Fusion power’s biggest question remains unanswered: how do you ensure the cost to start the fusion reaction isn’t higher than the price at which you can sell the power? Plenty of people have ideas, but no one has cracked it yet. Commonwealth Fusion Systems, for example, is confident enough that it’s building a massive reactor that costs several hundred million dollars. But the device won’t be turned on until next year , leaving the question unanswered for now. Other companies that were founded