That simple explanation is exactly wrong though! You don't expect to wait 2x the average. You expect to wait 1x the average, but you also expect that when you start waiting the previous block happened 1x the average time ago, and 1+1=2.
Consider buses which arrive every ten minutes, exactly. You arrive at the bus stop at a random time. How long should you expect to wait? Not 10 min but 5 min, on average. You are equally likely to arrive at any point during the 10 minutes wait.
Now change the buses to a Poisson process with mean rate 1 bus every 10 minutes. Now you arrive during an interval of average length 20 min, but wait on average 10 min.
https://news.ycombinator.com/item?id=16470358
> The hitchhiker's paradox is correct, taking a point and looking backward or forward will correctly give an average event 10 minutes away, but combining the events to give an average of 20 minutes is false.
https://news.ycombinator.com/item?id=16471544
> I thought this sounded funny, and I did a little simulation to see if it was correct. Given his assumptions (poisson with lambda 10), you do not get that answer. I got right around 10, which is what I would expect.