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Trivial Solutions Don't Help
Another point of disagreement in the great voucher debate concerns what, exactly, counts as parental involvement. Eve Tushnet writes:
What vouchers do offer is the ability (and therefore the responsibility) to make a choice. Parents who are content with the public schools can choose to keep sending their kids there; many will. But the fact that they can choose to a) use their voucher money to attend a cheap private school for free, or b) use the voucher money, plus savings of their own, to attend a less cheap private school they couldn't afford before, means that parents will be able to be more involved in directing their children's education, not less.
The key point of confusion here is that, while choosing a school and writing the checks are important, they're not the sort of parental involvement I was talking about in my earlier comments. I'm talking about a daily involvement-- making sure that the kids do their homework, encouraging them to read books rather than watching tv and playing video games, taking an interest in their school activities, and supporting any academic goals they may have. Education is about more than just getting into a good private school-- there are no end of chuckleheads with Andover diplomas. Education, real education, requires an active interest in learning on the part of the student, the sort of interest that can easily be crushed by parental disinterest.
Private school doesn't necessarily provide that sort of parental support. Sure, having to shell out for the tuition provides some incentive for parents to take a more active interest in their children's education. But then, shelling out for a gym membership theoretically provides the same sort of incentive to actually exercise, and there are plenty of fat slugs out there having their credit cards dinged monthly by Gold's Gym. (I speak from experience, here...)
Private school without the sort of parental support I'm talking about is probably better than public school without parental support. But public school with active parental support is probably better than private school without.
Again, I'm just arrogant enough to think of myself as anecdotal evidence in favor of that claim-- I went to public school in the back end of nowhere, but thanks in large part to the efforts my parents made to encourage and support me, I was able to go to one of the very best colleges in the nation, side by side with kids from the very best private schools in the country, and I never felt intellectually or educationally inferior to them. In fact, the few people there who did strike me as much better prepared than I was were all public school products, while the biggest clowns I knew had diplomas from prestigious private schools.
Having to choose where to send the kids to school may be a net increase in the involvement of many parents, but it's not a particularly useful increase. And to the degree that it is an increase in parental involvement, it's also a tragedy.
Posted at 11:55 PM | link | follow-ups | 3 comments
You Want Fries With That?
So, I stepped into the "school voucher" quagmire last weekend, and seem to be stuck once again. Eve Tushnet responded to my most recent post, and a couple of people in the comments take issue with my post, in particular my characterization of vouchers as a "cop-out."
Before I get into the reasons for my statements, I'll repeat the full disclosure statement from an even earlier post: my father just retired from public school teaching after thirty-two years, and for many of those years he was an active member of the teacher's union. Accordingly, I have a great deal of sympathy for the teacher's side of these arguments, and none whatsoever for people who blame unions for everything (people who blame administrators for everything come closer to the mark...).
So, why do I say that vouchers are a cop-out? I say that because, from what I can tell, the real goal of most voucher proposals is to avoid having to actually think about the problems involved. Voucher advocates say we'll privatize everything, and then "competition and free-market principles" will take care of everything. None of the people running the system need to make any actual decisions about policy, they just need to run the system through the Magic Black Box of the Free Market, and everything will be wonderful.
The problem is, I don't find this an especially convincing argument, because it subtly misses the real point of the free market. Market competition doesn't ensure that someone will find the absolute best way to run a school, it ensures that someone will find the absolute best way to make money from running a school. The two are not necessarily the same. In one of the posts linked above, Radley "The Agitator" Balko makes a strained analogy to McDonald's in arguing for vouchers. Amusingly, I would use a superficially similar analogy to argue in the opposite direction.
If you believe the claims many voucher advocates make regarding the creative powers of the Free Market, you might expect that market competition in the food-service area would inevitably lead to gleaming, efficient, friendly restaurants nationwide, providing a rich and varied menu, and filet mignon for $5 a plate. Instead, what has it brought us? McDonald's.
The problem here is that quality is not the sole criterion people use when choosing where to get food. Price enters in, and convenience as well-- it turns out that if you forgo the search for gourmet quality entirely, and concentrate on providing mass-produced food cheaply and conveniently, you can make money by the bucketload.
You need some minimal quality, to be sure, but it turns out to be easy to meet most people's minimum quality standard. Thus, we have McDonald's and Wendy's and Burger King, and a half-dozen other big chains, making money hand over fist for selling food that, taste and nutrition wise is no great shakes. And it turns out to be very difficult to even stay in business running a restaurant that tries to provide high quality food, let alone make a lot of money at it.
This is the flaw in the market zealot vision of vouchers. In an ideal world, populated with perfectly rational (and spherical, and frictionless) people, market competition should lead to a wonderful education system, as only the schools providing the highest quality education would be rewarded with funding. But it's not an ideal world, and people are prone to irrationality, or working from different priorities than those who design voucher schemes. The result might still be quality education for all, but it might turn out that, in education as in food, convenience trumps quality, and the result will be, well, educational McNuggets.
So what should we be doing? Well, for one thing, we should be trying to figure out what it is that makes the best schools (public and private) work the way they do. Is it parental involvement? Rigid discipline? Better teachers? Small class sizes? Some combination of these? And, more importantly, is there a way to put these factors to work in schools which are currently failing? Can we get more parents involved in a positive way? Is there a combination of reforms and bonuses that can be used to entice better teachers into failing districts?
Once we figure out what works, and what needs doing, we should implement it, even over the objections of whatever entrenched interests are involved. If doing the right thing means going against the wishes of teacher's unions, the screw the unions-- I'm not going to back stupidity. If that means pissing off educational bureaucrats, well, screw them, too. If it means running trouble-makers out of school, and pissing off their parents, well, they should teach their kids better manners. If it means spending money, well, let's spend the money. If it means setting up schools run under several different systems, and shuffling kids around to find the best fit, let's do that. And, hey, if it turns out that the answer is something that can only be implemented in a private school setting-- say, religious instruction is the key factor-- then, by all means, let's go to a voucher system
If all that sounds like hard work, it is. It'll require a lot of detailed policy work to figure out what to do, and implementing the plan will require expending a great deal of political capital-- toes will get stepped on, and there will be a price to pay for that. Whatever the actual solution is, it will almost certainly be unpopular with a great many people. But it's the right way to attack the problem. Throwing up our collective hands and saying "the market will fix it for us" is a cop-out.
Posted at 11:53 PM | link | follow-ups | no comments
Tractor Beams and Thermodynamics
So, I promised (or was it "threatened"?) to finish explaining the recent Australian work on the Second Law of Thermodynamics. I've put it off for a while, but I really ought to finish that before moving on to the eight or ten other ideas I have for ways to delay packing stuff for the upcoming move...
As I noted in my previous post on the subject, there's a theorem that tells you when and where to expect to see entropy decreasing in small systems. Everybody pretty much believed in this "fluctuation theorem," but there weren't any experimental tests until this recent paper, for the very good reason that nobody could really see how to do the experiments.
The key problem here is that entropy isn't something you can readily measure. We've got a good handle on how to measure temperature, but something as nebulous as the "disorder" of a system of many particles is a little hard to measure. There are ways to express the entropy mathematically, but measuring the entropy content of real objects is a tricky problem. As Doug Turnbull notes, for a long time it was held that entropy "does not correspond to any directly measurable physical property, but is merely a mathematical function." Entropy has a real physical meaning, though, and it is possible to measure it, albeit indirectly.
The experiment devised by the Australian group is exceptionally clever. They look at the motion of a small glass bead held in an optical trap, and calculate the entropy change in the system due to the motion. The way they move the bead, and measure the tiny foces they need to measure for the calculation, provides the vague connection to laser cooling that I also mentioned in the previous post.
An optical trap is often described in popular talks or news articles as the closest thing you'll ever see to the "tractor beam" used in Star Wars or Star Trek. It's a wonderfully simple idea: if you focus a laser beam, you can trap small particles in the focus, and move them about.
The most common targets for these "optical tweezers" are micron-sized glass spheres. Conveniently, they're also used in the clearest explanation of the process I've run across, which I'll try to reproduce here: Imagine a beam of light hitting a little glass sphere. The sphere will act like a lens, and cause rays of light to bend around, and come to a focus on the far side of the sphere from the light source. A ray on the left side of the sphere will be bent to the right, and a ray on the right side will be bent to the left.
As I said when I was explaining laser cooling, light carries momentum. So, when you change the direction of a beam of light, you've changed its momentum, in the same way that deflecting a stream of water from a tap changes the momentum of the water. In the same way that the deflected water exerts a force on your hand when you deflect it, the bent light exerts a force on the sphere. Each redirected photon requires a "force" to change its direction, and in keeping with Newton's Laws, that leads to an equal and opposite force on the sphere. So a photon over on the left side of the sphere, that gets bent rightward, leads to a leftward force on the sphere, and the photons on the right side which get steered leftward produce a rightward force on the sphere.
