Until the End of Time: Mind, Matter, and Our Search for Meaning in an Evolving Universe

by Brian Greene

The distribution of electrical charge across a water molecule might seem like an esoteric detail. But it’s not. It proves essential to the emergence of life. Because of water’s skewed charge distribution, it can dissolve nearly everything. The negatively charged oxygen vertex grabs hold of anything with even a slight positive charge; the positively charged hydrogen tips grab hold of anything with even a slight negative charge. In tandem, the two ends of a water molecule act like charged claws that pull apart most anything that’s submerged for a sufficient time. Table salt is the most familiar example. Composed of an atom of sodium bonded to an atom of chlorine, a molecule of table salt has a slight positive charge near the sodium (which donates an electron to the chlorine) and a slight negative charge near the chlorine (which accepts an electron from the sodium). Drop salt into water, and the oxygen side of H2O (negatively charged) grabs hold of the sodium (positively charged), while the hydrogen side of H2O (positively charged) grabs hold of the chlorine (negatively charged), ripping salt molecules apart and dissolving them into solution. And what’s true for salt is true for a great many other substances too. The details vary, but water’s asymmetric charge arrangement makes it an uncanny solvent. Wash your hands, even without soap, and water’s electrical polarity will be hard at work, dissolving foreign matter and carrying it away.