Monday, April 29, 2024

California’s Zero-Emission Train Regulations: End of the Line for Trains?


As polluters go, diesel-electric trains could be a lot worse.  A post on the website of the Institute for Energy Research says that it takes only a gallon of diesel fuel to move a ton of freight 500 miles by train, whereas if you put the same load in your one-ton pickup that gets 15 miles per gallon, or even a semi-trailer that does somewhat better, you will be making a lot more greenhouse gas with the trucks than with the train. 


But that hasn’t deterred the California Air Resources Board (hereinafter CARB) from issuing a set of proposed regulations that would effectively shut down diesel-locomotive-pulled trains, not only in California, but quite possibly everywhere else in the U. S. as well.  How would it do this?


First off, the regulations are not completely out of touch with reality.  The creative types who came up with them recognize that there are not yet any full-scale zero-emission locomotives anywhere in the world, not even in secret labs owned by Elon Musk.  So starting in 2026, all train companies will start having to pay into escrow almost a billion dollars each in order to save up to buy these zero-emission (presumably battery-powered) trains that don’t exist today, and may not exist for decades to come, either. 


Besides bankrupting small train lines, this will create an economic burden that will raise prices nationwide and put rail transport at a disadvantage that may force more shipments onto truck lines, where they will end up causing more pollution than if the CARB had just sat on its hands and done nothing.


And not all train traffic happens inside California, either.  A lot of it carries goods between that state and the rest of the country, and no one thinks that huge switchyards will spring up on the border of the state to change out nasty polluting diesel engines for electric ones to run inside the state.  In fact, due to a kink in the original Clean Air Act of 1972, California has a unique privilege to see that its own internal CARB regulations automatically trump any federal regulations, unless someone shows (typically through costly and lengthy litigation) that the CARB regulations are unreasonable.  And because California is such a large market, a regulation that is in force there typically has to be accepted by default elsewhere.  This is exactly how California automobile pollution standards, which were much stricter than either existing Federal or other state standards, became the de-facto U. S. standard. 


And now California is trying to do the same thing with their rail-transportation rules.

According to a report in National Review, during a public-comment period that ended Apr. 22 a huge variety of organizations protested the proposed regulations.  These range from the expected (train companies, state and local legislators) to the unexpected (railway labor unions) and downright surprising (two Federal agencies opposed it). 


As written, starting in 2030 the regulations require that all locomotives operating in the state must be less than 23 years old, obsoleting many perfectly good engines that can last for 40 years or more.  By that same year, only six years from now, half of all new locomotives must be zero-emission, and by 2035, all new locomotives must be electric (or nuclear, or “Back to the Future” flux capacitors, or whatever). 


In 1958, during Mao Zedong’s Great Leap Forward, that dictator decided that China had to become the world’s largest producer of steel, within five years.  The only sensible way to achieve that goal was to study the current large-scale steel industry, figure out what factories and people and training and expertise would be needed, and spend the money it would take to buy the equipment and build the steel mills and blast furnaces to do the job.


But that is not what Mao decided to do.  Instead, he called on his citizenry to build “backyard furnaces,” typically a few yards (or meters) in diameter, made of mud bricks and fueled by wood or charcoal.  In essence, he asked billions of people to take up steelmaking as a hobby, only a deadly-serious one.  So many people were compelled to abandon useful pursuits like farming in order to make backyard furnaces that some authorities think it contributed significantly to the Great Chinese Famine of 1959-1961, in which an estimated tens of millions of people died.  And the pig iron that the peasants managed to make was so poor in quality and small in quantity that the whole thing was abandoned a few years later.


The backyard-furnace fiasco is a good example of what happens when a person or organization without the ordinary common sense that (as my grandmother would say) God gave a soda cracker, is endowed with dictatorial powers.  The looming disaster awaiting U. S. railways if the CARB railway regulations about zero-emission trains are enacted bears more than a family resemblance to Mao Zedong’s ill-fated backyard foundries. 


At least people knew how to make steel, and it was a proven technology.  It just wasn’t practical for millions of Chinese peasants to make it on an absurdly small scale with no modern equipment, quality controls, or modern transportation. 


It is provably impractical—presently impossible—to make a free-standing electric locomotive that runs on batteries and does what a modern diesel-electric unit does.  But that hasn’t stopped the dictators at CARB from cooking up a regulation which, in the best case, will cost U. S. rail companies millions of dollars to fight in court, and billions to comply with in escrow funds in the meantime even if a zero-emission locomotive never comes to pass. 


