Numerous scientists have said in recent decades that our universe
seems to be “just right” in terms of having laws, forces, and
constants that allow for the evolution of intelligent life. We see
in our universe numerous examples of
fine-tuning where some number in
nature improbably exists within a tiny range of values that are
compatible with the existence of intelligent life. Scientists say
that tiny changes in the fine structure constant, the vacuum energy
density, the strong nuclear force, the gravitational constant, or the mass of quarks would
throw things off so that creatures like us would never have appeared.
We have one dramatic example of this fine-tuning in the fact that
each proton has an electric charge exactly equal in magnitude (
to 18 decimal places) to the electric charge of each electron, even
though each proton is 1836 times more massive than each electron.
This coincidence is unexplained by the standard model of physics, and
if the equality did not exist, planets would not hold together. There
is a similar dramatic coincidence involving the Higgs field, which
(minus a floundering SUSY theory) seems to be fine-tuned to 30
decimal places, as discussed
here, where a physicist says, "we need cancellation of all these different effects to one part in about 1,000,000,000,000,000,000,000,000,000,000." As if that wasn't enough, the
vacuum energy density or cosmological constant is apparently between 10
60 and 10
120 times smaller than the value predicted by quantum
field theory, suggesting some almost miraculous balancing act
going on in the physics of our universe (as discussed
here, where it is called the "worst problem of fine-tuning in physics"). These items and numerous
similar items have been extensively discussed in recent decades by
scientists, in pieces such as
this one.
Now if there was not much substance to these indications of
fine-tuning in our universe, they would have been brushed off and
ignored by those who ponder the universe from a materialistic standpoint. Instead quite the opposite
seems to have happened to a large degree. Rather than ignoring these
indications of fine-tuning, many recent thinkers have let these
indications drive them to a huge change in thinking: the assumption
that there is a multiverse or ensemble of universes.
The idea behind the multiverse is that there are a huge collection
of universes, presumably each with a random set of physical
characteristics, laws, and physical constants. The person who
advances such a concept uses it in an attempt to reduce the “miracle
of habitability” of our incredibly improbable universe-- to make
the ultimate “long shot” look like something that is likely to
occur at least once. Assume that the chance of a random universe
being compatible with the evolution of intelligent beings is only 1
in N, where N is some extremely high number. If we assume that there
is a number of universes much greater than N (say N times 1000), than
there might actually be a likelihood that some universe would purely
by chance meet all of the requirements necessary for intelligent
life.
Let us take a close look at this idea of a multiverse, and see
whether it holds up to scrutiny, in terms of explaining anything.
Before we can do that, we must carefully define some terms and
principles.
When talking about probability, mathematicians use the term
trials
to mean something like an experiment in which different results can
occur. A trial may or may not be a formal experiment. It might be
something like a hand in a game of cards, a roll of the dice, a
particular spin of a roulette wheel, or a particular swing of the bat
while a baseball player is at bat. In talking about a possible
ensemble of universes, then each different universe would be
considered a trial.
Now let me define two important terms.
Term |
Definition |
Number of successful trails |
The total number of successful trials in a series of random
trials |
trial success probability |
The chance that a random trial will be successful. When there
are a large number of trials, the trial success probability tends
to be equivalent to the ratio between the number of trials that
are successful and the number of trials that are unsuccessful |
Here are some examples to clarify the use of terms.
Example 1: If one thousand raffle tickets are sold in a
raffle, and a winner is selected from a barrel containing the stubs
of all of these raffle tickets, then the number of successful trials
will be 1 and the trial success probability is 1 in 1000. The number
of successful trials is exactly one because there is only one winning
ticket chosen. The chance of any ticket holder winning or the trial
success probability is 1 in 1000.
Example 2: If I make three bets on some position of a
roulette wheel with 38 positions, each time betting on a particular
spin of the roulette wheel, then the trial success probability is 1
in 38, because on each spin of the wheel there is one chance in 38 of
winning. The number of successful trials depends on chance. It could
be as high as 3 if I am very lucky, or it could be as low as 0 if I
am unlucky.
Now, what general principles can we state about the relation
between the number of successful trials and the trial success
probability? They are as follows:
Principle 1: If the trial success probability is zero,
the number of successful trials must be zero. This simply means
that if there is no chance of one trial being successful, there must
be no successful trials.
Principle 2: I
f the number of successful trials is zero,
it does not necessarily mean that the trial success probability is
zero. For example, in Example 2 above it is entirely possible
that the number of successful trials might be zero, meaning the
gambler loses on all three spins of the roulette wheel. But with each
spin of the roulette wheel there is 1 chance in 38 of being
successful; in other words the trial success probability is 1 in 38.
Principle 3: In some cases increasing the trial success
probability will tend to increase the number of successful trials,
but an increase in the trial success probability will not always mean
an increase in the number of successful trials. For example, let
us define a successful trial for a baseball hitter as hitting a home
run. A hitter may improve his batting technique, thereby increasing
the trial success probability, his chance of hitting a home run. That
will tend to increase (over a long enough time) the batter's number
of successful trials, or number of home runs, but is not guaranteed
to do so during a particular number of trials.
