Exposome

Exposome (pronounced eks-poh-sohm)

(1) A concept describing (1) the environmental exposures an individual encounters throughout life and (2) how these factors impact an individual's biology and health.

(2) The collection of environmental factors (stress, diet, climate, health-care etc) to which an individual is exposed and which can have an effect on health outcomes.

2005: The construct was expos(e) +‎ -ome, the word coined by cancer epidemiologist Dr Christopher Wild, then director of the International Agency for Research on Cancer (IARC).  Expose (in the sense of “to lay open to danger, attack, harm etc”; “to lay open to something specified”) dates from the mid-fifteenth century and was from the late Middle English exposen, from the Middle French exposer (to lay open, set forth), from the Latin expōnō (set forth), with contamination from poser (to lay, place). The –ome suffix was an alteration of -oma, from the Ancient Greek -ωμα (-ōma).  It was only partially cognate to -some (body), from σῶμα (soma) (body), in that both share the case ending -μα (-ma), but the ω was unrelated.  The sense was of “a mass of something” and use is familiar in forms such as genome (in genetics the complete genetic information (DNA (deoxyribonucleic acid) or RNA (ribonucleic acid)) and phenome (the whole set of phenotypic entities in a cell, tissue, organ, organisms, and species). Exposome is a noun and exposomic is an adjective; the noun plural is exposomes.

The study and assessment of external and internal factors (chemical, physical, biological, social, climatic etc) factors that may influence human health is not new and evidence of interest in the topic(s) exist in the literature of physicians and philosophers (there was sometimes overlap) from the ancient civilizations of Greece, Rome, China, Persia and India.  One of the paradoxes of modernity in medicine was that simultaneously there developed an interest in (1) interdisciplinary and holistic approaches while (2) specialization become increasingly entrenched, the latter leading sometimes to a “siloing” in research and data accumulation.  What makes exposome a useful tool is it is a way of expressing the interplay between genetics and environmental factors in the development of diseases with a particular focus on chronic conditions and widely the concept has been applied in many fields of medicine beyond public health.  What it does is calculate the cumulative effect of multiple exposures, allowing researchers to “scope-down” to specific or general gene-environment interactions, producing data to permit a more accurate assessment of disease risk and thus the identification of useful modes of intervention.

Dr Wild’s coining of exposome came about because some word or phrase was needed to describe his innovation which was the application of a systematic approach to measuring environmental exposures to what was coming to be known about the human genome; in a sense it was an exercise in cause and effect, the three components being (1) the external exposome, (2) the internal exposome and (3) the biological response.  The external exposome included factors such as air pollution, diet and socioeconomic factors as well as specific external factors like chemicals and radiation.  The internal exposome included endogenous factors, such as hormones, inflammation, oxidative stress, and gut microbiota.  The biological response described the complex interactions between the external and internal exposome factors and their influence on an individual's physiology and health.

At its most comprehensive (and complex), the exposome is a cumulative measure of all environmental exposures to which an individual has been subject throughout their entire life.  While that’s something that can be modelled for an “imagined person”, in a real-world instance it will probably always be only partially complete, not least because in some cases critical environmental exposures may not be known for long after their effect has been exerted; indeed, some may be revealed only by an autopsy (post mortem).  Conceptually however, the process can be illustrated by example and one illustrative of the approach is to contrast the factors affecting the same individual living in three different places.  What that approach does is emphasize certain obvious differences between places but variations in an exposome don’t depend on the sample being taken in locations thousands of miles apart.  For a variety of reasons, the same individual might record a radically different outcome if (in theory) living their entire life in one suburb compared with one adjacent or even in one room in one dwelling compared with another perhaps only a few feet away.  Conditions can be similar across a wide geographical spread or different despite close proximity (even between people sitting within speaking distance), the phenomenon of “micro-climates” in open-plan offices well documented.  The number of variables which can be used usefully to calculate (estimate might be a better word) an individual’s (or a group’s) exposome is probably at least in the dozens but could easily be expanded well into three figures were one to itemize influences (such as chemicals or specifics types of pollutant matter) and such is the complexity of the process that the mere existence of some factors might be detrimental to some individuals yet neutral or even beneficial to others.  At this stage, although the implications of applying AI (artificial intelligence) to the interaction of large data sets with a individual’s genetic mix have intrigued some, the exposome remains an indicative conceptual model rather than a defined process.

As an example, consider the same individual living variously in New York City, Dubai or Los Angeles.  In each of those places, some factors will be universal within the locality while others will vary according to which part of place one inhabits and even at what elevation at the same address; the physical environment in a building’s ground floor greatly can vary from that which prevails on the 44^th floor:

Lindsay Lohan in New York City in pastel yellow & black bouclé tweed mini-dress.  Maintaining an ideal BMI (body mass index) is a positive factor in ones exposome. 

(1) Air Quality and Pollution: Moderate to high levels of air pollution, especially from traffic (NO₂, PM2.5). Seasonal heating (oil and gas) contributes in winter.  Subway air has unique particulate matter exposure.

(2) Climate and UV Radiation: Humid continental climate—cold winters and hot summers. Seasonal variability affects respiratory and cardiovascular stressors.

(3) Diet and Food Environment: Diverse food options—high availability of ultra-processed foods but also global cuisines. Food deserts in poorer boroughs can reduce fresh produce access.

(4) Built Environment and Urban Design: Dense, walkable, vertical urban environment. High reliance on public transport; more noise pollution and crowding stress.  Lower car ownership can reduce personal emissions exposure.

(5) Cultural and Psychosocial Stressors: High-paced lifestyle, long working hours. High density increases social stress, noise, and mental health challenges.  Diversity can be enriching or alienating, depending on context.

(6) Economic and Occupational Exposures: Highly competitive job market. Occupational exposures vary widely—white-collar vs service industries. Union protections exist in some sectors.

(7) Healthcare Access and Public Policy: Robust healthcare infrastructure, but disparities remain by borough and income. Medicaid and public hospitals provide some safety net.

Lindsay Lohan in Dubai in J.Lo flamingo pink velour tracksuit.  A healthy diet and regular exercise are factors in one's exposome. 

(1) Air Quality and Pollution: Frequently exposed to dust storms (fine desert dust), high PM10 levels, and air conditioning pollutants. Limited greenery means less natural air filtration.  Desalination plants and industrial expansion add further exposure.

(2) Climate and UV Radiation: Extreme desert heat (45°C+), intense UV exposure, little rain. Heat stress and dehydration risks are chronic, especially for outdoor workers.

