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Archive for October, 2008

Suppose you have some physical process you are want to describe, for example a simple situation where a few particles move around, possibly scatter from each other. Each particle has a few numbers that specify its particular state at a given time. It can have position (specified by 3 numbers), velocity (3 other numbers), electric charge, mass, energy etc. Once you specify those numbers you know precisely what particle you are discussing and what it is doing. If you have a complicated situation, with many particles moving around, you end up having to specify lots of numbers to completely describe the situation.

Let’s look at the inverse problem, suppose you are given a series of such measurements, can you reconstruct the corresponding situation? the trick is that those numbers don’t come labeled, no higher authority gives them names like charge or position, interpretation is completely up to you (as is always the case!). This is not that easy actually, and as we’ll see the results are sometimes ambiguous, so I’ll be generous and let you perform as many thought experiments as you want, even infinitely many. Why not? we are talking about theorist’s favorite experiments, the ones that cost no money.

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I attended a colloquium talk on Thursday at the Institute I’m visiting for a couple of days. It was a colloquium on interesting magnetic orderings. There I learned that there are many species of bacteria that produce single domain magnetic crystals of high purity.
Here is a link with some of that information. It seems that this helps the bacteria determine the up and down direction: a really difficult problem in aquatic media. Sometimes it would be really cool to be equipped with such an extra magnetic sense (especially if I get turned around in a city I don’t know). We people fake it by GPS devices or by having a compass, but who walks with a compass nowadays anyway? Also, your favorite GPS device might run out of batteries…

In any case, I often get amazed by such facts

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My Canadian tour

Ask any academic and they will tell you all about the joy that is the grant proposal. In fact, I expect you may find it hard to stop them…There are so many research grants out there, and since success rates are low and terms are short, part of your job is to become an expert on those grant proposals. There are some grants that want you to be bold, and some that want you to blur the boundaries. Some grants require you to go all-American, then others are best used to employ Russian citizens of average height. Then there are those grants that prefer you conduct interesting interdisciplinary international inter-institutional research, leaving you scratching your head. Life is so much more interesting with the grant proposal, it’s almost as good as American politics.

You may expect that in Canada, a place where around any election time you’d find relatively competent politicians arguing endlessly about the same old boring “issues”, with not a word uttered about their wardrobes (or family dramas, or bizarre rituals), even the joyful process of the grant proposal is somehow made dull. You’d be correct, of course.

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Candle in an open container spinning in a centrifuge

Candle in an open container spinning in a centrifuge

So here we have a physics puzzle to tease you a little bit. The idea is simple. You put a candle in an open container (let us say a glass, like in the restaurants). You attach the container to a centrifuge, with a long arm, and you make the centrifuge spin at high speeds.

 

The big question is: what happens?

 

 

This is sometimes the flavor of big physics questions. One puts a couple of ingredients together, sometimes in a lab, and sometimes as a theoretical exercise, and one is supposed to come up with a detailed description of what happens. In this problem there are many ingredients, and it is not obvious what is important and what is not. This is what makes these problems fun. This problem was suggested to me by Nick Warner a couple of weeks ago. I thought it would be good to release it with some picture.

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This post in “Science After Sunclipse” reminded me of one of the most beautiful ideas to come out of the continuing attempts to combine String Theory and Cosmology. The idea of Robert Brandenberger and Cumrun Vafa, dubbed more recently as “String Gas Cosmology”, is a wonderfully creative attempt to explain why our world has three spatial directions. There is no other theory on the market where the dimensionality of space could be determined dynamically, or at least come out as a result of a calculation, rather than being put in as an input, so in String Theory this is a natural question to ask. The idea for an answer,  provided by String Gas Cosmology, could be stated naturally and simply, which is what I try doing in this post. As usual, one has to remember that the devil is in the details, and those at the moment provide a real challenge for the idea.

One of the beautiful aspects of this approach is even asking the question: why four dimensions?  famously, the dimension of spacetime in string theory is larger than the observed one, in the simplest scenarios 10 or 11 spacetime dimensions, depending on details. We of course only see 3 spatial directions to move in, and can only make sense out of one time direction. Isn’t that a clean Popperian falsification of String Theory?

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Where in the world is….

 By the time you start reading this post, I will be squirming in my seat trying to get a little bit of extra leg room, or I will have landed already. In any case, just to add some meaningful content and to avoid complaining about cramped conditions in airplanes, I thought I would give you a picture I took from an airplane a few years ago. And all you have to do is figure out where in the world this picture was taken.

Hint: there are geographic features in the photo that are visible…

Where was this picture taken?

Where was this picture taken?

