Information paradoxes

Woody Allen

As I have mentioned before, time travel, if it were possible, would cause many paradoxes. In a previous post I mentioned the paradox of unsourced information, which can be summarized thus:

A time traveler who lives in time 3 knows that a person A said or did something at time 2, prior to time 3. 

The traveler goes back from time 3 to time 1, prior to time 2, where he meets A. 

While they are together, the traveler suggests person A the idea of ​​doing or saying what he knows that person will do or say in the future, which has not yet taken place. 

Whose idea was it originally? Not the traveler’s, because he learned it from the history of person A at time 3. Not from person A, because the traveler suggested the idea to person A at time 1. 

The information in question has come out of nowhere, without anyone having thought it out.

The following diagram explains it.

Mistakes regarding natural selection

Charles Darwin

Since Charles Darwin coined this term, and included it in the title of his famous book, published in 1859, the term natural selection has been poorly understood, especially by non-specialists. Let’s review a few of the most frequent mistakes:

• Natural selection is a force that acts on living beings to cause evolution. This is not true. Natural selection is not a force, nor an object, nor an interaction, nor a phenomenon. It is simply a statistical observation. What is observed is the fact that, in general, individuals better adapted to their environment tend to leave more descendants than those less adapted. Nothing else. It is, therefore, a matter of common sense, not the result of the external action of a mysterious force.

Longevity and aging

Almost eight years ago I wrote a post on this topic in this blog, which contained a figure that I built starting from data provided by the Spanish Institute of Statistics, which showed mortality data for Spain in three different years: 1900, 1991 and 2013. The three curves in the figure represent the percentage of people who have reached a certain age and will die during the next year. I’m showing here an equivalent figure, with updated data that correspond to the years 1900, 1991 and 2022, as we now have more recent data.

As I said then, the figure shows that medical advances have reduced mortality, especially at the beginning and the end of life, but their effects are little noticeable for people between 20 and 40 years old. The mortality curve, which in 1900 was U-shaped, is approaching an inverted L, with a very low rate for almost all of life and a fairly abrupt rise after age 80.

Singularities

Hal 9000, from the film
2001, a space odyssey

A singularity is a mathematical concept applied to a function of a variable that reaches an infinite value for one or several finite values of its independent variable.

For example, the function y=1/x presents a singularity for x=0, since it is often said that 1 divided by zero is equal to infinity.