(3) Diet and Food Environment: High import dependency. Abundant processed and fast foods, especially in malls. Dietary pattern skewed toward high sugar and fat content.  Cultural fasting (eg Ramadan) introduces cyclical dietary stressors.

(4) Built Environment and Urban Design: Car-centric city. Pedestrian-unfriendly in many areas due to heat and design. Heavy air conditioning use is a major indoor exposure pathway.

(5) Cultural and Psychosocial Stressors: Strict social codes and legal restrictions influence behavioral exposures. Expat life often means social disconnection and job insecurity for migrant workers.

(6) Economic and Occupational Exposures: Large migrant workforce faces occupational health risks, including long hours in extreme heat. Labor protections are inconsistent.

(7) Healthcare Access and Public Policy: Healthcare access stratified—good for citizens and wealthy expats, less so for low-wage migrants. Private sector dominates.

Lindsay Lohan in Los Angeles in 2005 Mercedes-Benz SL65 AMG (2005-2011) Roadster (R230, 2002-2011).  Smoking is a factor in one's exposome.

(1) Air Quality and Pollution: Known for smog due to vehicle emissions and topography (valley trap). Ozone levels high, especially in summer. Wildfire smoke increasingly common.

(2) Climate and UV Radiation: Mediterranean climate with mild, dry summers. High UV exposure, though moderated by coastal influence. Drought conditions affect water quality and stress.

(3) Diet and Food Environment: Strong health-food culture, organic and plant-based diets more common. Yet fast food and food deserts remain in less affluent areas.  Hispanic and Asian dietary influences prominent.

(4) Built Environment and Urban Design: Sprawling, suburban in many parts. High car dependence means more exposure to vehicle exhaust.  Outdoor activities more common in certain demographics (eg, beach culture).

(5) Cultural and Psychosocial Stressors: Cultural emphasis on appearance, wealth, and entertainment may increase psychosocial pressure.  Homelessness crisis also creates variable community stress exposures.

(6) Economic and Occupational Exposures: Gig economy widespread, leading to precarious employment. Hollywood and tech industries also introduce unique workplace stress patterns.

(7) Healthcare Access and Public Policy: California’s public health programs are progressive, but uninsured rates still high. Proximity to cutting-edge research centers can boost care quality for some.

So one's exposome is a product of what one wants or gets from life, mapped onto a risk analysis table.  In New York City, one copes with urban pollution and persistent subway dust in an increasingly variable climate marked by periods of high humidity, a dietary range determined by one's wealth, the advantage of a good (if not always pleasant) mass transit system and the possibility of a “walking distance” lifestyle, albeit it in usually crowded, fast-paced surroundings.  Employment conditions are mixed and access to quality health care is a product of one's insurance status or wealth.

In Dubai, one lives with frequent dust storms, months of intense heat and UV exposure, a dependence on food imports, the constant temptation of fast food (FSS; fat, salt, sugar).  The car-centric lifestyle has created a built environment described as “pedestrian-hostile” and there are sometimes severe legal limits on the personal freedom especially for migrant workers who are subject to heat exposure and limited labor rights (even those which exist often not enforced).  The health system distinctly is tiered (based on wealth) and almost exclusively privatized.

The air quality in Los Angeles greatly has improved since the 1970s but climate change has resulted in the more frequent intrusion of smoke from wildfires and the prevailing UV exposure tends to be high; the climate is not as “mild” as once it was rated.  While there are pockets in which walkability is good, Los Angeles mostly is a car-dependent culture and the coverage and frequency of mass-transit has in recent decades declined.  Although this is not unique to the city, there's heightened awareness of a sensitivity to specific cultural pressures based on appearances and perceptions of lifestyle while housing stress is increasing.  Economic pressures are being exacerbated by the growth of the gig economy and traditionally secure forms of employment are being displaced by AI (bots, robots and hybrids).  Although California's healthcare system is sometimes described as "progressive", on the ground, outcomes are patchy.

So each location shapes the exposome in distinctive ways and the potential exists for the process better to be modelled so public health interventions and policies can be adjusted.  Of course, some risks are global: anywhere on the planet there’s always the chance one might be murdered by the Freemasons but some things which might seem unlikely to be affected by location turn out also to be an exposome variable. Because planet Earth is (1) roughly spherical, (2) and travels through space (where concepts like up & down don’t apply) and (3) constantly is exposed to meteoroids (every day Earth receives tons of “space dust”), it would be reasonable to assume one is equally likely to be struck by a meteoroid wherever one may be.  However, according to NASA (the US National Aeronautics and Space Administration), strikes are not equally likely everywhere, some latitudes (and regions) being more prone, due to several factors:

(1) Because Earth’s rotation and orbital motion create a bias, meteoroids tend more often to approach from the direction of Earth’s orbital motion (the “apex direction”), meaning the leading hemisphere (the side facing Earth's motion, near the dawn terminator) sees more meteoroid entries than the trailing hemisphere.  On a global scale, the effect is small but is measurable with the risk increasing as one approaches the equatorial regions where rotational velocity is greatest.

(2) Because most meteoroids approach from near the plane of the Solar System (the ecliptic plane), there’s what NASA calls a “latitude distribution bias”: Earth’s equator being tilted only some 23.5° from the ecliptic, meteoroids are more likely to intersect Earth’s atmosphere near lower latitudes (the tropical & sub-tropical zones) than near the poles.  So, those wishing to lower their risk should try to live in the Arctic or Antarctic although those suffering chronic kosmikophobia (fear of cosmic phenomena) are likely already residents.

(3) Some 70% of the Earth’s surface area being the seas and oceans, statistically, most meteoroids land in the water rather than in land so the lesson is clear: avoid living at sea.  The calculated probability is of course just math; because sparsely populated deserts accumulate meteorites better because erosion is low, a large number have been found in places like the Sahara and outback Australia but those numbers reflect a preservation bias and don’t necessarily confirm a higher strike rate.  The lesson from the statisticians is: Don’t dismiss the notion of living in a desert because of a fear of being struck by a meteoroid.

(4) Gravitational focusing, although it does increase Earth’s meteoroid capture rates (disproportionately so for objects travelling more slowly), is a global effect so there is no known locational bias.  While there is at least one documented case of a person being struck by a meteoroid, the evidence does suggest the risk is too low to be statistically significant and should thus not be factored into the calculation of one’s exposome because one is anywhere at greater risk of being murdered by the Freemasons.

