Archive for Martin Rees

Water and Energy

Posted in Biographical, Science Politics, The Universe and Stuff with tags , , , , , on May 25, 2010 by telescoper

I’ve refrained from blogging about the fraught history of my attempts to have a new  gas boiler installed in my house. Today, however, at last I have finally succeed in getting a state-of-the-art high-efficiency condensing contraption fit for the 21st Century, which will hopefully save me a few bob in gas bills over the winter but, more importantly, actually produce hot water for more than a minute or so without switching itself off.

The chaps that did the job for me actually had to test all the radiators too, which meant switching them all up to maximum. It wasn’t quite as hot today as it was yesterday but nevertheless the inside of the house was like a Turkish bath for a while. I therefore sat outside in the Sun for a bit waiting for them to get finished and tidy everything up.

While I was sitting there I got thinking about sustainable energy and so on, and was reminded of a comment Martin Rees made in his Reith Lecture not long ago. Wanting to sound positive about renewable energy he referred to the prospect of generating significant tidal power using a Severn Barrage. Given the local relevance to Cardiff – one of the main ideas is a barrage right across the Severn Estuary from Cardiff to Weston-super-Mare -so he presumably thought he was on safe ground mentioning it. In fact there was a lot of uneasy shuffling in seats at that point and the question session at the end generated some tersely sceptical comments. Many locals are not at all happy about the possible environmental impact of the Severn Barrage. That, and the cost – probably in excess of £20 billion – has to be set against the fact that such a barrage could in principle generate 2GW average power from an entirely renewable source. This would reduce our dependence on fossil fuels and increase our energy security too. The resources probably aren’t available right now given the parlous state of the public finances, but I’m glad that the Welsh Assembly Government is backing serious study of the various options. It may be that it won’t be long before we’re forced to think about it anyway. The Wikipedia page on the various proposals for a Severn Barrage is very comprehensive, so I won’t rehearse the arguments here. In any case, I’m no engineer and can’t comment on the specifics of the technology required to construct, e.g., a tidal-stream generator. However, I have to say that I find the idea pretty compelling, provided ways can be found to mitigate its environmental impact.

For a start it’s instructive to look at turbine-generated power. Wind turbines  are cropping up around the British isles, either individually or in wind farms. A  typical wind turbine can generate about 1MW in favourable weather conditions, but it needs an awful lot of them to produce anything like the power of a conventional power station. They’re also relatively unpredictable so can’t be relied upon on their own for continuous power generation. The power P available from a wind turbine is given roughly by

P \simeq \frac{1}{2} \epsilon \rho A v^3

where v is the wind speed, A is the area of the turbine, \rho is the density of air, which is about 1.2 kg per cubic metre, and \epsilon is the efficiency with which the turbine converts the kinetic energy of the air into useable electricity.

The same formula would apply to a turbine placed in water, immediately showing the advantage of tidal power.  For comparable efficiencies and sizes the ratio of power generated in a tidal-stream turbine to a wind turbine would be

\frac{P_{t}}{P_{w}}\simeq \frac{\rho_{t}}{\rho_{w}} \left( \frac{v_{t}}{v_{w}}\right)^{3}

The speed of the water in a tidal stream can be comparable to the airspeed in a moderate wind, in which case the term in brackets doesn’t matter and it’s just the ratio of the densities of water and air that counts, and that’s a large number! Of course wind speed can sometimes be larger than the fastest tidal current, but wind turbines don’t work efficiently in such conditions and in any case it isn’t the v which provides the killer factor. The density of sea water is about 1025 kg per cubic metre, a thousand times greater than that of air. To get the same energy output from air as from a tidal stream you would need to have winds blowing steadily ten times the velocity of the stream, which would be about 80 knots for the Severn. More than breezy!

Not all proposals for the Severn Barrage involve tidal stream turbines. Some exploit the gravitational potential energy rather than the kinetic energy of the water by exploiting the vertical rise and fall during a tidal cycle rather than the horizontal flow. The energy to be exploited in, for example, a tidal basin of area A  would go as

E \simeq \frac{1}{2} \epsilon A\rho gh^{2}

where h is the vertical tidal range, about 8 metres for the Severn Estuary, and g is the acceleration due to gravity. The average power generated would be found by dividing this amount of energy by 12 hours, the time between successive high tides. It remains to be seen whether tidal basin or lagoon based on this principle emerges as competitive.

