Swap

Swap (pronounced swop)

(1) To exchange, barter, or trade, as one thing for another.

(2) To substitute (one thing) for another (sometimes used in the forms swap-out & swap-in).

(3) To make an exchange.

(4) In finance, the verbal shorthand for a number of transactions (credit default swaps, currency swaps etc).

(5) In computer programming, exchanging two variables in the memory of a computer

(6) In computer operating systems, as swap partition, a partition of the physical data storage media used for paging to augment random access memory (RAM).

(7) In instrumentation as the acronym SWAP (Sun Watcher using Active Pixel System Detector and Image Processing), a space instrument used on solar satellites.

(8) In instrumentation as the acronym SWAP (Solar Wind At Pluto), a space instrument used in the observation of Pluto (which should still be a planet).

(9) In international development as the acronym SWAp (Sector-Wide Approach), a paradigm in the sector.

(10) In Cambridge University slang, a social meal at a restaurant between two university societies, usually involving drinking and banter; commonly associated with fining and pennying; the crewdate is the Oxford University equivalent.

(11) As swapling, an infant or child secretly exchanged for another; a changeling.

Circa 1200: From the Middle English swappen (to swap (the original meeting was “to hurl, to strike, strike hands (in bargaining the terms of an exchange)”) and cognate with the dialectal German schwappen (to slosh, slop, to clap, box (the ears)).  The origin is murky but it was probably from the Old English swappian, a secondary form of swāpan (to swoop) and may be compared with the Middle English swippen (to strike, hit), from the Old English swipian (to scourge, strike, beat, lash) which was in some way connected with the Old Norse svipa (to swoop, flash, whip, look after, look around).  Acronym finder has 37 entries for SWAP, the most obviously useful including (1) Solution Without A Problem, (2) Space, Weight And Power, (3) Shared Wireless Access Protocol, (4) Severe Weather Avoidance Protocol, (5) Sheriffs' Work Alternative Program, (6) Solar Wind Analyzer around Pluto & Stewart Warner Array Program (Stewart Warner a famous name in gauges and instrumentation) while some truly are niche such as Special Whatchamcallit Affectionately Pinned (used by Girl Scouts).  The alternative spelling, restricted mostly to the UK, is swop.  The noun swappist (used in a surprising number of sub-cultures) is non-standard while the noun swapsies provided the model for the later funsies (just for fun (ie not serious; not for financial gain)).  Swap is a noun & verb, swapper & swapling are nouns, swapped is a verb, swapping is a verb & adjective; the noun plural is swaps.

The seemingly strange etymological path from Middle English swappen ("to hurl" or "to strike") to the modern meaning of “swap” is thought to be an allusion to striking hands together when making an exchange, the handshake sealing the deal (ie the swap) as it were; the evolution of the word thus imitative of the sound of hitting or slapping.  The origin of swappen was the Middle English swippen (to strike, hit), from the Old English swipian (to scourge, strike, beat, lash), from the Old English swappian, a secondary form of the Old English swāpan (to swoop), from the Old Norse svipa (to swoop, flash, whip, look after, look around) which begat also swipe.  The verb (circa 1200) was the first form in the sense of "to strike, strike the hands together.  The sense of "to exchange, barter, trade" dates from the 1590s, the noun in this sense first recorded in the 1620s. Although swap-meets are an ancient institution of the barter economy known to many cultures and pre-dating antiquity, the term “swap-meet” seems not to have existed prior to 1968 when added to American English.

Bill Clinton (b 1946; US president 1993-2001) leaving the Martha's Vineyard Annual Swap Meet.

In 1890, the US Board on Geographic Names (BGN) introduced a policy avoiding the use of apostrophes in the possessive form in place names, the intent being: (1) a standardization convention to remove confusion, (2) to simplify the printing of maps by ensuring there were fewer clashes with special characters and (3) to remove another source of imaginative interpretation by lawyers.  An additional benefit was realized when computer databases began to be created and, especially in the early post-war years, many problems in indexing and formatting were avoided by restricting entries to letters & numbers.  The BGN does make the odd exception in the case of places of historical significance and Martha's Vineyard was one of the few places to emerge with apostrophe intact.

Swap files and operating systems

A swap file (known also as virtual memory) is a file (with special attributes) stored on a HDD (hard disk drive) or SSD (solid state drive) where data is written if the physical random access memory (RAM) available becomes insufficient for the stable functioning of the operating system.  RAM is preferable for operations because, being essentially static electricity, it is so much faster than even the fastest forms of HDD or SSD.  Older versions of Microsoft Windows used pagefile.sys as a page file but since Windows 10, the function has been split into pagefile.sys and swapfile.sys which by default reside in the root of the system (c:\) drive and, for good reason, are hidden from the user.  Pagefile.sys stores data from installed (third-party) applications while swapfile.sys handles data from Windows and applications installed from the Microsoft Store.  In years gone by, there were advantages to be had in terms of speed and storage by tweaking swapfile settings (the size and the volume on which it sat) and some disabled it entirely if they had a surfeit of RAM.  Those with long memories will recall even a time when Windows permitted a choice between a temporary and permanent swap file and there were reasons why one could be preferable to the other.  However, with modern versions of Windows, it shouldn’t be disabled because many applications require it to exist and without one, simply won’t start.  For what most people do most of the time, it’s best to ignore the settings and just allow the operating system to set the configuration, even though on a machine with much RAM, the swap file is seldom used.

