After his junior year, his parents divorced
— Chris was surprised;
they never argued
— and any overt power his father held over him vanished.

“I said, ‘You no longer have the right to tell me what to do with my life,’” said Chris.

“You’ve been giving me a hard time for not doing what I’m supposed to do,
and now you’re not doing what you’re supposed to do.”

He’d finished high school a year early and a decision presented itself.

“The big question for my father was, would I go to Harvard or would I settle for Princeton,” said Chris.

“And I told him that I wanted to work in a factory.

And he said, ‘I’m not paying for you to go to college so you can get a job at an auto plant.’

So, I thought about it and decided, ‘What do I need college for?’”

He joined a group whose goal, quaint as it sounds today, was to train smart young people to organize workers.

“The idea was to make the unions more responsive,” he said.

Along with a small crowd of like-minded young people,
he bounced from an oil refinery outside Los Angeles to a UPS warehouse inside Los Angeles to an auto factory in Detroit
and, finally, to a coal mine in West Virginia.

“It wasn’t that I was going to be the leader or anything,” he said.

“It was helping working people make use of their own power.”

The more time he spent with actual working people, the less plausible his self-assigned role seemed
— and not just to him.

By the time he arrived in West Virginia, he had only two other young revolutionaries by his side
— and they both took one look at their new jobs and fled.

Neither of them had had any idea of what a coal mine looked like, either.

His arrival in West Virginia coincided with something else:

a call from home to tell him that his mother had died by suicide.

(He never mentioned this to me. I learned it from a former colleague of his father’s.)

Chris went home for two days … and then returned to the coal mine in West Virginia.

He was now 19 and nearing the end of a romantic mission to revolutionize the life of the American worker.

The main effect of the previous three years had been to alienate his father.

(When his father told a friend of the curious path that Chris had put himself on,
the friend had said,
“You must be so proud of him.”

To which Robert replied, “I’d be proud of him if he was your kid.”)

He wasn’t organizing anything or even trying to.

He was sleeping in a trailer and working the graveyard shift at the Lightfoot No. 1 mine in Boone County, W.Va.,
alongside a bunch of guys who had grown up together.

It was as if he had flown halfway across the country to crash some random high school prom.

“I was never unaware of my outsider status for a moment,” he said.

“There was not a moment when I thought I fit in.”

Real-life American workers were different from his mental model of them.

“I had thought if they only knew what I thought, they’d see things how I do,” he said.

That idea now struck him as so obviously nuts that he didn’t bother to let them know what he thought.

His fellow coal miners were less concerned with his ideas about the economy and their rightful place in it than in simply making a living.

Their morale, at that moment, was actually sky-high.

“Coal was booming,” said Chris.

“We were going to save the world.

Thank god we have all this coal so we’re not reliant on Arab oil.

People felt good about themselves.”

Inside a West Virginia coal mine that politics had brought him to,
politics seeped out of him.

He was aware that his fellow miners must wonder why this stranger had turned up wanting to be a miner,
but they never asked him about it.

He returned the favor and didn’t pester them about their opinions.

“I’ve always thought that everyone has a right to think what they think,” he said.

But there were moments when he was reminded how different their world was from the one he’d grown up in.

The one time in the mine that someone brought up religion, for example.

“I broke my rule,” said Chris. “I said, ‘I’m, uh, actually an atheist.’

This other guy got this stricken look on his face, then looked up at the roof and said, ‘don’t say that in here!’”

Another time, Chris woke up for his night shift to hear on the radio that Mao Zedong had died.

“No one had the slightest interest in global affairs, but I thought, ‘I’ll try it.’”

He told a fellow miner the news.

“Who’s that?” asked the miner.

“He’s the head of China,” said Chris.

“Well, they won’t miss him, then,” said the miner.

“It’s standing room only over there!”

The premise of his radical youth was that people without power needed to be protected from the people with it.

But these coal miners weren’t asking for protection.

Their jobs were insanely risky,
but they seldom complained and at times even courted risk.

They routinely ventured beyond the pillars that prevented the mountain from falling in on them,
and into areas where the mountain floated over their heads without support.

They upped the odds of a methane explosion by smoking inside the mine.

“The way they judged a new boss was to whip out a cigarette and see if he said anything,” said Chris.

“If he said something, he was done.

He’d never be able to mine any coal.”

All of them knew people who had been killed mining coal.

Married couples learned to settle their arguments before the husband returned to the mine,
because they might never see each other again.

“Everyone had a tragedy,” said Chris.

Chris himself was twice nearly killed, and yet he never adjusted his behavior, either.

For reasons he could never fully explain, even to himself,
he loved being inside a coal mine.

“It was just so cool,” he said.

“You go down into a place most people think you are crazy to be.
And you like it.”

But a year into the job, his enthusiasm for the actual work flagged.

He didn’t really belong in West Virginia.

Everyone knew everyone else,
and he knew no one.

“It was like being an immigrant,” he said.

“You could be there your entire life and never fit in.”

