Cosmic Hydrogen Catches Gravitational Waves ✎ express
Hydrogen is the most common element. Its atoms are like antennas: they emit and absorb light at very specific frequencies. Einstein predicted that spacetime can ripple: these are gravitational waves. It turns out, clouds of hydrogen can also capture them: the energy of gravitons from ordinary stars precisely matches the resonance of hydrogen atoms. An atom that gains energy releases it either as light or as a gravitational wave. By comparing a cloud's glow with expectations, scientists calculate the fraction that went into gravity. This way, we can detect gravitational tremors from any objects, from individual stars to black hole mergers, and build a gravitational map of the Universe.
Gravitons twist spacetime twice as much as photons, which is why gravitational waves interact so weakly with matter.
In the film 'Interstellar', the characters communicate via gravity. The new method shows that we can pick up the gravitational whispers of distant stars using ordinary hydrogen.