The previous old conference photograph I posted seemed to be quite popular, so I thought I’d try an even older vintage. This was also taken at Durham, but at a meeting entitled The Epoch of Galaxy Formation, which took place between July 18th and 22nd 1988. Appropriately enough, this one is in glorious monochrome. Spot any familiar faces?
Although it’s a little late I thought I’d just put up a brief post to draw your attention to the news that a couple of technical papers have appeared on the arXiv giving updated details of the recent discovery at the Large Hadron of a new scalar particle that could be the Higgs boson. I don’t think it’s yet absolutely proven that this is what the new particle is, which is why I’ve called it the “LHC boson” in the title.
The ATLAS paper reports the detection of a Higgs-like particle with a 5.9 sigma confidence level, up from the 5.0 sigma reported on July 4. Here’s the abstract:
A search for the Standard Model Higgs boson in proton-proton collisions with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities of approximately 4.8 fb^-1 collected at sqrt(s) = 7 TeV in 2011 and 5.8 fb^-1 at sqrt(s) = 8 TeV in 2012. Individual searches in the channels H->ZZ^(*)->llll, H->gamma gamma and H->WW->e nu mu nu in the 8 TeV data are combined with previously published results of searches for H->ZZ^(*), WW^(*), bbbar and tau^+tau^- in the 7 TeV data and results from improved analyses of the H->ZZ^(*)->llll and H->gamma gamma channels in the 7 TeV data. Clear evidence for the production of a neutral boson with a measured mass of 126.0 +/- 0.4(stat) +/- 0.4(sys) GeV is presented. This observation, which has a significance of 5.9 standard deviations, corresponding to a background fluctuation probability of 1.7×10^-9, is compatible with the production and decay of the Standard Model Higgs boson.
The paper from CMS reinforces the discovery of a Higgs-like particle with a mass of 125 GeV at a 5-sigma level of confidence:
Results are presented from searches for the standard model Higgs boson in proton-proton collisions at sqrt(s)=7 and 8 TeV in the CMS experiment at the LHC, using data samples corresponding to integrated luminosities of up to 5.1 inverse femtobarns at 7 TeV and 5.3 inverse femtobarns at 8 TeV. The search is performed in five decay modes: gamma gamma, ZZ, WW, tau tau, and b b-bar. An excess of events is observed above the expected background, a local significance of 5.0 standard deviations, at a mass near 125 GeV, signalling the production of a new particle. The expected significance for a standard model Higgs boson of that mass is 5.8 standard deviations. The excess is most significant in the two decay modes with the best mass resolution, gamma gamma and ZZ; a fit to these signals gives a mass of 125.3 +/- 0.4 (stat.) +/- 0.5 (syst.) GeV. The decay to two photons indicates that the new particle is a boson with spin different from one.
I’ll refrain from commenting on the use of frequentist language in both these papers, but instead just comment that these extremely important papers are available for free on the arXiv. Open access, we call it.
PS. There’s an interesting blog post related to these papers, about citations in particle physics here.
Follow @telescoperYesterday’s old photograph reminded me of this classic from Private Eye ages ago. It appeared originally in the Guardian (before it went all Helvetica). Sorry it’s a bit battered…
I came across this old picture in my office today and couldn’t resist posting it for nostalgia’s sake. It was taken at a NATO Advanced Research Workshop called Observational Tests of Inflation, which took placed in Durham in December 1990. You’ll probably need to click on the image to be able to recognize faces, but I should at least point out Sir Fred Hoyle in the turquoise jacket in the front row; I am behind in the red and white T-shirt and black waistcoat. In those days I was considered quite trendy, among cosmologists.
You can also see George Smoot, Simon White and Alan Guth sitting next to each other in the front row.
Follow @telescoperNot having much time to write anything particularly original, I thought I’d use this blog to advertise a forthcoming centenary celebration which I hope to attend and speak at, if my recovery goes to plan. The text below is taken from the conference website for a meeting due to take place at the Lowell Observatory in Flagstaff, Arizona from September 13-15. I’m sure they won’t mind me borrowing it, as it helps promote the event. Registration is open until 10th August…
On September 17, 1912, Vesto Slipher obtained the first radial velocity of a “spiral nebula” – the Andromeda Galaxy. Using the 24-inch telescope at Lowell Observatory, he followed up with more Doppler shifts, and wrote a series of papers establishing that large velocities, usually in recession, are a general property of the spiral nebulae. Those early redshifts were recognized as remarkable by Slipher, and were critical to the discovery of what came eventually to be called the expanding Universe. Surprisingly, Slipher’s role in the story remains almost unknown to much of the astronomical community.