However, for nerds and megalomaniacs, it remains possible to tinker although, unless simulating one’s own thermonuclear explosions or modelling the global climate, few are likely to notice much difference.  It needs to be done with caution because if the swap file is too big then system will slow because RAM is often ignored whereas if it is too small, there comes a point at which that becomes functionally the same as disabling the feature.  Computer magazines used to publish ways to calculate the ideal size, either by (1) a calculation based on the size of the hard drive and installed RAM and (2), a calculation which involved assessing a typical use of physical RAM but most now concede that on modern PCs (ie 8 or more GB RAM), it’s best to allow the operating system handle the allocation.  Users can still experiment but Microsoft cautions the swap file size should never be set to more than twice the size of physical RAM; instability is assured.  There are different rules and parameters for Windows Server; because of the way Windows is written, there are special settings and system administrators have to make allowances so in event of system crashes, there’s sufficient space for dump files which can reveal much.  For those who don’t, in another context, wish anything to be revealed, page files can be encrypted although, while secure, that does impose some overhead on disk IO (input/output).

Under Linux, the golden rule long was a swap size should be double the installed RAM but that hardly applies to modern machines, indeed, on some boxes, that may no longer even be possible.  Many Linux distributors are actually silent on the matter, perhaps reflecting the not improbable assumption their users are nerdier than the Windows crowd and will likely work things out themselves but some do provide guidance.

(1) Red Hat suggest a swap size of 20% of RAM for modern systems (which they define as 4GB or more RAM).

(2) CentOS suggests (2a) twice the size of RAM if RAM is less than 2 GB or (2b) size of RAM + 2 GB if RAM size is greater than 2 GB.

(3) Ubuntu notes (3a) if hibernation is used, a swap of the size of RAM plus the square root of the RAM size is necessary, (3b), if RAM is less than 1 GB, swap size should be at least the size of RAM and at most double the size of RAM & (3c) if RAM is more than 1 GB, swap size should be at least equal to the square root of the RAM size and at most double the size of RAM.

In their dark hearts, all the Unix guys really long for the world of the early mainframes where the distinctions between memory and storage space really didn’t exist and for most users, the same thing applies under Linux: usually it’s best just to let the system decide.

Swap Films

Swap Movie DVD twin-packs: The Parent Trap and Freaky Friday.

“Swap” films are a common trope in commercial cinema, done so often one wonders if the screen-writers might not be ungrateful were the scripts for such things handed to AI (artificial intelligence) bots; it must be a thankless task to try to come up with some original take on the concept.  Probably, every twenty-odd years, scripts could be recycled and few except pedantic critics would notice.  Swap films with the Freaky Friday title have appeared four times since 1976 (another is threatened) and at least two others have been made which follow variations of the plotline.  The Parent Trap franchise is built around a different sort of swap, one which doesn’t depend on any aspect of the supernatural.  Using the title there have been two feature-length films and three made television features with Disney said to have another release in the pipeline.  This swap theme (two characters changing places for some purpose) has been used in fiction (in print and on screen) literally dozens of times in genres as varied as satire, rom-coms (romantic comedy), fantasy and horror.

Lava

Lava (pronounced lah-vuh or lav-uh)

(1) The molten, fluid rock that issues from a volcano or volcanic vent (sometimes accumulating, occasionally permanently) in a volcano’s “lava lake”.

(2) The rock formed when this solidifies, occurring in many varieties differing greatly in structure and constitution.

(3) In fashion, as “lava dress” (sometimes volcano dress), a long, flowing gown, classically in orange and black fabric, styled to recall a vertiginous lava flow.

(4) A shade of red which tends to orange, recalling the color of red-hot, molten lava.

(5) As Lava Lamp, the trademarked name of a electric decorative lamp made of a transparent, (usually tapered) cylinder containing a liquid in which a colored wax (or wax-like substance) is stimulated by the heat of the light bulb to change into randomly separating, seemingly luminous shapes which constantly rise and descend.

1740–1750: From the Italian lava (molten rock issuing from a volcano), from the Neapolitan or Calabrian dialectal lava (avalanche, torrent or stream; downpour overflowing the streets).  The original use in Italian was to describe flash flood rivulets after downpours and only later to the streams of molten rock from Mount Vesuvius.  The once commonly supposed link with the Latin lavāre (to wash) (from the primitive Indo-European root leue- (to wash) was based on the idea of “a liquid flowing” but is now thought one of those creations of the medieval imagination and it’s just as unlikely there’s was any relationship with the Arabic لابة‎ (lāba) (black volcanic rock).  Lava is also wholly unrelated to larva (an early stage of growth for some insects and amphibians) which was from the Latin larva (ghost-like, masked) which may have been from the Etruscan Lār (Etruscan praenomen; titulary god) which appeared usually as Lares (guardian deities).  The alternative etymology is from the Latin labes (sliding down, falling), which influenced lābī (to slide, fall or slip) (a labina an “avalanche or landslide”).  The only adjective in modern use is lavalike (or lava-like).  The old adjectives lavatic (1805), lavic (1822) & laval (1883) all fell into disuse by the twentieth century (although their occasional revival in the technical literature would not be unsurprising) and lavaesque seems never to have been coined.  The palindromic Laval did endure in France as both a locality name and surname and is remembered because of Pierre Laval (1883–1945), prime minister of France 1931-1932, 1935-1936 & de facto prime minister in the Vichy Government 1942-1944, executed by a French firing squad in 1945.  Lava is a noun and the obsolete lavatic, lavic & lavalike were adjectives; the noun plural is lavas.

