The brightest object in the sky is the sun - so bright, in fact, that it's difficult to look anywhere near it because of its blinding brilliance. One rumor often heard is that the Italian astronomer Galileo went blind from viewing the sun through a telescope, but it’s not true: he used his telescope only to project the sun’s image onto a viewing surface, which is perfectly safe. Long before the invention of the telescope, ancient Greeks observed and described large sunspots, perhaps 40,000 miles across that sometimes appeared on its face. They did this by watching the sun only while it was rising or setting, and at its dimmest. As you may have guessed, this is definitely NOT a safe practice: even though the amount of visible light is cut down by the thick column of air at the earth's horizon, the sun is still emitting invisible radiation which can blind you. So never stare at the sun, even at the beginning or end of the day.