Dan Snow:When the war ended, life in the trenches was captured again and again in poems, novels, art and later films, all of which powerfully put across the horrible conditions soldiers experienced.

Trenches were long, narrow ditches dug into the ground. They were very muddy. Some soldiers developed a problem called trench foot. In the middle was no man's land. Soldiers crossed this to attack ...

Despite its isolation, the Mariana Trench is tainted by pollution, with microplastics found even in its remote depths, ...