Lindsay Lohan in Pucci triangle lava-print bikini, The Bahamas, May 2007.  Pucci are noted for the shapes and colors printed on their fabric but their minimalist website is worth visiting as a reminder of how good Italian design can be.

What Pucci did for their "Lava" range was take the shapes and curves assumed by a lava flow and render it with colors sometimes never seen in volcanology.  The terms lava and magma (from the Ancient Greek μάγμα (mágma) (paste)) are sometimes used interchangeably but to geologists and volcanologists the distinction is that Magma is molten rock which exists beneath a planet’s surface and become lava only when it flows from a volcano or volcanic vent.  Magma thus does not always become lava, sometimes cooling and solidifying as rock beneath the surface and sometimes collecting in a magma chamber.  A magma chamber differs from a lava lake in that the pleasingly alliterative latter describes the (usually large) large pool of molten lava that forms in a volcanic crater (although volcanologists do use the term also of lava which “sticks” to a volcano’s surface and doesn’t flow further.  They also in some cases call the extrusive igneous rock formed when it hardens and cools “lava” although this is not in general use, laypeople associating both “magma” and “lava” with the material in its molten state.

1976 Lincoln Continental Mark IV, Pucci Edition (left) and the opera windows of the designer series Mark IVs (right), into which was etched the house's name.  The other designers were Bill Blass, Cartier & Givenchy and presumably something of an owner's character could be determined by their choice.  The ownership of the Mark IVs was overwhelmingly male and if a young lady heard one suggest she "come and see my etching", on the basis of what she saw on the opera window, she could elect to proceed or decline, fashion choices as good a criterion as any in such decisions. 

Although there was little else in the cars which suggested much influence from Italy, Pucci was one of four fashion houses chosen by the Ford Motor Company (FoMoCo) to provide “touches” for “designer” editions of the 1976 Lincoln Continental Mark IV and the Pucci package (in “vintage burgendy with a loose pillow velvety burgendy velour interior”) added US$2000 to the MRP (manufacturer’s recommended price) of US$11,060.  The creation of the designer editions was an attempt to stimulate demand because the sales numbers in 1974-1975 had proved disappointing, something attributed both the downturn in the economy and the Mark IV having been on the market since late 1971, the only changes since the addition of (1) emission controls which reduced power & impaired drivability and (2) huge, heavy, impact resistant bumpers, neither of which much engaged potential buyers.  The economy improved somewhat in 1976 but the “touches” of the fashion houses must have helped because after sinking to 47,145 in 1975, sales the next year for the Mark IV’s final season rebounded to 56,110.  The designer editions accounted for almost a third of that volume, FoMoCo so pleased the contracts were renewed and those who want a classic Pucci Lincoln can choose a Mark IV (1976), Mark V (1977-1979) or Mark VI (1980-1983), the detailing changing with each version although the Pucci name was always etched into the opera windows on the C-pillar.  Now part of the LVMH (Moët Hennessy Louis Vuitton) multinational conglomerate, in their corporate history there seems to be no mention of Pucci’s involvement with Lincoln’s “land yachts” but it must at the time have seemed a good idea.

Lava flowing over snow and ice, demonstrating the “Leidenfrost effect”.  The Leidenfrost effect (known also as “film boiling”) describes the phenomenon in which a liquid, close to a solid surface of another body that is significantly hotter than the liquid's boiling point, produces an insulating vapor layer that prevents liquid rapidly from boiling.  This happens because of “repulsive force”; droplets hovering over the surface, rather than making physical contact.  In a charming linguistic coincidence, the “frost” element in the word is not a reference to frozen water but from the name of German physician Johann Gottlob Leidenfrost (1715—1794), who first documented the phenomenon in De aquae communes nonnullis qualitatibus tractatus (Tract about some qualities of common water, 1756).  The son of a preacher, Dr Leidenfrost began his academic career studying theology before switching to medicine.  Until modernity overtook the twentieth century, the church was a source of many scientists, not all of whom abandoned their faith.  The German Leiden can be both a noun and verb; as a verb (leiden) it means “to endure” or “to suffer” but in idiomatic use it’s used in that sense also to mean “to tolerate” although most often in the negative (such as “Ich kann ihn nicht leiden” (I can't stand him.))  As a noun (das Leiden), it means “pain”, “suffering” or “affliction”.  The German Frost means “frost or freezing temperatures”.  Thus the surface analysis of the surname “Leidenfrost” is “enduring frost” or “suffering from frost” and onomasticians (or onomatologists, those who study surnames, a sub-branch of anthroponymy (the study of proper names) suspect the origin was something to do with those who live in cold or icy places although it may also be toponymic, referring to individuals from specific locations in Germany Leidenfrost in Thuringia or Leidenfrosten in Saxony-Anhalt.

