In two previous posts I dealt with the relation
between the
multiverse theories and the problem of fine tuning, noting that those
theories do not solve the problem. This third post describes briefly what is
the fine tuning problem.
Brandon Carter |
In 1973 Brandon Carter formulated the anthropic
principle, a name later deplored by its author, because it may
be prone to misunderstandings. This principle is simply the verification that
the universe must fulfill all the conditions necessary for our existence, since
we are here.
Over a decade later, John Barrow and Frank
Tipler published a book entitled The
anthropic cosmological principle, which offered a stronger version of
the anthropic principle, posing that the values of many of the universal constants
are critical and minor variations would make life impossible. This finding
raises the fine tuning problem, based
on the analysis of the possible effects of changing the values of those constants.
In other words, the universe seems designed to make life
possible. Let’s look at a few examples:
1. The mass of the proton is 1836 times
that of the electron. The mass of the neutron equals 1838.4 times the electron:
0.13% greater than the mass of the proton. If the neutron mass had been just 0.15%
higher (i.e. 1841.2 times that of the electron, or 0.28% greater than that of
the proton) stars would not be able to produce helium from hydrogen. They could
still use the helium generated shortly after the Big Bang, but only for a
few million years. In such a universe, life would not have time to appear.
2. Modern physics knows four
fundamental interactions: gravitational, electromagnetic, weak and strong
nuclear. If the strong nuclear force were 0.5% more or less intense than it is,
carbon or oxygen could not be produced in stars. Without carbon or oxygen,
earth-like life would not be possible, since both elements are indispensable
for organic matter. The same would happen if the intensity of the
electromagnetic interaction differed by more than 4% in both directions from
its actual value.
3. In every nuclear fusion that occurs
in stars, 0.7% of matter is converted into energy. If the value of this
constant were 0.8% or more, all the hydrogen would have become helium during
the Big
Bang and there wouldn’t be any hydrogen in the universe to make living
beings or to provide energy to stars. If it was less than 0.6%, hydrogen fusion
would be impossible, the universe would consist only of hydrogen and stars would
not exist.
4. The cosmological constant,
introduced by Einstein in his cosmic equation and later rejected by himself,
has recently re-risen with the discovery of the accelerated expansion of the
universe. Its value, if its existence is confirmed, would be critical: if it
were higher than it is, the universe would have expanded so fast that galaxies,
or stars (or life) would never have formed. Lower values lead to a universe which
would have stopped expanding soon and contracted toward a Big Crunch, with no time for
life to appear.
All these parameters, plus a few more that I
don’t have room to mention, have values in the field of real numbers. The
probability of the existence of life is thus calculated by dividing the volume
of configuration space compatible with the existence of life, between the
volume of the total configuration space (the infinite continuum). Considering
the above critical values, it follows that the part of configuration space
compatible with life is ridiculously small. Some scientists believe that the
probability that the universe fulfills all the necessary conditions could be
between 0 and 10-500. Recall that the probability of the existence
of something can be zero, even though we know that a favorable case exists.
This was discussed in a
previous article.
Manuel Alfonseca
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