The Hidden Story Behind When Was Helium Discovered—and Why It Changed Science Forever
The sun’s corona, a searing halo of plasma, had long baffled astronomers. During the total solar eclipse of July 18, 1868, a French astronomer named Pierre Janssen trained his spectroscope on the sun’s outer atmosphere—and saw something impossible. A yellow line in the spectrum, unmatched by any known element on Earth. Unknown to him, he … Read more
