If this question had a simple answer, such as a formula that could be learned, you can be sure that every comedian would know it! But laughter is a complicated things, and the best explanations of it are still only theories. We know, of course, that laughter is an expression of many feelings and that laughter is only found among human beings. It is difficult to decide what really makes...

Early man had to rely on his own muscle-power to carry objects, but over thousands of years tamed animals, such as horses, oxen and donkeys, elephants and camels. In order to be able to transport more goods than an animal could carry on its back, sledges and hurdles that could be pulled behind the animal were eventually invented, as well as such instruments as ploughs to make agriculture...

There are more than 150 species of octopus, ranging from the very small to the giant octopus, which may reach 33ft (10m) in length. Most of them eat crabs, fish, crustaceans and smaller mollusks, which they catch and tear apart with their suckered tentacles. An octopus’ mouth is shaped like a parrot’s beak, with two very strong jaws. In addition the octopus can inject venom or poison...