Ms Ann Hodges with bruise, Alabama, September. 1952.  Painful though it would have been, she did get  her “15 minutes of fame” and eventually sold the fragment for US$25 so there was that.

In the narrow technical sense, many people have been struck by objects from space (as estimated 40+ tons of the stuff arrives every day) but most fragments are dust particles, too small to be noticed.  The only scientifically verified injury a person has suffered was an impressively large bruise a meteorite (the part of a meteoroid that survives its fiery passage through the atmosphere to land on Earth’s surface) on 10 September 1954 inflicted on Ms Ann Hodges (1920-1972) of Sylacauga, Alabama in the US.  Weighing 7.9 lb (3.6 kg), the intruder crashed through the roof of her house and bounced off a radio, striking her while enjoying a nap on the sofa.  The meteoroid was called Sylacauga and, just as appropriately, the offending meteorite was named the Hodges Fragment.  Anatomically modern humans (AMH) have been walking the planet for perhaps 300,000 years and we’ve been (more or less) behaviorally modern (BMH) for maybe a quarter of that so it’s possible many more of us have been struck,  In the absence of records, while it’s impossible to be definitive, it’s likely more have been murdered by the Freemasons that have ever been killed by stuff falling from space although, as the history of species extinction illustrates, a direct hit on someone is not a prerequisite for dire consequences.

Dashcam footage of meteorite fragment in the sky over Lexington, South Carolina.

The cosmic intruder crashed through the roof of a house on 26 June, 2025 and although there were no injuries, Fox News reported the fragment left a hole in the floor “about the size of a large cherry tomato”.  Analysis determined the rock was from the asteroid belt between Mars and Jupiter and as well as the dramatic fireball many captured on their dashcams, it would briefly have broken the sound barrier as it entered Earth’s atmosphere.  It was also very old, dating from slightly before the formation of the Solar System’s rocky inner planets (one of which is Earth) some 4.56 billion years ago and such fragments are of interest to many branches of science because they represent a small part of the “basic building blocks” of those planets and can thus assist in understanding the processes active during the Solar System’s earliest days.  Curiously (to those not trained in such things), the cosmologists explained “such a small fragment didn’t present a threat to anyone” which seems strange given its impact left a small crater in a floor, one implication being one wouldn’t wish for such a thing to hit one’s skull.  That the impact happened in Georgia, a state adjacent to Alabama where a half-century earlier the unfortunate Ms Hodges was struck, may make some add “meteorite fragments” to their list of “exposome factors south of the Mason-Dixon Line” but the sample size is too small for conclusions to be drawn and the events are mere geographic coincidences.

Bunker

Bunker (pronounced buhng-ker)

(1) A large bin or receptacle; a fixed chest or box.

(2) In military use, historically a fortification set mostly below the surface of the ground with overhead protection provided by logs and earth or by concrete and fitted with above-ground embrasures through which guns may be fired.

(3) A fortification set mostly below the surface of the ground and used for a variety of purposes.

(4) In golf, an obstacle, classically a sand trap but sometimes a mound of dirt, constituting a hazard.

(5) In nautical use, to provide fuel for a vessel.

(6) In nautical use, to convey bulk cargo (except grain) from a vessel to an adjacent storehouse.

(7) In golf, to hit a ball into a bunker.

(8) To equip with or as if with bunkers.

(9) In military use, to place personnel or materiel in a bunker or bunkers (sometimes as “bunker down”).

1755–1760: From the Scottish bonkar (box, chest (also “seat” (in the sense of “bench”) of obscure origin but etymologists conclude the use related to furniture hints at a relationship with banker (bench).  Alternatively, it may be from a Scandinavian source such as the Old Swedish bunke (boards used to protect the cargo of a ship).  The meaning “receptacle for coal aboard a ship” was in use by at least 1839 (coal-burning steamships coming into general use in the 1820s).  The use to describe the obstacles on golf courses is documented from 1824 (probably from the extended sense “earthen seat” which dates from 1805) but perhaps surprisingly, the familiar sense from military use (dug-out fortification) seems not to have appeared before World War I (1914-1918) although the structures so described had for millennia existed.  “Bunkermate” was army slang for the individual with whom one shares a bunker while the now obsolete “bunkerman” (“bunkermen” the plural”) referred to someone (often the man in charge) who worked at an industrial coal storage bunker.  Bunker & bunkerage is a noun, bunkering is a noun & verb, bunkered is a verb and bunkerish, bunkeresque, bunkerless & bunkerlike are adjectives; the noun plural is bunkers.

Just as ships called “coalers” were used to transport coal to and from shore-based “coal stations”, it was “oilers” which took oil to storage tanks or out to sea to refuel ships (a common naval procedure) and these STS (ship-to-ship) transfers were called “bunkering” as the black stuff was pumped, bunker-to-bunker.  That the coal used by steamships was stored on-board in compartments called “coal bunkers” led ultimately to another derived term: “bunker oil”.  When in the late nineteenth century ships began the transition from being fuelled by coal to burning oil, the receptacles of course became “oil bunkers” (among sailors nearly always clipped to “bunker”) and as refining processes evolved, the fuel specifically produced for oceangoing ships came to be called “bunker oil”.

Bunker oil is “dirty stuff”, a highly viscous, heavy fuel oil which is essentially the residue of crude oil refining; it’s that which remains after the more refined and volatile products (gasoline (petrol), kerosene, diesel etc) have been extracted.  Until late in the twentieth century, the orthodox view of economists was its use in big ships was a good thing because it was a product for which industry had little other use and, as essentially a by-product, it was relatively cheap.  It came in three flavours: (1) Bunker A: Light fuel oil (similar to a heavy diesel), (2) Bunker B: An oil of intermediate viscosity used in engines larger than marine diesels but smaller than those used in the big ships and (3) Bunker C: Heavy fuel oil used in container ships and such which use VLD (very large displacement), slow running engines with a huge reciprocating mass.  Because of its composition, Bucker C especially produced much pollution and although much of this happened at sea (unseen by most but with obvious implications), when ships reached harbor to dock, all the smoke and soot became obvious.  Over the years, the worst of the pollution from the burning of bunker oil greatly has been reduced (the work underway even before the Greta Thunberg (b 2003) era), sometimes by the simple expedient of spraying a mist of water through the smoke.

Floor-plans of the upper (Vorbunker) and lower (Führerbunker) levels of the structure now commonly referred to collectively as the Führerbunker.

