As readers of this blog who appreciate the idea of putting science into the daily routine for a balanced diet, of mixing in sketches here and there, of good humour and a wondering eye on the world…. you’ll agree with me that we need to raise our voices and call out to NPR to Save “Krulwich Wonders”. According to Robert Krulwich, they are planning to cancel his blog as part of cost-cutting… this would be a big blow for the (always in danger) mission to improve the public understanding of science. Many suggestions are in the comments to that post I liked above, so feel free to read them and follow the ones that make sense to you! [Update: I've put a hashtag #savewonderNPR into the accompanying tweet of this post, so feel free to use that in your own raising awareness efforts on this...]
Act fast to let your voice be heard. The axe is on its way down!*
*I learned this from the blog Nanoscale Views.
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There has been quite a bit of discussion of the realisation that the exciting announcement made by the BICEP2 experiment back in March (see my post here) was based on erroneous analysis. (In brief, various people began to realise that most, if not all, of what they observed could be explained in terms of something more mundane than quantum spacetime fluctuations in the ultra-early universe – the subtle effects of galactic dust. A recent announcement by another experiment, the Planck team, have quantified that a lot.)
While there has been a bit of press coverage of the more sober realisations (see a nice June post on NPR’s blog here), it is (as with previous such cases) nowhere near as high profile as the initial media blitz of March, for better or worse. I think that “worse” might be the case here, since it is important to communicate to the public (in a healthy way) that science is an ongoing process of discovery, verification, and checking and re-checking by various independent teams and individuals. It is a collective effort, with many voices and the decentralised ever-sceptical scientific process itself, however long it takes, ultimately building and broadening the knowledge base. This self-checking by the community, this reliance on independent confirmation of [...] Click to continue reading this post
So I discovered a terrifying (but also kind of fascinating and beautiful at the same time) new element to the garden this morning. We’re having a heat wave here, and so this morning before leaving for work I thought I’d give the tomato plants a spot of moisture. I passed one of the tomato clusters and noticed that one of the (still green) tomatoes had a large bite taken out of it. I assumed it was an experimental bite from a squirrel (my nemesis – or one of them), and muttered dark things under my breath and then prepared to move away the strange coiled leaf that seemed to be on top of it. Then I noticed.
It wasn’t a leaf.
It was a HUGE caterpillar! Enormous! Giant and green with spots and even a red horn at one end! There’s a moment when you’re unexpectedly close to a creature like that where your skin crawls for a bit. Well, mine did for a while [...] Click to continue reading this post
You may recall that back in June I had a chat with Hal Rudnick over at Screen Junkies about science and time travel in various movies (including the recent “X-Men: Days of Future Past”). It was a lot of fun, and people seemed to like it a lot. Well, some good news: On Tuesday we recorded (along with my Biophysicist colleague Moh El-Naggar) another chat for Screen Junkies, this time talking a bit about the fun movie “Guardians of the Galaxy”! Again, a lot of fun was had… I wish you could hear all of the science (and more) that we went into, but rest assured that they* did a great job of capturing some of it in this eight-minute episode. Have a look. (Embed below the more-click):
[...] Click to continue reading this post
So while at a hotel somewhere down South for a few days (pen and watercolour pencil sketch on the right), I finally found time to sit and read Graham Farmelo’s book “The Strangest Man”, a biography of Dirac. (It has a longer subtitle as well, but the book is way over in the next room far from my cosy spot…) You may know from reading here (or maybe even have guessed) that if I were to list a few of my favourite 20th century physicists, in terms of the work they did and their approach and temperament, Dirac would be a strong contender for being at the top of the list. I am not a fan of the loudmouth and limelight-seeking school of doing physics that seems all so popular, and I much prefer the approach of quietly chipping away at interesting (not always fashionable) problems to see what might turn up, guided by a mixture of physical intuition, aesthetics, and a bit of pattern-spotting. It works, as Dirac showed time and again.
