Booze is prime territory for the appliance of science. But while we normally use biology to explain bad hangovers or chemistry to create new cocktails, there's plenty of science lurking within your humble glass of beer, too.
In fact, the UK's Institute of Physics has launched a Christmas website based on beer, to help explain some of the more peculiar scientific phenomena hidden in your ale. Like, for instance, why the bubbles in your pint of stout fall instead of rising:
As your pint of stout settles, the bubbles in the centre of the glass (where you can't see them) ARE rising to the surface, but at the same time the bubbles touching the wall of the glass experience some drag which prevents them from floating upwards.
Or why the head of your beer is white, even though the liquid itself is amber or brown:
The whiteness of the head comes from the way that light travels through it. The head is a foam made up of loads of bubbles crammed in close together, and each individual bubble is a pocket of gas surrounded by a thin wall of beer. Light traveling through the foam passes through a large succession of bubble walls and is scattered, reflected and refracted in an equally large succession of different directions. The light that exits the foam and enters your eyes is therefore a mix of all different wavelengths of light and appears white rather than brown.
Image by St0rmz under Creative Commons license