Think of a baby mobile: figurines dangling on threads, twitching at even a whisper of breeze. In the same way, planets on very wide orbits barely cling to their star's gravity, and they feel the faintest gravitational drafts. Astronomers have proposed turning such planets into detectors of dark matter. This invisible substance doesn't glow, yet its gravity governs the motion of stars and galaxies.

It is thought that after the Big Bang, superdense clumps of dark matter formed. When such a clump passes by, it would gently 'rock' a distant planet, and modern exoplanet surveys (like observing a planet as it crosses the face of its star, transit) could spot that shift. We'll get a map of invisible masses and learn what lumps and bumps existed right after the birth of the Universe.

The most surprising part: a clump the size of our Solar System could weigh as much as a star yet remain perfectly transparent, and to catch it, you need the most 'wobbly' planets in the entire Galaxy.