Partly out of stubborn pride, he refused to even consider heading home.

He enrolled in Penn State instead, to study mining engineering.

His mother had left him some money.

His father, mollified that his son had returned to college, chipped in a bit more.

And Chris would help pay for his education
— by moonlighting inside coal mines as he studied.

His political interest in workers’ rights was morphing into a technical interest in their safety.

Coal mining had long been the most dangerous job in the United States.

At the height of the Vietnam War, a coal miner was nearly as likely to be killed on the job as an American soldier in uniform was to die in combat,
and far more likely to be injured.

(And that didn’t include some massive number of deaths that would one day follow from black lung disease.)

Up to that point in the 20th century, half of the coal miners who had died on the job
— roughly 50,000 people
— had been killed by falling roofs.

In his classes at Penn State, Chris saw at least one reason for that:

The coal mining industry had learned to see the problem as the cost of doing business.

His rock mechanics professor was a Polish aristocrat named Z.T. Bieniawski.

Bieniawski was a big personality and maybe a tad out of place in State College, Pa.

“He liked five-star hotels and flying first class,
and in a lot of ways we didn’t have that much in common,” said Chris.

“Whatever the highest level of Toastmaster was, he was it.”

There was the story, which Chris loved, of the time Bieniawski staged a formal dinner at the restaurant of the Nittany Lion Inn.

Bieniawski (summoning the waitress): Madam, can you recommend your finest bottle of red wine?

Waitress (after studying Bieniawski a beat): Sir, if you want my opinion, you shouldn’t be drinking at all.

But he was a fabulous professor
— the sort of teacher who got you thinking even when he didn’t mean to.

One day he lectured his students on the formulas used to design the pillars that supported the roofs of coal mines
— which of course sounds like a topic to light a fire under no one.

But it lit a fire under Chris.

He’d experienced roof collapse.

He knew that poorly designed pillars killed people.

Now he learned that the formulas used to create them were all over the map.

“A kid in class raised his hand,” said Chris.

“He asked, ‘which of these formulas is the right one?’”

As Bieniawski had created one of the formulas, the professor’s answer seemed almost modest.

“You need to use your engineering judgment,” he replied.

But that can’t be right, thought Chris.

Each formula implied a different pillar design than the others.

At most only one could be right.

When wrong, coal miners died.

Yet no one had figured out which formula was best or really even saw the problem.

“I said, this is the place for me!” said Chris.

He graduated in 1981 without a clear idea of where to go next.

He had a serious interest (mine safety)
but no obvious place to express it.

He worked for a spell with an engineering consulting firm in Chicago
but found it dull and beside the point.

He toyed with going to work as a field engineer for a coal mining company and even spent a summer in mines in Wyoming.

There he was reminded of the realities of a coal miner’s life.

“A guy says, ‘Let’s go to a bar.’

It’s 50 guys and one woman stripper.

He says, ‘Let’s go somewhere else.’

It was the exact same scene:
50 guys and one woman stripper.

It made me so depressed
— that’s all I need is to be one of those 50 fucking guys.”

Then Bieniawski called to say that he’d just received new funding for a PhD student.

He wanted Chris to be that student.

All Chris needed was a thesis topic.

The coal mining industry soon supplied it.

On Dec. 19, 1984, a roof collapsed inside the Wilberg Mine,
just outside of Salt Lake City.

The miners at Wilberg had been trying to break the world record for the most coal mined in a single day.

Nine senior officials from the mine’s owner, Utah Power and Light,
had entered the mine to witness history.

Suddenly, a fire broke out in one of the two main tunnels.

Before the executives or 18 working coal miners could escape,
the roof in the second tunnel collapsed and blocked their exit.

All 27 people wound up trapped inside an inferno.

It would take a year to recover their bodies.

And Christopher Mark thought:

If they’d figured out the right formula for their pillars, they’d all still be alive.

Imagine a cake in the shape of a giant rectangle.

It consists entirely of vanilla quick bread except for a single six-foot-thick layer of chocolate fudge in the middle.

Your assignment is to burrow into that layer of chocolate fudge and extract as much of it as you can without triggering a collapse of the cake over your head.

If you were a coal miner in possession of a longwall mining machine,
you would drill several narrow tunnels into either end of the exposed side of the cake,
directly through the chocolate fudge,
all the way to the other side.

To prevent the cake from caving in, you wouldn’t carve out all the chocolate;

you’d leave pillars of it inside the tunnels.

As these pillars are made from chocolate, and your goal is to extract as much chocolate as possible,
you face constant pressure to take more of them than is safe.

Then, facing the direction you came from, you’d use the longwall mining machine to cut your way through the chocolate and back to where you started.

That’s when the job becomes especially treacherous.

You are now moving back and forth across the entire cake,
removing essentially the entire layer of chocolate fudge
— which also happens to be the sturdiest layer of the cake.

The machine starts on one end of the wall and slices all the way across to the other
and feeds the chocolate it removes onto a conveyor belt that carries it out through the original entry tunnels.

