Quite an oddity (Image: Shinichi Maruyama

We are confronted by many mysteries, from the nature of dark matter and the origin of the universe to the quest for a theory of everything. These are all puzzles on the grand scale, but you can observe another enduring mystery of the physical world – equally perplexing, if not quite so grand – from the comfort of your kitchen. Simply fill a tall glass with chilled water, throw in an ice cube and leave it to stand.

The fact that the ice cube floats is the first oddity. And the mystery deepens if you take a thermometer and measure the temperature of the water at various depths. At the top, near the ice cube, you’ll find it to be around 0 °C, but at the bottom it should be about 4 °C. That’s because water is denser at 4°C than it is at any other temperature – another strange trait that sets it apart from other liquids.

Water’s odd properties don’t stop there (see “Water’s mysteries”), and some are vital to life. Because ice is less dense than water, and water is less dense at its freezing point than when it is slightly warmer, it freezes from the top down rather than the bottom up. So even during the ice ages, life continued to thrive on lake floors and in the deep ocean. Water also has an extraordinary capacity to mop up heat, and this helps smooth out climatic changes that could otherwise devastate ecosystems.

Yet despite water’s overwhelming importance to life, no single theory had been able to satisfactorily explain its mysterious properties – until now. If we can believe …