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 results of simulations that have been done of the fully three-dimensional problem, and a little movie that puts it all together.
*Thanks Crystal D.!
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
As a contrast to yesterday’s quick caricature effort, I went back to one of the pictures in the magazine and did a more careful pencil sketch. Very different kind of exercise and technique needed to coax out the things I wanted to bring forward. It is a scan of pencils, so beware that it is not as representative of what’s on the page in some ways. To add to that I really should do a lot more finish work on this one (rendering of shadows on 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 [...]
Lovely bit of sitting in the sun for a short while after breakfast this morning relaxing by doing some quick freehand sketches from pictures in a magazine. I was experimenting with a pen I love but don’t use much at all – One of those nice inky brush pens by Pentel. Gives some interesting lines that take some getting used to since it is quite a different mark-making tool than the pens I Click to continue reading this post
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 we will explore a number of interesting topics, and not just talk all the time about string theory, since that could be rather dull, and definitely a missed opportunity… There is so much more to talk about!
Tune in and listen to find out!
See you then.
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
Eventually, although a bit over-priced in the Hollywood farmer’s market, I do fall for these at least once in the season. As someone whose job and pastimes involve seeing patterns everywhere, how can I not love the romanesco? It’s a fractal! There are structures that repeat themselves on different scales again and again, which is the root of the term “self-similar”. Fractals are wonderful structures in mathematics (that have self-similarity) that I urge you to find out more about if you don’t already know (just google and follow your nose). And Click to continue reading this post
Spotted in the hills while out walking. Three chairs left out to be taken, making for an enigmatic gathering at the end of a warm Los Angeles Spring day…
I love this city.
There is a total eclipse of the moon tonight! It is also at not too inconvenient a time (relatively speaking) if you’re on the West Coast. The eclipse begins at 10:58pm (Pacific) and gets to totality by 12:46am. This is good timing for me since I’d been meaning to set up the telescope and look at the moon recently anyway, and a full moon can be rather bright. Now there’ll be a natural filter in the way, indirectly – the earth!
There’s a special event up at the Griffith Observatory if you are interested in making a party out of it. It starts at 7:00pm and you can see more about the Click to continue reading this post
As you know I am a big fan of sketching, and tire easily of the remark people make that they “can’t draw” – an almost meaningless thing society trains most people to think and say, with the result that they miss out on a most wonderful part of life. Sketching is a wonderful way of slowing down and really looking at the world around you and recording your impressions. If you can write you certainly can draw. It is a learned skill, and the most important part of it is learning to look*. But anyway, I was pleased to see this nice way of getting people of all ages involved in sketching for fun at the book festival! So I reached in and grabbed a photo for you.
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It is nice to see the variety of authors at a book fair event like this one, and it’s great to see people’s enthusiasm about meeting people who’ve written works they’ve spent a lot of time with. The long lines for signings are remarkable! As you might guess, I’m very much a supporter of the unsung authors doing good work in their own small way, not anywhere near the spotlight. An interesting booth caught my notice as I was wandering… The word “science” caught my eye. Seems that a mother and daughter team wrote a science book to engage children to become involved in science… Hurrah! So Jalen Langie (the daughter, amusingly wearing a lab coat) gets to be Click to continue reading this post
I looked for D-Branes, by Clifford V. Johnson… But somehow must have missed it…
I’m sitting on the bus, on my way to the LA Times Festival of Books. I’ve opened my notebook to maybe sketch a face or two, but then I spot an algebraic error on a page from a few days ago, so I set about correcting it….(you know, either for those historians who will argue about my intentions while poring over these once-lost manuscripts…. Or more likely for me in a few weeks, likely to get confused by my own blunder-in-haste with a kindergarten level variation.)
A bearded fellow had boarded the bus and sat next to me while I was doing this. He eventually glances my way, then away, then he does a double take. I’ve been watching him out of the corner of my eye. He starts to speak to me.
Calc or Trig?
Calc or trig?
What are you studying?
I’m not…studying. It is my research.
Silence from him for a few beats, then:
Charged black holes.
