He began as a juggler, someone who can keep several objects in the air at the same time.

VOA: special.2009.03.09

That is metallic sodium that would keep in kerosene so it doesn't react with the oxygen in the air.

金属钠应该保存在没有中,这样它就不会和空气中的氧气反应了。

麻省理工公开课 - 固态化学导论课程节选

Keep them up. Wave them in the air with a bit of motion.

先别放下手,再举一小会

耶鲁公开课 - 博弈论课程节选