'The more we worked on this project, the simpler the answers became,' Harrellson said, adding that the experience 'is very rare in science.'

( E in this equation refers to the elasticity of a material A is a factor that depends on the temperature and humidity of the environment l is the approximate size of biological molecules and λ is the distance over which hydration forces lose their strength). To take one example, the team found that the simple equation E=Al/λ neatly describes how a material's elasticity changes based on factors including humidity, temperature, and molecule size. The simplicity of the formulas that the team found can predict these properties suggests that they're onto something. Previous models of how water interacts with organic matter have required advanced computer simulations to predict the properties of the material. The team found that bringing water to the front and center allowed them to describe the characteristics that familiar organic materials display with very simple math. This research, however, shows that that ambient water is much more central to wood, fungi, plants, and other natural materials' character than we had ever known. Think, for example, of a wooden door, that expands during a humid spell. We have long known that biological materials absorb ambient moisture. This new paper's argument that the hydration force is what defines the character of biological matter almost entirely, including how soft or hard it is, thus comes as a surprise. That pushing force, called the hydration force, was identified in the 1970s, but its impact on biological matter was thought to be limited. As a result, the water molecules push the biological matter's molecules away. But when the molecules that form biological materials combine with water, they tip the balance toward order: Water wants to return to its original state.

When water is in its liquid form, its molecules strike a fine balance between order and disorder. 'This idea may seem hard to believe, but it resolves mysteries and helps predict the existence of exciting phenomena in materials,' Sahin added. We discovered that some skyscrapers aren't supported by their steel frames, but by the air within those frames.' Harrellson, who recently completed doctoral studies in Columbia's physics department, and is an author on the study, used the metaphor of a building to describe the team's finding: 'If you think of biological materials like a skyscraper, the molecular building blocks are the steel frames that hold them up, and water in between the molecular building blocks is the air inside the steel frames. It's a big surprise, an intellectual delight.' 'It's unifying something incredibly diverse and complex with a simple explanation. 'I think this is a really special moment in science,' Ozgur Sahin, a professor of Biological Sciences and Physics and one of the paper's authors, said. In their paper, the authors group these and other materials into a new class of matter that they call 'hydration solids,' which they say 'acquire their structural rigidity, the defining characteristic of the solid state, from the fluid permeating their pores.' The new understanding of biological matter can help answer questions that have dogged scientists for years. Water gives rise to a solid and goes on to define the properties of that solid, all the while maintaining its liquid characteristics. A new paper published today in Nature upends that paradigm, and argues that the character of many biological materials is actually created by the water that permeates these materials.

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