Category Archives: Los Angeles

Films!

By | | , ,
1 Comment

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

By | | , ,
3 Comments

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 →

No, That’s the Other Guy…

By | | , , , ,
4 Comments

sam_jackson_tvNo, I’m not Neil deGrasse Tyson. Yes, we both talk about science on TV. Yes, we both happen to be black… but no, we are not the same guy. Also: No, I am not Jim Gates. He also sometimes shows up on TV talking about physics, and he is also black.. but no, he isn’t either me (Clifford) or Neil… He’s Jim.

This attempt at humour is inspired (in part) by real conversations I’ve had (less so in recent years, thank goodness – people are maybe better about googling first?). But mostly it is inspired by this (familiar) sad, funny, and stunningly awkward conversation from Monday* (the first 2 minutes 10 seconds): […] Click to continue reading this post →

Summing Numbers in a Small World

By | | , , , , , ,
15 Comments

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

By | | , , ,
7 Comments

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 →

Finally!?

By | | ,
3 Comments

la_clouds_02_02_2014Some rather exciting looking rainclouds, and a strong wind! Will we get some decent rain? Something like a biblical downpour, as promised by these clouds?

[Later:] A few spits of rain, but really nothing. Then back to sunshine again, disappointingly. We need some rain here in Los Angeles! Desperately.

To make the point more clearly, have a look at the site Climatestations.com for data on how we’re doing for rain as compared to the seasonal average. It is very disturbing.

If you look at the graph […] Click to continue reading this post →

Unfinished Meditation

By | | , , , ,
6 Comments

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 →

Morning Flames

By | | ,
1 Comment

sunrise_26_01_2014

I’ve a few things to tell you about from events over the last couple of days, and I want to mention some exciting events to come, but right now I must get on my bike again and head off up the hill in the park to the Griffith Observatory for an early morning meeting. As I was up again before the sun, I got to look out the window and see a wonderful – and rapidly changing – unfolding of the day. Thought I’d share it again*. Quite spectacular!

-cvj

(*See recent posts for other sunrises from recent days). Click to continue reading this post →

Celestial Card Games

By | | , , , ,
6 Comments

celestial_cardsI did not get to read the instructions about the games, but pictured are some cards (apparently from about 1830) for a game set. They have images of stars and planets on them, including one planet called Herschel. This is of course the planet to later be called Uranus. It took a while for the planet’s name to be agreed upon.

These are some of the objects from the Doheny Libary’s collection that will be […] Click to continue reading this post →

Collecting the Cosmos

By | | , , , , , , , , , , ,
2 Comments

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 →

Freedom’s Ring

By | | , , , ,
1 Comment

It is Martin Luther King day today. I noticed something I’d like to share. A team at the USC School of Cinematic arts in collaboration with the Martin Luther King, Jr. Research and Education Institute created an excellent animated mural (for want of a better term) to accompany the famous “I Have a Dream” speech. I recommend checking it out, here. From a USC news article about it, I learned that it:

“… allows viewers to scroll through the speech while learning about its history and context. Viewers can move phrase by phrase, see where King broke away from the written text …”

It is decorated by lovely drawings (which, as you might guess, is of course what caught my eye in the first place) and text and images. It uses a suite of software called Scalar, a platform designed at the Alliance for Networking Visual Culture at the school. It looks rather wonderful actually.

Go and re-live the speech once again, here.

-cvj Click to continue reading this post →

The Universe Lives!

By | | , , , ,
1 Comment

universe_shoot_16_01_2014Many people have been asking me whether the show The Universe on the History Channel and its sister channel H2, (now the longest-running science show on commercial TV in the US) has come to an end, and I’ve not actually known the answer (but have been assuming so). Well, the good news is that there are some new episodes being made! I know this since I was involved in some filming for a few segments on two episodes on Thursday. I spent the lunchtime session talking about novae and supernovae, and the […] Click to continue reading this post →

Early Fire Season?

By | | ,
Comments Off on Early Fire Season?

glendora_fire_plumeWe’ve been having a virtual Summer here, almost consistently through the Winter. Very odd. One of the consequences is pictured. There’s a huge brush fire burning in Glendora right now, over in the foothills of the San Gabriels. I woke up to a lovely sky, and then noticed the strangest looking cloud in one part of it. Then I realised it was not a cloud. So I went on to the roof to capture a bit of the scene for you. I thought it would serve as a contrast to the photo from a few days ago.

-cvj

Update: The fire was contained. Click to continue reading this post →

A New Group

By | | , ,
2 Comments

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 →