The nature, and especially the distance, of spiral nebulae was fiercely argued – most famously in the 1920 Shapley-Curtis debate. Hubble’s 1923 discovery of Cepheids in Andromeda, along with Henrietta Leavitt’s period-luminosity relation for Cepheids, led to a distance scale for the nebulae, enabling Lemaitre (1927) to derive a linear relation between velocity and distance (including a “Hubble constant” and, by 1931, a Primeval Atom theory).
Meanwhile, a new concept of space and time was formulated by Einstein, providing a new language in which to understand the large-scale Universe. By 1932, all the major actors had arrived on stage, and Universal expansion – the most general property of the Universe yet found – acquired a solid basis in observation and in the (relativistic) concept of space. “Space expands”… or does it? How did Lemaitre and Hubble interpret this concept? How do we interpret it? It continues to evolve today, with cosmic inflation and dark energy presenting new challenges still not fully assimilated.
This conference is in honor of Vesto Melvin Slipher and is timed to coincide with the 100th anniversary of the first measured Doppler shift in a Galaxy (then known as a Spiral-Nebula) on September 17, 1912:Slipher 1913 Lowell Obs 2, 56
We are bringing together astronomers and historians of science to explore the beginnings and trajectories of the subject, at the place where it began.
Follow @telescoperThis has been doing the rounds for a week or so, but I’ve only just found it. It’s a time-lapse video made from still photographs taken by the crew of the International Space Station. I thought I’d share it here because it’s wonderful…
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While I’m incarcerated at home I thought I might as well make myself useful by passing on an interesting news item I found on the BBC website. This relates to a paper in the latest edition of Nature that reports the discovery of what appears to be a classic “Grand Design” spiral galaxy at a redshift of 2.18. According to the standard big bang cosmology this means that the light we are seeing set out from this object over 10 billion years ago, so the object formed about 3 billion years after the big bang.
I found this image of the object – known to its friends as BX442 – and was blown away by it..
..until I saw the dreaded words “artist’s rendering”. The actual image is somewhat less impressive.
But what’s really interesting about the study reported in Nature are the questions it asks about how this object first into our understanding of spiral galaxy formation. According to the prevailing paradigm, galaxies form hierarchically by progressively merging smaller clumps into bigger ones. The general expectation is that at high redshift – corresponding to earlier stages of the formation process – galaxies are rather clumpy and disturbed; the spiral structure we see in nearby galaxies is rather flimsy and easily disturbed, so it’s quite surprising to see this one. Does BX442 live in an especially quiet environment? Have we seen few high-redshift spirals because they are rare, or because they are hard to find? Answers to these and other questions will only be found by doing systematic surveys to establish the frequency and distribution of objects like this, as well as the details of their internal kinematics.
Quite Interesting.
Follow @telescoperI’ve been trying to make myself useful over the last few days thinking about the new module I’m supposed to start teaching in October. I’m a bit daunted by it to be honest. The title is The Physics of Fields and Flows and it will be taken by students when they return to start their second year after the summer break. It’s twice the size of our usual modules, which means a lot of teaching and it’s all new for me, which means a lot of preparation.
The idea behind introducing this module was to teach a number of things together which previously had been taught in separate modules, specifically electromagnetism and vector calculus, or not at all, e.g. fluid mechanics. I’m not sure when or why classical fluid mechanics dropped out the syllabus, but I think it’s an essential part of a physics curriculum in its own right and also helps develop a physical understanding of the mathematics used to describe electric and magnetic fields. It’s one of the unhappy side-effects of modular teaching that it hides the important underlying connections between apparently disparate phenomena which are the essence of what physics is about.
Another thing I reckon we don’t do enough of these days is use lecture demonstrations. That’s harder to do these days because we tend to use pooled lecture theatres that don’t have the specialist equipment that they might have if they were dedicated to physics lectures only. Practical demonstrations are now usually given second-hand, by using video clips. That’s fine, but not as good as the real thing.