Lava lake, Mount Erebus, Antarctica.  Some 60 m (200 feet) in diameter, it sits within a small pit crater within the post-caldera summit and is phonolite in composition.  It may or may not remain a permanent feature.

The rock formations created by cooled magma at Mount Erebus proved especially interesting to those researching the history of the Earth’s magnetic field.  Geophysicist Dr Catherine Constable (b 1958) was studying the data used to refine a model explaining the mechanism of the earth’s occasional magnetic field reverses (from the familiar north & south polarity to the reverse where they swap) and found lava to be a substance keeping a perfect recorder of the field.  All magmas contain enough iron-rich minerals to detect the field and these align themselves toward the field as the lava freezes. As a result, the magnetic field at that moment is recorded: set in time and set in stone.  Over geological time, quite what the frequency (or the rapidity) of the shift isn’t clear and while studies suggest historically there’s be a swap every few hundred thousand years, it’s been almost a million years since the last so while one “might” be (over)due, Dr Constable says there’s no available evidence one is in progress or even imminent.

Catriona Gray (b 1994; Miss Universe 2018) in lava dress by Filipino designer Mak Tumang (b 1986) which used a image of lava flowing down Mayon Volcano, rendered in Swarovski crystals, Bangkok’s Impact Arena, Thailand, December 2018 (left) and lava flow on Tungurahua volcano, Huambalo, Ecuador (right).

Catriona Gray on the catwalk, lava flowing.

Lava cup-cakes

Lava cakes can pay tributes to volcanologists in different ways.  They can feature a magna chamber which, upon slicing can feed a lava flow or they can formed with an exposed crater in which sits a lava lake.  Professional chefs can produce the effects with room-temperature “lava” but usually these are for display and the cakes work best with hot, melted chocolate and obsessives use a variety of ingredients (peanut butter, raspberries, orange colored icing etc) to attempt to emulate the variegated colors of the real stuff.  They work best with dark chocolate but sweeter types can be used (or a blend).  Lava cakes can be made at larger scales but the laws of physics (both thermal and structural) mean full-sized constructions can be challenging (and messy) so most produce lava cup-cakes.  Because, in a sense, lava cakes are a kind of civil engineering, some very complex recipes have been created but the following will make 6-8 cup-cakes (depending on the size of the muffin tins) and it has the virtue of simplicity:

Ingredients

4 tablespoons of unsalted butter at room temperature (plus some with which to grease the muffin tray).

A third of a cup of granulated sugar (plus some to sprinkle in the muffin tray).

3 large eggs.

A third of a cup of all-purpose flour.

A quarter teaspoon of salt.

8 ounces of dark chocolate, melted (for best results, delay the melt process until ready to blend (step (8) below).

6-8 squares (from the standard blocks) of dark chocolate.

Icing (confectioners') sugar, for dusting.

Whipped cream or ice cream, for serving (optional).

Fruit for serving (optional and most choose a red or orange variety).

Instructions

(1) Preheat oven to 400°F (205°C).

(2) Grease the cups of muffin tray with butter, ensuring the coasting is light and consistent.

(3) Sprinkle some granulated sugar over the muffin tray and ensure each has buttered cup has a consistent coating.  Shake off any excess grains.

(4) Spoon some granulated sugar into each cup, swirling to make sure the cup is completely lined.

(5) Blend the butter and granulated sugar until the mix is creamy.

(6) To this mix, as the eggs, one at a time, blending them in after each addition.

(7) To this mix, beat in flour and salt (on a low speed) until combined.

(8) To this mix, add the molten chocolate, and beat until combined.  Don’t be off-put if the mix seems either more or less viscous that you might expect.

(9) Pour mix into the greased cups. Fill only to half-way.

(10) In the centre of each cup, place one of the chocolate squares.

(11) Add the remaining mix to each cup but, because the mix will expand, don’t fill higher than three-quarters.

(12) Put tray into the heated oven, baking until the middle of the cakes no longer jiggle (should be no more than 8-12 minutes and if left too long, they’ll cease to be lava cup-cakes and become chocolate cup-cakes).  Because there’s some risk of spillage, place baking paper underneath the tray.

(13) Remove tray from oven and allow it to sit for 7-8 minutes.

(14) Up turn tray on a plate or other suitable flat surface and remove cup-cakes so the conical aspect resembles volcano.

(15) Dust with the icing (confectioner's) sugar and serve with vanilla ice cream or whipped cream, adding some sort of fruit if desired.  Upon being sliced, the magma should ooze out, lava-like.

