I know it’s a bit late for Hallowe’en but have you noticed the similarity between the physical manifestation of the apocalyptic Sumerian deity Gozer as seen in the film Ghostbusters (left) and the pattern of dark coronal holes recently observed by NASA in the Sun’s atmosphere (right)? I wonder if, by any chance, they might be related?
Not long ago I posted an item about the Summer Programme for Undergraduate Research (SPUR) at Maynooth University. This past summer I had two undergraduate students doing research projects with me funded under this scheme. They were both involved with making Monte Carlo simulations of galaxy clustering and using them to test various statistical analysis tools. The Department of Theoretical Physics actually had five students on three different projects, which is quite a lot for a small Department. The University as a whole had 57 SPUR students so we had almost ten percent of the total!
Well, earlier this week there was a Research Symposium at which all the summer’s research undergraduates presented posters on their work, with prizes being awarded for the best. I couldn’t attend the Symposium because of other commitments but I was delighted to find out that both my students won prizes – that’s two out of the five awarded. Here are the pictures of them being presented with their awards at the ceremony yesterday, flanked by the Vice-for Research and Innovation, Brian Donnellan and the President, Eeva Leinonen.
The awards ceremony was held in the foyer of the new TSI building yesterday afternoon, which wasn’t an ideal choice because the acoustic is very poor and lots of students were making their way to and from lectures. I didn’t hear a word of the speeches, actually. Nevertheless it was nice to see Pawel (top prize in the Science and Engineering category) and Lisa (audience choice prize winner) collect their awards. It was a pleasure to work with both of them this summer!
Incidentally, the SPUR students are paid for the projects, which last for (usually) six weeks but can be extended. I wish we could offer these projects to every student who wanted one, actually, but we just can’t afford to do that. I don’t agree with unpaid internships as these can only be taken up by students who have access to enough income to cover living expenses over the summer, so are discriminatory. We select students based on an application form and their academic performance.
JWST – nice telescope, shame about the name
I’ve blogged before about the problematic naming of the James Webb Space Telescope. Its name was changed in 2002 from the Next Generation Space Telescope to the James Webb Space Telescope after James E. Webb, a civil servant who was NASA’s chief administrator from 1961 to 1968.
It’s not uncommon for scientific space missions like this to be named after people once the proposal has moved off the drawing board and into serious planning. That happened with the European Space Agency’s Planck and Herschel to give two examples. In any case Next General Space Telescope was clearly never anything but a working title. Yet naming this important mission after a Government official always seemed a strange decision to me. Then news emerged that James Webb had enthusiastically cooperated in a McCarthyite purge of LGBT+ people working in government institutions, part of a wider moral panic referred to by historians as the Lavender Scare. There have been high-profile protests (see, e.g., here) and a petition that received over a thousand signatures, but NASA has ruled out any change of name.
The main reason NASA give is that they found no evidence that Webb himself was personally involved in discrimination or persecution. I find that very unconvincing. He was in charge, so had responsibility for what went on in his organization. If he didn’t know then why didn’t he know? Oh, and by the way, he didn’t have anything to do with infrared astronomy either…
I still think it’s a shame that this fantastic telescope should have its image so tarnished by the adoption of an inappropriate name.
Anyway, yesterday I saw that the Royal Astronomical Society has issued a statement about this issue, which I encourage you to read in full. It begins
At its meeting in July the governing council of the Royal Astronomical Society (RAS) took a decision to write to the UK Space Agency, the European Space Agency (ESA) and NASA to express its concerns about the original JWST naming process, the apparent failure to investigate James Webb’s background and the dismissal of requests to rename the telescope.
Until that investigation takes place and the results are made public, the RAS now expects authors submitting scientific papers to its journals to use the JWST acronym rather than the full name of the observatory. In this case, the previous requirement for the acronym to be spelled out at first mention will not be observed. This change will also be reflected in our communications more generally.
This does at least acknowledge the problematic nature of the name and the message it sends to LGBT+ scientists around the world and it the statement as a whole is to be welcome.
