The Forbidden Universe (31 page)

In practice, however, the presence of vacuum energy was not considered too important – at least until the 1990s. The rate of expansion was believed to be constant, neither
accelerating nor decelerating, which meant that the vacuum energy played no part in the process. This, in turn, meant it must have a net value of zero – that is, all the energy in the vacuum was neatly balanced, the positive and negative particles cancelling each other out. Cosmologists had no idea why, but that’s what the data suggested.

But in the mid-1990s this happy state of affairs suffered a major jolt, as independent research based on new, more accurate data from sources such as the Hubble Space Telescope showed that the rate of expansion is, in fact, speeding up. This means that the vacuum energy has a slight positive value, not all of which is cancelled out by the negative. It is only a tiny imbalance: calculations showed that the positive energy value is 10
¹²⁰
times (that’s 119 zeroes after the decimal point before you even get to the 1) less than the total positive energy in the vacuum. In other words, the negative energy cancels out all the positive – apart from a minute portion.

Learned jaws were on the ground yet again when it was realized that if that value was just one decimal place shorter – that is, the actual positive energy was 10
¹¹⁹
times less than the total (or 118 zeroes after the decimal point and before the 1) – then the universe as we know it simply couldn’t exist. It would expand too quickly for galaxies, stars or planets to form. Referring to this as the ‘biggest fix in the universe’, Davies points out that this tiny difference – a point between the 119
^th
and 120
^th
decimal place – is the thinness of the knife edge on which all life is balanced.
¹⁴
In answer to the dilemma posed by this ‘staggeringly precise’ balancing of the vacuum energy, Leonard Susskind writes: ‘This seems like an absurd accident and we have no idea why it should happen. There is no fine-tuning quite like this in the rest of physics.’
¹⁵

However, while acknowledging that there is no viable alternative to an ‘anthropic explanation’,
¹⁶
Susskind does
not imply the existence of a ‘grand designer’. For him this phenomenon can only be explained by whatever is behind the anthropic effect as a whole, which to the conventional scientist means the
illusion
of design. For Susskind, however, as for many scientists, there is only one solution to the conundrum: the marvellous and all-encompassing notion of ‘multiverse’.

According to the fans of this fashionable hypothesis, there are millions or billions, perhaps an infinite number, of universes, co-existing invisibly alongside our own, each governed by its own laws of physics. We just happen to live in one that happens to be bio-friendly. It may appear to have been custom-made for us, but as this universe is, by definition, one that will sustain our sort of life and the only one we can perceive, this is the only one we know about.

The multiverse is a concept that turns the virtually impossible into the almost inevitable. To use the lottery analogy again, if your ticket automatically entered you into several million draws simultaneously, it would hardly be surprising if your numbers came up somewhere. The same logic dictates that by positing millions upon millions of universes, the odds that at least one would boast the right conditions for life are drastically shortened.

The multiverse theory is the only alternative to design that remains within the bounds of scientific credibility and allows the anthropic conundrum to be debated without professional anxiety. Bernard Carr explains that physicists regard the multiverse hypothesis as the ‘legitimization’
¹⁷
of the anthropic principle.

However, unfortunately for its many scientific fans, there are major problems with the multiverse. First, and surely the most damning, is that it is purely a theory with not a shred of solid data to back it up. There are three basic,
competing models of the genesis of multiple universes that may keep physicists agog with debate and busy
formulating
mathematical models of how they might work, but this seems a hollow exercise as none of the models have the remotest hope of ever being proved. In fact, it is impossible to gather evidence because interaction between universes is by definition also impossible.

On the other hand, multiverse theory can be used to predict certain features of
this
universe. But as American theoretical physicist Lee Smolin, founder of the Perimeter Institute for Theoretical Physics in Ontario, Canada, notes:

The theory also violates another highly-prized scientific principle, Occam’s razor, expressed by the great
twentieth-century
physicist Sir James Jeans as, ‘We must not assume the existence of any entity until we are compelled to do so’,
¹⁹
or, in other words, the simplest explanation is usually the best. As Paul Davies wryly comments: ‘To invoke an infinity of other universes to explain one is surely carrying excess baggage to cosmic extremes.’
²⁰

The complete absence of evidence does not justify the extraordinary confidence with which the multiverse is promoted as a solution to the anthropic conundrum. In a 2008 radio discussion, British theoretical physicist Fay Dowker stated that ‘the existence of the multiverse, if we can establish it, would eliminate the question of why the
laws of nature are the way we see them’.
²¹
If
we can establish it …

In the introduction to
Universe or Multiverse?
(2007), Carr acknowledges that the multiverse hypothesis:

He goes on:

In recent years the multiverse theory has become inextricably bound up with two others: string theory and the related M-theory. These are now locked in a symbiotic – indeed circular – relationship. To put it baldly, one is taken as proof of the other. Unfortunately, however, both the string and M-theories suffer from the same problems as the multiverse. And a growing chorus of physicists are volubly expressing doubts about their validity and whether, despite all the time, effort and often almost hysterical enthusiasm devoted to them, they are nothing more than a complete dead end. One of the most withering attacks on string theory came in 2006 from Lee Smolin in his book
The Trouble with Physics
.

