Bitcoin and other so-called cryptocurrencies （加密货币）have been all over the news lately. Apparently, the idea of money that's not tied to a specific bank—or a specific country—is appealing to many. But it's worth remembering that the banking system that we now all live with is just that： A modern invention. Not so long ago, money was almost always created and used locally, and bartering was common. （In fact, it still is common among many online local networks, like the Buy Nothing Project.）.In the past, money's makeup varied from place to place, depending on what was consid