Southman

I am In Nam, the editor of glu.kr. Under the mission “God Loves U: learn, discuss, and explain all things that God created,” I write across six areas — culture, history, science, plants, animals, and climate. Every article begins as an AI-assisted draft, then goes through source checks, numerical verification, and terminology review before I read and edit it myself for publication. Images carry their source and license, with freely licensed material preferred. If you find an error, write to south-man@daum.net. I verify it, correct the article, and note the change.

A Rainbow Isn’t a Semicircle — It’s a Circle: The 42° Geometry Drawn by a Single Raindrop

2026-07-012026-07-22

들판 위 하늘에 걸린 선명한 1차 무지개, 바깥이 붉고 안쪽이 보라색인 반원 호

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… Read More »A Rainbow Isn’t a Semicircle — It’s a Circle: The 42° Geometry Drawn by a Single Raindrop

It Repels Water Not by Being Smooth, but by Being Rough — The Surface Physics of the Lotus Effect

2026-07-012026-07-22

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… Read More »It Repels Water Not by Being Smooth, but by Being Rough — The Surface Physics of the Lotus Effect

Why a 1,200-Year-Old Bell Seems to Breathe: The Secret of the Divine Bell of King Seongdeok’s Beat

2026-07-012026-07-22

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… Read More »Why a 1,200-Year-Old Bell Seems to Breathe: The Secret of the Divine Bell of King Seongdeok’s Beat

The Third Visitor from Beyond: 3I/ATLAS — How Do We Know It Came From Outside the Solar System?

2026-06-302026-09-21

허블 우주망원경이 촬영한 성간 천체 3I/ATLAS의 푸른 먼지 코마와 배경 별 궤적

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… Read More »The Third Visitor from Beyond: 3I/ATLAS — How Do We Know It Came From Outside the Solar System?

An Animal with Nine Brains: How an Octopus Hides Its Body in 0.3 Seconds

2026-06-302026-07-13

common octopus Octopus vulgaris camouflage on reef (hero)

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… Read More »An Animal with Nine Brains: How an Octopus Hides Its Body in 0.3 Seconds

The Clock That Struck the Bell by Itself: the Jagyeongnu — Joseon’s Automatic Water Clock Revived by Records

2026-06-292026-09-21

복원된 자격루 전체 모형, 여러 개의 물항아리와 시보 장치가 단 위에 놓인 모습

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,… Read More »The Clock That Struck the Bell by Itself: the Jagyeongnu — Joseon’s Automatic Water Clock Revived by Records