The story of how James Reason became an authority on the psychology of human error begins with a teapot.

It was the early 1970s. He was a professor at the University of Leicester, in England, studying motion sickness, a process that involved spinning his subjects round and round, and occasionally revealing what they had eaten for breakfast.

One afternoon, as he was boiling water in his kitchen to make tea, his cat, a brown Burmese named Rusky, sauntered in meowing for food. “I opened a tin of cat food,” he later recalled, “dug in a spoon and dolloped a large spoonful of cat food into the teapot.”

After swearing at Rusky, Professor Reason berated himself: How could he have done something so stupid?

The question seemed more intellectually engaging than making people dizzy, so he ditched motion sickness to study why humans make mistakes, particularly in high-risk settings.

By analyzing hundreds of accidents in aviation, railway travel, medicine and nuclear power, Professor Reason concluded that human errors were usually the byproduct of circumstances — in his case, the cat food was stored near the tea leaves, and the cat had walked in just as he was boiling water — rather than being caused by careless or malicious behavior.

That was how he arrived at his Swiss cheese model of failure, a metaphor for analyzing and preventing accidents that envisions situations in which multiple vulnerabilities in safety measures — the holes in the cheese — align to create a recipe for tragedy.

“Some scholars play a critical role in founding a whole field of study: Sigmund Freud, in psychology. Noam Chomsky, in linguistics. Albert Einstein, in modern physics,” Robert L. Sumwalt, the former chairman of National Transportation Safety Board, wrote in a 2018 blog post. “In the field of safety, Dr. James Reason has played such a role.”

Professor Reason died on Feb. 4 in Slough, a town about 20 miles west of London. He was 86.

His death, in a hospital, was caused by pneumonia, his family said.

A gifted storyteller, Professor Reason found vivid and witty ways to explain complicated ideas. At conferences, on TV news programs and in consultation with government safety officials around the world, he would sometimes deploy slices of cheese as props.

In one instructional video, he sat at his dining room table, which was set for a romantic dinner, with a bottle of wine, two glasses and a cutting board layered with cheese.

“In an ideal world, each defense would look like this,” he said, holding up a slice of cheese without holes. “It would be solid and intact.”

Then he reached for another slice, one with quarter-size cutouts. “But in reality, each defense is like this,” he said. “It has holes in it.”

The metaphor was easy to understand.

“All defenses have holes in them,” Professor Reason continued. “Every now and again, the holes line up so that there can be some trajectory of accident opportunity.”

To explain how the holes develop, he put them in two categories: active failures, or mistakes typically made by people who, for example, grab the cat food instead of the tea leaves; and latent conditions, or mistakes made in construction, written instructions or system design, like storing two scoopable substances near each other in a cabinet.

“Nearly all organizational accidents involve a complex interaction between these two sets of factors,” he wrote in his autobiography, “A Life in Error: From Little Slips to Big Disasters” (2013).

In the Chernobyl nuclear accident, he identified latent conditions that had been in existence for years: a poorly designed reactor; organizational mismanagement; and inadequate training procedures and supervision for frontline operators, who triggered the catastrophic explosion by making the error of turning off several safety systems at once.

“Rather than being the main instigators of an accident, operators tend to be the inheritors of system defects,” he wrote in “Human Error” (1990). “Their part is that of adding the final garnish to a lethal brew whose ingredients have already been long in the cooking.”

Professor Reason’s model has been widely used in health care.

“When I was in medical school, an error meant you screwed up, and you should just try harder to not screw up,” Robert Wachter, the chairman of the department of medicine at the University of California San Francisco, said in an interview. “And if it was really bad, you would probably get sued.”

In 1998, a doctor he had recently hired for a fellowship said he wanted to specialize in patient-safety strategy, to which Dr. Wachter replied, “What’s that?” There were no formal systems or methods in his hospital (or most others) to analyze and prevent errors, but there was plenty of blame to go around, most of it aimed at doctors and nurses.

This particular doctor had trained at Harvard Medical School, where they were incorporating Professor Reason’s ideas into patient-safety programs. Dr. Wachter, who began reading Professor Reason’s journal articles and books, said the Swiss cheese model was “an epiphany,” almost “like putting on a new pair of glasses.”

Someone given the wrong dose of medicine, he realized, could have been the victim of poor syringe design rather than a careless nurse. Another patient could have died of cardiac arrest because a defibrillator that was usually stored in the hallway had been taken to a different floor to replace one that had malfunctioned — and there was no system to alert anyone that it had been moved.

“When an error happens, our instinct can’t be to look at this at the final stage,” Dr. Wachter said, “but to look at the entirety of the system.”

When you do, he added, you realize that “these layers of protection are pretty porous in ways that you just didn’t understand until we opened our eyes to all of it.”

James Tootle was born on May 1, 1938, in Garston, a village in Hertfordshire, northwest of London. His father, Stanley Tootle, died in 1940, during World War II, when he was struck by shrapnel while playing cards in the bay window of his house. His mother, Hilda (Reason) Tootle, died when he was a teenager.

His grandfather, Thomas Augustus Reason, raised James, who took his surname.