The more chocolate fudge you remove, the more vanilla cake you’ve left over your head without anything to support it.

You’re now effectively carving out a roof over your head.

Lacking support, that roof will eventually collapse.

Happily, the mining machine has a makeshift roof on it
— a giant metal plate capable of supporting a lot of cake
— and so you are protected from any cake that falls from immediately overhead.

But if that happens, you’ll probably need to stop mining and flee.

Meanwhile, behind you, the cake is collapsing in on itself.

That’s expected.

If anything unexpected happens, you can scurry into your original entry tunnels and out of the mine

This is the first sort of disaster that Chris set out to prevent.

“Pillar Design For Longwall Mining”
would be the subject of his PhD thesis
and the title of his first paper.

Bad pillar design was killing longwall coal miners.

It’s what killed 27 people in the Wilberg Mine.

It had killed miners since longwall mining had been invented in the 1940s.

It had also cost the coal industry money.

By the time Chris turned his attention to its roofs,
the longwall coal mining industry was out of pocket $200 for every minute its mines were shut down by some roof collapse
— and a single roof fall could shut a mine for days.

“The same roof fall that can kill miners can also cost a lot of money,” Chris said.

And yet even though the coal mine industry had a huge financial incentive to figure out how to solve the problem, it hadn’t solved it.

But the problem was complicated.

It didn’t frame itself as a single problem but thousands of smaller ones.

Each mine was sufficiently different from every other mine that regulators felt compelled to devise rules specific to it,
almost as if each mine were its own little industry.

The deeper the mine, for example, the heavier the weight over its roof,
and the more support it would require.

Rock itself differed from mine to mine in diabolical ways, so there was no reliable way to measure the load the pillars needed to support.

“A mine is unlike any man-made structure,” said Chris.

“It’s not a designed environment.

Most of the material the structure is made from is kind of unknown.

With rock you don’t know what the engineering properties are
— what the loads are.

You have a problem that is really not an engineering problem,
but people were insisting on using an engineering mindset to solve it.”

There was a reason no one could agree on coal pillar formulas:

No one could agree how to measure the rock the pillars needed to support.

Preventing the roof from collapsing inside a coal mine was less like analyzing the stresses inside a Gothic cathedral than building one from scratch.

There was only one way to do it: trial and error.

“The science wasn’t there,” said Chris.

“It didn’t have a clear mathematical solution or a way to get one.”

He was driving my rental car through the West Virginia coal fields when he said this.

His father had taken care with his dress and appearance.

Robert Mark liked suits and bow ties and his white beard as tightly and neatly groomed as an Augusta green.

Chris wore a wrinkled uniform of flannel and jeans and a careless stubble that was closer to the Augusta rough.

After 40 years in the coal fields, he looks and sounds less like a Princeton kid than a West Virginia coal miner.

When he laughs, he reveals a hole where a molar should be.

Nothing about him is decorative;
everything serves some structural purpose.

He lives in a modest house in the Pittsburgh suburbs
and drives a 10-year-old Subaru Forester with a standard transmission.

In the presence of luxury, he was visibly uneasy
— the sort of person who, when offered filet mignon,
squirms a bit before saying he’d rather have a cheeseburger.

“We always told our kids there are two ways to be rich,” he said.

“One is to make a lot of money.

The other is to not want much.”

It was the kind of thing a father would say only if he’d figured out how not to want much.

From the moment we left the interstate,
we were on narrow back roads winding through towns half-populated by people with a talent for throwing leery glances at strangers.

One side of the road was usually bordered by a canal or a single railroad track
and the other by exposed layers of sedimentary rock containing a thin seam of coal.

The West Virginia coal fields were famous for their abundance of coal seams.

Seldom more than six feet thick, they were still everywhere and encouraged generations of small mine operators to dig into the closest mountain they could find.

Every couple of miles, we’d pass a mine that had been abandoned,
its infrastructure left in place.

Old cranes rose from beds of weeds.

Chutes that once carried coal still ran half a mile from the mouths of exhausted mines to rusting and empty shipping containers.

“Does anyone ever intend to remove any of this?” I asked,
as we passed what looked like a vast abandoned construction site.

“It’s hard to imagine,” he said. “There’s no money in it.”

When Chris arrived in coal country in 1976, there were roughly 250,000 coal miners in the United States.

There are now fewer than 70,000.

During this time, West Virginia has turned from the bluest state in the country to the reddest.

“My idea about how society changes has changed,” he said.

Public interest in preventing miners from being killed on the job has always tended to peak after a mining disaster
and then fade until the next catastrophe.

The U.S. Bureau of Mines was created by an act of Congress in 1910,
three years after 362 coal miners were killed in an explosion in a West Virginia mine.

The bureau was mainly a research facility, however, and lacked the authority to police the mining industry.

In 1941, a year after mine explosions killed hundreds of miners in West Virginia and Pennsylvania,
Congress gave the bureau the authority to enter mines and look around
— but not much else.

