Mariano Rajoy, al contrario de lo que muchos puedan pensar, es un gran ejemplo de método científico y de como trabaja la ciencia desde hace mas de 400 años ... ¿o tal vez no? La importancia de la búsqueda bibliográfica en ciencia. La Ciencia lleva cuatrocientos años cambiando nuestra sociedad a pasos agigantados. Eso es posible por que se basa en un método de rigor y verificación que nos permite entender y describir la naturaleza de manera satisfactoria. Isaac Newton decía que el vio mas lejos por estar a hombros de gigantes. Con esto describió muy bien como trabajamos en ciencia. Los descubrimientos que hacemos hoy en dia son posibles por que basamos nuestras investigaciones en las de científicos que nos precedieron. Esto nos permite avanzar. El propio Newton se encontró que, para describir la Naturaleza, necesitaba unas herramientas matemáticas que no existían, el calculo infinitesimal. Tuvo que introducirlas. Hoy en dia aprovechamos sus aportaciones y la de miles de científicos para nuestras investigaciones especializadas. Por eso, en un articulo científico, es importante explicar bien la motivación de nuestra investigación y citar a aquellos trabajos en los que nos hemos basado. Nuestro trabajo es novedoso pero no hubiese sido posible sin otros. En el siguiente video, el sr. Rajoy no ha hecho una buena búsqueda bibliografica. De haber sido así, de haber consultado a un estudiante de tercero de primaria, hubiese sabido del ciclo del agua. La falsabilidad en ciencia. Parte de la opinion publica piensa que la ciencia es rígida y no se puede cuestionar. Nada mas lejos de la realidad. Una característica de la ciencia, que la hace muy poderosa, es que los científicos aceptamos los resultados experimentales y los argumentos que las explicaciones. Por muy extraña que parezca una teoría científica, si explica y esta de acuerdo con las observaciones y los experimentos, aceptaremos esa teoría. Eso si, cuanto más anti-intuitiva sea la teoría, mas robustas y concluyentes han de ser las evidencias. A veces aparecen resultados que contradicen una teoría bien aceptada. Ocurrió con la física de Newton cuando apareció la relatividad de Einstein. Eso no significo que Newton estuviese equivocado. Hay teorías que funcionan bajo ciertas condiciones, son excelentes aproximaciones en dichas circunstancias. Pero si las condiciones cambian hemos de adoptar una teoría mas general, que englobe a la anterior (la relatividad de Einstein engloba a la de Newton). Por eso es importante explicar las condiciones en que se hacen los experimentos y explicar donde tu experimento ha sido diferente de los anteriores. Por otra parte, si en ciencia alguien falsifica resultados, como hay muchos científicos trabajando en cada campo, alguien, tarde o temprano se dara cuenta de dicho fraude y la mala praxis sera denunciada. Como en esta comparecencia: La importancia del uso de los términos correctos y el redactado claro. Hace unos anos, en un congreso de comunicación científica, algunos asistentes se quejaban de que los científicos escribían para que nadie les entendiese. A mi a veces me lo ha parecido, con algún que otro paper. Pero esto no es así. Es muy importante utilizar los términos correctos, las palabras precisas y rigurosas. Pero por otra parte, tambien nos interesa que el lector (normalmente otro científico del ramo) entienda bien lo que hemos hecho y cuales son nuestros descubrimientos. De esta manera conseguimos hacer difusion de nuestro trabajo y que contribuir a construir ciencia. En la carrera o el doctorado hay muy pocas oportunidades de aprender a redactar de manera clara, diafana, pero rigurosa y concreta a la vez. Si no se logra, nuestro lector podrá malinterpretar nuestro trabajo o llegar a conclusiones equivocadas. Un gran ejemplo es este: La importancia de definir nuevos conceptos y de referenciar las fuentes. Todos los trabajos científicos que se publican tienen algún aspecto novedoso. Pero, como ya mencione anteriormente, tambien todos están basados en trabajos anteriores. Cuando necesitamos utilizar algún concepto, algún resultado, alguna metodologia, introducida por otro científico, hemos de referenciar muy claramente dicha fuente. A su vez, si un científico ha introducido un método muy concreto, que estamos utilizando, es bueno hacer una pequeña descripción para que el lector pueda seguir leyendo nuestro articulo, sin tener que leer toda la bibliografia a que hacemos referencia. De esta manera agilizamos la lectura y facilitamos que se nos entienda. Un ejemplo muy claro es el siguiente: Referencias a futuras investigaciones. Es poco común que un trabajo científico cierre un ciclo de investigaciones. Siempre se abren puertas y siempre quedan aspectos que investigar, o condiciones donde verificar los nuevos hallazgos. Es