I’ve read a lot about Dirac over the years, and was, especially in view of the title of the book, a little wary of reading the book when I got it four years ago, as I am not a fan of going for the “weren’t they weird?” approach to biographies of scientists since they serve too [...] Click to continue reading this post
Given that you read here at this blog, you may well like to keep your boundaries between art and science nicely blurred, in which case you might like to learn more about the coral reef forests made of crochet spearheaded by Margaret and Christine Wertheim. The pieces mix crochet (a hand-craft I know and love well from my childhood – I got to explore my love for symmetry, patterns, and problem-solving by making doilies) with mathematics – hyperbolic geometry in particular – as well as biology (mimicking and celebrating the forms of corals – and drawing attention to their destruction in the wild). You can read much more about the projects here. I’ve mentioned the work here before on the blog, but the other day I went along to see a new set [...] Click to continue reading this post
Back in LA, I had an amusing day the other day going from this* in the TV studio…
involving a laser and liquid nitrogen (so, around -320 F, if you must use those units), to this in the kitchen:
involving butter, flour, water and shortening… (and once in the oven, around +350 F) which ultimately resulted in this: [...] Click to continue reading this post
In case you missed it, Maryam Mirzakhani has been awarded the Fields Medal! This is regarded as the most prestigious prize in mathematics. Here’s a Guardian article covering it at a general level, and here is the page on all the award winners, with more detail on each, at the International Mathematical Union website. The reason this is a big deal (and why it is newsworthy) is because it is the first time the prize has been awarded to a woman. In a world where, despite the number of excellent women mathematicians out there, there is still a perception problem in the general populace about who (or more to the point, what gender) is associated with achievement in mathematics, it is important to note and celebrate such landmarks.
I also note that one of the other 2014 awardees, Artur Avila, is from Brazil! While not covered as much in the press as far as I can see, this is another big [...] Click to continue reading this post
So tonight (meaning the wee hours of Monday morning and the next few mornings, for optimum viewing – more civilised hours might work too, of course) the Perseid meteor shower will be on view! Have a look at this site (picked at random; there are many more) for more about how to view the meteors, in case you’re not sure. Well, here’s an interesting thing. The moon will be at its brightest as well, so that’ll mean that the viewing conditions for meteors will not be ideal, unfortunately. And it really will be extra bright (well, slightly, to be honest) because tonight’s full moon is during the moon’s closest approach to [...] Click to continue reading this post
I thought I’d mentioned this already, but I could not find anything after a search on the blog so somehow I think I must have forgotten to. It is a cute thing about a certain favourite solution (or class of solutions) of Einstein’s equations that I’ve talked about here before. I’m talking about the Taub-NUT solution (and its cousin, Taub-Bolt). Taub-NUT is sort of interesting for lots of reasons. Many, in fact. One of them concerns it having both mass and another parameter called “nut charge”, . There are several ways to think about what nut charge is, but one curious way is that is is sort of a “magnetic” counterpart to the ordinary mass, which can be thought of as an “electric” quantity.
The language is based on analogy with electromagnetism, where, in the usual [...] Click to continue reading this post
Hello from the Aspen Center for Physics. One of the things I wanted to point out to you last month was the 74 questions that Andy Strominger put on the slides of his talk in the last session of the Strings 2014 conference (which, you may recall from earlier posts, I attended). This was one of the “Vision Talks” that ended the sessions, where a number of speakers gave some overview thoughts about work in the field at large.
Andy focused mostly on progress in quantum gravity matters in string theory, and was quite upbeat. He declines (wisely) to make predictions about where the field might be going, instead pointing out (not for the first time) that if you look at the things we’ve made progress on in the last N years, most (if not all) of those things would not have been on anyone’s list of predictions N years ago. (He gave a specific value for N, I just can’t recall what it is, but it does not matter.)