History’s most infamous bunker remains the Berlin Führerbunker in which Adolf Hitler (1889-1945; Führer (leader) and German head of government 1933-1945 & head of state 1934-1945) spent much of the last few months of his life.  In the architectural sense there were a number of Führerbunkers built, one at each of the semi-permanent Führerhauptquartiere (Führer Headquarters) created for the German military campaigns and several others built where required but it’s the one in Berlin which is remembered as “the Führerbunker”.  Before 1944 when the intensification of the air raids by the RAF (Royal Air Force) and USAAF (US Army Air Force) the term Führerbunker seems rarely to have been used other than by the architects and others involved in their construction and it wasn’t a designation like Führerhauptquartiere which the military and other institutions of state shifted between locations (rather as “Air Force One” is attached not to a specific airframe but whatever aircraft in which the US president is travelling).  In subsequent historical writing, the term Führerbunker tends often to be applied to the whole, two-level complex in Berlin and although it was only the lower layer which officially was designated as that, for most purposes the distinction is not significant.  In military documents, after January, 1945 the Führerbunker was referred to as Führerhauptquartiere.

Führerbunker tourist information board, Berlin, Germany.

Only an information board at the intersection of den Ministergärten and Gertrud-Kolmar-Straße, erected by the German Goverment in 2006 prior to that year's FIFA (Fédération Internationale de Football Association (International Federation of Association Football)) World Cup now marks the place on Berlin's Wilhelmstrasse 77 where once the Führerbunker was located.  The Soviet occupation forces razed the new Reich Chancellery and demolished all the bunker's above-ground structures but the subsequent GDR (Deutsche Demokratische Republik (German Democratic Republic; the old East Germany) 1949-1990) abandoned attempts completely to destroy what lay beneath.  Until after the fall of the Berlin Wall (1961-1989) the site remained unused and neglected, “re-discovered” only during excavations by property developers, the government insisting on the destruction on whatever was uncovered and, sensitive still to the spectre of “Neo-Nazi shrines”, for years the bunker’s location was never divulged, even as unremarkable buildings (an unfortunate aspect of post-unification Berlin) began to appear on the site.  Most of what would have covered the Führerbunker’s footprint is now a supermarket car park.

The first part of the complex to be built was the Vorbunker (upper bunker or forward bunker), an underground facility of reinforced concrete intended only as a temporary air-raid shelter for Hitler and his entourage in the old Reich Chancellery.  Substantially completed during 1936-1937, it was until 1943 listed in documents as the Luftschutzbunker der Reichskanzlei (Reich Chancellery Air-Raid Shelter), the Vorbunker label applied only in 1944 when the lower level (the Führerbunker proper) was appended.  In mid January, 1945, Hitler moved into the Führerbunker and, as the military situation deteriorated, his appearances above ground became less frequent until by late March he rarely saw the sky,  Finally, on 30 April, he committed suicide.

Bunker Busters

Northrop Grumman publicity shot of B2-Spirit from below, showing the twin bomb-bay doors through which the GBU-57 are released.

Awful as they are, there's an undeniable beauty in the engineering of some weapons and it's unfortunate humankind never collectively has resolved exclusively to devote such ingenuity to stuff other than us blowing up each other.  That’s not a new sentiment, being one philosophers and others have for millennia expressed in various ways although since the advent of nuclear weapons, concerns understandably become heightened.  Like every form of military technology ever deployed, once the “genie is out of the bottle” the problem is there to be managed and at the dawn of the atomic age, delivering a lecture in 1936, the British chemist and physicist Francis Aston (1877–1945) (who created the mass spectrograph, winning the 1922 Nobel Prize in Chemistry for his use of it to discover and identify the isotopes in many non-radioactive elements and for his enunciation of the whole number rule) observed:

“There are those about us who say that such research should be stopped by law, alleging that man's destructive powers are already large enough.  So, no doubt, the more elderly and ape-like of our ancestors objected to the innovation of cooked food and pointed out the great dangers attending the use of the newly discovered agency, fire.  Personally, I think there is no doubt that sub-atomic energy is available all around us and that one day man will release and control its almost infinite power.  We cannot prevent him from doing so and can only hope that he will not use it exclusively in blowing up his next door neighbor.”

The use in June 2025 by the USAF (US Air Force) of fourteen of its Boeing GBU-57 (Guided Bomb Unit-57) Massive Ordnance Penetrators (MOP) bombs against underground targets in Iran (twelve on the Fordow Uranium Enrichment Plant and two on the Natanz nuclear facility) meant “Bunker Buster” hit the headlines.  Carried by the Northrop B-2 Spirit heavy bomber (built between 1989-2000), the GBU-57 is a 14,000 kg (30,000 lb) bomb with a casing designed to withstand the stress of penetrating through layers of reinforced concrete or thick rock.  “Bunker buster” bombs have been around for a while, the ancestors of today’s devices first built for the German military early in World War II (1939-1945) and the principle remains unchanged to this day: up-scaled armor-piercing shells.  The initial purpose was to produce a weapon with a casing strong enough to withstand the forces imposed when impacting reinforced concrete structures, the idea simple in that what was needed was a delivery system which could “bust through” whatever protective layers surrounded a target, allowing the explosive charge to do damage where needed rtaher than wastefully being expended on an outer skin.  The German weapons proved effective but inevitably triggered an “arms race” in that as the war progressed, the concrete layers became thicker, walls over 2 metres (6.6 feet) and ceilings of 5 (16) being constructed by 1943.  Technological development continued and the idea extended to rocket propelled bombs optimized both for armor-piercing and aerodynamic efficiency, velocity a significant “mass multiplier” which made the weapons still more effective.

USAF test-flight footage of Northrop B2-Spirit dropping two GBU-57 "Bunker Buster" bombs.

Concurrent with this, the British developed the first true “bunker busters”, building on the idea of the naval torpedo, one aspect of which was in exploding a short distance from its target, it was highly damaging because it was able to take advantage of one of the properties of water (quite strange stuff according to those who study it) which is it doesn’t compress.  What that meant was it was often the “shock wave” of the water rather than the blast itself which could breach a hull, the same principle used for the famous “bouncing bombs” used for the RAF’s “Dambuster” (Operation Chastise, 17 May 1943) raids on German dams.  Because of the way water behaved, it wasn’t necessary to score the “direct hit” which had been the ideal in the early days of aerial warfare.

