right now at 12p UTC there's a different set of top stories.
I call these Euro top stories. Within the next 2-4 hours USA will wake up and the top stories will change.
This would be really interesting to study. Same with Reddit.
Having moved continents last year, I think this is very apparent. European morning stores are the day/evenings of the US, and then like you say, between 2 and 4pm the active stories are more highly variable, as the US wakes up.
I believe HN will show you a few not-yet-popular posts that it thinks you might be interested in, so that the browsers of "New" aren't the only ones who decide what gets popular.
You might need to seek a psychics help to figure this one out.
xD
It's got 39 points in under an hour. That's clearly enough to push it up the rankings.
What are you confused by?
It had first only 4 votes and it was already in the top submissions.
All top submissions once had 4 votes – it all depends on how fast (and maybe from whom) they came.