Final answer:
Saturn's rings were first observed about 400 years ago, but scientists could not see them in three dimensions until 2009.
Step-by-step explanation:
From the given facts, we can conclude that scientists were not able to see Saturn's rings in three dimensions until 2009, although they were first observed about 400 years ago. This suggests that the technology and instruments used to observe Saturn's rings have significantly advanced over time. The ability to see the rings in three dimensions has provided scientists with a better understanding of the structure and composition of Saturn's rings.