9 More Minutes

So, I have a little poll for any who would like to participate. In makes it no fun if you google the answer. Just give it your best shot. The question is...Why do alarm clocks have a snooze button that extends sleep for 9 minutes? Why not 5? Why not 10? That is the question that I have researched. Here are some possible answers to that perplexing pregunta.

Theory 1
Ten minutes is long enough to get back into deep sleep, so they set the snooze for 9 so that people did not fall back into a deep sleep. This makes people happier throughout the day

Theory 2
Before digital clocks, when the snooze feature was added, the gears of the snooze function had to mesh with the gears of the clock. Because the gears did not fit precisely at 10 minutes, they set the snooze to be 9 minutes because more than 10 minutes would be too long. In other words, it was just a function of gears fitting together. Upon the advent of digital clocks, clockmakers had just accepted that snoozes should last 9 minutes

Theory 3
It is easier to program the alarm clock to pay attention to one digit. By setting the snooze to be 9 minutes, the programmers only have to worry about the last digit (they program the alarm to go off as soon as the last digit DECREASES by one i.e. 45 to 54). If it were 10 minutes, the last digit would be the same, thus requiring more digits for the alarm clock to keep track of

Theory 4
Original clockmakers were lazy and did not care about precision. When the snooze feature was introduced, it usually ended up going off between 9 and 10 minutes after the snooze button was hit. When digital clocks were invented, 9 minutes was then seen as the norm, hence the 9 minute snooze

Put your vote in for the theory you like the best. There seems to be no real consensus on this, so there are no wrong answers. Just something fun to ponder.