The laughter of the ancient alchemists
Since ancient times researchers dreamed of turning one metal into another, especially transforming tin and lead into gold. Out of that dream emerged the parascientific path of alchemy, where practical knowledge of material reactions mingled with mysticism. Alchemists pursued a philosopher’s stone that would glorify metals, cure diseases, and restore youth when ingested.
Alchemists did not succeed at transmuting metals. At best they coaxed a golden alloy with sulfur. Yet their work paved the way for modern chemistry, which holds that matter is conserved. The 18th-century chemist Antoine Lavoisier summarized this idea: nothing is created or destroyed in a chemical change, and the total amount of matter remains constant before and after a reaction, with elements simply rearranged. The craft of experimentation in chemistry rests on this principle.
Put simply, after a reaction the same atoms exist in the same total quantity as at the start. If anything other than water appears inside a container during the burning of hydrogen in oxygen, it signals contamination from outside. This fundamental truth still appears in first-year chemistry courses.
Bohr and the Fifth Washington Conference on Theoretical Physics in 1939 became a turning point. Niels Bohr spoke on a topic that would change science: atoms consist of a nucleus and a surrounding cloud of electrons, the nucleus housing protons and neutrons that define the element. Uranium nuclei can fuse into two barium nuclei with roughly half the mass. Edward Teller recalled a colleague’s reaction before the talk, noting the audacity that uranium might be fissile. The room buzzed with the sense that something profound was unfolding.
During Bohr’s talk, an announcement in the audience hinted at an urgent need for a new sample in the accelerator. After Bohr finished, physicists scrambled to verify his claims, dialing labs and gathering data. Within weeks, multiple teams independently tested the idea, confirming that certain nuclei could transform under the right conditions. It is often said that scientists began to observe real conversions of elements, a milestone ancient alchemists could hardly imagine. The transformation of uranium into lighter nuclei revealed the power and consequences of nuclear processes.
Was this the first conversion?
Physicists did not wait for a formal discovery to notice exceptions to Lavoisier’s rule. By the end of the 19th century, researchers found that some elements radiate spontaneously, a property called radioactivity. Early 20th-century work showed radioactive elements emit three kinds of rays: alpha, beta, and gamma. Ernest Rutherford demonstrated that beta rays are electrons and that alpha rays are helium nuclei, laying the foundation for understanding radioactive decay.
Experiments showed that radioactive substances gradually break down, transforming into different elements along predictable paths. In alpha decay, matter shifts two places back in the periodic table and the mass drops by four. Beta decay moves matter forward by one position without changing the mass. Through these processes, uranium can become thorium, thorium can become radium, radium can become radon, radon can become polonium, and polonium can become lead. Likewise, beta emissions can transform thorium into protactinium and actinium into thorium, among other changes. Chemically identical atoms of radioactive materials can decay at different rates, leading to the concept of isotopes.
From this data emerged the view that many substances share a common nature at the atomic level and that nuclei follow consistent rules. In the 1930s, physicists proposed that the atomic nucleus behaves like a liquid drop capable of splitting and merging, allowing elements to transform. Removing two protons from radium would yield radon, and those protons are the core of helium. The chemical properties of an atom largely depend on the number of protons, while isotopes arise from varying numbers of neutrons.
In the 1920s and 1930s, researchers observed transformations beyond metals. For instance, during experiments nitrogen appeared to convert into oxygen. If the nucleus behaves like a drop of liquid that can split and combine, the shock of uranium fission becomes understandable.
new energy source
All results pointed to a single truth: the atomic nucleus is held together by incredibly strong forces, once called strong interactions. It seemed impossible to strip anything larger than an alpha particle from a nucleus, suggesting limited transmutations to adjacent elements in the periodic table.
In 1938, German scientists Otto Hahn, Fritz Strassmann, Lise Meitner, and Otto Frisch irradiated uranium with neutrons and expected radium, a four-position shift in the periodic table produced by two alpha decays. Instead, they faced a surprise comparable to the early days of radiochemistry. Radium and barium share many chemical similarities, but their behavior in solution differed in rate of accumulation. The team tested samples and confirmed that the observed product matched radium in behavior, validating a path to new nuclear reactions.
Later, physicists recognized that what looked like an explosion inside the nucleus was real. Chemists and nuclear scientists debated the naming and interpretation, as reflected in archival notes from late 1938. A key question remained: where could the energy come from? Otto Frisch and colleagues discussed in a casual setting how energy could emerge from such reactions, realizing that the mass difference implied by the energy balance formula could account for vast energy release. This breakthrough explained why Bohr’s report carried enormous implications for science and society.
The discovery opened the door to extracting large amounts of energy from nuclear processes. If controlled, this energy could power cities gradually; if released abruptly, it could unleash enormous forces. The next step was figuring out how to harness it safely and reliably for civilian use, outside the context of wartime research. In the same era, researchers explored whether heavier elements could be produced from lighter ones through fusion.
As for gold and the dream of medieval alchemy, there are pathways to forging heavier elements from lighter ones through nuclear reactions. By the mid-20th century, experiments demonstrated the possibility of creating tiny amounts of gold from mercury under controlled conditions. The costs and challenges, however, make practical alchemy impractical for real wealth, underscoring the gap between myth and modern physics.