The Lava Lamp

The decorative lava lamp was invented in 1963 by Edward Craven Walker (1918-2000), a Word War II (1939-1945) RAF (Royal Air Force) pilot who was inspired by a rigged-up egg-timer he saw in a pub, the device made with oil and water in a bottle.  Oil and water being two immiscible (unable to mix) fluids, the timer worked by shaking the bottle, the egg deemed to be ready when the resulting blobs of oil had re-coagulated.  Knowing the world was well-supplied with cheap, reliable egg-timers, Craven saw little point in “making a better mousetrap” but he found the behavior of the blobs a pleasing piece of art and in his garage experimented with different fluids until he found a pleasing combination which produced just the effect he’d envisaged.  The characteristic shape of the lamp came about because the one seen in the pub used a standard cocktail shaker and the container in which Craven undertook his early research was an orange-squash bottle which was made in a similar shape; it proved ideal.

Although associated with psychedelia, as well as lurid colors (the range expanded since the introduction of LEDs), lava lamps with plain black blobs in clear fluid are available.

The first lava lamp patent (Lava Lamp is a registered trademark in some jurisdictions) was applied for in 1963 and they were first displayed in 1965.  Very popular in the early-mid 1970s, by the 1980s the fad had passed, not because of the popular association of them with stoners imagined sitting staring at one for hours while the Grateful Dead played on the turntable (endlessly on repeat) but because they’d come to be thought of as plastic kitsch.  However, they never quite went away and while there are spikes in demand (associated usually with some appearance in some prominent piece of popular culture), there is clearly a constant demand for those who just like the look while others furnish according to retro schemes or like the odd ironic piece among their conspicuous good taste.

An application of physics of thermodynamics and fluid mechanics, the lava lamps once so admired by stoned hippies work by exploiting differences in density, thermal expansion, and buoyancy within two immiscible fluids (ie they do not mix), the dynamics driven by a localized heat source and the construction is simple; in a variously shaped glass vessel, there is a wax-based compound (the “lava”, which typically is paraffin wax mixed with additives to adjust density and melting point), floating in a liquid (usually water or a water-based solution with salts or alcohols to achieve the desired density).  At the base of the vessel there is a source of light and heat which traditionally was an incandescent bulb, the heat a product of the inefficiency with which the energy was converted into light; when the bulb is switched on, the liquid becomes heated and as the wax absorbs some of this heat, it melts and thermally expands, density thereby decreasing to the point it’s slightly less dense than the surrounding liquid.  Buoyant force then causes the wax to rise through the liquid in blobs, randomness meaning tiny variations in surface tension and viscosity create infinitely different shapes of the rounded forms which cool as they move away from the heat source, meaning the wax contracts, increasing its density beyond that of the liquid, causing it to sink back toward the bottom.  Because it’s a closed system working on a continuous cycle, the heating & cooling repeats continuously and, component failure and material decay aside, in theory a lava lamp could run forever.

Kitsch at work: Lava Lamps and Random Number Generation

Some may have dismissed the Lava Lamp as "kitsch" but the movement of the blobs possesses properties which have proved useful in a way their inventor could never have anticipated.  The US-based Cloudflare is a “nuts & bolts” internet company which provides various services including content delivery, DNS (Domain Name Service), domain registration and cybersecurity; in some aspects of the internet, Cloudflare’s services underpin as many as one in five websites so when Cloudflare has a problem, the world has a problem.  For many reasons, the generation of truly random numbers is essential for encryption and other purposes but to create them continuously and at scale is a challenge.  It’s a challenge even for home decorators who want a random pattern for their tiles, their difficulty being that however a large number of tiles in two or more colors are arranged, more often than not, at least one pattern will be perceived.  That doesn’t mean the tiles are not in a random arrangement, just that people’s expectation of “randomness” is a shape with no discernible pattern whereas in something like a floor laid with tiles, in a random distribution of colors, it would be normal to see patterns; they too are a product of randomness in the same way there’s no reason why if tossing a coin ten times, it cannot all ten times fall as a head.  What interior decorators want is not necessarily randomness but a depiction of randomness as it exists in the popular imagination.

Useful kitsch: Wall of Entropy, Cloudflare, San Francisco.  Had this been in an installation in a New York gallery circa 1972, it would have been called art.  

For most purposes, computers can be good enough at generating random numbers but in the field of cryptography, they’re used to create encryption keys and the concern is that what one computer can construct, another computer might be able to deconstruct because both digital devices are working in ways which are in some ways identical.  For this reason, using a machine alone has come to be regarded as a Pseudo-Random Number Generator (PRNG) simply because they are deterministic.  A True Random Number Generator (TRNG) uses something genuinely random and unpredictable and this can be as simple as the tiny movements of the mouse in a user’s hand or elaborate as a system of lasers interacting with particles.

One of Cloudflare’s devices encapsulating unpredictability (and thus randomness) is an installation of 100 lava lamps, prominently displayed on a wall in their San Francisco office.  Dubbed Cloudflare’s “Wall of Entropy”, it uses an idea proposed as long ago as 1996 which exploited the fluid movements in an array of lava lamps being truly random; as far as is known, it remains impossible to model (and thus predict) the flow.  What Cloudflare does is every few milliseconds take a photograph of the lamps, the shifts in movement converted into numeric values.  As well as the familiar electrical mechanism, the movement of the blobs is influenced by external random events such as temperature, vibration and light, the minute variations in each creating a multiplier effect which is translated into random numbers, 16,384 bits of entropy each time.

