You've probably heard the claim that if all of your blood vessels were set in a line they would reach 60,000 miles/100,000km (or twice around the world). It's

You've probably heard the claim that if all of your blood vessels were set in a line they would reach 60,000 miles/100,000km (or twice around the world). It's so ubiquitous you can find that trivia in numerous places, from blogs and articles to books, webpages of educational institutions and scientific papers. But where did it come from ? And is it true ? This video is about Kurzgesagt and their year-long journey to find the original-original source.