Category Archives: science

Southern California Strings Seminar

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Takuya Okuda talking at the SCSS at UCLA, Dec. 2007

Takuya Okuda talking about Wilson Loops at the most recent SCSS, UCLA, Dec. 2007. Click to enlarge.

The next regional string meeting is a two-day one at Caltech, this Friday and Saturday, organized by Joseph Marsano. It’s going to be full of interesting talks and conversations, as usual. Please encourage your graduate students to come, especially, since special effort is made to make sure that each talk begins with a pedagogical portion to help non-experts in that subfield navigate and see the motivation.

The speakers are: […] Click to continue reading this post →

Kobe as Einstein

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Did you see the Nike commercial with Kobe Bryant as Einstein?

Kobe Bryant as Albert Einstein

It is part of a series with the theme “genius”, in which he plays a variety of historical figures with a reputation for innovation. More (including the video) on Bryant’s website, and there’s a breakdown by fliptomato on his blog (where I found this).

Given the opening line of fliptomato’s blog post, I wonder if he (or the commercial makers) knows about the excellent Gary Larson cartoon from very many years back […] Click to continue reading this post →

Consider the Alternatives

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multiple parallel branes, often used as central idea of alternative universesTomorrow I’m shooting all day for a TV show that is going to focus on the idea of alternative universes (or parallel universes, if you prefer). Should be fun. The setting at least will be interesting (more on that later) and it ought to be interesting to see how the writer puts all the material together into a coherent narrative. Part of my job will be to try to emphasize that while parallel/alternative universes show up a lot in actual scientific discussions (and have done for a long time), we have not yet had anything like a good observational or experimental reason to believe in their existence anywhere other than in our imaginations. It’s vital to get this across (I hope they don’t just edit it out) because people are so willing to believe in many half-baked fanciful ideas – and this is one of them – and when they show up in a science documentary (this is (again) for the History Channel’s “The Universe” series, which has been very good) with actual scientists being quoted, one should be especially careful (as we were on the “Cosmic Holes” episode (with different filmmakers), which has proven to be rather popular, and is full of speculative ideas like travel using wormholes and time machines right alongside equally fantastic-sounding things, like black holes, which are in fact a scientific reality). The rest of my job will be to talk about some of the places where the idea shows up in modern thought, some of the reasons why, and some of the opportunities for solving various challenging problems (and maybe creating a host of others!!) can be afforded by such ideas.

All that aside, this reminds me of something else entirely – Do you ever have those days when you feel like you’ve accidentally stepped sideways into an alternative universe? I do. Recently, I had a huge dose of it. Sit back and I’ll tell you the story…[…] Click to continue reading this post →

All Creatures Great and Small

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The previous post was a farewell to black holes in the class, not here on the blog. (And it was not quite a farewell there either, since the midterm yesterday was all about the properties of the Reissner-Nordstrom black hole, representing a black hole with an electric charge, and a nice computation involving cosmic censorship.)

There have been two rather notable discoveries in the black hole astrophysics world this week. The first is the discovery of what seems to be another case of an intermediate mass black hole (there was only one example known before). Not the supermassive ones that live at the centers of galaxies (tens to hundreds of millions of times the mass of our sun), and not stellar mass ones of a few times the mass of our […] Click to continue reading this post →

A Farewell to Black Holes

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Yesterday here at USC was my last lecture in the class about black holes (see also here). We’ve got to move on to other topics (Cosmology, Einstein’s equations, etc) and so cannot do any more. It was a fun last lecture though. I pulled together a few scraps of things I did not finish in the previous lecture (such as the extraordinarily high percentage of binding energy per unit rest mass you can extract with rotating black hole orbits – just what you need to power things like quasars) and then finished with:

  1. A taste of Hawking radiation, the Bekenstein-Hawking entropy and the wonderful and beautiful subject of black hole thermodynamics that opens up when you combine gravity with quantum mechanics*, followed by…
  2. A quick discussion of the Penrose process for extracting energy from rotating black holes. (I’m sure that all (past, present or future) super-advanced civilizations must be using them as the ultimate emissions-free means of generating energy for heating their homes and so forth. No, really.)

*Of course, all undergraduates commonly hate it when you dare bring in stuff from other classes, so to […] Click to continue reading this post →

More Trouble for LHC?

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[Update:- NB: This was an April Fool joke. -cvj]

CMS detector - New York TimesSome breaking news for a change. I’ve only heard snippets of this and so I’ll update later with more as I get it. That silliness that was in the news about two physicists pursuing a lawsuit against the Large Hadron Collider has suddenly become serious. (Image right: the CMS detector at the LHC, taken by Valerio Mezzanotti – from a NYT article last year.)

Recall that the issue was that there would be the possibility of the experiment creating mini black holes that could gobble up the earth and that the CERN scientists have not done enough to demonstrate that this was not a safety issue. Of course, and has already been said in several places (see e.g., Phil’s general level post about the physics and the case here), this is utterly ill-conceived and in any case certainly not the way to go about things, but it seems that the legal route can be quite damaging for science, in the right hands.

