字幕表 動画を再生する 英語字幕をプリント This is the Roe River. And if you believe the hype, it is the shortest river in the world. And through the miracle of modern technology, the waterproof camera on this stick, I can show you the full length of it. All the way from the source, a crystal-clear spring in Giant Springs State Park, Montana, flowing down 61 metres until it joins the much, much, much larger Missouri River flowing to the ocean. Yeah, the river's just there. And it really is crystal clear: while I was setting up, someone came along with some bottles and filled them up for drinking water. I was off in Vidcon in Los Angeles last week as I record this, and I was having dinner with a few folks who make educational videos when I mentioned that I was coming here to talk about 'the shortest river'. And if I'm honest, the conversation didn't go well. They kept raising different objections, and seemed to get angry just at the concept. So eventually I looked up the dictionary definition of 'river' in the Oxford English Dictionary: "A large natural stream of water flowing in a channel "to the sea, a lake, or another, usually larger, stream of the same kind." First objection: this is man-made. True, the course of this was refined by people, but... ...so was the Los Angeles River and that's still a river despite a lot of people thinking it's just an overgrown storm drain. Although to be fair, the Roe River here didn't even have a name until the 80s when some students surveyed it and campaigned for it to be named the shortest river. The Guinness Book of Records did eventually agree, at least for a while. Okay, said the folks I was talking to, but how do you know it's the shortest? That is a fair point. There have been long-documented arguments about whether this river is even the shortest in the United States... ...and there are international claims too, like this short channel between two lakes near Jyväskylä in Finland. And I was really skeptical before I got here, but yeah, now I'm standing by it, I genuinely think this is the shortest river in the world. It is a large, natural channel flowing in one direction to a lake. Fits all the dictionary definitions, unless you want to argue that it's not large enough, but frankly if it's large enough to drown in, I think it should count. You could try adding more specifics. Forget arguing about whether this is natural: how about saying that a river starts at a source, flows somewhere in a consistent direction, and ends at a much bigger bit of water? That seemed like a great definition to me, until someone pointed out that that would include waterslides. Every time we tried to nail down a definition, it slipped away. I'll be honest, I'm not really here to show you The World's Shortest River, because I can't. Because there will always be quibbles about definitions. All the categories that we try to put the natural world into, to fit everything into maps and databases, all those categories have to be fuzzy. Mapmakers have known for years that, as with so many things in the real world, "is it a river" is not always a question that can be answered with a binary 'yes' or 'no'. There is almost always an exception to the rule. The 'river' is whatever humans agree it is. The exact definition probably differs between languages and cultures anyway. And in the end, the Guinness Book of Records decided not to have a listing for shortest river.