Every year, doctors order as many as 40 million medical imaging scans that require a radioactive isotope called technetium-99m (Tc-99m). The scans help them diagnose cancer, heart disease and other serious maladies.
Working in the late 1700s, Spallanzani showed that blindfolded bats could still catch flies and find their way around. But they failed miserably when he sealed up their ears. His discovery of the bat’s “sixth sense,” called echolocation, launched the science of ultrasound.
