Sunlight for Food & Warmth

All life on Earth depends on sunlight for its existence, either directly or indirectly. Without sunlight (in its broadest sense, including all forms of radiation from the Sun), life as we know it would not exist; it would not have the conditions necessary for survival, and probably wouldn’t have developed in the first place.

Although not all of this energy reaches the Earth’s surface, much of that which doesn’t is absorbed by the atmosphere. Most of this energy ends up heating the Earth, reinforced by the greenhouse effect of the atmosphere, and results in an environment suitable for sustaining life.

Besides this environmental heating effect, many forms of life depend on the Sun in other ways: plants, algae and some bacteria rely on the Sun to drive the process of photosynthesis, that uses the Sun’s energy to power chemical reactions that provide food for the plant and allow it to grow; reptiles rely on the direct heating effect of the Sun’s rays to maintain their body temperature and allow them to be active.

Even those organisms that don’t rely directly on the Sun for food either directly eat other organisms that do, or eat other organisms in a food chain that ultimately ends up at such organisms, and so still indirectly rely on the Sun for their food. This includes us as human beings: the majority of the food that we eat is either plants or animals that eat plants.

We also depend on the Sun for energy in another way – through our use of fossil fuels: coal, oil and natural gas. These are nothing more than ancient plant and animal material, produced more or less directly from sunlight and then stored in the Earth for millions of years. In consuming these fuels, we are releasing stored energy from the ancient Sun. Modern biofuels are essentially the same process, but without the intermediate storage.

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