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You might have seen them in your shower, kitchen refrigerator or walls, or even you might have seen them hanging from the glass panel in the rear of a car you are following. They are suction cups, the product that really sucks. Erm, maybe that is not the best description of these objects, since they are very cool and useful and they don’t suck. Well, they do, but in the sense of suction, not in the other colloquial sense.

 

A cross section of a suction cup attached to a wall

A cross section of a suction cup attached to a wall

 So, how do these little suckers work? That’s the post for today. I have not explained any device recently, so I thought these would be a nice addition to the everyday physics series.

 

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Miles Davis’ second quintet

When it comes to Jazz, and probably in other parts of life as well, I am a conservative (let me add that originally that word did refer to perfectly sane people). The jazz that brings me most joy is early to mid-bebop, the music of the 1950s and 60s: Charlie Parker, John Coltrane, Thelonious Monk, Charlie Mingus,…, and yes, Miles Davis. I tend to stick with what I like, trying only occasionally to listen to earlier music (scratchy old Louis Armstrong albums, or mono recordings of Art Tatum), and even less occasionally to more recent music, with its blend of traditional Jazz, rock, folk, electronic music etc. etc.

On the other hand, I always admired Miles Davis’ ability to renew his music, getting inspiration from ever more diverse sources. How easy it is to coast: just keep doing what you’re doing so well, the craft that made you rich and famous, that brings happiness to millions of people, the thing you do better than anybody else. Making the effort to get out of your comfort zone requires amazing determination, doing it successfully requires unique talent.  That’s an inspiring story for anyone whose work requires certain component of creativity, mixed with long periods of learning and improving your craft, not unlike a scientist or a writer.

(To appreciate the risks in this total transformation, just follow Miles into the 1980s…).

In comparison to this amazing feat, it is fairly easy for me to make the effort to occasionally listen to something new. Miles Davis second quintet is one of the best discoveries I’ve had when getting out of my own comfort zone. I Started with the wonderful “In a Silent Way” (which incidentally, was my first choice for this blog’s name), and then it was hard to stop. The language of this group is so different from Miles’ previous sounds, even his own sound transformed so much, it does take some getting used to. But, it’s worth it, give it a try!

As a sampler, here is one of my favorite pieces from that period (unfortunately this cannot be embedded in the post), “Masqualero” from the album “Sorcerer”, which is probably my favorite of the group. The visual aesthetics leaves something to be desired, but the music is what counts…

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Stringy reflections on LHC

Stringy reflections on LHC

I have been attending the conference called “Stringy reflections on LHC”. This has been put together by the Clay Mathematics Institute, and here is the link. So with that wonderful title, you might be wondering what are we up to. What will follow is a quasi-technical discussion of what I have seen so far.

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Defending our turf

A couple of years ago, browsing as usual the bulletin board outside our main office,  looking for interesting talks and conferences, I noticed some odd advertisement. Apparently UBC has some sort of Christian student club, which occasionally has talks about various topics in theology. Some advertisements for these talks, to be held at the student union, were put up on our bulletin board. So, I took them down with the excuse that it is irrelevant, and that it is covering perfectly interesting announcements. The talks were not related to physics, were not taking place in our building, easy case to make. End of that story.

The next case I recall was an email circulating in our department, from the head’s office, offering free tickets to Ben Stein’s movie “Expelled” (no link, sorry). Again, one can argue that creationism is not precisely something that has to be promoted by a scientific organization, or at least one can wonder if buying legitimacy should not cost more than few movie tickets. But, really, what is the harm? The department did not endorse the guy’s “theory”, I was told, and did not force anyone to take those tickets. Do I really want to be an enemy of free speech, not to mention be such a killjoy?

Yesterday, I find in our bulletin board an advertisement (followed by an email invitation) to a talk by the esteemed creationist  (and to everyone’s pride, a graduate of the department) Hugh Ross. It is taking place in the physics building, the abstract is full of scientific sounding gibberish, and apparently on the website of his “Reasons to Believe” organization, Dr. Ross is listed as a visitor to the physics department. To add insult to injury, it was covering up the announcement for Art McDonald’s extremely interesting upcoming talk. All in all, a clear victory in the attempt to market this nonsense as legitimate science.

So, what do you think should (or is likely to) happen? in return for your thoughts I will keep you posted, and if the mood strikes me (which is pretty unlikely), I might even share some thoughts about slippery slopes, and how navigating those came to be part of our business.

update: Turns out that the group in question rented a venue from UBC, in the physics and astronomy building, to hold the event. It was not invited by anybody affiliated with the department. Nevertheless, on their website and in various advertisements the talk is listed as taking place in the physics department, and Dr. Ross is listed as visiting us (with a link to the department’s website). Blurring the boundaries is a skill, you have to admire it.

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