Some physicists sometimes act as if the hypotheses they propose to explain the mysteries of the universe are always true. But a hypothesis is nothing more than a proposal to explain a natural phenomenon, and it cannot be considered a confirmed theory until it has provided one or more surprisingly accurate predictions. This last detail, which is essential, is usually omitted.
In 2020, I read two popular books on cosmology and
particle physics (the two branches of physics are closely related):
- The
Big Bang, by Joseph Silk (2000). This book was recommended to me as a good
popularization of the Big
Bang
theory. The problem is that it discusses several strange theories, and several
particles whose existence has been proposed, as if they had been
confirmed. Thus, reading the book could confuse uninformed people,
contrary to the primary objective of popularization: to make those people
know more about cosmology and the history of the universe. Among the
hypotheses accepted as valid are string theory, currently in question, and cosmic inflation, which so far has not been confirmed.
- The
Dark Universe, by Catherine Heymans (2017). A good summary of the current
status of the standard cosmological model, focusing primarily on the
supposed existence of dark matter and dark energy, where the word dark should be understood to mean that we have no idea what
it is. In
this book, the author makes a typical mistake: sometimes (not always) she
confuses model
predictions with model
adjustments. Predictions are made when the model is used to predict something
we didn't know. As I said in the first paragraph of this article,
confirmed predictions validate the model. On the other hand, when a model
is developed, known data are used to adjust its parameters, but that
doesn't validate the model. Heymans correctly describes the use of baryon
acoustic oscillations to adjust the parameters of the ΛCDM model, but she is wrong in considering
that the model has been validated by studying the RCFM thermal power
spectrum, which was not a prediction, but an adjustment.
There are many particles whose existence has been
proposed to solve the mysteries of the many things we don't know about
cosmological theories. Some are very imaginative. The trouble is that their
existence is almost never confirmed, although authors of popular books often
speak as if they are real, and not mere hypotheses. Here are a few examples:
- Magnetic
monopoles, about which Silk's book says this: searches
have found that monopoles are few and far between in our galaxy. The truth is that not a single monopole has
ever been detected. Silk's statement gives the impression that they really
exist, as if the existence of theoretical particles were proven by the
fact that there is a theory that predicts them.
- The
photino:
This particle, predicted by supersymmetry theories, has never been found.
However, Silk says this: We know precisely how frequently [the photino] annihilation
process occurs, because once, long ago in the very early universe, it
occurred very frequently. How do we know, if it's quite possible that the photino does not
exist?
- Silk also mentions the
chargino. About this hypothetical particle, he says this: Experiments
have shown that the actual chargino abundance in terrestrial rocks and
seawater is far less than the predicted upper limit. This way of expressing it gives the false
impression that the existence of the chargino has been proved. To prevent
misunderstanding, the paragraph should be rephrased thus: As the
chargino has not been detected in rocks or seawater, its abundance, if it
actually existed, would be much lower than theoretical predictions.
Curiously, in Chapter 17 Silk jokes about this
supposed abundance of undetectable theoretical particles, when he says this: ...the
exotic weakly interacting particle candidates, of which there must exist a
number about equal to the square root of the number of particle physicists. In other words, Silk is aware of the current
precarious state of the predictions about the existence of exotic particles
that would explain dark matter, but sometimes he is carried away by the
optimism of other physicists.
As an example of the precariousness of these
theories, which often fail when subjected to experimentation, let's look at this
news article published in PhysicsWorld on March 27, 2025:
Atomic
anomaly explained without recourse to a hypothetical ‘dark force’
To summarize the news: in 2020, a team from MIT
detected a deviation in the theoretical predictions of the energy levels of the
ytterbium atom, a rare earth, which they immediately attributed to the
existence of a previously unknown dark
force, which would
naturally imply the existence of new particles. As usual, when a prediction
fails, physicists immediately propose the existence of dark matter or dark
energy and the corresponding mysterious particles.
Fortunately, this time things didn't go very far.
In 2025, a team of German physicists confirmed the anomaly, but managed to
explain it without resorting to dark forces or hypothetical particles, by studying
the interaction between the neutrons in the nucleus and the electrons in the
ytterbium shell.
But I have no hope
that this success of current theories over speculation will curb the
imagination of those physicists who, rather than science, seem to be doing
science fiction.
Thematic Thread about Standard Cosmology: Previous Next
Manuel Alfonseca
See you by mid-August