por eso que es común encontrar, al final de un articulo científico, sugerencias de futuros trabajos, o trabajos en marcha, de los autores. Esto puede dar pistas e ideas a otros grupos para ampliar las investigaciones. Otras veces se trata de preguntas abiertas que deja tu investigación, para las que quizas aun no tengamos las herramientas para responder. ¿O sí? La importancia de que queden los conceptos claros. Cuando estas presentando unos resultados novedosos, o definiendo un concepto nuevo, es importante que le dediques mucho tiempo a saber como lo vas a escribir, de tal manera que no queden dudas, que quede claro, que sea entendedor. Que quede toda la información, y que cualquier otro científico pueda repetir tu experimento o tus calculos. Por eso, a veces conviene hace repaso de ideas previas. Eso si, sin ser demasiado redundante, pues esto puede hacer pesada su lectura, verdad? La ciencia es maravillosa, nos sorprende y nos hace disfrutar al mismo tiempo. May the Science be with you.
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The detectors of gravitational waves, LIGO, have again felt a shudder in space-time. The event, merger of two black holes, has emitted as much energy in just one second as the whole the universe For the second time in three months, LIGO detectors have detected gravitational waves, from the merger of two black holes. These exotic astronomical objects, in an accelerated dance, rotating around each other at a rate of about 55 revolutions per second, have been merged into a final black hole, of 21 solar masses. In this process they have emitted an enormous amount of energy. In one second they have released as much energy as if the whole mass of the Sun was transformed into energy in that fraction of time, or equivalently, the energy emitted by all the stars in the universe in that second. Gravitational waves were predicted by Albert Einstein in 1916, and were first detected a few months ago. These waves distort space and time. In order to do this, it is required an energy that only the most exotic objects in the universe can deliver. Another source of gravitational waves was the Big Bang itself. But when these waves reach our detectors on Earth (1.4 billion light years in this case), they arrive so weakened, that they are extremely difficult to detect. The required measurement is equivalent to measuring the distance between the Earth and the Sun with an accuracy of a few atoms. When gravitational waves traverse the Earth, or its detectors, or you and me, they expand and contract the distances between atoms. These oscillations they create are related to the movement of the two black holes that originated them. The intensity of the oscillations, their frequency and their evolution, can give us a lot of information from the event. The announcement of the first detection was the starting point of gravitational wave astronomy. Until then, all information from the universe came though electromagnetic waves: light. We now have another source of information, another way to scan the cosmos. This new window can reach where light does not reach. With gravitational waves we can see black holes, and maybe we can get to watch the Big Bang. This new detection, the second in three months, begins to indicate how many of these phenomena are taking place in the Universe, and will help us to determine the density of black holes in the universe. This is important for models of galaxy evolution and to extend our knowledge of the history of the universe. We are witnessing a new era in astronomy. we are beginning to fell the shudders of the Universe, a if we were Darth Vader feeling the presence of the force. We have already detected gravitational waves. The rumors of the news were in the air for a few weeks and finally the researchers (from the MIT, Caltech and the LIGO project) have announced their finding Special Relativity: one century of interferometry One of the most common ways to introduce special relativity is by describing the interferometry experiment of Michelson and Morley from the late 19th Century. Their negative result was pointing to a fundamental problem in the interpretation of space and time. Even though Albert Einstein didn't use their result to present his special theory of relativity, the experiment was one of the most precise experiments of all times, and it is a pedagogical tool. Michelson designed an interferometer to measure the drag of the "luminiferous aether" on the speed of light. This aether was a supposed fluid that filled all space and was introduced in order to explain the wave nature of light. In his experiment, Michelson first and with Morley later, compared the time that light needed to travel along two perpendicular paths, as in the figure. The light