When Accepted Knowledge Isn't Knowledge at All

There are some factoids and trivia on the internet that have been around so long they are accepted as common knowledge. But that doesn't necessarily mean they are true. If something is repeated enough times, people will believe it, at least until someone calls their bluff. In this example, we've all heard that the blood vessels in your body, if laid out end-to-end, would be 100,000 kilometers or 60,000 miles long, which is long enough to wrap around the earth twice and then some. But where did that figure come from in the first place? Who figured this measurement out? And is it true? Kurzgesagt decided it would be best to run this down after someone asked for a source. It was a long path back to 1922 to find where this fact came from, and a big job figuring out if it was plausible. The moral of the story is that fact-checking can be a lot harder than you'd think. This video is only 10:35 long; the rest is promotional.