If the light is uniform in intensity, these forces add up to zero. For every photon bent right, there's a photon bent left, and the leftward force is balanced by the rightward force. If the light varies in intensity-- let's say it's brighter on the right side of the sphere than the left side-- you get a force pulling toward the brighter part of the light. There are more photons on the right being bent left than on the left being bent right, which means that the rightward force is larger than the leftward force, and the beam moves toward the brighter light. If you focus the beam down, you create a single point where the intensity is a maximum, and the sphere will be trapped there-- any attempt to move it out of the focus will create a force pulling it back.
These "optical tweezers" are used in all manner of experiments, mainly with biological systems. They're an excellent tool for determining the mechanical properties of small systems, and can be used to drag single cells around. I may talk about some of those experiments in a later post-- there's fascinating stuff being done with optical tweezers (In keeping with my general policy of hyping my friends whenever possible, however, I'll throw in a link to the NIST experiments on optical tweezers). With some minor refinements (which I won't explain), it turns out to be possible to measure the exact force being exerted on a particle held in the trap at any given instant. That's the feature which makes the Australian experiments possible.
What they do is extremely simple-- they catch a small glass bead suspended in water in one of these optical traps, and then drag it through the water (by moving the cell containing the water, and holding the trap fixed). While they do this, they monitor the force exerted by the trap in pulling the bead along through the water. This force varies over time-- it's easy to see why if you think about it in terms of water molecules colliding with the sphere: if a bunch of water molecules strike the sphere at the same time, you'll need a bigger force to keep it moving, while if only a few hit the sphere in a given instant, you'll need a much smaller force.
By keeping track of the variation of this force, they can calculate exactly how much of a change in entropy was caused by moving the sphere through the water for a given amount of time. They repeat this many times, and for many different durations of motion, and count up how many times, for a given duration, they get a positive change (increase in total entropy), and how many times they get a negative change (decrease in total entropy).
What they find agrees beautifully with the prediction of the fluctuation theorem. For short times (less than a second), they find a fair number of experiments in which they measure a decrease in the total entropy, while for longer times, they find that entropy almost always increases. If you look at the motion for only a short time, you've got a reasonable chance (almost fifty-fifty for the shortest times in their experiment) of catching one of the events which leads to a small decrease in the total entropy. If you look at the motion for a longer time, those small decreases are wiped out by much larger numbers of events which increase the total entropy. The longer you look, the more likely it is that entropy will increase.
The data look great-- the effect is much clearer than I would've expected for something so subtle. They've also got computer simulations of the effect which agree very nicely with their observations. It's a very convincing paper. If there's a flaw to be found, it probably lies in the fact that this is a very indirect measurement, requiring precise force calibration of their optical trap, and knowledge of the exact temperature of the water and the bead. This is a well-understood technology, though, and the data are really very good. And it's not like the result is a shocking violation of known physics-- I'd expect this one to hold up.
What does it mean for life as we know it? I'll split that off into a separate post.
Posted at 2:41 PM | link | follow-ups | no comments
Laws of Thermodynamics Violated, Arthur Anderson Sought for Questioning
So, what does this all mean? Will Glenn Reynolds get his MAxwell demon air conditioner? Well, no. As Bob Park over at What's New puts it, "The title: 'Experimental Demonstration of Violations of the Second Law of Thermodynamics in Small Systems and Short Timescales,' says it all. The authors discovered that when statistical laws are applied to systems that aren't statistically significant, they don't work." I'd be a little less snide, as I think this is significant work (also, I don't have tenure), but the basic point is sound-- the Second Law is "violated" only for small systems and short time scales. We won't be seeing perpetual motion machines popping up all over the place any time soon, though some charlatans are sure to seize on this experiment as justification for their quackery.
What about the claims of the authors that "The results imply that the fluctuation theorem has important ramifications for nanotechnology and indeed for how life itself functions," then? I suspect that the sentence is basically just the sort of boilerplate hype you're obliged to tack onto any research article-- people in atomic physics almost invariably work in a reference to either Bose-Einstein Condensation or quantum computing-- but it's not an outright lie. It'd be a great shock to everyone if nano-scale engines worked exactly the same way as macroscopic ones, and some of the issues involved in the fluctuation theorem are sure to be involved. It's also true that we don't have that great a handle on "how life itself functions" on the molecular level, so you might as well invoke the fluctuation theorem there, too (in my snarkier moments, I call this the "Penrose method").
On the other hand, one of the salient features of the functioning of life is that, well, it works on longer time scales than those studied in this experiment. And if anyone ever succeeds in making functional nanotechnology, that, too, will need to run on longer time scales in order to be useful. The fluctuation theorem may slow the rate of increase of entropy fr a nanomachine, but then the Second Law never said entropy increased quickly, just that in the long run, it always increases. Nothing in this experiment changes that.
The Australian experiment is a very nice piece of work, and helps fill in the gap between the microscopic world of reversible physical processes and the macroscopic world of statistical mechanics and the Second Law. It's a significant advance in the study of mesoscopic systems, and a very clever piece of work. The future technological implications are likely to be pretty minimal, though.
Posted at 2:40 PM | link | follow-ups | no comments
A Different Religious Argument
A quick-hit this morning, as I have stuff to do. More later, maybe.
Over on the Good Ship Clueless, Steven Den Beste is pounding on the Mac vs. PC issue again. He's been harping on this for weeks now-- between this, Glenn Reynolds's hammering on BlogSpot (and his eighty-seven lame "rhinoceros" jokes), and Andrew Sullivan's tedious attempts to pin everything bad on Clinton, the people I depend on for the morning jolt of righteous indignation that I need to get me through the day are letting me down.
While I know that the Mac/Windows debates have a religious fervor exceeded (among geeks) only by the Emacs/vi wars, I've mostly lost interest, because I long ago realized that the specific hardware and software doesn't matter as much as individual Computer Karma. DenBeste can't figure out why some people prefer Macs to PC's, and devotes pages of text to deriding the system as inferior to Wintel. Meanwhile, I sit here in my office with a Windows machine that:
- Locks up completely on every third attempt to use the Zip drive-- I mean a full, Blue Screen of Death, physically cut the power sort of freeze-up.
- Occasionally freezes up-- again, a BSOD, cut the power shut-down-- when I have PowerPoint and Excel open at the same time. Since I use Excel to do my grades, and PowerPoint to do my lecture notes, this is ever so slightly annoying.
- Despite having a 1.2 GHz processor and 384 MB of RAM, can't play an MP3 without skipping and stalling and garbling the sound every time I move the mouse (forget about trying to actually use other software at the same time). It sometimes has the same trouble with CD's, and don't even ask about streaming audio over the Web.
- My personal favorite-- once or twice a week, when I start the computer up in the morning, it begins the day by informing me that Explorer has performed an illegal operation and must be shut down. This is just after I turn the power on, mind-- I'm not running anything, but Explorer crashes first thing in the morning. I'm so glad they've chosen to make it an integral part of the operating system...
Now, granted, some of these are very specific to this computer. My home computer (a 500 MHz Wintel machine with 128 MB of RAM) plays MP3's without trouble, even when I have five or six other programs running. It's got an entirely different set of charming little quirks, most notably a tendency to hang up after I tell it to shut down, and a conflict between the printer drivers and some of the scientific software I use at home. But all in all, I just have bad Computer Karma with Windows machines-- the desktop machine I had at Yale was comically awful.
On the other hand, I spent six years in grad school working in a Mac-based lab, and never had these kind of problems. They needed to be restarted once a day or so, but then so do the PC's I use now. When they were running, they ran without the constant hassles I get from Microsoft-- there weren't any pairs of programs that simply couldn't be run at the same time, there weren't any conflicts between hardware drivers and completely unrelated software packages, and the hardware add-ons never caused the whole system to melt down. But then there was a Unix-zealot post-doc in the group who had the ability to reduce the Mac OS to a smoking pile of rubble just by wiggling the mouse back and forth.
It's all personal karma. I suffer constant aggravation when dealing with Wintel machines, but do fine with Macs, while others have the reverse experience. I'm something like two-for-nine lifetime at getting freeware programs written by German Unix geeks to work, and I've basically given up on the concept, but Kate has no problems with them.
The whole computing experience is so wildly variable that I'm skeptical of any attempt to draw sweeping conclusions about the relative quality of a particular platform. I certainly can't see expending the effort some Mac and Windows people do in calling each other idiots. Especially when Unix is clearly superior to both...
Posted at 10:15 AM | link | follow-ups | 7 comments
Tools of the Trade
The other point where I wanted to take disagree with NZ Bear was regarding the tools used to keep track of weblogs:
First, nobody blogs if they don't think anybody is reading them. (Or at least, nobody I know). And right now, the tools available to us as blog readers are skewed to favor blogs that are updated very frequently --- and readers who are monitoring blogs continuously. Weblogs.com's main list is the worst example. It's great if you're monitoring it every few hours and looking to see when Glenn updates. But if you check it once every two days (let's not even think about only once a week) and are looking for three blogs that update about once a week, then good luck. You'll never find them; the tool isn't geared to that kind of usage.
Some add-ons to Weblogs' main data stream help; BlogTracker lets you select your list of blogs and shows you when they were last updated, and can be used to track blogs over long periods of time. But we need more --- more tools, more features on those tools, more flexibility in how to use them, and more independent tools that don't rely on the Weblogs,com data stream (because after all, the fatal annoyance of Weblogs.com is that it requires the blogger to ping them. We need active monitoring tools to handle sites run by people who've never heard of Weblogs.com).
I agree that more tools and some new tools would be useful-- some sort of subject-based indexing would be nice, and a way to search for weblog posts on a specific topic would be helpful (several times since I started this, I've wasted an hour looking for some post that would be the perfect link to include, if I could only remember where I saw the damn thing...). But I disagree strongly about the "fatal annoyance" of weblogs.com and blogtracker, particularly for the "once a week" blogs the Bear is recommending.
