for ever, replace ‘creating its initial state’ by something like ‘deciding the number of its particles, and their arrangement at at least one time’.

1.3 Referring to God as ‘he’ or ‘him’ is just following convention. If God is real then his reality seems to me most likely to be as described by the Neoplatonist theological tradition. He is then not an almighty person but an abstract Creative Force which is ‘personal’ through being concerned with creating persons and acting as a benevolent person would.

To be more specific, Neoplatonism’s God is the world’s creative ethical requiredness. Or, which comes to the same thing, he is the creatively effective ethical requirement that there be a good universe or universes. Or again, he is the Principle that the ethical need for a universe or universes is itself responsible for the actual existence of that universe or those universes.³

However, it might instead be that God was a divine person creating everything else. Such a person might owe his existence and creative power to the fact that this was ethically required, a position suggested by the philosopher A.C.Ewing.

It is no insult to a divine person to suggest that he exists for that kind of reason. If anything, what would be uncomplimentary would be to call his existence utterly reasonless.

The Fine Tuning

1.4 This chapter introduces some of the book’s chief arguments. One is that it looks as if our universe is spectacularly ‘fine tuned for Life’.

By this I mean only that it looks as if small changes in this universe’s basic features would have made life’s evolution impossible. Thus talk of ‘fine tuning’ does not presuppose that a divine Fine Tuner, or Neoplatonism’s more abstract God, must be responsible.

In the modern cosmological literature you find many claims like the following. (More details of them and full references to the literature will be given in Chapter 2.)

• Large regions coming out of a Big Bang could be expected to be uncoordinated since not even influences travelling at the speed of light would have had time to link them. When they made contact tremendous turbulence would occur, yielding a cosmos of black holes or of temperatures which stopped galaxies forming for billions of years, after which everything would be much too spread out for them to form. Placing a pin to choose our orderly world from among the physically possible ones, God could seem to have been called on to aim with immense accuracy. Cosmologists refer to this as the Smoothness Problem.
• The cosmos threatened to recollapse within a fraction of a second or else to expand so fast that galaxy formation would be impossible. To avoid these disasters its rate of expansion at early instants needed to be fine tuned to perhaps one part in 10⁵⁵ (which is 10 followed by 54 zeros). That would make Space remarkably ‘flat’, so this is often called the Flatness Problem.
• Smoothness and Flatness Problems might be avoided through what is known as ‘Inflation’: after initial deceleration, a short burst of accelerating expansion at very early times could have increased the universe’s size by a factor of as much as 10^1,000,000. This could mean that everything now visible to us had grown from a region whose parts were originally well co-ordinated, which would give the observed smoothness. Also, a greatly expanded space might be very flat like the surface of a much inflated balloon.
  However, Inflation could itself seem to have required fine tuning for it to occur at all and for it to yield irregularities neither too small nor too great for galaxies to form. Thus, besides having to select a Grand Unified Theory (GUT) or Theory of Everything (TOE) very carefully, a deity wishing to bring about life-permitting conditions would seemingly need to have made two components of an expansion-driving ‘cosmological constant’ cancel each other with an accuracy better than of one part in 10⁵⁰. (‘Bare lambda’, the cosmological constant as originally proposed by Einstein, has to be in almost but not quite perfect balance with ‘quantum lambda’. With a balance that was perfect, Inflation would probably not occur.) A change by one part in 10¹⁰⁰ in the present strengths either of the nuclear weak force or of gravity might end this cancellation, disastrously.
• Had the nuclear weak force been appreciably stronger then the Big Bang would have burned all hydrogen to helium. There could then be neither water nor long-lived stable stars. Making it appreciably weaker would again have destroyed the hydrogen: the neutrons formed at early times would not have decayed into protons.
• Again, this force had to be chosen appropriately if neutrinos were to interact with stellar matter both weakly enough to escape from a supernova’s collapsing core and strongly enough to blast its outer layers into space so as to provide material for making planets.
• For carbon to be created in quantity inside stars the nuclear strong force must be to within perhaps as little as 1 per cent neither stronger nor weaker than it is. Increasing its strength by maybe 2 per cent would block the formation of protons—so that there could be no atoms—or else bind them into diprotons so that stars would burn some billion billion times faster than our sun. On the other hand decreasing it by roughly 5 per cent would unbind the deuteron, making stellar burning impossible. (Increasing Planck’s constant by over 15 per cent would be another way of preventing the deuteron’s existence. So would making the proton very slightly lighter or the neutron very slightly heavier, as it would then not be energetically advantageous for pairs of protons to become deuterons.)
• With electromagnetism very slightly stronger, stellar luminescence would fall sharply. Main sequence stars would then all of them be red stars: stars probably too cold to encourage Life’s evolution and at any rate unable to explode as the supernovae one needs for creating elements heavier than iron. Were it very slightly weaker then all main sequence stars would be very hot and short-lived blue stars.
  
