Category Archives: Cosmology (general)

Remembering Stephen Hawking

Like many physicists, I woke to some sad news early last Wednesday morning, and to a phoneful of requests from journalists for a soundbyte. In fact, although I bumped into Stephen at various conferences, I only had one significant meeting with him – he was intrigued by my research group’s discovery that Einstein once attempted a steady-state model of the universe. It was a slightly scary but very funny meeting during which his famous sense of humour was fully at play.

4Hawking_1 (1)

Yours truly talking steady-state cosmology with Stephen Hawking

I recalled the incident in a radio interview with RTE Radio 1 on Wednesday. As I say in the piece, the first words that appeared on Stephen’s screen were “I knew..” My heart sank as I assumed he was about to say “I knew about that manuscript“. But when I had recovered sufficiently to look again, what Stephen was actually saying was “I knew ..your father”. Phew! You can find the podcast here.

Image result for cormac o raifeartaigh stephen hawking

Hawking in conversation with my late father (LHS) and with Ernest Walton (RHS)

RTE TV had a very nice obituary on the Six One News, I have a cameo appearence a few minutes into the piece here.

In my view, few could question Hawking’s brilliant contributions to physics, or his outstanding contribution to the public awareness of science. His legacy also includes the presence of many brilliant young physicists at the University of Cambridge today. However, as I point out in a letter in today’s Irish Times, had Hawking lived in Ireland, he probably would have found it very difficult to acquire government funding for his work. Indeed, he would have found that research into the workings of the universe does not qualify as one of the “strategic research areas” identified by our national funding body, Science Foundation Ireland. I suspect the letter will provoke an angry from certain quarters, but it is tragically true.


The above notwithstanding, it’s important not to overstate the importance of one scientist. Indeed, today’s Sunday Times contains a good example of the dangers of science history being written by journalists. Discussing Stephen’s 1974 work on black holes, Bryan Appleyard states  “The paper in effect launched the next four decades of cutting edge physics. Odd flowers with odd names bloomed in the garden of cosmic speculation – branes, worldsheets , supersymmetry …. and, strangest of all, the colossal tree of string theory”.

What? String theory, supersymmetry and brane theory are all modern theories of particle physics (the study of the world of the very small). While these theories were used to some extent by Stephen in his research in cosmology (the study of the very large), it is ludicrous to suggest that they were launched by his work.



Filed under Cosmology (general), History and philosophy of science, Science and society, Teaching, Third level

Hawking, Cambridge and the infant universe

I hugely enjoyed this week’s conference ‘Cosomolgy and the Constants of Nature’  at Cambridge University. There were some truly great talks by John BarrowJohn Ellis and Thanu Padmanabhan among others, not to mention Joao Magueijo describing his famous ‘variable speed of light’ theory in person. The icing on the cake was that my visit coincided with this week’s announcement of the detection of gravitational waves from the infant universe by the American BICEP2 experiment. If correct, the signal gives very significant experimental support for the theory of cosmic inflation, as well as the phenomenon of gravitational waves predicted by general relativity…..a double whammy if ever there was one.

Yesterday, I was priviliged to attend a seminar on the new results given by George Efstathiou and Anthony Challinor, team leaders on the rival Planck experiment (EU). There’s nothing like hearing a new observation dissected by a rival group and the seminar certainly didn’t disappoint. Both Cambridge physicists concluded that the BICEP 2 result is very robust, at least at face value, with the caveat that the signal needs to be reproduced at more than one frequency. The other caveat is that although the sensitivity of BICEP2 is up to ten times that of Planck,  there is a certain tension between the BICEP2 data and last year’s published data from Planck. I was particularly interested in Professor Efstathiou’s comment that the differing data of the two experiments may be a genuine effect, i.e., may represent some new physics at wide angles (Planck) that doesn’t affect the BICEP2 (small angle) measurements . The next few months should be very interesting indeed for cosmology…(see here for a rigorous discussion of the BICEP2 data by Peter Coles).

I had my own private excitement when I was introduced to Stephen Hawking for the first time. It was a very moving encounter, Professor Hawking remembered my father and his work. Stephen was also very interested in our recent discovery of Einstein’s unpublished attempt at a steady-state model of the cosmos. Indeed, his first remark to me was that steady-state cosmic models were the dominant cosmic paradigm when he started his research career at Cambridge all those years ago. He asked me to send him a copy of Einstein’s paper and I had a stressful evening trying to do so as my college email chose that day to block me for not changing my password often enough – of all days for that to happen!