My book log is done by hand. I didn't feel like learning to use new software when I started it, and I don't update it often enough to really require the features that Blogger or Movable Type would offer. I could change over to use some blogging software, but for the limited number of updates I do, the current system works fine. So I edit the files by hand, FTP them up to the server, and then ping weblogs.com.
Of those steps, the ping is by far the least annoying-- it literally takes about ten seconds. And it's more than worth the trouble-- when I started pinging weblogs.com, I saw a clear spike in the number of people reading the book log. Also, that ten-second ping is all you need to get yourself listed on Blogtracker, which allows people to keep track of when you update, even if it's only once a week.
Better yet, the "fatal annoyance" is a complete non-factor for people using most of the popular blog tools. Blogger Pro (which I use for this site) has a simple check-box to automatically ping weblogs.com. Movable Type has this as an option as well, and I think (but can't say for sure) that Radio does as well. If you use one of these tools, there's no excuse for not pinging them, and the people involved in the exodus from BlogSpot really ought to take advantage of the service. And the people relentlessly flogging the Blogger/ BlogSpot problems should mention this feature as well.
There's nothing wrong with weblogs.com and Blogtracker that can't be fixed by people making the minimal effort to use the available tools. More tools would be nice, but the ones we've already got are perfectly functional.
Posted at 12:00 PM | link | follow-ups | no comments
Wanted: Fewer Pundit Blogs
There's been a fair bit said about Salon's new blog site. As I've spent an awful lot of time droning on about physics the past few days, and don't quite feel up to another school voucher post (I'll get to it, but probably not until the weekend), I'll make a few comments about this, and put off the second part of the Second Law business until tomorrow.
I share some of Ginger Stampley's puzzlement as to what, exactly, you get out of running your web log with Salon that you wouldn't get from setting it up on your own. I also generally agree with her opinion that this is probably a good thing (leaving aside the question of who will have the time to read all these new web logs... Other than Glenn Reynolds, that is...). Sturgeon's Law will still apply, but any increase in the total amount of stuff will inevitably lead to an increase in the amount of stuff that's not crap (yeah, I know he originally said "crud" not "crap," but "crap" sounds better, damnit...).
The comments I specifically wanted to reply to were over at The Truth Laid Bear, where the Salon announcement is deemed Good in reference to an older post, calling for "Soccer Mom" web logs. There are a number of points here I want to take issue with, starting with:
To keep to what I know best --- the political end of the blogosphere --- I know what Stephen and Glenn and Mickey and Andrew have to say about homeland security. What I want to know is what the legendary soccer moms have to say about it.
Ultimately, I think I'm really not all that interested in having a flood of new web logs wherein "Soccer Moms" hold forth about homeland security. They'll have a slightly different perspective, true, but you know what? We've already got a whole host of web logs devoted to half-assed pontificating about politics. I think that I'd actually be more interested in a well-written web log where a "Soccer Mom" held forth on, well, soccer and motherhood.
That's a large part of why, as someone I found in my referrer logs noted, I go "on and on and on and on and on" about science. It's interesting to me, I hope it's vaguely interesting to others, and it's something that you don't see a whole lot of in the blogging world. I can't resist the temptation to occasionally hold forth about politics, but impressed as I am with my own cleverness, I'm not sure I really believe my political posts are any more insightful than those of Jim Henley or Patrick Nielsen Hayden, let alone people who do this for a living. And I know I rarely put things as well as the pseudonymous Charles Dodgson, and wish I could match Teresa Nielsen Hayden's stinging indictment of American politics (or, for that matter, her cooking ability, or her very funny essay on her excommunication from the Mormon church, though I think I could live without the ability to find pictures of Jesus eating roast guinea pig... But now we're getting way off track...). The one thing I know for sure I can do that these other people can't is talk about what it's like to be a physicist, and try to give people some idea of how a scientist views the world-- in other words, I can talk about my job.
Some of the best web logs out there are the ones about what other people do for a living. I've mentioned Derek Lowe's Lagniappe several times, and his reflections on medical chemistry were one of the things that convinced me this would be a good idea. Sydney Smith's Medpundit is also excellent (and will be added to the links bar the next time I fiddle with the template) for informed commentary on medical issues. I don't have the highest opinion of economics in general, and don't always understand the details he posts, but Brad DeLong's site is another great one for finding out how people in a different business see the world (and I'm not just saying that because he said nice things about my web log...). While his political stuff tends to grate on me, Steven Den Beste does provide some interesting insights into how engineers see the world. And the True Porn Clerk Stories journal that's hit the weblogging world like some sort of virus is just terrific for this sort of thing, which is the reason why it's been linked so many times.
The "blogosphere" is overrun with journalists and pundits and wannabe journalists and wannabe pundits presenting their view of the world. We're swamped in political opinion pieces, most of which end up looking very similar, even when they come from different parts of the political spectrum. Salon's new program is bound to add more political web logs to the flood, and may even, as Ginger Stampley notes, produce the lefty Instapundit that Jim Henley's looking for.
But what I'd like to see is more occupational blogging. I'm getting tired or journalists and pundits, and people pretending to be journalists and pundits. Let's get some more people writing about what they do for a living in other areas-- teachers talking about education, editors talking about editing, caterers talking about catering, detective talking about detecting, garbagemen talking about trash collecting. 90% of such web logs will be crap, of course, but the 10% that are good will probably be fascinating in the same way that "True Porn Clerk Stories" is. And it's almost got to be more interesting than yet another round of "adjectivePundits" talking only about politics.
Posted at 11:28 AM | link | follow-ups | 11 comments
Any Time Is a Good Time for Self-Promotion
There's a new entry over on my book log, covering Will Ferguson's HappinessTM. Quick review: the book tries hard to be a Thank You for Smoking for the self-help industry, but doesn't quite manage it.
As an aside, for some reason, I have trouble keeping people named "Will" straight in my head. I didn't read this for a long time because I was subconsciously attributing it to Will Self instead of the Will Ferguson who wrote Hokkaido Highway Blues, which I liked very much. In a blogging context, I always confuse Will Warren and Will Wilkinson (which I ought to be able to remember, Wilkinson being a Terp, and having written a good account of the Final Four riots this past year. Fear the Turtle, and all that... At least I didn't confuse him with Will Gay, who's a Dukie...). I don't know why that is.
No, I don't really have much of a point with this.
Posted at 10:14 AM | link | follow-ups | 1 comment
Entropy Always Increases, Especially in My Office
I'm going to have to start calling this weblog "Australia National University Science Watch," because they're back. (A good month for Aussie science...) I talked a week or two ago about "quantum teleportation" experiments done by their quantum optics group, while this week it's a group at their Research School of Chemistry that's making news, having reported the observation of violations of the Second Law of Thermodynamics. While this probably counts as a devastating blow to the arguments of creationist wing nuts everywhere, it's not quite the earth-shattering development that some of the press coverage might suggest.
Thermodynamics and Statistical Mechanics (the two are closely linked) are two of the most overlooked great achievements in physics. They involve the study of huge agglomerations of atoms-- macroscopic samples of gases, liquids, and solids-- and the bulk properties of those objects, as well as transitions between phases, and the behavior of engines. It's an extraordinarily difficult regime to work in-- the particles are far too numerous to keep track of the individual properties of each atom or molecule (though there are people who work on computer simulations involving huge arrays of particles), and yet through statistical methods and mathematical sleight of hand, the fields have managed to evolve a grand edifice of theory that is remarkably successful at connecting the microscopic behavior of atoms and molecules with the macroscopic properties of everyday solids, liquids, and gases. It's pretty amazing when you stop to think about it.
(Of course, there's a reason they're overlooked-- thermodynamics is very abstract and phenomenological, while statistical mechanics is very abstract and highly mathematical, and they're both about as exciting as public access cable broadcasts of village board meetings. Also, there's some sort of conspiracy in academia which ensures that StatMech classes never meet later than nine o'clock in the morning...)
The best-known achievements of the field are the so-called Laws of Thermodynamics, glibly paraphrased as 1) You Can't Win, 2) You Can't Break Even, and 3) You Can't Quit the Game. Somewhat more formally, the First Law of Thermodynamics is basically a re-statement of the Law of Conservation of Energy-- Energy can neither be created nor destroyed, but only changed from one form to another. The Second Law is generally stated as "Entropy always increases," the point being that in any real process, some energy is changed into a form that's not recoverable. The Second Law is the one that puts limits on the efficiency of engines, and rules out perpetual motion machines. The Third Law is most concisely presented as a statement that it's impossible to reach a temperature of absolute zero in a finite time. The Third Law really doesn't come up much, and some textbooks more or less skip it. Like I'm going to do here.
Another statement of the Second Law is that disorder always increases-- entropy, roughly speaking, is a measure of the "disorder" of a system. For macroscopic objects, and on long time scales, closed physical systems always move from a more ordered state to a less ordered state. You can see this by considering a glass of ice water as a closed system. Left alone for enough time, the ice will always melt-- the ice, with water molecules locked into a solid matrix, is inherently more ordered than the liquid state, where molecules are free to move about randomly in the fluid. You can re-freeze the water, but only by reaching in from outside the system and doing some work on it (and in that case, the entropy of the larger system (consisting of the water, you, and your freezer) will increase). Absent any outside intervention, the molecules in the water will never spontaneously re-form into an ice cube.
There's always been a bit of a problem with this, though, in that there are a lot of qualifications in that statement-- macroscopic objects, long time scales, closed systems (the last one, by the way, is the main one tripping up the creationist nut-jobs). Thermodynamics is very much a science of average properties-- it's very good at describing the big picture, but only at the cost of giving up the ability to look at the behavior of individual particles. And it's always been hard to reconcile the Second Law with microscopic physics.
