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Uniqueness of the Universe
it doesn’t require special proof that the science of cosmology has
very little effect on the daily life of an average individual. Although it seems overwhelmingly distant from our immediate
concerns and mundane worries, cosmological ideas have, for
centuries, played an essential role in shaping philosophical views
and therefore they have heavily influenced numerous aspects of
religious and political life.
as a science, limits itself to the study of the universe as a whole;
its contents, structure, and evolution.
Cosmological beliefs are based on the conclusions drawn from
astronomical observations and mathematical models, but they still
substantially influence the media and raise public interest.
study of cosmology has changed from a speculative enterprise into a
data-driven science that is part of a modern standard physical
theory and supported by a wealth of observations.
Nevertheless some theoretical proposals are being made for
the very early stages of the universe that have no observational
support; and sometimes it may be impossible to ever obtain such.
Thus in some respects it remains a principle driven
enterprise, with observation subordinate to theory.
Which means that the foundations of this science are
inherently confined to some degree of speculation.
this book we are going to undertake a breathtaking journey into the
very roots of the philosophy of cosmology in order to rigorously
appraise this degree of possible speculation.
This will allow us to make an attempt to define the ultimate
limits of human knowledge in order to form a sober view of what,
exactly, we can and cannot know.
hope that our effort will escape the possible accusations in
agnosticism and we will distant ourselves from the famous saying of
Socrates “I know that I know nothing” by trying to estimate the
true limits of our knowledge while appreciating tremendous progress
of science that took place since the days of this great Greek
first difficulty that the philosophy of cosmology encounters is the
uniqueness of the universe. The
most fundamental issue is that there is only one universe. This
essential uniqueness of its object of study sets cosmology apart
from all other sciences. In particular, the unique initial conditions that led to the
current state of the universe that we have the honor to observe
today were somehow “set” by the time that physical laws as we
know them started governing the evolution of both the universe and
its contents. We are not able to alter these unique initial conditions in
any way. They are given
to us absolute and unchangeable.
of the major implications of that is that the universe itself cannot
be subjected to physical experimentation. Obviously we cannot re-run
the universe with the same or altered conditions to see what would
happen if they were different, so we cannot carry out scientific
experiments on the primary object of our study, the universe itself.
Furthermore, due to its uniqueness the universe cannot be
observationally compared with any other universes.
example, the laws of inheritance, which laid the foundation for
modern genetics, derived by Gregor Mendel, needed tests on over
28,000 pea plants. His experiments wouldn’t be possible if he had
only one pea to examine.
Unfortunately, like having only one pea, we have only one
universe to study, and, moreover, that we can only partially
observe. Because we
cannot compare our universe with any other universes we are
considerably limited in our ability to derive certain laws that
would apply to the whole group of objects that we aren’t even sure
example may illustrate the intriguing thought that the concept of
‘Laws of Physics’ once it applies to only one object is
questionable. We cannot scientifically establish `laws of the
universe' that might apply to the class of all such objects, for we
cannot test any proposed law except in terms of being consistent
with one object. Indeed
the concept of a ‘law’ becomes doubtful when there is only one
given object that is possible to study.
The basic idea of a physical law is that it applies to a
group of objects, all of which have similar characteristics despite
some possible variations. These variations result from different
initial conditions for the systems on which the law acts.
Scientific experiments allow us to vary the initial
conditions of the systems we wish to test. This is not possible in the case of cosmology because we
cannot re-run the universe in the lab.
can observe the laws of physics locally and we can confirm that they
look the same on the small scale anywhere in the universe, but we
have a certain difficulty to extrapolate them on the higher level of
hierarchy of the organization of the universe.
For example, Newton’s Laws of Gravity
work perfectly on the level of our solar system, but they can not be
applied with the same degree of certainty once we examine the
orbital speeds of stars around the galactic center, which turned out
to be higher than expected or behavior of the galaxies in the
clusters that stay together despite the fact that their visible mass
wouldn’t be able to hold them together, and some other issues.
Even though the modern cosmology explains this by the
presence of the missing mass that was dubbed “dark matter” in
the halos of the galaxies, there are still some alternative theories
like modified Newton’s gravity (MOND)
that challenges the mainstream cosmology from time to time, quite
upsetting the advocates of Lambda Cold Dark Matter model that
currently is in general agreement with observed phenomena.
the higher level, the laws of gravity cannot explain why the
universe is expanding and even accelerating in its expansion.
