Consequences of statistical ignorance

In a study performed a few years ago [1], the following problem was proposed to 18 expert consultants for AIDS patients:

Helen has tested positive for AIDS. How likely do you think she is really an AIDS patient? What would you advise her?

The input data are:

1.      The probability of having AIDS, when one belongs to a population without special risk, is 1 in 10,000.

2.      The sensitivity of the AIDS test is 99.9%. In other words, the probability of a false negative is 0.1%.

3.      The specificity of the AIDS test is 99.99%. In other words, the probability of a false positive is 0.01%.

The result of the study was as follows:

·         The 18 experts agreed that the probability that Helen is an AIDS patient is greater than 90%. Most thought that the probability is greater than 99%. Some even claimed that is greater than 99.9%.

·         All experts said that they would advise Helen to inform her family, make everybody test for AIDS, and start taking medication.

Science or speculation?

Merging of two black holes

In December 2013 several media made reference to an article published in the journal Physical Review Letters, in the field called quantum gravity, a set of mutually incompatible theories that in the last 30 years have scarcely formulated a single testable prediction, although they are usually presented as the latest in physics and give rise to news broadly popularized by the general media. This scientific news was presented by some media with this title: quantum entanglement causes the appearance of wormholes. Some of the reviews contained important mistakes. I’ll cite two:

1.      The group showed that, by creating two black holes intertwined, later separated, a wormhole appeared, a “shortcut”' through the universe, connecting the two distant black holes to one another.

Comment: the group did not show that. It just found some equations that suggest that this might happen (or not, because mathematics is not the same as physics). Moreover, these theoretical speculations are based on string theory, which is just one among several alternative proposals of quantum gravity existing today.

Happy anniversary

Tomorrow August 12th is the second anniversary of the opening of this blog on popular science. The Spanish version of the blog appeared a little earlier, on January 15th 2014. In these two years I have published over 100 articles, usually one per week, although I have interrupted publication during the summer, and slowed it somewhat in Christmas.

In this anniversary I want to take stock of what has been done so far, and the goals I imposed myself when I started this activity. The decision on whether I have achieved any of these goals is left open to the consideration and critical judgment of the readers.

Pirated eBooks, or just free eBooks?

"Treasure Island-Scribner's-1911" 

by N.C. Wyeth Beinecke Library

A headline in a major Spanish newspaper: Piracy increases. The text says: A survey shows that 56.6% of those who downloaded a book through the Internet did it without any payment... [In Spain] we are going backwards, because while in countries like France the number of pirated eBooks decreases year after year, here, however, it increased. Next door is another story where publishers complain of their falling sales.

In this context, we should notice a couple of widespread errors:

•         There is confusion between a free downloaded eBbook and a pirate eBook. Both things are quite different. For instance, when I bought my eBook reader, it came with a library of about 1000 files. (Books and files cannot be considered equivalent, for each story by Edgar Allan Poe, to give one example, was in a separate file). All these books were legal, because all of them were works out of copyright. Later on I have added many more: just now I have over 2000 volumes of classic books, downloaded from free sites like the Project Gutenberg, the University of Adelaide, epub Books, the Cervantes virtual library, Dominio Público, Livres Pour Tous, Ebooksgratuits, etc. All the books that can be downloaded from these sites are free, but all are legal. However, publishers (and the media who echo them) tend to count any freely downloaded book as a pirate book, because it does not provide them with any profit.

Political correctness attacks again

University of Bologna (1088)

Since the foundation of the Western universities, starting at the eleventh century, these centers soon became places for debate, where different topics of discussion were raised by two or more specialists who defended the different sides of the issue to be discussed, after which the audience could decide for one or the other position, or for both at once.

This debating function of the universities has persisted for many centuries (we are near turning a millennium). Now, however, political correctness, this new form of censorship, threatens to end this activity in the universities.

Consider the headline of the story:

Oregon State University Socratic Club Debate Cancelled

And the first paragraph:

The hollow Earth in pseudoscience and science

Cyrus Reed Teed (Koresh)

1870 saw the first appearance of a curious variant of the hollow Earth theory outside the literary field. The American Cyrus Read Teed proclaimed his belief that the Earth is hollow, but (here is the difference with previous theories) we live inside. Although the sea surface has been known for over two thousand years to be convex, and in spite of the arguments that led the Greek philosophers to assign the Earth a spherical shape, with ourselves on its outer surface, Teed was convinced that the Earth is really concave. The apparently infinite outer space would be a hollow bubble inside a universe made of rock. Teed changed his name to Koresh and founded a religion (Koreshanity) which reached several thousand followers, although they were scattered after his death in 1908.

Soon after, a German aviator named Bender, a prisoner in France during the First World War, read Teed publications and believed them. Bender developed these theories and asserted that the universe is an infinite mass of rock surrounding a bubble 13,000 kilometers in diameter, in whose inner surface we live. The atmosphere, 60 kilometers thick, thins up to the central vacuum, where three bodies move: the sun, the moon and the ghost universe, a ball of gas with shining points of light: the stars. When the ghost universe passes before the sun, it causes the alternation of day and night in the various regions of the inner surface of the Earth.

The hollow Earth in religion and literature

The idea that the interior of the Earth is hollow and inhabited is probably as old as man. In almost all ancient religions, the dead are the inhabitants of the hollow Earth. The origin of this belief may depend on the custom of burying the bodies, which dates back at least from the Neanderthals. Volcanoes and earthquakes also contributed to this idea, while caves plunging into the bowels of the earth seemed to be the entries to the underworld.

In ancient Egypt, survival after death was an obsession. At first the Pharaoh, as representative of the gods, was the only one who could achieve immortality, but the privilege was later extended to others. During the second millennium B.C.E., the democratization of the afterlife was complete. The dead were judged by a court of forty-two gods, presided by Osiris, the lord of the underworld. The next life was considered a simple continuation of this life. This is why they filled the graves with useful objects and statuettes of slaves and workers, which would play the role of servants, replacing the deceased person in the work to be done in the afterlife. But the dead Egyptians did not spend all their time underground. In the night, provided with a lantern, they would stroll around heaven: these were the stars.