The Sun pumps out energy in all directions 24/7,
and Earth soaks in it every day.
Some of that energy gets absorbed--
by the oceans, the land, the atmosphere--
and some gets reflected back out into space.
How much stays and how much goes is a function of Earth's Energy Budget.
Almost all of Earth's energy comes from the Sun.
As sunlight heats the planet, the planet changes.
The most obvious transformations are with water.
Oceans soak up heat, warming the planet.
But warming water evaporates, which forms clouds.
Those clouds, in turn, reflect sunlight back into space, which cools the planet.
When the clouds dissipate, sunlight once again warms the water below....
...and the cycle continues.
Other areas of the world have similar cycles.
Polar ice caps, for example, reflect sunlight....
...while dark land surfaces soak it up.
Overall, the amount of energy leaving the planet is equal to the amount coming in,
and Earth's energy budget stays roughly in balance....
...and it's a delicate balance.
That's why NASA has missions designed to keep track of how much energy The Sun is putting out,
as well as missions designed to keep track of forces on Earth
that might alter how much heat the planet traps.
That energy balance isn't simply a scientific measurement,
but a description of one of the most fundamental conditions
for making our planet conducive for sustaining life.