The Forgotten Irish Genius Who Split the Atom and Changed Science Forever

Added: 2026-05-24

[00:00:00]On the 14th of April, 1932, in a basement laboratory in Cambridge, an Irishman climbed into a wooden observation hut, barely big enough for one person, switched on a 700,000 volt particle accelerator, and made history.

[00:00:16]He watched a beam of protons slam into a thin sheet of lithium, and saw something that nobody on Earth had ever seen before.

[00:00:24]>> [music] >> The atom, the basic building block of matter, the thing every scientist had been trying to understand for over 2,000 years, broke apart in front of his eyes.

[00:00:35]He described what he saw as twinkling stars. What he was actually looking at was the birth of the nuclear age, the atomic bomb, nuclear medicine, nuclear power, particle physics, everything that came after. All of it traces back to a single moment in a Cambridge basement on a spring afternoon in 1932.

[00:00:57]He split the atom. His name was Ernest Walton.

[00:01:00]>> [music] >> He won the Nobel Prize for it, and almost nobody outside Ireland has ever heard of him. This is his story. This is Dust and Stories. [music] Subscribe, because some of the most important people in history are the ones nobody ever talks about.

[00:01:17]Ernest Thom Thomas Sinton Walton was born on the 6th of October, 1903, >> [music] >> in a town called Dungarvan, on the south coast of County Waterford.

[00:01:28]His father, John Walton, was a Methodist minister. His mother, Anna Sinton, [music] came from a very old Ulster family who had lived in the same house in Armagh for over 200 years. Methodist ministers in Ireland at that time moved parishes every few years, and Walton's childhood was spent moving from town to town, to places like Banbridge in County Down, and Cookstown in County Tyrone, and parishes across the north of Ireland.

[00:01:57]>> [music] >> He attended a series of local schools, and in 1915, at the age of 12, he was sent as a boarder to Methodist College in Belfast. That's where everything started. The teachers at Methodist College spotted something in the quiet boy from Waterford almost immediately.

[00:02:14]>> [music] >> He had an aptitude for mathematics and science that bordered on the extraordinary. He won prize after prize.

[00:02:22]By the time he finished school in 1922, he had won a scholarship to Trinity College Dublin to study mathematics and experimental science. Within 2 years, he was elected a foundation scholar, one of the highest academic honors at Trinity, awarded only to students who demonstrate exceptional ability through grueling examinations.

[00:02:44]He graduated in 1926 with first-class honors in both mathematics and physics, a double first, the highest possible result. He earned his master's degree the following year, and then the world opened up.

[00:02:59]In 1927, Walton was awarded a research scholarship by the Royal Commission for the exhibition of 1851, >> [music] >> a prestigious British scholarship for outstanding scientists from across the empire. [music] The award gave him a place at Trinity College Cambridge working at the legendary Cavendish Laboratory under Lord Ernest Rutherford. Rutherford was, at that moment, the most famous physicist in the world. He had discovered the atomic nucleus. He had won the Nobel Prize. He had transmuted nitrogen into oxygen [music] using natural radiation in 1919, the first artificial transformation of one element into another in human history.

[00:03:41]The Cavendish under Rutherford was the most important physics laboratory on the planet. When Walton arrived, there were four Nobel laureates already on the staff. By the time he left, that number had grown, and Walton himself would be one of them.

[00:03:57]But the path from Cambridge novice to Nobel laureate was anything but smooth.

[00:04:02]Rutherford had set the lab a problem.

[00:04:04]He wanted a way to artificially produce fast-moving particles, protons accelerated to such high speeds that they could be used to bombard atomic nuclei and probe their structure.

[00:04:18]The Rutherford experiment of 1919, which had transmuted nitrogen into oxygen, had relied on alpha particles from naturally radioactive elements.

[00:04:29]But nature was unreliable. Alpha particles flew in random directions at random speeds.

[00:04:36]To really understand the atom, scientists needed control. They needed to aim. They needed to choose the energy of their particles.

[00:04:45]And in 1928, that was impossible.

[00:04:48]There were no particle accelerators.

[00:04:50]Nobody had built one.

[00:04:52]The technology did not exist.

[00:04:54]Walton tried first. Working alone, he attempted two different methods of accelerating particles, early prototypes of what would later become the linear accelerator and the betatron.

[00:05:06]Both failed. The available power sources could not generate the necessary energies.

[00:05:11]Walton spent two years building machines that did not work. He wrote later that he had been on the verge of giving up.

[00:05:18]Then, in 1929, a Russian physicist named George Gamow visited the Cavendish and changed everything.

