IP over Laser
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.
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
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
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.
Saw that "What the Bleep" movie
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
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.
Dude, where's my 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
- 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.
How do we know there's no afterlife?
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,
testing, as part of a course on detection
and estimation. I also learned about the scientific
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
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
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
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
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.
Thanissaro Bhikkhu, other stuff
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
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
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 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
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.
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.