Buckingham Pi Dimensional Analysis - simplifying problems by eliminating units

**Alternate title: "How to make Pi"
A tutorial on the Buckingham Pi method, why dimensionless parameters are awesome (not just the Reynolds number), and how they can be used to narrow down the solution space before even a single experiment is performed.

Submitted to #SoME3
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References and images

https://commons.wikimedia.org/w/index...
http://www.jpl.nasa.gov/pictures/sola..., https://commons.wikimedia.org/w/index...
https://www.nasa.gov/centers/ames/org..., https://commons.wikimedia.org/w/index...
https://www.nasa.gov/centers/ames/ima...

Egdar Buckingham, https://commons.wikimedia.org/w/index...
Lord Rayleigh, https://commons.wikimedia.org/w/index...
Joseph Bertrand, http://scienceworld.wolfram.com/biogr..., https://commons.wikimedia.org/w/index...

Vortex street animation by Cesareo de La Rosa Siqueira - http://www.mcef.ep.usp.br/staff/jmene..., Attribution, https://commons.wikimedia.org/w/index...

Pierre-Gilles de Gennes during a lecture in 2006. CC BY-SA 3.0, https://commons.wikimedia.org/w/index...

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