Las ecuaciones del electromagnetismo y una tatarabuela de Maxwell

El físico escocés James Clerk Maxwell nació el 13 de junio de 1831 en Edimburgo en el seno de una familia acomodada. Su vida transcurrió durante la consolidación de la revolución industrial en Gran Bretaña, en la era victoriana y en pleno auge del Imperio Británico, en una sociedad cambiante con una expansión demográfica sin precedentes.

Al leer “James Clerk Maxwell”, y siguiendo la costumbre anglosajona de mantener sólo un apellido, el del padre, probablemente pensamos que su nombre es compuesto, “James Clerk”, y su apellido es “Maxwell”. Sin embargo, realmente su primer apellido no era “Maxwell”, sino “Clerk” (de los “Clerk” de Penicuik) y además el apellido de su madre era Cay (de los “Cay” de Northumberland). Lo que sucedió es que su bisabuelo George Clerk (cuarto Baronnet) se casó con su prima Dorothea, cuya madre se llamaba Agnes Maxwell (de los “Maxwell” de Midelbie), y al heredar las fincas de la familia Maxwell, y por temas legales, añadió “Maxwell” a su primer apellido “Clerk”, quedando su apellido desde entonces como “Clerk Maxwell”, que además sólo llevaban los que heredaban las fincas de Midelbie de los Maxwell. Los demás hijos, incluido el hijo mayor que heredaba las propiedades de los Clerk en Penicuik, eran sólo “Clerk”.

En conclusión, las ecuaciones del electromagnetismo llevan el nombre del primer apellido de una tatarabuela de Maxwell.

BIBLIOGRAFÍA

J. C. Maxwell’s Heritage: the Ancestral Origins of his Genius

J. M. Sánchez Ron, J. M. (ed.), J. C. Maxwell: Materia y movimiento (Crítica. Barcelona, 2006)

J. Gabàs, La naturaleza de la luz: Maxwell. (Nivola Libros y Ediciones. Madrid, 2012)

A. Beléndez, “Mi clásico favorito: James Clerk Maxwell”, Revista Española de Física, Vol. 30, Nº 3, pp. 62-73 (2016)

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Las ecuaciones de Maxwell

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The laser turns 60!

In 1960 the laser, one of the most important and versatile scientific instruments of all time, was invented. It was on 16 May 1960, that the North American physicist and engineer, Theodore Maiman (1927-2007), obtained the first laser emission.

Press Photo Dr. Theodore H. Maiman with his new laser device in New York (July 7th, 1960).

This date is therefore of great importance not only for those of us who carry out research in the field of optics and other scientific fields, but also for the general public who use laser devices in their daily lives. CD, DVD and Blu-ray players, laser printers, barcode readers, and fibre-optic communication systems that connect to the worldwide web and Internet are just a few of the many examples of laser applications in our daily life. Lasers also have a range of important biomedical applications; for example they are used to correct myopia, treat certain tumours and even whiten teeth, not to mention the beauty clinics that continually bombard us with advertisements for laser depilation, which has become so popular nowadays. However, the laser is of great importance not only due to its numerous scientific and commercial applications or the fact that it is the essential tool in various state-of-the-art technologies but also because it was a key factor in the boom experienced by optics in the second half of the last century. Around 1950 “optics was widely considered a somewhat dull discipline with a great past, but without prospects of a great future” (Kragh, 2002). At that time, the most prestigious journals were full of scientific papers from other branches of physics. However, this situation changed dramatically thanks to the laser which led to a vigorous development of optics. It is indisputable that the laser triggered a spectacular reactivation in numerous areas of optics and gave rise to others such as optoelectronics, non-linear optics or optical communications.

This date is therefore of great importance not only for those of us who carry out research in the field of optics and other scientific fields, but also for the general public who use laser devices in their daily lives. CD, DVD and Blu-ray players, laser printers, barcode readers, and fibre-optic communication systems that connect to the worldwide web and Internet are just a few of the many examples of laser applications in our daily life. Lasers also have a range of important biomedical applications; for example they are used to correct myopia, treat certain tumors and even whiten teeth, not to mention the beauty clinics that continually bombard us with advertisements for laser depilation, which has become so popular nowadays. However, the laser is of great importance not only due to its numerous scientific and commercial applications or the fact that it is the essential tool in various state-of-the-art technologies but also because it was a key factor in the boom experienced by optics in the second half of the last century. Around 1950 optics was considered by many to be a scientific discipline with a great past but not much of a future. At that time, the most prestigious journals were full of scientific papers from other branches of physics. However, this situation changed dramatically thanks to the laser which led to a vigorous development of optics. It is indisputable that the laser triggered a spectacular reactivation in numerous areas of optics and gave rise to others such as optoelectronics, non-linear optics or optical communications.

