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Nearly all of the known energy sources utilized by humans come from the Sun
or other stars. The stars themselves came from the accumulation of matter created
from intense densities of light resulting from the Big Bang, about 14 billion
years ago.
Humans and other living organisms, for all of our splendor and diversity, are
really energy scavengers living off of the carcasses and emanations of stellar
bodies. Though the truth may not be pleasant, it has important consequences!
First for some fun, though. Let's look at all of the wonderful ways we produce
and use power.
For perhaps ten thousand years, humans have utilized solar power to grow food. Humans cannot eat sunlight. However, plants such as corn, tomatos and beans depend upon sunlight for their energy, and humans can get energy to power their lives by eating those plants. Some plants such as mushrooms do not obtain energy directly from the Sun, but rather from other decaying solar-powered plants.
Most food that humans eat comes from agriculture. Food is grown on both big
farms and small ones, all across the Earth. Ultimately, farm fields can be seen
as giant solar collection systems, for it is sun light that powers the growth
of most food plants. However modern human agriculture is heavily dependent upon
petroleum for use as a fuel for tractors which plow and harvest fields and trucks
which transport most of the harvest. Humans also eat meat, but farm animals
such as chickens must eat food, most of which is grown on farms.
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