Have you ever wondered what lies beneath the ocean floor? Besides the colorful corals and exotic fish, there are also hidden treasures that can reveal the secrets of the universe. These treasures are not gold or jewels, but old pieces of metal that have been sitting in shipwrecks for centuries.
These metal pieces are called low-background steel, and they are very valuable for scientists who are looking for dark matter, an invisible substance that makes up most of the matter in the cosmos. Dark matter is one of the biggest mysteries of physics, and it can only be detected by very sensitive instruments that can pick up its faint signals.
But these signals are often drowned out by the noise from other sources of radiation, such as the sun, the earth, and even modern steel. Modern steel is contaminated by radionuclides, which are radioactive atoms that come from atmospheric nuclear testing and the use of atmospheric gas in steel production.
Low-background steel, on the other hand, has less radioactive contamination than modern steel, because it was produced before the first nuclear bombs were detonated in the 1940s and 1950s. It is typically sourced from shipwrecks and other steel artifacts of this era, such as pre-World War II buildings and medical equipment.
By surrounding their detectors with low-background steel, scientists can shield them from unwanted radiation and increase their chances of finding dark matter. “It’s sort of like gold dust,” says Chamkaur Ghag, a physicist at University College London who uses low-background steel for his experiments.
But low-background steel is scarce and expensive, and some shipwrecks are illegally scavenged for it, posing ethical and historical concerns. Some of these shipwrecks are war graves that contain human remains and cultural heritage. Some are also protected by international laws and treaties that prohibit their disturbance.
The demand for low-background steel is not only driven by science, but also by other industries that need radiation-free metal for sensitive applications, such as Geiger counters and spacecraft sensors. As more and more shipwrecks are plundered for their precious cargo, the question arises: how much are we willing to sacrifice for the sake of knowledge?
– 2321: Low-Background Metal – explain xkcd, explain xkcd, May 11, 2022
– Why the Search for Dark Matter Depends on Ancient Shipwrecks, The Atlantic, October 25, 2019
– Lost bones, a mass grave and war wrecks plundered off Indonesia, The Guardian, March 2, 2018
– Low-background steel – Wikipedia, Wikipedia, not available