I should say at this point that I get this a lot. No matter who I meet out there in the random world, or what they see me writing, the assumption is always that I am taking a class in high school mathematics. Why is that? People, at least guess for some of the time that I might be at least teaching it, even if you can’t imagine people doing research in this area. The grey hairs in my beard are a guide to your assumptions.
Another gripe: if you see someone writing words, and want to engage them in conversation about it, you don’t assume they are practicing the basic structures… Imagine the analogous exchange: Are you practicing joined-up writing madam, or spelling? Neither, I’m writing poetry.
Anyway, back to the conversation. So, as you recall, I said Charged black Click to continue reading this post
We had a midterm in the undergraduate General Relativity class this week. Midterm II. We’d just come off a batch of lectures on black holes (focussing on Schwarzschild and Kerr), and so it seemed very natural to focus on that as the topic. Schwarzschild is the most basic (vanilla) black hole and Kerr is the case of having rotation for a bit of extra flavour. They are both hugely important in real physics – the former for the basic phenomena and then the latter since most objects out there in the astrophysical realm are actually going to be rotating to some degree (and after gravitational collapse, probably a high degree). So I focussed on those in class.
For the midterm therefore, I got the opportunity to have them discover properties of the (less astrophysically important perhaps) charged black hole – the Reissner-Nordstrøm solution*:
…and do a few computations with it analogous to what they did for the other cases in class and in homework. I hope they had fun (like discovering that for a Click to continue reading this post
It was the departmental retreat this weekend, and we all went off on a boat to an island! On the voyage back I decided to practice a little sketching, and found myself surrounded by good subjects, because a lot of people were sitting still during the crossing (it was a small boat). Since the boat was rocking Click to continue reading this post
(From a walk near my hideout a couple of weeks ago…)
By the way, for those of you in the area, don’t forget that the LA Times Festival of Books comes to the USC campus again this month. It is next week – the 12th and 13th April. The book prizes ceremony is the night before, as usual. on the 11th, and as usual there is an interesting selection of finalists in various categories that you can see online here, for example.
(Happily, there is no clash with a CicLAvia this year! – You might remember the craziness last year – The next Ciclavia is this coming Sunday, the 6th, and it is along Wilshire again. Sadly, I will not be able to attend since I must be away on a trip and do not return until the afternoon on Sunday, leaving little time to get on my bike and get down there. Do head there and enjoy it… the Wilshire route is particularly nice.)
The main Book Festival website has a lot of information up about what is Click to continue reading this post
On Friday I had to give the keynote address at the Phi Beta Kappa induction ceremony held here on the USC campus. I did not know what that really was when asked, perhaps because my educational environment as a student was in the UK. (Although for all I know there are such things over there too, but perhaps I did not notice.) After a bit of googling I learned that this is an honours society and it is devoted to excellence in the liberal arts. It is the oldest one of its sort, apparently (founded in 1776), and these days although science was there at the start, the practice is to add “and sciences” when you say liberal arts now. Students who maintain a certain standard of grades through their undergraduate degree in a liberal arts and sciences area are invited to become members and then there is an induction ceremony. Sadly, no secret handshakes and strange behind the closed doors practices… Well, as far as I know. (In fact, as a thank you for giving the address, I get added to the membership as an honorary member, so perhaps a packet will arrive with my instructions about handshakes and so forth, but I doubt it.)
My speech was to be something about the liberal arts and to celebrate that and to impart some wisdom to the students and their assembled parents and so forth. I was happy to oblige and after letting it stew in background in my head for some time, come Friday morning I sat down at the computer and something nice flowed out through my fingers onto the page. People liked it – a lot, I was later told. I’m still a bit surprised (pleasantly) by that. There may be a story about it later, so I’ll post a link to that when/if it appears.
To my delight I recognised several names in the list for the ceremony. There were in fact five physics majors inducted (is that the right word?) all at the Click to continue reading this post
Thursday’s event at the Natural History Museum went very well. There was a great turnout, and the audience was very enthusiastic. As you can see from the photos*, there were two fierce-looking large dinosaurs in attendance in the audience, but it did not have any effect on the overall time-keeping, and the lectures ran over the allotted time quite a bit.