was coming from the left (see figure). A beam splitter divided the beam of light into two. One half going to Mirror 2 and the other half to Mirror 1. Then those beams were reflected. They interfered at the beam splitter again and recombined, being sent to the detector. Depending on the difference in time the interference pattern can be different, and from this we can extract the difference in velocity, if any. As light has undulatory behavior the interference between two pulses or beams of light depends on their relative phases. This phase will depend on the difference of path taken by each beam. The problem shown in this experiment was that, contrary to the general belief, there was no aether, and the way to explain some contradictory results was to assume that space and time are distorted as seen from different observers that move one with respect to the other: if a traveler flies at very high speeds (comparable to that of light), time for the traveler passes much slowly than for an observer at rest. Also, space seen by the traveler gets contracted. This is a direct implication of two principles: - The speed of light is constant (has an absolute value). It is the same for all observers, independently of the velocity of the observer with respect to the source that emitted the light. - All inertial reference frames (those with constant velocity but no acceleration) are equivalent. We can not design an experiment to tell us if our reference frame is at rest or it moves with uniform motion (constant velocity in magnitude and direction). All the laws of physics are the same for all observers. General Relativity But the Special Theory of Relativity of 1905 didn't account for gravity. After almost a decade later 9in 1915), Albert Einstein presented his general theory of relativity, which described gravity. This theory introduced the idea of curved space-time. Einstein introduced a geometric description of space and time in 1905 and he showed that space and time formed a continuum four dimensional tissue where all matter in the universe is immersed. Matter deforms the space-time fabric and the distortion of space-time shows the matter and light how/where they have to move. The Universe is full of matter that gravitates and distorts space-time as it flies by. It is like playing bowling in a green that is not uniform, but also, it changes shape as the bowls roll by. But an indirect observation of gravitational waves had already been made in the late 1990s. General Relativity predicts that a fast spinning neutron star will emit energy in for of gravitational waves. This lost of energy will be reflected is the rotational energy of the star. Detailed observations through thirty years confirmed that the rotational energy lost was exactly the one predicted by General Relativity to be emitted as gravitational waves.Gravitational waves All the predictions of general relativity have been confirmed. Gravitational lensing, or how gravity changes the straight lines and makes light travel in curved trajectories. gravitational time dilation, or how gravity makes clocks travel slower, so that a person in a intense gravity field will experience less time lapse than a person far from an intense gravity field. Gravitational redshift, or how light looses energy due to gravity by changing its wavelength. Gravitational waves was the last prediction to be directly observed. This waves are created when cataclysmic phenomena happen in the universe, such as collision of black holes or coalescence of neutron stars. Even though the energy released in these phenomena are huge (about two solar masses in the gravitational waves observed by LIGO), when we detect them (so far away, luckily) they are really tiny. Interferometry to the rescue. But to measure the Gravitational Waves we need to measure tiny, very tiny variations in the distance between atoms, as the waves traverse them. It is like measuring the distance from the Sun to Proxima Centaury (~4light years) with a resolution of one human hair! To do this, physicists form the LIGO project have used a Michelson interferometer (yes, again the same experiment Michaelson did in 1887). In this case, though, it was not a tabletop experiment. The two arms of the interferometer were four kilometers long. This has to be this way so that the distance of the mirrors are change enough to be detected (one thousandth of the size of the proton). In order to be sure that what was measured were really Gravitational Waves, the experiment counted with two different interferometers, one in the state of Washington and the other in the state of Louisiana. They are far enough so that any local perturbation measured in one of them is not detected by the other. Also, the time difference between detections can