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Diffstat (limited to 'misc')
| -rw-r--r-- | misc/SCUBA.page | 89 | ||||
| -rw-r--r-- | misc/artists.page | 7 | ||||
| -rw-r--r-- | misc/newcomb-paradox.page | 69 |
3 files changed, 165 insertions, 0 deletions
diff --git a/misc/SCUBA.page b/misc/SCUBA.page new file mode 100644 index 0000000..6e15c52 --- /dev/null +++ b/misc/SCUBA.page @@ -0,0 +1,89 @@ +--- +format: rst +categories: +toc: no +... + +============ +SCUBA Diving +============ +--------------------------------------------- +Self Contained Underwater Breathing Apparatus +--------------------------------------------- + +SCUBA stands for "Self-Contained Underwater Breathing Apparatus". +One of the primary organization regulating recreational SCUBA diving is +PADI (the Professional Association of Diving Instructors). + +Equipment +--------- + +:BCD: The buoyancy control device is basically an inflatable live vest + that you can inflate using the regulator (or by mouth) to control + your buoyancy. Your buoyancy changes as you use up air (tank gets + lighter for same volume displaced), inhale/exhale, swim in water + of different temperature or salinity, or change depth: increased + pressure compresses any flexible air pockets, including the BCD + itself, neoprene foam, or a dry-suit. + Most BCDs have their own pressure hoses coming from the first stage + regulator that supply air. + Sometimes there is only one vent valve, which has to be at the + highest orientation or air will not vent out of the bladders. +:Tank: Most tanks are made of steel or aluminum and can store compressed + air of up to 3000psi. They are stored at pressure to prevent moisture + from leaking in. There is a valve built into the tank itself that + usually gets taken apart and repaired every two years. Tanks + can last for decades even with heavy use; they are pressure tested + for fatigue and leaks. +:Regulator: The first-stage regulator is connected to the tank and steps + the pressure down to about 250psi above the surrounding/ambient + pressure. Hoses carry air at this mid-level pressure to the second + stage regulator/mouthpiece, which steps the pressure down to + about what is in your lungs. Depending on the regulator they can + be stiff (you have to suck a bit to get air, but then it rushes + in with force) or very natural feeling (air comes very smoothly + on inhalation and doesn't press into your lungs). +:Alternate: These days almost everybody carries a second regulator mouthpiece + for emergencies. These are always on and ready to breath from, + but usually stiffer so they don't free-flow as often. +:Dive Computer: + A dive computer monitors time and depth to give you an accurate picture + of how much excess nitrogen is in a diver's bloodstream. By + continuously integrating they usually "give more time at depth" than + hand calculations using tables (which err towards safety). +:Dry Suit: A dry suit is a sealed and air tight, keeping the diver's skin dry. + Extra insulation is needed to give warmth underneath. Some dry + suits are made of compressed neoprene. + A dry suit has to be constantly adjusted with tank air just like + the BCD to maintain inflation and buoyancy. +:Wet Suit: Wet suits work on the principle of holding water against the skin: + a diver's body warms this water and stays cozy as long as water + flow is restricted enough. Even little bit too much flow through + wrist or ankle openings can be very cold. + + +Depths +------ +A PADI Open Water Diving course gives a recommended limit of 20m/60ft. +A "deep dive adventure course" gives a recommended limit of 30m/100ft, +and additional experience gives a limit of 40m/130ft. + +With careful decompression stops and enriched compressed air (higher oxygen +content) it's possible to reach depths of hundreds of meters. Sometimes +commercial divers will dive for many hours using surface supplied air, +then live at the surface in a compression chamber overnight between dives +to stay at the same pressure [*]_. + +History +------- +I'm pretty sure `Jacques Cousteau`_ invented the aqualung, which is the basis +for modern diving, but I'll have to check. + +.. _Jacques Cousteau: /k/jacquescousteau/ + +Flying +------ +After a regular no-decompression dive, wait at least 12 +hours before flying (or going to high altitude, eg over 300m). + +.. [*] Need a citation, heard this word of mouth diff --git a/misc/artists.page b/misc/artists.page new file mode 100644 index 0000000..ac1cc86 --- /dev/null +++ b/misc/artists.page @@ -0,0 +1,7 @@ +Artists +======= + +* Kay Sage (1898-1963), American Surrealist Painter +* Yves Tanguy (1900-1955), French Surrealist Painter +* Hans Bellmer (1902-1975), French. "Die Puppe" series (dolls) +* Francis Picabia (1879-1953) French Painter diff --git a/misc/newcomb-paradox.page b/misc/newcomb-paradox.page new file mode 100644 index 0000000..58ace89 --- /dev/null +++ b/misc/newcomb-paradox.page @@ -0,0 +1,69 @@ +--- +format: rst +toc: no +... +================== +Newcomb's Dialemma +================== + +Newcomb's paradox was thought up by a researcher named Newcomb; it was first +explored and written up by Robert Nozick in the 1969 paper +"Newcomb's Problem and Two principles of Choice". + +The Situation +------------- +As narrated by an all knowing "predictor":: + + I am going to give you a choice. It is important to know that I really + pretty much know what you are going to do. I have been watching their whole + life and am additionally an immortal being; i've been doing this a long + time and always guess correctly. It's also important to know that I am + unbiased and don't care which decision you make, I have nothing to gain + either way. + + Here are two boxes: a large and a small. The small has a 10 shekel coin + in it (show everybody). The large one may or may not have a thousand + shekels in it; you don't know. Your choice is to either take only the + large box or to take both the large and small boxes. The twist is that + I already knew which decision you will make and decided whether or not + to put the $1000 in the large box or not based on that knowledge. + If I knew you would "two box", then I left the large box empty. If I knew + you would "one box" then I filled it. + +Dominance Mindset +----------------- +Regardless of what decision was made previously, and whether or not there +is anything in the large box, the person is better off taking both boxes; +either they will get just $10 (better than none) or $1010 (better +than $1000). So two-box. + +Trusting Mindset +---------------- +The predictor is pretty much always right so we can just ignore the +possibility that they are wrong. In this case, choosing to one-box +implies that the Predictor knew you would and you get $1000; +choosing to two-box implies that the predictor knew you would and you +only get $10. + +The predictor doesn't even have to be perfectly accurate; say they are +90%: +If you one-box, your expected value is $900. +If you two-box, your expected value is $110. + +Discussion +---------- +It's disputed whether this is a paradox, and there are many deeper arguments +that I don't have time to go into here. Ultimately, I am a one-boxer +though this is something of a minority position. + +Afterword +--------- +The person who taught me this paradox, Professor Augustin Rayo, a +two-boxer, then had this to add. He was talking with his one-boxing friend +and accused her of letting irrationality undermine her logic: she is so +optimistic that if a statement S is unprovable, but it would be nicer if S +was true than false, then she pretens that S is proven. So basically, even +though there is no rationalization, she will accept a statement "just +because it would be nice", and this isn't how logic works. To which she +replied "but wouldn't it be nice if it was?". + |