Fed Governor Daniel Tarullo said Europe's debt woes, if not contained, could cause financial markets to freeze and spark a global crisis akin to the market meltdown of late 2008.

One cold evening in late autumn, Jenny sat shivering over her fire, drinking broth out of a wooden bowl, when a spark flew from the fire and lit her skirts on fire.

It was in the 1980s that the late neuroscientist Benjamin Libet saw a spark of brain activity 300 milliseconds before subjects consciously chose to twitch a finger.