Tag Archives: Cosmology (general)

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 Stephen was also very interested in our recent discovery of Einstein’s unpublished attempt at a steady-state model of the cosmos.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!

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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!

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Farewell to Clare college

Update

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…

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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)…

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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…

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Clare College – a good place for some quiet thinking

Update

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…

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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.

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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.

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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…

Update

There is a very nice video describing our discovery here.

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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!

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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 http://arxiv.org/abs/1402.0132

Update

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

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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

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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!

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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.

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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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COSMO 2013 at Cambridge University

Today was the first day of the COSMO 2013 conference at Cambridge. Walking up the path to the hallowed Department of Applied Mathematics and  Theoretical Physics (DAMTP), I was gripped by my usual fear that I might meet with a frosty reception at the door; “No experimentalists, please!”

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The hallowed halls of DAMTP

But it’s not that sort of conference. COSMO 2013 is a very nice mix of cosmology and particle physics, theory and experiment. You can see the conference poster and programme here.

This morning started with two contrasting plenary talks on particle physics; an experimental talk by Lars Sonneschein, and a more general talk ‘From the Higgs boson to Cosmology’ by well-known CERN theoretician John Ellis.

In his talk ‘Recent Results from the LHC’, Professor Sonnenschein gave a brief overview of recent results at the LHC, from current production rates of top anti-top quarks to the famous discovery of the Higgs boson. Much of this probably wasn’t that new to the audience given the number of Higgs talks last year, but it was good to see up-to-date information on the decay modes and coupling constants for the Higgs.The main point was that with more and more accurate measurements, there is still no evidence yet of any physics beyond the Standard Model, whether one was searching for dark matter, microscopic black holes or indeed supersymmetry (SUSY). On the other hand, there were grounds for good cheer for the experimentalists given the projections Lars gave for increased luminosity at the LHC in the next few years.

John Ellis’s talk took a very different tack. He starting by explaining why a light Higgs mass and weak couplings is a good result for supersymmetry (SUSY can stabilize a light Higgs), giving theorists yet another reason to take the theory seriously, despite the ecent narrowing of windows of possibility at the LHC (at least for minimal models). Professor Ellis then made a connection with cosmology, remarking that basic Wess-Zumino SUSY models can be shown to fit very well with many generic models of inflation;in particular, adding supersymmetry to the mix can give models that fit very comfortably within the recent PLANCK results (some fall well within the dark blue region in the famous Planck figure below). A colleague of a certain age commented to me afterwards  that he isn’t quite reconciled  with the way inflation has become the dominant paradigm in today’s cosmology; for my part, I can never get used to today’s discussions of  supersymmetry in both cosmology and particle physics, having grown up thinking of it as an obscure theory practised only by my father and a few colleagues around the world! Science truly evolves…

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Prof Ellis wearing his Standard Model t-shirt

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Generic SUSY versions of inflation can give models that fall within the most probable region (dark blue)

At question time afterwards, I commented that I was struck by the contrast between the two talks, i.e. the strong motivation for SUSY from theory but the lack of results so far at the LHC, and asked Professor Ellis whether he thought the first evidence for SUSY might indeed come from the cosmic microwave background rather than particle accelerators (I made a mess of the question, nervous for once!). He responded by pointing out that it took 40 years to find the Higgs in particle accelerators, thus we should not be too impatient.  This answer makes a lot of sense to me, I’m a bit dismayed at the way SUSY scepticism has quickly become almost as popular a sport as string theory scepticism. After all, theory is often decades ahead of experiment, particularly in particle physics…

There were two other plenary lectures after coffee, an overview of Dark Matter by Malcolm Fairbairn and a talk on neutrino masses by Silvia Pascoli. They were both excellent talks but there is so much going on I just can’t keep up! Also, Stephen Hawking is sitting three tables away, also working away at a computer – I’m going to tidy myself off to the afternoon sessions before someone mistakes me for a journalist and chases me out of the canteen!

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Last day of Quantum Foundations conference at Oxford

Yesterday was the last day of the  Cosmology and Quantum Foundations  conference, a symposium that formed part of the  Establishing the Philosophy of Cosmology project at Cambridge and Oxford.

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There was no workshop in the  morning, but there were two weighty lectures in the afternoon, ‘Inflationary Cosmology as a Laboratory for Primordial Quantum Mechanics’ by Antony Valentini and ‘Relational Quantum Mechanics: Spinfoam Cosmology’  by Carlo Rovelli.

