I also got stuck on that sentence for a minute. The idea of being able to throw a gram of salt in the ocean in Florida, wait a while for the salt to disperse, a

I also got stuck on that sentence for a minute. The idea of being able to throw a gram of salt in the ocean in Florida, wait a while for the salt to disperse, and then measure the difference in a water sample taken in New York sounded implausible. Also, when you talk about sensitivity, don’t you need to talk about the amount per something? E.g a billionth of a gram per milliliter?