Some time back I did a Slashdot post on IP over laser: It should be possible to route IP packets over inexpensive laser pointers for pretty large distances... [Using Google] I found several instances of people doing RS-232 over laser, but very little about IP over laser. I still think this is an interesting cool idea, particularly if the government claims eminent domain of today's Internet.

Ten or fifteen years ago, I was fooling with using bright LEDs to send pulse-width modulated voice signals. You want to use PWM for noise immunity, because the linearity of LEDs and phototransistors isn't very reliable and because you want to see nice clean edges. Something like PWM would of course be excellent for sending bit sequences.

Save yourself a heap of trouble and use visible light. You'll be able to see what you're doing. If you need secrecy, encrypt the bitstream but don't use light you can't see.

In a light transmitter, you want good collimation, so that the light will travel as far as possible. This means you want a point-like emitter, placed at the focal point of your lens, and you can adjust this by forming a spot on a distant wall. Of course if you're using a laser pointer, it's already collimated.

Light rays entering the receiver want to be collimated so that the image of your light emitter will form a point right on the sensitive part of your detector. So the detector sits at the focal point of its lens (or parabolic mirror) also.

The receiver wants the light-gathering property of a telescope. The primary lens or mirror (the first thing the light hits) should be as large as possible. When I was tinkering with this stuff, I used an inexpensive 8.5x11 Fresnel lens sold at Staples. If you wanted something less cheesy, you could become an amateur telescope builder or go out and buy a telescope. From one of the web pages below: Unlike a telescope... we needn't bother trying to obtain an actual detailed image of the light source. We need merely to gather as much light from the source as possible. Also, adjustable focus is not needed. A light communications antenna then can be much simpler and cheaper than a telescope.

Another important property of the receiver is bandwidth of the receiving circuitry. It's easy to crank a lot of bits per second through the transmitter, but getting them back out of the receiver can be a challenge. Detectors (phototransistors and photodiodes) are in many cases quite limited in bandwidth. One trick is to keep the voltages on all pins of the detector at constant voltages, and only allow the currents to change. This can be done by AC-coupling the detector to a virtual ground (like the input of an op amp, or the base of a transistor).

Forget about doing this with something hand-held. At a minimum, put the transmitter and receiver on camera tripods (put a UNC-2B 1/4"-20-thread C-mount on the bottom of whatever they're mounted on). Better yet, make it a permanent fixture on the side of a building or something, but make sure the aim is adjustable in some way.

• http://www.n1bug.net/tech/laser/alc_wa6ejo.html -- Amateur radio laser communication, voice not IP packets. LOTS of fantastic technical information.
• http://www.messaggeri.it/xoptoelettronica.htm -- Where to buy optical supplies. A number of light receiver circuits, maybe 1/3 of the way down the page, of which the first was designed specifically for Ethernet over laser.
• http://www.hut.fi/Misc/Electronics/circuits/laserl ink.html -- This guy sent 115.2 kbaud serial information over a laser link. He used a pre-built laser receiver (Hewlett Packard HBFR-2521) but I can't easily find any information about it.
• http://www.qsl.net/wb9ajz/laser/data/cheepo.txt -- Here's another ham who built a very inexpensive transmitter and receiver, for sending Morse code, so the bandwidth is very low, but he has some good ideas.
• http://www.clansullivan.com/joseph/projects/laser. htm -- Another RS232 over laser project. Includes a discussion about how to modify the laser pointer.

So you've got two locations (one with electrical power but no Internet access), and each one has a transmitter and a receiver, and you can send bits back and forth at a decent rate. You'll need a computer that talks to the transmitter and receiver and functions as their connection to the local LAN, effectively I haven't thought about this part very hard so I'm going to wing it, and assume that anybody attempting this will know this part better than I do.

I'm a Linux bigot and I'll assume that nobody would ever do this with anything other than a Linux box.

The immediate problem is connecting the transmitter and receiver to the Linux box. You want to handle lots of bandwidth. Probably the easiest thing to do is connect to the parallel port.

Then you want to make the transmitter and receiver appear to the operating system as a network device (like a NIC card). The best idea would be to write a network device driver that looks like one of the existing drivers. Apparently there is SONET hardware with similar characteristics for data flow, because it does laser transmission over fiber optics. There may be examples of this in drivers/atm/suni.c or drivers/atm/nicstar.c.

