How Physicists Accidentally Transformed Lead into Gold at the Large Hadron Collider

Medieval alchemists fantasized about turning lead into gold. Fast forward to today, and science tells us that lead and gold are distinct elements. A lead atom has three more protons than a gold atom. But can we convert lead into gold by simply removing those three protons?

Surprisingly, the answer is yes, but it’s a complex process.

Physicists at the Large Hadron Collider in Switzerland have, through their ALICE experiment, stumbled upon a method to produce small amounts of gold. In their experiments, they created approximately 29 trillionths of a gram of gold by colliding lead atoms at high speeds—mimicking conditions shortly after the Big Bang.

So, how does one extract protons from lead? Protons reside in an atom’s nucleus. While protons carry an electric charge and can be influenced by an electric field, they are also held tightly in place by the strong nuclear force. This force is extremely powerful and requires an electric field about a million times stronger than what lightning generates.

To create such a fierce electric field, scientists accelerate lead nuclei to nearly the speed of light and collide them. During these collisions, lead nuclei can either crash into each other or just barely miss. A direct impact destroys both nuclei. However, when they have a near-miss, their electric fields interact, creating strong enough forces to “shake” out some protons.

Occasionally, a lead nucleus will lose exactly three protons, transforming into gold. But how do scientists know this transformation has occurred? They can’t directly observe gold nuclei, so they use detectors known as zero-degree calorimeters to count the protons that have been removed from lead nuclei.

In fact, during these rapid-fire collisions, ALICE scientists estimate they produce about 89,000 gold nuclei per second. They also create other elements, like thallium (with one proton removed) and mercury (with two).

Interestingly, while this process reveals fascinating insights into atomic behavior, the gold produced is more of a nuisance than a treasure for scientists. Once a lead nucleus loses protons, it doesn’t stay on course and can collide with the collider’s walls within microseconds. This effect reduces the intensity of the particle beam over time, complicating future experiments.

Despite the challenges, understanding this accidental transformation helps scientists refine their methodologies and structures for even bigger experiments ahead. It’s a modern twist to an ancient dream—where alchemy unexpectedly meets cutting-edge physics.

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