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The New Mariner

Posted in Poetry, The Universe and Stuff, Uncategorized with tags , , , , on November 16, 2014 by telescoper

In the silence
that is his chosen medium
of communication and telling
others about it
in words. Is there no way
not to be the sport
of reason? For me now
there is only the God-space
into which I send out
my probes. I had looked forward
to old age as a time
of quietness, a time to draw
my horizons about me,
to watch memories ripening
in the sunlight of a walled garden.
But there is the void
over my head and the distance
within that the tireless signals
come from. An astronaut
on impossible journeys
to the far side of the self
I return with the messages
I cannot decipher, garrulous
about them, worrying the ear
of the passer-by, hot on his way
to the marriage of plain fact with plain fact.

by Ronald Stuart Thomas (1913-2000)

 

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Rosetta and Philae: So Much More Than Science

Posted in The Universe and Stuff with tags , , , , on November 15, 2014 by telescoper

Time to break radio silence, so to speak, with a short post about the main event that’s happened in the astronomical world while I’ve been indisposed, namely the separation of the probe Philae from its parent spacecraft Rosetta and subsequent successful landing  on  Comet 67P/Churyumov-Gerasimenko. There’s been  a huge amount of media coverage and in-depth specialist analysis of this going on over the past few days, and it isn’t reallly in my own area of specialism, so there isn’t much point in trying to do my own version of events here. If you’re looking for a science briefing then you could do a lot worse than the official European Space Agency web pages here. I’ll confine myself to a few general reflections.

First, as has been widely reported, the final stages of Philae’s  approach were clearly a bit hairy (appropriately enough, since the word “comet” is derived from the Greek word for “hair”).  Although it homed in on its intended landing site pretty accurately, when it got close the thrusters intended to help it settle onto the surface didn’t fire and the “harpoons” supposed to fasten it to the surface also failed. As a consequence of all this, Philae bounced off the surface, floated in space for about two hrs, during which it travelled about 1km across the surface of the comet; that’s an average speed of about 0.14 m/s relative to the surface of the comet. It then encountered the surface again, bounced again for about 7 min, and then come to rest on 2 legs, with one pointing into space, against a cliff on the edge of a crater, with only one solar panel in operation because of the shade from the cliff.

It’s worth noting that the escape velocity from the surface of Comet 67P/Churyumov-Gerasimenko is only about 0.5 m/s and the probe met the surface of the comet at about twice that speed. Without significant intervention to stick it down, Philae could quite easily have bounced off and into space forever. The loss of the thruster and the failure of the harpoons made that a very likely outcome, but the mission’s luck held out. Fortune favours the brave.

Here’s just one of the remarkably vivid pictures taken of the surface of the Comet taken by Philae from its precarious resting place. I don’t know about you but to me it looks very eerie but at the same time it almost makes me feel like I am there in person, as if I could reach out and touch it…

comet_surface

It then became clear that the rate at which Philae was using power from its batteries was exceeding the rate at which it could recharge using its solar panel. For a time it was by no means obvious that it could perform all its science tasks in the short time (~60 hours) remaining before it would run out of juice, but in the end, according to the experts, it did accomplish about 80% of its science goals before going into hibernation.

I’ve heard some folk – including a few astronomers – claiming that Philae’s difficulties have cast a big shadow over the Rosetta mission. That’s clearly nonsense. In fact, the odds that Philae would ever  attach itself to its target were only about 50-50. And even if it did succed there was a chance some of its on board instruments may well have failed. After all, they had spent 10 years in the hostile environment of space waiting to be called into action. As it turned out, Philae’s achievements are at the upper end of the range of expectations. But even if the probe had failed entirely then there would still have been the huge amount of science being done by Rosetta itself. Overall, I think the mission so far has been a stunning success and there’s a lot more to come.

From a non-scientific point of view the perilous landing of Philae was even a bonus, as it made a public that is in danger of becoming blasé about spaceflight realise (a) that it is incredibly difficult and (b) there are people clever enough to make it work. The tension that mounted as events unfolded had people gripped largely because people could see in their mind’s eye this little thing, like a washing machine on legs, bouncing about in slow motion across an alien landscape. It was a drama largely acted out in our own imagination, and all the more absorbing for that.