Wall of Entropy, Cloudflare, San Francisco.

The arrangement of colors which avoids any two being together, in the horizontal or vertical, was a deliberate choice rather than randomness although, there's no reason why, had the selection truly been random, this wouldn't have been the result.  Were there an infinite number of Walls of Entropy, every combination would exist including ones which avoid color paring and ones in which the colors are clustered to the extent of perfectly matching rows, colums or sides.  What Cloudflare have done in San Francisco is make the lamps conform to the popular perception of randomness and that's fine because the colors have no (thus far observed) effect on the function.  In art and for other purposes, what's truly random is sometimes modified so it conforms to the popular idea of randomness.

Mutual & Common

Mutual (pronounced myoo-choo-uhl)

(1) Possessed, experienced, performed, etc by each of two or more with respect to the other; reciprocal.

(2) Having the same relation each toward the other.

(3) Of or relating to each of two or more; held in common; shared.

(4) In corporate law, having or pertaining to a form of corporate organization in which there are no stockholders, and in which profits, losses, expenses etc, are shared by members in proportion to the business each transacts with the company:

(5) In informal use, an entity thus structured.

1470–1480: From the Middle English mutual (reciprocally given and received (originally of feelings)), from the Old & Middle French mutuel, from the Latin mūtu(us) (mutual, reciprocal (originally “borrowed”)), the construct being mūt(āre) (to change (source of the modern mutate (ie delta, omicron and all that))) + -uus (the adjectival suffix) + the Middle French -el (from the Latin –ālis (the third-declension two-termination suffix (neuter -āle) used to form adjectives of relationship from nouns or numerals) and rendered in English as –al.  Root was the primitive Indo-European mei- (to change, go, move).  The alternative spelling mutuall is obsolete.  Derived forms used to describe ownership structures such as quasi-mutual and trans-mutual are created as required.  Mutual & mutualist are nouns & adjectives, mutuality, mutualization, mutualism & mutualness are nouns, mutualize, mutualizing & mutualized are verbs and mutually & mutualistically are adverbs; the noun plural is mutuals.

The term "mutually exclusive" is widely used (sometimes loosely) but has a precise meaning in probability theory & formal logic where it describes multiple events or propositions such that the occurrence of any one dictates the non-occurrence of the other nominated events or propositions.  The noun mutualism is used in fields as diverse as corporate law, economic theory, materials engineering, political science and several disciplines within biology (where variously it interacts with and is distinguished from symbiosis).  The phrase "mutual admiration society" is from 1851 and appears to have been coined by Henry David Thoreau (1817–1862) to describe those who habitually were in agreement with each-other and inclined to swap praise.  The "mutual fund", although the structure pre-existed the adjectival use, is from 1950 and these soon came to be known simply as “mutuals”, the word appearing sometimes even in the registered names and the best known of the type were the building societies & benevolent (or friendly) societies, the core structural element of what was the ownership being held in common by the members rather than shareholders.  The concept of the mutual structure is of interest in some jurisdictions because of the suggestion the large assets held by chapters of the Freemasons may be so owned and, with the possibility the aging membership may ultimately result in these assets being dissolved and the proceeds distributed.  If, under local legislation, the structure was found to be mutual, membership might prove unexpectedly remunerative.

The Cold War's "mutually assured destruction" (MAD) is attested from 1963 (although it wasn’t until 1966 it entered general use) and was actually a modification of the Pentagon’s 1962 term “assured destruction” which was a technical expression from US military policy circles to refer to the number of deliverable nuclear warheads in the arsenal necessary to act as a deterrent to attack.  In the public consciousness it was understood but vaguely defined until 1965 when Robert McNamara (1916–2009; US Secretary of Defense 1961-1968) appeared before the House Armed Services Committee and explained the idea was "the minimum threat necessary to assure deterrence: the capability in a retaliatory nuclear attack to exterminate not less than one third the population of the Union of Soviet Socialist Republics (USSR)”.  The “mutual” was added as the number of deployable Soviet warheads reached a critical strategic mass.  The mastery of statistical analysis served McNamara well until the US escalation of the war in Vietnam when the Hanoi regime declined to conform to follow his carefully constructed models of behavior. 

In social media, a mutual is a pair of individuals who follow each other's social media accounts, whether by agreement or organically and there’s something a niche activity is working out the extent to which the behavior happens between bots.  Mutuality (reciprocity, interchange) was from the 1580s.  Mutually (reciprocally, in a manner of giving and receiving), was noted from the 1530s and the phrase mutually exclusive was first recorded in the 1650s.  The specialized mutualism (from the Modern French mutuellisme) dates from 1845, referring to the doctrine of French anarchist-socialist Pierre-Joseph Proudhon (1809-1865) that individual and collective well-being is attainable only by mutual dependence.  In the biological sciences, it was first used in 1876 to describe "a symbiosis in which two organisms living together mutually and permanently help and support one another" although there are those who differentiate mutualism (a type of co-existence where neither organism is directly affected by the other but the influence they exert on other organisms or the environment is of benefit to the other) from symbiosis (where there’s a co-dependency).