He sent an email to everyone who was either speaking, organising, moderating a session or similarly involved in the conference, asking them to send, off the [...] Click to continue reading this post
I was sent an interesting link a while ago* that I thought I would share with you. It is a really good discussion about Dark Energy – what do we think it is, why we think it exists, why some think it does not, and how to move forward with the discussion of what is, after all apparently *most* of our universe. It is a panel discussion that was hosted by the Institute for Arts and Ideas (which I *love* the idea of!). The discussion is described on the site as follows:
Dark energy is supposed to make up two-thirds of the universe. But troublingly CERN has yet to find any evidence. Have we got our story of the universe wrong – might dark energy be the aether of our time? Do we need a new account of the universe, or is it too soon for such radical solutions?
The BBC’s Sue Nelson asks Templeton Prize winning cosmologist George Ellis, Cambridge physicist David Tong and mathematician Peter Cameron to seek the invisible.
Ok, the “troublingly CERN has yet to find any evidence” part puzzles me a bit, since nobody’s really expecting CERN to find any evidence of it, in any large scale experiments that I’m aware of (please correct me if I am wrong)… Is the writer of the abstract confusing Dark Energy and Dark Matter? Even then I think it is an odd phrase to lead with, especially if you don’t mention the huge amount of evidence from astronomy in the same footing… but I imagine the abstract was maybe not written by a physicist?
Nevertheless, I strongly recommend it as a thought-provoking discussion, and you can find it embedded below. Do also check out their many other interesting [...] Click to continue reading this post
It is the 4th of July, and I hope you who are celebrating it have a good time today!
I can’t really let the day pass without sharing with you the episode of Fail Lab in which we examine fireworks and pyrotechnics with an appropriate cautionary note, and a dash of humour. Enjoy it again if you’ve seen it before, and don’t forget to check out all twelve episodes. You can read my discussion of the whole series (excellently made by Patrick Scott) starting here, and there’s more here. Click below for the episode: [...] Click to continue reading this post
As you may know from three previous recent posts on research (here, here, and here), I’ve been thinking and calculating a lot in the area of dynamical cosmological constant – concerning mostly (but not entirely) thermodynamics and quantum gravity. Specifically, the cosmological constant becomes the pressure variable in the thermodynamics. I think it is important, and will teach us something about things like gauge/gravity duality, string theory, black holes, and perhaps even cosmology, but I am not sure what yet. I’ve made some suggestions in recent papers, and computed some interesting things along the way.
Anyway, the larger community has not been following this story much, since: (1) It means a break with some powerful and still very fruitful frameworks where the cosmological constant being fixed is a given – like AdS/CFT – and it is not clear what that means yet, so the motivation is not super-strong; and (2) Let’s be honest, there’s no superstar working on it, so it is not going to get anyone any points. So I’ve been trying to shout about it in my little way from the periphery, as I think it might be useful, and since several people have been doing really good and interesting work on this issue for many years and it is worth more people seeing what they’ve been up to.
So imagine my pleasant surprise when I looked on the listing of new papers on the arXiv for today and saw three (!) papers on the subject, moving things forward in various ways. (They all seem to have noticed some of what I’ve [...] Click to continue reading this post
The conference is really rather good, with a varied program involving topics and speakers from all over the map. This includes the parallel sessions we had on Wednesday, which were held down at the Institute. Those were a lot of fun, because of the dodging back and forth between different auditoria at the IAS to get to talks of interest. I was chairing one of the sessions, and so did not get to dodge about in the first 90 minutes, and had to miss some interesting talks, but did a little talk-surfing in the second 90 after the break.
It had been many years ago now since I began to talk about there being a need for parallel sessions at strings conferences. Some people would object to them, saying that it would somehow be damaging to the field’s connected nature, where everyone is following many strands and topics in the field. To me that concern was always balanced by the problem of only having a small cluster of people and ideas represented each year due to the constraints of only having five days to present the activity of such a diverse population of researchers in the field. The main objection to having parallel sessions were, to my mind, based on a view of the field left over from when the field was smaller in terms of both people and thriving ideas. I think the conference organizers this year found a way of combining the two models rather well, with the single afternoon of parallel sessions, along with well chosen sets of half hour talks for the main sessions where we all sit together, roughly grouped by themes. There were three one hour big marquee plenary/summary talks. Theses are really useful. If I were to make a change, I’d perhaps have four or five of those, putting the two half hour talks that were displaced into the parallel section.
