Cryptocurrency mining is basically verification that transactions on the blockchain are legitimate. One method to do that is “proof of work.” But that takes a lot of electricity. So soon, blockchain platform ethereum will shift to a different method: “proof of stake.” Instead of multiple miners expending energy at the same time, one “validator” wins a lottery to verify the transaction. “Marketplace’s” Kimberly Adams speaks with Alex de Vries, founder of Digiconomist, about what the shift means.