RAF Bomber Command archive photograph of Avro Lancaster (built between 1941-1946) in flight with Grand Slam mounted (left) and a comparison of the Tallboy & Grand Slam (right), illustrating how the latter was in most respects a scaled-up version of the former.  To carry the big Grand Slams, 32 “B1 Special” Lancasters were in 1945 built with up-rated Rolls-Royce Merlin V12 engines, the removal of the bomb doors (the Grand Slam carried externally, its dimensions exceeding internal capacity), deleted front and mid-upper gun turrets, no radar equipment and a strengthened undercarriage.  Such was the concern with weight (especially for take-off) that just about anything non-essential was removed from the B1 Specials, even three of the four fire axes and its crew door ladder.  In the US, Boeing went through a similar exercise to produce the run of “Silverplate” B-29 Superfortresses able to carry the first A-bombs used in August, 1945. 

Best known of the British devices were the so called “earthquake bombs”, the Tallboy (12,000 lb; 5.4 ton) & Grand Slam (22,000 lb, 10 ton) which, despite the impressive bulk, were classified by the War Office as “medium capacity”.  The terms “Medium Capacity” (MC) & “High Capacity” referenced not the gross weight or physical dimensions but ratio of explosive filler to the total weight of the construction (ie how much was explosive compared to the casing and ancillary components).  Because both had thick casings to ensure penetration deep into hardened targets (bunkers and other structures encased in rock or reinforced concrete) before exploding, the internal dimensions accordingly were reduced compared with the ratio typical of contemporary ordinance.  A High Capacity (HC) bomb (a typical “general-purpose” bomb) had a thinner casing and a much higher proportion of explosive (sometimes over 70% of total weight).  These were intended for area bombing (known also as “carpet bombing”) and caused wide blast damage whereas the Tallboy & Grand Slam were penetrative with casings optimized for aerodynamic efficiency, their supersonic travel working as a mass-multiplier.  The Tallboy’s 5,200 lb (2.3 ton) explosive load was some 43% of its gross weight while the Grand Slam’s 9,100 lb (4 ton) absorbed 41%; this may be compared with the “big” 4000 lb (1.8 ton) HC “Blockbuster” which allocated 75% of the gross weight to its 3000 LB (1.4 ton) charge.  Like many things in engineering (not just in military matters) the ratio represented a trade-off, the MC design prioritizing penetrative power and structural destruction over blast radius.  The novelty of the Tallboy & Grand Slam was that as earthquake bombs, their destructive potential was able to be unleashed not necessarily by achieving a direct hit on a target but by entering the ground nearby, the explosion (1) creating an underground cavity (a camouflet) and (2) transmitting a shock-wave through the target’s foundations, leading to the structure collapsing into the newly created lacuna. 

The etymology of camouflet has an interesting history in both French and military mining.  Originally it meant “a whiff of smoke in the face (from a fire or pipe) and in figurative use it was a reference to a snub or slight insult (something unpleasant delivered directly to someone) and although the origin is murky and it may have been related to the earlier French verb camoufler (to disguise; to mask) which evolved also into “camouflage”.  In the specialized military jargon of siege warfare or mining (sapping), over the seventeen and nineteenth centuries “camouflet” referred to “an underground explosion that does not break the surface, but collapses enemy tunnels or fortifications by creating a subterranean void or shockwave”.  The use of this tactic is best remembered from the Western Front in World War I, some of the huge craters now tourist attractions.

Under watchful eyes: Grand Ayatollah Ali Khamenei (b 1939; Supreme Leader, Islamic Republic of Iran since 1989) delivering a speech, sitting in front of the official portrait of the republic’s ever-unsmiling founder, Grand Ayatollah Ruhollah Khomeini (1900-1989; Supreme Leader, Islamic Republic of Iran, 1979-1989).  Ayatollah Khamenei seemed in 1989 an improbable choice as Supreme Leader because others were better credentialed but though cautious and uncharismatic, he has proved a great survivor in a troubled region.

Since aerial bombing began to be used as a strategic weapon, of great interest has been the debate over the BDA (battle damage assessment) and this issue emerged almost as soon as the bunker buster attack on Iran was announced, focused on the extent to which the MOPs had damaged the targets, the deepest of which were concealed deep inside a mountain.  BDA is a constantly evolving science and while satellites have made analysis of surface damage highly refined, it’s more difficult to understand what has happened deep underground.  Indeed, it wasn’t until the USSBS (United States Strategic Bombing Survey) teams toured Germany and Japan in 1945-1946, conducting interviews, economic analysis and site surveys that a useful (and substantially accurate) understanding emerged of the effectiveness of bombing although what technological advances have allowed for those with the resources is the so-called “panacea targets” (ie critical infrastructure and such once dismissed by planners because the required precision was for many reasons rarely attainable) can now accurately be targeted, the USAF able to drop a bomb within a few feet of the aiming point.  As the phrase is used by the military, the Fordow Uranium Enrichment Plant is as classic “panacea target” but whether even a technically successful strike will achieve the desired political outcome remains to be seen.

Mr Trump, in a moment of exasperation, posted on Truth Social of Iran & Israel: “We basically have two countries that have been fighting so long and so hard that they don't know what the fuck they're doing."  Actually, both know exactly WTF they're doing; it's just Mr Trump (and many others) would prefer they didn't do it.

Donald Trump (b 1946; US president 2017-2021 and since 2025) claimed “total obliteration” of the targets while Grand Ayatollah Khamenei admitted only there had been “some damage” and which is closer to the truth should one day be revealed.  Even modelling of the effects has probably been inconclusive because the deeper one goes underground, the greater the number of variables in the natural structure and the nature of the internal built environment will also influence blast behaviour.  All experts seem to agree much damage will have been done but what can’t yet be determined is what has been suffered by the facilities which sit as deep as 80 m (260 feet) inside the mountain although, as the name implies, “bunker busters” are designed for buried targets and it’s not always required for blast directly to reach target.  Because the shock-wave can travel through earth & rock, the effect is something like that of an earthquake and if the structure sufficiently is affected, it may be the area can be rendered geologically too unstable again to be used for its original purpose.