Yesterday I was chatting with a friend who was trying to understand what Philae was doing as it bounced. It is quite difficult, if you think about it, to apply physical intuition to this situation. On the Earth we think of the “up” and “down” directions as being unambiguously defined, but “up” actually means two different things: (i) perpendicular to the Earth’s surface; and (ii) in the opposite direction to which gravity makes things fall (“down”) . On a spherical object such as a planet, gravity acts towards the centre, hence “what goes up  (i)  must come down  (ii)” .

Comet 67P/Churyumov-Gerasimenko, however, is far from spherical (even by the standards of a theoretical physicist):

Comet_close

This means that bouncing up off the surface does not necessarily result in coming straight back down again – gravity may well pull in a quite different direction. Add to that the spinning of the comet and its uneven surface, and you can understand how difficult it was to figure out where Philae ended up and precisely how it had got there!

Another comment I’ve heard concerns the cost. At €1.4 Billion it does sound expensive, but divide that among the population of the European Union (currently over 500 million) and it doesn’t sound so much, about the cost of a cup of coffee, and remember that the mission has lasted over years.  Philae has succeeded in generating a  huge amount of scientific data and I have no doubt that important conclusions will soon be drawn from the measurements it has made, but it’s not just the science that justifies the (modest) pricetag. Rosetta is an achievement that all humanity can celebrate. It is a demonstration of what we can achieve collectively if we have ambition, imagination and determination. Setting ourselves targets and reaching them. Asking ourselves questions and answering them. This is what makes us humans what we are. Venturing into space changes our perspective on our own world, something we need to do urgently if humanity is to survive on Earth.

 

 

 

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Wind versus Nuclear: The real story in pictures

Posted in Science Politics, The Universe and Stuff with tags , , , on November 5, 2014 by telescoper

Here’s an interesting, balanced analysis of the statistics of wind power versus nuclear power in the UK over the past couple of months. There’s obviously room for more growth in renewable energy generation, but I still think we’ll need to increase nuclear capacity to provide a counter to the intermittent variability of wind power if we are to reduce our dependency on fossil fuels, which still produce most of the UK’s energy…

Michael de Podesta's avatarProtons for Breakfast

Graph showing the electricity generated by nuclear and wind power (in gigawatts) every 5 minutes for the months of September and October 2014. The grey area shows the period when wind power exceeded nuclear power. Graph showing the electricity generated by nuclear and wind power (in gigawatts) every 5 minutes for the months of September and October 2014. The grey area shows the period when wind power exceeded nuclear power. (Click Graph to enlarge)

For a few days in October 2014,  wind energy consistently generated more electricity in the UK than nuclear power. Wow!

You may have become aware of this through several news outlets. The event was reported on the BBC, but curiously the Daily Mail seems not to have noticed .

Alternatively, you may like me, have been watching live on Gridwatch – a web site that finally makes the data on electricity generation easily accessible.

I was curious about the context of this achievement and so I downloaded the historically archived data on electricity generation derived from coal, gas, nuclear and wind generation in the UK for the last three years. (Download Page)

And graphing the…

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Science, Poetry and Romanticism

Posted in Poetry, The Universe and Stuff with tags , , , , , , on November 4, 2014 by telescoper

I listened to a very interesting programme on BBC Radio 3 on Sunday evening, part of which was a documentary about science and poetry presented by Gregory Tate. Given that both these subjects feature heavily on this blog I couldn’t resist a quick post about it.

The feature explored why so many scientists have been inspired to write poetry, and the nature of the relationship between their artistic work and their science.

Among the famous scientists included in the programme was chemist and inventor Humphry Davy who, inspired by his friendship with the poets Wordsworth and Coleridge, wrote poems throughout his life. Others to do likewise were: physician Eramus Darwin; mathematician William Rowan Hamilton; astronomer William Herschel (who was also a noted musician and composer); J. Robert Oppenheimer; and Erwin Schrödinger.