[00:05:27]Gamow, working with Niels Bohr in Copenhagen, had developed a wave mechanical theory suggesting that particles could tunnel through energy barriers rather than having to go over them.

[00:05:38]Translated into practical terms, you did not need millions of volts to penetrate an atomic nucleus. You needed only about 500,000.

[00:05:47]That was a fraction of what everyone had assumed. It was suddenly possible.

[00:05:52]Rutherford gave the green light. Walton was paired with John Cockcroft, [music] a quiet, methodical English physicist who had the engineering skills to complement Walton's experimental brilliance. [music] Together, they began building. The apparatus they constructed was a monster. A voltage multiplier capable of generating 700,000 volts, [music] the kind of electrical equipment that, if it failed, could kill a man instantly. A vacuum tube where protons would be accelerated to near the speed of light.

[00:06:23]A target chamber where the protons would slam into a thin sheet of lithium foil only a few microns thick. A detection screen coated with zinc sulfide that would flash every time a particle struck it. The whole thing filled a basement laboratory at the Cavendish and looked like something from a science fiction film. [music] Coils, glass tubes, copper wires, transformers, and a wooden observation hut barely big enough to hold a single person. Cockcroft and Walton built it themselves with their own hands on a tiny budget over the course of 3 years. The Cavendish was famously underfunded. Rutherford had a saying, "We haven't got the money, so we have to think." Walton and Cockcroft thought. By April 1932, they were ready.

[00:07:12]On the afternoon of the 14th, Walton climbed into a small wooden observation hut beside the accelerator. Cockcroft and Rutherford waited outside. The hut was lined with paraffin wax to shield him from radiation. There was a small viewing port pointed at the zinc sulfide detection screen. Walton's eyes had to adjust to the darkness. The flashes they were hoping to see would be tiny, fleeting, and easily missed. He sat there for several minutes, letting his pupils dilate. Then he switched on the machine.

[00:07:43]The accelerator hummed. The voltage climbed.

[00:07:47]The protons streamed down the tube at speeds approaching the speed of light and slammed into the lithium target.

[00:07:53]On the screen, Walton saw flashes of light, like, in his own words, twinkling stars.

[00:08:01]He counted them.

[00:08:02]He could not believe what he was seeing.

[00:08:05]He climbed out and called Cockcroft over.

[00:08:08]What he was seeing was the splitting of lithium nuclei.

[00:08:12]Each proton hitting a lithium atom was breaking the nucleus apart into two helium nuclei.

[00:08:20]For the first time in human history, an atom had been deliberately, controllably, artificially split.

[00:08:29]The most fundamental particle of matter had been taken apart by hand, by a 30-year-old physicist from a small town in Ireland, in a basement. Walton emerged from the hut and told Cockcroft what he had seen.

[00:08:42]Cockcroft climbed in and confirmed it.

[00:08:45]Rutherford was called. The most famous physicist in the world climbed into the observation hut, switched on the accelerator, and saw the twinkling stars for himself.

[00:08:55]Their Nobel Prize citation, awarded in 1951, would later describe the moment in these words: "Thus, for the first time, a nuclear transmutation was produced by means entirely under human control."

[00:09:09]Walton wrote in a letter to his fiancee, Freda Wilson, who was waiting back in Ireland for him to come home: "Cockcroft and I made what is in all probability a very important discovery in the lab. It opens up a whole new field of work, which may go a long way towards elucidating the structure of the nucleus of the atom."

[00:09:27]He was understating it. The Cockcroft-Walton generator, as their machine came to be known, was the first true particle accelerator. Every accelerator built since, from the cyclotrons of the 1930s to the Large Hadron Collider at CERN today, is a descendant of the machine Walton and Cockcroft built in a Cambridge basement.

[00:09:48]The experiment on April 14th, 1932 opened the door to everything that came after.

[00:09:55]The discovery of new elements, the development of nuclear medicine, the understanding of how the sun produces energy, the principles behind nuclear reactors, the radiation therapies that treat cancer in every hospital on Earth, and yes, [music] the principles behind the atomic bomb.

[00:10:13]Within 13 years of Walton's experiment, the bombs dropped on Hiroshima and Nagasaki would kill over 200,000 people.

[00:10:22]Walton was deeply troubled by this. He had no role in the Manhattan Project. By 1942, he was back in Dublin teaching, but he understood that the experiment he had performed in 1932 had made the atomic bomb possible.

[00:10:38]He spoke later in life about the responsibility of scientists to consider the moral consequences of their work.