Within minutes of the bombing having been announced, legal academics were being interviewed (though not by Fox News) to explain why the attacks were unlawful under international law and in a sign of the times, the White House didn't bother to discuss fine legal points like the distinction between "preventive & pre-emptive strikes", preferring (like Fox News) to focus on the damage done.  However, whatever the murkiness surrounding the BDA, many analysts have concluded that even if before the attacks the Iranian authorities had not approved the creation of a nuclear weapon, this attack will have persuaded them one is essential for “regime survival”, thus the interest in both Tel Aviv and (despite denials) Washington DC in “regime change”.  The consensus seems to be Grand Ayatollah Khamenei had, prior to the strike, not ordered the creation of a nuclear weapon but that all energies were directed towards completing the preliminary steps, thus the enriching of uranium to ten times the level required for use in power generation; the ayatollah liked to keep his options open.  So, the fear of some is the attacks, even if they have (by weeks, months or years) delayed the Islamic Republic’s work on nuclear development, may prove counter-productive in that they convince the ayatollah to concur with the reasoning of every state which since 1945 has adopted an independent nuclear deterrent (IND).  That reasoning was not complex and hasn’t changed since first a prehistoric man picked up a stout stick to wave as a pre-lingual message to potential adversaries, warning them there would be consequences for aggression.  Although a theocracy, those who command power in the Islamic Republic are part of an opaque political institution and in the struggle which has for sometime been conducted in anticipation of the death of the aged (and reportedly ailing) Supreme Leader, the matter of “an Iranian IND” is one of the central dynamics.  Many will be following what unfolds in Tehran and the observers will not be only in Tel Aviv and Washington DC because in the region and beyond, few things focus the mind like the thought of ayatollahs with A-Bombs.

Of the word "bust"

The Great Bust: The Depression of the Thirties (1962) by Jack Lang (left), highly qualified content provider Busty Buffy (b 1996, who has never been accused of misleading advertising, centre) and The people's champion, Mr Lang, bust of Jack Lang, painted cast plaster by an unknown artist, circa 1927, National Portrait Gallery, Canberra, Australia (right).  Remembered for a few things, Jack Lang (1876–1975; premier of the Australian state of New South Wales (NSW) 1925-1927 & 1930-1932) remains best known for having in 1932 been the first head of government in the British Empire to have been sacked by the Crown since William IV (1765–1837; King of the UK 1830-1837) in 1834 dismissed Lord Melbourne (1779–1848; prime minister of the UK 1834 & 1835-1841).

Those learning English must think it at least careless things can both be (1) “razed to the ground” (totally to destroy something (typically a structure), usually by demolition or incineration) and (2) “raised to the sky” (physically lifted upwards).  The etymologies of “raze” and “raise” differ but they’re pronounced the same so it’s fortunate the spellings vary but in other troublesome examples of unrelated meanings, spelling and pronunciation can align, as in “bust”.  When used in ways most directly related to human anatomy: (1) “a sculptural portrayal of a person's head and shoulders” & (2) “the circumference of a woman's chest around her breasts” there is an etymological link but these uses wholly are unconnected with bust’s other senses.

Bust of Lindsay Lohan in white marble by Stable Diffusion.  Sculptures of just the neck and head came also to be called “busts”, the emphasis on the technique rather than the original definition.

Bust in the sense of “a sculpture of upper torso and head” dates from the 1690s and was from the sixteenth century French buste, from the Italian busto (upper body; torso), from the Latin bustum (funeral monument, tomb (although the original sense was “funeral pyre, place where corpses are burned”)) and it may have emerged (as a shortened form) from ambustum, neuter of ambustus (burned around), past participle of amburere (burn around, scorch), the construct being ambi- (around) + urere (to burn),  The alternative etymology traces a link to the Old Latin boro, the early form of the Classical Latin uro (to burn) and it’s though the development in Italian was influenced by the Etruscan custom of keeping the ashes of the dead in an urn shaped like the person when alive.  Thus the use, common by the 1720s of bust (a clipping from the French buste) being “a carving of the “trunk of the human body from the chest up”.  From this came the meaning “dimension of the bosom; the measurement around a woman's body at the level of her breasts” and that evolved on the basis of a comparison with the sculptures, the base of which was described as the “bust-line”, the term still used in dress-making (and for other comparative purposes as one of the three “vital statistics” by which women are judged (bust, waist, hips), each circumference having an “ideal range”).  It’s not known when “bust” and “bust-line” came into oral use among dress-makers and related professions but it’s documented since the 1880s.  Derived forms (sometimes hyphenated) include busty (tending to bustiness, thus Busty Buffy's choice of stage-name), overbust & underbust (technical terms in women's fashion referencing specific measurements) and bustier (a tight-fitting women's top which covers (most or all of) the bust.

Benito Mussolini (1883-1945; Duce (leader) & Prime-Minister of Italy 1922-1943) standing beside his “portrait bust” (1926).

The bust was carved by Swiss sculptor Ernest Durig (1894–1962) who gained posthumous notoriety when his career as a forger was revealed with the publication of his drawings which he’d represented as being from the hand of the French sculptor Auguste Rodin (1840-1917) under whom he claimed to have studied.  Mussolini appears here in one of the subsequently much caricatured poses which were a part of his personality cult.  More than one of the Duce's counterparts in other nations was known to have made fun of some of the more outré poses and affectations, the outstretched chin, right hand braced against the hip and straddle-legged stance among the popular motifs. 

“Portrait bust” in marble (circa 1895) of (1815-1989; chancellor of the German Empire (the "Second Reich") 1871-1890) by the German Sculptor Reinhold Begas (1831-1911).

 In sculpture, what had been known as the “portrait statue” came after the 1690s to be known as the “portrait bust” although both terms meant “sculpture of upper torso and head” and these proved a popular choice for military figures because the aspect enabled the inclusion of bling such as epaulettes, medals and other decorations and being depictions of the human figure, busts came to be vested with special significance by the superstitious.  In early 1939, during construction of the new Reich Chancellery in Berlin, workmen dropped one of the busts of Otto von Bismarck by Reinhold Begas, breaking it at the neck.  For decades, the bust had sat in the old Chancellery and the building’s project manager, Albert Speer (1905–1981; Nazi court architect 1934-1942; Nazi minister of armaments and war production 1942-1945), knowing Adolf Hitler (1889-1945; Führer (leader) and German head of government 1933-1945 & head of state 1934-1945) believed the Reich Eagle toppling from the post-office building right at the beginning of World War I had been a harbinger of doom for the nation, kept the accident secret, hurriedly issuing a commission to the German sculptor Arno Breker (1900–1991) who carved an exact copy.  To give the fake the necessary patina, it was soaked for a time in strong, black tea, the porous quality of marble enabling the fluid to induce some accelerated aging.  Interestingly, in his (sometimes reliable) memoir (Erinnerungen (Memories or Reminiscences) and published in English as Inside the Third Reich (1969)), even the technocratic Speer admitted of the accident: “I felt this as an evil omen”.

