(The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.) Daniel Merino, The Conversation (THE CONVERSATION) The 2023 Tour de France is here. Starting in Copenhagen on June 1, the tour covers almost 2,100 miles (3,380 kilometers) over 24 days of riding through Denmark, Belgium, Switzerland and France. The tour is a feat of human athleticism, but to really understand how incredible it is to complete the race – much less win it – requires thinking about a unique blend of physics, biology and physiology.