Eastern Europe. Thus, MacKinder articulated the famous encapsulation of his
argument:
Who rules East Europe commands the Heartland; who rules the Heartland
commands the World-Island; who rules the World-Island controls the world.The heartland theory unquestionably had a profound impact on geopolitical
thinking in the wake of World War I. Eastern Europe’s strategic importance as a
shatterbeltwas now reinforced by the heartland theory, and German scholars like
Karl Haushofer and other members of the Geopolitik school certainly considered
MacKinder’s theory to be a major contribution. Even MacKinder’s critics, most
notably Nicholas Spykman and hisRimland theory,employedasimilarcore-
peripherytheoretical framework in constructing alternatives to the heartland con-
cept. It is a testimony to the tenacity of MacKinder’s ideas that the heartland
theory remains the subject of debate among political geographers today.
Heating and Cooling
Change of temperature on hourly, daily, and seasonal time scales is familiar to all
of us. In one sense they are quite simple because they are largely driven bysolar
energy. As the sun changes its position in the sky during the day, disappears below
the horizon at night, or its path through the sky systematically changes over a
course of months, we can readily understand its importance to heating and cooling
here on the planetary surface. The full story is more complicated and vital to our
understanding of physical geography.
Heat is the energy of molecular motion that is exchanged between molecules.
All objects inEarth’sphysical systems contain some heat, including those at very
coldtemperatures. Heat transfers from warmer to colder substances at a rate pro-
portional to the temperature differences between the substances. The calorie is the
standard unit of heat and is the amount of energy needed to raise the temperature
of 1 gram of pure liquid water 1°C. (This is different than from Calories used in
dietetic applications where 1 Calorie¼1,000 calories.) The amount of heat that
can be transferred out of an object is related to its total heat content and its emis-
sive properties. The sun is large and is losing its heat content over billions of years.
The metal in an automobile may be hot to the touch when exposed to solar energy,
but rapidly loses its heat content at night and typically becomes much colder than
surrounding, natural materials. In a broad sense, heating and cooling can be under-
stood via energy imbalances. If an object gains more energy than it loses, its
Heating and Cooling 171