Complex Numbers

The Far Side

Well, it missed the full moon by a couple of days, but this one finally came up from my queue for me:

Why the Moon’s two faces are so different  
The far side of the Moon is incredibly different from the Earth-facing side. 63 years later, we know why the Moon's faces are not alike.

Article has a helpful picture of both hemispheres of the moon up at the top, and lots of other pretty pictures scattered throughout.

The Moon, by far, is the brightest object and largest object that’s visible to human eyes in Earth’s night sky.

I was about to object to this until I realized that it means that it appears the largest, not that it's the largest object, in absolute terms, that we can see. That would probably be a star somewhere, depending on your definition of "object."

So to satisfy my urge to be pedantic, I'll point out that one can often see the moon in the daytime sky, as well, during certain phases when it doesn't appear too close to the sun.

With even an off-the-shelf pair of binoculars or the cheapest telescope you can find, there are two main features about the Moon that you can’t miss:

That it's made of cheese and it's round?

In addition, because the Moon’s orbit is elliptical, moving faster when it’s closest to Earth and slower when it’s farthest away, the face of the Moon that’s visible changes ever-so-slightly, a phenomenon known as lunar libration. Even though this means, over the course of many months, we could see up to a total of 59% of the Moon, it wasn’t until 63 years ago, when the Soviet spacecraft Luna 3 swung around to the far side of the Moon, that we got our first pictures of the far side of the Moon.

Because of this, most of the features of the far side are named in Russian.

Although it wasn’t very impressive in terms of image quality, it was remarkable for an unexpected reason: the near side of the Moon appears vastly different, in terms of both cratered features and maria features, from the far side that always faces away from us. This discovery came as quite a shock, and for decades, even as our imaging and understanding of this elusive side of our nearest planetary neighbor improved in quality, we lacked an explanation as to why this difference existed at all.

The rest of the article explains just that, and it's pretty cool, not only for the explanation, but for the observations, deductions, and science that got us there. Which is fascinating, but there's not a lot of point in rehashing it here.

Then:

No matter how wild or unusual your idea may be, if it has sufficiently strong explanatory power to account for what we observe, it just might be the necessary idea to solve whatever puzzle it is that you’re considering.

Until some better observations come along, of course, and change everything we think we know. But that, too, is part of the awesomeness of science.