I think I’ll continue to use the name James Webb Space Telescope on this blog, though, as a reminder that the name should just be changed. Even in shorthand it’s an insult.
Regular readers of the blog – both of them – may remember that we have twice previously presented a Masterclass in Astrophysics & Cosmology in Maynooth. Well, owing to popular demand, we’ve decided to do a re-run of the event on Wednesday 16th November 2022 during this year’s Science Week. Last year’s event was a big success, with over a hundred schools joining in, with probably over a thousand young people listening and asking questions.
Like last year’s event this year’s will be a half-day virtual event via Zoom. It’s meant for school students in their 5th or 6th year of the Irish system. There might be a few of them or their teachers who see this blog so I thought I’d share the news here. You can find more information, including instructions on how to book a place, here.
Here is the flyer for the event:
I’ll be talking about cosmology early on, and John Regan will talk about black holes later on. After the coffee break one of our students will talk about why they wanted to study astrophysics. Then I’ll say something about our degree programmes for those students who might be interested in studying astrophysics and/or cosmology as part of a science course. We’ll finish with questions either about the science or the studying!
Here is a more detailed programme:
Fortunately this year I don’t need to dash away at noon to do a lecture!
A couple of articles appeared recently that I encourage people to read who are studying physics, or interested in studying physics.
The first article by Carl Wieman is from Physics Today and is entitled How to become a successful physicist. It is aimed at graduate students, though most of what it says is relevant to those at an earlier stage of their studies. Here’s an excerpt from near the beginning:
The primary characteristic of a successful physicist is being a good problem solver.
The article goes on to say some very interesting and instructive things, and is well worth reading in its entirety. There are one or two things that I don’t agree with though. One is the statement that…
…textbook problems provide all the information needed and have a single well-defined path to a solution.
That’s true of many problems at an elementary level, but problems at undergraduate or graduate level often have more than one way of finding the solution. That’s certainly true of many that I set as assignments. Indeed, sometimes the students come up with better ways of approaching them than I did! The important difference between textbook and research problems is that you know the textbook problems have a solution. Research is scarier because you don’t know at the outset that an answer can be found!
The second article, by Ethan Siegel, is called The secret to becoming an excellent physicist. Here is a quote from that, revealing the “secret”:
It’s simplicity itself: you become good at physics by solving physics problems. That’s it: that’s the secret. If you want to become competent at physics, you will solve physics problems in the area you wish to learn.
I hope you get the message. It’s not about rote-learning facts and formulae. The brain is much more than a memory device. It’s all about problem-solving. The ability to do that effectively can only be learned through practice.
I’m currently teaching two modules on Mathematical Physics and I devote most of the time in lectures for both of them to doing worked examples rather than proving theorems or presenting facts, theorems, derivations, formulae, etc to learn. I spend quite a lot of time in lectures giving students things to work out, which makes classes more interactive, but students also have tutorials built around problem-solving tasks to complement this.
If you’re interested you can see my post on How to Solve Physics Problems; there is also a video version here.
I’d add one piece of advice. If you really want to develop as a physicist, don’t just solve a lot of easy problems; challenge yourself by tackling difficult ones too. Don’t be afraid to get “stuck” or make a mistake, as those are both necessary parts of the learning process. Above all, develop the confidence in your ability to take on a problem and back yourself to solve it and don’t be deterred if the answer doesn’t come quickly!
Aa few months ago I posted a piece about the European Space Agency’s Euclid Mission which had been due to be launched in 2023 on a Soyuz ST 2-1b rocket. That no longer being possible because of Russian’s invasion of Ukraine, it seemed there would be a lengthy delay in the launch of Euclid, with late 2024 seeming the earliest feasible date for launch on the obvious alternative, the new Ariane 6.
I ended that piece with this:
It seems to me that the best hope for a resolution of this problem would be for ESA to permit the launch of Euclid using something other than Ariane 6, which means using a vehicle supplied by an independent commercial operator. I sincerely hope ESA is able to come up with an imaginative solution to this very serious problem.
