Archive for October, 2013

Busy Busy Bee…

Posted in Uncategorized with tags , , on October 26, 2013 by telescoper

I saw this the other day and thought I’d post it here because it’s so fascinating. I’ve seen a few of these little bees on the Falmer campus of the University of Sussex, actually, but didn’t know what they were and  pay much attention to them. The species is Osmia bicolor, a beautiful solitary bee that inhabits chalk grassland and nests in old snail shells. This one is bringing pieces of grass to camouflage the shell in which she has nested; the video was filmed on the University of Sussex campus.

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We few, we happy few..

Posted in Film, Literature with tags , , , on October 25, 2013 by telescoper

In case you didn’t know, today is St Crispin’s Day. It’s also the anniversary of the Battle of Agincourt, which took place on this day in 1415, and which features in Shakespeare’s Henry V. Here is the famous St Crispin’s Day Speech, delivered in stirring style by Laurence Olivier, in the classic 1944 film.

And here is the orginal text, slightly different from the film version,  Henry V in Act IV Scene iii 18-67. Scene: The English Camp:

WESTMORELAND. O that we now had here
But one ten thousand of those men in England
That do no work to-day!

KING. What’s he that wishes so?
My cousin Westmoreland? No, my fair cousin;
If we are mark’d to die, we are enow
To do our country loss; and if to live,
The fewer men, the greater share of honour.
God’s will! I pray thee, wish not one man more.
By Jove, I am not covetous for gold,
Nor care I who doth feed upon my cost;
It yearns me not if men my garments wear;
Such outward things dwell not in my desires.
But if it be a sin to covet honour,
I am the most offending soul alive.
No, faith, my coz, wish not a man from England.
God’s peace! I would not lose so great an honour
As one man more methinks would share from me
For the best hope I have. O, do not wish one more!
Rather proclaim it, Westmoreland, through my host,
That he which hath no stomach to this fight,
Let him depart; his passport shall be made,
And crowns for convoy put into his purse;
We would not die in that man’s company
That fears his fellowship to die with us.
This day is call’d the feast of Crispian.
He that outlives this day, and comes safe home,
Will stand a tip-toe when this day is nam’d,
And rouse him at the name of Crispian.
He that shall live this day, and see old age,
Will yearly on the vigil feast his neighbours,
And say “To-morrow is Saint Crispian.”
Then will he strip his sleeve and show his scars,
And say “These wounds I had on Crispian’s day.”
Old men forget; yet all shall be forgot,
But he’ll remember, with advantages,
What feats he did that day. Then shall our names,
Familiar in his mouth as household words-
Harry the King, Bedford and Exeter,
Warwick and Talbot, Salisbury and Gloucester-
Be in their flowing cups freshly rememb’red.
This story shall the good man teach his son;
And Crispin Crispian shall ne’er go by,
From this day to the ending of the world,
But we in it shall be remembered-
We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother; be he ne’er so vile,
This day shall gentle his condition;
And gentlemen in England now-a-bed
Shall think themselves accurs’d they were not here,
And hold their manhoods cheap whiles any speaks
That fought with us upon Saint Crispin’s day.

Tension in Cosmology?

Posted in Astrohype, Bad Statistics, The Universe and Stuff with tags , , , on October 24, 2013 by telescoper

I noticed this abstract (of a paper by Rest et al.) on the arXiv the other day:

We present griz light curves of 146 spectroscopically confirmed Type Ia Supernovae (0.03<z<0.65) discovered during the first 1.5 years of the Pan-STARRS1 Medium Deep Survey. The Pan-STARRS1 natural photometric system is determined by a combination of on-site measurements of the instrument response function and observations of spectrophotometric standard stars. We have investigated spatial and time variations in the photometry, and we find that the systematic uncertainties in the photometric system are currently 1.2% without accounting for the uncertainty in the HST Calspec definition of the AB system. We discuss our efforts to minimize the systematic uncertainties in the photometry. A Hubble diagram is constructed with a subset of 112 SNe Ia (out of the 146) that pass our light curve quality cuts. The cosmological fit to 313 SNe Ia (112 PS1 SNe Ia + 201 low-z SNe Ia), using only SNe and assuming a constant dark energy equation of state and flatness, yields w = -1.015^{+0.319}_{-0.201}(Stat)+{0.164}_{-0.122}(Sys). When combined with BAO+CMB(Planck)+H0, the analysis yields \Omega_M = 0.277^{+0.010}_{-0.012} and w = -1.186^{+0.076}_{-0.065} including all identified systematics, as spelled out in the companion paper by Scolnic et al. (2013a). The value of w is inconsistent with the cosmological constant value of -1 at the 2.4 sigma level. This tension has been seen in other high-z SN surveys and endures after removing either the BAO or the H0 constraint. If we include WMAP9 CMB constraints instead of those from Planck, we find w = -1.142^{+0.076}_{-0.087}, which diminishes the discord to <2 sigma. We cannot conclude whether the tension with flat CDM is a feature of dark energy, new physics, or a combination of chance and systematic errors. The full Pan-STARRS1 supernova sample will be 3 times as large as this initial sample, which should provide more conclusive results.

