The lower stages of its Falcon 9 rockets crashed and burned many times before the firm mastered the art of landing and re-using them, something that had not been done before.

在该公司掌握了着陆和重复使用它们的技术之前， 猎鹰 9 号火箭的下级曾多次坠毁和燃烧，这是以前从未做过的事情。

For the next half hour or so, as you relax more and more, you will drift down through stage 2 and stage 3 sleep. The lower your stage of sleep the slower your brain waves will be.

在随后约半小时内，你进一步放松，进入第二和第三阶段睡眠。睡眠越深入，脑电波就越缓慢。