In the Dark, 17th June
Well I’ve just read official confirmation that a few hours ago ESA Council has approved the proposal to launch Euclid on a Falcon 9 rocket operated by SpaceX. If all goes well -specifically if the Euclid Consortium member states agree with this move – it might be possible to launch Euclid by the end of 2023. Although I don’t have any firm information about what date is being proposed I believe it could be as soon as July 2023.
Setting aside any personal opinions about Elon Musk, the Falcon 9 has proved to be very reliable, with the latest version having 110 out of 110 successful launches. Euclid will not be in an Earth orbit, like most of the satellites so far launched by SpaceX, but has to be delivered to the 2nd Lagrange Point, L2. That should not pose to much of a difficulty, however.
It seems a lot longer than four years ago that I drew the attention of readers of this blog to the science case for the Simons Observatory, the next big thing in ground-based studies of the cosmic microwave background.
Obviously a couple of years of pandemic have intervened, amongst other things, but I was delighted to read yesterday that the UK has invested £18M in the Simons Observatory, which will enable further development of the facility at Cerro Toco, high above the Atacama Desert in Chile.
The project was already a large international collaboration led from the USA, but the new funds from UKRI mean that six UK institutions will now join. These are (in alphabetical order): Cambridge; Cardiff; Imperial College London; Manchester; Oxford; and Sussex. Although I’m not involved in this project myself I know many people at these institutions (two of which I have worked at) and elsewhere who will be absolutely thrilled to be able to participate in this exciting project. Congratulations to them!
It would have been great if Ireland had been able to get involved in the Simons Observatory, but sadly fundamental science of this type is not a priority for the powers that be in Irish science funding. This is unfortunate because I think membership of international consortia like this would enable a small country to punch above its weight in science. Still, at least the UK PI, Prof. Michael Brown (Manchester), is an Irishman…
Sorry to be so late advertising this but it’s been a busy week. This year’s Royal Astronomical Society Gerald Whitrow lecture will be given this afternoon by Prof. Pedro Ferreira of Oxford University, as a hybrid event. You have until 3pm to register. Among many other things, Pedro is a member of the Editorial Board of the Open Journal of Astrophysics…
The abstract of the lecture is:
Observations of the large scale structure of the Universe have allowed us to validate a powerful mathematical model of the Universe. We can now measure with remarkable precision, a number of properties such as its geometry, its matter content and the morphology of the initial conditions. This model is firmly rooted in physics that we know yet also reliant on speculative assumptions: inflation, dark matter and dark energy. As our understanding of the cosmological model has developed, and with ever improving data, we have been confronted with anomalies and inconsistencies. There is hope that, with new observations, more powerful simulations and the new developments in machine learning and data science, we will be able to fully resolve any inconsistencies. But there is a real risk that, if we don’t start to think differently, we will never completely understand our mathematical model. Ultimately we may never know how our Universe really works.
It should be an interesting talk and there’s still a bit of time to register. Alternatively you can wait until the recording appears on YouTube. I’ll add a link here when it does.
I’ve just finished reading an interesting paper by Secrest et al. which has attracted some attention recently. It’s published in the Astrophysical Journal Letters but is also available on the arXiv here. I blogged about earlier work by some of these authors here.
The abstract of the current paper is:
We present the first joint analysis of catalogs of radio galaxies and quasars to determine if their sky distribution is consistent with the standard ΛCDM model of cosmology. This model is based on the cosmological principle, which asserts that the universe is statistically isotropic and homogeneous on large scales, so the observed dipole anisotropy in the cosmic microwave background (CMB) must be attributed to our local peculiar motion. We test the null hypothesis that there is a dipole anisotropy in the sky distribution of radio galaxies and quasars consistent with the motion inferred from the CMB, as is expected for cosmologically distant sources. Our two samples, constructed respectively from the NRAO VLA Sky Survey and the Wide-field Infrared Survey Explorer, are systematically independent and have no shared objects. Using a completely general statistic that accounts for correlation between the found dipole amplitude and its directional offset from the CMB dipole, the null hypothesis is independently rejected by the radio galaxy and quasar samples with p-value of 8.9×10−3 and 1.2×10−5, respectively, corresponding to 2.6σ and 4.4σ significance. The joint significance, using sample size-weighted Z-scores, is 5.1σ. We show that the radio galaxy and quasar dipoles are consistent with each other and find no evidence for any frequency dependence of the amplitude. The consistency of the two dipoles improves if we boost to the CMB frame assuming its dipole to be fully kinematic, suggesting that cosmologically distant radio galaxies and quasars may have an intrinsic anisotropy in this frame.
