Films!

Good News Everyone!

The deadline for the USC Science Film Competition (now in its third year) passed, over the weekend. The good news is that I now have 12 films in the vault (a 50% increase on the two previous years), waiting for the next stage of the competition. They are on a wide range of topics, in a variety of narrative styles, and I’m super-excited to find a block of time and have a look at them. The next stage is judging, and I’ll be assembling the panel over the next day or two and letting them start looking at them and casting their votes.

So keep an eye out for more news soon. The showcase and awards ceremony is on the 7th of March, and I’ll be opening envelopes and giving away prizes with delight, I’m sure. I’ll also be posting films here on the blog for you to look at, once that date has passed.

-cvj Click to continue reading this post

Mass Matters

I was about to do a little post about where we are in the General Relativity class. We’re about to start studying our first full non-trivial solution of Einstein’s equations. Then I had this feeling I’d done it before, so I looked, and indeed the very post I thought I’d do was first posted Feb. 13th 2008. So why not re-post it for your reading pleasure?

_________________________________________________
(First posted 13th Feb. 2008)

Well, only four weeks and change behind us in this course, and… the class (see here and here) is ready to understand this wonderful equation:

the schwarzschild solution

and all that it implies. What is it? It encodes the shape of spacetime around a spherical blob of mass of total mass M. No, don’t worry too much about the details, since this is not a lecture about General Relativity….. it is just nice (I hope) every now and again to get a look at the sorts of things we use in our day to day work. This “warped” spacetime encodes what we interpret as the gravitational field (in the old Newtonian language) due to a spherical (or, to a good approximation, almost spherical) mass. Like the sun, or the earth, or that tennis ball in the corner there*. It is an exact solution […] Click to continue reading this post

Summing Numbers in a Small World

So here’s a slightly weird thing. So there’s been all this excitement over the web about the old old “shocker” that the sum of the positive integers is -1/12. You know, not even an integer, and not even positive. Apparently there have been articles in the New York Times and Slate and goodness knows where else… and I’ve been ignoring it all since I’m tired of what it often leads to: People wilfully using it as a device to manipulate people’s ignorance about subtleties with infinite processes to make the tired point that string theory is somehow wrong since it is based on “funny math”. I called Lawrence Krauss (who should have known better) out about it some years ago when he did that at an event I happened to attend. It’s a bit tedious, not the least because it is actually part of a wonderful field of mathematics that can get misrepresented, and of course because it has nothing to do with string theory.

So I ignored it all. Then some students in my class asked me about it. And I explained why it is interesting and so forth… Then I carried on ignoring it all.

Then a day or two ago a mathematician colleague emailed me to ask what […] Click to continue reading this post

Straight

In class tomorrow I’ll introduce one of my favourite equations:

[tex]
\frac{d^2x^\sigma}{d\tau^2}+\Gamma^\sigma_{\rho\nu}\frac{dx^\rho}{d\tau}\frac{dx^\nu}{d\tau}= 0\ .
[/tex]

… Wait – Where did everyone go?!

Come back! I’m not expecting you to know what it means, I just wanted to talk a bit with it sort of … nearby. If you consider yourself a bit intimidated by mathematics, be assured that it won’t bite. (No more than a piece of sheet music lying nearby will harm someone who has not learned to read music.)

It turns out that it is pretty geometry! In the equation, we’ve the object
[tex]
\Gamma^{\sigma}_{\rho\nu}\equiv\frac12 g^{\sigma\mu}\Biggl(\frac{\partial g_{\mu\nu}}{\partial x^\rho}+\frac{\partial g_{\mu\rho}}{\partial x^\nu}-\frac{\partial g_{\rho\nu}}{\partial x^\mu}\Biggr)\ ,
[/tex]
called the “Christoffel symbols”. The set of objects [tex]g_{\mu\nu}[/tex] (the “metric”) actually encode the properties of the space you wish to study (like the plane, or the sphere), and the equation at the top tells you what are the “straight lines” in that space. Well, in the plane (like your desktop) they are straight lines, while in other spaces they are the analogue of straight lines – if you want to go from one point to another point somewhere else in the space and desire to travel along the shortest path to do so, you want to follow such a line. It is called a “geodesic”. The equation is commonly called the geodesic equation.

