Ideal Gas Law / Equation of State

The ideal gas law combines Boyle’s law, Charles’ law and uses volume as the inverse of density. All gases are found to approximately follow this equation.

─     Gases tend to expand when heated and become denser when cooled.

─     Density increase + constant temperature = pressure increase

─     Constant density + temperature increase = pressure increase

Deriving Poisson's Equation

In mathematics, Poisson's equation is a partial differential equation of elliptic type with broad utility in electrostatics, mechanical engineering and theoretical physics. It is used, for instance, to describe the potential energy field caused by a given charge or mass density distribution. The equation is named after the French mathematician, geometer, and physicist Siméon Denis Poisson. [Wikipedia]

Siméon Poisson

Focus on Aviation: Density Altitude and Aircraft Performance

Understanding Weather and Climate (7th Edition) (MasteringMeteorology Series) by Edward Aguado, James E. Burt 

Physical Principles: Variations in Density

Understanding Weather and Climate (7th Edition) (MasteringMeteorology Series) by Edward Aguado, James E. Burt

The World of Seven Billion

National Geographic - The World of 7 Billion

The map shows population density; the brightest points are the highest densities. Each country is colored according to its average annual gross national income per capita, using categories established by the World Bank (see key below). Some nations— like economic powerhouses China and India—have an especially wide range of incomes. But as the two most populous countries, both are lower middle class when income is averaged per capita.