Principle 4: For random trials that do not involve
practice at a skill, increasing the number of trials tends to
increase the number of successful trials or make it more likely to be
at least one, but increasing the number of trials does not increase
the trial success probability. For
any random process such as the spin of a roulette wheel of the throw
of a pair of dice, an increase in the number of trials or attempts may tend
to increase the chance of one successful outcome (or increase the
number of successful outcomes), but the number of trials or attempts
does not tend to increase the chance of success on any random one of
the trials, that is the trial success probability. The one exception
to this principle is that when the trials involve a human practicing,
the chance of success on one trial may actually increase, because of
the tendency of a human to improve with practice.
Now let us look at how all of this is relevant to the theory of a
multiverse. The theory of a multiverse is that there are multiple
universes, each with a different random set of characteristics.
Speaking in terms of probability theory, each of these universes may
be considered a separate trial. The series of trials in this case is
the entire ensemble of universes, or multiverse. The theory has been
introduced to try to explain why a universe such as ours (which looks
like an incredibly improbable long shot) might exist.
General Term |
Meaning in This Case |
Normal Thinking |
Multiverse Theory |
Number of trials
|
Number of universes
|
1 (?)
|
Very many
|
Number of successful trials |
Number of habitable universes with life
|
1 (?) |
Many |
trial success probability |
The chance of any one random universe being habitable
|
Incredibly small number such as 1 in a billion trillion
quadrillion |
Incredibly small number such as 1 in a billion trillion
quadrillion |
The last line in this table indicates why the multiverse theory
(at least in its simple form) is a total bust, dud, and failure from
an explanatory standpoint. Because of Principle 4 described above,
the multiverse theory leaves us with a trial success probability that
is not any higher than the incredibly low number we started out with.
If the chance of our universe randomly being habitable is something
like 1 in a billion trillion quadrillion before we think about a
multiverse, then we have exactly the same incredibly small number
after we adopt the multiverse theory.
In other words, the multiverse theory does nothing to make the
“miracle of habitability” of our universe seem any less miraculous.
It's the same type of “ten consecutive royal flushes in
spades” type of unlikelihood, even after we adopt a multiverse.
The longest of long shots of our universe being habitable is just as
long a long shot even after we assume a multiverse.
To help clarify how great a weakness this is in the multiverse
theory, let us look at a wildly speculative theory that would not suffer from
such a defect (although it would suffer from a different problem). I
can call this fanciful theory the
viral multiverse theory.
The theory can be fancifully expounded as follows:
Once upon a time there were a vast number of uncreated
universes, each with a different random set of characteristics.
Purely by chance, one of these universes was habitable for
intelligent life. Then, through some weird strange process, that
universe infected another universe with its favorable physics, making
that universe habitable. Then the infected universe itself infected
another universe with its favorable physics. Habitability thereby
spread like a virus throughout all of the ensemble of universes. When
this long infection period ended, every single universe in the vast
ensemble of universes was habitable.
Now let's expand the previous table to include this fanciful
theory.
|
Normal Thinking |
Multiverse Theory (Regular) |
Viral Multiverse Theory |
Number of universes
|
1 (?)
|
Very many
|
Very many
|
Number of habitable universes with life
|
1 (?) |
Many |
Very many (all trials successful) |
The chance of any one random universe being habitable (trial success probability) |
Incredibly small number such as 1 in a billion trillion
quadrillion |
Incredibly small number such as 1 in a billion trillion
quadrillion |
100% (all universes end up habitable) |
When we compare the regular multiverse theory to this viral
multiverse theory, it helps clarify what an explanatory failure the
regular multiverse theory is, and how lame the theory is from the
standpoint of explaining anything. Fanciful and ridiculous as it may
be, the viral multiverse theory leaves us with an explanation for why
our universe is habitable, something which the regular multiverse
theory completely fails to do (as the trial success probability does
not change after we believe in a multiverse).
The believer in the viral multiverse theory can say, “Why of
course our universe is habitable – all of the universes in the vast
ensemble are habitable.” The believer in the regular multiverse
theory can say no such thing, and in that theory
our universe
being habitable is still the longest of long shots.
So why can't we just adopt a theory like this viral multiverse
theory? It's because the idea of one universe infecting another
universe with favorable physics is absurd. No one has the slightest
idea of how one universe could infect another universe, causing the
second universe to have favorable physics like the physics of the
first universe. Imagining such a thing seems like an invalid case
of applying an idea from biology into the realm of physics where it
has no business existing. No one even has any workable idea of how there could
be any contact whatsoever between one universe and another universe.
Plus there are cosmological reasons for thinking that our universe
has had favorable physics from its earliest beginning. Numerous scientists have noted that if the Big
Bang hadn't been just right, the universe would either have expanded
too fast for galaxies to form, or the universe would have collapsed
in on itself or collapsed into black holes. So we can't really imagine that our universe started out as “any
old universe” and then got its favorable physics long after it
originated.
The multiverse enthusiast therefore has a Hobson's choice, a
choice between equally unattractive alternatives. He can choose a
regular multiverse theory which has no explanatory power because it
does not change the incredibly low chance of our universe being
habitable, or he can choose some weird variation of the multiverse
theory that might explain why our universe is habitable, but at the
price of requiring you to believe in some crazy, laughable idea such
as a multiverse-wide viral cross-pollination of universe physics (or
some other equally ludicrous and byzantine piece of conceptual
baggage).
So where does this leave the person who wishes to explain away the
astonishing fine-tuning that our universe seems to have? That person
is left in an uncomfortable place, stuck with a deep mystery (“the
miracle of habitability”) he can't explain away with a plausible physical theory that gets the job done with explanatory rigor.
Are the cosmic dice loaded?