No, not a million of those... I am talking about page hits. And no, there is no reason for retiring: the next million is awaiting!

I didn't give much thought to page hits when I started blogging. And I probably still don't give it enough attention, but I do realize it is page hits that make the internet tick. And yes, it is stimulating for me to witness a piece that I have written attracting many thousands or even tens of thousands of hits. Yet somehow it feels unreal. Who are all these folks clicking on a link to this blog? A million hits for a nerdy and rather inaccessible physics blog is way more than I ever could have expected. 

Or is it? Let's put this figure of one million in perspective. If this blog continues attracting page hits at its current rate, it would take a respectable ten centuries to get to the number of hits of a video of two toddlers uploaded onto YouTube. And that is a video that got created in a minute and happened to be uploaded for the mere purpose of allowing it to be watched by the toddlers' godfather. And that figure of ten centuries probably creates a too rosy comparison for the blog you are reading: it seems safe to assume that a significant fraction of the 400 million hits of the toddlers video resulted in a full 56 seconds view with all the nuances ("That baby knows perfectly well what it's doing!") getting conveyed. Can the same be said of the million hits of my blog? I doubt it. 

Well, in fact, I don't doubt it: I am pretty sure that the number of hits to the posts on this physics blog tells me very little about how often the various articles have been read and digested. I would be surprised if the number of true readers isn't at least an order of magnitude smaller than the number of bare hits.

Let's have a look at the available statistics.

I started this blog May 2009, 32 months ago. A total of 65 articles were posted, a modest two per month.* These attracted a million hits, and 2,350 comments. It seems reasonable to assume that the number of reads is in-between the number of hits and the number of comments. Lacking a better method, and to settle on a number, I am going to apply the 'Hammock Rule'. This rule can be applied to blogs every reader can comment on: the number of people actually reading a blog post is the geometric mean of the number of hits and the number of comments posted by the readers:

   #Reads  =  Sqrt( #Hits  X  #Comments )

This rule is based on the assumption that reading the full blog post given one has stumbled upon it, provides as much a hurdle as reacting to a blog post given that one has read it. This assumption translates into the expectation that if one in every N people who happen to hit upon a blog post do make the effort to read it, also one in every N people who happen to  read it do post a reaction. The rest is simple math. 

With #Hits = 1,000,000 and #Comments = 2,350, it follows that my blog posts have been read in total roughly 48,500 times. A number that translates into an order of magnitude estimate of close to 750 faithful readers that pay careful attention to each Hammock Physicist blog post. That doesn't seem an unreasonable figure, given the fact that my least popular posts have delivered a number slightly north of 1,000. With close to 750 recurring readers, and taking into account duplicate hits, one would indeed expect a thousand or more hits also for the least popular posts. So let's settle on a number of 750 loyal followers who pay attention to each of the posts on this physics blog.

As many as 750 loyal readers, that is a number that I am more happy with than the million hits. Thank you, all seven-hundred-fifty of you!

Now back to the hard data. On average each hammock post attracted slightly more than 15,000 hits. The variation around this average is huge, with the most popular articles attracting over 100,000 hits. This strong variation must contain some important insights on what info the pop-science-hungry are seeking. The twelve most popular Hammock Physicist articles each attracted over 25,000 hits:

 1) What's Wrong With E=mc2?
 2) It From Bit - The Case Of Gravity
 3) Survival Of The Stupidest
 4) Holographic Hot Horizons
 5) It From Bit - Entropic Gravity For Pedestrians
 6) Shut Down The LHC?
 7) The Art Of Acting Rational
 8) Limits To Science: God, Godel, Gravity
 9) Big Bang, Big Bewilderment
10) Metric Versus Imperial
11) It From Bit - Dark Energy
12) Gravity Of Free Will

Can you spot a pattern? I can't. I have no idea why precisely these articles come out on top. What do energy-mass equivalence, entropic gravity, game theory, the LHC, and units&measures have in common? If you see a commonality between these twelve posts, let me know!

One last piece of interesting statistics. It is well known that rankings such as the population ranks of cities, corporations size rankings, income rankings, citation rankings, meteorite size rankings, earthquake amplitude rankings, etcetera, all tend to follow Zipf's law. This rank-size rule states that the top ranking item will approximately be twice as large as the second largest, three times as large as the third largest, etc. Does the same regularity hold for Hammock Physicist page hit rankings? 

Not entirely surprising, the ranking of my blog posts by hit frequency indeed does display a Zipfian behavior. This can best be seen by plotting the number of hits for each of the blog posts versus their page hit rank in a log-log plot. If Zipf's law holds the result will be a line with slope -1. Such a behavior is indeed observed for the "Hammock Physicist" page hit statistics (see figure, the purple straight line indicates Zipfian behavior with slope -1). 

Why is this Zipfian behavior so ubiquitous? Why does it describe phenomena as diverse as your blog surfing behavior as well as city sizes and meteorite impacts? 

That question deserves its own blog post...

* Yes Hank, I know: attention span on the Internet is short, and to build a significant group of followers, I need to make that into posting at least twice a week, or even better: twice a day. If only I could find the time...