Parimutuel betting is from the French invention pari mutuel (mutual betting), the construct being pari (wager, from parier (to bet) from the Latin pariare (to settle a debt (literally “to make equal”)) from par, from paris (equal) + mutuel (mutual).  It describes a gambling system where all bets of a particular type are pooled and from this (gross-pool), taxes and the vigorish (from the Yiddish וויגריש‎ (vigrish), from the Russian вы́игрыш (výigryš) (winnings), the commission or “hose-take" are deducted.  The dividends are then calculated by dividing the remainder (net pool) by all winning bets.  In many jurisdictions it’s called the Tote after the totalisator, which calculates and displays bets already made; in Australia and New Zealand it’s the basis of the original agency structure of the Totalisator Agency Board (TAB).

The adoption of mutual as a synonym for "common" is from 1630s and was long condemned as being used “loosely, improperly and not infrequently, often by those who should know better”; “mutual friend" seemed the most common offence.  The view was that “mutual” could apply to only two objects and “common” should be used if three or more were involved.  Opinion has thankfully since softened.  Mutual and common (in the sense of the relation of two or more persons or things to each other) have been used synonymously since the sixteenth century and the use is considered entirely standard.  Objections are one of those attempts to enforce create rules in English which never existed, the only outcome being the choice of use treated as a class-identifier by those who care about such things and either ignored or un-noticed by most.  Tautologous use of mutual however should be avoided: One should say co-operation (not mutual co-operation) between two states.

Common (pronounced kom-uhn)

(1) Belonging equally to, or shared alike by, two or more or all in question (as in common property; common interests etc).

(2) Pertaining or belonging equally to an entire community, nation, or culture; public (as in common language; common history etc).

(3) Joint; united.

(4) Prevailing; Widespread; general; universal (eg common knowledge).

(5) Customary, habitual, everyday.

(6) In some jurisdictions a tract of land owned or used jointly by the residents of a community, usually a central square or park in a city or town (often as “the commons” or “the common”).

(7) In domestic & international law, the right or liberty, in common with other persons, to take profit from the land or waters of another, as by pasturing animals on another's land (common of pasturage ) or fishing in another's waters (common of piscary).  Of interest to economist and ecologists because of the disconnection between the economic gain from the commons and the responsibility for its care and management.

(8) Vulgar, ordinary, cheap, inferior etc (as a derogatory expression of class, often in phrases such as “common as muck” or “common as potatoes”, the back-handed compliment “the common-touch” applied to politicians best at disguising their contempt for the voters (or, as they refer to us: “the ordinary people”).

(9) In some (particularly Germanic) languages, of the gender originating from the coalescence of the masculine and feminine categories of nouns.

(10) In grammar, of or pertaining to common nouns as opposed to proper nouns.

(11) In the vernacular, referring to the name of a kind of plant or animal but its common (ie conversational) rather than scientific name (the idea reflected in the phrase “common or garden”).

(12) Profane; polluted (obsolete).

(13) Given to lewd habits; prostitute (obsolete).

(14) To communicate something; to converse, talk; to have sex; to participate; to board together; to eat at a table in common (all obsolete vernacular forms).

1250–1300: From the Middle English comun (belonging to all, owned or used jointly, general, of a public nature or character), from the Anglo-French commun, from the Old French, commun (Comun was rare in the Gallo-Romance languages, but reinforced as a Carolingian calque of the Proto-West Germanic gamainī (common) in the Old French and commun was the spelling adopted in the Modern French) (common, general, free, open, public), from the Latin commūnis (universal, in common, public, shared by all or many; general, not specific; familiar, not pretentious), thought originally to mean “sharing common duties,” akin to mūnia (duties of an office), mūnus (task, duty, gift), from the unattested base moin-, cognate with mean.  The Latin was from a reconstructed primitive Indo-European compound ḱom-moy-ni-s  (held in common), a compound adjective, the construct being ko- (together) + moi-n- (a suffixed form of the root mei- or mey (to change, go, move (hence literally "shared by all").  The second element of the compound was the source also of the Latin munia (duties, public duties, functions; specific office).  It was possibly reinforced in the Old French by the Germanic form of ḱom-moy-ni-s  (ko-moin-i) and influenced also the German gemein, and the Old English gemne (common, public).  Comun and its variations cam to displace the native Middle English imene & ȝemǣne (common, general, universal (from the Old English ġemǣne (common, universal)), and the later Middle English mene & mǣne (mean, common (also from the Old English ġemǣne)) and the Middle English samen & somen (in common, together (from the Old English samen (together)). A doublet of gmina.  Common is a noun, verb & adjective, commoner is a noun & adjective, commonality is a noun and commonly is an adverb; the noun plural is commons.