In 1952, a year after 111 coal miners died inside an Illinois mine, Congress required the industry to acknowledge every roof fall fatality and investigate the cause of failure.

In 1969, a year after 78 miners died in another explosion inside a West Virginia mine, Congress passed a new law that gave the bureau the power to punish safety violations with fines and even criminal charges.

In 1972, after 125 people were killed by a burst dam in a West Virginia coal mine, Congress,
suspecting that the Bureau of Mines had been largely captured by the industry it was meant to regulate,
encouraged the Interior Department to separate mine inspection and regulation,
and created a new agency called the Mining Enforcement and Safety Administration.

Five years later, after 15 miners died inside a coal mine in Kentucky, Congress changed the new agency’s name to the Mine Safety and Health Administration
and gave it even more powers.

It mandated quarterly inspections of every underground coal mine, for instance, to ensure it was following the safety rules.

The powers obviously were only as helpful as the safety rules.

And the safety rules had some problems.

In the late 1960s, roughly 200 American coal miners were dying on the job every year.

Half of those were killed by collapsing roofs,
and roughly half of those were killed while following the existing safety rules.

No one ever told Chris to invent better rules.

But before he even began to figure out better designs for coal mine pillars, he knew that was what he wanted to do:

He wanted to keep miners safe.

As he worked toward his PhD, he figured out that the only place to do it was inside the federal government.

The coal mining companies had largely dodged their responsibility.

Industry executives who visited Penn State made it clear to Chris that they viewed safety as a subject for wimps and losers.

And no one coal mining company was likely to fund the research that would benefit all coal companies.

Working on his thesis, right through the mid-1980s, Chris had offers to teach,
but he knew no university could guarantee him access to the mines he wanted to study.

“Plus, academia puts on a facade of being impartial but is in fact much more closely connected to industry than anything else,” he said.

“In some ways it is an arm of industry.”

He needed to find a job inside the federal government,
with either the Mine Safety and Health Administration or the Bureau of Mines.

The mine safety agency had been hit by the Reagan administration with a hiring freeze.

But the Bureau of Mines, still largely owned by the industry, had some money and knew about his research.

“I just kind of had an open door there,” said Chris.

“I’m not actually sure who even hired me.

I know I had one interview because I forgot a tie and had to stop off at Wal-Mart on the way to buy one.”

It was now 1987.

He was 31 years old, married and the father of a 1-year-old son.

He joined the bureau at its research facility outside of Pittsburgh.

Upon arrival, he sensed a certain wariness from his new colleagues.

No one else had a PhD.

No one else had studied with the great Bieniawski.

“They put me in a basement office that was way out of the way with a guy who was mentally unstable,” said Chris.

“Whenever I’d get a phone call, he’d start making these funny sounds.”

They also assigned him to the jobs no one else wanted
— week-long trips to gather data from coal mines in Kentucky.

None of it mattered;

he was the least likely human being on the planet to put on airs,
and what was pain to others was pleasure to him.

He didn’t even much care that his phone calls triggered at the desk beside him the honks of a braying donkey.

“I thought I’d died and gone to heaven,” said Chris.

“The idea of being able to spend weeks studying these longwall mines was fantastic.

And as soon as I got to the Bureau of Mines, I had no one to tell me what to do.

I even made up my own title:
Principal Roof Control Specialist.”

He began with the problem he’d been attacking in his still-unfinished PhD thesis:

roof collapse inside longwall coal mines.

Evaluating the safety of a coal mine roof was less like evaluating the safety of a suspension bridge than it was predicting the performance of baseball players.

No matter what you did, you were going to be wrong some of the time:

The best you could do was improve the odds of success.

And the way to do this was to collect lots of data from roof failures
and search for patterns.

Much later, he’d explain his approach in a paper:

“The very words ‘statistical analysis’ seem foreign to many in rock engineering.

Engineers are trained to see the world in terms of load and deformation,
where failure is simply a matter of stress exceeding strength.

Statistics are generally given short shrift in engineering curriculums,
and so the entire language of statistics is unfamiliar.

Yet statistics are the tools that science has developed to deal with uncertainty and probability,
which are both at the heart of mining ground control.”

His new job came with a badge that granted him access to any mine he wished to study.

The Bureau of Mines also kept records of deadly roof failures along with important details:

the mine’s depth, the size and shape of its pillars, the nature of the rock in the roof, and so on.

Oddly, no one was really searching for meaning in the numbers.

“They had all this data but weren’t doing much with it,” said Chris.

The phenomenon had also occurred in baseball and, I’d bet, in other fields, too.

The impulse to collect data preceded the ability to make sense of it.

People facing a complicated problem measure whatever they can easily measure.

But the measurements by themselves don’t lead to understanding.

At the start, much of what Chris did in his new job felt like bricolage.

He took data gathered by others and work done by others and repurposed it to his narrow problem.

His immediate goal was to create for the pillars inside the tunnels of longwall mines the equivalent of what engineers call a safety rating.

A safety rating is the load-bearing capacity of whatever is holding the load,
divided by the load.

