Cryptocurrency mining uses huge amounts of power—and can be as destructive as the real thing.

Money, it’s often said, is a shared fiction. I give you a slip of paper or, more likely these days, a piece of plastic. You hand me eggs or butter or a White Chocolate Mocha Frappuccino, and we both walk away satisfied. With cryptocurrency, the arrangement is more like a shared metafiction, and the instability of the genre is, presumably, part of the thrill. Dogecoin, a cryptocurrency that was created as a spoof, has risen in value by eight thousand per cent since January, owing to a combination of GameStop-stylepumping and boosterish tweets from Elon Musk. On Tuesday, which backers proclaimed DogeDay, the cryptocurrency was valued at more than fifty billion dollars, which is more than the market cap of Ford. Coinbase, a cryptocurrency exchange, went public last Wednesday; almost immediately, it became worth more than G.M.