What is the theory of evolution?

Tree of Life

The theory of evolution, in its current form, asserts that the transformation of species (the evolution of life) depends on five factors:

1.      Spontaneous variations in the genome (mutations, genetic recombination, and other events that modify the genome).

2.      Spontaneous variations in the environment. This factor is often overlooked, as the environment is usually quite stable, although sudden changes sometimes occur that can have huge consequences.

3.      Inheritance, through which the variations that occur as a result of the first factor are passed on to offspring and are subject to the action of natural selection.

4.      Natural selection, which means that those individuals whose genome is best adapted to the environment will leave more offspring (at least statistically).

5.      The basic laws of the universe, which are currently represented by quantum theory and the theory of relativity.

Religious persecution of scientists?

William Harvey

This summer, Jesús Lizcano published an article in El Imparcial entitled. A memory for the scientists persecuted in history (my translation). He classifies the persecuted scientists into three groups: a) persecuted for political reasons; b) persecuted for religious reasons; and c) persecuted for reasons of sexual orientation. Here I am going to refer to those in the second group, which I find debatable.

Of course, among the eleven scientists persecuted for religious reasons, according to Lizcano, Hypatia and Galileo could not be missing. They are mentioned once and again, often with obvious exaggerations, as shown by the fact that many people believe that Galileo was burned alive by the Inquisition, when in fact he was sentenced to house arrest, softened over time. But here I am going to talk about the other nine mentioned in the article.

The Hubble-Lemaître Law

Georges Lemaître

Let us look at a little history.

In various places in the sky, but especially in the constellation of Cepheus, where the first case was discovered, there are some stars whose light intensity varies regularly, and therefore are called variable Cepheids. In 1908, the American astronomer Henrietta Swan Leavitt discovered that the period of these stars is linked with their real luminosity: the greater the luminosity, the longer the period. Therefore, by measuring their period, their real luminosity can be deduced.

In 1913, the American astronomer Vesto Melvin Slipher obtained the spectrum of what was then called the Andromeda nebula (the giant galaxy closest to ours) and discovered a blue shift that indicated (according to the Doppler effect) that the nebula moves towards us with a speed of about 300 kilometers per second, much higher than expected. Slipher then studied the light of other spiral nebulae and made the unexpected discovery that most of them, unlike Andromeda, show redshifts, that is, they move away from the solar system with great speed. In fact, he measured speeds above 1000 kilometers per second.

In 1919, the American astronomer Edwin Powell Hubble used the Mount Wilson telescope to photograph several spiral nebulae, including Andromeda, and showed that, actually, they were not nebulae, as had been believed, but huge clusters of stars. From then on they were no longer called nebulae, but galaxies, in honor of our Milky Way, which also belongs to the class of spiral galaxies. Galactos in Greek means milk.