Although I have spoken about some of these things in other posts, I’ll put together here three questions that, for now, don’t have a scientific answer, and perhaps never will.
- Did the universe begin to
exist at the Big Bang, or was there something before? This controversy is much older than many
think. Three quarters of a millennium ago, Thomas Aquinas wrote this in
his Summa
Theologiae (Part I,
Question 46):
It cannot be proven by demonstration that the world
has not always existed.
In other words, according to Aquinas, the question of creatio originans (that the world had a beginning) cannot be solved by human reason. It should be noted, however, that creatio ex nihilo (the fact that the world was created) would be within the reach of reason. In other words: reason would let us reach the conclusion that the universe was created, but we cannot prove that it had a beginning.
The controversy came back to the forefront with the
triumph of the Big
Bang cosmological theory. Alternative theories (which I
described in another
post) disagree on whether the time associated with our universe began with
the Big Bang. Our two main physical theories do not let us know
what happened before Planck’s time (5×10-44 seconds after the Big Bang), so those proposals must be considered, at least for the time being,
speculations without a scientific basis.
On the other hand, the second principle of
thermodynamics, which predicts the heat death of the universe, seems to imply
that the universe must have had a beginning. Otherwise, we would be now in
thermal death. We know that this principle applies throughout the known history
of the universe, but did it also apply before the Big Bang, assuming this phrase makes sense? Nobody knows.
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| Aristotle |
- Is the universe finite or infinite? Paraphrasing Aristotle, we could say that
Nature abhors infinities.
The two current physical theories present a
problem: they both predict infinities. General relativity does that in
gravitational singularities: the Big
Bang and black holes, whose density would be literally
infinite. Quantum mechanics, in the vacuum energy and other quantities that
must be renormalized in quantum field theory. Some scientists think that a
quantum theory of gravity, that we still don’t have, would eliminate these
infinities. If so, we need to wait until a future genius will solve it.
But my initial question in this section refers to
something else:
Is space finite or infinite?
Cosmologists disagree on the answer to this
question. Some, like Einstein, would rather the universe be finite, although
unlimited. Others say that it could be infinite, and draw the consequence that
everything that happens and has happened on Earth, including our personal life,
must be repeated in an infinite number of places in the universe. In 2014, Soler
Gil and I published an
article that refutes some of these arguments. That article contains the
following paragraph:
[I]f we start from the standard cosmological model, the possibility that
the universe is infinite can only be deduced if an additional postulate is
accepted, namely the so-called ‘cosmological
principle’, which asserts that the universe is homogeneous and isotropic at
sufficiently large scales. This principle is
necessary to extrapolate the cosmological description of the universe beyond
the boundaries of the observable universe. However, its introduction gives rise to serious problems. In fact, the
cosmological principle is being increasingly questioned from both sides:
theoretical arguments and observational evidence. Therefore
an agnostic position with respect to the extrapolation of the known universe
beyond our horizon seems to be epistemologically reasonable, especially when
that extrapolation leads to infinity.
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| Gregory Chaitin |
- Is everything in the
universe the work of chance? Perhaps this question does not make sense, since chance is
undecidable, as Gregory Chaitin proved (see this
post in my blog). His theorem, proven in 1975, says in essence the
following:
The randomness of integers is undecidable. Although
randomness can be defined accurately and can even be measured, in general it
cannot be proved that a set of numbers is random. This sets a new limit to what
is possible in mathematics. (Randomness and Mathematical Proof, Scientific
American 232, No. 5, May 1975, pp. 47-52).
In the same post I described a thought experiment that shows that the discrimination between chance
and design is undecidable. If, starting from my experiments on artificial life,
I ended up by creating a world designed by me, where intelligent beings
appeared, these beings could come to the conclusion that their existence was a
consequence of chance, when in fact it would be a clear case of design. If they
would decide that I don’t exist, it seems to me that they would be wrong.
One of my science fiction novels, Jacob’s Ladder, is based on this idea.
Thematic Thread about Standard Cosmology: Previous Next
Manuel Alfonseca
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