🚀 go-pugleaf

lhom@nature.berkeley.edu (Louis Hom) writes:
>
>So, I'm trying to collect posters' favorite Things in Math & Science.

 My favorite bit of elementary math is the relationship between the 
 trig functions and exp(ix).  The special case of e^{i\pi} gets all 
 the fame and fortune, but students are much more intrigued by the 
 more general result when they first find out how to use it to 
 solve differential equations easily. 
 
 My favorite physics factoid is the volume I call the "Hubble-barn". 
 This has a cross-sectional area of 1 barn (used to quantify reaction 
 rates in nuclear and particle physics, SI value = 100 fm^2) and a 
 length of the inverse hubble constant (c/H; with H = 75 km/s/Mpc 
 this is  about 120 Ym).  The volume is about 12 liters for that 
 value of H, which is around the middle of the range spanned by 
 various controversial measurements, IIRC.  For that value, a straw 
 with the cross-sectional area of the Ba-135 nucleus that extends 
 to the edge of the universe has the volume of about pi US gallons, 
 the universere in about 10 six packs of beer.  This provides an 
 interesting way to compare different values of Hubbles constant, 
 since 55 ==> about 17 liters, while 100 ==> about 9 liters. 

 The more obscure "barn-Megaparsec" = 3 cm^3 = about 2/3 teaspoon 
 but has the advantage of being a well-defined constant.  

-- 
 James A. Carr   <jac@scri.fsu.edu>     |  "They invented band!"  
    http://www.scri.fsu.edu/~jac/       |  Spectator at 1997 inaugural parade
 Supercomputer Computations Res. Inst.  |  commenting on the Macarena done by
 Florida State, Tallahassee FL 32306    |  the Florida A&M Marching 100