Modern life makes us tired, right? But research from societies in Africa and South America suggests people in the ancient world slept only 6.5 hours a night.

马斯克的公然唱反调，也表明他与特朗普之间出现了罕见的分歧。要知道，马斯克一向是力挺特朗普的，他先是在竞选中为特朗普豪掷2.7亿美元，然后又在特朗普的新政府里扮演了重要角色。