Rudolph Marcus was perplexed. It was 1955 and Marcus, a 31-year-old associate professor of chemistry still in the early stages of his career, had found an elementary mistake in the work of an esteemed scientist.

“Something doesn’t add up,” Marcus thought..

Marcus had discovered a calculation that violated the law of conservation of energy, a bedrock scientific principle, tucked inside a new theory on electron behavior. This frustrated Marcus because he otherwise liked the innovative theory that had been proposed by Willard Libby, a physicist who had helped develop the atom bomb.

Marcus set out to fix the problem, but ended up doing much more. Within a month, he had developed an elegant formula that would upend scientific understanding of how molecules use energy and eventually win him the Nobel Prize.

“When I got the result it was the most exciting moment that I’d ever had in science in my life,” he recalled in a Caltech oral history interview in 1993. “There was just such exhilaration. … It came out in such a simple form. It really was a thing of beauty — to me, anyway.”

Marcus, a Caltech professor for nearly half a century and a longtime Pasadena resident, died peacefully Thursday at home, Caltech and his family said. He was 102.

“Rudy Marcus’s career exemplified the beauty and reach of fundamental science, and he will be deeply missed,” said Caltech President Ray Jayawardhana. “He was a visionary scientist who transformed our understanding of chemical reactions at their most elementary level, [and] laid the conceptual foundations that continue to shape advances in clean energy, catalysis, electronics, and beyond.”

Marcus, who would have turned 103 on Tuesday, was at work on three separate research papers at the time of his death, his family said.

Marcus first published his conclusions on “electron transfer reactions” in 1956 and continued to refine them over the next nine years. His ideas were controversial until they were confirmed by experiments over three decades. In 1992, he was awarded the Nobel for chemistry.

The Marcus Theory, as it came to be known, provides a mathematical way to determine how fast or slow, or in what direction, electrons jump between molecules without breaking chemical bonds. It expanded scientists’ knowledge of a wide spectrum of processes, such as how plants gain energy from sunlight, how animals use oxygen and food as fuel, and how batteries use chemicals to create electricity.

He was also known for his part in what was called the RRKM theory, named for the four scientists, including Marcus, who developed it. It describes how energy is released from the chemical reactions of molecules in the gas phase.

“The RRKM theory is one of the outstanding theories of chemical physics,” said Harold Johnson, a physics professor at UC Berkeley, in 1985. “Marcus took a good theory developed in the 1920s and ‘30s, brought it up to date in 1951 and made it complete. All kinds of people in chemistry use it.”

Rudolph Arthur Marcus was born July 21, 1923, in Montreal, the only child of American-born Myer Marcus and English-born Esther Marcus, both of Jewish Lithuanian descent. His father had various jobs, selling picture frames at one point, later managing a fruit store. When he was 3, his family moved to Detroit, then returned to Montreal when he was 9.

While his father had little interest in education, Marcus found academic inspiration in two uncles who were doctors, a great-uncle who could speak nine languages and, mostly, his mother.

“She liked school so much that she went to the last grade twice, because she couldn’t afford to go on,” Marcus recalled in a 1991 interview with the Chemical Heritage Foundation.

In high school, he developed a love for mathematics: “If the teacher said do every alternate problem, I’d do every problem, just simply for the fun of doing it.”

At Montreal’s McGill University, he majored in chemistry, partly because an advisor said that as a Jew he would have a harder time finding a job in mathematics. He received his bachelor’s degree in 1943 and a PhD in 1946, both in chemistry and both from McGill.

Marcus did his first postdoctoral research in Ottawa, but in 1949 he jumped at the chance to study theory — instead of hands-on, experimental chemistry — at the University of North Carolina. Within his first few days there, Marcus met Laura Hearne, a graduate student in sociology, and they married six months later. They would have three sons together and remain married until her death in 2003.

In 1951, Marcus landed at the Polytechnic Institute of Brooklyn as an assistant professor. It was there, four years later, that he had his Nobel-winning insight.

“We’ve heard of ‘eureka’ and, yes, there was this eureka moment,” he recalled. “I’ve never solved a problem so quickly, before or after.”

In 1958, he was naturalized as an American citizen.

In 1964, Marcus left Brooklyn’s Polytechnic to be a chemistry professor at the University of Illinois. He spent 14 years there — even turning down a professorship at England’s Oxford University because he didn’t want to uproot his family — before coming to Pasadena and the California Institute of Technology in 1978. Caltech was his home for the rest of his career, though he stepped down from teaching at the age of 95.

“Enough is enough,” he joked in 2023. “They should really have somebody who really knows something.”

The Nobel and its $1.2-million prize did little to change Marcus. A 1994 Los Angeles Times profile noted that he continued to walk to work most days from his home just off the Pasadena campus, and still drove a 16-year-old car. He said proudly that when Laura met Sweden’s King Carl Gustav XVI, she was wearing a homemade dress.

Around the Caltech campus, Marcus remained so unaffected and so focused on his research that one colleague quipped that he “must have spent his million dollars on a new sweater.”

Said Marcus: “It’s best if one doesn’t think too much about prizes and things. That puts the focus in the wrong place, which should be on your work … on a particular problem and how you should solve it.”

Marcus is survived by sons Alan, Kenneth and Raymond; four grandchildren; one great-grandson; and his long-term colleague and companion Maria-Elizabeth Michel-Beyerle.

In 2023 Caltech held a symposium in honor of Marcus’ 100th birthday. As family, friends and colleagues dropped by his table to offer congratulations, he confessed that he was eager to get back to the office. He had a new experiment he was excited to work on.