231px-Longitude_(PSF)You know such lines, intuitively, in a non-trivial example. Next time you look at a globe (wait, does anyone but me look at maps and globes any more? I love them!), you’ll probably see examples of those lines drawn in. They are the “great circles”, the lines of longitude, and the equator. (Image used with permission.)

I just made a class worksheet that guides one through a bit of playing with this equation to get the class excited about […] Click to continue reading this post

Hawking an Old Idea

On the one hand it is good to get members of the general public excited about scientific research, and so having some new excitement about something Stephen Hawking said, driven by gushingly written articles in the press and online, can be good. On the other hand, it is annoying that the thrust of the articles are largely that he’s stunned the world again with a brilliant and unlooked-for idea. People just lap this stuff up, unquestioningly. It is actually an old idea (and in fact one that is being mis-reported – see below). One’s instinct is to just say “Welcome, Stephen, we’ve been waiting for you to join us”, or “Come on in, the water’s lovely”, and just move on, but it seems so unfair. The thing that’s most puzzling in all of this is Hawking’s own paper (which is all of two pages of words – a transcript of a talk he gave in August), which makes no reference at all to (for example) Samir Mathur’s work, which has been explicitly saying essentially the same thing for well over a decade, with a very definite proposal for how it might work. That work has hardly been buried in obscurity. Samir and many other people who have liked his idea have been working out the consequences of the proposal in numerous papers for over a decade and reporting on their results at all the main conferences, and even talking to him about it (I note that Samir was in the audience during the August talk and even politely asked the speaker to compare and contrast the similar-sounding proposals). So it is puzzling that you get no hint from the paper’s citations that this is a well-considered and ongoing idea, even if (perhaps) in detail it may pan out differently from other suggestions.

light cones in  spacetime with a compact mass - a black holeWhat’s the idea?, you ask. Well, it is not, as you might get from most of the articles (somewhat confusingly), that black holes do not exist. It is that the black hole’s event horizon, thought of as a sharp “point of no return” boundary, may not exist. Instead, it is approximation or shorthand for the complicated physics (of both matter and spacetime) that happens in the vicinity of the black hole. Simply put, the horizon arises in classical solutions to classical (i.e. non-quantum) equations (such as in General Relativity) of gravity. (See an earlier post I did about them here, from which came the illustration […] Click to continue reading this post

Unfinished Meditation

figure_27th_january_2014_1_smallAfter a long weekend of a two-day meeting of an American Physical Society committee (hosted in LA this time, so I did not have to travel far), I decided last night to go and do a drop-in-and-draw session at an art studio, to clear my mind.

The model was excellent, with a smashing hairdo and good body-awareness that made for interesting poses. I was in the mood to disappear and listen to Hendrix for three hours while focusing on the simple task of representing what was in front of me. So I did.

I’m horribly slow again. Lack of regular practice (on full figures), of course. The good news is that I have been able to hold on to some of the more important foundations that allow me to lay things out, and see forms and shapes. But it does mean that I don’t get to get to some of the finishing processes that I intuitively prepare for in the earlier parts of the drawing.

As you know from many posts of mine on the subject (see e.g. here and here) I actually like incomplete drawings where you can see a lot of the process […] Click to continue reading this post

Collecting the Cosmos

i_2014_01_24_CollectCosmos_150x200Don’t forget that on the USC campus on Friday at 4:00pm, we’ll be kicking off the Collecting the Cosmos event! It will be in the Doheny library, and there’ll be a presentation and discussion first, and then a special opening reception for the exhibition. Be sure to get yourself on the waiting list since there’s some chance that you’ll get in even if you have not RSVPed yet. (The image is from the Visions and Voices event site, and includes parts of the artworks – by artists Victor Raphael and Clayton Spada – to be included in the exhibition, so come along and see.) The event description says, in part: […] Click to continue reading this post