The mysterious Pan-STARRS stands for the Panoramic Survey Telescope and Rapid Response System, a set of telescopes cameras and related computing hardware that monitors the sky from its base in Hawaii. One of the many things this system can do is detect and measure distant supernovae, hence the particular application to cosmology described in the paper. The abstract mentions a preliminary measurement of the parameter w, which for those of you who are not experts in cosmology is usually called the “equation of state” parameter for the dark energy component involved in the standard model. What it describes is the relationship between the pressure P and the energy density ρc2 of this mysterious stuff, via the relation P=wρc2. The particularly interesting case is w=-1 which corresponds to a cosmological constant term; see here for a technical discussion. However, we don’t know how to explain this dark energy from first principles so really w is a parameter that describes our ignorance of what is actually going on. In other words, the cosmological constant provides the simplest model of dark energy but even in that case we don’t know where it comes from so it might well be something different; estimating w from surveys can therefore tell us whether we’re on the right track or not.

The abstract explains that, within the errors, the Pan-STARRS data on their own are consistent with w=-1. More interestingly, though, combining the supernovae observations with others, the best-fit value of w shifts towards a value a bit less than -1 (although still with quite a large uncertainty). Incidentally  value of w less than -1 is generally described as a “phantom” dark energy component. I’ve never really understood why…

So far estimates of cosmological parameters from different data sets have broadly agreed with each other, hence the application of the word “concordance” to the standard cosmological model.  However, it does seem to be the case that supernova measurements do generally seem to push cosmological parameter estimates away from the comfort zone established by other types of observation. Could this apparent discordance be signalling that our ideas are wrong?

That’s the line pursued by a Scientific American article on this paper entitled “Leading Dark Energy Theory Incompatible with New Measurement”. This could be true, but I think it’s a bit early to be taking this line when there are still questions to be answered about the photometric accuracy of the Pan-Starrs survey. The headline I would have picked would be more like “New Measurement (Possibly) Incompatible With Other Measurements of Dark Energy”.

But that would have been boring…

Planck and Being Human

Posted in The Universe and Stuff with tags , , , on October 23, 2013 by telescoper

On Saturday 19th October the instruments and cooling systems on the European Space Agency’s Planck spacecraft were switched off, marking the end of the scientific part of the Planck mission, after about four years of mapping the cosmic microwave background.  Later, a piece of software was uploaded that would prevent  the spacecraft systems being  accidentally switched on again after being switched off and the transmitter from causing interference with any future probes.  Planck is already “parked” indefinitely in a what is called a “disposal” orbit, far from the Earth-Moon system, having been nudged off its perch at the 2nd Lagrangian Point (L2) in August by a complicated series of manoeuvres. On October 21st the spacecraft’s thrusters were fired to burn up the last of its fuel, an important aspect of rendering the spacecraft inert, as required by ESA’s space debris mitigation guidelines.

Planck

These preliminaries having been completed, today, at 12.00 GMT,  a final instruction will be transmitted to the spacecraft  to close it down permanently; thereafter Planck will circle the Sun as a silent memorial to the stunning success it achieved when active. I’m sure all those who worked on the Planck mission will pause as the final shutdown command is given and ponder the lonely future  of the spacecraft that had supplied so much interesting data.

But although this will be the end of the Planck mission, it is by no means the end of the Planck Era. Vast amounts of data still need to be fully analysed and key science results are still in the pipeline,  relating in particular to the polarization of the microwave background radiation. Moreover, the numerous maps, catalogues and other data products will be a priceless legacy to this generation, and no doubt many future generations, of scientists.

The fate of Planck illustrates two contrasting aspects of the human experience. On the one hand, there’s the fragility of our existence in a cosmos too vast for us to comprehend. Like the defunct spacecraft, our Earth too circles this little Sun of ours in a precarious orbit while the rest of the Universe – with its countless billion upon billion of other suns – carries on, oblivious to our very existence. Planck makes us painfully aware of our own insignificance.

But on the other hand there’s the sense of fulfillment, and even of joy, at finding things out. We may have puny monkey brains and many things are likely to remain forever beyond our mental grasp, but trying to figure things out is one of the things that defines us as human.  Experiments like Planck (and, for that matter, the Large Hadron Collider) are not the wasteful extravagance some people claim them to be. We need them not just for the sake of science, but to remind us of our common humanity.

