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As it ages, white paper turns a distinctive yellow. But why? To find out, scientists artificially aged modern paper to reveal the changes on the molecular level. The research is in the journal Physical Review Letters.
随着年代的久远，白纸会明显发黄。这是为什么呢？为了寻找答案，科学家人为地将现代的白纸老化以揭示其分子水平出现的变化。这项研究成果刊登在《物理评论通讯》上。
For 48 days, three unbleached paper samples aged rapidly in reactors that simulated different environmental conditions. The researchers then compared the artificially aged samples to the real deal: three pieces of paper crafted in 15th century Europe. This technique allowed them to gauge the types and amounts of changes going on.
在48天的时间里，三个原色纸张样品在三个模拟不同环境条件的反应堆中迅速老化。然后，研究人员比较了人为老化的纸张和三张15世纪欧洲的纸片之间的区别。这种方式可以让他们判断出这些纸张在类型和数量上所发生的变化。
About 90 percent of the weight of old paper is cellulose, the sturdy material that makes up plant cell walls. But over time cellulose fibers oxidize. The process modifies parts of various molecules and turns them into what are called chromophores, which absorb light.
旧纸张重量的约90％来自纤维素，这是构成植物细胞壁的坚固材料。但随着时间的推移，这种纤维素会逐渐氧化。这个过程会让各种分子发生改性变化并将其转化成染色体，而染色体会吸收光线。
White paper is white because it reflects all colors of light. Aging paper filled with chromophores reflects wavelengths that make it look yellow. The non-destructive technique used in this study could inform research to preserve and even whiten ancient texts and art. And give paper conservation abrighter outlook.
白纸之所以显出白色因为它可以反射各种光线。而充满了染色体的年代久远的纸张则可以反射那些使它看起来显示黄色的波长。这项研究中使用的非破坏性技术有助于研究如何保持甚至将古代典籍和作品重新亮白。这对纸张保护而言是一个光明的前景。
注：本文译文属可可英语原创，未经允许，请勿转载。