I can’t quite believe this photo

All in all, it was yet another hugely productive visit to Cambridge University. Every time I come here something dramatic happens but I’m also looking forward to going home, I could do with a rest!


Farewell to Clare college


The American National Pubic Radio ran a piece on our Einstein discovery on today’s Morning Edition. I think it’s quite nice, apart from the usual emphasis on Einstein’s ‘blunders’ (why do journalists always see explorations as blunders?) Still, I’m learning not to be too precious about media stuff…


Filed under Cosmology (general)

Cosmology and the constants of nature at Cambridge

They say the Irish know how to party and the coincidence of yesterday’s victory in the Six Nations with a St Patrick’s weekend has brought the country to a whole new level of craziness. So it’s good to arrive in beautiful, tranquil Cambridge University for  a few day of quiet contemplation of the universe. It’s also good to get away from the hoopla generated by our recent discovery of an unpublished Einstein manuscript (see last post)…


Clare bridge this evening

I’m here for the conference ‘Cosmology and the Constants of Nature’, the next installment in the Cambridge/Oxford collaborative research project on the philosophy of cosmology (see here for an overview of the project).  Readers with a rudimentary knowledge of cosmology or particle physics will recognize the theme of this week’s meeting. Are ‘constants of nature’ such as the speed of light in vacuum or the gravitational constant truly constant? Or did they have different values in the early universe ? Are they truly independent of one another? Or are there hidden connections we are unaware of? Where do their values come from? The programme looks truly impressive, with talks by Martin ReesJohn Barrow, John Ellis, John Webb, Pedro Ferreira, Thanu Padmanabhan and Joao Magueijo. See here for the conference programme and overview.

I’m looking forward to Joao’s talk ‘Variations of c and other constants’. Joao made headlines a few years ago when he suggested that a speed of light in vacuum in the early universe very different to today’s value could give rise to many of the effects predicted by cosmic inflation. It looked like an intriguing alternative to inflation, although I haven’t heard much about the proposal recently. Joao also wrote a really nice book on the subject – in fact, it was one of the things that inspired me to persuade my boss to allow me to teach a course on the history of 20th century cosmology. It seems a while ago now, who would have guessed my little course would lead to the discovery of an unknown Einstein model of the universe ?

Right now, it’s time to stop musing and catch up on the world with the ten o’ clock news. Except wait, I don’t have a tv! I’m back in Clare College, my favourite of all the Cambridge colleges. There’s no tv, but on the other hand there’s something about working away in an unpretentious student room overlooking the beautiful quad that I find very relaxing. A perfect place for a bit of thinking…or maybe write a murder mystery…


Clare College – a good place for some quiet thinking


Some truly great talks by , John BarrowJohn Ellis, and Martin Rees among others so far at the conference, but the big news is yesterday’s announcement  of the observation of B-mode polarization in the cosmic microwave background by the BICEP2 experiment. If correct, the signal is strong evidence of gravitational waves emanating from the inflationary epoch of the infant universe. A huge boost for the notion of cosmic inflation, not to mention strong empirical evidence for the phenomenon of gravitational waves predicted by general relativity…..a double whammy if ever there was one. I won’t say more on this as several cosmologists here at Cambridge who are team leaders on the European PLANCK experiment will give an impromptu seminar on the US results tomorrow. I’d best change my flight – every time I come to Cambridge something dramatic like this happens…


Filed under Cosmology (general), History and philosophy of science

Einstein’s unfinished symphony in the media

Our recent discovery of an unpublished model of the cosmos by Albert Einstein (see last post or here for a preprint of our paper) is receiving a lot of media attention, it’s very humbling. First off the mark was Davide Castelvecchi with a very nice article in Nature. Davide’s article was quickly reproduced in various outlets, from Scientific American here to the Huffington Post here. Trawling over the internet, I see newspaper and magazine articles describing our discovery in a dozen languages. It’s nice to see historical material receiving this sort of attention, I guess everyone loves an Einstein story.


I’m also intrigued that it was the traditional media that picked up the story – with the exception of Peter Woit, no-one in the blogosphere seemed to notice our preprint or even a blogpost I wrote describing our paper. Perhaps we bloggers need the imprimateur of respected print journals more than we care to admit!