With the proposed CARB railway regulations, we have arrived at the dictatorship of the administrative state.  It is no longer merely a future threat—it is here, right now, standing with a battle-ax poised over the neck of the U. S. railway industry.  It passed through my mind to encourage the railways to simply refuse to service California once the regulations are in place.  See how they like it without trains.  This would probably provoke a Federal takeover of the industry, as it did during the Wilson administration in World War I, and the only advantage then would be that the dictatorship would be out in the open for all to see.


But it is already, and I only hope that this ends better than Mao’s backyard furnaces.  Right now, I’m not optimistic. 


Sources:  The Institute for Energy Research article “California Proposes to Ban Diesel Trains and Has Asked EPA For a Waiver” appeared on Mar. 29, 2024 at  The National Review article “California vs. the World on Zero-Emission Trains” by Dominic Pino appeared at  I also referred to the Wikipedia articles “Backyard furnace” and “Great Chinese famine.”

Monday, April 22, 2024

Does Bitcoin Use An Immoral Amount of Energy?


The business of cryptocurrency turns out to be one of the more power-hungry forms of market speculation.  An article in the April 2024 issue of Physics Today says that between 0.6% and 2.3% of the total electricity production in the U. S. goes to cryptocurrency mining farms.  Is this a bad thing, and if so, what can be done about it?


A helpful review of the history of cryptocurrency is found in the surprisingly entertaining 2020 book Money:  The True Story of a Made-Up Thing by National Public Radio reporter Jacob Goldstein, who points out that one of the main attractions of physical currency (paper bills and coins) is its anonymity.  No one can tell where a $100 bill has been, and so that's why illegal transactions around the world favor briefcases full of large-denomination bills. 


Goldstein describes how after the rise of the Internet, "techno-libertarians" tried to develop a digital equivalent of cash, free of the need for banks and creditors and debtors to keep track of who has transferred what amount of money.  After several "cypherpunks" came up with pieces of what was needed, an anonymous person (or group of persons—no one knows exactly) calling himself Satoshi Nakamoto put it all together in a paper sent to other cypherpunks on Halloween, October 31, 2008. 


Goldstein calls the entity which eventually became known as bitcoin "an anonymous(ish), money(ish) thing that buyers and sellers could exchange over the internet without any bank or tech company in the middle."  After a very slow start, including the first-ever purchase paid for with bitcoin in 2010 (someone sent a tech nerd a pizza in exchange for 10,000 bitcoins, which were then worth about a third of a cent each), the criminal element discovered that bitcoin was ideal for international illegal transactions involving illicit drugs.  Bitcoin started to rise in value, and as the code for bitcoin was openly published, imitators started to create their own versions.


But as with many network-based phenomena, the first to get in with a usable product tends to dominate, and today bitcoin is responsible for about half the total market in cryptocurrency.  Lately it has been trading at around $72,000 per bitcoin, which would make that 2010 pizza worth $720 million at today's prices. 


As Goldstein points out, most items used over the centuries for money have been either relatively difficult to obtain, or else governments have strictly enforced laws to prevent counterfeiting.  Nakamoto chose to make bitcoin intrinsically hard to create by embodying digital puzzles that must be solved before new bitcoins can come into being.  The custody of the master code has now been taken over by a 57-member Bitcoin Mining Council, which has adjusted the difficulty of the puzzles to keep up with advances in computer technology so that nobody has been able to flood the market with bitcoins, at least so far.  And the code is set up so that no more than 21 million bitcoins will ever exist.


The price of all these restrictions is that to make a new bitcoin requires huge computer installations, such as the 700-MW-rated-consumption unit in Rockdale, a small community in Central Texas.  In 2023 that much power produced almost 7,000 bitcoins.  The mining analogy is apt, because as the Physics Today article points out, the estimated global energy consumed in cryptocurrency mining is 163 TWh (163 with 12 zeroes behind it), comparable to the estimated 132 TWh consumed worldwide in gold mining.  Both enterprises require a great deal of work to produce a commodity whose price is unstable, and a sudden dip in price can render either a gold mine or a bitcoin mine useless.  But risk-averse people generally don't fool with mining investments in the first place.


