The rate of solar energy striking Earth averages 168 watts per square meter. The rate of energy radiated from Earth's surface averages 390 watts per square meter. Comparing these numbers, one might expect that the planet would cool quickly, yet it does not. Why not?

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Understand that the energy balance of Earth involves both incoming solar energy and outgoing terrestrial energy.

Recognize that the incoming solar energy is absorbed by Earth's surface and atmosphere, which then re-radiates energy back into space.

Consider the role of Earth's atmosphere, which contains greenhouse gases that trap some of the outgoing energy, preventing it from escaping into space immediately.

Acknowledge that this trapped energy is re-radiated back towards Earth's surface, maintaining a balance and keeping the planet warm.

Realize that this process is known as the greenhouse effect, which is why Earth does not cool quickly despite the difference in energy rates.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Energy Balance

Energy balance refers to the equilibrium between the energy received from the sun and the energy radiated back into space. The Earth absorbs solar energy and, through various processes, re-emits energy as infrared radiation. If the incoming energy exceeds the outgoing energy, the planet warms; if the outgoing energy exceeds the incoming energy, it cools. Understanding this balance is crucial to grasp why Earth maintains a relatively stable temperature despite the apparent discrepancy in energy rates.

Greenhouse Effect

The greenhouse effect is a natural process where certain gases in Earth's atmosphere trap heat, preventing it from escaping into space. This effect is primarily due to water vapor, carbon dioxide, and methane, which absorb and re-radiate infrared radiation emitted by the Earth's surface. This process helps to maintain a stable and habitable climate, counteracting the cooling that would occur if all emitted energy were lost to space.

Heat Capacity

Heat capacity is the amount of heat energy required to change the temperature of a substance. Earth's surface and atmosphere have significant heat capacities, meaning they can absorb and store heat without a rapid increase in temperature. This property allows the planet to moderate temperature changes over time, contributing to a stable climate despite fluctuations in energy input and output.

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The solar power striking Earth every day averages 168 watts per square meter. The highest ever recorded electrical power usage in New York City was 13,200 MW. A record established in July of 2013. Considering that present technology for solar energy conversion is about 10% efficient, from how many square meters of land must sunlight be collected in order to provide this peak power? (For compar- ison, the total area of New York City is 830 km2.)

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Write balanced chemical equations for each of the following reactions: (a) The nitric oxide molecule undergoes photodissociation in the upper atmosphere. (b) The nitric oxide molecule undergoes photoionization in the upper atmosphere. (c) Nitric oxide undergoes oxidation by ozone in the stratosphere.

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Write balanced chemical equations for each of the following reactions: (d) Nitrogen dioxide dissolves in water to form nitric acid and nitric oxide.