I just happened (while flicking channels to try to avoid the
naked mud-wrestling, oops, women’s beach volleyball*) to run into a broadcast of the Los Angeles Public Library conversation between KC Cole and Lenny Susskind about the amusingly titled “Black Hole War” between him and Stephen Hawking and the circle of ideas and theories connected with all of that wonderful area of physics. (I blogged about it here and here.) It looks like it was really good (I just caught some of the questions and answer […] Click to continue reading this post
Well, you may not have gone to the chat between K C Cole and Leonard Susskind that I mentioned a while ago at the LA Central Library downtown. I couldn’t make it either, being away at the Aspen Center for Physics. I expect it was good. Anyway, I found a little bit of a report on the conversation, done by reporter John Johnson for the LA Times. It is here. (Clickable image of Susskind to the right is by Matthew Black, for the LA Times.)
It gives you some of the simply-stated reasons as to why there was a big argument between Stephen Hawking and Leonard Susskind in the first place (and between several other physicists too… there are hosts of people working on these things, and it took hosts of people to sort it out to where we are now, not just those two, giants though they are). I recommend having a look, as it is especially for the lay-person, and will give you a good idea of what the fuss is about.
You can also see a little bit about his new book on the subject and a link to a video interview with Brian Cox (the physicist, not the actor) at the LA Times blogs here. There are also links to his Stanford continuing education course on quantum mechanics, including the online lectures you can view at your convenience. What a resource!
You might wonder why we care about all this, since currently the only way we know for sure to make black holes in the universe (astrophysical processes making stellar black […] Click to continue reading this post
Somehow, I only learned about this today, and it is already standby tickets only, but you never know. If you’re in LA and interested in a different kind of conversation, consider taking in the event (part of the Aloud series) at the downtown Los Angeles Central Library tomorrow night at 7:00pm. It’s between two friends and colleagues of mine, the science writer K C Cole and the scientist Lenny Susskind! The event is entitled, “The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics”, and presumably will be about Lenny’s reflections on some of the exciting squabbles over various important issues in black hole physics that took place (and still take place) in our field of physics. The above turns out to be (I just learned from a Google search) the title of a book he’s written, so you might be interested in it for your Summer (or other) reading.
Some of you may recall her really great conversation with Alan Alda that took place at USC earlier this year. I reported on it here. K C tends to run these sorts of […] Click to continue reading this post
Good news everyone! GLAST has been launched successfully. GLAST stands for Gamma-ray Large Area Space Telescope, and it does exactly what it says on the packet. It is an instrument designed to look more closely at gamma rays from outer space. More here. It will help (alongside other instruments such as SWIFT) get better understanding of a wide range of gamma-ray emitting objects, that pertain to a wide range of issues, astrophysical to cosmological.
“Gamma ray bursters” are obvious super-powerful sources of gamma rays out there, largely due to macroscopic astrophysical objects (collapsed stars or stars in the process of doing so, or merging with each other – see earlier posts) doing violent things, or interacting violently with their surroundings. So are active galactic nuclei, powered by black holes. We’d like to better understand all of the processes that allow these objects to generate gamma rays.
Other sources could include particles and antiparticles annihilating each other and (by […] Click to continue reading this post
Well, I’ve been quiet here because I got rather swamped with lots of things over the last few days. The biggest thing was yesterday. I gave a colloquium at Caltech entitled “Cooking with Quarks and Gluons: Recipes from the String Theory Kitchen”. The abstract is given below. It is mostly based on what I wrote about last Summer.
With all the other things I had to do (including writing and giving two fun two hour lectures on cosmology in my undergraduate GR class) I still decided that it was time to totally rethink how I tell this exciting physics story, and how I present it. This meant designing and building many new slides. Each slide can take a long time to prepare, so this took two solid days of hiding away while designing and building them, only breaking for the other stuff.
Well, it was fun in the end, and today I am exhausted. I decided that you should not miss out entirely on the treats, so I made a little movie of the first parts of the talk to […] Click to continue reading this post
Well, I’ve said (and pointed to) enough on the matter, but I could not resist a quote from today’s essay by Dennis Overbye in the New York Times (do have a look at the rest of it):
Besides, the random nature of quantum physics means that there is always a minuscule, but nonzero, chance of anything occurring, including that the new collider could spit out man-eating dragons.
Excellent! Proper flying, armoured, fire-breathing, talking, treasure-hoarding, […] Click to continue reading this post
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
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:
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…
- 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
[Update:- NB: This was an April Fool joke. -cvj]
Some 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
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
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):
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
Black Holes, by Tamsin Van Essen. Part of a series of lovely ceramics with a physics theme. For more, visit the websites here and here.
As you may recall from the post I did some time ago, the “Light Cone” is a rather important concept in physics, and keeping track of it in a given physical scenario is an extremely important tool and technique for understanding many physical situations. (I urge you to review that post before continuing reading this one.)
One way to understand a most important concept – the event horizon – is by keeping track of lightcones, and so let’s go ahead and explore that here. The outcome is that […] Click to continue reading this post
Not long ago David Morrison (UCSB) came to the mathematics department here at USC to give a colloquium.
This was a treat for me for many reasons. Here are three:
- It’s always good to see Dave. He’s one of the people I’ve known in the field was since my very first postdoc when I was learning to survive in the big bad world on my own after graduate school. I mostly could not understand a word he or anyone there else said in those days (IAS Princeton, right in the belly of the
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From the Chandra X-ray Observatory site (where you can find lovely larger versions of this image):
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Over on Correlations, I talked a bit about the History Channel’s science show “The Universe” (as I have here), and pointed out that the new season (season two) has already begun being broadcast. Here’s hoping that it’s a good series of programmes that will be enjoyable and informative. The show’s website is here.
Well, I’ve learned that the second episode, tomorrow’s (showing at 9:00pm), is one of those that i did some shooting for over the last two months at a number of places around LA. Rather than repeat, here’s what I said:
The next one, to air on Tuesday the 4th December, is called “Cosmic Holes” (yeah, I know), and the subject matter will be right on the edge of the known and the unknown, talking about black holes, white holes, and wormholes. While we know that the first are out there, the second two, while also solutions of Einstein’s General Relativity, are still theoretical constructs (and not without problems). The show explores some of the ideas and the prospects for the ideas surrounding
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