Once you managed to write the correct device driver, you'd set it up with /etc/modules.conf and /etc/sysconfig/network-scripts/ifcfg-ethX.

So I finally saw the "what the bleep" movie a few days ago. My sister has been going crazy about this movie. She thinks it's the greatest thing ever recorded on movie film. Sometimes she goes a little overboard in her enthusiasm for things, particularly when she feels they validate whatever choice she made but felt uncertain about.

The discussion of the limitations of scientific knowledge was great. There's a lot of stuff we don't know. It's true that we don't know what wave-particles are, and it's true that virtual particles pop in and out of existence. That doesn't mean that there are no rules at all in the universe, or that the human pursuit of science has been a complete failure in finding any of those rules.

My sister is exactly the kind of person who will use this movie to reject any scientific knowledge that she doesn't like. What will confuse non-scientists is that the movie suggests that science actually doesn't know anything at all, that all scientific knowledge is suspect or invalid. That's just not true. If it were, planes wouldn't fly and cars wouldn't drive. The technology we use every day has its roots in scientific knowledge, and some of that knowledge is valid.

I did like the message that people have free will (or at least are better off if they act as if they do), and that it's OK to love yourself. Those are great life-affirming messages, and if people want to do affirmations or meditations or visualizations or whatever, that's great. I can't say that I see these as direct corrolaries of ideas in quantum mechanics, as the movie suggests.

It turns out that there are currently several interpretations of quantum mechanics, with varying degrees of acceptance in the scientific community. Majority opinion favors the Copenhagen interpretation, where the wavefunction collapses when observed, so the observer has a special role. In other interpretations, the collapse of the wavefunction is not a special event and so an observer has no special role. Particularly interesting among these is the many worlds interpretation.

In the movie, the special role of the observer is used to suggest a connection between the exotic mystique of quantum mechanics and the everyday utility of a notion of free will. As I said, it's great to promote self-esteem and free will, but the connection of these psychological issues to quantum mechanics seems contrived.

But it's a fun movie, the animations are pretty and amusing and delightful, and I recommend it as a visual and cognitive experience. I don't recommend that everything it says be accepted without exercising one's own thought process. And the movie's website is ridiculously self-serving, but we all expected that.

People who know me know that I've had a deep interest in nanotechnology for a lot of years. There was a Scientific American article in 1989 describing cell repair machines that got me interested, and soon I read Engines of Creation and started reading and posting on sci.nanotech, going to conferences, and occasionally even writing software. So I'm down with the whole molecular manufacturing thing. One of the particularly interesting ideas associated with nanotechnology is the post-scarcity society.

Imagine a robot with enough smarts and dexterity that it can build a copy of itself. Call this a "capable robot". Start with one capable robot, tell it to make more of itself, go away for a few months, come back, and you have an army of them. Not surprisingly, this has economic implications.

Those economic implications depend strongly upon the cost of the input materials that the robot uses for self-replication. If the robot is only snapping together two complex subassemblies, then there are no implications. If the robot digs up ore and smelts it into metal, makes its own lathes and drill presses and nuts and bolts, and purifies its own silicon from rocks and sand, then the implications are big.

The implications are big because the input materials are cheap. The robot does not have to participate in a complex interwoven economy to get its subassemblies, it makes them itself. The price of a freshly-minted robot drops to nearly the same as an equal weight of rocks and sand. You can give the robot to anybody and they can instruct the robot to make more robots.

The price of a capable robot is infinite today (completely unavailable), and some day it will be billions of dollars, and a year or two later it will be falling precipitously and it will level off near the cost of the raw materials to make a new robot.

If capable robots were distributed to every village, they could change life on Earth. Poverty could be wiped out. Diseases could be cured. We could live in a robot-labor-powered paradise. It has been argued that we might easily end up in a robot-labor-powered hell of perpetual unemployment. So the distribution of capable robots is important to understanding how they would reshape the world.

So there are some interesting questions.

