X-Ray

Röntgen discovered X-rays while experimenting with cathode rays in a completely darkened room—he noticed a fluorescent screen across the room was glowing even though his apparatus was covered. The discovery was so serendipitous that he initially thought his eyes were deceiving him. Within weeks of realizing he'd found a new form of radiation, he took the first medical X-ray: his wife's hand, complete with her wedding ring, which she reportedly found so disturbing she declared "I have seen my death."

Within a year of Röntgen's 1895 announcement, X-ray machines were being used on battlefields to locate bullets in wounded soldiers. The technology spread faster than almost any medical innovation before or since—hospitals worldwide adopted it within months, not years or decades. This breakneck adoption happened despite no one understanding the health risks, leading early radiologists to suffer horrific radiation burns and cancers before safety protocols emerged.

For nearly 50 years (1920s-1970s), shoe stores featured X-ray fluoroscopes where customers—especially children—could wiggle their toes and watch their foot bones in real-time to ensure proper shoe fit. These machines delivered radiation doses up to 13 times higher than a modern chest X-ray, and some children visited them repeatedly for entertainment. It took decades of mounting evidence before these "shoe-fitting fluoroscopes" were finally banned, illustrating how wonder can override caution.

X-rays work precisely because they interact differently with various materials—dense calcium in bones absorbs them, while soft tissue lets them pass through. This same principle now lets us examine everything from airport luggage to priceless paintings hiding earlier artworks beneath. Art historians use X-ray fluorescence to detect forged masterpieces and discover how Renaissance artists changed their minds mid-painting, revealing creative processes invisible to the naked eye.

Röntgen won the first-ever Nobel Prize in Physics in 1901 for X-rays but deliberately refused to patent his discovery or accept commercial benefits, believing it should belong to humanity. He donated his Nobel prize money to his university and died in relative poverty after World War I. Had he patented X-ray technology, he would have been one of history's wealthiest individuals—instead, his decision enabled the rapid global spread that saved countless lives.

While Earth's atmosphere blocks celestial X-rays (thankfully, or we'd all be fried), space telescopes like Chandra have revealed that X-rays flood the universe from exotic sources like black holes and neutron stars. These cosmic X-rays tell us about some of the most violent and energetic events in existence—supernova explosions, matter spiraling into black holes at millions of degrees. The same radiation that lets doctors see your broken bone also reveals the universe's most extreme physics, connecting the medical and the cosmic.