Conduction is thermal energy moving along physical objects. Conductors are materials that make it possible for thermal energy to flow. Insulators are materials that prevent thermal energy from flowing. Convection is when particles with high thermal energy move into areas with low thermal energy. This transfers the energy from one place to another. Radiation, or inferred radiation, is how thermal energy is moved through items. Radiation is the only one out of the three that can happen in space, because it does not involve particles. Thermal energy always scales with heat capacity.
The earth produces thermal energy from the heat it radiates; this energy is commonly referred to as geothermal energy. Many countries are turning to geothermal energy because it is cheaper and provides a substitute to fossil fuels, which are becoming harder to find. Geothermal energy can be found in a person's backyard, 10 to 100 feet down, and in hotspots like the Pacific Rim.
It is important to note that thermal energy is not the same thing as heat. Heat is the exchange between two systems, while thermal energy can exist and be measured in a single system.Learn more about Thermodynamics