Why does a rainbow always appear at 42°, why is it actually a full circle rather than a semicircle, and why does everyone see their own rainbow? The surface physics of the rainbow — refraction, one internal reflection, and dispersion inside a single water droplet.
Why do water droplets bead up and roll off a lotus leaf instead of soaking in? The answer is not smoothness but an invisible, two-tier roughness. Hydrophobic wax (chemistry) multiplied by micro- and nano-scale roughness (structure) pushes the contact angle past 160°, and the rolling droplets carry the dust away with them.
The Divine Bell of King Seongdeok (the Emille Bell), cast more than 1,200 years ago, still swells and fades as if breathing — not by mystery but by a beat. A slight asymmetry splits one vibration into two, creating rhythms of about 3 and 9 seconds. We also revisit the Emille legend through the bell’s own inscription.
In 2025 a third visitor from beyond the solar system, 3I/ATLAS, passed through. How do we know it came from outside? Its unclosing hyperbolic orbit is the decisive proof. We calmly walk through its CO2-rich composition, its estimated age, and the alien-technology controversy that once arose.
In the octopus, about two-thirds of its roughly 500 million neurons are distributed across the arms, not the central brain. Though effectively color-blind, it melts into the background in a fraction of a second. We trace its three-layer skin and the principle of distributed neural control through the research.
The Jagyeongnu, built by Joseon in 1434, was an automatic time-announcing water clock that sounded the bell, drum, and gong on its own every hour, with no one watching. The original built by Jang Yeong-sil and others is lost, but the records of the “Borugak-gi” have kept its intricate working principle alive to this day.