String theory – often called ‘superstring theory’ in a rather pitiable attempt to make it sound sexier – posits that instead of being single points, subatomic particles are all manifestations of a single type of vibrating one-dimensional string-like entity that expand and contract as they gain or lose energy. As they are beyond tiny, one-trillionth of a trillionth the size of an atom, obviously no one has ever seen one. They only definitely exist within the realm of mathematical formulae.

String theory was formulated in the mid-1980s and was quickly recognized as the best hope for the physicists’ dream of a theory that would unify relativity and quantum theories, the grand unified theory or theory of everything. However, it rapidly moved in the opposite direction. As it failed to explain certain things, variations were suggested to account for them, and so every attempt to fix the initial problem ended with another variant of the basic theory – adding new excrescences to the equations. As the number of variations multiplied exponentially, creating new
sub-theories
, each with its own problems, attempts to fix those led to more variations. And so on.

Physicists belonging to the old guard reacted with alarm. Richard Feynman declared: ‘I don’t like that for anything that disagrees with an experiment, they cook up an explanation – a fix-up to say, “Well, it still might be true.”’
²⁴

The numbers involved are literally beyond imagining. Based on the currently-understood value of certain cosmological parameters, when all the different variables are taken into account, there are around 10
⁵⁰⁰
possible versions of string theory. That’s 1 followed by 500 zeroes – difficult enough to write down, let alone imagine – about six times the number of atoms calculated to exist in the observable universe. As Smolin points out:

In 1995 the term ‘M-theory’ was coined in an attempt to bring order to the chaos. M-theory simply means the single theory that is assumed to lie behind all the variations of string theory and which, once established, will reconcile them all. Although ‘M’ was chosen randomly – like labelling an unknown quantity ‘X’ – those to whom it is the ultimate answer have happily tied themselves in knots trying to work out what it means, suggesting it might stand for ‘magic’, ‘mystery’ or ‘mother’. Those who are undecided about its value suggest maybe it stands for ‘maybe’. Sceptics prefer ‘myth’. Despite the fact that M-theory is simply shorthand for a desperately needed, but currently
non-existent
solution to the complex problems posed by string theory, many physicists now solemnly make statements like ‘according to M-theory …’

In a seminal paper in 2002, Leonard Susskind, the ‘father of string theory’, one of those who originally formulated it in the late 1960s, proposed a unification of the string and multiverse theories that made a virtue of the vagueness of M-theory. He was compelled in that direction by the astonishing precision of the near-cancellation of vacuum energy that we discussed earlier, which he realized could only point to an anthropic explanation. Susskind proposed that every variation of string theory was as correct as any other – each simply defines the laws of physics for a
different universe. In what he termed a ‘landscape’ of string theories, he proposed that rather than one theory of everything, there are really lots of ‘everythings’, each with its own theory.

So, although the term ‘M-theory’ was originally invented as an umbrella term for the 10
⁵⁰⁰
competing variations of string theory, its advocates, most prominently Susskind and Stephen Hawking, have turned it into a single theory in its own right. This ‘proves’ that there are 10
⁵⁰⁰
different string theories defining the laws of physics for 10
⁵⁰⁰
different universes, and is therefore taken as proof that the multiverse is real.

This may be an ingenious exercise in explaining one unknown by another, but that’s all it is. As we have seen, the multiverse theory is after all by definition untestable, and M-theory unproven to say the least. As Jim Al-Khalili, theoretical physicist at the University of Surrey, commented:

The situation thus becomes very much like the argument between those who insist their chosen god is bigger and better than any other, a line that so rouses Richard Dawkins’ ire. To him, this is ludicrous even to begin to debate, as
no
gods exist. Yet here we have a very similar attitude. The arguments about multiverses and string theory are basically
theological
debates without a god or gods.

Clearly the multiverse explanation of why we live in a bio-friendly universe is (to put it as kindly as we can) at best speculative. As Smolin comments, because the multiverse hypothesis can’t be confirmed by direct observation, it can’t be used as an explanation and conversely, ‘the fact that we are in a biofriendly universe cannot be used as a confirmation of a theory that there is a vast population of universes.’
²⁷
The late John Archibald Wheeler, who took on Einstein’s mantle in the 1950s, discovered black holes and is widely regarded as the greatest theoretical physicist of modern times, considered the multiverse as unscientific speculation that carried ‘too much metaphysical baggage’.
²⁸