Doing a quick google about after the programme I came across this example by Hamilton, which I searched for because he is the scientist from the list above with whose mathematical work I am most familiar because of its huge influence on physics, and because he seems to have been a very colourful character as well as a superb mathematician. Interestingly, he too was a very close friend of Wordsworth, to whom he often sent poems with requests for comments and feedback. In the subsequent correspondence, Wordsworth was usually not very complimentary even to the extent of telling Hamilton to stick to his day job (or words to that effect). What I didn’t know was that Hamilton regarded himself as a poet first and a mathematician second. That just goes to show you shouldn’t necessarily trust a man’s judgement when he applies it to himself.

Here’s an example of Hamilton’s verse – a poem written to honour Joseph Fourier:

Hamilton-for Fourier

If that’s one of his better poems, then I think Wordsworth may have had a point!

The serious thing that struck me about this programme though was how many scientists of the 19th Century, Hamilton included, saw their scientific interrogation of Nature as a manifestation of the human condition just as the romantic poets saw their artistic contemplation. It is often argued that romanticism is responsible for the rise of antiscience. I’m not really qualified to comment on that but I don’t see any conflict at all between science and romanticism. I certainly don’t see Wordsworth’s poetry as antiscientific. I just find it inspirational:

I HAVE seen
A curious child, who dwelt upon a tract
Of inland ground, applying to his ear
The convolutions of a smooth-lipped shell;
To which, in silence hushed, his very soul
Listened intensely; and his countenance soon
Brightened with joy; for from within were heard
Murmurings, whereby the monitor expressed
Mysterious union with its native sea.
Even such a shell the universe itself
Is to the ear of Faith; and there are times,
I doubt not, when to you it doth impart
Authentic tidings of invisible things;
Of ebb and flow, and ever-during power;
And central peace, subsisting at the heart
Of endless agitation.

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Three Minutes of Cosmology

Posted in The Universe and Stuff with tags , , on October 29, 2014 by telescoper

Not much time today to do anything except help one of my former PhD students become a Youtube sensation by sharing this video of Ian Harrison. Ian did his doctorate with me in Cardiff but now works in the Midlands, at the University of Manchester. Here he is talking about part of his PhD work for just three minutes without repetition, hesitation, deviation, or repetition:

 

 

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Why Cosmology Isn’t Boring

Posted in Brighton, The Universe and Stuff with tags , , , on October 23, 2014 by telescoper

As promised yesterday, here’s a copy of the slides I used for my talk to the ~150 participants of the collaboration meeting of the Dark Energy Survey that’s going on here this week at Sussex. The title is a reaction to a statement I heard that recent developments in cosmology, especially from Planck, have established that we live in a “Maximally Boring Universe”. I the talk I tried to explain why I don’t think the standard cosmology is at all boring. In fact, I think it’s only now that we can start to ask the really interesting questions.

At various points along the way I stopped to sample opinions…

IMG-20141022-00439

I did however notice that Josh Frieman (front left) seemed to vote in favour of all the possible options on all the questions.  I think that’s taking the multiverse idea a bit too far..

 

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Cosmology, to be precise…

Posted in The Universe and Stuff with tags , on October 22, 2014 by telescoper

After an extremely busy morning I had the pleasant task this afternoon of talking to the participants of a collaboration meeting of the Dark Energy Survey that’s going on here at Sussex. Now there’s the even more pleasant task in front of me of having drinks and dinner with the crowd. At some point I’ll post the slides of my talk on here, but for the mean time here’s a pretty accurate summary..

Summary

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Controlled Nuclear Fusion: Forget about it

Posted in The Universe and Stuff with tags , , , on October 20, 2014 by telescoper

You’ve probably heard that Lockheed Martin has generated a lot of excitement with a recent announcement about a “breakthrough” in nuclear fusion technology. Here’s a pessimistic post from last year. I wonder if it will be proved wrong?

Michael de Podesta's avatarProtons for Breakfast

Man or woman doing a technical thing with a thingy told with laser induced nuclear fusion. Man or woman adjusting the ‘target positioner’ (I think) within the target chamber of the US Lawrence Livermore National Laboratory.

