Thursday, January 18, 2018

How the eye evolved

Let us reason about this problem by answering a few questions.
  1. Which part of the eye is most essential? The answer is obvious: the retina. If light cannot be detected, the remainder of the eye is useless.
  2. Can a retina, on its own, without the rest of the eye, play a useful role? Obviously, yes. Many groups of not too complex animals have ocelli, photo-receptor cells that just react to the presence of light, but cannot form images. Of course, perceiving the presence of light offers advantage against being totally blind. The proof of this: ocelli have appeared independently in at least 40 different animal groups.
  3. What is the next step? We also have traces among current animals. The Planaria is a Platyhelminth (flatworm) whose ocelli are located at the bottom of a concavity in its body. Thanks to this, the Planaria not only detects the presence of light, but also, to some extent, the direction it comes from. It is also obvious that being able to perceive the direction of light provides advantage to those who can, against those who cannot.

Thursday, January 11, 2018

The eye as an argument about evolution

Schematic diagram of the human eye
The vertebrate eye consists of five parts: cornea (a transparent insulating layer); aqueous humor; crystalline lens (a lens surrounded by muscles that make it possible to achieve a variable focal length); vitreous humor; and retina. The light passes through the cornea and the aqueous humor, is focused by the lens, goes through the vitreous humor and impacts on the nerve cells of the retina, which generate electric signals that the optic nerve transmits to the brain, which forms from them an image of the external world, where the light rays came from. The brain even turns the image around, as it is inverted when projected on the retina.
The complex structure of the eye has always been a problem for evolutionists, and an argument for those opposed to the theory of evolution. Darwin, in Chapter 6 of The Origin of Species, whose title is significant (Difficulties of the theory) dealt with the problem of the evolution of the eye in the following words:

Thursday, January 4, 2018

What happened to the predictions for 2017?

At the end of every year, many predictions are made about the following year. This applies especially to politics and the technological field. In this blog we are not interested in politics, so we’ll talk a little about technological predictions. What happened to those that were made for 2017 near the end of 2016? Have they been fulfilled?
This question is difficult to answer satisfactorily (with a yes or no), for those who make predictions usually do them on purpose in an ambiguous way, so the next year they’ll be able to say that they were right. For instance:

Thursday, December 28, 2017

The best 40 science fiction novels I have read

Blade Runner poster
Lists of favorite books have always existed, and with the rise of the Internet they have proliferated. That’s why I decided to make a new list (in case there were not enough). But what I’m showing here is not just the list of my favorite books in this genre, but something a little more complex.
To build the list, I started with four lists made by others, sometimes individually, sometimes collectively. For example, one of those lists has been created in Goodreads, the social network for books, is called Best Science Fiction and contains over 2,000 books. In order to build this list, the members of Goodreads vote (almost 1000 people have voted for at least one book), together with the book’s score and the number of people who have read it (in some cases several million).
To form my new list I used the following criteria:
  1. It just contains books that I have read.
  2. It does not contain books that I have read, but did not like at all (i.e. those I would assign one star in the Goodreads or Amazon ratings). As an example of these books I will mention Do androids dream with electric sheep? by Philip K. Dick. Its argument is based on an interesting idea, but the way it has been developed in the form of a novel is deplorable, sometimes absurd. This is one of the rare cases where the film based on a book (Blade Runner) turned out to be far superior to the original work.
  3. Therefore, if one of your favorite books is not listed here, it may be for three reasons: because I have not read it, because I did not like it at all, or because it didn’t come among the top 40 in the average of the lists I have used to build mine.
  4. It only contains science fiction books. The Lord of the Rings, for example, has not been included, although it is on one of these lists, because I don’t consider it science fiction.

Thursday, December 21, 2017

What really happened in the history of cosmology

To complete last week’s post, I will offer here a summary of the history of Cosmology, from the Greeks to the paradigm shift that took place in the sixteenth and seventeenth centuries.
The basic elements of Ptolemaic astronomy, showing a planet on an epicycle (smaller dashed circle), a deferent (larger dashed circle), the eccentric (×) and the equant (•).
  • Greek cosmology (with the exception of Aristarchus of Samos) put the Earth at the center of the universe. Plato and, above all, Aristotle established the idea that, since the sky is perfect, the orbits of the planets must be exactly circular, because, for them, the circumference is the most perfect curve of all.
  • The Greek model explained well the movements of the sun and moon, and therefore made it possible to predict eclipses, but had a problem with the retrograde movements of the planets then known (Mercury, Venus, Mars, Jupiter and Saturn). Three centuries before Christ, Apollonius of Pergamum proposed that the orbits of these planets are epicycles, circumferences centered on another circumference (the deferent), which in turn revolves around a point located near the Earth, but apart from its center (the eccentric).

Thursday, December 14, 2017

Was physics wrong in Ptolemy's cosmology?

1919 solar eclipse
A recent article in the journal Science News has this title: Eclipses show wrong physics can give right results. It claims that Ptolemy’s physics was incorrect, because he assumed that the Earth was at the center of the universe, and yet Greek science was able to predict the dates of eclipses.
According to the article, Ptolemy’s physics was less correct than the physics of Copernicus, who fourteen centuries later proposed that it was not the Earth, but the Sun, at the center of the universe.
The analysis in this article in Science News is completely wrong. Ptolemy’s physics was exactly the same as the physics of Copernicus. Copernicus did not propose a change in the physical theories that had governed classical astronomy since Hipparchus (2nd century BC). Copernicus just showed that, with a change in the coordinate system, and applying the same physics, the calculations are easier to perform. Logically, the same results are obtained.

Thursday, December 7, 2017

Automatic Learning

 Originally posted to Flickr as Comic-Con 2004
Terminator statue, CC BY 2.0
As I said in a previous article, automatic learning is one of the areas of weak artificial intelligence which has been object of research for at least 40 years. Strictly speaking, rather than a field of application, automatic learning is a methodology or technique used by other fields of application, such as neural networks, expert systems or data analysis. Automatic learning is divided into two main branches:
  • Supervised automatic learning, which has been used most frequently up to now. This post is dedicated to explain it.
  • Unsupervised automatic learning, related to the field usually called Data Mining. It has lately been widely advertised by the media in relation to a program (AlphaGo Zero) that, learning by itself, has reached a level comparable to the world champion of the game called Go (at the end of this post I’ll talk more about this).