Mathematicians and psychologists don't cross paths that often and when they do you wouldn't expect it to involve an (apparently) unassuming puzzle like the Tower of Hanoi. Yet, the puzzle holds fascination in both fields.

Ocean waves are not moving walls of water. Instead, it's some kind of energy that moves along. But then, what happens to the water itself? This isn't just an idle question to ponder while watching the ocean — its answer may help protect us from it too. And it requires some sophisticated maths.

At the beginning of July Plus went to the European Congress of Mathematics in Krakow! Around 1,000 mathematicians came together there for a week-long programme of talks and seminars. To give you an idea of what it was like we chatted to several of them during one of the coffee breaks.

The 6th European Congress of Mathematics, which took place in Krakow at the beginning of July, wasn't just about mathematicians talking to each other. On the streets of Krakow maths buskers were entertaining the public, handcuffing innocent Krakowians, constructing emergency pentagons and reading minds. So what is maths busking all about? We caught up with Sara Santos, the director of the project, and one of her volunteers to find out.

Greetings from the beautiful city of Krakow, where the 6th European Congress of Mathematics has opened today! Around 1,000 mathematicians, donning hats, fans and flip-flops to resist the incredibly hot weather, have come together here to chat, share and listen to lectures, and Plus will be reporting from the congress all week.