• Is this "capable robot" idea possible at all? In the short term, it's more efficient to manufacture stuff in stages (one guy smelts ore, another guy builds a metal lathe, and a third guy builds a building). The capable robot trades away economic efficiency in favor of economic opportunity.
• We are currently on a trajectory of increasing concentration of wealth; the gap between rich and poor is growing while the middle class is shrinking. Can capable robots turn that around? What mechanisms and policies can we put in place today so that when robots arrive, the poor and unemployed aren't left behind?
• How do these questions and answers change when we replace robots (presumably built with technology available today) with mature nanotechnology? The cost of inefficiency declines.

As far as the thing about not leaving the poor and unemployed in the dust, Marshall Brain has suggested that everybody get a $25000 minimum wage just for breathing. It's interesting, and even affordable. I have what I think may be a better idea.

Suppose Acme Robots (or a real robot company) offers robot purchasing savings accounts. I open my account and plunk down twenty bucks. Then I go about my business for ten or fifteen years. My money collects interest at some reasonable rate, and one day the price of a capable robot decreases to the amount in my account. On that day, Acme Robots ships me a capable robot (or just tells one of their robots to walk to my house). In the developing world, the initial deposit might be shared among all the families in a village, or a group of villages. When the robot arrives, one of its jobs is to make more robots.

Could cheap robots help to discover new medical treatments, or find the next new galaxy or solve the next mathematical grand challenge? These are more computer questions than robot questions since the challenges involved (aside from the physical working-in-the-lab part) are primarily cerebral. So: Could advances in computer hardware and software trigger advances in scientific and medical progress? I think so. Big fast computers enable simulation. They enable literature database searches. They can sift through mountains of data to find correlations that might be too subtle for human minds to notice.

People in science and technology, for the most part, maintain a working assumption of materialism: that the mind is an activity of the brain, that there is no soul or spirit beyond the mind, and that when the brain dies, the mind or soul ceases to exist. Empirically I've found that doctors are often staunch defenders of materialism. This seems to be because of the consistent correlation between locations of brain injuries and consequent changes in habits or cognitive faculties.

The death of my wife gives me a reason to re-examine the assumption of materialism. I'd accepted it without much thought in the past, but now I have a more compelling interest in its veracity or lack of it. Being a geek, schooled in the ways of geeks, I took plenty of math and science courses, including probability and statistics, including hypothesis testing, as part of a course on detection and estimation. I also learned about the scientific method.

What does the scientific method tell us about the theory of materialism? It says that materialism is a viable theory only (A) if it makes falsifiable predictions, and (B) none of those predictions has yet been falsified by empirical evidence. Can we ever prove a theory is correct? No, theories can be disproven, but not proven. The closest we can come to proving a theory is to disprove all known competing theories, and the "proof" lasts only until there's a new competing theory consistent with the data known thusfar.

There are competing theories. Some of these are dualism (the idea that mental phenomena and physical phenomena are of fundamentally different stuff), idealism (the idea that there is really only mind, and physicality is an illusion), and functionalism, the idea that mental phenomena are fundamentally software, and can therefore exist on substrates other than brains (though I have a hard time seeing a conflict between materialism and functionalism, since functionalism only talks about how the material is organized).

Some dualists like the idea that there is "another world" inhabited by souls or spirits, which somehow influences this one. In this view, living means some kind of inter-world connection between a soul and a body which is broken when the body dies. Various questions remain unresolved, and the idea of two different, somehow-intersecting worlds just rubs everybody's esthetic sense the wrong way. I'd accept it if it were the only premise whereby my wife's spirit could somehow survive the death of her body, but it has the air of implausibility about it.

Another idea is that science will grow to include both physical phenomena and spiritual phenomena, and we will see that spirits or souls survive the death of the body and that it is ultimately sensible and reasonable that they should do so. This idea, which I admit is comforting to somebody with an engineering background, has been put forth by various psychics and mediums.

If you've seen N strange phenomena (where N is large) and you've shown all of them to be fraudulent, have you proven that no strange phenomenon can ever be genuine? No. Maybe the (N+1)-th phenomenon just happens to be the first geniunely spooky thing you'll ever see. William James commented that it suffices to find one white crow to disprove the proposition that all crows are black. He called Leonora Piper his white crow.