The future is very difficult to predict. But I am prepared to put on record my belief that controlled nuclear fusion as a source of power on Earth will never be achieved.

This is not something I want to believe. And the intermittent drip of news stories about ‘progress‘ and ‘breakthroughs‘ might make one think that the technique would eventually yield to humanity’s collective ingenuity.

But  in fact that just isn’t going to happen. Let me explain just some of the problems and you can judge for yourself whether you think it will ever work.

One option for controlled fusion is called Inertial Fusion Energy, and the centre of research is the US National Ignition Facility. Here the most powerful laser…

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What’s the point of conferences?

Posted in Education, The Universe and Stuff with tags , , , , , on October 19, 2014 by telescoper

Well, here I am back in the office making a start on my extensive to-do list. Writing it, I mean. Not actually doing any of it.

It was nice to get away for a couple of weeks, to meet up with some old friends I haven’t seen for a while and also to catch up on some of the developments in my own field and other related areas. We do have pretty good seminar series here at Sussex which should in principle allow me to keep up to date with developments in my own research area, but unfortunately the timing of these events often clashes with other meetings  that I’m obliged to attend as Head of School. Escaping to a conference is a way of focussing on research for a while without interruption. At least that’s the idea.

While at the meeting, however, I was struck by a couple of things. First was that during the morning plenary lectures given by invited speakers almost everyone in the audience was spending much more time working on their laptops than listening to the talk.  This has been pretty standard at every meeting I’ve been to for the last several years. Now that everyone uses powerpoint (or equivalent) for such presentations nobody in the audience feels the need to take notes so to occupy themselves they spend the time answering emails or pottering about on Facebook. That behaviour does not depend on the quality of the talk, either. Since nobody seems to listen very much the question naturally arises as to whether the presentations have any intrinsic value at all. It often seems to me that the conference talk has turned into a kind of ritual that persists despite nobody really knowing what it’s for or how it originated. An hour is too long to talk if you really want people to listen, but we go on doing it.

The part of a conference session that’s more interesting is the discussion after each talk. Sometimes there’s a genuine discussion from which you learn something quite significant or get an idea for a new study.  There’s often also a considerable amount of posturing, preening and point-scoring which is less agreeable but in its own way I suppose fairly interesting.

At the meeting I was attending the afternoons were devoted to discussion sessions for which we split into groups. I was allocated to “Gravitation and Cosmology”; others were on “Cosmic Rays”, “Neutrino Physics and Astrophysics”, and so on. The group I was, of about 25 people, was a nice size for discussion. These sessions were generally planned around short “informal” presentations intended to stimulate discussion, but generally these presentations were about the same length as the plenary talks and also given in Powerpoint. There was discussion, but the format turned out to be less different from the morning sessions than I’d hoped for. I’m even more convinced than ever that Powerpoint presentations used in this way stifle rather than stimulate discussion and debate. The pre-prepared presentation is often used as a crutch by a speaker reluctant to adopt a more improvisatory approach that would probably be less polished but arguably more likely to generate new thoughts.

I don’t know whether the rise of Powerpoint is itself to blame for our collective unwillingness inability to find other ways of talking about science, but I’d love to try organizing a workshop or conference along lines radically different from the usual “I talk, you listen” format in which the presenter is active and the audience passive for far too long.

All this convinced me that the answer to the question “What is the point of conferences?” has very little to do with the formal  programme and more with the informal parts, especially the conversations over coffee and at dinner. Perhaps I should try arranging a conference that has nothing but dinner and coffee breaks on the schedule?

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Dark Matter from the Sun?

Posted in The Universe and Stuff with tags , , , , , , , on October 16, 2014 by telescoper

This afternoon while I was struggling to pay attention during one of the presentations at the conference I’m at, when I noticed a potentially interesting story going around on Twitter. A little bit of research revealed that it relates to a paper on the arXiv, with the title Potential solar axion signatures in X-ray observations with the XMM-Newton observatory by Fraser et al. The first author of this paper was George Fraser of the University of Leicester who died the day after it was submitted to Monthly Notices of the Royal Astronomical Society. The paper has now been accepted and the final version has appeared on the arXiv in advance of its publication on Monday. The Guardian has already run a story on it.