Another thing that struck me doodling these things on the back of an envelope in the garden is that this sort of thing is what we should be getting physics students to think about. I’m quite ashamed to admit that we don’t…

A Reith Lecture

Posted in Politics, The Universe and Stuff with tags , , on May 13, 2010 by telescoper

I’m a bit late getting around to blogging today, primarily because I spent the evening at a lecture by Martin Rees. Not just any lecture, but one of the annual series of Reith Lectures that he has been chosen to present this year. This event took place in the splendid Reardon Smith Theatre in the National Museum in Cardiff, and was preceded by a wine reception where we mingled amongst the relics of Welsh prehistory. The audience for the lecture  included academics, politicians, journalists and students and there was a lively question-and-answer session afterwards.

The Reith Lectures were inaugurated in 1948 by the BBC to mark the historic contribution made to public service broadcasting by Sir John (later Lord) Reith, the corporation’s first director-general. John Reith maintained that broadcasting should be a public service which enriches the intellectual and cultural life of the nation. It is in this spirit that the BBC each year invites a leading figure to deliver a series of lectures on radio. The aim is to advance public understanding and debate about significant issues of contemporary interest.

The very first Reith lecturer was the philosopher, Bertrand Russell who spoke on “Authority and the Individual”. Among his successors were Arnold Toynbee (The World and the West, 1952), Robert Oppenheimer (Science and the Common Understanding, 1953) and J.K. Galbraith (The New Industrial State, 1966). More recently, the Reith lectures have been delivered by the Chief Rabbi, Dr Jonathan Sacks (The Persistence of Faith, 1990) and Dr Steve Jones (The Language of the Genes, 1991). Since 2002, the Reith Lectures have been presented as was tonight’s,  by Sue Lawley.

I think this is the first time any of these lectures have been delivered in Cardiff. Martin Rees is, in fact, almost a Welshman himself ,  being born in Ludlow in Shropshire only about a mile the wrong side of the border; since being elevated to the peerage a few years ago, he is now known as Baron Rees of Ludlow. He is, of course, an immensely distinguished astrophysicist (he has been Astronomer Royal since 1995) but now has a broader portfolio of responsibility in the higher echelons of British science as President of the Royal Society.

As well as being an eminent scientist, Martin Rees is also a very fine public speaker, possessing an effortless gravitas that  any politician would die for.  He speaks with great clarity, thoughtfully and to the point, but with an economical use of language. He comes across as not only highly intelligent , which he undoubtedly is, but also deeply humane, another rare combination. Martin Rees was therefore an excellent choice to give the Reith Lectures. I had been looking forward to the evening for months after I got a phone call from Auntie Beeb asking me if I’d like to attend.

His lecture this evening wasn’t about astrophysics, and neither are the others in the series which has the pretty vague overall title Scientific Horizons. This lecture, the second of the series of four, was entitled Surviving the Century,and it concerned the role of science in identifying and possibly counteracting the threats facing humanity over the next few decades. He touched on climate change, renewable energy, and the possibility of nuclear or bio-terrorism. Although he spelled out the dangers in pretty stark terms he nevertheless claimed to be an optimist to the extent that he believed science could find solutions to the most pressing problems facing our planet, but I also sensed he was more of a pessimist as to whether the necessary measures could be implemented owing to socio-economic and political constraints. Science is vital to safeguarding the future of the planet, but it isn’t sufficient. People need to change the way they live their lives.

I won’t say any more about the lecture – or the interesting audience discussion that followed it – because you’ll be able to hear it yourselves on BBC Radio 4. The Lectures will be broadcast at 9am on Radio 4 starting on Tuesday 1st June (Lecture 1, called The Scientific Citizen). The lecture I attended tonight will be broadcast at the same time the following week (8th June). Lectures 3 and 4 will follow on 15th and 22nd June. Of course they will also be available as podcasts from the BBC website. If you want to be informed, enriched and challenged then I recommend you check them out.