(If it’s less than one, don’t look up.)

Bieniawski had created a formula for calculating the load-bearing capacity of coal pillars,
but to use it you needed to know the load that needed bearing.

Calculating this was tricky.

It changed as coal was removed from the mine in ways that were not obvious,
and that varied from mine to mine.

The rock that collapsed harmlessly behind the mining machine did not have the same ability to support the mountain above it as the previously intact seam of coal.

Crumbled cake offered less support to whatever was above it than intact cake.

The weight of the mountain needed to travel someplace.

One place it went was onto the remaining coal pillars.

The more coal you removed, the greater the so-called abutment load
— not the load that was vertically over the pillar, but the load that moved, horizontally, onto it.

Chris spent several years measuring the way the load on the pillars changed as coal was mined.

His aim was to reduce his findings to a set of equations that could be used by mine designers.

Given the length of the mining wall, the depth of the mine and the height of the roof, etc.,
the load should be roughly X.

X was the numerator of his safety factor, which,
to avoid the impression that the entire mine was rendered safe by it,
he renamed the “stability factor.”

He then back-tested the number against case histories to see whether coal mine roofs had indeed collapsed when the stability factor was less than his model thought it needed to be.

He was turning pillar stability into a science.

“All I’m doing is taking trial and error and looking at the data more scientifically,” he said.

By academic statistician standards, his work was more than a bit loose.

“I’ll never have a database that is large enough
— or collected in the random way that you’d need to do precise statistical analysis,” he said.

“I’ll never be able to say ‘there’s a 95 percent chance the roof will hold up.’

You’ll never know the exact probabilities.

I’m using statistics to make better engineering judgments.”

He finished his thesis while settling into his new job at the Bureau of Mines.

But even before it was finished, coal mine engineers embraced his stability factor.

At conferences, they’d come up to him after he’d explained his work and say,
what you are doing is the future.

They hadn’t felt compelled to do the work themselves, but they were delighted that he spared them these roof falls that cost them $200 a minute to clean up.

There was a limit to its practical usefulness, though, as the stability of a coal mine roof depended on its specific geology.

And the geology varied from coal field to coal field.

“In some places, like Pittsburgh, you needed a higher stability factor,
and in other places, like Alabama, you could use a smaller one,” said Chris.

The same stress that caused a mine roof outside Pittsburgh to crumble and collapse would have no effect on a mine roof in Alabama.

It wasn’t enough to know the load on the pillars.

You needed also to know more about the rock mass over them.

In some coal fields, the sedimentary layers were as thick and cohesive as a chocolate fudge cake,

in others as thin and flaky as a mille-feuille.

Some mines had more moisture in them than others,
and some rocks, in the presence of moisture, would return to mud.

Layers of laminated shale tended to be weakly bonded and vulnerable to horizontal stress.

All else equal, a layer of sandstone was a good sign.

Yes, it had once been a beach, but grains of sand tended to bond more strongly than other particles.

Between a rock and a rock mass was the difference between a person and a society.

Hard as it was to understand a rock,
it was far harder to understand masses made of lots of different rocks.

And so Chris spent much of the late 1980s and early 1990s figuring out which qualities in rock masses caused their strength to vary.

“What I realized very quickly was that none of the existing classification systems for rocks were going to work for coal mine roofs.

You are evaluating not a rock but a structure.

There’s enormous variety.

That’s the key, to look past that variety and come up with a measure.”

Again, he found work done by others and repurposed it for his uses.

Back in the 1940s, geologists working for the Agriculture Department in national forests created a crude method for work crews to determine if some rock would work as a road:

whacking it with a ball-peen hammer.

Oddly, it didn’t matter how hard you whacked it.

There were just a handful of ways the rock might react,
and its specific reaction revealed its strength.

Chris started whacking mine roofs with ball-peen hammers.

“It’s not precise,” he said, “but it does get you in the ballpark.”

The why of it all often remained out of view.

He couldn’t explain why certain traits in a rock mass made it less prone to collapse.

He could just show that they did.

But as Chris set out to classify rock masses, he noticed an odd force that was often observed inside underground coal mines:

the massive horizontal stress on the rock.

“There’s a textbook explanation for stress in the ground,” he said.

“You have the vertical stress of the rock above.

And any time you apply stress from above, the rock below tries to expand laterally.

But at depth it can’t expand laterally in either direction because it is confined by other rock.

So you get horizontal stress.”

In the textbooks, the rule of thumb was that the horizontal stress was about one-third of the vertical stress.

In fact, as mine engineers had known from the stress gauges they drilled into rock,
the forces on the rock running parallel to the Earth’s surface were often two to three times greater than the vertical pressure from the rock pressing down directly from above.

Often miners could even see this horizontal stress
— say, in a buckled mine floor.

But its source was a mystery.

“No one could explain it,” said Chris.

“Nobody had any theory of it.”

It finally occurred to him that what coal miners were seeing near the surface of the Earth
was simply an expression of forces deeper in the Earth’s crust:
plate tectonics.