You can sort of see the problem by considering an imaginary game of billiards. If you've got two pool balls sitting together at rest on the table, that's a fairly ordered state. According to the Second Law, then, when you hit those two with a third ball, and break them apart (into a disordered state, with higher entropy), it should be impossible to re-form the state with two stopped balls stuck together.
But for this three-particle system, it's conceivable that exactly that could happen. If you reversed the final velocities of the three balls, that's what should happen-- the three should collide, leaving the two colored balls sitting together and not moving, with the third ball traveling back from whence it came. Put another way, if somebody made a tape of the collision, and played it backwards, there's nothing in physics that would tell you that you were watching a tape run backwards-- you might be a little suspicious, but it's conceivable that this sort of collision of pool balls could happen. Given enough pool balls randomly bouncing around the table, it's bound to happen sooner or later, and anyone who's spent a fair bit of time playing pool (such as, for example, my sophomore year in college) has probably seen something like it. If you replace the pool balls with single atoms, this is a process that happens all the time-- it's called "three-body recombination," where three free atoms collide, leaving a diatomic molecule and one free atom, and people have made careers of studying it.
On the other hand, if you look at the case where a full rack of pool balls is broken by an incoming cue ball, you'd have to be a complete sap not to know if the tape were being played backwards. It's still physically possible to have fifteen colored balls and one cue ball come together and leave a nice, orderly rack with only the cue ball moving, but it's not the sort of thing you'd ever expect to see happen. With sixteen balls bouncing around the table more or less at random, there are an essentially infinite number of possible arrangements of velocities for all those balls, only one of which will end up re-creating the rack. It's not strictly impossible, but it's so wildly improbable that you'd never expect to see it. When you're not talking about pool balls, but about the billions and trillions of water molecules that would need to spontaneously re-arrange themselves to form an ice cube from a glass of cold water, it is impossible, at least as far as that word has any meaning in physics.
The point is that thermodynamics only really works on large scales, and in a statistical manner. On a large scale, there are an essentially infinite number of disordered states, but only a handful of ordered states, so the probability of randomly stumbling into one of the ordered states from a disordered one is essentially zero. Once you've moved to a state of higher entropy, once you've lost the initial order of the system, the ordering will never spontaneously re-form without help. So on a macroscopic scale, it's impossible for the entropy of a system to decrease without something from outside the system putting work in to make it decrease.
But when you start talking about very small systems-- a handful of particles, say-- there aren't so many more disordered states than ordered ones, and it's conceivable that a random arrangement of velocities could move you from a disordered system to an ordered one. It's not all that likely, but it's not so unlikely that it will never happen. So the Second Law doesn't really apply to small systems. You can extend the argument to show that it doesn't apply on short time scales, either-- processes involving smallish numbers of particles that reduce the total entropy by a small amount will happen all the time, and if you look for only a brief instant, and happen to catch one of those, you'll see a short-term entropy reduction. Over longer times, though, these few events will be completely swamped by a much larger number of processes that increase the total entropy.
The difficulty in making thermodynamics and microscopic physics play nice together is not a new problem-- the Australian paper that's caused such a stir this week cites an article from 1876 (not all that long after the invention of thermodynamics, really) that pointed this out. It's a problem that's been hard to quantify, though-- how small a system do you need to have before the Second Law seems to apply? For the billiard-table example above, the critical number is somewhere between three and sixteen, but it's hard to nail down quantitatively. It was finally quantified in 1993, when the same Australian group responsible for the current work came up with the "fluctuation theorem," a mathematical expression that tells you when you can expect to find violations of the Second Law, and how big those violations should be for a system of a given size, and for a given time scale.
The new experimental results are a confirmation of the fluctuation theorem for a system consisting of a small glass bead dragged through water. It's a very clever experiment, and the results look pretty convincing, but explaining the details (including a vague tie-in to laser cooling) will have to wait until tomorrow.
Posted at 9:33 AM | link | follow-ups | no comments
Having seen a huge spike in the number of hits over the past few days, and not wanting to overrun the bandwidth limits on steelypips.org, I've cut the main page down to displaying only four days' worth of posts. I have no idea how long the traffic level will stay this high (it appears to be due to Blogger deeming this a "Blog of Note." I'm flattered to be considered noteworthy...), but the front page was pushing 100 K as it was, which is a bit much on a dial-up connection. I also did some minor fiddling with the links over on the left.
The archive files will remain huge because, well, I'm lazy and don't feel like fixing them now.
Posted at 11:05 AM | link | follow-ups | 1 comment
More Moral Education
Eve Tushnet responds to my comments on vouchers. Since she doesn't have comments, and I'd like to respond before this gets too stale, I'll half-cheat and post two long things on a weekday (it's only half cheating because I wrote the laser cooling stuff last night, and posted it this morning...).
Eve read my post as arguing for a "strict separation of school and ethics," saying in part:
But also, I'm just not sure how UP would work this separation of "values" and schooling, for a number of reasons. One is the basic practical reason that you've gotta corral the kids somehow; you've gotta keep them from biting one another, lying, carping, etc. In order to teach math, you've got to start by building a rough-and-ready, low-level ethical platform, just so they'll listen to the math stuff. This is similar to Alasdair MacIntyre's point about the virtues required by certain practices- -chess requires virtues like honesty, for example (you can cheat at chess, but that ignores the point of playing the game).
("UP" is me-- I sound much perkier as an abbreviation...)
That's not really what I was after. I wasn't attempting to claim that there's absolutely no role for ethics in school, or that we should strive to make education utterly amoral (though some of the disciplinary policies instituted in public schools seem to be aimed that way...). Eve's correct in saying that some minimum standard of discipline is required to succeed in educational purposes, and some ethical content is inescapable, and there's nothing wrong with that.
But really, while there's some overlap between discipline and ethics, they're not the same thing. "Keep quiet during class because it's rude to talk while others are speaking" is a fine principle, and a good lesson for children to learn. For educational purposes, though, "Keep quiet during class because if you don't, you'll be sent to the office" is sufficient, but it counts as an ethical precept only in a very Old Testament fire-and-brimstone sort of way. Making sure that the students take the former lesson rather than the latter is properly the job of the parents, not the school system-- if you leave ethical instruction to the schools, you're more likely to get the latter than the former.
My real point was that imparting ethics is, at best, a secondary purpose of public education, and that the failure of public schools to provide a religious grounding in morality is not, to my mind, a strong argument in favor of vouchers. But there are a few different arguments tangled up here, so I'll try to disentangle them, and make my position a little clearer.
There are really two central questions: 1) Should we regard ethical instruction as a primary goal of education? and 2) Is a failure of the public schools to teach ethics a pressing enough problem to divert public resources to solve it? I read Eve's original post, in part, as answering "yes" to both, but especially the latter question-- that because "Public schools, a.k.a. government schools, can't teach the religious beliefs that many Americans consider to be the bedrock of all other values," we should provide vouchers to allow parents to send their children to religious schools, where they can receive proper moral instruction.
I would answer "no" to both questions, and especially the latter. The failure to provide an explicitly religious grounding in morality (or any grounding beyond "Obey the rules or be punished") is not a pressing enough problem that it needs fixing with tax dollars-- it's not on the level of trying and failing to teach basic literacy, which is a big enough problem to require repairs. If you want your children to learn the religious basis of moral principles, teach them yourself, send them to Sunday School, or pay for religious school on your own. Moral instruction is not a primary goal of the public education system, and religious instruction is most definitely no business of the state's.
Another point was really a matter of missing context. Eve writes:
A couple quick final points: UP writes, "Now we want to pay to shuffle the kids off into religious schools, to free parents from the hassle of providing moral and religious instruction as well? Are parents not supposed to play any role beyond paying for clothes and video games?" Wait now hey now. How does this follow? If I send my children to a school that will reinforce the beliefs I'm trying to inculcate in and model to my children, why does that relegate me to a parental ATM?
I say that primarily because I tend to think of vouchers as a cop-out, an attempt to improve education without requiring parents or legislators to take an active and continuing interest in the process. The lament about the lack of moral guidance provided in public schools struck me as piling on yet one more abrogation of parental responsibilities. It's not an absolute and inescapable result, but it was my immediate and cynical impression.
As to the larger questions of the purposes of public education, the reasons for choosing religious education (including some very good points about complicated traditions), and so on, well, I do have a day job, which I really need to get to. Comments on those issues will have to wait a while.
Posted at 10:48 AM | link | follow-ups | 2 comments
Clever Tricks and Cooling
So, at the end of yesterday's post, I had talked about how to use light to exert forces on atoms, and change their velocity. This is the basic tool used to do laser cooling, but it doesn't get you all the way there.
The problem is that, in the simple approximation we've been using thus far, the scattering force is as likely to cause an atom to speed up as to slow down. If you know what direction an atom is moving, you can aim the laser in the opposite direction, and use the force to slow them down (this is often compared to hitting a rolling bowling ball with a steady stream of ping-pong balls-- any one ping-pong ball doesn't make much of a difference, but enough of them striking the bowling ball in succession will bring it to a stop). You can even use this method to slow down a beam of atoms, but eventually they'll stop, turn around, and accelerate back the other way. And, anyway, we'd like to cool a gas of atoms, where the velocities are randomly directed.
