The beauty and clearness of the dynamical theory, which asserts heat and light to be modes of motion, is at present obscured by two clouds. The first came into existence with the undulatory theory of light, and was dealt with by Fresnel and Dr. Thomas Young; it involved the question, how could the earth move through an elastic solid, such as essentially is the luminiferous ether?
The beauty and clearness of the dynamical theory, which asserts heat and light to be modes of motion, is at present obscured by two clouds. The first came into existence with the undulatory theory of light, and was dealt with by Fresnel and Dr. Thomas Young; it involved the question, how could the earth move through an elastic solid, such as essentially is the luminiferous ether?
"在我眼裡，我們已經取得的關於運動和力的理論是無比優美而簡潔明晰的，這些理論斷言，光和熱都不過是運動的某種表現方式（熱是分子的運動，光是電磁波的運動）。但是我們卻看到，在經典物理學這片藍天上有兩朵小烏雲讓我們感到有些不安。自從菲涅爾先生和托馬斯·楊博士創立了光的波動學說以來，我們一直都在苦苦尋覓一個問題的答案，那就是：我們的地球是如何在以太中航行的？以太這種被我們稱為‘彈性固體’的看不見摸不著的物質存在的證據又在哪裡？這就是我要說的第一朵烏雲。”