Cryptocurrency doesn't have to consume huge amounts of power.  One alternative version, Ethereum, changed its algorithm in 2022 to something called "proof of stake," which exchanges puzzle-solving for putting up one's own stock of cryptocurrency as collateral in order to do the necessary digital work to maintain the blockchain process, which by itself is not that burdensome.  Ethereum thus reduced its energy consumption by 99.9%.


As an attempt to replace physical cash, bitcoin and its allied cryptocurrency creatures are a failure.  One of the prime features of the U. S. dollar is its relative stability in value as measured by what it will purchase.  Even minor upticks of 5 or 10 percent annually, as we saw in the last few years, lead to fierce political blowback and can endanger whole administrations.  So no one without a very good (and probably illegal) reason to do so is going to use a commodity for routine transactions like bitcoin, whose value bounces around like a kangaroo. 


Instead, cryptocurrency has found its niche in the spectrum of other commodities traded primarily for speculative purposes.  Most economists consider speculation a basically unproductive activity, because it tends to be a zero-sum game.  If A makes a killing on the stock market, you'll surely find that B, C, and a lot of other letters lost at least that much, unless a lot of leveraging is going on, in which case we get into fractional-reserve banking theory, and that's a whole other column.  A society can tolerate a certain amount of financial speculation, but at least gold mining leaves you with something physical that you can wear or plate electrical contacts with.  When your bitcoin investment turns sour, it's gone into the bit void, never to return.


People do all sorts of things with their money, and as long as what they are doing with it is not intrinsically illegal, I don't see a large problem with bitcoin mining compared to all the other nasty things that we have to put up with these days.  Other things being equal, I wish they'd redesign their algorithm to use less power, but it might rock the boat too much and leave every investor with little or nothing.  But hey—it's only bits anyway.


Sources:  Jacob Goldstein's Money:  The True Story of a Made-Up Thing by Jacob Goldstein (New York:  Hachette, 2020) is a treasury (so to speak) of little-known facts about money and a pretty good guide to how it works, including the Federal Reserve System.  Physics Today carried the article "Code changes could drastically reduce bitcoin's enormous energy requirements" by David Kramer on pp. 26-29 of the April 2024 issue.

Monday, April 15, 2024

It's Time to Ban Social Media on Smartphones for Children and Adolescents


In the May issue of National Review, San Diego State University psychologist Jean Twenge presents smoking-gun data that shows the manifold harms to children and teenagers caused by smartphones, specifically social-media use on them.  She claims, and I agree, that we have to do more to alleviate these harms, by government intervention if necessary. 


First, the harms.  Twenge has collected data on a wide number of measures of wellbeing including sleep patterns, socializing, indicators of loneliness and depression, and participation in adult activities.  Significant shifts in all these data have occurred over the last five decades. 


In-person socializing, measured as the percentage of U. S. teens going out with friends twice a week or more, was reasonably steady until about 2008, when it began to decline, and fell off a cliff around 2012, falling from 80% in 1976 to around 55% in 2021 for 12th-graders.


The percentage of 8th, 10th, and 12th graders sleeping less than seven hours a night was about 35% from 2003 to 2013, when it abruptly took off and rose steadily to 50% by 2022. 


The percentage of U. S. 12- to 17-year-old girls suffering major depression in the past 12 months was steady at 12% until 2011, and then went through a similar rise to almost 30% by 2021.


And the percentage of 15-year-olds measuring "high" in loneliness in regions as disparate as Asia, Latin America, Europe, and English-speaking countries all show a sharp uptick when?  Three guesses and the first two don't count:  2012.


What happened in 2012?  It was the year that the number of smartphone users in the U. S. crossed 130 million on its eventual way to the current number of 316 million, out of a population of about 330 million.  Also, the number of active Facebook users crossed the 1 billion mark worldwide that same year. 


Twenge, wearing her good-scientist hat, proposes other possible causes for these dismal statistics about teen wellbeing:  anxiety over college debt, the opioid crisis, even global warming.  None of them pass muster.  Her close study of the detailed behavior patterns of teens regarding smartphones reveals that the average U. S. adolescent spends nearly five hours a day on social media.  That's more than a half-time job, seven days a week. 


Anyone observing teens in the wild can confirm that their faces are stuck to their phones at every possible moment—in an elevator, walking down the street, at mealtimes with or without other family members, and evidently late at night too.  As for the other possible causes Twenge diligently considers and rejects, there is no such thing as mathematical proof in psychology, but she has come as close as anybody can to proving that social media use on smartphones has had a huge, and largely negative, influence on the daily lives of teenagers. 


