The Magic Length of the Universe: 21 Centimeters
2025-04-24
The 21-centimeter line, emitted by neutral hydrogen atoms, is a powerful tool for understanding the universe. This specific wavelength, resulting from a hyperfine transition in hydrogen, allows us to map the distribution of gas clouds, trace the history of star formation, and even search for elusive dark matter signals and primordial gravitational waves. Its precision and long-range reach make it a unique probe into the early universe and the cosmos's deepest secrets.