Free
Earth, Venus, and Mars are neighbors in the solar system. They’re also 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 was lost to space. This was partly because of solar wind. Earth’s magnetic field protects it from solar wind. Only Earth has the proper atmosphere and distance from our Sun to preserve water and sustain life.
Loading the player...
Sunblockers
Different layers of Earth’s atmosphere work as a screening system to block out the Sun’s harmful radiation. Most visible light and radio waves make it to Earth. But dangerous X-rays are stopped in the ionosphere. Meanwhile, the ozone layer of the stratosphere absorbs most—but not all—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 ejects charged particles that travel in solar wind at 1 million miles an hour. Some of them come zooming toward Earth. Others travel to different parts of space.
Earth’s magnetic field is surrounded by the magnetosphere. It protects Earth from most of the charged particles from the Sun.
Magnetic field lines are invisible lines of force between poles.
Earth is like a huge magnet. Its magnetic field extends far into space.
Some charged particles from the Sun enter Earth’s magnetosphere. They are channeled along the magnetic field lines toward the North and South Poles.
Solar wind distorts the shape of the magnetosphere.
On the Sun side of Earth, the magnetic field lines are squashed 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 known as the aurora borealis, or northern lights. In the Southern Hemisphere it’s called the aurora australis, or 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. For instance, the Sun makes water evaporate and become clouds. Those clouds help reflect about 34 percent of the Sun’s visible light back into space. The Sun helps warm the atmosphere, but the heating is uneven. That’s partly because the planet’s cloud cover is spotty. This uneven heating causes differences in air pressure. These generate wind and weather changes.
Sunlight hits our backyards and beaches as tiny bits of energy called photons. A photon travels at the speed of light (about 186,000 miles per second). It takes a photon about eight minutes to reach Earth. The atmosphere (the thin layer of gases that surround our planet) blocks out much of this sunlight. With no atmosphere, the sunny side of Earth would be 250 degrees F, while 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 own food, which is 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. For instance, 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 are also tied to the Sun. ▶
