When is a kilogram not a kilogram?
I feel that I should be surprised at the ambiguity of BBC journalists. Sadly, I'm not.
Writing about the change in the definition of a kilogram, Pallab Ghosh describes the imprecision of the current standard, Le Grand K:
How wrong is Le Grand K? The fluctuation is about 50 parts in a billion, less than the weight of a single eyelash.
Pallab Ghosh, science correspondent, BBC News
But parts per billion
is a relative measurement, so the analogy means nothing without additional context. It's the weight of a single eyelash in relation to what? Twenty million eyelashes is obvious—assuming he's using short scale—although meaningless.
After more than one reread, he's equating the fluctuation to the weight of a single eyelash compared to the kilogram standard itself. It could've been phrased clearer though, for those of us sitting at the back of the class. The fluctuation is less than the weight of a single eyelash
would've sufficed, and he didn't really need to bring in ppb at all.