The 1908 experiment that turned oxygen into gold

The Race to Absolute Zero

By 1908, every element on the periodic table had surrendered to the cold—except one. Hydrogen liquefied at 20 Kelvin in 1898, oxygen at 90 Kelvin decades earlier, but helium stubbornly remained a gas no matter how low experimenters drove the temperature. The Dutch physicist Heike Kamerlingh Onnes at Leiden University had spent fifteen years building the world's most sophisticated cryogenic laboratory, a cathedral of glass coils and copper pipes that could produce temperatures within a few degrees of absolute zero.

On July 10, 1908, after an all-night session and multiple equipment failures, Onnes watched liquid helium collect at the bottom of his apparatus at 4.2 Kelvin—minus 452 degrees Fahrenheit. His notebook records the moment with uncharacteristic emotion: "It is a wonderful sight." The liquid appeared so clear and still that Onnes initially suspected his glassware was simply empty, the helium gas having leaked away. Only by shining a light at an angle and observing the meniscus—the curved surface of the liquid—could he confirm that this ghostly, almost invisible substance was real.

The Leiden Cryogenic Empire

Onnes had transformed Leiden into what contemporaries called the "coldest spot on Earth." Starting in 1894, he established a liquefaction cascade system requiring liquid oxygen (90K) to cool hydrogen gas into liquid hydrogen (20K), which then provided the refrigeration necessary to attack helium. His team included master glassblower Gerrit Flim, whose hand-blown Dewar flasks and vacuum-jacketed transfer tubes were technological marvels that institutions worldwide tried unsuccessfully to replicate.

The laboratory consumed massive amounts of helium, then an exotic gas extracted from natural gas wells in Kansas and shipped across the Atlantic at extraordinary expense. A single liquefaction attempt required 360 liters of liquid oxygen, 80 liters of liquid hydrogen, and twenty liters of helium gas—representing months of accumulated resources. When word spread of Onnes's success, James Dewar at the Royal Institution in London, who had narrowly missed the discovery, reportedly refused to speak to colleagues for weeks.

Properties Beyond Imagination

What Onnes discovered in his liquid helium was stranger than mere cold. At 2.17 Kelvin—achievable by reducing pressure above the liquid—helium underwent a phase transition into what became known as "helium-II" or superfluid helium. This substance defied physics as understood in 1908: it flowed upward against gravity, leaked through molecularly sealed containers, and conducted heat hundreds of times better than copper. Onnes observed it creeping up the walls of its container in defiance of surface tension, forming films just atoms thick.

These properties seemed so impossible that Onnes spent years documenting them before publication, fearing ridicule from the scientific community. His 1911 discovery of superconductivity—electrical resistance dropping to absolute zero in mercury cooled by liquid helium—only deepened the mystery. These phenomena would require quantum mechanics, not developed until the 1920s, to explain. Wolfgang Pauli and Lev Landau would eventually show that helium-II represented a quantum state of matter where individual atoms lost their identity.

Legacy in the Modern World

Onnes received the 1913 Nobel Prize in Physics, and his techniques revolutionized experimental science. Today, liquid helium remains the essential coolant for superconducting magnets in MRI machines, the Large Hadron Collider at CERN, and quantum computers. Every MRI scan performed worldwide—over 100 million annually—depends on liquid helium maintaining superconducting electromagnets at 4.2 Kelvin. NASA uses it to cool infrared space telescopes like the James Webb Space Telescope to detect the universe's earliest galaxies.

Yet the helium Onnes used so liberally has become a crisis. Formed by radioactive decay deep underground over millions of years, helium escapes into space once released and cannot be recovered. Global shortages threaten medical imaging and quantum research. The Federal Helium Reserve in Texas, established in 1925, contained one billion cubic meters but neared depletion by 2018. Onnes's achievement opened new realms of physics while inaugurating humanity's dependence on an irreplaceable element—one that, once liquefied and boiled away, is lost forever to the cold darkness of space.