11.Boltzmann's Constant: 1.380650 x 10^23 joule per kelvin

The Boltzmann constant occurs in nearly every statistical formulation in classical and quantum physics. 

Boltzman constant explains why ice cubes melt in warm water, but are not spontaneously created in tepid water, among other uses.

10. Imaginary Unit: i

"i" equals the square root of -1, which means that i squared is equal to -1.

Math had advanced to the point where saying "there is no square root of negative numbers" was holding back a lot of progress. Solutions of some polynomials have both real solutions that we could use in real life as well as solutions that involved the square root of a negative number, which can be discarded.

9. The Golden Ratio: 1.6180

The golden ratio is a number which we often use while taking the ratios of distances in geometric figures.

It is used in financial technical analysis to determine when a market will continue its path or reverse. It's also observed very frequently in nature, especially in the way that some naturally occurring spirals expand outward.