UPDATE: And now, from ESA, confirmation that Planck has received its last command. Goodbye, and enjoy your retirement!

Introduction to the PhD for Physics or Astronomy students

Posted in Education with tags , , , , , , on October 22, 2013 by telescoper

It’s the time of year when final-year students start to think about the possibility of doing a PhD after they have graduated, so I I thought I’d jot down here a few general remarks that might be useful to people who are thinking of taking the plunge. I’ve posted on such matters before, but this is something that comes around every year so I hope you’ll excuse the repeat. I’m aiming this primarily at UK students applying for places in the UK; special considerations apply for students wanting to do graduate research abroad.

What is a PhD? The answer to that is relatively easy; it’s a postgraduate research degree. In order to obtain a PhD you have to present a thesis like that shown on the left (which happens to be mine, vintage 1988), typically in the range 100-250  pages long. A thesis has to satisfy two conditions for the award of the degree: it should contain original research, which is publishable in an academic journal; and it should present a coherent discussion of that original work within the context of ongoing work in the area of study. In Physics & Astronomy, the PhD is pretty much a prerequisite for any career in academic research, and it usually takes between 3 and 4 years to complete. After submission of the thesis you will have to undergo a viva voce examination conducted by two examiners, one internal and one external. This is quite a tough test, which  can last anywhere between about 2 and about 6 hours, during which you can be asked  detailed questions about your research and wide-ranging questions about the general area.

The Money Side. In the UK most PhDs are supported financially by the research councils, either EPSRC (most physics) or STFC (nuclear & particle physics, astronomy). These generally award quotas of studentships to departments who distribute them to students they admit. A studentship will cover your fees and pay a stipend, currently £13590 pa. That doesn’t sound like a lot, but you should at least remember that it is a stipend rather than a wage; it is therefore not taxed and there is no national insurance payable.

How do I choose a PhD? During the course of a postgraduate degree you are expected to become an expert in the area in which you specialize. In particular you should reach the point where you know more about that specific topic than your supervisor does. You will therefore have to work quite a lot on your own, which means you need determination, stamina and enthusiasm. In my view the most important criterion in your choice of PhD is not the institution where you might study but the project. You need to be genuinely excited by the topic in order to drive yourself to keep through the frustrations (of which there will be many). So, find an area that interests you and find the departments that do active research in that area by looking on the web. Check out the recent publications by staff in each department, to ensure that they are active and to have something to talk about at interview!

Qualifications. Most universities have a formal requirement that candidates for admission to the PhD should have a “good honours degree”, which basically means at least an Upper Second Class Honours degree. Some areas are more competitive than others, however, and in many disciplines you will find you are competing with a great many applicants with First Class degrees.

How to apply successfully. The application procedure at most universities is quite simple and can be done online. You will need to say something about the area in which you wish to do research (e.g. experiment/theory, and particular field, e.g. cosmology or star formation). You’ll also need a CV and a couple of references. Given the competition, it’s essential that you prepare. Give your curriculum vitae some attention, and get other people (e.g. your personal tutor) to help you improve it. It’s worth emphasizing particular skills (e.g. computing). If you get the chance, make use of your summer vacations by taking on an internship or other opportunity to get a taste of research; things like that will undoubtedly give your CV an edge.

The Interview. Good applicants will be invited for an interview, which is primarily to assess whether you have the necessary skills and determination, but also to match applicants to projects and supervisors. Prepare for your interview! You will almost certainly be asked to talk about your final-year project, so it will come across very badly if you’re not ready when they ask you. Most importantly, mug up about your chosen field. You will look really silly if you haven’t the vaguest idea of what’s going on in the area you claimed to be interested in when you wrote your  application!

Don’t be shy! There’s nothing at all wrong with being pro-active about this process. Contact academic staff at other universities by email and ask them about research, PhD opportunities. That will make a good impression. Also, don’t be afraid to ask for advice. Although we’re all keen to recruit good PhD students for our own departments, we academics are  conscious that it is also our job to give impartial advice. Ask your tutor’s opinion.

How many places should I apply for? Some research areas are more fashionable than others so the level of competition varies with field. As a general rule I would advise applying for about half-a-dozen places, chosen because they offer research in the right area. Apply to fewer than that and you might lose out to the competition. Apply to many more and you might not have time to attend the interviews.

What’s the timetable?  Most applications come in early in the new year for entry to the PhD in the following October. The Christmas break is therefore a pretty good time to get your applications sorted out. Interviews are normally held in February or March, and decisions made by late March. STFC runs a deadline system whereby departments can not force students to accept or decline offers before the end of March, so there should be ample time to visit all your prospective departments before having to make any decisions.