There is a need for new laws that would describe the missing
energy responsible for such expansion, dubbed “dark energy”
either in a form of cosmological constant or quintessence.
Although, such new laws that may provide reasonable
explanations cannot be checked because we cannot observe them on any
other object but our universe itself.
the restriction of a global solution to a local neighborhood, we can
employ as a solution the hypothesis that we have zillions of
“mini-universes" on which may test the laws that control the
local nature of the universe. But a mini-universe is not the
universe itself; it is a small part of the whole. By examining these
“mini-universes" and seeing if they are essentially the same
everywhere, we can to some degree, check that the laws of physics
are the same everywhere in the universe (a key feature of all
cosmological analysis), and secondly that the universe is
practically the same in all areas and directions.
But the latter feature is what has to be explained by a `law
of the universe’; verifying homogeneity does not explain why it is
the concept of probability is problematic in the context of
existence of only one object. Problems arise in applying the idea of
probability to cosmology as a whole, but a concept of probability
underlies much of modern argumentation in cosmology. For instance,
we are talking about very low probability of the observed ‘fine
tuning', which means that all physical constants have such precise
values that allow them to create conditions not only for life to
exist but also for atoms to form.
If the constants would be different the atoms would never
form, the stars would never shine, thermonuclear synthesis of the
elements wouldn’t be possible and the diversity of the chemical
elements that supports life would never emerge.
assumes both that things could have been different, and that we can
assign probabilities to the set of possibilities that have never
become a reality in an astronomically provable way. The issue here
is to explain in what sense they could have been different with
well-defined probabilities assigned to the different theoretical
scenarios, if there is indeed only one universe with one set of
cannot scientifically establish laws of creation of the universe
that might determine different initial conditions and resulting
probabilities. First of all, it is useful to distinguish between the
experimental sciences, physics, chemistry, microbiology for example,
on the one hand, and the historical and geographical sciences,
astronomy, geology, evolutionary theory for example, on the other.
It is the experimental sciences that are usually in mind in
discussions of the scientific method. The understanding in these
cases is that we observe and experiment on a class of identical, or
almost identical objects and establish their common behavior. The
problem then resides in just how identical those objects are.
Quarks, protons, electrons, are all exactly identical to each other,
and so have exactly the same behavior (indeed this feature underlies
well-tested quantum statistics). All DNA molecules, frogs, human
beings, and ecosystems are somewhat different from each other, but
are similar enough nevertheless that the same broad descriptions and
laws apply to them; if this were not so, then we would be wrong in
claiming they belonged to the same class of objects in the first
place. Water molecules, gases, solids, liquids are in an
intermediate category, almost identical, certainly describable
reliably by specific physical and chemical laws.
regards the geographical and historical sciences, here one
explicitly studies objects that are unique (the Rio Grande, the
continent of Antarctica, the Solar System, the Andromeda galaxy,
etc.) or events that have occurred only once (the origin of the
Solar System, the evolution of life on Earth, the explosion of a
certain supernova star.). Because of this uniqueness, we can only
observe rather than experiment; the initial conditions that led to
these unique objects or events cannot be altered or experimented
with. However at least in principle, there is a class of similar
objects out there (other rivers, continents, planetary systems,
galaxies, etc.) or similar events (the origin of other galaxies, the
evolution of other planetary systems, the explosion of other
supernovae, etc.) which we can observe and compare with our specific
exemplar, also carrying out statistical analyses on many such cases
to determine underlying patterns of regularity; and in this respect
these topics differ from cosmology.
we truly cannot carry out such analysis then that subject poses a
legitimate question of the nature of cosmology. One may claim that
the dividing line here is that if we convince ourselves that some
large-scale physical phenomenon essentially occurs only once in the
entire universe, then it should be regarded as part of cosmology;
whereas if we are convinced it occurs in many places or times, even
if we cannot observationally access them (e.g. we believe that
planets evolved around many stars in other galaxies), then study of
that class of objects or events can be distinguished from cosmology
precisely because there is a class of them to study.
scientists have tried to get around this set of problems by
essentially denying the uniqueness of the universe. This is done by
proposing the physical existence of `many universes' to which
concepts of probability can be properly applied envisaged either as
widely separated regions of a larger universe with very different
properties in each region (as in chaotic inflation for example), or
as an ensemble of completely disconnected universes with no physical
connection whatsoever between them in which all possibilities are
so far there is no hard proof that ‘other universes” may exist
and we have to stick to the statement that the universe we live in
is unique at least from our point of view and we need to deal with
philosophical implications of such approach