Common has been used disparagingly of women and criminals since at least the fourteenth century and snobs have added categories since as required.  The meanings "pertaining equally to or proceeding equally from two or more" & "not distinguished, belonging to the general mass" was from circa 1400 whereas the sense of "usual, not exceptional, of frequent occurrence" & "ordinary, not excellent" dates from the late fourteenth century.  Common prayer was that done in public in unity with other worshipers as contrasted with private prayer, both probably more common then than now.  The Church of England's Book of Common Prayer was first published in 1549 and went through several revisions for reasons both theological and political.  The 1662 edition remains the standard collection of the prayer books used in the Anglican Communion and while many churches now use versions written in more modern English, there remain traditionalists who insist on one of the early editions.

The common room was noted first in the 1660s, a place in the university college to which all members were granted common access.  The late fourteenth century common speech was used to describe both English and (less often) vernacular (which came to be called vulgar) Latin.  From the same time, the common good was an English adoption of the Latin bonum publicum (the common weal).  Common sense is from 1839 and is U whereas, because of the tortured grammar, 1848’s common-sensible is thought non-U.  The idea of common sense had been around since the fourteenth century but with a different meaning to the modern: The idea was of an internal mental power supposed to unite (reduce to a common perception) the impressions conveyed by the five physical senses (sensus communisin the Latin, koine aisthesis in the Ancient Greek). Thus it evolved into "ordinary understanding, without which one is foolish or insane" by the 1530s, formalised as "good sense" by 1726 with common-sense in the modern sense the nineteenth century expression.

The mid-fourteenth century common law was "the customary and unwritten laws of England as embodied in commentaries and old cases", as opposed to statute law.  Over the years, this did sometimes confuse people because in different contexts (common law vs statute law; common law versus equity; common law vs civil law) the connotations were different.  The phrase common-law marriage is attested from a perhaps surprisingly early 1909.  In the English legal system, common pleas was from the thirteenth century, from the Anglo-French communs plets (hearing civil actions by one subject against another as opposed to pleas of the crown).  In corporate law, common stock is attested from 1888.  The late fourteenth century commoner is from the earlier Anglo-French where in addition to conveying the expected sense of "one of the common people” also had the technical meaning “a member of the third estate of the estates-general".  In English it acquired the dual meaning as (1) of non-royal blood and (2), since the mid-fifteenth century “a member of the House of Commons”.  Commonly the adverb is from circa 1300 and commonness the noun from the 1520s though it originally meant only "state or quality of being shared by more than one", the idea of something of "quality of being of ordinary occurrence" not noted until the 1590s.  The adjective uncommon assumed a similar development, in the 1540s meaning "not possessed in common" and by the 1610s meaning "not commonly occurring, unusual; rare".

Last thoughts on a non-rule

The distinction between mutual (reciprocal; between two) and common (among three or more) probably once was, at least to some extent, observed by educated writers, Dr Johnson (1709-1984) in his A Dictionary of the English Language (1755) allowing but one definition: MUTUAL a. Reciprocal; each acting in return or correspondence to the other.

G K Chesterton.

That old curmudgeon G K Chesterton (1874-1936) was certainly convinced.  Writing about Charles Dickens (1812–1870) novel Our Mutual Friend (1864-1865), he claimed the title was the source of the phrase in general speech, snobbily noting of it was the “…old democratic and even uneducated Dickens who is writing here. The very title is illiterate. Any priggish pupil teacher could tell Dickens that there is no such phrase in English as 'our mutual friend'.  Anyone could tell Dickens that 'our mutual friend' means 'our reciprocal friend' and that 'our reciprocal friend' means nothing. If he had only had all the solemn advantages of academic learning (the absence of which in him was lamented by the Quarterly Review), he would have known better. He would have known that the correct phrase for a man known to two people is 'our common friend'."

The phrase in the English novel however pre-dated Dickens, Jane Austen (1775-1817) using it in both Emma (1816) and Persuasion (1818) and long before 1864, Mary Shelley (1797–1851), Sir Walter Scott (1771–1832), William Makepeace Thackeray (1811–1863), Herman Melville (1819–1891), James Fenimore Cooper (1789–1851) and Elizabeth Gaskell (1810–1865) all had “mutual friend” in their text.  Dickens, with the prominence afforded by the title and serialized in the press, doubtless popularized it and, as Chesterton well knew, literature anyway isn’t necessarily written in "common speech".  Whoever opened the floodgates, after 1864, mutual friends continued to flow, the writers George Orwell (1903-1950), Joseph Conrad (1857–1924), Jerome K Jerome (1859–1927), Rudyard Kipling (1865–1936), Mark Twain (1835-1910), Anthony Trollope (1815-1882), Henry James (1843–1916), Robert Louis Stevenson (1850–1894), Arthur Conan Doyle (1859–1930) and Church of England (broad faction) priest & historian Charles Kingsley (1819–1875) all content with "mutual friend" so those condemned by Chesterton are in good company.  The old snob probably did ponder if calling someone a “common friend” might create a misunderstanding but then, good with words, he’d probably avoid that by suggesting they were “rather common” or “a bit common" if that was what he wanted to convey, which not infrequently he often did.

Lindsay Lohan and her lawyer in court, Los Angeles, December 2011.