Communal central heating means Moscow can plunge entire neighbourhoods into cold with a single strike

Many Ukrainians are without heating in sub-zero temperatures as a result of relentless Russian strikes on energy infrastructure, while the country suffers through its coldest winter of the war so far.

Ukraine is especially vulnerable to such attacks, as Moscow can exploit a widespread Soviet-era heat system in which multiple apartment blocks rely on communal central heating.

Pressure, frictional heating and a disordered layer of molecules on top of the ice make skating possible

Ice skating is counterintuitive: why should a narrow blade make it easier to slide over the ice? The science is surprisingly complex, but unscientific people worked out the practical application a long time ago.

William FitzStephen described how Londoners entertained themselves in freezing conditions in 1173: “Crowds of young men go out to play on the ice. Some of them fit shinbones of cattle on their feet, tying them round their ankles … and are carried along as fast as a flying bird.”