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The Sun pumps out energy in all directions 24/7,

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and Earth soaks in it every day.

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Some of that energy gets absorbed--

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by the oceans, the land, the atmosphere--

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and some gets reflected back out into space.

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How much stays and how much goes is a function of Earth's Energy Budget.

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Almost all of Earth's energy comes from the Sun.

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As sunlight heats the planet, the planet changes.

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The most obvious transformations are with water.

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Oceans soak up heat, warming the planet.

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But warming water evaporates, which forms clouds.

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Those clouds, in turn, reflect sunlight back into space, which cools the planet.

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When the clouds dissipate, sunlight once again warms the water below....

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...and the cycle continues.

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Other areas of the world have similar cycles.

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Polar ice caps, for example, reflect sunlight....

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...while dark land surfaces soak it up.

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Overall, the amount of energy leaving the planet is equal to the amount coming in,

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and Earth's energy budget stays roughly in balance....

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...and it's a delicate balance.

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That's why NASA has missions designed to keep track of how much energy The Sun is putting out,

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as well as missions designed to keep track of forces on Earth

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that might alter how much heat the planet traps.

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That energy balance isn't simply a scientific measurement,

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but a description of one of the most fundamental conditions

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for making our planet conducive for sustaining life.