I can summarize the paper in the form of this well-worn meme:
My main reaction to the paper – apart from finding it interesting – is that if I were doing this I wouldn’t take the frequentist approach used by the authors as this doesn’t address the real question of whether the data prefer some alternative model over the standard cosmological model.
As was the case with a Nature piece I blogged about some time ago, this article focuses on the p-value, a frequentist concept that corresponds to the probability of obtaining a value at least as large as that obtained for a test statistic under a particular null hypothesis. To give an example, the null hypothesis might be that two variates are uncorrelated; the test statistic might be the sample correlation coefficient r obtained from a set of bivariate data. If the data were uncorrelated then r would have a known probability distribution, and if the value measured from the sample were such that its numerical value would be exceeded with a probability of 0.05 then the p-value (or significance level) is 0.05. This is usually called a ‘2σ’ result because for Gaussian statistics a variable has a probability of 95% of lying within 2σ of the mean value.
Anyway, whatever the null hypothesis happens to be, you can see that the way a frequentist would proceed would be to calculate what the distribution of measurements would be if it were true. If the actual measurement is deemed to be unlikely (say that it is so high that only 1% of measurements would turn out that large under the null hypothesis) then you reject the null, in this case with a “level of significance” of 1%. If you don’t reject it then you tacitly accept it unless and until another experiment does persuade you to shift your allegiance.
But the p-value merely specifies the probability that you would reject the null-hypothesis if it were correct. This is what you would call making a Type I error. It says nothing at all about the probability that the null hypothesis is actually a correct description of the data. To make that sort of statement you would need to specify an alternative distribution, calculate the distribution based on it, and hence determine the statistical power of the test, i.e. the probability that you would actually reject the null hypothesis when it is incorrect. To fail to reject the null hypothesis when it’s actually incorrect is to make a Type II error.
If all this stuff about p-values, significance, power and Type I and Type II errors seems a bit bizarre, I think that’s because it is. In fact I feel so strongly about this that if I had my way I’d ban p-values altogether…
This is not an objection to the value of the p-value chosen, and whether this is 0.005 rather than 0.05 or, , a 5σ standard (which translates to about 0.000001! While it is true that this would throw out a lot of flaky ‘two-sigma’ results, it doesn’t alter the basic problem which is that the frequentist approach to hypothesis testing is intrinsically confusing compared to the logically clearer Bayesian approach. In particular, most of the time the p-value is an answer to a question which is quite different from that which a scientist would actually want to ask, which is what the data have to say about the probability of a specific hypothesis being true or sometimes whether the data imply one hypothesis more strongly than another. I’ve banged on about Bayesian methods quite enough on this blog so I won’t repeat the arguments here, except that such approaches focus on the probability of a hypothesis being right given the data, rather than on properties that the data might have given the hypothesis.
Not that it’s always easy to implement the (better) Bayesian approach. It’s especially difficult when the data are affected by complicated noise statistics and selection effects, and/or when it is difficult to formulate a hypothesis test rigorously because one does not have a clear alternative hypothesis in mind. That’s probably why many scientists prefer to accept the limitations of the frequentist approach than tackle the admittedly very challenging problems of going Bayesian.
But having indulged in that methodological rant, I certainly have an open mind about departures from isotropy on large scales. The correct scientific approach is now to reanalyze the data used in this paper to see if the result presented stands up, which it very well might.
In the Dark 