Karetot 12: Olive Bulks, Egg Bulks, Volume and Time Measurements

Today's day examines measurements regarding eating.  We have learned about this before, but not in the context of applying the punishment of karet.  There will be a certain amount of food that must be eaten to fulfil a commandment, for example, after reciting ha'motzi lechem min ha'aretz, for commanding us to eat bread from the earth, and for eating something forbidden, for example eating something on a fast day.  We look at the volume of the food and the amount of time we spend eating. Generally, eating is measured as consuming k'zayit b'cheday achilat peras, an olive bulk over the time it takes to eat a half loaf of bread.

Peres is based on the root 'p r s', to break, and so the word peras means a broken piece, agreed to mean half of a loaf.  But how large is the loaf?  Rashi says that the loaf is the size of eight eggs and thus the peras is the size of four egg-bulks. The Ramban says that the loaf is the size of six eggs and so the peras is the size of three egg bulks.  

The rabbis also argue about the volume of an egg bulk.  It might be 40 cubit centimetres or 100 cubit centimetres.  That would be one monster egg.

And of course, the rabbis disagree about the time that it should take to eat this amount.  Their arguments consider using the size of an average person or, alternatively, using a subjective standard for each individual.  The Gemara continues this discussion, debating the time it might take to walk half of a Roman mil, mile, which might be nine minutes.  However, in other places it might be the amount of time that it takes to walk 200 amot; approximately two minutes.  

The Halacha seems to vary between these two extremes.  This is another set of laws that demonstrate the plasticity of Torah law depending on time, place, experience, personality, bias, and interpretation.