During the long history of mankind, the planet of earth seemed to be an infinitely large place. The earth was so immense that the impact of human activities to the biosphere seemed quite negligible. But after the industrial revolution and especially in the twentieth century things have changed dramatically. World population increased from 1.5 billion to 6 billion in the twentieth century and has reached 7.2 billion this year. And with the advancement of communication and transportation, the earth has shrunk in relative terms. This sudden transition from "unlimited earth" to a "limited earth" has extremely significant consequences, yet the development of human society, moving along the track of infinity for a long time, has not seemed to be able to adapt to the new reality that the earth is "limited". On the "limited earth", perhaps the most important challenges for scientists are problems related to the climate change and environmental degradation, together with unsustainable production and consumption. Without immediate action and transformation, the survival of human society will be seriously threatened. This is the first time in human history that all human beings on earth have been faced with learning to work together and live together as one family in a global village – the time for finally realizing that the planet Earth on which we live is only finite in space, capacity and natural resources. Our future depends entirely on how effectively the entire world would function as a community. This is a necessary awakening – vital for the survival and sustainable development of mankind. I believe that if we make the correct choice at this crossroads, then the 21st century is likely to be marked as the great turning point, or great transition – the beginning of a new era in the history of mankind.

在人類漫長的歷史中，地球似乎是一個無限大的地方。地球是如此地龐大，以至於人類活動對生物圈的影響是可忽略的。但是在工業革命之後，尤其是二十世紀之後，事情有了劇烈的改變。在二十世紀，全球人口從15億增加到60億，今年已增加到72億，再加上通訊與交通的進步，地球相對上「縮小了」。從「無限」的地球，到「有限」的地球，這一個突然的轉變，有著非常顯著的影響。然而，人類社會的發展，長久以來循著無限地球的軌跡，似乎無法接受地球是有限的新事實。在這個有限的地球上，科學家最重要的挑戰，或許是在氣候變遷、環境劣化，以及無法永續的生產與消費等相關的議題。若無立即的行動與改變，人類社會的存續將面臨嚴重的威脅。 在人類歷史上，這是第一次，地球上的全體人類要面臨學習一起努力、一起生活，如同在地球村中的一家人一樣 ─ 人類終於要體認到，我們所在的地球，無論在空間、容量、和在自然資源上，是有限的。我們的未來完全決定於，整個世界是否能有效率地像一個社區一樣運作。這是一個必要的覺醒、人類之存活與永續發展的關鍵。我相信如果我們在這個十字路口上做了正確的選擇，二十一世紀將會被標示為偉大的轉捩點，或是人類歷史上新紀元的開始。 （感謝中央研究院原子與分子科學研究所林志民教授協助翻譯）