But people had fun, and the museum staff were very kind and flexible, so that’s ok. I actually learned a lot from Ed Krupp’s talk about the astronomy and astronomical objects along the Silk Road from the Far East to the Middle East especially. Laura Danly gave a talk that was mostly a detailed history the Internet including at least three internet cat videos as illustration (an emphasis that I found unexpected, I’ll admit, since I was expecting more about contemporary astronomy). It was certainly a modern perspective on the Silk Road, as we promised the audience, and it seemed to go down well. The observation opportunity that Laura arranged outside (with the telescopes that were set up in the new gardens) was also well received. Jupiter and its Click to continue reading this post
So, I don’t know why, but in addition to the catalogues I get in my work mailbox from publishers of physics books or lab equipment, I’ve started getting a lot about books in the Humanities and related subjects. Is this because those publishers know of my tendency to dabble in other subject? I’ve no idea. In any case, all of those things tend to end up pretty swiftly in the recycling bin nearest the department mailboxes. A suite of lovely new books on teaching Art History is about as valuable to me as a shiny sets of vacuum pumps or electronic controllers. I’ll admit to sometimes looking through and longing for the time I’d need in order to explore such things (vacuum pumps or Art History texts)… but then into the bin they go.
Well, earlier this week a catalogue arrived and one might be forgiven for thinking that they are really trying to get my attention with this one. It is a catalogue of Gender and Sexuality texts from Ashgate, and if the image on the cover is representative (uh, as far as I know it is not!) they’ve really developed some fancy techniques in the field!
Some of the formulae are hilarious! (And I’m trying to understand the, obviously important, inequality right in the middle…)
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I’m doing a disturbing amount of speechifyin’ this month. One of the occasions is tomorrow, and is open to the general public. Have you been to the Natural History Museum’s “Traveling the Silk Road” exhibition yet? I went to have a look a couple of days ago and it is rather nice. I recommend it. There are even live silk worms!
I’ve been coorganizing an event as part of their series of lectures that accompanies the event and I am delighted to announce that I have connected two of the most awesome spaces and institutions in the city for this one. The Griffith Observatory will team up with the Natural History Museum for this one, with a lecture and Q+A session, and then (weather permitting) a bit of stargazing in the new gardens! Please spread the word and come along:
Click to continue reading this post
Some of you are wondering what I’m working on while on retreat. Well, actually there’s a nice coincidence here. I’m working on the graphic book that you may have heard me talk about a bit. “The Project” as I sometimes call it. I’ve been doing things on various aspects of it, such as reworking the description of it for various people to look at, writing new bits, and spending a bit of time pulling together various bits of the prototype story I used to start all of this back in 2010. The prototype bits have all of my experimentation and development of style and technique all over them, and so there are pages that needed a bit of rework (to say the least). So, on Monday, Click to continue reading this post
While on a hiding retreat in another town or city, I like to seek out a local group that might be doing a “drop in and draw” session. You show up, pay your money, and there’s a safe environment (in a studio, a back room, upstairs of a pub, etc) for a model and artists to work on the wonderful business of capturing the human form in various media. I’m a reasonably private person so I like to keep the anonymity level reasonably high, but it does not only work. People are of course on the watch out to protect the group from perceived problems, so they ask questions. Others are just trying to make friends, and so they ask questions too. I just like to be polite and friendly, share the odd joke or remark, but mostly keep my mouth shut and listen to the various small talk that breaks out during breaks. Most of all, I want to get on with the business of drawing.
I went to one on Monday. This time around it was sort of amusing to me at one point when one of the organisers of the group asked me why I’d come down from LA to their small seaside town drawing group and I said I was hiding. I could sense alarm immediately (I can imagine the pictures he might have had in his mind even before I said “hiding”) and so I then went further, by way of reassurance, and said something vague but standard about wanting to get out Click to continue reading this post
I’m actually in hiding and silence for a week. It is Spring Break and I have locked myself away in a seaside town to do some writing, as I did last year. But I must break my silence for a little while. Why? Well there’s been a really great announcement in physics today and while being very happy that it is getting a lot of press attention – and it should since the result is very important and exciting – I’ve been stunned by how confusingly it has been reported in several news reports. So I thought I’d say a few things that might help.