To do real cooling with lasers, you need some sort of clever trick to arrange for the atoms to only absorb photons when absorbing photons will make them slow down. That is, they should only absorb when they're headed toward the laser. The quirk of physics which makes this possible is the Doppler Effect.
The Doppler effect is one of the great "you know this, but don't even realize it" effects in physics. It says that the frequency of waves emitted from a moving source will be shifted, depending on the direction of motion. It's most commonly encountered with sound (Doppler demonstrated his effect by putting a brass band on a moving train, and having them play a constant note as the train went down the track)-- sounds emitted from an object moving toward have a higher pitch (higher frequency) than the same sounds emitted from a stationary source, and sounds emitted from an object moving away from you have a lower pitch (lower frequency). This accounts for the way that a police or fire engine siren seems to change pitch when it passes you, and for the characteristic two-tone engine noise of NASCAR telecasts (rendered imperfectly in text as a sort of "EEEEEEEEEEEooowwwwwwwww" thing) and little kids pretending their bikes are cars, and for the way an aggrieved younger sibling's cry of "MMMMOOOOooooommm!!!!" changes pitch as he runs off to tattle. Well, OK, maybe not the last one-- the shift also depends on the magnitude of the velocity, and few small children move fast enough to produce significant Doppler shifts.
The Doppler effect affects light waves as well (as noted previously, like all quantum objects, light insists on being both a particle and a wave, at the same time). Doppler shifts of light emitted by distant galaxies are the primary evidence of the expansion of the Universe, and even smaller Doppler shifts of the light emitted by single stars are used to detect the presence of extrasolar planets.
The Doppler shifts seen by moving atoms (the effect is the same if the source is stationary and the receiver is moving) are a tiny fraction of the frequency of light waves, but atoms are incredibly sensitive frequency detectors. Atoms will absorb and emit only very specific frequencies of light, and a tiny change in the frequency of the light is enough to prevent absorption. Or allow it.
The trick to laser cooling is to set your laser to a frequency slightly below the frequency required to make a transition between two states in the atom (this is referred to as "red detuning" since the frequency is tuned to something other than the atomic transition frequency, and since red light has the lowest frequency in the visible spectrum). In that case, an atom at rest will see light that's not the correct frequency to be absorbed, and ignore it. No photons will be absorbed, so the atom will feel no force. An atom moving away from the laser (in the same direction as the beam) will see the light shifted even further down in frequency, and again, will do nothing.
An atom moving toward the laser, though, will see the light shifted up in frequency, and will absorb photons. When it absorbs photons, it feels a force in the direction of the laser, a force which acts to slow it down. Using a red-detuned laser, then, we can generate exactly the force we want to do cooling-- atoms which move toward the laser will be slowed down, while atoms moving away from the laser or standing still won't be affected at all.
If you take a single red-detuned laser, and direct it opposite a beam of atoms, you can slow and stop the beam, without having to worry about turning the atoms around and accelerating them in the other direction. With two beams of light aimed in opposite directions, you can cool atoms in one dimension-- an atom moving to the right will see the left-bound laser shifted up in frequency, absorb photons, and feel a force slowing it down, while an atom moving to the left will absorb from the right-bound laser, and slow down. Three such pairs of beams will get you cooling in three dimensions. Atoms in such a laser field are in the same predicament as a person trapped in a vat of sticky fluid-- no matter what direction they try to move, they feel a force opposing their motion. In honor of this sort of viscous behavior, this arrangement of lasers acquired the name "optical molasses" (one of my predecessors on my undergrad thesis project lobbied hard for changing the name to "optical treacle," but to no avail. He was a weird dude...).
(There are still some technical details and additional complications before you can use this to do real cooling of real atoms-- the biggest issue being that as the atoms slow down, the Doppler shift changes, and they stop absorbing photons. To slow or stop a beam of room-temperature atoms, you need to do something to compensate for the changing Doppler shift, either by changing the frequency of the laser ("chirping" the laser), or by changing the frequency the atoms want to absorb by applying magnetic fields to the atoms ("Zeeman slowing," after the Zeeman effect, which causes a shift of the energy levels for an atom in a magnetic field. Zeeman slowing is the idea that got Bill Phillips his share of the Nobel Prize for laser cooling.). Happily, the atomic transitions aren't infinitesimally narrow (a consequence of the uncertainty principle), rather there's some range of frequencies over which the atoms will absorb light, which means that you don't have to perfectly match the Doppler shift to get cooling. Once you've slowed a beam of atoms down from room temperature velocities, this allows you to cool atoms with a small range of velocities in optical molasses using a single laser frequency.)
Doppler cooling and optical molasses are the basis for all the success laser cooling has enjoyed. Further refinements of the basic scheme allow you to trap atoms (that is, confine them to a small region of space-- optical molasses is "sticky," but atoms can still wander out of the molasses region) as well as cool them to temperatures well below the limits suggested by the simple theory (For those keeping score at home, trapping was Steve Chu's contribution, while Claude Cohen-Tannoudji explained and improved the sub-Doppler cooling mechanisms. A fairly readable summary of the field's history (it really only dates from 1975) is provided by the Nobel Foundation. I won't go into any detail about that stuff right now...).
The laser cooling mechanism is strongly dependent on the specific properties of the atoms you're trying to cool-- you need a different laser frequency for each type of atom you want to cool, and only certain kinds of atoms turn out to have properties suitable for laser cooling. We're nowhere close to being able to laser cool beer. To date, something under twenty different atomic species (of a hundred-odd known elements) have been laser cooled (a partial list: lithium, sodium, potassium, rubidium, cesium, francium, calcium, strontium, helium, neon, argon, krypton, xenon. A few other species have been laser cooled as ions, not neutral atoms, and I'm sure I'm forgetting some others).
Still, to say that laser cooling has revolutionized atomic physics would probably be an understatement. Whole classes of experiments have been opened up that were previously thought to be impossible (we ran across a paper from the early 80's once that proposed an experiment, but then pooh-poohed it as wildly unrealistic. We found the paper because we had done the experiment described, and were looking for something to help explain the results...): ultra-cold collisions, ultra-precise spectroscopy, ultra-cold plasmas, atom interferometry, quantum state engineering, Bose-Einstein Condensation, and more. There are also numerous technological applications-- already, the world's best sensors of acceleration, rotation, and gravity gradients are based on laser-cooled atoms, not to mention the very best atomic clocks in the world (at NIST in Boulder and LPTF in Paris). In the future, laser cooling techniques could potentially have a huge impact on everything from atom lithography to nanotechnology, to nuclear physics, to quantum computing.
And all of that comes from the appealingly simple and wonderfully counter-intuitive idea that you can shine a laser on something, and make it cold. Even now, more than ten years after I first heard the idea, I still think that's just the coolest thing ever. Bringing this full circle to the beginning of yesterday's post, that's what got me into grad school, and got me to where I am today. I'm not sure whether that's an inspirational tale, or a cautionary one, but there you go.
Posted at 7:15 AM | link | follow-ups | 1 comment
Not Just Air Conditioning the Laser Lab
Last week, when talking about how to do a public lecture, I wrote that:
To get the basic message across, you really need to recall what it was about the field you're in or the problem you're working on that drew you in in the first place-- you just don't get to the Ph.D. level in a science without thinking, on some level, that the field you're in is just the absolute coolest endeavor ever conceived since our many-times-great-grandparents first rubbed two sticks together and set fire to the savannah.
For me, the thing that really drew me into atomic physics was the idea of laser cooling. It's a wonderful mix of simple and complex-- the basic idea behind it all is one of those forehead-slapping "Of course! Why didn't we think of that sooner?" sort of ideas (for a physicist, anyway), but when you sit down and go through it all in detail, it actually involves quite a bit of sophisticated atomic physics. To my mind, at least, it brings together all of the best things that physics has to offer: it's conceptually simple, but applying the concepts involves quite a bit of ingenuity; it makes manifest some of the weirdest behaviors in physics, but ends up having fairly concrete technological applications.
(It didn't hurt that one of the first times I heard about the field was as an undergrad physics major, when Claude Cohen-Tannoudji came to give a talk on campus. He's a wonderfully clear speaker, and does a marvellous job conveying the cool concepts without sacrificing theoretical rigor. His books tend to be exceedingly dry and formal, but he gives great talks...)
The essence of laser cooling is this: You take a sample of atoms, hit them with a laser, and the atoms get cold. "Laser Cooling" is not, as some people seem to think, about keeping your laser from overheating, but about using lasers to make things cold.
Right about there, I was hooked, just because it's such a wonderfully counter-intuitive idea. When you think about hitting something with a laser, you don't imagine that it'll get cold. You think of lasers cutting steel in industrial processes, or the Death Star blowing stuff up (real lasers don't merge like that, of course, but it sure does look cool...). So how do you use lasers to make things cold?
The first step in explaining this is to explain what, exactly, we mean by temperature-- before you can use lasers to make things cold, you need to know what it means to be cold. And the samples we deal with in laser cooling experiments are at least a million times less dense than air, so this isn't stuff you can just stick a thermometer into and read off a number. We need to look at what "temperature" means on a microscopic level.
Temperature is a measure of the average kinetic energy of a particle in the sample. A sample of gas is made up of millions of atoms zipping around with different velocities-- as a result, each of the atoms has some energy bound up in its motion. The average of this energy for all the atoms in the sample is what we call the temperature. In a "hot" sample, say a gas at room temperature, the atoms are moving at speeds comparable to the speed of sound. In a "cold" sample, they're moving much more slowly-- the molecules making up the liquid nitrogen I used for my demos on Saturday are moving at roughly half the speed of room-temperature nitrogen molecules. In a run-of-the-mill laser-cooled sample, the atoms are moving at something like 10 cm/s-- comparable to the speed of a running insect. Something that scuttles under the fridge when you turn on the light is moving about as fast as an atom in a laser-cooled sample.