Now a lot of really stupid stuff has been said in defense of kooky ideas, and a lot of people making extraordinary claims have rightly been shown to be frauds. But there are some researchers, who've examined the data carefully, and conclude that the case for spooky stuff is really pretty compelling. Too few investigators are using statistical methods, but some of them are. That means we can have a meaningful debate about the merits of the data, the experimental methodology, and the interpretation of the data.

A few final thoughts on libertarianism. One: read David Friedman's brilliant book The Machinery of Freedom. Two: the "free market" is often distorted because deep-pocketed corporations and organizations can change the rules of the game by buying cooperative legislators and politicians, which is hardly news, but it argues against Bill Gates's notion of "frictionless capitalism". Sure, it's frictionless if you have several billion dollars to spend on grease. Three: if I were a standard-issue libertarian, I'd indulge a knee-jerk impulse to blame the recession on violations of the free market, but free market violations don't appear to me to be playing a big role here.

The other day I stumbled across this rather fascinating essay by one of my favorite authors on Buddhism, Geoffrey DeGraff, who was ordained in the Thai forest tradition under the name Thanissaro Bhikkhu ("bhikkhu" meaning "monk"). Some other of his really interesting writings are Wings to Awakening and The Mind Like Fire Unbound, the latter being an exploration of the use of fire imagery in early Buddhist literature. Really fascinating stuff. I find his writing to be both accessible (unlike a lot of over-mystified Buddhist lit) and intellectually engaging.

A lot of Buddhism is quite self-evident. Impermanence (anicca) is logical, especially to an old fart like me. My body and my world are burning and crumbling before my eyes, and my mortality towers before me now. The notion of selflessness (anatta) makes sense too: I am a temporary assembly of pieces, imagining itself to be a monolithic whole, and hoping that the monolithic wholeness will enjoy some kind of mystic permanence after the pieces have fallen apart. (DeGraff addresses the interesting question of whether Buddha intended us to regard anatta as a metaphysical truth or as a teaching aid to help us attain the goal of nibbana.)

As an old fart, getting older all the time, I am of course keenly interested in the question of what lies beyond. On this point Buddha was notoriously murky; I can find only one translation of one conversation where he addressed the question straightforwardly. The Buddha describes a life-to-life continuity that I think I could be happy with, if it's for real.

DeGraff offers his own take on the matter: ...one of the important stages of meditation is when you discover within the mind a knowing core that does not die at the death of the body. If you can reach this point in your meditation, then death poses no problem at all. That's great for those who can attain such levels of meditation, but I doubt I'll ever get there myself. DeGraff and other writers variously refer to this as the Deathless or the Unconditioned, by contrast to the "conditioned things" that suffer impermanence and deterioration, like this old body of mine.

But going back to the rather fascinating essay that I first mentioned -- here DeGraff discusses the plight of Buddhist practice in Thai society. While it's a nominally profoundly Buddhist country, there are societal forces there that work to limit the accomplishments of innovators in meditation. An interesting read, check it out. And imagine a time and place in human history where the very best of human ingenuity went not into computers or electronics or software, but into the study and training of the human mind. I first got a glimpse of this myself at a weekend retreat at Kripalu, a yoga center here in Massachusetts.

Here in Massachusetts we are in the midst of an election for the state governor. One candidate, Carla Howell, is running as a libertarian. We have had four or five candidate debates lately, of which I believe Miss Howell has participated in two. I watched one of them.

I am of generally libertarian inclinations myself, and even have a Carla Howell bumper sticker on my car. But I confess disappointment in her performance in the debate I watched. Regardless what question she was asked, she hammered on two or three catchphrases. She was more contentious with the other candidates than I thought necessary. I'm not sure she presented libertarianism in a favorable light. She's unlikely to win in Massachusetts but I'd like to see her use this as an opportunity to demonstrate why a reasonable thinking person would choose to be a libertarian.

Libertarianism is an intellectually defensible position. The rationale is grounded in microeconomics. When people are free to exchange goods and services as they choose, they will generally engage in an exchange only if it is beneficial to both parties. Fraud can mitigate benefit, but fraudulent people will tend to become known as such, and people will stop trading with them. Also, fraud watchdogs will emerge (like Consumer Reports). So that's the idyllic vision of the free market.

Big government mucks up the free market with taxes (a transaction that is not freely chosen by all concerned) and by restricting peoples' freedoms to engage in other transactions. The premise of big government is that strangers can spend your money better than you can. Libertarians believe that everybody is best off if each person makes his or her own decisions.

