Humans like alignment. We like perfection.
Every year, planets orbiting the sun beyond Earth’s orbit reach what astronomers call “opposition.” That means when they appear in the sky at the position opposite that of the sun. At opposition, the planet (it could also be a satellite or asteroid) and the sun line up with Earth between them.
Pluto and its moons were at opposition on July 8, 2016 and in this case the alignment was perfect. That means something that I don’t quite understand. I read that if you were standing on the surface of Pluto or one of its moons and looked at Earth, you would see Earth transit (or move across) the solar disk.
Oh, it has to do with the Line of Nodes, the intersection of the plane of the Earth’s orbit and a planet’s orbit. I don’t get it, but it’s interesting.
I do like the idea that things eventually align.
Pluto was last near one of these perfect alignments in 1931. But it will be there again in 2018, and then, oddly, because of the eccentricity of Pluto’s orbit, it will be another 161 years until the next perfect alignment.