Here’s what you’ll learn in this story:A mysterious metal shard captured the imagination of the American public, because it was supposedly from a 1947 UFO that crashed on Earth. The sample seemed to have an unprecedented material structure that could indicate an extraterrestrial technosignature, or sign of alien technology. That’s why scientists were intrigued when a mysterious shard of metal found on Earth exhibited signs that it might have come from intelligent minds on a distant planet. The sample had an apparently unprecedented material structure that could indicate an extraterrestrial technosignature, or sign of alien technology. Unlike anything in your microwave, bismuth is capable of directing terahertz waves.