He made a study and sure enough, the direction of the horizontal stress in coal mines lined up exactly with the definitive plate tectonics stress map that had been created in the 1970s.

The plates pushing against each other directly below West Virginia create a stress running from east to west.

West Virginia mines that ran north to south had always experienced more roof collapses than those that ran east to west,
but no one knew why.

Now they did:

It was as if they were trying to saw against a wood’s grain instead of with it.

“Once you figured that out, it was like magic,” said Chris.

“You would see people’s eyes light up.”

By 1994, Chris had figured out how to rate any coal mine roof, on a scale of 1 to 100.

He’d created new understanding of the effects on roof strength of various properties of rock masses:
the thickness of the sedimentary layers, their sensitivity to moisture, their response to being whacked by a ball-peen hammer, and so on.

He’d reduced these to a checklist that any coal mine engineer anywhere in the world could use to evaluate his roof and know just how much support it required.

And then he’d traveled to coal fields across the United States to personally deliver to mining engineers the new knowledge,
in the form of software he’d written.

“Technology transfer has always been central to what I do,” he said.

“If you don’t transfer it, you’re just wasting taxpayers’ money.”

It was all voluntary.

Congress never passed any law that ordered coal mine companies to use the Chris Mark software.

The last specific rules on the subject passed by Congress had been written in 1969 and said only that coal mine pillars needed to be sized appropriately for their conditions.

It never specified what that meant.

“It’s not like we told them, ‘Hey, you have to use 70 foot-wide pillars here,’” said Chris.

“We just said, ‘Here’s a solution.’

I knew it was better than anything they had before.

There was no competition out there.”

A mining engineer named Phil Worley, who’d spent his entire career working for coal mining companies, put it another way:

“It was like somebody turned on the lights.”

There’s obviously something unusual about a person willing to spend a decade figuring out how to prevent roofs collapsing in longwall coal mines.

“Why I find it so fascinating is a mystery to everyone I’ve ever met,” said Chris.

“But I do.”

Most people capable of solving such a time-intensive technical problem would grow bored of it before they were done.

“You have to be smart but not too smart to put in the years,” as he put it.

The federal government has long been a natural home for such characters:

people with their noses buried in some particular problem from which they feel no need to look up.

But once Chris had solved his particular technical problem, he had nothing to do but to look up.

“I said, ‘Okay, I solved the pillar problem for longwall mines.

What do I want to do next?

I want to look at whatever has the direst safety implications.’”

He never questioned the path he had put himself on,
but he soon had new thoughts about how to move along it.

“As far as I was concerned, there was only one reason I was there:
worker safety,” he said.

“At the Bureau of Mines you didn’t have to feel that way.

The kinds of things we did research on were usually not the same things that killed people.

It was more about keeping the mine stable and working.

But I started asking: What’s killing people?”

And so he brought his statistical mind to another mother lode of data:
casualty reports,
which had been meticulously collected since they were mandated by law in 1952.

He began to read individual accident reports.

Patterns leaped out from them.

Chris had always imagined that accidents in a coal mine followed the same logic as casualties on a battlefield.

In war, the rule of thumb had always been that for every soldier who died, three or four would be wounded.

He now saw that for every miner who was killed by a falling roof, 100 were injured.

More oddly, the injuries were occurring in mines where the pillars held up.

“When I looked at the data, the support system seemed to be working, but you had all these injuries,” said Chris.

He assembled another database.

It showed that injuries were being caused by smaller pieces of rock falling between the pillars.

As these fragments could be the size of Volkswagen buses,
they occasionally killed,
but mostly they just maimed. “

I realized that death and injuries were two separate problems,” he said.

“On a battlefield the same bullet can kill or wound you.

Here there are two different mechanisms.”

He’d been so focused on the bullets that killed that he hadn’t noticed the bullets that usually just wounded.

This was the problem that roof bolts had been invented to fix.

Right through World War II, miners had used timbers to support the roof directly over their heads.

In the 1940s, a handful of coal companies showed that it was far more effective to bolt the roof,
effectively to itself.

It struck many miners, at first, as completely weird.

They’d drill a hole into the mine roof and then drive a metal bolt between three and six feet long into it.

The bolt pinned the sedimentary layers together the way a toothpick pins a turkey club sandwich.

The success of the bolt
— and the toothpick
— turns on the presence of at least one solid, strong layer.

Roof bolts, in effect, used strong rock to hold weaker rock in place.

“The single most important technological development in the field of ground control in the entire history of mining,” Chris called them.

Roof bolts were adopted more rapidly than any other technology in coal mining.

Someone had the idea, and almost instantly they were being drilled into mine roofs.

They obviously worked and yet … they hadn’t.

At least not for a very long time.

In the accident statistics, Chris stumbled upon a riddle:

The powerful new technology hadn’t reduced deaths and injuries.

“The accepted story was someone invented roof bolts and it was safer right away,” he said.

“I looked into it and saw it just wasn’t true.

By the end of the 1950s, death rates had actually gone up!”

