Yep! It does seem a little funny to trust olive oil, but since there's a very specific refractive index standard that extra virgin olive oil needs to meet, it makes a convenient and inexpensive calibration fluid. There are lots of other options (glycerol, etc.) that could be used, but most people already have olive oil in their kitchen and few people have lab grade supplies lying around.Why do we have to put our trust in olive oil?
Isn't it ludicrous?