Final answer:
Most of our energy originates from the sun, captured by plants through photosynthesis, with a significant portion from the combustion of fossil fuels releasing stored solar energy. The energy fuels our bodies and our technology, though it ultimately converts into heat.
Step-by-step explanation:
The energy we use to function primarily comes from the sun. Through photosynthesis, plants and certain bacteria convert solar energy into chemical energy, which is then passed on to us either directly through the consumption of plant materials or indirectly via the animals that feed on plants.
Moreover, the combustion of fossil fuels, such as oil, coal, and natural gas, also releases solar energy that has been stored over millions of years as plant and animal matter.
Humans then use this energy in various forms for transportation, electricity, heating, and other needs. However, most of our energy consumption involves thermal processes and eventually turns into heat, except for a small fraction used in activities like launching objects into space.