As noted elsewhere here, I grew up in Pittsburgh, Pennsylvania. Back
in February 2001 I got to witness Pittsburgh's Three Rivers
Stadium demolition. My dad brought our old 1980's video camera to
film it, and afterwards we dumped the recording to the computer. And
so I present another low-quality video,
I put this up on YouTube in September 2006, and as of this writing it
has gotten about 28,000 views. Now that I finally put it here, it's
clearly available under any of the licenses at the bottom of this
page.
We were
standing nearly underneath the Fort Pitt Bridge (seen at the top
of the video) facing directly north, next to some railroad tracks. You
can see all three rivers: Ohio river to the left, Monongahela river to
the right, and the Allegheny in the top middle behind the Point.
That thick dust cloud you see at the end rose up and engulfed the
whole city, overtaking us as we headed back to the car. So I got a
little bit of history in my lungs. If you're some distant-future
archaeologist reading this maybe you can retrieve some particles from
my decomposed rib cage. Put them in a museum or something.
First, let me note that I don't watch television. At least not in the
sense of sitting on the couch, turning it on, and flipping through the
stations. I can't stand the compressed audio, the constant, loud
commercial interruptions, and general lack of control over my
viewing. VCRs, and more recently PVRs, have mitigated these last two
points, but not enough to grab my interest.
The way I see it, there are four ways to access television. Here is
the matrix,
For an "acceptable" situation we have cost-free television, but with
advertising, in broadcast and streaming television. And in the
opposite "acceptable" situation we have ad-free television, but with a
monthly fee, in premium television. I think these two are acceptable
compromises. Someone else can foot the bill, or you can foot the bill.
In a few cases, such as viewer-supported television like PBS, it's
both cost-free and ad-free. This is pretty nice. You can have your
cake and eat it too.
However, most television is only legitimately available in the
worst case situation! Not only do you have to pay to access it, but
one-third of it is annoying, unwanted advertising. This is awful, and
it is one reason why I choose not to participate.
Luckily, there is another "best case" option which provides quick
access to most television shows of the world: peer-to-peer
file-sharing. Unfortunately, it doesn't include live television, and
it's usually not quite legal. We have the technology to distribute
large amounts of data to huge numbers of people at practically no
cost, but a bunch of old, out-of-date laws stand in the way. It's a
shame. I think this
quote by "muuh-gnu" sums it up well,
We have 2009. Everybody and their dog has a computer, which is
designed to copy stuff. Also we have broadband which is, again,
designed to ... move stuff around the world. So is what you're
actually pointlessly advocating is that we collectively should
... actually what? Abstain from using a common technology in
order to make absurdly archaic 50's business models of
"manufacturing and selling single copies" viable in day and age
when everybody can manufacture and distribute those copies
themselves?
It's a good thing some bad laws don't get in the way of progress
too much.
This was almost 6 years ago now. In my freshman year of college, three
of us (Matt Stine and Matt Takach) designed and assembled a dry ice
powered potato gun. We got the idea for using dry ice after purchasing
some from the famed
Penn State Creamery. They sold it for 50 cents per pound, no
questions asked. The purpose was for keeping ice cream cold over a
long car trip, but they'd sell it to you even if you didn't buy ice
cream.
I don't recommend doing this yourself unless you are going to
take extreme caution. Like, more caution than we did. We weren't too
careful ourselves and were really lucky no one got hurt. The dry ice
"bombs" can be very powerful, enough to shatter PVC tubing. We did
bring safety glasses with us (but they went mostly unused). We also
did this in cold weather, which made things a bit safer.
On to the details, here is a diagram I drew up at the time,
It's just glued PVC tubes and a nail. The bottom of the "blast
chamber" had a screw-on cap, which kept getting blown to
smithereens. We bought several of those. The original plan also had
some wires, connected to some kind of high-resistance wire, so we
could control when the gun would fire. That didn't work out.
