Imagine if you could see only the front of your home and that no matter what you did, the back side remained hidden. Weird and frustrating? That's how astronomers feel a lot of the time because humans can observe only one side of some of the most intriguing places in the universe.
The most obvious example is the moon, which always keeps one hemisphere facing Earth. That is why every month we see the same man-in-the-moon pattern. This friendly looking formation—created by a group of ancient lava flows that are slightly darker than the surrounding surface—is most noticeable when the moon is roughly full, August 7 to 12 this month.
Astronomers had long assumed that the farside was just like the near side. Wrong. Pictures of the hidden hemisphere, first taken in 1959 by the Soviet spacecraft Luna 3, show a vastly different landscape. Now we know that the moon ...