Here are some of the slides I used for a talk on such matters a year or so ago, which you might find useful.

That’s all I can think of for now. I hope at least some of these comments are useful to undergraduates anywhere in the UK thinking of applying for a PhD. If there are any further questions, please feel free to ask through the comments box. Likewise if I’ve missed anything important, please feel free to suggest additions in the same manner…

Updates for Cosmology: A Very Short Introduction?

Posted in Books, Talks and Reviews, The Universe and Stuff with tags , , , , , on October 21, 2013 by telescoper

Yet another very busy day, travelling in the morning and then in meetings all afternoon, so just time for another brief post. I thought I’d take the opportunity to do a little bit of crowdsourcing…

A few days ago I was contacted by Oxford University Press who are apparently considering the possibility of a second edition of my little book Cosmology: A Very Short Introduction, which is part of an extensive series of intensive books on all kinds of subjects.

I really enjoyed writing this book, despite the tough challenge of trying to cover the whole of cosmology in less than 35,000 words and was very pleased with the way it turned out. It has sold over 25000 copies in English and has been published in several other languages.

It is meant to be accessible to the interested layperson but the constraints imposed by the format mean it goes fairly quickly through some quite difficult concepts. Judging by the reviews, though, most people seem to think it gives a useful introduction to the subject, although you can’t please all of the people all of the time!

However, the book was published way back in 2001 and, well, one or two things have happened in the field of cosmology since then.  I have in fact had a number of emails from people asking whether there was going to be a new edition to include the latest developments, but the book is part of a very large series and it was basically up to the publisher to decide whether it wanted to update some, all or none of the series.

Now it seems the powers that be at OUP have decided to explore the possibility further and have asked me to make a pitch for a new edition.  I have some ideas of things that would have to be revised – the section on Dark Energy definitely needs to be updated, and of course first WMAP and then Planck have refined our view of the cosmic microwave background pretty comprehensively?

Anyway, I thought it would be fun to ask people out there who have read it, or even those who haven’t, what they feel I should change for a new edition if there is to be one. That might include new topics or revisions of things that could be improved. Your comments are therefore invited via the famous Comments Box. Please bear in mind that any new edition will be also constrained to be no more than 35,000 words.

Oh, and if you haven’t seen the First Edition at all, why not rush out and buy a copy before it’s too late? I understand you can snap up a copy for just £3 while stocks last. I can assure you all the royalties will go to an excellent cause. Me.

What, no Hammett?

Posted in Literature with tags , , , on October 20, 2013 by telescoper

I just took a break from work to have a look through the Sunday newspapers. In the Independent on Sunday I found an artincle about a new poll by the Crime Writers’ Association, which invites the public to vote on the best crime novel ever written.

I’m not going to quibble with the entire shortlist of ten books as such things are never going to generate a consensus. I will, however, admit being a bit annoyed with it for two reasons.

The first reason is the presence on the list of The Big Sleep by Raymond Chandler. Now don’t get me wrong, I think Chandler was a fine novelist. This particular book, though, is very far from his best work. It is notable for being the first novel to feature his detective Philip Marlowe, but the plot has too many gaps for it to be considered a great example of the genre. Perhaps the shocking nature of the plot, which revolves around drugs, pornography and sexual exploitation, has drawn attention away from these flaws. Anyway it wouldn’t be in my top ten. Chandler’s other book on the shortlist, The Long Goodbye is another story – it’s completely marvellous and thoroughly deserves its place on the list.

The second reason is the absence from the selection of any of the great novels by Dashiell Hammett. The Dain Curse, The Glass Key, Red Harvest and of course The Maltese Falcon are all contenders, in my opinion.

I just can’t understand why the Crime Writers’ Association picked an inferior Chandler over a brilliant Hammett.

Incidentally I don’t think Raymond Chandler would have disagreed. He was well aware of the failings of The Big Sleep and of Hammett he wrote:

Hammett gave murder back to the kind of people that commit it for reasons, not just to provide a corpse; and with the means at hand, not with hand-wrought duelling pistols, curare and tropical fish. He took murder out of the Venetian vase and dropped it in the alley. He was spare, frugal, hard-boiled, but he did over and over again what only the best writers can ever do at all. He wrote scenes that seemed never to have been written before.

There. I’ve said my piece. At least Hammett is on the list for the best Crime Writer. And by way of protest I’m going to have a glass of wine and watch a DVD of The Glass Key starring Alan Ladd and Veronica Lake, a classic film noir adapted from Hammett’s great novel.