There is a two hour session of “Vision Talks” this afternoon. Should be interesting to hear what is said. We will perhaps get some good discussion going about where various ideas may be headed. I hope there is a lot of audience participation.
Poster sessions and the “gong show” were also great things to have as part of [...] Click to continue reading this post
Today is day one of Strings 2014, this year’s version of the official annual conference about the latest research in string theory. There’s a feeling that there is a buzz of excitement in the air, in part because (I’m guessing): (1) Well, it is the annual conference, you’re going to find out more about what’s been going on in the various corners of the field, and (2) everywhere you look there walks a giant of the field, and (3) more generally, people just like you who “get you”, and whose papers you’ve read that you’ve spent a good portion of your life thinking about, so it would be odd if you were not excited, and (4) it is in Princeton, which is sort of equal to Mount Olympus in our field, where a lot of the giants live, if you’ll permit me to mix metaphors a bit, and (5) apparently this is the largest Strings meeting since Paris in 2004. (I’ve heard that it is maybe 600 people registered, making it the biggest Strings ever?… Not sure.)
I could go on guessing about the buzz felt by others, but instead I’ll mention [...] Click to continue reading this post
Longest day of the year? It sure felt like it. I spent about 6 hours of it standing high above the city in the sun talking about physics and astronomy to camera… Super tiring.
It is for a new show I’ll say more about later.
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Well, I sort of disappeared there for about a week. I got lost in some really interesting physics and had a lot of fun doing it.
I kept walking away, and it kept bringing me back. There’s that fun groove one can get into that other theorists will recognise: You hit an interesting vein where you can calculate interesting results in a particular model, and you just can’t help yourself computing more and more [...] Click to continue reading this post
As you know from my writings and sketches, I like to carry a notebook. People often ask me what types I use, or assume that I use the (increasingly fashionable) Moleskine books. I like Moleskine books (the little 3inx5in ones for example), and have used them a lot in the past, but actually I prefer the books by HandBook Journal Co., (made by Global Art Materials). The surface of the paper is more flexible, in my opinion. It has a little more tooth than standard Moleskine, which makes mark-making with pencil much surer, and it also takes wetting better, so you can work with a little wetness as well, such as lots of ink, or watercolour (paint- or pencil-based). That allows for crisp drawings like the one on the right (click for larger view – more about these sketches here), right alongside physics research musings and computations in pen and ink line on the pages shown below on the left (those notes pertain to the paper I discussed here.)
I tend to carry one of the 8.25inx5.5in landscape ones (although I love the 5.5in square ones too). (See more chat about them here.) They allow a good [...] Click to continue reading this post
On Tuesday I hung out with some of the Screen Junkies folks who you may know from the hilarious “Honest Movie Trailers” web series (seriously, if you’ve not seen any of them, please go right now and have a look). We had a fun chat about time travel in movies, and presenter Hal Rudnick and I bonded over various movies old and new. The final version of the show is up on YouTube (embed below), and I’m bummed that I did not get to meet the other guest, Christina Heinlein (JPL), who seems fun – and is a descendant of, yes, that Heinlein. I love the idea that she works at JPL, helping make possible the space exploration that Robert Heinlein helped inspire us all about in his writing. Anyway, enjoy the short piece (I wish you could see a bunch of the other material too… we really had a great chat about the ins and outs of time travel, but a lot of it inevitably ended up not making the cut…)
I could not resist talking about my view of this (perhaps growing) trend of using time travel as a means of resetting movie franchises (see Star Trek, X-Men…). It’s a great way of repairing writing and other filmmaking wrong turns. Feel free to imagine your own version of this – Star Wars anyone? Another pass at [...] Click to continue reading this post
So it happened again. I got musing to myself about something and decided to do a quick computation to check it out, and it took me down an interesting rabbit hole, which resulted in me writing a nice little paper at the end of last week that appeared today on the arxiv. I think the physics is really really nice. Let me tell you a bit about it. It is in the same area of ideas that I mentioned last time, concerning that paper I wrote last month. So let me pick up the story there, since I did not really touch on the core of the story. [Note: for non-experts, the following will get somewhat technical and full of terms and ideas that I will not explain. Sorry.]
