Elon Musk has pivoted from his long-standing focus on Mars, announcing an ambitious plan to set up a “self-growing city” on the moon in less than a decade. The plan could see Musk’s aerospace company, SpaceX, competing for prime space with China’s planned International Lunar Research Station, which Beijing aims to establish by 2035. While it is possible both the US and China could have bases on the moon within a decade, a space expert said it would require massive infrastructure that neither...