This is the abstract:

The soft X-ray flux produced by solar axions in the Earth’s magnetic field is evaluated in the context of ESA’s XMM-Newton observatory. Recent calculations of the scattering of axion-conversion X-rays suggest that the sunward magnetosphere could be an observable source of 0.2-10 keV photons. For XMM-Newton, any conversion X-ray intensity will be seasonally modulated by virtue of the changing visibility of the sunward magnetic field region. A simple model of the geomagnetic field is combined with the ephemeris of XMM-Newton to predict the seasonal variation of the conversion X-ray intensity. This model is compared with stacked XMM-Newton blank sky datasets from which point sources have been systematically removed. Remarkably, a seasonally varying X-ray background signal is observed. The EPIC count rates are in the ratio of their X-ray grasps, indicating a non-instrumental, external photon origin, with significances of 11(pn), 4(MOS1) and 5(MOS2) sigma. After examining the constituent observations spatially, temporally and in terms of the cosmic X-ray background, we conclude that this variable signal is consistent with the conversion of solar axions in the Earth’s magnetic field. The spectrum is consistent with a solar axion spectrum dominated by bremsstrahlung- and Compton-like processes, i.e. axion-electron coupling dominates over axion-photon coupling and the peak of the axion spectrum is below 1 keV. A value of 2.2e-22 /GeV is derived for the product of the axion-photon and axion-electron coupling constants, for an axion mass in the micro-eV range. Comparisons with limits derived from white dwarf cooling may not be applicable, as these refer to axions in the 0.01 eV range. Preliminary results are given of a search for axion-conversion X-ray lines, in particular the predicted features due to silicon, sulphur and iron in the solar core, and the 14.4 keV transition line from 57Fe.

The paper concerns a hypothetical particle called the axion and I see someone has already edited the Wikipedia page to mention this new result. The idea of the axion has been around since the 1970s, when its existence was posited to solve a problem with quantum chromodynamics, but it was later realised that if it had a mass in the correct range it could be a candidate for the (cold) dark matter implied to exist by cosmological observations. Unlike many other candidates for cold dark matter, which experience only weak interactions, the axion feels the electromagnetic interaction, despite not carrying an electromagnetic charge. In particular, in a magnetic field the axion can convert into photons, leading to a number of ways of detecting the particle experimentally, none so far successful. If they exist, axions are also expected to be produced in the core of the Sun.

This particular study involved looking at 14 years of X-ray observations in which there appears to be an unexpected seasonal modulation in the observed X-ray flux which could be consistent with the conversion of axions produced by the Sun into X-ray photons as they pass through the Earth’s magnetic field. Here is a graphic I stole from the Guardian story:

axions

Conversion of axions into X-rays in the Earth’s magnetic field. Image Credit: University of Leicester

I haven’t had time to do more than just skim the paper so I can’t comment in detail; it’s 67 pages long. Obviously it’s potentially extremely exciting but the evidence that the signal is produced by axions is circumstantial and one would have to eliminate other possible causes of cyclical variation to be sure. The possibilities that spring first to mind as an alternatives to the axion hypothesis relate to the complex interaction between the solar wind and Earth’s magnetosphere. However, if the signal is produced by axions there should be characteristic features in the spectrum of the X-rays produced that would appear be very difficult to mimic. The axion hypothesis is therefore eminently testable, at least in principle, but current statistics don’t allow these tests to be performed. It’s tantalising, but if you want to ask me where I’d put my money I’m afraid I’d probably go for messy local plasma physics rather than anything more fundamental.

It seems to me that this is in some sense a similar situation to that of BICEP2: a potentially exciting discovery, which looks plausible, but with alternative (and more mundane) explanations not yet definitively ruled out. The difference is of course that this “discovery paper” has been refereed in the normal way, rather than being announced at a press-conference before being subjected to peer review…

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