January 19, 2015
“There was a young lady named Bright” – A summary of “A Brief History of Light”, relatively speaking
The first cafe of 2015 could not have been more interesting and well attended! And those present were particularly lucky, because thanks to technical issues, the video of the afternoon is slightly abbreviated.
2015 is not only the International Year of Light and Light Based Technologies (celebrations are in progress in Paris at the time of writing this), but it is also the 100 year anniversary of Einstein’s equations for General Relativity. While humans have known about light in some form from the beginning of time, understanding it and being able to harness its properties took an inordinate amount of time and effort, and was not without controversy. Although one may have heard the names of some of the physicists who profoundly influenced our understanding of light, the details are mostly known only to “insiders”. On Saturday, thanks to Professor Stone, Tilde Cafe attendees got a chance to peek into this relatively arcane realm, and get a sense of the breadth of the scientific contributions of these individuals, and also a little about the process of their discoveries. More importantly, an appreciation of the relationship between theoretical and experimental physics was evident – it’s what contributed to recognizing the dual wave and particle properties of light.
Doug Stone’s recent research is focused on lasers and their novel modifications and applications, for which he and his colleague Hui Cao received the Willis E. Lamb award for Laser Science and Quantum Optics just last week. A poorly appreciated fact, but one which long time Tilde Cafe attendees might have recalled from Steve Girvin’s talk in 2010, is that Einstein laid the foundations for lasers, the acronym for light amplification by stimulated emission of radiation. What few will have known before this cafe, is that lasers which produce light by themselves are actually oscillators and not amplifiers, rendering the acronym for them as LOSER – however, due to this unfortunate acronym, “laser” is used more broadly!
Many thanks, Doug, for an informative and entertaining afternoon. It was wonderful to see such a great turnout and while the video has been posted on the youtube channel, it doesn’t hold a candle (pun intended) to having been there that afternoon – https://www.youtube.com/user/tildecafe
To make up for the footage lost to posterity, we close the circle from the subject line for this email, with this limerick:
There was a young lady named Bright
Whose speed was far faster than light;
She set out one day
In a relative way
And returned on the previous night.
– A. H. Reginald Buller (from Punch, 1923)
The Universe and diseconomies of scale – a consequence of expansion.
To summarize a cafe discussion on dark energy seems almost like a Sisyphean task, not only because of the burden of what is still unknown about the topic, but also the complexity of what is known. Professor Nikhil Padmanabhan ignited the interest of those attending this most recent Tilde Cafe discussion. He shed light on the topic quite effortlessly and gave us some appreciation of the magnitude of the questions he and his peers are attempting to answer through their research efforts. That the Universe was expanding was known for almost a century, but it has been only in the last two decades that there has been evidence of an acceleration of this expansion. And this new evidence comes from the field of dark energy. Although the term “dark energy” was coined only in 1998 as a consequence of then puzzling results, the 2011 Nobel Prize in Physics went to three scientists who “helped to unveil a Universe that to a large extent is unknown to science.” Dark energy constitutes about 70%of the Universe; dark matter – 25%; we constitute barely 0.03%! Perhaps one aspect that makes it harder for those of us who aren’t devoted to studying dark energy appreciate the field, is the fact that while there is evidence of the existence of dark energy, it’s composition remains largely unknown. After introducing us to some basic concepts, Nikhil described what goes into a typical survey of the skies, right from collecting images, to how spectra are collected from the objects observed – check the video from the afternoon at – http://www.youtube.com/watch?v=xGxU1uRCx1I&feature=youtu.be (55 min mark). Despite the relative opaqueness of the topic, we had almost twice the number of people than we’d expected, which is always welcome and a treat, so thank you all for coming out on a lovely Saturday afternoon. This was the first cafe discussion for many, and I hope it has helped to whet their appetites – watch this space for many more engaging discussions. From the press release by the The Royal Swedish Academy of Sciences – “…..dark energy [is] remains an enigma – perhaps the greatest in physics today”, and Nikhil helped us get a peek at that enigma on Saturday afternoon. Thank you, Nikhil.