So, the process of laser cooling involves using lasers to slow moving atoms down. That's a little more concrete, but not especially enlightening without two more key facts: First, that atoms have discrete energy states, and will only absorb or emit very specific colors of light; and second, that a beam of light can be thought of as made up of "photons," which behave like little particles.
The discrete nature of atomic states is the key to all of quantum mechanics. Indeed, it was the realization that atomic states have to be quantized that gives the theory its name. This is an idea that should be fairly familiar to anyone who's taken physics or chemistry in high school-- there are only certain very specific orbits which can be occupied by electrons in an atom, and each of those orbits has a very specific energy. Electrons can move between these states by absorbing energy from a beam of light, or by giving up some of their energy in the form of emitted light. The color of the light (or the frequency of the light wave) absorbed or emitted depends on the energy difference between states, so atoms will only absorb or emit light of very specific colors, determined by the limited number of transitions between allowed states. (There's a wonderfully cheesy applet demonstrating this at the Physics 2000 site.)
Physicists, fond as we are of abstracting away unimportant details ("Assume a spherical cow..."), prefer to talk about hypothetical atoms which only have two possible states, and thus only one transition between states. In reality, there are no two level atoms (and sodium is not one of them), and the multi-level nature of real atoms turns out to have significant consequences, but it's not a terrible approximation for a lot of systems, and it makes the explanation of basic laser cooling a lot simpler.
The light that's absorbed and emitted is also quantized, coming in discrete chunks called photons. Photons are generally described as "particles of light," and they carry the energy involved in the transition between states in the atom. As with everything else in the quantum world, they perversely insist on also having wave-like properties, so the energy carried by the photon is associated with a frequency, or the "color" of the light. If a photon of the appropriate energy comes along, it can be absorbed by the atom, which will use that energy to move to a higher ("excited") state. After some time in the higher energy state, the atom will spontaneously drop back down to the lower ("ground") state, emitting a photon with the same frequency as the one that was absorbed.
So far, so good (I hope...). The key to laser cooling is that, in addition to carrying energy, photons also carry momentum. In a very real sense, they behave like little particles-- when a photon strikes an atom and is absorbed, the momentum of the photon is transferred to the atom. A stationary atom hit by a photon will thus start moving, in the same way that a bullet fired into a block of wood will start the block moving.
The change in velocity isn't a big one-- a rubidium atom which absorbs a single photon changes its velocity by about half a cm/s, so it takes hundreds of thousands of photons to bring a room-temperature atom to a halt. But photons are cheap-- a fairly weak laser of the sort used as a pointer for a talk will deposit something like 10^15 photons on the screen in one second. That's a million billion photons per second, to wax Sagan-esque (well, OK, to really be Sagan-esque, I'd have to say "a miilllllion, biillllllion photons per second"). A hundred thousand photons is nothing.
So, light can be used to exert forces on objects. That's why it's so hard to get out of the house on a sunny Monday morning, right?-- you've got this constant hail of photons to fight your way through... OK, the force is actually pretty insignificant for a massive object, but for something sufficiently small, like a single atom, it can be substantial enough to make big changes in the motion.
(The other place this turns up is in the idea of a "light sail," common in science fiction. It's a different approach than laser cooling, but a similar idea-- rather than using smallish numbers of photons to produce big accelerations of small objects, you use astonishingly large numbers of photons to produce modest accelerations of big objects. If you could make a sufficiently large sail to catch the light of the Sun, you could actually generate a large enough force to move a space ship. You need a whole lot of photons, but again, photons are cheap, and for a big enough sail and a lightweight ship, you could theoretically move sizeable objects with the force of light...)
It's this light force that we use to cool atoms. Of course, they don't hand out Nobel Prizes for simple stuff, so there are a number of complications that have to be dealt with to get to cooling. Chief among them is the fact that the light force as described above is as likely to heat the sample as cool it-- you can use the light force to make fast atoms slow down, but you can also use it to make slow atoms speed up. To do cooling, you need to find a clever trick you can use to only exert forces that slow atoms down.
But this is running really long already, so that'll wait for another post...
Posted at 11:48 AM | link | follow-ups | 2 comments
Sunday Schooling
Time for tiresome politicking. I just can't seem to get away from the school voucher arguments...
I ran across the following passage in a post by Eve Tushnet:
3) Public schools, a.k.a. government schools, can't teach the religious beliefs that many Americans consider to be the bedrock of all other values. In the absence of religious faith, public schools teach--at best!--a "civic religion" in which the claims of state and community trump the claims of God, since state and community are the only objects of loyalty that a public school can acknowledge. It is difficult to forge a civic order out of people who adhere to different faiths and believe that their God is more important than their country--on that point, the anti-voucher claim is correct. But this difficulty is intrinsic to a society that is a) mostly religious, b) diverse, and c) most importantly, free. You can't get around the difficulty by shunting poor kids into schools that extol loyalty to Caesar while being forbidden to mention loyalty to God. (As I said above, I don't think public schools actually do extol loyalty to Caesar all that often, but my point here is that civic loyalty is not the ultimate value, and I don't see why we should act as if it trumps religious loyalty or parents' responsibility to direct their children's moral education.)
While I'm not particularly religious myself (my family is Catholic, and I've been through most of the education and liminal rituals of the faith, so I have a respect for the tradition, but little deep religious feeling), I can sort of understand the feeling here. If something is that important to your life, you want to see your children brought up in the appropriate manner.
However (and there's always a "however"), I really don't see why this has anything whatsoever to do with the public schools. Faith and values are very personal things, and teaching them to children is properly the job of the parents, not the schools. The primary role of the school system is not to provide moral instruction, any more than it is to provide free day care. The primary role of the school system is to provide students with a basic grounding in the knowledge they will need to function as productive members of society. Civic values and free day care are secondary benefits, or ought to be.
If you want your children to have the proper values, it's your job as a parent to provide them-- indeed, the job is too important to be left to harried and overworked school teachers. Failure to mention loyalty to God is not a failure of the public school system-- extolling loyalty to God is simply outside their jurisdiction. Religious instruction is a matter for parents and clergy, not teachers.
Now, to be fair, the post quoted above is arguing against a claim that I find equally silly-- that public education is a unifying force that binds disparate groups into a unified citizenry. Again, to whatever limited degree that is true (anyone who speaks warmly of the unifying effects of public school doesn't remember junior high very clearly...), it's a secondary effect at best, and not the primary purpose of public education. If that is ever truly the main benefit we get out of public schooling, then it'll be past time to tear the whole system up and start over.
The quoted post is also primarily an argument in favor of vouchers for poor children to attend religious schools, not a plea to put God back in the public schools (at least, I hope it's not a plea for putting God back in public schools...). But even here, I'm not particularly happy about the implication-- this looks let yet another attempt to push parental responsibilities off onto others. Too many parents now expect the government schools to provide the sole educational force in their children's lives (resisting any suggestion that parents should encourage and supplement their children's education), and in many places, the schools have been forced to take up the additional burdens of teaching children the basics of health, and attempting to provide responsible education about sex and drugs, not to mention the day care aspects of the system. Now we want to pay to shuffle the kids off into religious schools, to free parents from the hassle of providing moral and religious instruction as well? Are parents not supposed to play any role beyond paying for clothes and video games?
But then, I've never entirely understood the motivation behind sending kids to religious schools in the first place, particularly when the goal seems to be the kind of moral indoctrination mentioned above. If you really and truly believe in the truth of your faith, and instruct your children in the faith, shouldn't that faith be strong enough to withstand contact with the real world? Indeed, doesn't it need to be strong enough to hold up against other faiths, other ideas, other cultures? You can't stand behind your children for their entire lives, ready to cover their ears and sing "La la la la la la!" whenever they encounter an idea that runs counter to your beliefs-- sooner or later, they need to stand on their own, and choose for themselves. Religious instruction that's never challenged is simply brainwashing.
The idea that the moral sense of children is so fragile that they'll simply fall to pieces if they're not constantly bombarded with religious values strikes me as close kin to the idiotic notion that the imagery of pop culture has the ability to mesmerize children and turn them into violent psychopaths. Kids are stronger and smarter than most adults give them credit for, and we do them a disservice by exaggerating their fragility.
In the end, this always reminds me of an old Dennis Miller bit, talking about one of the high-profile cases where parents sued a record company after a disturbed kid killed himself: "If your kid is going to be moved to suicide by anything Ozzy Osbourne has to say, you're not doing your job as a parent." Which is as good a summation as I can come up with right now, so I'll stop babbling.
Posted at 11:17 AM | link | follow-ups | 2 comments
A Great Morning for Vanity
OK, it's not like it's Page One of the New York Times, but yesterday's talk got written up in the Albany Times Union:
Smashing frozen flowers shows kids college is cool
As the class on laser cooling ended, the high school students crowded around the front of the Union College classroom, dipping flowers and balloons into liquid nitrogen, then smashing them to bits.
They had gasped in awe as Professor Chad Orzel poured some of the liquid nitrogen onto the table in front of him, causing the liquid to turn into steam the moment it hit the tabletop. When the discussion on the movement of atoms slowed, Orzel randomly tossed a racquetball at students to illustrate the random movements.
It was an attention-grabbing lesson, and that was the point. The 103 students -- mostly from minority families or the first person in their family to consider college -- are spending this weekend getting a chance to see what attending a university would be like.
(It's probably petty to want to correct the science errors in that...)
Now I have to go buy a paper... .
Posted at 9:25 AM | link | follow-ups | 3 comments