In 1962, he graduated from the University of Manchester with a degree in psychology. He received his doctorate in 1967 from the University of Leicester, where he taught and conducted research before joining the faculty at the University of Manchester in 1977.

He married Rea Jaari, an educational psychologist, in 1964. She survives him, along with their daughters, Paula Reason and Helen Moss, and three grandchildren.

Throughout his career, Professor Reason’s surname was a reliable source of levity.

“The word ‘reason’ is, of course, widely used in the English language, but it does not describe what Jim is rightly famous for, namely ‘error,’” Erik Hollnagel, the founding editor of the International Journal of Cognition, Technology and Work, wrote in the preface to Professor Reason’s autobiography. “Indeed, ‘error’ is almost the opposite of ‘reason.’”

Still, it made sense.

“Jim has certainly brought reason to the study of error,” he wrote.

From Thursday night into Friday morning, Earth’s shadow will swallow the moon, transforming the usually pearly orb into a striking red sphere.

It’s the first total lunar eclipse in more than two years. Also known as a blood moon, the event will be most visible across the Americas, western parts of Africa and Europe, New Zealand and some of Russia.

“It’s a lovely sight to see in the night sky,” said Amanda Bosh, the executive director of the Lowell Observatory in Arizona, who has seen more than 20 lunar eclipses in her lifetime.

“I love seeing the solar system, the universe, at work,” she added.

What is a total lunar eclipse?

A lunar eclipse occurs when the sun, Earth and moon align, in that order. There are different types of lunar eclipses that depend on how deeply the moon crosses into Earth’s shadow, which is divided into an outer part, the penumbra and the umbra, the innermost section.

A total lunar eclipse, when the entire moon slips into the umbra, is by far the most dramatic variety. Earth’s shadow envelops the face of the moon, causing it to shine scarlet. This happens because sunlight spilling over the edges of Earth and lighting up the lunar surface must first travel through our atmosphere, which more readily scatters blue wavelengths of light. Redder wavelengths pass through, creating the blood-moon effect.

According to Dr. Bosh, the exact shade of red during a lunar eclipse can vary. Clouds and recent natural disasters — like dust storms or volcanic eruptions, which leave particles in the air — can make the moon appear more crimson.

Less visually striking is a penumbral eclipse, when the moon grazes through the outer part of Earth’s shadow. This causes the moon to dim so slightly that it can be difficult to notice.

When only a portion of the moon recedes into the innermost umbra, it creates a partial eclipse, which looks like a bite has been taken out of the lunar surface.

When will this eclipse occur?

There are several phases of a total lunar eclipse. According to the United States Naval Observatory, the event will occur over about six hours across Thursday and Friday.

The moon will begin to creep into Earth’s penumbra at around 11:56 p.m. Eastern time on Thursday. At 1:09 a.m. on Friday, the moon will enter the umbra, during which a growing portion of its surface will be obscured from view. According to Dr. Bosh, the moon will appear more red as the partial phase elapses.

Totality, when the entirety of the moon is engulfed in the darkest part of Earth’s shadow, occurs at 2:25 a.m. and lasts for just over an hour.

Then the lunar surface will begin to brighten white again as the moon glides out of the umbra, a phase that lasts until 4:48 a.m. Eastern time. The final leg of its journey, through the penumbra, finishes at 6:01 a.m.

How can I see the eclipse?

Anyone on the night side of Earth will have the opportunity to see the lunar eclipse, but how much you can see depends on your location.

Skywatchers in most of North America and the western half of South America can witness the entire event. But in other places, people may just catch the eclipsed moon rising or setting in the sky.

No special equipment is needed for this cosmic sight. “It’ll look just as beautiful with your eyes” than it would through a telescope, said Dylan Short, a telescope specialist at Lowell Observatory. Decent photographs can be taken with a cellphone, he said, or with a simple D.S.L.R. camera that uses a lens with a long focal length. Images of the moon can also be captured through the eyepiece of a telescope.

In many cities, local stargazing groups and planetariums are hosting watch parties. Another option is to view a live broadcast of the lunar eclipse online.

Will weather affect my viewing?

Although a winter storm is barreling across the United States, forecasters say sky viewers have a shot at seeing the eclipse in several areas, including portions of Florida, the central and southern Plains, West and South Texas, the Ohio Valley into the Appalachian Mountains, and a sliver of the desert Southwest.

But in other parts of the country, including the East and West Coasts, clear views may be more difficult to come by.

If you do see clouds in the sky during the eclipse, keep in mind that the event unfolds over several hours. It may be worth looking again later, especially if those clouds are thin or seem to be moving.

When will the next eclipse occur?

Lunar eclipses can happen several times a year, though not all of them reach totality. According to NASA, the next total lunar eclipse will occur in September, most visible in Asia and parts of Europe, Africa and Australia.

There will be another total lunar eclipse next March, followed by a partial lunar eclipse later in August.

Lunar eclipses also occur paired with solar eclipses. On March 29, this lunar eclipse’s partner, a partial solar eclipse, will be visible in parts of North America and Europe.

Amy Graff contributed reporting.