hive hints on the origin of such waves. In September, 14th, 2015, both interferometers detected the same signal, almost simultaneously. The signal had the specific frequency pattern predicted by General Relativity for two merging black holes, and could not be attributed to any other phenomena. The first ever Gravitational Wave had been observed. This detection technique, not only confirms once more Einstein's Relativity, but opens a new window to the Universe. We can now observe it not only with electromagnetic waves, but also with gravity waves. In Terrassa (Spain) the Association Planeta da Vinci, together with the Astronomical Association of Terrassa, are organizing the 9th Dissemination Day on Relativity. They have been creating a meeting point between Scientists, Science Communicators and Society since 2008. The journal Physical Review Letters publishes this month my last paper in complex dynamics in optical systems: “Unveiling temporal correlations characteristic of a phase transition in the output intensity of a fiber laser”. This work is in collaboration with scientists from Spain [1], UK [2] and Russia [3]. In it, we unveil underlying correlations and time-scales in the intensity fluctuations of a fiber laser in its transition to a turbulent regime. Fiber lasers are widely used in industry, and very attractive due to their high gain, high output power or high optical quality. But wave dynamics in fibre lasers is highly complex as result of the non-linear interaction of millions of elements. Recently, the group of Aston University (the lab. of Sergei Turitsyn) found similarities between this type of laser and fluids. They showed the analogy between optical regimes in fiber lasers and the transition from a laminar to a turbulent regime in hydrodynamics. We have applied complex dynamics techniques to study this transition and we reveal clear correlations in time and in laser intensity. We have identified temporal structures that evolve with, and characterize the transition between the two dynamical regimes. These techniques are shown to be powerful tools and can also be used to study high-dimensional complex systems that undergo similar transitions. Probabilities of six different temporal (a) and intensity (b) patterns that evolve as the pump power of the laser varies from 0.8 Watts to 1.5 Watts. The transition is at 0.9 Watts. If the dynamics was stochastic, random, all six patterns should be equally probable. Right around the transition we see how the behavious is more deterministic, more structured. he result of our research helps us understand the laminar to turbulent transition, present in fiber lasers but also in fluids, such as a liquid in a pipe. We have also found a more structured behaviour right at the transition than in the laminar or turbulent regimes. This helps understand the flow of fluids at the transition, which will help for fluid transport purposes (water in a tube, gas in a pipeline or light in an optical fiber). We have also found characteristic intrinsic time scales where the system shows random behaviour and time scales with a more structured behaviour. This will be useful in long distance telecommunications, one of the applications of this type of lasers. This time scales could point out interesting frequencies for transmission. Our work helps understand better light-matter interactions in these lasers, which are very complex as millions of laser modes interact, due to their very long cavity. This work can also help to verify and/or improve models used to capture the essence of the transition, and to estimate the model parameters for this type of lasers. There are still some aspects to understand in these systems, such as the origin of the intrinsic time scales, and what type of nonlinear interactions created pulses with this dynamics. [1] Universitat Politecnica de Catalunya (Laura Carpi, Carme Torrent and Cristina Masoller) [2] Aston University (Sergei Turitsyn, Nikita Tarasov and Dmitry Churkin) [3] Novosibrisk University (Nikita Tarasov and Dmitry Churkin) A long time ago, in a galaxy far, far away ... Here it comes the new film of the saga Star Wars, The Force Awakens. Ready to make us enjoy and dream. Full of technology, adventures, and ready to show us the Galaxy. All united with the force. The force, ... Where is the force in Nature? Can the Jedi can fell the force, if they can use it, our devices should be able to detect them. Shouldn't they? In order to try to understand what should be the force in the landscape of Science I will remind the definition Master Obi Wan gave to Luke in the first movie. "The force is what gives the Jedi its power. It's an energy field created by all living things. It surrounds us, it penetrates us. It binds the galaxy together." He is