But first, let me acknowledge that there’s a ton of coverage out there and so I don’t need to point to any press articles. I will just point to the press release of the BICEP2 collaboration (yes, that’s what they’re called) here, and urge you once you’ve read that to follow the link within to the wealth of data (images, text, graphs, diagrams) that they provide. It’s fantastically comprehensive, so knock yourself out. The paper is here.
I keep hearing reports saying things like “Scientists have proved the Big Bang”. No. The Big Bang, while an exciting and important result for modern cosmology, is very old news. (You can tell since there’s even a TV comedy named after it.) This is not really about the Big Bang. This is about Inflation, the mechanism that made the universe expand rapidly from super-tiny scales to more macroscopic scales in fractions of a second. (I’ll say more about the “super-tiny” below).
I also hear (slightly more nuanced) reports about this being the first confirmation of Inflation . That’s a point we can argue about, but I’d say that’s not true either. We’ve had other strong clues that Inflation is correct. One of the key things that pops out of inflation is that it flattens out the curvature of universe a lot, and the various observations that have been made about the Cosmic Microwave Background over the years (the CMB is that radiation left over from when the universe was very young (about 380,000 years old – remember the universe is just under 14 billion years old!)) have shown us that the universes is remarkably flat. Another previous exciting result in modern cosmology. Today’s result isn’t the first evidence.
So what is today’s exciting news about then? The clue to the correct Click to continue reading this post
“So, you have a choice. We’ve ten minutes of class left. I can either finish early, or…. I can show you that there’s actually a wormhole living in this picture, or can I tell you about Hawking radiation.”
That was the choice I presented the students with after we’d spent some time together exploring the Kruskal-Szekeres extension the the basic black hole solution, in my General Relativity class today. You probably don’t know what all that is, and that’s ok. Suffice to say that you end up with a pretty diagram which looks like two everlasting black holes put together as in a sort of elegant trading card. Or perhaps a neat knot where one black hole is sort of upside down and neatly slots into the other one so that they hug each other into eternity, acting as each others’ past and future. Look it up and see.
Anyway, they went for the wormhole, with a chant “Worm-Hole! Worm-Hole!”. So I constructed the wormhole for them… the Einstein-Rosen bridge, as it is known, ending with the sad news that it is not a real traversable wormhole that Click to continue reading this post
Sorry that it has taken me so long to get to posting the results of the USC Science Film Competition. It has been super-hectic. In addition to the usual things I have to do, I had to give a talk about science education to the Society of Physics Students – that went well, I heard – read and examine another PhD. thesis (twice in one week), do battle with two fronts of vermin attacks on my house, and prep a whole lot of other things I won’t trouble you with… Also, oddly, the time change seems to have left me in a state of exhaustion each day.
Enough with the excuses. What are the results, you ask? And is it true the winner was controversial?!
Well, first and foremost we had a fantastic time celebrating the work of all the students in the competition. About 75 or so people turned up, making all my frantic buying of things in Trader Joe’s and so forth all worth while, and there were two screening sessions separated by a coffee and snacks break. Since there were twelve films this year (a 50% increase!) there were six per session (I curated things so that the sessions were about the same length), which worked rather well. A lot of the films used quite a bit of their 10 minute allowed duration, and so given that I pause between films to give each team a chance to take a bow, it was in danger of being a long evening, and for that I apologize to everyone, but I do think that the students should get a fair amount of individual recognition for their hard work.
Anyway, to cut a long story to medium, the standard was quite high this year, with several good films at the top that were hard to choose between, but I think the 15 judges (from academia and the film industry, with scientists and filmmakers and scientists-turned-filmmakers on both sides) got it right.
The first prize winning film has resulted in raised eyebrows from some, including the filmmakers themselves who apparently were sure that their film would be overlooked due to its content. I think that the judges got it exactly right. It is a fine example of exactly what I’m looking for in this competition- a Click to continue reading this post
Just a reminder: The USC Science Film Competition Showcase and Awards are tonight (March 7th) at 6:00pm. I’ve been tallying up all the judges’ input and have the results in special envelopes to give out tonight. Very exciting. Come along (event information here), and enjoy celebrating all the students’ hard work. There will be twelve films on display!