Antony Valentini’s talk was the second installment of his thesis that we should consider the possibility that the quantum equilibrium universe we experience is simply a subset of a much larger ensemble which is deterministic, not in equilibrium, and does not obey the standard rules of quantum probability. In this model, elements of the larger ensemble made a transition  by a process of relaxation on atomic timescales to the quantum equilibrium we see today. Antony hypothesized that observational cosmology might offer a test for his model because any non-equilibrium states remaining before cosmic inflation would have become frozen during this period,  feeding into the cosmic microwave background at the end of inflation. His analysis suggested one explanation for the well-known power deficit in the CMB at long wavelengths in the Planck and WMAP data.  I have no idea what the theoreticians thought of Antony’s hypothesis, but talks like this certainly give the lie to those who accuse physicists of groupthink and of being incapable of thinking outside the box!

Carlo Rovelli then gave the second installment of his talk on his relational view of quantum mechanics (see last post). The main point here was that adding gravity to the analysis is not a complication in the case of the relational interpretation of qt because the model is fundamentally relativistic in nature (gravity is simply a curvature of spacetime in relativity). He went on to describe how the theory leads to the ‘quantum loop’ view of quantum gravity. I am not qualified to comment on the theory, but what I took out of Carlo’s talks is that the only fundamental entities in relational theory are covariant quantum fields -the wavefunction has no physical significance, any more than a mathematical operator.

All this was followed by a round table discussion between, Carlo, Antony, Simon Saunders and David Wallace. For many of us, this was a major highlight of the conference. It was a privilege to hear major proponents of the many-worlds interpretation of quantum theory (Saunders and Wallace) arguing point-by point against the relational view (Rovelli), not to mention pointed interjections from heavyweights in the audience such as John Barrow, Julian Barbour and Joe Silk. During the course of the debate, it struck me that the discussion was in some ways a modern echo of the classic debate between the Heisenberg and Schroedinger interpretations of the quantum world. I could almost see Heisenberg behind Carlo Rovelli’s chair, applauding his emphasis on the discreteness as the key property of the quantum world and his dislike of the wavefunction. In the opposite corner, Schroedinger’s view had much in common with the many-worlds camp because of his dislike of collapsing wavefunctions. Indeed, it has recently been suggested by several authors that Schroedinger’ s later work on quantum interpretation somewhat anticipates the many-worlds view (will dig out references on this).

So a splendid finish to a splendid conference; an important debate on the meaning of quantum theory between leading proponents of alternate modern interpretations of the theory, with echoes of history throughout.

Update

It all happens at Oxford. Strolling past the Sheldonian this evening, I heard the familiar strains of Vivaldi’s Four Seasons. Turns out Nigel Kennedy was giving a concert with the Oxford Philomusica, so I sneaked into the foyer to hear the last few movements. You don’t hear much about Kennedy since he moved to Poland, but his performance was as electric as ever. I timed the applause at over 20 minutes, he certainly hasn’t lost his gift for communicating with the audience. However, the real surprise was the orchestra, it didn’t sound like any college orchestra to me – lovely crisp playing, fantastic articulation in the fast passages, and super pianissimos in the slow passages. Turns out the Oxford Philomusica is a relatively new initiative, a professional orchestra in residence at the university. What a great idea , I’m sure it gives a unique opportunity for the very best of the music students

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Nigel Kennedy at the Sheldonian

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Day II at Oxford

Today was the second day of the  Cosmology and Quantum Foundations  conference, a symposium that forms part of the  Establishing the Philosophy of Cosmology project at Cambridge and Oxford.

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The workshop this morning started with a fascinating talk by Douglas Spolyar  on a model of cosmic inflation that predicts that inflation could happen at relatively low energies. The big advantage of such models that they are testable at the TeV energies, i.e., at accelerators such as the LHC; I need to read the paper before I comment further, but all the talks will soon be available on the conference website.

Laura Mersini then gave a talk on evidence for the multiverse post-Planck. This was a discussion of her thesis that the multiverse should in principle be detectable in the cosmic microwave background because of the phenomena of quantum entanglement and decoherence. She then discussed how in her view the Planck data offers support for the model in terms of the cold spot, the dark flow and other effects. It was a good thorough lecture and I understood a lot more than I did at the Cambridge conference on the philosophy of cosmology last March.  Of course, not all cosmologists agree with her thesis and there was plenty of lively discussion from the audience – as an experimentalist, I really like the way theoreticians constantly challenge each other  during their talks, it’s very interactive!

In the afternoon , it was back to the conference proper for ‘Probability and the multiverse: an Everettian view’, the second installment of Simon Saunder’s discussion of the many-worlds interpretation of quantum theory. I found this a lot more challenging than Monday’s talk, I really need to brush up on my reading on many-worlds. Max Tegmark then gave a talk on ‘Thermodynamics, information and consciousness in a quantum multiverse’, a discussion that was  full of interesting insights and provocative ideas. A central theme of his is that entropy does not always increase, but can in fact decrease on observation. I have heard this idea before but I’ve never been clear whether it is an argument that pertains to entropy as a state of information about a system, or whether it is literally true of physical entropy.  I wanted to ask this at question time, and how one might test the hypothesis,  but time ran out.