One of the things that might have struck you (if you’re an expert in the area) from my proposal to make heat engines out of black holes that do real mechanical work like the engines you read about in physics textbooks is that there ought to be no actual mechanical work since there’s no pistons – no pistons changing volumes and so forth. That is (or rather, was) a missing ingredient in the standard thermodynamics of black holes in quantum gravity. Well, that all changed a short few years ago with the work of a number of authors, particularly with the clear suggestion of David Kastor, Sourya Ray, and Jennie Traschen, and work by Brian Dolan, with a fair bit of followup investigations by various other authors including some I’ll mention below. (Update: Two reviews, with different foci, can be found in here and here.) The general idea is that if you allow the cosmological constant to be a thermodynamical variable as well (and there is a long history of authors considering this in various contexts), where it naturally acts like a pressure , (G is Newton’s constant, and I’m setting various other constants to unity in the usual way) then you naturally include a conjugate to that variable that should be the pressure.
For a simple static black hole like Schwarzschild, the volume turns out to the the naive volume you get by taking the radius of the black hole and forming [...] Click to continue reading this post
….Let’s hope it is not equipped with a low-flow shower head though. If you get a chance this evening, find a wide area of sky away from as many lights as you can (it does not have to be perfectly dark, but the darker the better). There is a new meteor shower, the Camelopardalids…. It is new because the comet debris responsible (we’re flying through debris left over from its tail) has not intersected with our orbit before, but things have been changing a bit (apparently due to Jupiter’s gravitational pull) and as a result we’ll go right through it for the first time (as far as records show). It is expected that there’s a good chance that it will be a high event shower, and it has also been said – I forgot where I read this – that the [...] Click to continue reading this post
I think the people at LA Metro were trying to go for all of the visual science tropes in one cliché-filled glance! I’m a big fan of LA Metro, as you know from several posts about it here, so don’t misunderstand my poking fun at their ad I spotted on a bus stop bench. I think it is to do with helpful apps for your phone – presumably they help you use the system more easily, because of…science? More generally, I’d love to believe that people will take the train more because scientists are involved in designing the logistics, but there’s so much evidence against this on both counts, like having the Blue line and the Expo line – that share the same main platform – both boast BLUE as their colours. But put that all aside for now, and let’s simply count off all the sure-fire imagery that will [...] Click to continue reading this post
Well, it is that time of year. The Jacarandas peaking is one of the many LA markers of the seasons for me. It means that classes will soon be over (in fact they are now) and I’ll be saying goodbye to a group of students, either because a class is over, or because students I’ve taught in earlier classes are graduating and leaving USC. Either way, it is always a time of mixed feelings, and a sense of being in transition in a number of ways. The Spring is already beginning to feel like it is rolling into Summer, and I’m clearing my desk of one set of things and making way for other things.
(Oh, and of course, the other thing that happens this year is that I seem to end up doing a post like this at around this time, right down to within a few days. It usually involves a picture of a Jacaranda tree. See here and look at the list of related posts below.)
I had an extraordinarily good group of students in my Spring class this year. As you may recall it was an undergraduate General Relativity class (see earlier posts on this by searching on that topic). We ended up having a lot of fun with the topic itself, and things were extra good because the students were very [...] Click to continue reading this post
I learned* that over on the Huffington Post, Christian Ott (Caltech) wrote a piece describing research on modelling stellar explosions using supercomputers. When a star goes supernova, what exactly happens? Capturing the physics that goes on is a very difficult problem to do, and in the article he explains some of the difficulties, and some of the recent progress.
There’s a slide show showing some of the [...] Click to continue reading this post
This diagram is the cycle for another heat engine (using a black hole as the working substance) that I studied in the recent paper. It is a path made of two constant pressure legs (isobars) and two constant volume legs (isochores) that happen (due to the properties of static black holes) to also be adiabats. See the post.
