Frozen water butt problems

The other winter, the spell of freezing weather that went on for weeks caused a problem with our water butt. Water freezes from the top down - that's the reason life survived on Earth as it could survive under the ice sheets on frozen oceans. Here, the problem is that it also explands as it freezes. The stuff that freezes first at the top doesn't expand upwards anticipating the lack of space. This means that the stuff that freezes last at the bottom has no space into which to expand. It thus expands downwards, pushing out the flat plastic bottom into a rounded shape. The water butt was free to wobble on its round bottom and it fell over. Water is H2O. The hydrogen atoms in one H2O molecule are attracted to the oxygen atom in the next water molecule. This is called hydrogen bonding. At ordinary temperatures, the heat energy is enough to wobble the molecules out of fixed bonding patterns. But as water freezes, the molecules can form fixed hydrogen bonds, making the H2O into a solid. These fixed bonds give the water a rigid molecular structure, like scaffolding, and this opens up gaps, pushing the molecules apart. Google it for a more scientific explanation and diagrams!

"Copenhagen" radio play

On Sunday night Radio 3 broadcast a long radio play (2 hours) about a meeting during the Second World War between two of the greats of quantum physics, Niels Bohr, who was Danish, and Werner Heisenberg, who was German. The meeting took place in the capital of Denmark, hence the title. It is an important incident for the ethics of science. No one really knows exactly what happened but Heisenberg seemed to want to talk to Bohr about the German atomic bomb programme. I had always thought Heisenberg was regarded as dodgy for continuing to work in Germany at this time, but a bit of Internet research suggests that his "crime" may well have been to avoid becoming a martyr and refusing to defect to America. Here's the link. Listen and see what you think.

http://www.bbc.co.uk/programmes/b01ppwn6