**The talk will take place in RIII seminar room on 28th of=
September** at 19:00.

The structure of the talk will be as follows:

- Interlude to Dimensional Analysis, Quantities and the Principle of Dime= nsional Homogeniety
- Physical dimensions as a vector space
- Bridgmann's theorem
- Examples, and some interesting applications
- Dimensionless quantities as a group, the Buckingham PI theorem and the = principle of dynamical similarity
- Deriving Kepler's third law with Dimensional Analysis

Dimensional analysis is one of the finest tools in the tool-set of a phy= sicist. The idea of dimensional analysis is very simple: In physics, we're = not dealing with numbers alone. We're dealing with quantities equipped with= a physical dimension. The main way to play physics is as a game of restric= tion, and dimensional analysis is one of the tools for the job. At its simp= lest, dimensional analysis tells you that you can't have a physical law tha= t relates a left hand side of position to a right hand side of time; that's= the principle of time. In the depths of theoretical physics, it restricts = the form of your Lagrangians, objects that determine all, to a very large d= egree. In fluid mechanics, particularly computational fluid dynamics, it pl= ays a major role in determining analytical laws of very complicated systems= . Even when your problem is not physics, sometimes you can manually inject = dimensions as sensible to then farther figure out things about the problem = with dimensional analysis.

In ~1950 or so, the US did some nuclear bomb test (Trinity test) on some= desert in Mexico. While the details about the bomb were highly classified = at that time, some magazine published time-stamped photos of the explosion = to show off how big it is. Detective G.I. Taylor, a physicist and a fluid d= ynamist, only by looking at the photos, and mostly using dimensional analys= is, was able to come up with a pretty good estimate of the yield of the bom= b right off the bat~ 22 kilto tons of TNT was his result.

The accepted - but then classified - value was 20 kiltons. "classified"?= bleh :P

**Dimensional snacks** will be provided. Until then!