Carla Howell wants to eliminate the state income tax and greatly reduce the size and complexity of the state government. Some people fear that the free market only works for the wealthy - that without a big state government their kids won't be able to go to school and they won't get the medical help they need. Miss Howell needs to take a little time off from repeating her two or three slogans, and demonstrate to people that government functions can safely be privatized without plunging the poor into a Dickensian nightmare.

Do we have any evidence one way or the other? Is there a model for Massachusetts with Carla Howell as governor? The closest I can find is Jesse Ventura, the governor of Minnesota. Libertarians feel that he falls short of being a REAL libertarian, but he did look for opportunities to shrink taxes and government, as Miss Howell would. And Minnesota is not worse off for his governorship.

I lost my job in March (which is OK because it was sucking pretty hard) and got a new job in late July. The work is interesting but the schedules are a bit too hectic for my taste, and there's a lot to learn.

I have always had a mental block with CVS. Now I actually understand why: there are no books, very little good documentation, and whatever people may tell you, CVS really does have some non-trivial complexities to it. So I had always been one of these people who could never quite figure out what's going on at Sourceforge. But now that I'm in a culture of heavy CVS users, and I'm connected to the oral tradition, I'm finding that I really admire CVS and cvsweb.

At one place I worked, there was a very good source code repository system that was also connected to the bug log in a rather elegant way, so that if you did a check-in with a comment that it fixed a bug, the bug log was automatically updated to reflect that. I don't know if it's possible to connect CVS to a bug log in that way.

I've set up a CVS server at home, and thrown several stupid little projects on there, instead of dumping them on alt.sources all the time. Though I gotta say, the benefit of alt.sources is that if my machine crashes, they're still there on Google. Maybe I should adopt a reasonable backup policy.

I stopped into our neighborhood Mexican place last night to pick up some chow. It's a beautiful authentic little place that, if you've ever visited Mexico or the Caribbean, looks like you've just stepped a thousand miles south. Very small, a counter but no tables, mostly take-out, but the food is fantastic. I chatted a bit with the owner, asking about some new convenience-store stuff that had appeared. I was concerned that this perhaps signaled a bout of misfortune. He said he'd picked it up from a convenience store that closed a couple doors up the road, but didn't like the fact it was all junk food and his kitchen prepares only healthy stuff. He said that after some nearby layoffs in the wake of September 11th, the lunch crowd is way down and he's in pretty tough shape. I've decided to give an ad for him in my Slashdot sig, because I really don't want him to go out of business. Being it's Slashdot and I don't like spam any more than anybody else, I wanted to make the ad tasteful, so it just gives GPS coordinates (42.3243 N 71.3994 W). Enough to find the place, a momentary amusement for anybody of nerdly inclinations, but not too in-your-face. If you're lazy, just look here.

People have often talked about supporting their own local economy in the context of helping the economy overall. There are even folks who like the idea of creating a local currency. I think these are good ideas.

The recession is like a bunch of dominoes. Each domino has continuous inputs and internal state variables (orientation and momentum), and a discrete output (falling over), so each domino amplifies the pervasive phenomenon of falling over. A company's discrete output is the decision to lay people off. So there's a thing here of amplifying the bad karma and passing it along to others. One preventive measure would be to avoid needing to pass along bad karma: a company with better financials can sustain more troublesome inputs before it is forced to lay people off. In the domain of human relations, some people can take a lot more crap than others before snapping at somebody else. So this amounts to good management.

Maybe supporting the local economy is a form of good management? Maybe a local currency can better represent values that are cherished locally but dissed by the wider economy? Maybe it doesn't matter where the money goes, as long as it keeps moving around? Maybe keeping the money local prevents it getting sucked into some value-sink in Washington or Wall Street?

Supposing I can absorb abuse for a longer time before passing along bad karma, this may reduce the net intensity of bad karma but it lengthens its total lifetime. In a perfect world one could hope to reduce both the intensity and the total lifetime of bad karma. This reminds me of an interesting result from control theory: if there is any frequency for which the system's gain is exactly -1, you end up with instability, or persistent oscillations. This is called the Bode stability criterion. Here's another link.