  Again, a slight strengthening could transform all quarks (essential for constructing protons, and hence for all atoms) into leptons or else make protons repel one another strongly enough to prevent the existence of atoms even as light as those of helium. Again, strengthening by 1 per cent could have doubled the years needed for intelligent life to evolve, by making chemical changes more difficult. A doubled strength could have meant that 10⁶² years were needed—and in a much shorter time almost all protons would have decayed.
  Again, there is this. The electromagnetic fine structure constant gives the strength of the coupling between charged particles and electromagnetic fields. Increasing it to above 1/85 (from its present 1/137) could result in too many proton decays for there to be long-lived stars, let alone living beings who were not killed by their own radioactivity.
• The need for electromagnetism to be fine tuned if stars are not to be all of them red, or all of them blue, can be rephrased as a need for fine tuning of gravity because it is the ratio between the two forces which is crucial. Gravity also needs fine tuning for stars and planets to form, and for stars to burn stably over billions of years. It is roughly 10³⁹ times weaker than electromagnetism. Had it been only 10³³ times weaker, stars would be a billion times less massive and would burn a million times faster.
• Various particle masses had to take appropriate values for life of any plausible kind to stand a chance of evolving, (i) If the neutron-proton mass difference—about one part in a thousand—had not been almost exactly twice the electron’s mass then all neutrons would have decayed into protons or else all protons would have changed irreversibly into neutrons. Either way, there would not be the couple of hundred stable types of atom on which chemistry and biology are based, (ii) Superheavy particles were active early in the Bang. Fairly modest changes in their masses could have led to disastrous alterations in the ratio of matter particles to photons, giving a universe of black holes or else of matter too dilute to form galaxies. Further, the superheavies had to be very massive to prevent rapid decay of the proton, (iii) The intricacy of chemistry and the existence of solids depend on the electron’s being much less massive than the proton, (iv) The masses of a host of scalar particles could affect whether the cosmological constant would ever be the right size for Inflation to occur appropriately, and whether it would later be small enough to allow space to be very flat—failing which it would be expanding or contracting very violently. Today the constant is zero to one part in 10¹²⁰. (v) Forces can vary with range in seemingly very odd ways: the nuclear strong force, for instance, is repulsive at extremely short ranges while at slightly greater ones it is first attractive and then disappears entirely. The explanation for this lies in force ‘screening’ and ‘antiscreening’ and in how force-conveying ‘messenger particles’ can vanish before having had time to deliver their messages. These effects are crucially dependent on particle masses. The actual masses make forces enter into intricate checks and balances which underlie the comparatively stable behaviour of galaxies, stars, planets, and living organisms.

1.5 No doubt some of these claimed facts are mistakes—although many seem as well established as facts about the reality of quarks or black holes or neutron stars, or of the Big Bang itself. Others, again, may be dictated by physical principles so fundamental that they are not fine tunable. But clues heaped upon clues can constitute weighty evidence despite any doubts attaching to each element in the pile. Important, too, is that force strengths and particle masses are distributed across enormous ranges. The nuclear strong force is (roughly) a hundred times stronger than electromagnetism, which is in turn ten thousand times stronger than the nuclear weak force, which is itself some ten thousand billion billion billion times stronger than gravity. So we can well be impressed by any apparent need for a force to be ‘just right’ even to within a factor of ten, let alone to within one part in a hundred or in 10¹⁰⁰–especially when nobody is sure why the strongest force tugs any more powerfully than the weakest.