The "power cell" was a soda bottle with water and dry ice in it. Some
brands worked better than others. We had to smash the dry ice into
little pieces to get them in the bottle. Dry ice goes in first, then
the water, then the cap goes on. After that it's a ticking time bomb,
and you want to load it into the gun ASAP. In warm weather you have,
maybe, a few seconds. In cold weather it could be 30 minutes.
Yeah, you don't want that in your hand when it explodes.
Once the bottle explodes, there is a lot of pressure behind that
potato, so it gets quickly pushed down and out of the barrel. As I
said, in that cold weather this could take about 30 minutes. In the
video above we were adding warm water to speed up the process.
When we fired a golf ball out of the gun straight up in the air, it
took about 10 seconds to hit the ground. This put it at maybe 50 m/s
(110 mph) barrel exit speed. When launching into the field, we found
the potatoes between 150 and 250 meters.
At night we stuck glow sticks in the potatoes so we could watch their
entire trajectory. Pretty cool.
Some campus "security" person stopped us on our way home, since
carrying a muddy pipe looks suspicious. We told her it was just a
potato "cannon", which she told us "wasn't allowed on campus" (yeah,
yeah). That's time to just walk away.
Here are some pictures of the construction, and my excessive beard,
What stands out for me is that the patterns can easily be represented
as a S-expression. We represent substitutions with symbols, literals
with strings, and groups with lists. For example, this pattern,
s(ith|<'C>)V
can be represented in code as,
(s ("ith" ("'" C)) V)
I want a function I can apply to this to generate a name. First, I set
up an association list with symbols and its replacements,
(defvarnamegen-subs
'((s ach ack ad age ald ale an ang ar ard as ash at ath augh
aw ban bel bur cer cha che dan dar del den dra dyn
ech eld elm em en end eng enth er ess est et gar gha
hat hin hon ia ight ild im ina ine ing ir is iss it
kal kel kim kin ler lor lye mor mos nal ny nys old om
on or orm os ough per pol qua que rad rak ran ray ril
ris rod roth ryn sam say ser shy skel sul tai tan tas
ther tia tin ton tor tur um und unt urn usk ust ver
ves vor war wor yer)
(v a e i o u y)
...
(d elch idiot ob og ok olph olt omph ong onk oo oob oof oog
ook ooz org ork orm oron ub uck ug ulf ult um umb ump umph
un unb ung unk unph unt uzz))
"Substitutions for the name generator.")
Since we will need this in a couple places, make a function to
randomly select an element from a list,
(defunrandth (lst)
"Select random element from the given list."
(nth (random (length lst)) lst))
A function for replacing a symbol,
(defunnamegen-select (sym)
"Select a replacement for the given symbol."
(if (null (assoc sym namegen-subs))
(throw 'bad-symbol
(concat "Invalid substitution symbol: " (format "%s" sym)))
(symbol-name (randth (cdr (assoc sym namegen-subs))))))
And finally, the generator. Find a string, pass it through, find a
symbol, substitute it, find a list, pick one element and recurse on
it.
(defunnamegen (sexp)
"Generate a name from the given sexp generator."
(cond
((null sexp) "")
((stringp sexp) sexp)
((symbolp sexp) (namegen-select sexp))
((listp sexp)
(concat (if (listp (car sexp)) (namegen (randth (car sexp)))
(namegen (car sexp)))
(namegen (cdr sexp))))))
That's it! We can apply it to the expression above,
(namegen '(s ("ith" ("'" C)) V))
-> "rynithi"
But that's really the easy part. The hard part would be converting the
original pattern into the S-expression, which I don't plan on doing
right now.
Something else to note: this is thousands of times faster than the
Perl version I wrote earlier.
I threw the code in with the rest of my name generation code
(namegen.el),
First, let me note that I don't watch television. At least not in the
sense of sitting on the couch, turning it on, and flipping through the
stations. I can't stand the compressed audio, the constant, loud
commercial interruptions, and general lack of control over my
viewing. VCRs, and more recently PVRs, have mitigated these last two
points, but not enough to grab my interest.