Granting the validity of her case, what is to be done about it? 


Leaving teenagers in the gentle hands of the social-media companies is like leaving the hens in the gentle paws of the fox.  Some of the world's most sophisticated and effective AI software drives teens to keep clicking and scrolling on infinite websites, because the firms' profits depend on their doing so. 


Asking parents to control their teens' use of smartphones is nice in theory, but one would have to be a literal helicopter parent to do that effectively, hovering over each child's shoulder every waking minute of the day.  Yes, there is software to block certain sites, but teens know ways to evade such restrictions, and it's simply impossible for even highly conscientious parents to monitor and censor every last thing a child does with his or her phone. 


Twenge proposes a straightforward ban on social media use for everyone under 16.  While the brain of a sixteen-year-old has still got a lot of maturing to do, this age represents a compromise between exposing highly vulnerable young people to the harmful effects of social-media use and keeping them from using it when they are mature enough not to be significantly harmed by it.  While an outright ban is still in the future, a number of states (Texas, Louisiana, Arkansas, an Utah) have passed laws requiring that firms obtain parental permission before allowing people under 16 to get social media accounts. 


In many ways, this issue has parallels with the way attitudes and laws concerning smoking changed during the last part of the twentieth century.  Once a near-universal social habit, smoking was first revealed to be a leading cause of lung cancer.  Then when we found that cigarette companies had engaged in a concerted effort to deceive the public, their reputation suffered further.  The banning of cigarette ads from TV and radio in 1971 began a general social trend that gradually changed smoking from a normal activity to one engaged in by a decided minority of people, but only after years of adverse publicity, revelations of corporate wrongdoing, and contested legislation.


Largely because of the profits involved, we can expect a similar battle over an all-out ban on social media for teens.  In this case, however, the people most affected can't directly influence legislators, not being old enough to vote.  It is up to parents and others concerned about the wellbeing of the next generation to organize opposition to powerful entrenched interests backed by billions of dollars.  And even if our small-r republican system of government was in proper working order, this would be a hard fight. 


Fortunately, protecting children and adolescents from psychological harm has not become a partisan issue—yet.  Both Democrats and Republicans can understand the need to keep social-media firms from exploiting populations who suffer harm all out of proportion to their numbers.  Twenge and her fellow social-science colleagues have given us all the proof we need to take action.  Now all that is needed is the courage and diligence to see it through.


Sources:  Jean M. Twenge's article "Ending the Tyranny of Smartphones" appeared on pp. 34-38 of the May 2024 issue of National Review, and relies on data presented more fully in her latest book Generations (Atria Books, 2023).  I also referred to data from the following websites:,, and 


Monday, April 08, 2024

Havana Syndrome: Is It Real, and Who's Doing It If So?


For nearly a decade, there have been isolated reports of strange health problems in U. S. diplomatic and espionage personnel stationed in sensitive parts of the world such as Cuba, China, and Vietnam.  Although there is no typical case, there are some commonalities in many of the cases.  The symptoms usually have a sudden onset.  Victims describe hearing strange noises, feeling severe pain in the head and elsewhere, and other neurological symptoms.  Some of them have proved to sustain serious brain-trauma injuries and suffered chronic debility from the attack.  Some victims have been struck inside offices or hotel rooms, while others were outside—one attack allegedly occurred on The Ellipse in Washington, D. C. 


Of course, U. S. government investigations into these incidents have sought to determine several things, including (a) whether the attacks are real, or simply a product of psychological stress and conventional illness, and (b) if they are real, what is causing them.  The matter is complicated by the fact that diplomatic issues are involved, as well as national prestige. 


A recent year-long investigation by news organizations including the web-based Insider, Germany's Der Spiegel, and CBS's 60 Minutes revealed on Mar. 31 that there is strong circumstantial evidence pointing to Russian operatives who have been seen in the vicinity of many of the attacks.  Although no "smoking-gun" evidence such as hardware or caught-in-the-act scenarios have come to light, the Russians are known to be researching directed-energy weapons, which the U. S. and other countries have already deployed in certain areas. 


