My understanding is that the number 18 is the amount of time it takes for an average person to walk 1 mil (side Q, how does this measurement translate to current English or metric units?)

Why was this measurement used, though?

  • Not all communities light Shabbat candles 18 minutes before sunset. – Double AA Dec 17 '15 at 18:19
  • Many authorities believe it takes the average person 21.5 minutes to walk 1 mil. – Double AA Dec 17 '15 at 18:20