Ways of Getting a World Ensemble

1.6 As indicated earlier, one way of accounting for fine tuning of the world’s properties to suit Life’s needs would be suppose that there exists an ensemble of vastly many ‘Worlds’ or ‘universes’ with very varied properties. Ours would be one of the rare ones in which living beings could evolve. There is no need to say ‘infinitely many universes’ or ‘all possible universes’ instead of ‘vastly many’, although people often write as if this were essential. For a car number plate such as ‘LOOK 1234 WOW’ to be explained, rendered unmysterious, it can be enough that very numerous permutations of letters and numbers appear on cars. Again, a sufficiently mighty army of monkeys at typewriters could type a page of poetry unmysteriously without having to type infinitely many pages or all possible pages.

People have proposed a wide variety of mechanisms for generating multiple universes. Many such mechanisms will be discussed in detail in Chapter 4. They include these:

• The cosmos oscillates: Big Bang, Big Squeeze, Big Bang, and so on. As was suggested by J.A.Wheeler, each oscillation could count as a new World or (small-u) universe because of having new properties, or because the oscillations are separated by knotholes of intense compression in which information about previous cycles is lost—or in which Time breaks down entirely so that we cannot talk of other cycles as being ‘previous’.
• Many-Worlds quantum theory, originated by H.Everett III, is usually understood as giving us a capital-U Universe which branches into more and more Worlds that interact hardly at all. Each World represents one choice among the sets of events which quantum mechanics views as having been truly possible.
  Some people treat such branching as an offence against Simplicity. They prefer to regard Worlds other than our own as useful fictions at best. But various experiments—for instance, the double slit experiment in which we see what looks like interference between two separate sets of waves—seem to show that these supposed fictions are complexly active. The paths which particles might have taken appear able to affect in complex ways the paths which they actually take, setting up what looks like a ‘jostling’ of all the possibilities. It is then doubtful whether Simplicity is served by denying that the Worlds are all of them fully real.
• Worlds, small-u universes, could occur as quantum fluctuations, as was suggested by E.P.Tryon in 1973. Maybe such fluctuations would occur from time to time in a Superspace, although some have denied the need for any such already existing background.
  That an entire universe could occur as a fluctuation can seem absurd. In fact, however, it forms the basis of what is fast becoming the accepted account of how our universe began. Quantum fluctuations, in which particles spring into existence at unpredictable places and times, are happening constantly even in empty space. A fluctuation can be long-lasting if its energy is very small. And it is very ordinary physics to treat binding energies—for instance, the energy which binds an electron to a nucleus—as negative energies. Now, gravitational energy is binding energy, and our universe is richly supplied with it. It may be a universe having a total energy of zero or nearly zero when this is taken into account. Moreover even a small fluctuation could give birth to hugely much, because at very early times more and more new matter could spring into existence without ‘costing’ anything: its mass-energy could be exactly balanced by its gravitational energy.
• If Space is ‘open’ instead of being ‘closed’ like the surface of a sphere then on the most straightforward models it is infinitely large and contains infinitely much material. Gigantic regions situated far beyond our ‘particle horizon’ (the horizon set by how far light can have travelled to us since the Bang) could well be counted as ‘other universes’, particularly if their properties were very different.
• Even a ‘closed’ cosmos could be of any size, and the nowadays very popular Inflationary Cosmos is in fact gigantic. It is quite probably split into hugely many domains, markedly different in their properties. A.H.Guth and P.J.Steinhardt suggest that our own domain stretches 10²⁵ times further than we can see,⁴ so of course we can see none of the others.

1.7 Even granted ideal conditions, life might evolve only with great difficulty: its first beginnings could depend, for instance, on tremendously lucky molecular combinations in some primeval soup. If so, then multiple universes could help produce it by sheer force of numbers: toss fifty coins sufficiently often and some day the lot will land heads together. However, a multiplicity of universes could be all the more helpful if the universes varied widely, so making it more likely that conditions would somewhere be ideal. Now, modern Unifie...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Acknowledgements
• Chapter One: World Ensemble, or Design
• Chapter Two: The Evidence of Fine Tuning
• Chapter Three: Further Evidence
• Chapter Four: Multiple Worlds
• Chapter Five: The Need to Explain Life
• Chapter Six: Anthropic Explanations
• Chapter Seven: The Design Argument
• Chapter Eight: God
• Chapter Nine: Conclusions
• Notes
• References