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Memory foam mattresses have come a long way in the past decade. PlushFoam Memory Foam mattresses have taken the many benefits of traditional memory foam and found ways to improve an already great product. These are just some of the benefits to consider should you decide to purchase PlushFoam Memory Foam Mattresses, or even if you're trying to decide between PlushFoam and some other memory foam product.
Read More // TAGS: cool memory foam, memory foam and latex, memory foam mattress, memory foam mattress benefits, PlushFoam memory foam

subset: commoncrawl


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Trillion Sensors Not Likely
15 comments post a comment
The trillion-sensor world is not going to happen anytime soon. Just do the math.
The trillion-sensor world is not going to happen anytime soon.
Bernie Cole, Embedded.com's site editor, does a great job each week summarizing a mashup of data about topical subjects. Recently he reported that GE, Cisco, and others predict that, by the end of the decade, about 1 trillion sensors will be deployed and connected to the Internet, with a market value of $15 trillion. This is part of the so-called Internet of Things.
(Daily we're faced with ridiculous IoT hype as if this were some new concept. Has everyone forgotten the notion of "embedded systems"? For about 20 years, we've been building devices with sensors that connect to the Internet; before that, they were hooked up to a variety of ad hoc networks. The IoT is a new marketing buzzword and nothing more.)
Charles Manning, a frequent commenter and email correspondent, applied a bit of engineering analysis to the notion of a trillion sensors. I've scoffed at the 1 trillion number for some time, and now, expanding on Charles' thinking, I am even more convinced that this is all some marketing person's pipe dream.
The web page for the TSensors Summits claims that about 10 billion sensors (or something like that; the wording is unclear) were sold in 2013. So it seems a median of 200 billion will be sold each of the next five years to reach the 1 trillion number.
Does it seem likely that we'll see a jump in shipments from 10 billion a year to 200 billion in the next 12 months? Not really. So presumably the final year of this decade will show the bulk of sales, with far more than 200 billion pushed out the door that year. If shipments double every year, then the aggregate sum of devices will be a bit more than 1 trillion, with about 470 billion shipped in 2019 alone.
According to a Global Issues article titled "Poverty Around the World," about half the people in the world live on less than $2.50 a day. Fully 80% squeak by on less than $10 a day. It's hard to imagine buying sensors instead of food. If the 20% with money represent the market, then 1.6 billion of the expected 8 billion people in the world in 2020 will be buying these devices. Per capita, that's 300 Internet-connected devices each in 2019 alone. How many e-gadgets did you buy last year?
What about IP addresses? Only 4% of today's connections use IPv6; 96% are on IPv4, which can accommodate only 4 billion devices.
Click here to finish reading on EE Times sister site Embedded.com.


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Hi i'm pretty new to C and am writing a program for a sports league table. I'm having a couple of problems:
I have the following code in a function to add a new team to an array of structs called teams (teams[i].name where i is next free array space):
this code semi works. It works fine if the name i enter has no spaces (eg. ManUtd) However if i enter Man Utd it places Man in teams[i].name and it places Utd in teams[i+1].name for some reason. Any ideas why?Code:void addTeam(char *teamName, int i) { strcpy(teams[i].name, teamName); }
Secondly I have made a function to try and sort an array of structs. I pass in the array of structs of type team, "teams". I call it as follows:
Here is the code:
Upon compiling i get the following errors:Code:void sortTable(team teams) { team temp[1]; for (int i = 0; i < 12; i++) { for (int j = 11; j >=0; j--) { if (teams[j].score > teams[(j-1)].score) { temp[1] = teams[(j-1)]; teams[(j-1)] = teams[j]; teams[j] = temp[1]; } } } }
"In this statement, "teams" is of type "pointer to struct declared without a tag", and cannot be converted to "struct declared without a tag". noconvert "(on the line when i am calling sortTable outside the function)
Secondly I get 6 errors saying "In this statement, "teams" has a struct type, but occurs in a context that requires a pointer. <needpointer>" (pointing to different lines of the code)
A lot of questions I know but I'm pretty lost here. Any help greatly appreciated.


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Register now for Veterans Day Parade
Sept. 24, 2011 at 4:24 a.m.
Plans are under way by the Victoria County Veterans Council for the Veterans Day Parade.
The parade will be at 10 a.m. Nov. 11 at its traditional site in downtown Victoria.
Anyone who would like to enter a unit in the parade and has not been contacted, email your request to email@example.com. An entry form will be mailed to you.
Entries should be returned as soon as possible.


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Investment, Insurance CUSO Form Strategic Alliance
Credit Union Financial Network LLC and CU Insurance Alliance LLC have come together to help leverage their relationships and offer services to credit unions at a more competitive price,
The Peoria, Ariz.-based CUFN offers investment, customized financial plan programs, insurance, business and trust services. Based in Salem, Ore., CUIA is owned by 18 credit unions.
While CUIA is focused on insurance operations, CUFN's expertise is in investment and estate planning solutions, the CUSOs said. By partnering, the two companies said they become a larger purchaser on behalf of credit unions and can continue to drive down expenses associated with the products they offer.
One example of the buying power leverage is in the employee benefits area. A subsidiary of CUIA, CU Benefits Alliance, has created a credit union employee benefits program which has reduced the benefits cost for member credit unions by an average of 23%, according to John Harris, CEO of CUIA. Some credit unions have saved more than $1 million since joining the benefits coalition, he added.
"It's all about working together and working smarter," Harris said.
With this partnership, both CUSOs said they are looking to grow into new markets and serve more credit unions.
"We exist to help credit unions earn more income and save costs through compliance and sales management of the financial planning (and) wealth management program," said Mike Prior, CEO of CUFN. "Our focus on recruiting quality advisers to provide quality advice has been well received by the CEOs, CFOs, and branch staff of the credit unions we have helped upgrade."
Along with leadership in investment program management, CUFN offers non-traditional services such as helping credit unions improve their ROA on the credit union's investment portfolio, according to Prior.
The CUSO also offers support and assistance in the recruiting of a financial adviser, developing and implementation of marketing strategies, employee branch training, community and SEG financial education workshops, as well as managing all aspects of the broker/dealer relationship.
CUIA and CU Benefits Alliance are multi-credit union owned insurance CUSOs designed to meet the insurance, risk management and fee income needs of investor credit unions and their affiliated CUSOs, Harris said.
The alliance is designed to provide both knowledge and channels for improvement in the insurance and investment relationships maintained by the credit union.


