The Sun gives us heat, light, our food, and the air that we breathe. It powers the atmosphere to give us the winds and rain. Even the coal and oil thatgenerate electricity for light and power come from plants and animals that lived hundreds of millions of years ago and depended on the Sun for life. The Sun heats theland, oceans, and air. It evaporates water from lakes and oceans. When the water vapor cools, it drops as rain or snow, giving us the moisture we need for drinkingwater and for plants and animals to grow. Water, Air, Life, and Land - the Earth is a system.
For most of us, Earth's environment ends somewhere above the clouds butbelow the space shuttle. The 93 million miles (150 million kilometers) of space between the Earth we know and the star we see is empty black space, a vacuum. Or is it?To the unaided eye, space appears to be a vast, dark void, and the Sun a tranquil sphere of light. But in fact, space is not empty. That's because we live in theatmosphere of our dynamic Sun. With the advent of radios, RAM, and rockets in the 20th century, scientists found that Earth's environment stretches thousands of miles intospace, and the Sun brings us far more than just daylight. We actually live inside the atmosphere of the Sun. From observatories in space and on the ground, physicists nowstudy an invisible realm as changeable as the weather, windier than a mountain peak, and as electric as a city night. They call it geospace...Earth's space. Our solarsystem has the cosmic equivalent of winds, clouds, storms, and hurricanes -- scientists call it space weather. Just like weather on Earth, it can be both mild and wild.