What seems to have happened is this. Since the suit was filed in Hawaii, it falls under US Federal jurisdiction, and has been taken up as an emergency issue before the Supreme Court. Somehow the litigants got a hearing on this with the help of powerful friends who have what can only be thought of as another example of the anti-science agenda we’ve a lot of in various branches of the government in recent years.

The upshot is that the Supreme Court has announced today that they are requiring all […] Click to continue reading this post →

Liberated Penguins

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[Update:- NB: This was an April Fool joke. -cvj]

Well, I learned recently* that the BBC wildlife program makers have done it again, breaking new ground in scientific discovery while making a new series. Quite amazing this time. From the Daily Telegraph website:

The BBC will today screen remarkable footage of penguins flying as part of its new natural history series, Miracles of Evolution.

Also:

penguins in flight image from daily telegraphThe programme is being presented by ex-Monty Python star Terry Jones, who said: “We’d been watching the penguins and filming them for days, without a hint of what was to come.

“But then the weather took a turn for the worse. It was quite amazing. Rather than getting together in a huddle to protect themselves from the cold, they did something quite unexpected, that no other penguins can do.”

Above right (click for larger view) is a screen shot that I took of the incredible footage […] Click to continue reading this post →

Law Vs Law

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A silly lawsuit vs the search for physical law, that is. What’s the story?* An attempt to stop the Large Hadron Collider (LHC) in Geneva from operating over fears that the experiment will destroy the earth by creating a black hole that will swallow it up. Or some other bogeyman. Article by Dennis Overbye here, or here, and there’s a Fox News story by Paul Wagenseilhere.

The lawsuit, filed March 21 in Federal District Court, in Honolulu, seeks a temporary restraining order prohibiting CERN from proceeding with the accelerator until it has produced a safety report and an environmental assessment. It names the federal Department of Energy, the Fermi National Accelerator Laboratory, the National Science Foundation and CERN as defendants.

Quite an entertaining read can also be found at the two plaintiffs’ website. The main […] Click to continue reading this post →

Bigger than the FCC

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We’ve been studying rotating black holes in my class this week, which has been fun. We get to apply the techniques we’ve been honing in the context of the Schwarzschild solution (link to recent posts below) to a bit more complicated solution, the Kerr solution, which includes rotation. Some equations follow, although you needn’t be put off by them. Most of this will make sense without really understanding them much. Just so you can see the shape of the things we scribble, I’ll show you the equation that captures this curved spacetime geometry, with no real explanation (sorry):

kerr solution

Here [tex]\Delta\equiv r^2-2Mr+a^2[/tex] and [tex]\rho^2\equiv r^2+a^2\cos^2\theta\ .[/tex] The parameter [tex]a[/tex] is the ratio of the solution’s spin or angular momentum [tex]J[/tex] to its total mass [tex]M[/tex], measured in appropriate units. It’s a very important solution to get to grips with, since it’s not just fantasy physics, but highly relevant for astrophysics since black holes that are “out there” are unlikely to be non-rotating, and in fact, one can expect them to be rotating at quite a clip in many cases. A good many black holes – including some of the […] Click to continue reading this post →

Sand, Man

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sand dune from 2006 trip to Death ValleyIn physics, most of what we do is look for the simple, often in extremely complicated systems. If you’re asking the wrong question, or looking at the wrong aspect of the system, this quest for the simple is unlikely to work at all, but the right question asked about the right aspect can yield rather striking insights, often with far-reaching consequences. Although it often is not emphasized in this manner during our school or undergraduate (and sometimes even graduate) education, this is the primary skill in the physicist’s arsenal that we teach and learn. (See an earlier article here for a take on this.)

Sometimes, you don’t need the sharp eyes and years of training and drilling in these seemingly arcane (but, I’d argue, most natural) arts (and the requisite sequestering away in monasteries and nunneries with abstinence, self-flagellation, and so forth) – there are times when if just jumps out at you that there’s a simple question or two […] Click to continue reading this post →

Lighting Up Field Theory

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Sidney Coleman lecturingI got an email from one of the group’s graduate students today*, pointing to an archive of videos of lectures by the great Sidney Coleman. He’s doing quantum field theory. This makes this a marvelous resource, in principle, and so I thought I’d share them with you. They are here.

I wonder: are these the lectures that Jacques Distler has mentioned attending a few times in the past on his blog? This was the 1975-1976 year, a graduate course. I wonder if anyone (else) I know was in that class room…

[Update: I learned from the discussion over on Jonathan Shock’s site that there are some partial lecture notes from the course here, by Bryan Gin-ge Chen, based on notes by Brian Hill. He’s looking for help on completing the project, so get in touch if you want to help out..]

I’ve never seen Coleman in action before, and so I was immediately rather curious, […] Click to continue reading this post →

Biggest Binoculars Ever

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Large Binocular Telescope (image courtesy of the LBT)

Am I the only one who sees this, or does this look like the head of some giant friendly robot, all smiles with big cheeks? Remember Brad Bird’s Iron Giant, for example?

Well, it is actually not from science fiction but science fact. And it is a robot, sort of – well it can be controlled remotely to swivel its head and so forth. It is actually a […] Click to continue reading this post →