Astronomy Look-alikes, No. 19

Posted in Astronomy Lookalikes with tags , on April 6, 2010 by telescoper

While watching Carry on Screaming on the telly tonight, I was reminded of the similarity in visual appearance possessed by the villainous Orlando (played by Kenneth Williams) and the distinguished Astronomer Royal, President of the Royal Society and Master of Trinity College, Cambridge, and the Universe, Lord Rees of Ludlow (who, I hasten to add, is not at all villainous..).

Lord Martin of Rees

Sir Kenneth of Williams

Cranks Anonymous

Posted in Biographical, Books, Talks and Reviews, The Universe and Stuff with tags , , , , on September 22, 2009 by telescoper

Sean Carroll, blogger-in-chief at Cosmic Variance, has ventured abroad from his palatial Californian residence and is currently slumming it in a little town called Oxford where he is attending a small conference in celebration of the 70th birthday of George Ellis. In fact he’s been posting regular live commentaries on the proceedings which I’ve been following with great interest. It looks an interesting and unusual meeting because it involves both physicists and philosophers and it is based around a series of debates on topics of current interest. See Sean’s posts here, here and here for expert summaries of the three days of the meeting.

Today’s dispatches included an account of George’s own talk which appears to have involved delivering a polemic against the multiverse, something he has been known to do from time to time. I posted something on it myself, in fact. I don’t think I’m as fundamentally opposed as Geroge to the idea that we might live in a bit of space-time that may belong to some sort of larger collection in which other bits have different properties, but it does bother me how many physicists talk about the multiverse as if it were an established fact. There certainly isn’t any observational evidence that this is true and the theoretical arguments usually advanced are far from rigorous.The multiverse certainly is  a fun thing to think about, I just don’t think it’s really needed.

There is one red herring that regularly floats into arguments about the multiverse, and that concerns testability. Different bits of the multiverse can’t be observed directly by an observer in a particular place, so it is often said that the idea isn’t testable. I don’t think that’s the right way to look at it. If there is a compelling physical theory that can account convincingly for a realised multiverse then that theory really should have other necessary consequences that are testable, otherwise there’s no point. Test the theory in some other way and you test whether the  multiverse emanating from it is sound too.

However, that fairly obvious statement isn’t really the point of this piece. As I was reading Sean’s blog post for today you could have knocked me down with a feather when I saw my name crop up:

Orthodoxy is based on the beliefs held by elites. Consider the story of Peter Coles, who tried to claim back in the 1990’s that the matter density was only 30% of the critical density. He was threatened by a cosmological bigwig, who told him he’d be regarded as a crank if he kept it up. On a related note, we have to admit that even scientists base beliefs on philosophical agendas and rationalize after the fact. That’s often what’s going on when scientists invoke “beauty” as a criterion.

George was actually talking about a paper we co-wrote for Nature in which we went through the different arguments that had been used to estimate the average density of matter in the Universe, tried to weigh up which were the more reliable, and came to the conclusion that the answer was in the range 20 to 40 percent of the critical density. There was a considerable theoretical prejudice at the time, especially from adherents of  inflation, that the density should be very close to the critical value, so we were running against the crowd to some extent. I remember we got quite a lot of press coverage at the time and I was invited to go on Radio 4 to talk about it, so it was an interesting period for me. Working with George was a tremendous experience too.

I won’t name the “bigwig” George referred to, although I will say it was a theorist; it’s more fun for those working in the field to guess for themselves! Opinions among other astronomers and physicists were divided. One prominent observational cosmologist was furious that we had criticized his work (which had yielded a high value of the density). On the other hand, Martin Rees (now “Lord” but then just plain “Sir”) said that he thought we were pushing at an open door and was surprised at the fuss.

Later on, in 1996, we expanded the article into a book in which we covered the ground more deeply but came to the same conclusion as before.  The book and the article it was based on are now both very dated because of the huge advances in observational cosmology over the last decade. However, the intervening years have shown that we were right in our assessment: the standard cosmology has about 30% of the critical density.

Of course there was one major thing we didn’t anticipate which was the discovery in the late 1990s of dark energy which, to be fair, had been suggested by others more prescient than us as early as 1990. You can’t win ’em all.

So that’s the story of my emergence as a crank, a title to which I’ve tried my utmost to do justice since then. Actually, I would have liked to have had the chance to go to George’s meeting in Oxford, primarily to greet my ertswhile collaborator whom I haven’t seen for ages. But it was invitation-only. I can’t work out whether these days I’m too cranky or not cranky enough to get to go to such things. Looking at the reports of the talks, I rather think it could be the latter.