Anyway, it struck me that it would be quite easy to arrange a demonstration of the transition between laminar and turbulent flow using the simple and relatively inexpensive equipment shown in the rather beautiful image. Unfortunately, however, demonstrating this sort of thing isn’t allowed on University premises even for scientific purposes…
Follow @telescoperI thought anyone reading my rather gloomy recent posts could probably do with a laugh so I thought I’d put this up. It’s something I posted a while ago, in fact, but the video links on that have long since evaporated; a newer version appeared recently on Youtube so I thought I’d update it and re-post the piece.
This clip contains a short item I did about twelve years ago for the BBC series Space, which was presented by Sam Neill. It was subsequently screened outside the UK with an alternative title, Universe. Originally we were going to demonstrate wormholes using a snooker table, clever editing and reversed video. However, the producer, Jeremy, decided that wouldn’t look spectacular enough so instead we went to St Anton in Austria: I was flown over the Alps in a helicopter and then driven through the Arlberg tunnel in an impressively fast car. Well worth the cost to license fee payers, I’m sure, even if the three-day trip to Austria by me and a crew of six as well as the hire of the helicopter ended up as a mere three minutes of screen time…
The episode I was in, the last of 6 in the series, was called To Boldly Go. I remember suggesting to the producer that the only way to travel faster than light in the manner required was with a split infinitive drive, but they didn’t use that in the final script.
The segment I’m in starts at about 18:00 on the video. Notice how, in the helicopter sequence, I give the appearance of being completely terrified. A fine piece of acting by me, I thought. *Cough*
The item is daft, I know, and I don’t really believe any of that stuff about wormholes, but it was great fun doing it and I have to say the camera guys took some amazing footage of the mountains from the helicopter.
P.S. The next sequence, after mine, explains how the Anglo-Australian 2dF Galaxy Redshift Survey was done in order to provide a map for future generations of intergalactic space travellers. Really?
Follow @telescoperI sneaked into the department this morning to pick up some things from the office and leave some other things that I’ve finished with. I went quite early, to avoid the Saturday crowds there and back.
One of the things I found in my pigeonhole was a packet of student questionnaires about the third-year module Nuclear and Particle Physics for which I was responsible. It seems like a decade since I finished teaching it and marked the exams, but it can only be a couple of months. I was dreading reading the responses this time because I know I struggled a bit with this module, partly because it’s the first time I taught the Nuclear Physics part and partly for other reasons I won’t go into.
In fact the students were very kind and gave me quite good reviews; the only score that let me down really was that they thought the material was rather difficult. I’m not really surprised by that, because I think it is. However, as I’ve said before, I don’t think it’s a physics lecturer’s job to pretend that the subject is easy; it is a lecturer’s job to try to convince students that they can do things that are difficult. I don’t mean making things difficult just for the sake of it, but trying to get the message across that a brain is made for thinking with and figuring difficult things out can be intensely rewarding.
The main criticism that students wrote in the space provided for their own comments was that they didn’t like the fact that I used powerpoint for some lectures. Actually, I don’t like using powerpoint for lectures either, but unfortunately I had no choice on some occasions. First I had a rather large class (85 students) and one of the rooms I had to use had a very small whiteboard; I was worried about its visibility from the back and the need to keep cleaning it every five minutes. Also in that room the projector screen covers the same area as the whiteboard, so it’s a pain to keep changing between powerpoint and whiteboard. Anyway, it’s a fair criticism. I’ll try to work out a better way of doing it next year.
To be perfectly honest I don’t like whiteboards much either. Call me old-fashioned, but chalkboards are much better. Received wisdom, however, is that we have to have whiteboards, with all the ludicrous cost and environmental unfriendliness of the accompanying dry-wipe marker pens. But I digress.
Anyway, next Wednesday afternoon will see our graduation ceremony. Graduation day always reminds me of something somebody told me years ago when I attended my first one, at Queen Mary (and Westfield College, as it was then). The essence of the comment was that what you have to remember as a lecturer is that when the students do well it’s their achievement; but when they don’t it’s your fault. Life’s like that, it’s never as symmetrical as particle physics.
Many of the students who took Nuclear and Particle Physics will be graduating on Wednesday. I’m distraught that I won’t be able to go myself; this will be the first ceremony I’ve missed since I moved here five years ago. If any of the graduating Physics class from Cardiff University happens to read this, I really hope you have a great day on Wednesday. I wish I could be there to shake your hand and wish you a very fond goodbye, but sadly that’s just not possible on this occasion.
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In the Dark 