Two more Try Your Skills exercises are now available. Both are at the Middle level.
The first of these, II.6 Measuring the Earth - Moon Distance with a Laser, concerns a very basic type of measurement. You will learn about the way this is done from an observatory in France (CERGA) and be astonished how good the accuracy really is!
The second is about II.6 Measuring the Distances to the Galaxies by means of Cepheid variables. and provides a very useful supplement to the information available in the Collaborative Project on variable stars.