Archive for Bending of Light

Lights all askew in the Heavens – the 1919 Eclipse Expeditions (Updated)

Posted in History, Talks and Reviews, The Universe and Stuff with tags , , , , , on June 3, 2019 by telescoper

Here is a video of my talk at the Open Meeting of the Royal Astronomical Society on April 12 2019. Was it really so long ago?

You can find the slides here:

The 1919 Eclipse: That Was The Talk That Was…

Posted in History, The Universe and Stuff with tags , , , , , on May 29, 2019 by telescoper

Well, I did my talk this afternoon to mark the centenary of the 1919 Eclipse Experiment that was performed on May 29th 1919. It’s a good job we changed the venue to a bigger lecture theatre than originally booked because even the new one was full! Thanks to everyone who came, and I hope you enjoyed the talk!

Anyway, here are the slides if you’d like to see them:

Here is a picture of me about to start:

Now that the centenary has passed I promise to post a bit less about this topic, although there are still a few things coming up that I might mention…

Lights all askew in the Heavens – the 1919 Eclipse Expeditions

Posted in History, Talks and Reviews, The Universe and Stuff with tags , , , , , on April 23, 2019 by telescoper

I completely forgot to upload the slides from my talk at the Open Meeting of the Royal Astronomical Society on April 12 2019 so here they are now!

Just a reminder that the centenary of the famous 1919 Eclipse Expeditions is on 29 May 2019.

The Mystery Object Revealed

Posted in History, The Universe and Stuff with tags , , , , , on April 12, 2019 by telescoper

As I revealed this afternoon in my talk at the Royal Astronomical Society, yesterday’s mystery object..

..is in fact the 4-inch object (geddit?) glass that was manufactured by Howard Grubb in Dublin and taken to Sobral in Brazil in 1919 to be used in a famous experiment to measure the bending of light by the Sun during a total eclipse.

Here is a picture of the observing setup in Sobral:

The 4-inch lens is mounted in the square tube on the right. The eclipse was observed using a coelostat (a steerable mirror) that reflected light into the telescopes. Here is a photograph of the coelostat:

The object glass and coelostat are usually on display at Dunsink Observatory but these are currently en route to Brazil for the commemorations of the centenary of the historic expedition.

Photo Credits to Tom Ray of DIAS…

Dyson on Eddington

Posted in Books, Talks and Reviews, The Universe and Stuff with tags , , , , , , on April 10, 2012 by telescoper

I’m grateful to George Ellis for sending me a link to a book review written by Freeman Dyson that appeared in a recent  edition of the New York Review of Books. I was particularly interested to read the following excerpt about Arthur Stanley Eddington. I have been intrigued by Eddington since I wrote a book about his famous expeditions (to Principe and Sobral) in 1919 to measure the bending of light by the Sun as a test of Einstein’s general theory of relativity; I blogged about this on its ninetieth anniversary, by the way, in case anyone wants to read any more about it.

Although I read quite a lot about Eddington, not only during the course of researching the book but also afterwards, as there are many things about his character that fascinate me. He died long before I was born, of course, but whenever I meet someone who knew him I ask what they make of him. Not altogether surprisingly, opinions differ rather widely from one person to another as his character seems to have been extremely contradictory. He doesn’t seem to have been very good at small talk, but was nevertheless a much sought-after dining companion. He was a man of great moral integrity, but at times treated his colleagues (notably Chandrasekhar) rather shamefully. He was a brilliant astrophysicist, but got himself hooked on his peculiar Fundamental Theory which was a dead end. He remains an enigma.

Anyway, this is what Dyson has to say about him:

Eddington was a great astronomer, one of the last of the giants who were equally gifted as observers and as theorists. His great moment as an observer came in 1919 when he led the British expedition to the island of Principe off the coast of West Africa to measure the deflection of starlight passing close to the sun during a total eclipse. The purpose of the measurement was to test Einstein’s theory of General Relativity. The measurement showed clearly that Einstein was right and Newton wrong. Einstein and Eddington both became immediately famous. One year later, Eddington published a book, Space, Time and Gravitation, that explained Einstein’s ideas to English-speaking readers. It begins with a quote from Milton’s Paradise Lost:

Perhaps to move
His laughter at their quaint opinions wide
Hereafter, when they come to model heaven
And calculate the stars: how they will wield
The mighty frame: how build, unbuild, contrive
To save appearances.

Milton had visited Galileo at his home in Florence when Galileo was under house arrest. Milton wrote poetry in Italian as well as English. He spoke Galileo’s language, and used Galileo as an example in his campaign for freedom of the press in England. Milton had witnessed with Galileo the birth struggle of classical physics, as Eddington witnessed with Einstein the birth struggle of relativity three hundred years later. Eddington’s book puts relativity into its proper setting as an episode in the history of Western thought. The book is marvelously clear and readable, and is probably responsible for the fact that Einstein was better understood and more admired in Britain and America than in Germany.

As a student at Cambridge University I listened to Eddington’s lectures on General Relativity. They were as brilliant as his books. He divided his exposition into two parts, and warned the students scrupulously when he switched from one part to the other. The first part was the orthodox mathematical theory invented by Einstein and verified by Eddington’s observations. The second part was a strange concoction that he called “Fundamental Theory,” attempting to explain all the mysteries of particle physics and cosmology with a new set of ideas. “Fundamental Theory” was a mixture of mathematical and verbal arguments. The consequences of the theory were guessed rather than calculated. The theory had no firm basis either in physics or mathematics.

Eddington said plainly, whenever he burst into his fundamental theory with a wild rampage of speculations, “This is not generally accepted and you don’t have to believe it.” I was unable to decide who were more to be pitied, the bewildered students who were worried about passing the next exam or the elderly speaker who knew that he was a voice crying in the wilderness. Two facts were clear. First, Eddington was talking nonsense. Second, in spite of the nonsense, he was still a great man. For the small class of students, it was a privilege to come faithfully to his lectures and to share his pain. Two years later he was dead.