For most of us, Earth's environment ends somewhere above the clouds
but below the space shuttle. The burning ball of gas we call the Sun
hangs in the sky, marching from horizon to horizon and spreading
sunbeams and sunburns. The 93 million miles (150 million kilometers)
of space between the Earth we know and the star we see is just empty
black space, avacuum.  Or is it?
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With the advent of radios, RAM, and rockets in the 20th century,
scientists found that Earth's environment stretches thousands of miles
into space, 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 now study 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."
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