Rachel, I'm not a historian, but I've heard about an interesting example of Christina's comment about learning a lot from the light and other particles coming from the Sun. I've read that one of the more common elements on Earth, helium, that makes balloons float up in the air, and can be found in many natural deposits on Earth, was actually first discovered 140 years ago, on the Sun! This happened because a French astronomer was observing light from the Sun's upper atmosphere, during a solar eclipse in 1868. He noticed a special kind of light, with a wavelength that became visible only during the eclipse. It looked almost like light from sodium, but not exactly, so the astronomer guessed it came from a special element that perhaps, he thought, only existed on the Sun, because at that time it was unknown on Earth. So they called this imaginary element helium, which means literally "of the Sun," because the Greek word for Sun is Helios. Later helium was found by geologists, and the same kind of light, with the same wavelength, showed that it was the same element known first from the Sun!