[Update: I asked Max this question over coffee. I think the answer is yes to physical entropy and he suggested an experiment that could test the idea; unfortunately, I understood about 5% of what he said, I need to read up on this!]

The last speaker of the day was Carlo Rovelli, who spoke on a new interpretation of quantum theory known as the relationary view, a hypothesis  he put forward in the 1990s. This interpretation of qt  imports a lot of ideas from special relativity, in particular applying the idea of the reference frame of the observer to the measurement problem. Thus, instead of talking about wavefunctions that collapse into one state or another, one has to consider that measurements of systems are made relative to another system – it is the relation between the systems that counts. It was fascinating to hear a description of this intriguing new idea from its creator, and tomorrow he will explain how the new theory gives a description of  quantum gravity. [Writing this, I seem to remember that one of Schrodinger's own objections to the notion of collapsing wavefunctions involved the problem of observations of the same object from different reference frames, must look this up]

After all that, it was time for the conference dinner. I was lucky enough to be at the same table as Carlo, who is also  the author of the highly regarded book ‘The First Scientist: Anaximander and His Legacy’ and we had a great discussion on the history of science. I have never met a physicist who is not interested in the history of our subject – how things were found out is almost as interesting as the things themselves!

As a bonus, the an after-dinner talk was given by Max Tegmark who posed an intriguing question; what if mathematics is a useful way of describing nature simply because nature *is* mathematics? This question was  first raised by Pythagoras, and Max gave an extremely interesting talk on the subject. So much so that I finally realised who he reminds me of – Richard Feynman!

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I had a quick walk under the Bridge of Sighs before dinner

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Oxford!

I’m at Oxford University this week, at the Cosmology and Quantum Foundations  conference, a symposium that forms part of the recent Establishing the Philosophy of Cosmology project at Cambridge and Oxford.

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Physicists don’t always accept the relevance of philosophy in the study of physics, but there is no question that quantum theory has long posed difficult questions of a philosophical nature, not least the interpretation of the quantum wavefunction. In addition, modern cosmology points towards a universe that was once in an extremely small and dense state,  that may or may not have had a finite beginning. As well as the familiar problems of quantum philosophy, this raises a host of other philosophical problems, such as ‘When did the laws of physics become the laws of physics?’ or ‘Were space and time always there or did emerge with the big bang ?’

The conference started at 9.30 this morning with a workshop on cosmic inflation. First up was Andrew Liddle ; after a brief review of the basic postulate of inflation, Andrew explained how the theory soon provided an explanation for the formation of galactical structure (in terms of quantum fluctuations in the early universe inflated to the perturbations observable in the cosmic background radiation). This explanation has since become a major motivation for the theory. Andrew then described new constraints imposed on inflationary models by the data from the Planck satellite.

Andrew’s talk was followed by a seminar by Douglas Spolyar on a new model describing how inflation might have ended (‘supercooled inflation’). I won’t describe it here as part II is due tomorrow. For lunch, we all trooped over to the famous Clarendon lab to hear well-known MIT physicist Max Tegmark give  a rather different sort of talk, ‘The future of life – a cosmic perspective’,  hosted by Oxford’s Future of Humanity Institute. Max’s main thesis was that a cosmological perspective renders existential problems more important, not less. Given that there is a finite chance that mankind is the only conscious life in the universe, if mankind were to die out there would be no-one to observe the universe! It’s a fascinating and provocative argument, and I was pleased to see climate change up there amongst the existentialist risks. However, I wasn’t entirely convinced by Max’s central theme ; apart from the philosophical debate concerning the role of the observer (is he/she really that important?) one wonders are there not more selfish reasons to tackle existential risks (what do I know,  it was an interesting take anyway).

After the Tegmark seminar, it was off to St Anne’s College for the opening of the conference proper. The afternoon session kicked off with a talk by well-known Oxford physicist Simon Saunders on the Many Worlds interpretation of quantum theory. Oxford have a major reputation in this area and I know no better physicist to give an introduction to this topic. It was a fascinating lecture and part II is tomorrow.  After coffee, Max Tegmark gave another excellent talk, this time on The cosmological interpretation of quantum mechanics – unifying the inflationary and quantum multiverses’ (more on this tomorrow).

After dinner with Andrew, I walked around Oxford and took a few photos.There is such fabulous  architecture everywhere you look, no wonder it produces great thinkers. Also, there’s a real thrill in seeing so many locations that are familiar from Inspector Morse , not to mention Lewis.

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The Bodlean (I think)

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The Bridge of Sighs

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The River Thames

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