The other senses of bust (as a noun, verb & adjective) are diverse (and sometimes diametric opposites and include: “to break or fail”; “to be caught doing something unlawful / illicit / disgusting etc”; “to debunk”; “dramatically or unexpectedly to succeed”; “to go broke”; “to break in” (horses, girlfriends etc): “to assault”; the downward portion of an economic cycle (ie “boom & bust”); “the act of effecting an arrest” and “someone (especially in professional sport) who failed to perform to expectation”.  That’s quite a range and that has meant the creation of dozens of idiomatic forms, the best known of which include: “boom & bust”, “busted flush”, “dambuster”, “bunker buster”,  “busted arse country”, “drug bust”, “cloud bust”, belly-busting, bust one's ass (or butt), bust a gut, bust a move, bust a nut, bust-down, bust loose, bust off, bust one's balls, bust-out, sod buster, bust the dust, myth-busting and trend-busting.  In the sense of “breaking through”, bust was from the Middle English busten, a variant of bursten & bresten (to burst) and may be compared with the Low German basten & barsten (to burst).  Bust in the sense of “break”, “smash”, “fail”, “arrest” etc was a creation of mid-nineteenth century US English and is of uncertain inspiration but most etymologists seem to concur it was likely a modification of “burst” effected with a phonetic alteration but it’s not impossible it came directly as an imperfect echoic of Germanic speech.  The apparent contradiction of bust meaning both “fail” and “dramatically succeed” happened because the former was an allusion to “being busted” (ie broken) while the latter meaning used the notion of “busting through”.

Continuity

Continuity (pronounced kon-tn-oo-i-tee or kon-tn-yoo-i-tee)

(1) The state or quality of being continuous; logical sequence, cohesion or connection; lack of interruption.

(2) A continuous or connected whole.

(3) In political science, as “continuity theory”, an approach to twentieth century German historiography which focuses on structural and sociological continuities between eras (including pre-twentieth century influences and traditions).

(4) In narratology, a narrative device in episodic fiction where previous and/or future events in a series of stories are accounted for in present stories.

(5) As bicontinuity (the sate of being bicontinuous), (1) in topology: homeomorphic (a continuous bijection from one topological space to another, with continuous inverse) and (2) in physics, chemistry (of a liquid mixture), being a continuous phase composed of two immiscible liquids interacting through rapidly changing hydrogen bonds.

(6) In film production, as “continuity girl” (the now archaic title in film production (now called “continuity supervisor” or “script supervisor”)) for the person responsible for ensuring the details in each scene conform to the continuity of the narrative.

(7) In film production, the scenario (in the industry jargon a synonym of “continuity”) of script, scenes, camera angles, details of verisimilitude etc, in the sequence in which they should appear in the final cut.

(8) In fiction (especially in television series but also in film and literature), as “continuity nod”, a reference, to part of the plot of a previous series, volume, episode etc.

(9) In audio & visual production (radio, podcasts, television, internet etc), the spoken part of a script that which provides introductory, transitional or concluding material in non-dramatic (documentaries and such) programmes (some production houses include in their staff establishment the position “continuity announcer”).

(10) In film projection, the continuous projection of a film, using automatic rewind.

(11) In mathematics, a characteristic property of a continuous function.

(12) In mathematics, as semicontinuity (of a function), the state of being semicontinuous (that it is continuous almost everywhere, except at certain points at which it is either upper semi-continuous or lower semi-continuous).

(13) In mathematics, as equicontinuity, (of a family of functions), the state of being equicontinuous (such that all members are continuous, with equal variation in a given neighborhood).  The Lipschitz continuity was named after German mathematician Rudolf Lipschitz (1832–1903); the Scott continuity was named after US logician Dana Scott (b 1932).

(14) In mathematics, as hemicontinuity, the state of being hemicontinuous (having the property that if a sequence of points in the domain of a function converges to a point L, then either the sequence of sets that are the images of those points contains a sequence that converges to a point that is in the image of L, or, alternatively, for every element in the image of L, there will be a sub-sequence in the domain whose image contains a convergent sequence to that element.

(15) In marketing, in the plural, as “continuities”, sets of merchandise, given away for free or sold cheaply as promotional tool (the idea being the continuity of the customers returning).

1375–1425: From the late Middle English continuite (uninterrupted connection of parts in space or time), from the Old & Middle French continuité, from the Latin continuitatem (nominative continuitās) (a connected series (the construct being continu(us) (continuous) + -itās (equivalent to the English continu(e) +‎ -ity), from continuus (joining, connecting with something; following one after another) from the intransitive verb continere (to be uninterrupted (literally “to hang together”).  The –ity suffix was from the French -ité, from the Middle French -ité, from the Old French –ete & -eteit (-ity), from the Latin -itātem, from -itās, from the primitive Indo-European suffix –it.  It was cognate with the Gothic –iþa (-th), the Old High German -ida (-th) and the Old English -þo, -þu & -þ (-th).  It was used to form nouns from adjectives (especially abstract nouns), thus most often associated with nouns referring to the state, property, or quality of conforming to the adjective's description.  Continuity is a noun, continuance, & continuousness are nouns, continue is a verb, continuous & continual are adjectives and continually is an adverb; the noun plural is continuities.

The adjective continuous (characterized by continuity, not affected by disconnection or interruption) dates from the 1640s and was from either the French continueus or directly from the Latin continuus.  The verb continue (was in use by at least the mid-fourteenth century) in the form contynuen (maintain, sustain, preserve) which by the late 1300s has assumed the meaning “go forward or onward; persevere in”.  It was from the thirteenth century Old French continuer and directly from Latin continuare (join together in uninterrupted succession, make or be continuous, do successively one after another), from continuus.  The sense of “to carry on from the point of suspension” emerged early in the fifteenth century while the meaning “to remain in a state, place, or office” dates from the early 1400s, the transitive sense of “to extend from one point to another” was first documented in the 1660s.  The word entered the legal lexicon with the meaning “to postpone a hearing or trial” in the mid fifteenth century.