Ten years ago, on the occasion of the celebration of the 50th anniversary of the laser’s invention, President Barack Obama sent a presidential message to the founding partners of LaserFest, a yearlong initiative created to celebrate the 50th anniversary of the first working laser, recognizing it as “one of the most important and versatile inventions of the 20th century.” In his message, President Obama recognized the “intensely creative theoretical work” that led to the development of the laser, “followed by innovative engineering and a spectacular diversity of applications that have brought economic benefits unimagined at the start of the process.” He went on to say he looks forward “with real excitement to further advances in this field and new applications as yet undreamed of today.”

What is a laser? 

It is a device capable of generating a light beam of a much greater intensity than that emitted by any other type of light source. Moreover it has the property of coherence, which ordinary light beams usually lack. The angular dispersion of a laser beam is also much smaller and so when a laser ray is emitted and dispersed by the surrounding dust particles it is seen as a narrow straight light beam. But let us leave to one side the specialized technical points, more suitable to other types of publications, and concentrate on aspects of the invention of the laser which are no less important and no doubt of greater interest to the general public. The word laser is actually an acronym for “Light Amplification by Stimulated Emission of Radiation” and was coined in 1957 by the American physicist Gordon Gould (1920-2005), working for the private company Technical Research Group (TGR), who changed the “M” of Maser for the “L” of Laser. In the image below, the phrase “some rough calculations on the feasibility of a LASER: Light Amplification by Stimulated Emission of Radiation” may be seen (Gordon Gould’s manuscript, 1957).

First page of Gordon Gould’s 1957 lab notebook where he defines the term ‘laser’. Credit: (AIP Emilio Segre Visual Archives.

The origins of the development of the laser may be found in a paper by Albert Einstein (1879-1955) on stimulated emission of radiation in 1916 («Strahlungs-emission und -absorption nach der Quantentheorie», Emission and absorption of radiation in Quantum Theory). But it was an article published on 15 December 1958 by two physicists, Charles Townes (1915-2015) and Arthur Schawlow (1921-1999) titled  “Infrared and Optical Masers” that laid the theoretical bases enabling Maiman to build the first laser at the Hughes Research Laboratories (HRL) in Malibu, California in 1960. Maiman used as the gain medium a synthetic ruby crystal rod  one centimeter long with mirrors on both ends and so created the first ever active optical resonator. It is probably not general knowledge that the Hughes Research Laboratories was a private research company founded in 1948 by Howard Hughes (1905-1976), eccentric multimillionaire, aviator, self-taught engineer, Hollywood producer and entrepreneur, played by Leonardo DiCaprio in the film “The Aviator” directed by Martin Scorsese in 2004.

The executives of the Hughes Research Laboratories gave Maiman a deadline of nine months, 50,000 dollars and an assistant to obtain the first laser emission. Maiman was going to use a movie projector lamp to optically excite the gain medium but it was his assistant, Irnee D’Haenes, who had the idea of illuminating the ruby crystal with a photographic flash.

Charles H. Townes (left) and Arthur Leonard Schwalow (right). Nobel Museum, Stockholm. Credit: Augusto Beléndez.

When he obtained the first laser emission, Maiman submitted a short article to the prestigious physics journal the Physical Review. However, it was rejected by the editors who said that the journal had a backlog of articles on masers –antecedent of the laser in the microwave region and so had decided not to accept any more articles on this topic since they did not merit prompt publication. Maiman then sent his article to the prestigious British journal, Nature, which is even more particular than the Physical Review. However it was accepted for publication and saw the light (excuse the pun) on 6 August 1960 in the section Letters to Nature under the title “Stimulated Optical Radiation in Ruby”, with Maiman as its sole author. This article which ran to barely 300 words and took up the space of just over a column may well be the shortest specialized article on such an important scientific development ever published. In a book published to celebrate the centenary of the journal Nature, Townes described Maiman’s article as “the most important per word of any of the wonderful papers” that this prestigious journal had published in its hundred years of existence. After Maiman’s article was officially accepted by Nature, the Hughes laboratories announced that the first working laser had been built in their company and called a press conference in Manhattan on 7 July 1960.