It was a full two decades before roof fall fatality rates began to decline, and dramatically.

That year, 1969, also happened to be the year that the Bureau of Mines was finally given the enforcement power it needed to properly regulate the industry.

The standard story
— the story accepted by the coal mine industry
— was that new technology had led inexorably to greater safety.

What had happened was far more interesting
— and told you how this little American subculture worked,
rather than the way economists who had never seen the inside of a coal mine might imagine that it worked.

Roof bolts were indeed more efficient and effective than timber supports in preventing chunks of roof from wounding miners.

But they were expensive to install.

The coal mine companies had, in effect, figured out how few roof bolts they needed to use to maintain the same level of risk their miners had endured before their invention.

“Simply stated,” Chris wrote, “roof bolts can only prevent roof falls if enough of them are installed.”

And so, amazingly, for the first 20 years of its use, the main effect of the most important lifesaving technology in the history of coal mining was to increase the efficiency of the mines
while preserving existing probabilities of death and injury.

Taking advantage, essentially, of people conditioned to a certain level of risk by failing to ameliorate that risk.

“No one puts people’s lives at risk per se,” Chris said.

“It’s not obvious most of the time that people’s lives are at stake.

You’re always playing probabilities.

But they knew what they were doing.

They could see people dying.

Even in a union mine they did it.

That is what is so extraordinary.

These were not dumb guys.

This was a conscious decision.”

If coal mine companies had played the odds with miners’ lives,
it was because they felt they couldn’t afford not to.

Any mine that installed a safe number of roof bolts would find itself at a competitive disadvantage to any mine that didn’t.

It had been a race to the bottom,
and until Chris created his database and made his study,
no one had really noticed what had happened.

If working-class families in West Virginia were angry but didn’t know quite where to direct their feelings,
here was a road map.

Their society had just assumed it could foist risk upon them without anyone ever really noticing or caring.

But someone had noticed.

The point of the roof bolt story was that,
left to itself,
the free market would fail to protect ordinary workers
— even when it clearly had the wherewithal to do so.

A mining company called Murray Energy soon proved the point.

Just before 3 in the morning of Aug. 6, 2007, the pillars collapsed inside of its Crandall Canyon mine in Emery County, Utah.

Crandall Canyon was especially deep:

Six miners were trapped 2,000 feet underground.

Three rescue workers were killed trying to save them.

The bodies of the six miners were never recovered.

The subsequent investigation and Senate hearings and criminal trials would last for years,
but it took Chris less than a day to work out what had happened:

The company had ignored his formula for pillar design.

As the pillars were made of coal, the fewer of them you left standing, the more coal you could remove.

Murray Energy wanted more coal, and to get it, the company had hired an engineering consultant who persuaded a regional mine inspector to sign off on a pillar scheme that Chris’s formula would have flagged as wildly risky.

“This is one where it should have saved lives but didn’t,” said Chris.

“They ran my algorithm.

They knew they had a problem.

They said, ‘Don’t worry, it’ll be fine.’ ”

“The short answer to the question of what happened at Crandall Canyon is that the people in the Western coal fields had this deep-seated idea that the rules from the East didn’t apply to them,” said Chris.

It was the last time any mining company would be able to do that.

After the Crandall Canyon disaster,
all designs for mines deeper than 1,000 feet would need to be inspected by Chris’s office.

And Crandall Canyon would be the last major catastrophe caused by a falling roof.

Nine years later, for the first time in history,
no American miner would be killed by falling roofs.

And Chris would write another history.

“The Road to Zero: The Fifty-Year Effort to Eliminate Roof Fall Fatalities from U.S. Underground Coal Mines.”

The paper would show in persuasive detail not just what happened, but why.

About half of the deaths that were averted could be attributed to better technology and new knowledge
— that is, by the kind of work he had done.

The other half was due to changes in the culture of coal mining.

And the greatest spur to that change had been the federal regulations that gave mine inspectors the power to enforce rules.

It’s obviously not possible to do anything more than speculate why anyone ends up doing whatever they do with their lives.

But Chris had been endowed with a deeper-than-usual desire for fairness.

He had a powerful father and a powerless mother and wound up feeling powerful sympathy for the underdog.

He’d ended up working for the institution best equipped to help the unlucky defend themselves from the lucky.

And the effect of his work had indeed been to make the world just a little bit less unfair.

We’d just passed West Virginia’s last coal-fired power plant when I asked Chris a question that plainly irritated him.

I knew as little about coal mines as he had when he’d first seen one in 1976 and so had asked 2,000 stupid questions about them.

He’d patiently answered every one of them.

But then I hit a nerve.

“Is it normal for someone in your job to write academic history papers?”
I’d asked.

In the later part of his career, Chris had turned himself into the color commentator of the game in which he was still starring.

His papers
— mostly nitty-gritty descriptions of his research inside coal mines
— have made him, by a factor of two,
the world’s most cited mining engineer.

“I never wrote an academic paper,” he said, a bit sharply.

“Not one. They’re technical papers.”