talking about an energy field that surrounds us, penetrates us and binds the galaxy together. There are two things in the Universe that could respond to that description, and both come from the dark side: dark energy and dark matter. These two dark concepts are not really well known nowadays. But we do know that they constitute 69% and 27%, respectively, of the content of the Universe. The dark side rules the Galaxy They both are distributed all through the Universe, although dark matter is attractive gravitationally, therefore forming lumps, while dark energy is uniformly distributed and repulsive. In any case, neither of them has been directly detected yet. Dark energy was postulated in the late XX century in order to explain the accelerated expansion of the universe, observed in 1998. It should be some sort of repulsive pressure that pulls the Universe apart, making it grow faster and faster. But dark energy does not bind the galaxy together. If it continues as it is doing now, dark energy will pull the universe so intensely that it will break it apart, tearing galaxies apart. Dark energy can not explain the force. In the case of dark matter, the most likely candidate are the so-called Weakly Interactive Massive Particles (WIMPs). These are described as very heavy particles that don't interact through the electromagnetic force. This lack of interaction makes dark matter be almost undetectable (it has not been up to date, although there are efforts in this direction). Neutrinos were candidates for dark matter at some point, but they can only account for 1% of the content of the Universe. Just as neutrinos are doing right now, dark matter should be penetrating us without us noticing it. Dark matter is attractive gravitationally, unlike dark energy. Indeed, this was the first clue to identify its existence in the 1930s. The movement of galaxies, for example, can't be explained with the amount of matter we observe from stars, and it is needed the existence of extra matter to explain it satisfactorily. Also, dark matter is necessary to explain galaxy formation. Without it , probably galaxies wouldn't have formed the way they did. So, yes, dark matter surrounds us, penetrates us, and binds the galaxy together. Is dark matter the Jedi force? Well, if dark matter exists, which a few astronomers do not agree, it should penetrate the ordinary matter that we all are made of: atoms. But it should penetrate living creatures as well as water, rocks, or even stars. Or, ... Obi Wan could be referring to baryonic matter (made out of atoms) when he said living. In a poetic form he could be talking about the matter that we can see, the matter that can create living things (4.9% of the content of the Universe) as living things. May a Jedi use the force? The way we interact with things is through the forces, that is right. But these forces are the electromagnetic force, the gravitational force, the weak nuclear force and the strong nuclear force. The two first are long range interactions while the two nuclear forces are very short range, just the size of atoms. But we are all made out of atoms, so whatever sensor the Jedi has to detect the force (if it is dark matter or not) we should be able to build detectors made out of atoms to detect it too. And we can't detect dark matter (if this is the force), yet. In the Fantom menace, Qui-Gon Jinn talks about midiclorians, some microscopic creatures that live inside us and are the link between the Jedi and the force. It doesn't matter how long ago and how far the galaxy is, the laws of Nature work here and there, now and then. We should be able to detect it here, in our laboratories. If you want to imagine that dark matter was detectable millions of years ago, and it then decoupled from electromagnetism, we should have already seen it in our laboratories, and there should be signatures of that in the observable Universe, which is not the case. The Universe needs about 7 million years to create life as we know it (or as the one that appears in Star Wars). When the Universe was that age, the temperature of the Universe was very similar to the one we have now. Nature was following the same rules it follows now, and the conditions were the same we find now. The more exotic situation of the first minutes of the Universe had passed long before.
Lots of efforts are focussed nowadays to detect dark matter, and most groups think they will detect it in the next decade or so. Maybe they should include biologists in their ranks to find it earlier. In any case, may the Science be with you. |
Andrés AragonesesPhysicist, working in quantum optics and nonlinear dynamics in optical systems. Loves to communicate science. Archives
January 2018
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