“The main thing is finding something that you enjoy doing, that preferably doesn’t harm others, and that tests whatever aptitude one has, that tests one’s ingenuity,” he said of his approach to life. “It’s almost like a kind of a game. You against nature.”

CONCOW, Calif. — Until recently, when members of the Konkow Valley Band of Maidu pulled up a map of their ancestral land in the foothills of the Sierra Nevada, only about two dozen of their historic sites appeared.

Disease, violence and forced labor had separated California tribe members from their history. Without routine Indigenous fire to clear out the foothills, the landscape — much of it now managed by the U.S. Forest Service — grew dense with conifers, obscuring the signs of their enduring presence.

As a result, archaeologists’ picture of the tribe’s past was spare. No more than 500 people. Going back about 3,000 years — a fraction of the time other tribes are known to have lived in the state.

Then the forests burned.

In less than a decade, wildfires destroyed forests across 95% of the tribe’s homelands. The Forest Service turned to the tribe for help healing the land. As members walked the wide-open moonscape, they found evidence of their vibrant history everywhere.

Now just a few years later, their map shows more than 1,200 sites.

Each one is itself a collection: Arrowheads. Rock art. Milling stations where ancestors used cups carved into rock faces to grind salmon, manzanita berries and bay leaves. The circular pits of winter houses, where they sat around a fire under a cedar roof.

Now, as Tribal Chairperson Matthew Williford Sr. walks these lands, he imagines a much more vibrant past than the one traditionally portrayed by archeologists.

For millennia, upward of 5,000 ancestors living in the basin, many trekking to higher elevation to gather food in the summertime. Husbands venting about domestic life as they shaped their arrowheads on one side of the hill; wives doing the same at the milling stations on the other side.

Matthew Williford Sr., Konkow Valley Band of Maidu tribal chairperson, stands in Plumas National Forest.

(Sara Nevis / For The Times)

Now, to better understand the tribe’s past, the Konkow Valley Band of Maidu is teaming up with a new generation of archaeologists. On a recent day in the Plumas National Forest, Matthew O’Brien, an anthropology professor at Chico State University, worked alongside a handful of students and tribal members.

The team excavated a house pit, carefully carrying artifacts to a rudimentary lab of folding tables and camp chairs, where students weighed them, measured them with calipers and assessed their chemical makeup with an expensive tool called an XRF analyzer. People offered explanations for how their ancestors used the artifacts.

For O’Brien, this form of archeology is worlds apart from the practice of the past. Tribal people are not voiceless historical subjects to study but active collaborators helping to understand and protect the past.

In the 20th century, “the government put archaeologists in charge of stewarding the past. In places like the United States, that leads to some serious ethical issues because what we’re in charge of protecting is not our own culture,” O’Brien said. Now, “it’s our job to help repair that relationship.”

It’s an irony lost on no one that the same policies that disconnected tribal members from their history also enabled the fires that then allowed them to rediscover it.

Even before California gained statehood, Gold Rush lawmakers banned tribes from lighting fire to rejuvenate and thin out forests. That same law also allowed white Californians to force Indigenous adults and children into labor, which separated “at least a generation of children and adults from their families, languages, and cultures,” the state later acknowledged.

Meanwhile, the federal government refused to ratify treaties to establish reservations for tribes whose homelands lay within newly created California, leaving tribes like the Konkow Valley Band of Maidu landless. By the early 1900s, Forest Service officials were working aggressively to squash lingering sentiment among white ranchers that intentional fire was productive. Any fire that started on Forest Service land, the policy became, ought to be contained by 10 a.m. the next morning.

The Konkow Valley Band of Maidu did what they could. Tribal members drove around in a beat-up Buick flinging matches out the window. Eventually those efforts landed one elder in jail for arson.

The open forests of oak, dogwood and a few pines, once routinely thinned and maintained with low-intensity “good” fire, became thick with conifers, to the delight of the Forest Service. Now five to six times denser, the trees formed yet another barrier between the tribe and its history — yet a fragile one. When fire inevitably ignites within so much wood in such a tight space — through lightning or human error — it does not burn gently.

A statue stands in a lot charred by the Camp fire, which tore through Paradise, Calif., in 2018.

(Noah Berger / Associated Press)

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In 2018, the Camp fire ripped through Butte County, burning 150,000 acres and killing 85 people. Three years later, the Dixie fire ravaged nearly a million acres. In its wake, a world covered in ash. Waterways turned into black sludge. A foul smell of sulfur lingered in the air.

“It was sickening,” Williford said. “Just disgusting.”

Material to be burned is piled in an area of Plumas National Forest that the Konkow Valley Band of Maidu helps manage.

(Sara Nevis / For The Times)

“The land used to repay us, or acknowledge us, by giving us what we needed,” Williford said, standing on a dirt road overlooking the valley. “There were Native generations that were disconnected, unplugged. … We feel lucky that it’s our opportunity to reconnect, to let the land know that ‘Hey! We’re still here!’”

Restoration work with the Forest Service — surveying sites, planting trees and bringing back good fire — continues to unearth long-lost artifacts. And the most exciting data from O’Brien’s team is yet to come:

The team plans to carbon-date a piece of charcoal from the house pit it excavated to see just how long ago tribal ancestors sat around its hearth.

It was an ancient fire, not the recent ones, that preserved some dead wood, and with it, a lasting elemental fingerprint saying, “We were here.”