(agglomeration)

In 1609, hearing of a telescope built by a Dutch eyeglass maker, Italian scientist Galileo Galilei put together his own version, consisting of a convex lens and a concave lens mounted in a lead tube. "Bringing my eye to the concave lens," he noted, "I saw objects satisfactorily large and near." In the next few years, he saw craters on the Moon, sunspots on the Sun, the rings of Saturn, and four moons of Jupiter.