In a very short time the laser stopped being a simple curiosity and became an almost unending source of new scientific advances and technological developments of great significance. In fact the first commercial laser came on the market barely a year later in 1961. In the same year the first He-Ne lasers, probably the most well known and widely used lasers ever since, were commercialized. In these early years between 1960 and 1970 none of the researchers working on developing the laser –the majority in laboratories of private companies such as those of Hughes, IBM, General Electric or Bell- could have imagined to what extent lasers would transform not only science and technology but also our daily life over the subsequent 60 years.

On May 16, 2020, we  celebrate the 60th Anniversary of Maiman’s monumental accomplishment in conjunction with the International Day of Light.

He-Ne laser illuminating an optical set-up made using two holographic lenses in the old Optics laboratory placed at the University of Alicante. This university was one of the pioneer universities in Spain in the application of laser to research. / Augusto Beléndez, Variable holographic filter (1988).

“55th anniversary of the laser’s invention”: Published in IYL2015 BLOG (May 27th, 2015)

 

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Why celebrate an International Day of Light?

Humans have always felt –and still feel– fascination for light, mainly thanks to those magnificent organs of the human body which are the eyes. Luminous phenomena such as rainbows, aurora borealis, sundogs, Fata Morgana or just the rising and the setting of the Sun still amaze us as they did our ancestors before us. The truth is that light affects every day of our lives. Clearly, the light emitted by the Sun plays a fundamental role in the development of life on Earth and it is the main source of energy for our planet. If someone asks «what do we get from the Sun?» we immediately answer: «light and warmth» and some might even add «ultraviolet light», from which – luckily for our health– the Earth’s atmosphere protects us to a greater or lesser extent. However, they are not really three different things, but one and the same: energy in the form of electromagnetic waves with wavelengths corresponding to visible, infrared and ultraviolet radiations, which produce different effects and sensations.

Following a highly successful International Year of Light 2015, which highlighted the importance of light-based sciences and technologies and saw more than 13,168 activities implemented in 147 countries, the Executive Board of UNESCO, at its 200th session, established the International Day of Light on 16 May of every year (200 EX/Decision 27). The 39th General Conference has approved this decision in document 39 C/40. This International Day highlights the fundamental role of light and its technologies in all human activities. Light is at the origin of life, it has inspired beauty, painters, poets, architects… and is essential to photography, cinema, theatre or television because there is no doubt that light affects the emotional response of the audience. We just need to look around us to verify that the numerous applications of light in science, engineering, architecture, medicine, communications, culture, art and leisure have revolutionized society.

The International Day of Light is a global initiative that provides an annual focal point for the continued appreciation of light and the role it plays in science, culture and art, education, and sustainable development, and in fields as diverse as medicine, communications, and energy. The broad theme of light will allow many different sectors of society worldwide to participate in activities that demonstrates how science, technology, art and culture can help achieve the goals of UNESCO – education, equality, and peace.

The industries related to light are true economic engines and with the invention of the laser –one of the most important and versatile scientific instruments– Optics and photonics are increasingly meeting the needs of humanity in multiple aspects. They give access to information, facilitate our communications, help to preserve our cultural heritage, promote sustainable development and enhance health and social welfare. Light–based technologies are also providing new solutions to various global issues in areas such as energy, education, agriculture, environment and health. However, excessive light may sometimes have adverse consequences. Light pollution has become one of the biggest problems in developed countries since it not only affects astronomical observations –the Milky Way is no longer visible in the night sky–, but also birds, insects, turtles and other nocturnal creatures, not to mention the tremendous waste of energy involved. There is no doubt that the study of light and light–based technologies has become a cross-cutting discipline of science and technology in the 21st century. For this reason, it is essential that we be fully aware of the importance of the scientific study of light and the application of light-based technologies for sustainable global development. This requires public and private investment to develop research projects in different fields related to light and technologies. In the same way that the 20th century has sometimes been called the century of electronics, perhaps the 21st century will be known as the century of light, mainly due to the advances in optics and photonics that have taken place in the last sixty years.