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Pages: 1
Hi community,
hope, I post my question in the right forum. If not ... sorry.
But now to my question:
I've placed my panel on the left desktop side. My Problem is, that the tasklist buttons for the open programs are variable in there height. So with one open program the button take the whole space, with two open programs each button take the half and so on. I want, that every button has a fix height (lets say 30 pixel). Is there a way to do that?
I'm using Xubuntu 7.10 with Xfce 4.4.1.
I hope, it's clear, what my problem is. If not, I could attach some screenshots.
Maybe you have some suggestions for me. Thanks in advance.
Is there no way to do that?
Pages: 1


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15 July-2014, WSJ: The Federal Trade Commission sued Amazon.com Thursday, alleging that the online retailer allowed kids to rack up millions of dollars in unauthorized purchases through its app store. In January, the agency settled similar charges against Apple for practices at its App Store. Google, which has been criticized for letting kids make unauthorized purchases through its Play store for Android phones, has so far escaped the commission's legal scrutiny.
How to stop kids from making unauthorized in-app purchases
Today, all three tech giants offer parents some controls over in-app purchases, requiring passwords to be entered periodically, or for each purchase. Here's a look at the policies:
APPLE: Users are asked to enter a password when they download an app. To make an in-app purchase, the user has to enter the password again. That opens a 15-minute window in which the user can make more purchases without entering a password.
But a user can change settings to require a password for every purchase, or to disable all in-app purchases. (The choices are at Settings > General > Restrictions > Require Password.)
Prior to 2012, Apple users were prompted to enter a password once, which automatically authorized additional purchases for 15 minutes. In its complaint against Apple, the FTC alleged that consumers didn't always understand that the password would allow additional purchases. Parents had complained about unexpected charges to Apple and to the commission. Apple changed its practices before its January settlement with the commission, in which it agreed to refund parents a minimum of $32.5 million, and change some billing practices.
Apple plans to give parents more control in the next version of its mobile operating system, iOS 8, expected this fall. In iOS 8, Apple will allow users to create family accounts where parents are alerted each time a child tries to make a purchase.
ANDROID (GOOGLE): Users attempting to make an in-app purchase must enter a password and then set controls. Users have three options. They can require that a password be re-entered every time a purchase is made, every 30 minutes, or to never ask again.
Google changed its settings in March, shortly after Apple's settlement with the FTC. Google says the settings give parents more choice, by allowing them to avoid having to enter passwords repeatedly, or to maintain strict control. Users can change the setting at any time.
AMAZON: To make an in-app purchase through the Amazon App store, users are asked whether they want to require a password for each future purchase, or permit purchases without a password. No purchase can be made before the user makes that choice. Users who choose to require a password for future purchases are taken to a parental-control screen where they can prevent any app purchases by kids or limit the amount of time kids spend on apps.


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What she said.
Not much room to defend Roman Polanski. Whatever plea bargain he didn't think was going to be honored, going on the lam isn't a solution. Because they're right to catch you, and then you have to be punished for running. Had he stayed, there's this amazing process called an appeal. It likely would have been over and done with 30 years ago. He also had a recent chance to appear in court to settle the issue, and turned it down.
It's unfortunate that many directors have signed a petition in Polanski's defense, which allows wingers to trot out their usual anti-Hollywood blather, but I understand that most of these people like Scorsese are Polanski's friends. Subjectivity is a bitch, and knowing that Polanski has walked a pretty straight line and lived a good life since fleeing is certainly somewhat reassuring. But he's got unfinished business. I look forward to him being able to walk on American soil again after he's resolved it.
Now if only those wingers were calling for Bush and Cheney's arrest…


text: Is there any technical difference between ZA free and ZA Pro? With older versions, it seemed to be some differences, but now, in the comparison table, they both have the same functions. And a remark: with older versions, one could see, in the "Program Control" table, what program uses Internet, there was a little green circle on its line. Now that column dissapeared. Am I right or there's a way to see it again? Thank you very much.


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MIAMI - Student at Florida International University's Chaplain School of Hospitality and Tourism Management are awaiting the benefits from the South Beach Wine & Food Festival.
The teaching facility for the school is currently under construction. It's Michael Hampton's pride and joy.
"We understand that this is actually one of the longest food production lines in all of South Florida," said Hampton, the dean of the Chaplain School of Hospitality and Tourism Management. "This is really the showplace."
The facility has a state-of-the-art stainless steel kitchen, a dining room that seats 140 people, and a two-story wine room.
"They're still installing the chandeliers and everything in here," said Hampton. "My favorite part is the idea that students have an environment where they can now incubate new ideas."
The proceeds from the South Beach Wine & Food Festival benefit the school. The festival kicked off Thursday.
"The proceeds have allowed us to be able to make the school's vision a reality," said Hampton.
The festival, now in its 12th year, have provided FIU with more than $20 million.
"I am very, very excited," said Luciana Page, a FIU student. "I'm still pinching myself to see if it's real."
"That's really what we get excited about," added Hampton, "is seeing that students have the opportunities to be able to do things that they couldn't do otherwise."
Construction on the 6,500-square-foot teaching facility is expected to finish in April.
Click here for information on tickets that are still available at the SOBEWFF.
Copyright 2013 by Local10.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.


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"Fascinating and engaging."Associated Press
"One of the more stirring anecdotes involves an anti-Hitler before-dinner concert that Guthrie gave with Sonny Terry and Brownie McGhee in Baltimore in 1942. After they were done, the hosts gave Guthrie a seat at the head table, and offered to feed Terry and McGheeboth blackin the kitchen. Guthrie, bless him, got thoroughly pissed off and started overturning tables while shouting over and over, 'This fight against fascism gotta start right here!'... In some sense, Guthrie and Seeger really did see themselves less as artists talking politics, and more as politicians playing banjos."The Atlantic


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or Mary E. Christiano, director of communication
(800) 424-4244
Fax: (888) 225-6935
Email: firstname.lastname@example.com
Website: www.pia.org/NY/
FOR RELEASE: Jun. 15, 2010
ATLANTIC CITY, N.J.-The Professional Insurance Agents of New York State Inc. presented David Isenberg, past president of PIANY, with the Distinguished Insurance Service award, Monday, June 14, 2010, at the associations annual conference held at the Trump Taj Mahal Casino Resort in Atlantic City. Isenberg is president of the D.C. White Agency, Long Beach, N.Y.
The Distinguished Insurance Service award recognizes an individual who has established a history of service, dedicated leadership and attention to the concerns of independent agents and their clients.
"David has been an effective and respected leader in the insurance industry," said Kevin M. Ryan, CIC, president of PIANY. "His dedication and loyalty to PIANY is to be admired. His service to our association and our profession is unique and extensive."
A professional in the insurance industry for more than 47 years, Isenberg was honored for his dedication to PIA and for his years of work on behalf of New Yorks independent agency community. A graduate of Hofstra College, Hempstead, N.Y., with a bachelor of business administration in marketing and management, Isenberg began his career at the Consolidated Mutual Insurance Group, Brooklyn, N.Y., where he served as assistant vice president. He joined the D.C. White Agency in 1978.
In addition to serving as a director for PIANY and PIA Management Services Inc., Isenberg is also a director of the Excess Line Association of New York; a member of the Professional Insurance Wholesalers Association of New York; and a member of the American Association of Managing General Agents. In recognition for all his work in the insurance industry, he was honored as the 1998 Council of Insurance Brokers of Greater New York Man of the Year, received the Louis A. Morelli award from PIANY in 1998 and named PIANYs 2007 Metro Regional Awareness Program General Agent Executive of the Year.
PIANY is a trade association representing professional, independent insurance agencies, brokerages and their employees throughout the state.


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at local and regional level
03.02.12 -
As part of its contribution to the Council of Europe ONE
in FIVE campaign, the Congress is organising a seminar
in Strasbourg, France, on 9 February 2012 (Palais de
l'Europe, room 5). It will gather a panel of experts,
grassroots players and local and regional elected
representatives. On the basis of the experiences
presented, the Congress will propose model bodies to be
set up at local and regional level to prevent the sexual
exploitation of children and to protect and support
victims and their families. The seminar will be opened
by Maud de Boer Buquicchio, Deputy Secretary General of
the Council of Europe, Keith Whitmore, President of the
Congress, and Emin Yeritsyan, President of the Congress
Current Affairs Committee. Those wishing to take part in
the seminar must register by 6 February 2012 at the
''Local and regional dimensions of the ONE in FIVE


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