Thursday, September 21, 2017

The Tunguska event

On June 30th, 1908, at dawn, a mysterious explosion took place in an almost uninhabited region of central Siberia. The explosion leveled 2000 km2 of taiga, uprooting about 80 million trees, which were left lying on the ground, away from the central point of the event, like the spokes of a wheel. The most probable theory considers the event as the impact of a meteorite or comet, although nobody could find the debris. Unlike other cases, as the Arizona Meteor Crater, no crater was found in the place of the event. As an explanation of these anomalies, it was concluded that the explosion of the celestial body took place at a high altitude (between 5 and 10 km). Taking into account the effects, it has been calculated that the energy released by the explosion would be in the span of 3 and 30 megatons. Recall that the most powerful nuclear weapon ever detonated (by the Soviet Union) was a 50 megatons hydrogen bomb, over 1000 times stronger than the Hiroshima bomb, which only released 20 kilotons. (One megaton equals 1000 kilotons). During the cold war, the Soviet Union boasted of possessing an even larger bomb (100 megatons) that they couldn’t use in Europe, as the effects of its explosion would reach their own territory.

Thursday, September 14, 2017

A few clarifications on the quantum revolution

First of all, let as clarify a few concepts, for recent news published in the media tends to encourage confusion.
·         Qubit: the quantum unit of information. While classical information is expressed in bits, which may take only the values 0 or 1, qubits are formed by superposition (or linear combination) of two quantum states, |0> and |1> (i.e. the horizontal or vertical polarization of a photon) and its value is: α|0>+β|1>, where α and β are two complex numbers called probability amplitudes.
·         Quantum Cryptography: It encrypts information through a protocol that takes advantage of the quantum properties of matter. The procedures devised so far can be deciphered by opponents using quantum procedures, but it is known (or believed) that they are impossible to decipher by classical means. The first quantum cryptography protocol, BB84, was proposed in 1984 by Charles Bennett and Gilles Brassard of IBM.

Thursday, September 7, 2017

Medical Dietetics, Science or Fashion?

Food containing magnesium
The advices given by medical dieticians about healthy food oscillate continuously as time goes by. They rather look like the alternatives of fashion, than the discoveries of science. Here are a few examples:
         In the fifties and sixties it was fashionable to disparage the consumption of olive oil and recommend the use of seed oils, supposed to be healthier. Heart patients were advised to consume various seed oils, while olive oil was not even mentioned. Sometimes it was asserted that the consumption of olive oil increases cholesterol in blood. This policy caused significant damage to Spain, one of the main olive oil exporters, as stated in a newspaper article published in 1968:
The economic problems of the olive grove are motivated, to a great extent, by the change in the taste of the consumers, who sometime ago were forced to use different seed oils, and now, when we are trying to bring them back to a higher consumption of olive oil, they don’t want to do it in the proportion advisable for this market of the Spanish fruit, as it is rather more expensive.