But, why May 16th? The answer is that May 16th is the anniversary of the first successful operation of the laser in 1960 by physicist and engineer, Theodore Maiman. The laser is a perfect example of how a scientific discovery can yield revolutionary benefits to society in communications, healthcare and many other fields. However, the International Day of Light is not just about lasers and science. It also includes aspects of art, culture, entertainment – everywhere light is present in fact! This day is a call to strengthen scientific cooperation and harness its potential to foster peace and sustainable development. This May 16th, 2020, in addition, we celebrate the 60th Anniversary of Maiman’s monumental accomplishment in conjunction with the International Day of Light

In 1917 Albert Einstein declared: «for the rest of my life I will reflect on what light is.» Every May 16th of each year, millions of people around the world will reflect on how wonderful light is and the many ways in which light and light–based technologies can improve our lives.

International Day of Light 16 May Official Video

Terrassa to hold the 2020 Central IDL Event in Spain.

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Los diez experimentos más bellos de la Física

En el año 2002 Robert P. Crease, historiador de la ciencia, preguntó a los lectores de la revista Physics World (donde escribe una columna desde el año 2000 titulada critical point) cuáles eran, en su opinión, los experimentos más bellos de la física. Para confeccionar la lista escogió los diez experimentos que fueron citados por los lectores con mayor frecuencia. Su “lista” se publicó en la revista Physics World, pero de allí la noticia saltó a las páginas de The New York Times el 24 de septiembre de 2002 y en España fue el diario El País el que dedicó mayor atención a la “noticia” en su edición del 23 de octubre de 2002. ¿En qué radica la “belleza” de estos experimentos? Seguramente la respuesta es que el denominador común de la mayor parte de ellos es la gran simplicidad de medios para su realización y que desde luego todos tuvieron una gran capacidad de cambiar el planteamiento dominante en su tiempo que ofrecieron sus conclusiones. Además, casi todos los experimentos de esta lista de los diez más bellos fueron realizados individualmente o, como mucho, con la ayuda de unos pocos colaboradores, y en un plazo de tiempo relativamente corto. El orden del resultado de la encuesta, por número de votos, fue el siguiente:

  1. Interferencia de los electrones al pasar por una doble rendija (Bohr, De Broglie, Heisenberg et al.)
  2. Caída libre de los cuerpos (Galileo)
  3. Determinación de la carga eléctrica del electrón (Millikan)
  4. Descomposición de la luz del Sol por un prisma (Newton)
  5. Interferencia de la luz por la doble rendija (Young)
  6. Medida de la constante de la gravitación universal con una balanza de torsión (Cavendish)
  7. Medida del radio de la circunferencia de la Tierra (Eratóstenes)
  8. Caída de un cuerpo por un plano inclinado (Galileo)
  9. Descubrimiento del núcleo atómico (Rutherford)
  10. Movimiento de la Tierra (péndulo de Foucault)

El experimento que quedó en el undécimo lugar fue el principio de Arquímedes de la hidrostática (ver vídeo), seguido por el método de Römer para la medir la velocidad de la luz. Otros experimentos considerados “bellos” fueron el experimento de Michelson y Morley o la experiencia de Oersted (ver vídeo), ya comentada en una entrada anterior.

Años después Robert P. Crease escribió un libro sobre este tema (“El prisma y el péndulo”), el cual finaliza señalando que “la capacidad de reconocer la belleza de los experimentos nos puede ayudar a abrir los ojos ante un sentido de la belleza más fundamental” y, como punto final a su libro, incluye la siguiente cita del matemático, físico teórico y filósofo de la ciencia francés Henri Poincaré (1854-1912):

“Los científicos no estudian la naturaleza porque sea útil; la estudian porque les place, y les place porque es bella. Si la naturaleza no fuese bella, no valdría la pena conocerla, no valdría la pena vivir la vida”.

Os sugiero busquéis más información sobre estos experimentos que podéis ampliar, por ejemplo, en internet, en textos de Física (Tipler, Gettys, Alonso & Finn, etc.) y más específicamente en los siguientes libros de Robert P. Crease y Manuel Lozano Leyva:

R. P. Crease, El prisma y el péndulo: Los diez experimentos más bellos de la ciencia (Ed. Crítica, Barcelona, 2009).

M. Lozano Leyva, De Arquímedes a Einstein. Los diez experimentos más bellos de la física (Ed. Debate, Barcelona, 2005). (Este libro está disponible en la Biblioteca Politécnica, Óptica y Enfermería de la Universidad de Alicante)

Diapositiva1

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