Directed-energy weapons work by generating powerful radio-frequency or microwave energy and directing it in a concentrated beam toward a target.  (There are also weapons of this kind that use infrared or visible laser beams, but those are easily blocked by walls and are probably not being used in these cases.)  Depending on the power level and the nature of the target, the results of an attack can range from simple heating to crippling damage in the case of a hardware target such as a missile, or severe physical injury in the case of a biological organism. 


One problem in trying to discover material on this topic is that no one who has a working unit wants to brag about what it can do.  Undoubtedly, many animal studies have been done in this area, but to my limited knowledge there is very little on it in the open literature.


Besides that, the U. S. government, or at least some people in it, seem reluctant to name names even if they do have strong evidence that, for example, Russian spies are causing most of the Havana-syndrome cases.  National Review reports that the Office of the Director of National Intelligence said as recently as a year ago that they thought enemy action as a cause of Havana Syndrome was "very unlikely."  And Sen. J. D. Vance's reaction to the Mar. 31 news reports was dismissive, to say the least—he said it felt like "a lot of journalists have lost their minds." 


As a microwave engineer, I admit that this whole controversy inspires in me a sense of frustration, because the one thing that is true about directed-energy weapons is that they are extremely easy to detect, given the proper equipment.  Unfortunately, depending on the nature of the weapon, the proper equipment can be costly and inconvenient to use.


There are wideband radio receivers that can sense radiation ranging in wavelength from below the AM broadcast band (roughly 0.5 to 1.5 MHz) well into the microwave region (3 to 30 GHz, billions of Hz).  But if the energy is powerful enough (and it would have to be to cause the symptoms that victims report), the receiver doesn't have to be complicated at all.  A set of wideband printed antennas going to detector diodes monitored by a low-power (but well-shielded!) microprocessor could form an electronic version of the old radiation badges that used to be worn at all times by workers in nuclear reactors (and still may be, for all I know).  And produced in enough quantity, these units could cost under a kilobuck each, possibly much less.


The point is, if we are looking for conclusive proof of both the cause of these attacks and the fact that they do indeed occur, a fairly small amount of engineering effort would result in an abundance of data in case anyone wearing such a sensor was attacked.  This project would cost something, but the lives of diplomats and other personnel abroad are worth something too.


But no technical solution that ends up getting used by people is purely technical.  Someone has to need it enough to make it and deploy it.  And there are abundant indications that in this situation, as with many other issues relating to the U. S.'s relationship, such as it is, with Russia, the administration seems eager to smooth over issues that arise rather than taking firm countermeasures.  If such smoking-gun knowledge that portable directed-energy monitors could provide is something that the U. S. government doesn't want to know, the U. S. government isn't going to go to the trouble of looking for it. 


To my mind, this is a dereliction of duty to protect your own people from harm.  At least one diplomat resigned his post rather than run the risk of suffering an attack similar to what several of his colleagues received.  When things get this serious, it seems that any technical means available should be taken to protect people against these attacks, and getting hard evidence of them first would take us a long way toward that goal.


As more news about Havana Syndrome becomes available, political pressure to do something may change some minds in the government where it counts.  But for all the public knows at this moment, our diplomats and other personnel abroad are sitting ducks, waiting for another directed-energy-weapon attack. And figuring out what these attack are and who is doing them is the first step toward preventing them.


Sources:  The reaction of J. D. Vance and other government officials to the Mar. 31 news reports appeared in an article by Noah Rothman in National Review's website at  The very lengthy report on Havana Syndrome published Mar. 31 by Insider is at  I also referred to the Wikipedia page on Havana Syndrome, which (unique in my experience) has been locked by Wikipedia management to prevent malicious editing until Apr. 19. 

Monday, April 01, 2024

Key Lessons of the Key Bridge Collapse


Some accidents are simple:  two cars collide on a freeway, a tree falls on a jogger, lightning hits a golfer.  Others require a chain of events, each of which is unlikely, and so are much rarer than the simple kind.  The sequence of occurrences, each one fairly harmless by itself, which led to the collapse of the Francis Scott Key Bridge in Baltimore Harbor on last Tuesday, March 26 included things that by themselves would cause few if any major problems.  But on that fateful night, they all aligned to end four lives and cause what will eventually turn out to be billions of dollars in direct and indirect damage.


