At Trinity College's defense session, Li Qiwei spoke with easy eloquence under the gaze of more than two hundred people.
"More than two thousand years ago, in Ancient Greece, scientists of the Pythagorean School believed that light was a stream of tiny particles."
"There was no particular reason for it. Light was simply so commonplace that intuition said it ought to be made of particles."
"But Aristotle, one of the ancient sages, believed that light traveled like ripples on water. Very few people agreed with him, however."
"And so, the view that light was made of particles persisted for nearly a thousand years, without much progress."
"Until 1655, when the Italian mathematician Grimaldi discovered that if an object was placed under sunlight, the edges of its shadow would be blurred."
"So Grimaldi wondered whether light, like water waves, could bend around obstacles and slip behind objects, making the boundary between light and dark less sharply divided."
"So he conducted an experiment, passing a beam of light through a small hole and shining it onto a screen in a dark room."
"But he discovered that after passing through the hole, the patch of light on the screen became noticeably wider. This phenomenon was very similar to water waves."
"Thus, he believed that light might be a fluid capable of moving in wave-like form, and he was the first to propose the concept of [light diffraction]."
"Grimaldi therefore became the earliest advocate of the wave theory of light, shattering people's ingrained understanding of the particle theory of light."
Everyone in the classroom listened in silence. Li Qiwei's plain and accessible language had won them over, and they actually developed a flicker of interest in physics.
"Afterward, the British scientist Hooke inherited Grimaldi's ideas. He conducted experiments observing the colors on soap-bubble films