Ian Johnston, Open University
If you look at a pile of sand close up, you will see that the grains at the edge can be piled in many different ways. Sometimes there might be a cliff (one grain on top of the other), sometimes a flat step and sometimes, perhaps, a valley. If you move a bit further away, though, the surface looks smooth and at a fairly constant slope. Now drop a grain of sand onto the pile. Sometimes nothing happens: it stops where it hits. Sometimes it will go tumbling down the side of the pile. Sometimes it will cause an avalanche - one grain of sand will cause hundreds, thousands or more to come tumbling down. Similar behaviour happens in many different systems, from the microscopically tiny to the astronomical, and in both natural and artificial systems. They are called Self Organising Critical Systems - critical means that they are always on the point of doing something more or less dramatic!
The linked projects give students the chance to carry out experiments to investigate what happens, to make hypotheses, and use their data to see how correct these are.