I notice one slightly misleading point in the electronic version of the Nature article is getting repeated everywhere. It’s probably not quite correct to frame Einstein’s attempt at a steady-state model of the cosmos in terms of a resistance to ‘big bang’ theories; there is no reference to the problem of origins in Einstein’s manuscript. Indeed, one of the most interesting aspects of the manuscript is that it appears to have been written in early 1931, at a time when the first tentative astronomical evidence for an expanding universe was emerging but the issue of an explosive beginning for the cosmos had yet to come into focus (e.g. the great debate between Eddington and Lemaitre later in 1931). It’s interesting that the initial mention in Nature of resistance to ‘big bang’ theories  is repeated in almost all other outlets, one can’t help wondering how many science journalists read our abstract. An honorable exception here is John Farrell at Forbes Magazine. John certainly noticed the discrepancy and no wonder – John has written an excellent book on Lemaitre.


All in all, it’s been a lot of fun so far. I’m getting quite a few emails from distinguished colleagues pointing out that Einstein’s model is trivial because it didn’t work, which is of course true. However, our view is that what Einstein is trying to do is very interesting from a philosophical point of view  – and what is even more interesting is that he apparently abandoned the project when he realised that a consistent steady-state model would require an amendment to the field equations. In short, it seems the Great Master conducted an internal debate between steady-state and evolving models of the cosmos decades before the rest of the community…


There is a very nice video describing our discovery here.


Filed under Astronomy, Cosmology (general), History and philosophy of science

Einstein’s exploration of a steady-state model of the universe

Some research news:

Last summer, in the course of our research into the Friedman-Einstein model of the cosmos (see this post or here for the article), I came across an unpublished manuscript by Einstein in which he explored a ‘steady-state’ model of the universe, i.e.,  a model of the universe in which space expands but the density of matter remains constant due to a continuous creation of matter from the vacuum. Such a model is radically different to previously known Einsteinian models of the universe, from his static model of 1917 to the evolving models he proposed in 1931 and 1932 in the wake of Hubble’s observations of the recession of the galaxies.  On the other hand, it bears some similarities to the famous  steady-state cosmic theories proposed by Hoyle, Bondi and Gold in 1948.

When was Einstein’s steady-state model written?

Several aspects of the manuscript suggest it was written in early 1931, after Hubble’s observation of the recession of the galaxies but before Einstein’s evolving models of 1931 and 1932. So it could be said that Einstein anticipated the general idea of steady-state models of the universe by almost twenty years!


Einstein giving a lecture at Caltech in 1931.His attempt at a steady-state model 
was probably penned during his stay in the USA in early 1931

A discarded model

Why was Einstein’s steady-state model never published? The bad news is that the model doesn’t work, i.e., it contains a fundamental flaw that leads to a null solution, i.e., a universe empty of matter. It only looked like a viable theory because Einstein made a mistake in his analysis. There is evidence in the manuscript that Einstein spotted the problem on revision and this is almost certainly the reason he declined to publish the manuscript. So it’s a failed model. That said,  it is very interesting that Einstein didn’t anticipate that the particular approach model he used (a variation of the de Sitter model) would lead to a null solution, and even more interesting that when the problem became apparent, he declined to try again with a more sophisticated version. We see this as an important crossroads – it seems that on realising that a successful steady-state model would require amending the field equations of relativity, Einstein plumped instead for evolving models.

Who cares?

It could be argued that steady-state models are of little interest today because observations have shown unequivocally that we live in an evolving universe  (not to mention the fact that Einstein’s version didn’t work). All of this is true, but what Einstein is attempting to do is of great interest; the standard narrative that Einstein eagerly embraced evolving models of the cosmos on learning of  Hubble’s results because they allowed him to drop the cosmological constan, no longer seems entirely accurate. In his attempt at a steady-state model in the manuscript, Einstein retains the cosmological constant and even loosely associates it with the creation of matter from the vacuum. Most interesting of all, it seems that Einstein conducted an internal debate between steady-state and evolving models of the universe decades before a similar debate took place in the wider cosmological community.

Why was the theory not found before?

The manuscript was never published and was archived in the Albert Einstein Archives as a draft of something else, Einstein’s published 1931 model of the cosmos (also known as the Friedman-Einstein model). It was while researching materials relevant to the latter paper that we discovered the model (I nearly fell off my chair).  This sort of thing happens all the time in historical research – for example, we  also discovered a number of numerical errors  in the Friedman-Einstein model that no-one seems to have noticed before.