[00:10:45]Walton finished his PhD at Cambridge in 1931, actually before the famous experiment.

[00:10:51]He stayed on as a Clerk Maxwell Scholar until 1934.

[00:10:56]And then he made a decision that would shape the rest of his life, and ultimately, the reason almost nobody outside Ireland knows his name.

[00:11:05]He went home.

[00:11:06]>> [music] >> In 1934, at the age of 30, Ernest Walton turned his back on the Cavendish Laboratory, the most important physics lab in the world at the peak moment in its history, and returned to Trinity College Dublin to [music] take up a position as a fellow in the physics department. He had offers to stay in Cambridge. He had offers from other major universities. He turned them all down.

[00:11:31]>> [music] >> He married Frieda Wilson, the woman who had been writing to him from Ireland throughout his years at the Cavendish, the same year. Cockcroft stayed at Cambridge and eventually became director of the Atomic Energy Research Establishment at Harwell, helping to lead Britain's nuclear program during and after the Second World War.

[00:11:52]Walton became a teacher. He gave up cutting-edge research at the center of the scientific universe to teach [music] undergraduates in a country that, in 1934, had almost no scientific infrastructure, no funding, no equipment, [music] and no community of researchers.

[00:12:10]He did it because Trinity had been his dream since he was a boy.

[00:12:15]He did it because he wanted to build Irish science from the inside. He did it because he loved teaching more than he loved fame. [music] He was right about the teaching. By every account, Walt Walton was an extraordinary lecturer, patient, clear, generous with his students, willing to explain anything to anyone.

[00:12:37]He served as Erasmus Smith's Professor of Natural and Experimental Philosophy at Trinity from 1946 until his retirement in 1974.

[00:12:48]He trained generations of Irish physicists. He campaigned tirelessly for better funding for scientific research in Ireland. He spent his career trying to build the kind of laboratory in Dublin that he had once in at Cambridge, and he largely failed because Ireland in the 1930s, the 1940s, and the 1950s simply did not have the money or the political will to fund cutting-edge physics.

[00:13:14]In 1951, almost 20 years after the famous experiment, Walton and Cockcroft were jointly awarded the Nobel Prize in Physics.

[00:13:24]The citation read, "For their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles.

[00:13:33]Walton was 48 years [music] old. He had been a relatively obscure physics professor in Dublin for 17 years by the time the world finally remembered what he had done.

[00:13:43]The Nobel [music] Prize barely changed his life.

[00:13:46]He gave the medal and citation to Trinity College Library just before his death.

[00:13:51]He continued teaching. He continued lecturing. He continued going to the physics department for cups of tea long after he retired.

[00:14:00]He also gave lectures on science and religion.

[00:14:03]Walton was a deeply religious man.

[00:14:06]A lifelong Methodist who saw no contradiction between his scientific work and his faith.

[00:14:12]He once wrote, "One way to learn the mind of the creator [music] is to study his creation.

[00:14:18]We must pay God the compliment of studying his work of art."

[00:14:22]He believed that splitting the atom was in some sense an act of worship, a way of understanding what the universe was actually made of.

[00:14:33]Ernest Walton died on the 25th of June, 1995 in Belfast at the age of 91.

[00:14:41]He left behind four children, generations of students, and an experiment that changed everything.

[00:14:48]The Cockcroft-Walton generator he and his partner built is on display in museums around the world.

[00:14:54]There is a plaque on his birthplace in Abbeyside, Dungarvan.

[00:14:59]The local park is called the Walton Causeway Park.

[00:15:02]Trinity College keeps his Nobel medal in its library.

[00:15:06]And the experiment of April 14th, 1932 is taught in every physics classroom on Earth.

[00:15:13]But ask a hundred people on the street to name the scientist who first split the atom, and you will get answers like Einstein or Oppenheimer or maybe Rutherford. Einstein was a theoretical physicist who never split an atom in his life.

[00:15:27]Oppenheimer did not split the first atom. He built the first bomb based on principles Walton's experiment had established.

[00:15:35]Rutherford was Walton's supervisor. He gave the orders, but he did not build the machine or run the experiment. The man who actually did it, the one who climbed into the hut, switched on the accelerator, and watched the twinkling stars was Ernest Walton from Dungarvan, County Waterford, Ireland. He came home.

[00:15:56]He taught. He died. And the world quietly forgot that the most important experiment of the 20th century was performed by a Methodist minister's son from a small Irish coastal town who learned mathematics in a Belfast boarding school >> [music] >> and changed the universe in a Cambridge basement.

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