About forty-five minutes after midnight, the Singapore-registered container ship Dali left its berth at the Port of Baltimore bound for Sri Lanka.  Its route lay beneath the second-longest continuous-truss bridge in the U. S., the Key bridge, which carried traffic around the southern part of the Interstate 635 loop around Baltimore, and was the last bridge to pass under before the Dali reached the open sea.  On the bridge, a construction crew was repairing potholes resulting from the previous winter.


Some time after leaving port, the Dali began to experience engine trouble.  Security-camera videos recovered afterwards show that the ship's lights flickered on and off several times and black smoke began to come from the stacks.  As a recent NBC News report shows, contaminated bunker fuel is a serious problem in marine shipping circles.  As the giant propulsion engines are separate from the smaller diesel engines that run a ship's generators, and both were affected, some experts have speculated that contaminated fuel may have caused the ship's power problems, as that is a common factor that would account for both difficulties.


Whatever the cause, the ship's crew was alert enough to issue a mayday call by radio, which was picked up by first-responder officials, and they issued orders for traffic to be blocked on the bridge. 


Less than two minutes later, the now-adrift ship plowed into one of the two main "bents" supporting the highest span of the bridge.  A cloud of masonry dust can be seen on the video of the collision, shortly before the support fails and the entire truss structure breaks up and falls into the ocean.  Two construction workers on the bridge were rescued, but six others remain missing and were presumably killed.  While our prayers go out to those who lost loved ones and friends, the accident could have caused many more fatalities if it had happened during an afternoon rush hour with hundreds of vehicles on the bridge.


Several relatively unlikely things had to happen together for this tragedy to take place.


As it turns out, engine problems and failures due to contaminated fuel are not that uncommon.  Propulsion engines of the type used on the Dali can have up to fourteen cylinders, each over a yard (~1 meter) in diameter and with a stroke of eight feet (2. 5 meters), and the amount of fuel used is phenomenal.  So shippers are motivated to find the cheapest fuel around that will run the engines, and so-called bunker fuel is used.  It is thicker and heavier than the type of diesel fuel used in passenger cars, and because suppliers sometimes cut corners and mix adulterants in the fuel to cheapen it, it's not uncommon for ships to lose power from bad fuel.


We still don't know the exact cause of the power loss, but the vast majority of such events occur in the open sea where a drifting ship represents lost time and money, but is not otherwise dangerous.  The Dali had the bad fortune to lose its power in the worst possible place:  a few hundred yards away from a vulnerable bridge.


Why wasn't the bridge structure protected from such collisions?  It doesn't take a genius to guess that sooner or later, a ship might lose control and bang into a support.  Not being a maritime bridge architect, I can't answer that question.  As the bridge was built in 1977, it withstood nearly half a century of wear and tear from weather, traffic use, and shipping.  It's an open question whether the builders tried to estimate what it would take to fend off a straying ship colliding with the supports.  As there are so many variables—the size and weight of the ship, its velocity, exactly where it would hit—the designers may have just tried to make sure smaller ships couldn't damage it and hoped that the pilots of the larger ships would be equipped with radar and other navigational aids to miss the bridge supports. 


And until last Tuesday, every ship capable of knocking down the bridge succeeded in missing them.  But the unlikely event of a ship losing power and having just the right combination of weight, ocean currents, and momentum to wreck the bridge finally came up, and the result is as we see.


Again, we can be thankful that the main losses are monetary rather than in the form of injuries and many fatalities.  This accident could have been much worse, and the ship's crew and first responders deserve credit for issuing maydays and blocking traffic as promptly as they did. 


But for the foreseeable future, anyone wanting to drive around Baltimore is going to have to do it without the benefit of the Key Bridge, and until the wreckage is cleared, the Port of Baltimore is shut down.  As disasters go, this one was spectacular, but way down the list of fatal accidents compared to other mechanical failures that killed many more people. 


We can be sure that the next bridge will have more protection from ship collisions, whatever else is taken into consideration.  And this accident may shine a light on the dubious quality of bunker fuel used in maritime service, an international market with poor quality-enforcement mechanisms, according to the NBC News report.  These are good things, and while any accident is regrettable, the lessons we learn from them benefit the next generation of designers and users of the built environment. 


Sources: I referred to an NBC News report on bunker fuel quality as a possible cause of the accident at, a CBS News timeline at, and the Wikipedia articles on the Francis Scott Key bridge collapse and the maritime Wärtsilä-Sulzer RTA96-C engine, the largest reciprocating engine in the world.