The movement of heat in the

atmosphere causestemperatures to

change,winds to blow,and rain to fall.

Nearly all the energy in Earth’s

atmosphere comes from the

sun.

The sun’s energy travels

in electromagnetic waves, mostly as visible light and infrared

radiation.

A small amount of the sun’s energy

travels asultraviolet radiation.

Visible light includes all of the colors that

you see in a rainbow.

Different wavelengths result in the

different colors that you see.

Red and orange light have the

longest wavelengths.

Blue and violet light have the

shortest wavelengths.

Infrared radiation has

longer wavelengths

than red light.

Infrared radiation is

invisible, but it can be felt as

heat.

Ultraviolet radiation has

shorter wavelengths

than violet light.

Too much ultraviolet

radiation can cause sunburn,

skin cancer,and eye damage.

Before reaching Earth’s surface, sunlight must pass through

the atmosphere.

Some sunlight is absorbed or

reflected by the atmosphere before it can

reach the surface.

The rest passes through the

atmosphere to the surface.

Some of the sun’s energy

reaches Earth’s surface and is reflected back

into the atmosphere.

About half of the sun’s energy,

however, is absorbed by the land and water and changed to

heat.

When Earth’s surface is heated, it

radiates most of the energy back

into the atmosphere as

infrared radiation.

Much of this infrared

radiation cannot travel all the

way through the atmosphere

back into space.

Instead, it is absorbed and

forms a “blanket”

around Earth that holds heat

in the atmosphere.

This process is known as the greenhouse

effect and keeps Earth’s

atmosphere at a temperature that

is comfortable for most living

things.