It got included in the paper as another example where one could compactly write down something useful about the efficiency, since, as it turns out, you can write closed form expressions [...] Click to continue reading this post
This is a good one from the Onion. (I’ve not looked in on them for a while, so this was a funny thing to return to see…*) The title says it all: “Top Theoretical Physicists, R&B Singers Meet To Debate Meaning Of Forever”. Extract:
[...] at the four-day symposium, where they grappled with extant questions regarding the concept of forever that remained unresolved, such as whether forever is better conceived as an infinite, four-dimensional expanse of space-time or, rather, what one second feels like when you’re away from your girl.
“For many years, the R&B community has posited the classic notion that forever is presumed to go on and on like our love,” said Edward Witten, a string theorist at the Institute for Advanced Study, who acknowledged that while time appears to extend unendingly, it is paradoxically composed of discrete moments such as a tender embrace or a single perfect kiss. “This assertion then raises a problem of even greater [...]
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On Monday 28th April at 8 PM Eastern time (5 PM Pacific) I’ll take part in a live radio interview that you might want to listen to, on a show called Alpha Centauri and Beyond. I guess I’m in the “Beyond” bit? I don’t really know anything about the show except that they like to bring people on to discuss ideas, and when I get a call to come and help sprinkle a bit of science, you know I’m likely to say yes if I can spare the time.
You can see a link to the details here, and you can listen online. As you can see it is advertised as being about me explaining string theory. Well of course that billing is nothing to do with me – I can’t hope to explain any complicated subject like that in the time available – but if asked I will do my best to try and motivate some of the ideas behind the subject. I hope it will be a fun interview and that [...] Click to continue reading this post
Yes, you heard me right. Holographic Heat Engines. I was thinking recently about black holes in universes with a cosmological constant and their thermodynamics. I had an idea, it led to another, then another, then some calculations, and then a couple of days of writing, calculating, and thinking… then a day to cool off and think about other things. Then I came back to it, decided it was still exciting as an idea and so tidied it all up as a paper, made some diagrams, tidied some more, and voila! A paper submitted to the arxiv.
I’m sort of pleased with all of it since it allowed me to combine a subject I think is really fun (although often so bleakly dull when presented at undergraduate level) – heat engines – with contemporary research ideas in quantum gravity and high energy physics. So I get to draw some of the cycles in the p-V plane (graph of pressure vs volume) representing the inner workings of engines of particular designs (just like you might have seen long ago in a physics class yourself) and compute their efficiency for doing mechanical work in exchange for some heat you supply. It is fundamental that you can’t do that with 100% efficiency otherwise you’d violate the second law of thermodynamics – that’s why all engines have to have some exhaust in the form of heat, giving an efficiency represented by a quantity that is less than one, where one is 100% efficient. The diagram on the left illustrates the key pieces all engines must have, no matter what working substance you’re using. The details of the design of the engine are what kind of cycle you taking it through and what the properties (“equation of state”) your working substance has. In the case of a car, for example, the working substance is cleverly mixed up with the source of heat – the air/gasoline mix forms a “working substance” that gets expanded and compressed in various ways (in the green bit of the diagram), but the fact that it also burns releasing heat means it is also the source of the heat that comes into the engine (the flow from the red bit) to be (in part) turned to work, and the remainder flowing out to the blue (exhaust). Very clever.
The cool thing here is that I’m using black holes as the working substance for [...] Click to continue reading this post
Did you catch the eclipse last Monday? It was wonderful. Here’s a little snap I took of the progress (taken with an iPad camera precariously through the lens of a telescope, pointing out of a bedroom window, so not the best arrangement). One of the striking things about looking at the progress of it is just how extra three-dimensional the moon seems as the earth’s shadow slowly covers it. It really makes one’s whole mind and body latch on to the three dimensional reality of the sky – you really feel it, as opposed to just knowing it in your head. That’s sort of hard to explain – and you’re not going to see it in any photo anyone can show – so I imagine you are not really sure what I’m getting at if [...] Click to continue reading this post