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大約在1610至1638年的某一個晚上，繁星點綴山谷城鎮佛羅倫斯，山谷兩旁相隔約1.5公里的兩個小山丘上分別聚集兩批人，他們各有一個用黑布覆蓋的大燈籠。這並非秘密的軍事偵察，因為負責這次行動的人是伽利略，他正準備進行一次史無前例的測量光速實驗。伽利略的理念是在一處地方先把燈籠的黑布揭起，當另一處的人看到燈籠發出的光，便立刻把用來遮蔽燈籠的黑布也同時揭開，就可藉測量燈光來回所需的時間，算出光的運行速度。但伽利略因選擇的測量距離太短而失敗。1676年，奧勒．羅默在計算木星的衛星方位時，卻受到木星距離變化而影響計算成果，因而意外測得光速。
The First Scientist who Measured the Light Speed
The stars twinkled over the valley city of Florence. A small group of men, with a big lantern covered up, stood on the top of the hill. Looking across the city to another hill on the other side, some 1.5 kilometers away, was a similar group of people. It was sometime between 1610 and 1638. Galileo was carrying out a scientific experiment to measure the speed of light. His idea was to let the first group uncover their lantern and the second group, upon seeing the light, would do the same immediately. The time for the light to travel back and forth should enable him to calculate the speed of light. But Galileo had adopted a distance far too short for his crude setup. It was not until 1676 that Ole Romer, while trying to predict the positions of the Jovian satellites, accidentally unveiled this secret. ■甄枝強 資深天文愛好者
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