Changes in the Scientific Paradigm

Thomas Kuhn

As Thomas Kuhn pointed out, from time to time there are shifts in the scientific paradigm that cause sharp deviations in the direction of research. These shifts can occur in any of the sciences. Here are some important historical examples:

Puerperal fever was for centuries the leading cause of death in women giving birth. In 1795, the Scottish obstetrician Alexander Gordon claimed that the disease was transmitted by doctors and midwives. In 1842, the English physician Thomas Watson, known for his description of the aortic pulse, recommended that doctors wash their hands with diluted lye before attending a birth. And in 1847, the Austrian physician Ignaz Semmelweis advised the same, based on data showing that the incidence of puerperal fever was higher in hospitals than in births taking place at home, and higher among women in labor attended by doctors than by midwives. Semmelweis' proposals were violently rejected by contemporary physicians, who were outraged by the idea of ​​being blamed for infections caused by themselves, to the point that Semmelweis was committed to an asylum where he only survived two weeks. His death is believed to have been the result of a beating by the asylum guards when Semmelweis, who was 47 years old, tried to escape. His proposals were confirmed by the discovery of the germ theory of infectious diseases by Louis Pasteur, according to which diseases are caused by microorganisms, and not by miasmas transmitted by air, as previously believed. This caused an abrupt change in the scientific paradigm applied to medicine.

Is homo economicus rational?

Nicolás Bernoulli

In 1713, Nicolás Bernoulli formulated the St. Petersburg paradox, which can be summarized as follows:

Let us consider the following game: a coin is tossed. If it comes up heads, you receive $2. If it comes up tails, it is tossed again. If it comes up heads, you receive $4. If it comes up tails, it is tossed again. And so on. With each toss, the prize is multiplied by 2. How much would you be willing to pay to participate in the game?

The probability of winning $2 is 0.5; the probability of winning $4 is 0.25; the probability of winning $2^k is 2^-k. The expected value is obtained by multiplying each value by its probability and adding them all together. So the expected value of the profit that could be obtained by playing that game is:

The Chinese and artificial intelligence

Wolfgang von Goethe

The media has been reporting on a recent breakthrough in LLMs (large language models), the hottest applications in the field of artificial intelligence, which in the last two years have given rise to great hype, suspicions of stagnation and accusations of excessive energy and water costs.

This latest breakthrough has been achieved by a Chinese company, DeepSeek, which has jumped to the front line because it successfully competes with the big companies in the field, OpenAI (which built ChatGPT and GPT4) and Google (with GEMINI), but at a lower cost.

There are now many tools of this type, but the two mentioned in the previous paragraph (GEMINI and GPT4) provided the best performance, although they were the most expensive. Their code is secret, owned by the two companies (Google and OpenAI) and users cannot modify it. Alongside them, now there are others with open source, which can be adapted to each user, but with lesser performance.

Anything can be assigned a probability?

In the previous post I mentioned the book Radical Uncertainty: Decision Making Beyond the Numbers by Mervyn King and John Kay. The book, written by two prestigious British economists, attacks the bad use of statistics and probability calculus in fields where they are not always applicable, such as history, economics and the law. Let’s look at a few examples:

• What do we mean when we say that Liverpool F.C. has a 90% chance of winning the next match? One possible interpretation is that if the match were to be played a hundred times, with the same players and the same weather conditions and the same referee, Liverpool would win 90 times, and draw or lose the other ten. But the match will be played just once. Does it make sense to talk about probabilities? No, because there are no supporting data on frequency. What is meant is that the person speaking believes that Liverpool will win. Nothing more. It is a subjective probability. Milton Friedman wrote: We can treat people as if they assigned numerical probabilities to every conceivable event. (Price Theory, 1962).

Risk versus Uncertainty

I have read the book Radical Uncertainty: Decision Making Beyond the Numbers by Mervyn King & John Kay. As the title suggests, it talks about radical uncertainty. What is uncertainty? Its definition is simple: any uncertain knowledge. But there are two types of uncertainty:

·         Risk: Measurable or resolvable uncertainty. Probability calculations can be applied. Example: the outcome of a roulette or lottery game. Problems of this type can be called puzzles. Phenomena of this type are stationary (their properties do not change over time).

·         Radical uncertainty: Uncertainty that is not measurable. It arises when there is obscurity, ignorance, vagueness, ambiguity, ill-defined problems, lack of information. It cannot be described by probability calculations. Problems of this type can be called mysteries. Phenomena of this type are usually not stationary.

Probability of the existence of extraterrestrial life

In a previous post I talked about the probability of the existence of extraterrestrial intelligence and mentioned the difficulty of its calculation, as we don’t know of any planet where they exist, apart from Earth, and to calculate the probability of an event one must know the number of favorable cases and the number of possible cases. For extraterrestrial life, we ​​don’t know either.

In another post I detailed the conditions that should be necessary if life similar to ours were to be possible on a planet similar to Earth. These conditions are many, which reduces the probability that we will find life on some extrasolar planet located in our vicinity. In fact, among the almost 10,000 planets detected so far (of which just over half have been confirmed), 65 are at a distance from their star that could be favorable for life (the Goldilocks zone), but only three of them orbit around stars similar to the Sun (of the stellar class G).

500 posts in PopulScience

This is the 500th post I have published on the Spanish version of this blog, just after 11 years since the creation of, on January 15, 2014. The English blog, PopulScience, where I almost always publish the same posts, translated into English, came about later. I did not publish the first article until August 12, 2014, so it was half a year late. However, over the years, it has gradually recovered the lost ground, to the point that right now there are 498 posts, only two less than the Spanish blog.

Why is this? It is very simple: in the United States the summer holidays are shorter and end in mid-August, while in Spain the whole month of August is a non-working month. When I take a vacation from the blog, I stop publishing posts in the Spanish version for most of July and all of August, and start the new course at the beginning of September. On the English blog, however, I start in mid-August, and so every year I catch up on two or three posts. After eleven years, I have almost made up for the half-year delay that the English blog was behind. This summer, God willing, the two blogs will be on a par.

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).