The Lighter, the Better?

In the present paper various aspects of lightness of spatial structures are discussed. In the development of spatial structures there has been a continuing trend of seeking for ever lighter roof structures. This is first observed in a graph of unit weights of the roof structures of historically known buildings against the time coordinate. In the middle of the nineteenth century toward the beginning of the twentieth a few genius engineers developed this desire to a surprising extent with their innovative ideas and thoughtful judgments. By the second half of the twentieth century men have already observed the minimum extremity in lightness of the roof structures. Then comes the question: the lighter, the better? The answer is that it is not always so, if the roof is already light enough. What is more important of the roof structures than lightness is discussed. Finally the lightest big structure that has ever been realized by the author is mentioned.