When I look at Cassini images of Saturn – with its multitude of rings and fleet of moons – I am inspired, moved, and even awed.
And sometimes I laugh. When I saw this image, for example, I actually chuckled to myself. Why?
[Click to encronosenate.]
This gorgeous shot was taken on December 30, 2011 and released just today as the Cassini Image of the Week. It shows Saturn’s gorgeous rings seen nearly edge on, and the tiny moon Epimetheus, only 113 kilometers in diameter, next to them.
It’s a lovely image to be sure, and my very first thought was; I wonder if Epimetheus is closer to us than the rings, or farther away? If we’re looking down on the rings, from the north, then Epimetheus is closer to us. But if we’re looking up from underneath the rings, Epimetheus is on the other side of the rings. I could mentally switch my perspective back and forth, but I couldn’t tell which view is correct! This prompted my chuckle, as I wryly smiled at my brain’s confusion (I love optical illusions).
So take another look: are we looking down on the rings, or up? Hint: the Sun is shining from the north, down on the rings.
It’s a bit of a conundrum, isn’t it? Just by looking it’s almost impossible to figure out! If you’re familiar with Cassini pictures, the rings look subtly different if they are illuminated from above and you’re looking at them from underneath, and vice-versa. But it’s hard to tell. And to be honest, I wouldn’t have known without reading the caption for the image.
The answer is we’re looking up. The Sun is shining down on the top of the rings, and we’re looking up from underneath, putting wee Epimetheus about 1.5 million kilometers (900,000 miles) from Cassini when this picture was taken. If it helps, hold up something round like a DVD and look at it from underneath. As another helpful guide: in the image above, the part of the rings at the top of the picture are closest to you, the bottom farther away, and Epimetheus father still.
And I bet that even knowing that, some of you are having a hard time picturing it. Our brains are funny things, easily fooled when there’s symmetry in a picture, especially when that picture shows an unfamiliar object. I’m sure Carolyn Porco can just glance at something like this and figure out everything she needs to understand the geometry! I’m not so sure I could’ve.
Remember: seeing isn’t always believing. It’s easy to fool our eyes and brain, but in the end the Universe knows what it’s doing.
Image credit: NASA/JPL-Caltech/Space Science Institute