Where to find more on this

We have submitted a paper containing a transcription, translation and analysis of Einstein’s manuscript to the European Physical Journal (H) by kind permission of the Einstein Papers Project and the Hebrew University of Jerusalem. A preprint of the paper can be found on the physics ArXiv at


Nature have a news article on our discovery here. It’s a nice article although the writer has confused Einstein’s reservations concerning a dynamic universe with his reservations concerning Lemaitre’s theory of origins (those come later). One of the most interesting aspects of the manuscript is that it seems to predate discussions of the issue of an origin for the cosmos. It’s interesting that Davide’s  error is repeated in outlets such as  Scientific American here and the Huffington Post here! There is a very nice video describing our discovery here


Filed under Cosmology (general), History and philosophy of science

Einstein’s smallest blunder

At 17.45 GMT today, I carried out the final fuel checks on our Einstein paper, took a deep breath and hit launch (okay SUBMIT).

Over the summer, I came across quite a few references to a paper Einstein wrote on cosmology in early 1931, in the wake of Hubble’s first observations of the expanding universe (Ahemperhaps you mean  in the wake of Hubble’s observation of an apparent linear relation between the recession of the spiral nebulae and their distance, an empirical result that some theorists interpreted as evidence of an expanding universe – Ed ).

Like many Einstein papers, this paper is written in German, but unlike most Einstein papers  I could not find an English translation anywhere – pretty strange, given that this is Einstein’s first official  publication in the light of the new astronomical results (and given that he wrote very few papers on cosmology). So, with permission from the Einstein Archives, I spent the summer translating the paper with a colleague and adding hysterical remarks. Sorry, historical remarks. It was a most enjoyable project, with a few surprises along the way:

(i) Einstein’s 1931 paper offers a lot of interesting insights into his thoughts on the first tentative evidence for an expanding universe, but it does not say what a lot of science historians seem to think it says

(ii) Some calculations, where Einstein estimates values for the radius of the universe and the density of matter using Hubble’s results, seem to contain a fairly obvious numerical error

(iii) The same error can be seen in writing on a blackboard preserved from a lecture Einstein gave on the paper at Oxford University in 1931


Einstein in Oxford – nice to know we all make mistakes

There has already been quite a bit of interest in our article, it seems your humble correspondent may have gotten lucky for once. Or we  might be wrong, in which case we’re going to look very silly. In the meantime, it looks like I’ll be doing a bit of traveling this year….

Update (Jan 2014)

Our article has now been published in the European Physical Journal (History). You can find the article here or a preprint on the Physics Arxiv here.

Update (Jan 2014)

Our article made the cover of EPJ!

EPJ cover


Filed under Cosmology (general)

Last day at COSMO13 in Cambridge

Today was the last day of the COSMO13 conference, a most enjoyable, if sometimes exhausting conference – so many seminars, not to mention a banquet in Trinity College last night.


The conference finished this morning with lectures on dark energy from Ofer Lahav and Edmund  Copeland, on dark energy and modified gravity by Lam Hui and Claudia de Rahm, and on inflation by Richard Easther. The conference website is here and videos of the presentations will be available here in the next few days.

UPDATE: Videos of the plenary talks and pdfs of talks from the parallel sessions are  now available here.

If I had to summarize the conference in one sentence, I think the take-home message is that recent experimental results in both cosmology (from the PLANCK satellite) and particle physics (from the LHC) are strongly supportive of our basic models, giving strong confidence that our underlying theories are on the right track. The downside is that in each case, the fit is a teeny bit too good for comfort. There is a slightly worrying lack of evidence for physics beyond the standard models so far – a lack of evidence for supersymmetric particles at the LHC (although a low-mass Higgs is in principle good news for SUSY) and a lack of non-Gaussianities and parity violation in the PLANCK measurements of the cosmic microwave background. But the future is bright, especially considering the projected increases in luminosity at the LHC and the possible detection of B-mode polarization in the CMB by PLANCK.

That said, I agree heartily with Ofer Lahav’s comment that it is extraordinary to be living through a paradigm shift in cosmology, namely the discovery of the accelerated expansion (two paradigm shifts if you include inflation). Added to which we are now in an era of precision cosmology. Indeed, measurements of the cosmic microwave background by PLANCK are now reaching such a level of precision that it isn’t always meaningful to talk about agreement or tension with astrophysical measurements – the latter have quite a lot of catching up to according to George Efstathiou!

On a personal note, it’s extraordinary to see Dad’s work on supersymmetry reaching a whole new audience in cosmology, as supersymmetry breaking in the early universe  becomes a major area of research. I can’t tell you how many young researchers eyed my badge in astonishment and then started to quizz me about O’Raifeartaigh models!

Now the conference has finally ended, it’s nice to get back to work on my paper on Einstein’s cosmology in the 1930s – some of the talks here have given me some new ideas. I managed to finish most of the paper here, I’ll always think of it as my Cambridge paper!


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Filed under Cosmology (general)