Giant Viruses

John Maynard Smith

In 1966, H.J. Muller defined living beings as follows: Any being capable of multiplying with inheritance and variation. With this definition, which prioritizes reproduction and evolution as the definition of life, viruses should be considered as living beings. Other biologists, such as John Maynard Smith, thought that this criterion was too broad. It would mean that nucleic acids are alive, since they are capable of reproducing with inheritance and variation. That is why they propose adding another criterion: A living being is capable of reproducing and metabolizing. This would exclude nucleic acids, and therefore viruses, which are nucleic acids enclosed in a protein capsule, and viroids, which are isolated nucleic acids.

The tree of life, the family tree of all species of living beings, seems to indicate that all beings formed by one or more cells descend from a single individual, the first living being, which is called LUCA (Last Universal Common Ancestor). As I said in another post, some think that perhaps LUCA was not a single individual, but a network of individuals. But where do viruses come from?

Universe or multiverse?

In the posts in this blog I have often said that theories about the multiverse (there are many) are not science, but speculations, because it is impossible to design an experiment that demonstrates the existence or non-existence of these multiverses.

In an article published in May 2023 in the journal Springer Nature, entitled Is Everyone Probably Elsewhere?, the authors claim that it would at least be possible to distinguish between the following two hypotheses:

1. Our universe is unique, it does not belong to any multiverse.
2. Our universe belongs to some multiverse. Of course, we would have no idea what type of multiverse it would belong to.

Physics, Mathematics and Mathematical Physics

Eugene Wigner

Eugene Paul Wigner was a Hungarian physicist who received the Nobel Prize in Physics in 1963 for his contribution to the theory of the atomic nucleus and elementary particles. In a famous article published in 1960, Wigner said:

It is important to point out that the mathematical formulation of the physicist's often crude experience leads in an uncanny number of cases to an amazingly accurate description of a large class of phenomena. (“The unreasonable effectiveness of mathematics in the natural sciences”. Communications on Pure and Applied Mathematics 13: 1-14).

The lost worlds of 2001

Arthur C. Clarke

2001: A Space Odyssey (1968) is one of the most representative science-fiction films in the world of cinema. Its script, which took several years to develop, was elaborated jointly by Arthur C. Clarke, a renowned science-fiction writer during the golden age of this genre, and Stanley Kubrick, a famous film director. While he was working on the script, Clarke wrote a book with the same title as the film, which was published after the film’s release.

In 1972 Arthur C. Clarke published a book entitled The Lost Worlds of 2001, where he mixes reminiscences about the elaboration of the script with discarded chapters from the book. By reading this book, we can follow the process of the construction of the film by Clarke and Kubrick and the successive stages of the plot. I agree with them that the final script was much better than the intermediate versions. Reading this book has led me to the following two comments:

Quantum mechanics or classical physics?

John Stewart Bell

The debate about which theory explains better the behavior of elementary particles, either quantum mechanics (with strange consequences such as state superposition and quantum collapse) or a still unknown classical physics-type theory that eliminates the need for such phenomena, has been going on since Bohr and Einstein started this debate almost one century ago.

The issue seemed to have been decided when John Steward Bell formulated in 1964 the famous Bell inequality, which I described in another post. However, as some physicists still raise the question, other means of distinguishing between the two types of theories are still being sought. One of them is the Leggett-Garg inequality (LGI), to which I will dedicate this post, based on a recent article in Physics World, dated August 12, 2024.

Time travel in science fiction

H.G. Wells

A few years ago, I published in this blog a series of posts about the scientific aspect of time travel, the paradoxes it could cause if it were possible (which almost certainly it is not) and proposed solutions to these paradoxes, such as the quantum multiverse, one of the most absurd theories physicists have ever concocted. In another post I talked about the scientific errors in Michael Crichton’s sci-fi novel Timeline, which tries to avoid the paradoxes in this way, but does it poorly.

Here I am going to speak about time travel from a literary point of view, as a subgenre of science fiction. In this context, it’s irrelevant that time travel may or may not be possible. We are interested in the question, because this is one of the most frequent topics in this type of literature.

Correlation or causality

Francis Galton, Darwin’s cousin, best known for promoting eugenics, invented the mathematical concept of correlation. Since then, many mistakes have been made relating correlation and causality, which sometimes coincide, but can also be completely different.

Two variables are said to be correlated when increases in one resemble increases in the other, and decreases in one resemble decreases in the other. But not all correlations are the same: to distinguish them, Galton devised the correlation coefficient, a number between -1 and 1.