Earth, Venus, and Mars are neighbors in the solar system. They’re all about the same size.
Billions of years ago, Venus and Mars may have had rivers, lakes, and even oceans. What happened? Water on Venus and Mars went into space, partly because of solar wind. Earth’s magnetic field protects it from solar wind. Only Earth has the right atmosphere and distance from our Sun to keep its water. This allows life to exist.
Sunblockers
Different layers of Earth’s atmosphere block the Sun’s harmful radiation. Most visible light and radio waves make it to Earth. But dangerous X-rays are stopped in the ionosphere. The ozone layer of the stratosphere catches most of the Sun’s ultraviolet rays. Water vapor in the troposphere blocks infrared light.
Sun Facts
Distance from Earth
Average of 93 million miles


Solar Attraction

The Sun throws off charged particles. These travel in solar wind at 1 million miles an hour. Some of them zoom toward Earth. Others go to different parts of space.
The magnetic field is surrounded by the magnetosphere. It protects Earth from most of the Sun’s charged particles.
Magnetic field lines are invisible. They’re lines of force between poles.
Earth is like a big magnet. Its magnetic field reaches far into space.
Some charged particles from the Sun enter Earth’s magnetosphere. The magnetic field lines send them toward the North and South Poles.
Solar wind changes the shape of the magnetosphere.
On the Sun side of Earth, the magnetic field lines are crushed by pressure from solar wind.
In the ionosphere, charged particles collide violently with gas atoms. This causes the atoms to give off light that is visible around the poles. In the Northern Hemisphere, this light is called the aurora borealis. The popular name is the northern lights. In the Southern Hemisphere, the light is known as the aurora australis. We call these the southern lights.
On the side of Earth away from the Sun, the magnetic field lines are stretched out.

▲ Mix sunlight and water and you get weather. The Sun causes water to evaporate. Then it becomes clouds. They help reflect about 34 percent of the Sun’s visible light back into Space. The Sun also helps warm the atmosphere. But the heating is uneven. That’s partly because Earth’s cloud cover is spotty. This uneven heating causes differences in air pressure. That creates wind and changes in the weather.
Sunlight hits our backyards and beaches as tiny bits of energy called photons. A photon travels at the speed of light. That’s about 186,000 miles per second! It takes a photon about eight minutes to reach Earth. The atmosphere (the gas layer that surrounds Earth) blocks a lot of this sunlight. Without atmosphere, the sunny side of Earth would be 250 degrees F. The dark side would be minus 250 degrees! ▼


◀ We capture some of the Sun’s energy every time we eat. Plants use sunbeams to make their food. It’s stored in their leaves. This process is called photosynthesis. It’s the key to life on Earth. Animals like cows and deer get energy from the plants they eat. These plant-eaters then become food for humans and other animals.
Most of the energy that powers machines comes from the Sun. Oil and coal are the fossilized remains of ancient plants and animals. Burning them releases the solar energy that those creatures stored up millions of years ago. Wind, water, and other ways of generating power also rely on the Sun. ▶
