When someone mines for bitcoin, what's the best cryptocurrency to buy what they’re really doing is adding and verifying a new transaction record to the blockchain—the decentralized bank ledger where bitcoin is traded and distributed. But bitcoin isn’t going anywhere. Its first-mover advantage has translated into a recent market cap of $700 billion, more than the five next most valuable cryptocurrencies combined. (Ether, the second most popular, has a market cap of $250 billion.) And bitcoin mining is unlikely to get much less energy-intensive. Its algorithm forces miners to compete to unlock each new coin, and that competition will continue until the last bitcoin is mined, sometime around 2140. Registering a transaction on the bitcoin blockchain takes a million times more energy than processing one on Visa’s bank network. (Backers say a new Lightning transaction network designed to operate atop bitcoin could make it even more efficient than Visa.)nbsp