He caught himself and explained that he saw himself not as an academic but a solver of practical problems.

“I have an absolute allergy to academic elitism,” he said,
but finally added.

“No, it’s not normal.”

He didn’t say much more,
and I set it aside and returned to a list of questions I had about government service.

How had he felt on the several occasions the federal government was shut down and he was sent home without pay?

(He’d secretly kept working and even gone into mines.)

What were his feelings in 1995 when Newt Gingrich closed the Bureau of Mines and his little mine safety unit had been the only one spared?

(“Any bureaucracy once it exists will continue to grow absent exogenous forces.

I never heard someone say I wish so-and-so at the Bureau of Mines was still here,” Chris said.)

How much had it mattered that he’d been moved into the Energy Department, then into the Centers for Disease Control and Prevention and finally into the Labor Department?

(“Not much.”)

The role played by his managers in Washington was to give him the space to work.

“What the government job gave me was the freedom to do these things,” he said.

“No one told me to do it.

No one could have told me to do it.”

But then a few hours later, toward the end of our drive, I hit another nerve.

“So you run away from home and your father’s bourgeois life
and you wind up doing underground what he did for Gothic cathedrals.”

“I don’t think of it like that,” he said, again a bit sharply.

He didn’t really see much connection between their careers.

His father had returned the favor.

“His father never acknowledged that their work had anything in common,” said Mary Denison,
who is both Chris’s wife and a psychologist.

The tension between them dwindled after the death of Chris’s mother and his return to his formal education.

“I always knew he had a high opinion of me and my abilities,” said Chris.

And the feeling was mutual.

But right up until his father died, in 2019, he never felt real warmth or got the sense that his father saw value in what he’d done with his life.

And yet even now his father hovered in the background both as a rhyme and a presence.

The careers of both men had been redirected by a simple question posed in a college class.

Both spent their lives measuring the stress in stone.

Both used scientific methods to answer questions that had seemed to everyone else beyond the reach of science.

Both sought to understand what prevented roofs from collapsing.

The father’s work had received a lot of public attention and the son’s had not.

But that was just an accident of what people cared about.

A lot of people cared about Gothic cathedrals;

fewer were concerned with whatever was happening to workers deep underground.

Every now and then, however, Chris’s work slipped into public view.

His coal mine roof rating was used all over the world and,
in his own narrow circles,
he was well known.

In 2016
— the first year in recorded history that zero underground coal miners were killed by falling roofs
— Chris landed in a public spat.

He’d seen an article by an economic historian about the history of roof bolts in the journal of Technology and Culture.

The historian wanted to argue that roof bolts had taken 20 years to reduce fatality rates because it had taken 20 years for the coal mining industry to learn to use them.

All by itself, the market had solved this worker safety problem!

The government’s role, in his telling, was as a kind of gentle helpmate of industry.

“It was kind of amazing,” said Chris.

“What actually happened was the regulators were finally empowered to regulate.

Regulators needed to be able to enforce.

He elevated the role of technology.

He minimized the role of regulators.”

To set the record straight
— and maybe also to start a fight with an academic he was bound to win
— Chris wrote a long and debate-ending letter to Technology and Culture.

As it happened, he knew the journal well.

His father had been its editor.

Later, Chris wouldn’t be able to recall whether he had called his father,
or if his father had called him.

In any case it had been in 2002, when his father faced a curious problem.

Robert Mark had been hired to figure out what was going on inside Washington National Cathedral.

The cathedral had taken 83 years to build.

Teddy Roosevelt had laid its first stone, and George H.W. Bush had presided over the laying of its last,
a decorative pinnacle.

The second architect on the project had enlarged the west facade without sufficiently adding to the foundation.

The whole building was subsiding,
but the west tower was sinking faster than the nave and,
in the bargain, beginning to tilt.

The elder Mark did what he did:

He modeled the stresses in the building.

Soon enough he figured out that the answer lay beneath the ground.

“I told him we had instruments to measure this sort of movement,” said Chris.

“The kinds of things to measure rocks in a mine.”

He asked for and received permission to use the equipment to study the church.

For the next four years, father and son worked together to determine whether,
as Chris put it,
“we were going to have the Leaning Tower of Pisa or something.”

It was tricky.

The devices they installed showed the cathedral tilting one way and then straightening itself in a single day.

It moved so much with the warmth of the sun, and with the seasons, that it took them several years to get a read on the severity and speed of the longer trend.

“What we found was that these things were going on, but the big problem was slowing down, and it was going to level off,” said Chris.

The cathedral wasn’t at risk of collapse.

This piece of work wasn’t a big deal.

He had done it for free and the fun of it.

He and his father wound up writing the only paper they’d ever write together about it.

Still, a problem had gotten solved, and Chris enjoyed that feeling.

All he ever wanted to do was to find problems that were fixable.

After all, roofs fell.

Someone needed to help them stay up.

-- On Sept. 11, at a ceremony at the Kennedy Center,
Christopher Mark will receive the Sammies Award for Career Achievement