Why 21 cm is our Universe's "magic length"

a year ago

The 21 cm wavelength is a critical length in the Universe due to the hyperfine transition in hydrogen atoms.
Hydrogen atoms have a 50% chance of forming with aligned spins (proton and electron), which is a higher-energy state than anti-aligned spins.
The transition from aligned to anti-aligned spins emits light at precisely 21 cm wavelength, a key signal in astronomy.
This 21 cm radiation is the narrowest and most precise transition line known in atomic and nuclear physics.
The 21 cm signal can reveal early Universe conditions, star formation history, and even primordial gravitational waves.
Measuring 21 cm radiation helps detect hydrogen-rich regions, even those without stars, providing insights into cosmic evolution.
Future experiments, like LOFAR and lunar-based arrays, aim to map 21 cm signals to uncover the Universe's hidden secrets.

Hasty Briefsbeta