I recall seeing a suggestion that "everything" happens in threes, in a meaningful sense. Something along the lines of: you take events which happen according to

I recall seeing a suggestion that "everything" happens in threes, in a meaningful sense. Something along the lines of: you take events which happen according to a poisson distribution with parameter L, and you define a cluster to be "any group of events which happen with no more than time L between adjacent ones", and then the expected size of a cluster is a little less than three. I'm probably misremembering the details, and I can't immediately find a source, but I thought this was interesting.