Until about a century ago, social movement was relatively modest, and most people probably grew up within a day's journey of where they had been born. Communities were small (in fact, typically about 150 to 200 people), and most folks knew everyone. That arrangement created a complex web of interwoven relationships, many of which were familial. Since then, society has undergone a dramatic change. It has become commonplace for people to move many times during their working lives—first to college, then to their first jobs, followed by a series of moves as they are transferred to new offices by their companies or move to new jobs elsewhere. The result is that our networks of 150 have become fragmented into small subsets of friends picked up along the way. Our college friends probably do not know our family, and they certainly won't know the friends we acquired when we moved to another city for a job.Full article in IEEE spectrum: http://spectrum.ieee.org/telecom/internet/how-many-friends-can-you-really-have

## Thursday, June 2, 2011

### Maximum number of friends that humans can manage

Given through an explanation by Dunbar:

## Wednesday, June 1, 2011

### Difference between Kullback–Leibler (KL) and Kolmogorov-Smirnov (KS) distance

A nice excerpt from a site named stack exchange:

The KL-divergence is typically used in information-theoretic settings, or even Bayesian settings, to measure the information change between distributions before and after applying some inference, for example. It's not a distance in the typical (metric) sense, because of lack of symmetry and triangle inequality, and so it's used in places where the directionality is meaningful.

The KS-distance is typically used in the context of a non-parametric test. In fact, I've rarely seen it used as a generic "distance between distributions", where theℓ1 distance, the Jensen-Shannon distance, and other distances are more common.

## Sunday, May 29, 2011

### Application of the drake equation for finding a date

Application of the drake equation. This was also discussed in the big bang theory, where Howard walowitz uses this equation to calculate the number of females available for dating in a 40mile radius in Pasadena, CA.

"A man studying in London has taken a mathematical equation that predicts the possibility of alien life in the universe to explain why he can't find a girlfriend. Peter Backus, a native of Seattle and PhD candidate and Teaching Fellow in the Department of Economics at the University of Warwick, near London, in his paper, 'Why I don't have a girlfriend: An application of the Drake Equation to love in the UK,' used math to estimate the number of potential girlfriends in the UK. In describing the paper on the university Web site he wrote 'the results are not encouraging. The probability of finding love in the UK is only about 100 times better than the probability of finding intelligent life in our galaxy.'"

Labels:
application,
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drake equation,
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physics