[chengmi]

I wouldn't be surprised if the "pi" trend correlates well with vacation times in academia.

[aristus]

Sure, but are school curricula really that well coordinated across the english-speaking world? I'm kind of surprised that the graphs match so well:

http://www.google.com/trends?q=natural+logarithm%2Cbase+10%2...

http://www.google.com/trends?q=hamlet%2Csocrates%2Ctruman

[chengmi]

We may be reading too much into this: http://www.google.com/trends?q=base+10%2Cdirac%2Ccheerios&#3...

[pygy]

Yes, but : http://www.google.com/trends?q=base+10,dirac,+wrist+band&...

This is a US specific plot, but the world wide one is similar. There are plausible explainations for a correlation between the type of breakfast and the school cycle.

The spike at the end of 2007 appears for any queries when you look at the world-wide data.