Relativity – Einstein and Light Disturb the Universe

In the summer of 1895, while the rest of the world was locked in the Victorian age, Albert Einstein was pondering the phenomenon of light.  Though he was just sixteen, Einstein had renounced his German citizenship, rejected Judaism, and begun “a positively fanatic orgy of free thinking.” Bored in his prep school near Zurich, he took long walks in the Swiss Alps, experimenting in his own private chamber — his mind.

All his life, Einstein would perform Gedankenexperimente — thought experiments. That fall, he did his first. What would the world look like, he wondered, if he could ride on a beam of light? “If a person could run after a light wave with the same speed of light,” he thought, “you would have a wave arrangement which could be completely independent of time.” He knew that “such a thing is impossible,” yet he could not stop thinking about the ride. Viewed from a beam of light, clocks would seem frozen, the light from their moving hands never reaching the retreating passenger. And yet, like someone in a slow elevator, light’s rider would barely know he was moving. All the staid laws of Newton’s universe would be upset.

Credit: Saulo Trento

Credit: Saulo Trento

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Einstein 1905: From “Energy quanta” to “Light quanta”

“The energy of a light ray spreading out from a point source is not continuously distributed over an increasing space [wave theory of light] but consists of a finite number of energy quanta which are localized at points in space, which move without dividing, and which can only be produced and absorbed as complete units.” With these words Albert Einstein (1879-1955) introduced his “heuristic point of view toward the emission and transformation of light” which was presented in his first Annus Mirabilis paper published in 1905, a year that Einstein himself referred to as “very revolutionary”. Einstein introduced the concept of “light quanta”, an indivisible packet, although it was not until 1926 when the term “photon” (coined by Gilbert Lewis (1875-1946) in an article published in Nature) substituted Einstein’s “light quanta” forever.

Of course, this year 2015 marks the centenary of the publication of Einstein’s papers on general relativity and –as the IYL 2015 Resolution points out­– “the embedding of light in cosmology thorough general relativity”. However, perhaps it is not so well known that Einstein also made several seminal contributions to the science of light. He did not only introduce in 1905 the concept of “light quanta” and applied it to theoretically study “the emission and transformation of light”, as it has been mentioned before, but he also postulated stimulated emission in 1916, which eventually became the basis of laser operation. Besides these two contributions, Einstein was also one of the pioneers in exploring the wave-particle duality of light in a paper published in 1909. There is no doubt that Einstein gave us a remarkable legacy in light.

Albert Einstein in 1905. Credit: Wikipedia.

Albert Einstein in 1905. Credit: Wikipedia.

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IYL 2015 Events #47 | Week 23-29 November

Find below the activities listed on the IYL 2015 Event Programme starting between 23-29 November. Click on the links for more information on the different activities.

Please note that some last-minute additions to the event programme may not appear here. For an up-to-date overview of IYL 2015 events please visit the IYL 2015 Event Programme.

Celebrating IYL 2015 and the Story of Light

The National Institute of Technology (NIT) Calicut (India) organized a three-day event Tathva’15 from 30 October to 01 November 2015 at the NIT Campus, Calicut, Kerala, India. The event included invited lectures, workshops and exhibitions. The workshops were desgined to Illuminate the young minds by developing skills in a wide range of engineering disciplines. There were exhibitions on the rich heritage of Indian railways, India’s first 3D printed humanoid robot, Light: Beyond the Bulb, and state-of-the-art electronics by Keltron. There were five invited lectures by experts in different disciplines. I delivered a lecture on the ‘The Story of Light’ covering the Greek era (pre- 8th century C.E.), the Arab-Islamic Golden Age (8th to 15th century C.E.), the European period (16th to 19th century C.E.) and the modern period (20th century C.E. onwards).

Zahid H. Khan delivering a lecture at Tathva'15, NIT Calicut, Kerala. Credit: Tathva'15.

Zahid H. Khan delivering a lecture at Tathva’15, NIT Calicut, Kerala. Credit: Tathva’15.

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Catching the light (but not too much)

Several years ago, while travelling through India, I discovered a peculiar shop called “Old things dealers”. From over-aged books to most ancient kitchen utensils, anyone could have found any “thing” to bring back from the country as a souvenir.

I was very excited to discover a series of negatives dated from the 1930s in their original box. As a tourist, I usually try to avoid taking back trinkets. However I couldn’t resist this find. I was attracted by these portraits and landscapes from the past that were once abandoned in this shop. Back from India, the box of negatives was put away on a shelf and abandoned again.

The old things dealers, Tamil Nadu, India. Credit: Gina Gunaratnam.

The old things dealers, Tamil Nadu, India. Credit: Gina Gunaratnam.

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