Tuesday, October 25, 2011

Strange quantum effects of water make life possible

Basically all life is made with water, and carbon molecules. In humans, water can reach up to 80 percent of body weight, highlighting the immense volumes that are used for life. But it seems that only small changes in the laws of physics are needed to completely eradicate the life-giving properties of water. A new study has shown that quantum effects cancel each other out, in order to stabilize the water molecule: H2O. Due to these complicated effects, water is more dense in liquid form, than in solid form, an unique feature that almost no other molecule possesses. The stability of H2O makes that our bodies can use it to maintain temperature, something that would otherwise be impossible.
Water is water due to two quantum mechanical effects that cancel each other out. Due to the so-called Heisenberg's uncertainty principle, no molecule can have a fixed position in respect to others. If this is the case, the network that water molecules create among each other would be severely destabilized, ruining its capabilities for life. So far, it was a mystery why H2O is not unstable, even though this quantum effect is working its way to destabilize the molecule.

H2O connects to its siblings by making so called hydrogen bonds. This means that a connection between a hydrogen atom (H) is formed with an oxygen (O) atom of an other molecule. Varying lengths of these bonds (because there can be no fixed position) destabilize the connection, and therefore the whole network that water forms, either in liquid or solid shape. Because water is stable, it was hypothesized that hydrogen bonds within a single molecule (the bonds connecting the H to the O to form the actual molecule) also vary in length, in a precise way to cancel out the length variation between molecules. By shooting particles at H2O, researchers have now shown that this is indeed the case, revealing why water can exist in the way we see it today.

While varying lengths of atomic bonds between and within molecules may seem like a boring topic, these mechanisms explain to us why water-based life, like ours, can exist. If the quantum mechanical effects of either one of these two principles were a little bit different, the balance would be eradicated, leaving an unstable H2O molecule, not fit for giving life. This seemingly unimportant detail is 'just right' for life, like many more laws of physics in the universe are 'just right'. For example, if certain values in physics formulas were a little bit different, the universe would either tear apart, or crumble on itself. In addition, small changes would make formation of molecules impossible, rendering creation of life impossible.

Scientists have postulated that our 'just right' universe is the reason we are here. If it was not 'just right', we would not been able to be there to measure it. This view is called the Anthropic principle, which also leaves us with the assumption that there are parallel universes in which the laws of physics are different: it would make our existence a little less improbable.


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