The noun continuation (act or fact of continuing or prolonging; extension in time or space) dates from the late 1300s, from the thirteenth century Old French continuation and directly from the Latin continuationem (nominative continuatio) (a following of one thing after another), a noun of action from past-participle stem of continuare.  The adjective continual was from the early fourteenth century continuell (proceeding without interruption or cessation; often repeated, very frequent), from the twelfth century Old French continuel and directly from the Latin continuus.  The noun continuance (perseverance, a keeping up, a going on) dates from the mid-fourteenth century, from the thirteenth century Old French continuance, from continuer.  Continuance seems to have been the first of the family to appear in the terminology of legal proceedings, used since the late fourteenth century in the sense of “a holding on or remaining in a particular state”, in courts this by the early fifteenth had extended to “the deferring of a trial or hearing to a future date” and in some jurisdictions lawyers to this day still file an “application for continuation”.  The now widely used discontinuation (of legal proceedings; of a product range etc) has existed since at least the 1610s in the sense of “interruption of continuity, separation of parts which form a connected series” and was from the fourteenth century French discontinuation, from the Medieval Latin discontinuationem (nominative discontinuatio), noun of action from past-participle stem of discontinuare.

Page 1 of IMDb's (Internet Movie Database) listing of discontinuities in Mean Girls (2004).

A discontinuity: In Mean Girls, a donut (doughnut) appeared with a large bite taken from it while a few seconds later it had endured just a nibble.

In film production, the job title “continuity girl” seems to have been retired in favor of “continuity supervisor” or “script supervisor”, one of the terms culled in the process of gender neutrality which also claimed most of the “best boys” (they’re now styled with titles such as “assistant chief lighting technician” or “second lighting technician”.  Whether myth or not, the industry legend is the “best boy” job title really did begin with the request “give me your best boy” although that wasn’t something as ominous as now it may sound.  The first known reference to a continuity girl in a film’s credits was in the US 1918 and the job involved ensuring the “continuity” (in the industry “scenario” is synonymous) of the final cut appeared as a seamless narrative.  The job was required because although a single scene in a film might appear to be a contiguous few minutes, the parts assembled in the editing process to produce it may be made up of takes shot days or even months weeks and possibly in different places.  Among a myriad of tasks, what a continuity girl had to do was maintain a database with the details of each piece of film (vital for the editing process) and ensure the details of each shot (clothes, haircuts, props (including their exact placement) and environment (climate, time of day etc) are in accordance with the previous footage.  The detail can be as simple as the time displayed on a wall clock and it matters because there’s a minor industry of film buffs who go through things frame-by-frame looking for discontinuities, all of which gleefully they’ll catalogue on various internet sites.

Three covers used for Leah McLaren’s The Continuity Girl (2007, left); not all Chick lit titles used vibrant or pastel shades in the cover art.  The Continuity Girl (2018, right) by Dr Patrick Kincaid (b 1966) is an unrelated title.

The Continuity Girl (2007) was the debut novel of Canadian journalist Leah McLaren (b 1975), the protagonist being a continuity girl named Meredith Moore.  A classic piece of Chick lit (the construct being chick (slang for “a young woman” + lit(erature)), a now unfashionable term describing novels focused on women and their feelings) the plotline involves Ms Moore’s biological clock tick-tocking to the psychological moment on her 35^th birthday: she wakes up feeling a sudden acute yearning for a baby.  In a Chick lit sort of way, her solution was to leave her predictably pleasant Canadian life and head for London where she plans to select a man on the basis of her assessment of his genetic suitability for breeding, seduce him and, in the way these things happen, fall pregnant.  Things of course don’t work out quite that effortlessly but, being Chick lit, there’s much self-realization, self-discovery and self-expression on the path to a happy ending.

In political science, “continuity theory” is an approach (in two aspects) to twentieth century German historiography which focuses on structural and sociological continuities between eras (including pre-twentieth century influences and traditions).  The first aspect was the notion there existed “continuity” in the persistent influence of long-term social, political, cultural, and institutional developments in German history, dating at least from the time of Martin Luther (1483–1546) contributed to the particular nature of Imperial Germany (1871-1918), the failure of the Weimar Republic (1918-1933) and the Führerprinzip (Leader Principle) which, structurally, was the distinguishing feature of the Third Reich (1933-1945).  This idea has underpinned a number of major historical studies but has always been contested because another faction (which has at times included a significant proportion of the German population) which argues that Nazism was uniquely radical and an aberration in the nation’s history.  Most controversially, some proponents of continuity theory extend the application to the post war years, examining how former Nazis, neo-Nazis and their ideologies persisted (and at times have flourished) both in the FRG (Federal Republic of Germany; the old West Germany (1949-1990)) and the unified state formed 1990 after the FRG absorbed the GDR (German Democratic Republic (the old East Germany)).

Adolf Hitler (left) looking at Ernst Röhm (right), Nürnberg, 3 September 1933.  Some nine months later, Hitler would order Röhm's discontinuation (murder).  Photograph from the Bundesarchiv (Federal Archives), Bild (picture) 146-1982-159-22A.

The theory’s other aspect was structural and was essentially an analysis of the extent to which the Nazi state operated under the constitutional and administrative arrangements inherited from the Weimar Republic, the state which Adolf Hitler (1889-1945; Führer (leader) and German head of government 1933-1945 & head of state 1934-1945) claimed “his” National Socialist revolution had overthrown.  The indisputable fact that the Nazi dictatorship was fundamentally different from Weimar at the time obscured the continuity but maintaining the Weimar constitution was hardly unique.  Hitler choose also to adapt the existing mixed economic model, something which upset some of the more idealistic souls in his movement who had taken seriously the “socialist” bit in “National Socialism” and led to the infamous Nacht der langen Messer (Night of the Long Knives), also called Unternehmen Kolbri (Operation Hummingbird) a purge executed between 30 June-2 July 1934, when the regime carried out a number of extrajudicial executions, ostensibly to crush what was referred to as “the Röhm Putsch” (Ernst Röhm (1887–1934; chief of the Sturmabteilung (the stormtroopers (the SA)), head of the four-million strong SA had certainly in the past hinted at one but there’s no doubt no such thing was imminent).

The USGS’s (US Geological Survey (1879)) depiction of the Mohorovičić discontinuity (the Moho).

The Mohorovičić discontinuity (which geologists tend to call “the Moho”) is the boundary between the Earth's crust and mantle, the extent defined by the distinct change in velocity of seismic waves as they pass through changing densities of rock.  The phenomenon is named after Croatian geophysicist Andrija Mohorovičić (1857–1936; one of the seminar figures in modern seismology), who first published his findings (based on seismographic observations of shallow-focus earthquakes) in 1909.