A New Group

The new semester is underway and it’s off to a good start. I’m teaching the upper division class that I designed some years ago on General Relativity and got put on the course catalog here at USC. My thought back then was that since we are graduating streadily increasing numbers of talented physics students, many of whom are now going to the top graduate schools around the country, we really should have an opportunity for them to learn in depth about general relativity before they graduate. My thinking was also that it affords them the opportunity to not only learn about one of the most beautiful and important discoveries (almost 100 years old now) about our Universe, but also to learn skills and ways of thinking about physics and calculational techniques that they do not necessarily see in other classes. For many students it will be one of the last classes they take in physics as an undergraduate, and so they leave on a mind-expanding high note, off into the world to do wonderful things with their knowledge. For others who may take it the year before they graduate (or possibly even a year earlier) it may inspire them in their growing love and appreciation for all of physics in their remaining undergraduate years, maybe even help them decide to go to graduate school. More about all this here.

So anyway here we are. I’m happy to say that once again the group of […] Click to continue reading this post

Thinking…

thinkingHoliday time is upon us, and in this part of it, it is coming up on Christmas time. Really fast, it seems. The semester sort of petered out mid-week for me with the submission of the final grades for my graduate electromagnetism class (everybody did really well… fantastic group of students this year), and one last two hour committee meeting for another of those committees I can’t tell you about. I’ve found some time to think about some physics, and work on a new page for the book, among other things. There’s a panel […] Click to continue reading this post

Not Struck…

…by lightning or anything. Yay.

heaven_help_us

It was fun! (See previous post for what I’m talking about.) The audience seemed to like it. I got to explain that being curious and doing experiments and forming hypotheses is somehow preferable (to some) to sitting back and saying “God did it”, and that there are a lot of nice side effects of that curiosity. (You know, increased food supply, improved medicine, better communications, travel, overall quality of life, and so forth…) We even got to talk a tiny bit about physics (somehow I got on to neutrinos…. not sure why, but then… why not?). […] Click to continue reading this post

Heaven Help Us

Well it is 6:30pm. It was my plan to take a nap this late afternoon (maybe early evening) but I’m not going to do that anymore. Why? Well turns out I’m appearing in a show this evening. It starts at midnight so I’m a little afraid that I might just sleep all the way through, wake up tomorrow morning and so miss my spot. So while the sleep would do me some good in order to be up so late, and functioning, I think I’ll skip it.

What’s the show? Well it’s a show on stage put on by some of the Upright Citizens Brigade. They asked me to appear as a guest – not as a character, but actually as myself, a scientist. It’ll be in front of a live audience, although they will be taping it later possible broadcast. You know how it goes with me – I especially like an opportunity to put some science out there here it is not expected so this is right up my alley. My understanding is that it’s a comedy […] Click to continue reading this post

New Tool

magnify_toolActually, this new tool is pretty old school, and I love it! There are times when I want to have a change of venue while doing rather detailed work for The Project… perhaps go sit in a cafe for a change, instead of at the drawing desk. But when not at the drawing desk, I could not use the lovely large illuminated magnifying glass […] Click to continue reading this post

Fail Lab Episode 12 – Finale

fail_lab_ep_12_still….In which Crystal and many of the crew chill out on the sofa after a long hard season of shows and express some of their gut feelings about the whole business. Well done on an excellent series of shows, Crystal, Patrick, James, and all the other behind the scenes people! (Warning: – This episode may not be for the squeamish!)

Embed below:
[…] Click to continue reading this post

Dining

lunch_timeWell, since yesterday was all about eating here in the USA (Thanksgiving, in case you missed that), I thought I’d share a partially inked panel from The Project, of a meal in progress. I got a bit of quiet time to work on it this evening, while listening to Jimi Hendrix and then Freddie Hubbard. They helped a lot. It is at times like this I wonder what insanity has come over me […] Click to continue reading this post