Why does an unpeeled orange float when a peeled one sinks to the bottom? How do you make a crossbow and a catapult that shoots matchsticks and corks? How can you make good food look repulsive?

These are among the many questions Michael Underwood and Kate McIntyre (below) set out to answer in this new series of a well-established strand for children, where the fun and games are backed up by references to basic scientific principles. The crossbow and the catapult, for example, are all about releasing conserved energy at the right moment. You can then use the projectiles to knock down a medieval castle, constructed in Blue Peter style out of old toilet rolls and lolly sticks. Good old-fashioned fun.

Capitalism BBC4, from Friday, June 28, 9-10pm

Melvyn Bragg introduces a three-part study of capitalism, starting with the Industrial Revolution and the teachings of Karl Marx. He continues next week with the 20th-century conflict between capitalism and communism, and concludes the following Friday with a discussion about the future of capitalism and whether there are any conceivable alternatives.

Bragg is joined by a number of experts to discuss these topics.

Last night, also on BBC4, Mark Steel gave an idiosyncratic view of Karl Marx, his life and his legacy, in The Mark Steel Lecture. On July 8, the same channel is broadcasting The King of Capitalism: Thomas Watson Sr and the Building of IBM - the fascinating story behind the multinational corporation and the eccentric who founded it. All in all, that’s a lot of heavyweight political debate on BBC4 - capital!

The Manns BBC4, from Wednesday, July 3, 10-11pm

This Bavarian Media Television production, by Heinrich Breloer, looks at the history of novelist Thomas Mann’s family. Mann is the author of Buddenbrooks and Death in Venice, and won the Nobel Prize for Literature in 1929.

With the help of his daughter Elizabeth, the film traces his life and that of his brother Heinrich and son Klaus. Their stories are set against the background of the Weimar Republic, the Third Reich and the postwar period. It was during this time that, as leading anti-Nazis, they found themselves at odds with the mood of their time.

The series has been a great success in countries across Europe and, in effect, uses the Mann family as the focus for a history of Germany in the 20th century.

Great Battles Discovery Channel, from Tuesday, July 2, 8-8.30pm and 12.30-1am

The first of these four films deals with the Battle of Hastings, describing its impact on British history and the part technology played in the Norman victory.

Wednesday’s featured battle is Bosworth, which signalled the start of the Tudor dynasty and a period of great prosperity for the country. This is followed by Marston Moor (the defeat of Charles I) and the Battle of the Boyne - an event not forgotten in some corners of the UK.