Now, anyone care to risk the libel laws and guess who Professor BigWig was?

Budget Boost?

Posted in Science Politics with tags , , , , on April 19, 2009 by telescoper

This Wednesday (22nd April 2009) the Chancellor of the Exchequer, Alistair Darling, will deliver the UK government’s budget for this year. The background is of course the economic recession and the consequent collapse of our public finances. The government will have to borrow an estimated £175 billion over the next year, and it likely that taxes will eventually have to rise considerably to balance the books in the longer term.

Rumours are abounding about what will be in the budget and what won’t. According to today’s Observer, the centrepiece is likely to be a £50 billion scheme to revitalize the housing market.  If this is the case then I think it’s a mistake. Our economy has been run for too long on the basis of money raised from inflated property valuations, and we need to take this opportunity to change to a more sustainable way of running the country. Other schemes that may emerge include a £2 billion scheme to help unemployed young people which is a better idea, but much of it would probably be wasted in bureaucracy rather than doing real good.

My own attention will be focussed on whether there is anything in Alistair Darling’s speech that indicates some help for science, particularly fundamental science like physics and astronomy. In yesterday’s Guardian the Astronomer Royal and President of the Royal Society, Lord Martin Rees argued  for an injection of cash to stimulate science and innovation. About a month ago the BBC reported on efforts by Ministers to convince the treasury of the benefit of a £1 billion stimulus package for science along these lines. However, even if the powers that be listen to this argument (which is, in my view, unlikely), any increase in science funding would not necessarily be directed towards fundamental physics. I think if there isn’t anything for those of us working in astronomy in this budget, then we’re completely screwed.

I believe the funding crisis at the Science & Technology Facilities Council (STFC) was precipitated by a conscious government decision to move funds away from blue skies research and into more applied, technology driven areas.  The 2007 Comprehensive Spending Review was extremely tough on STFC but quite generous to some other agencies.  Moreover, within STFC itself there seems to be a shift from science-driven to technology-driven projects,  signalled by the cancellation of projects such as Clover to save a couple of million, and the allocation of funds to projects such as Moonlite which is devoid of any scientific interest and which could end up costing as much as £150 million over the next five years or so.

The true depth of the ongoing STFC crisis is only gradually becoming apparent. It was bad enough to start with, but has been exacerbated by the fall in value of sterling against the euro since 2007 which has meant that the cost of subscriptions to CERN, ESA and ESO have risen dramatically (by about 40%). These form such a large part of STFC’s expenditure – the CERN subscription alone is £70m out of a total budget of around £800m – that it cannot absorb the increased cost and it is now looking to make swingeing cuts on top of the 25% cut in research grants already implemented.

News emerged last week that STFC has abandoned plans to fund any R&D grants for ESA’s Cosmic Vision programme, and there are dark rumours circulating that it is considering cancelling all astronomy grants this year as well as clawing back money already given to universities in previous rounds. I hope these are not true, but I fear the worst.

Cuts on this scale would be devastating, demoralising, and I honestly think would destroy the United Kingdom as a place to do astronomy. They would also signal a complete breakdown of trust between scientists and the research council that is supposed to support them, if that hadn’t happened already.

Incidentally it is noticeable that STFC hasn’t bothered to report any of these matters publically through its website. Instead, the lead story on the STFC news page is about a visit by Prince Andrew to the Rutherford Appleton Lab. No sign yet, then, of the promised improvement in communication between the STFC Executive and its community.

The way I see it, the urgent issue is not whether we get a stimulus package , but whether we even get the bit of sticking plaster that is needed to  saves physics and astronomy from utter ruin. The cost would be a small fraction of the billions lavished on profligate bankers, but I’m not at all sure that the government either appreciates or cares about the scale of the problem.

Anyway, coincidentally, next week sees the Royal Astronomical Society’s National Astronomy Meeting (NAM), which is this year held jointly with the European Astronomical Society’s JENAM at the University of Hertfordshire. I won’t be going because it has unfortunately been organized in term time apparently because European astronomers refuse to attend meetings in the vacations, at least if they’re in places like Hatfield.  STFC representatives  have been invited; it remains to be seen what, if anything, they will have to say.