Splendid. As the Wikipedia entry for this lithograph points out:
In the world of Relativity, there are actually three sources of gravity, each being orthogonal to the two others. Each inhabitant lives in one of the gravity wells, where normal physical laws apply. There are sixteen characters, spread between each gravity source. The apparent confusion of the lithograph print comes from the fact that the three gravity sources are depicted in the same space.The odd thing is that there are three, rather than four: in fact the 'gravity well', or line of alignment, that is missing is the upside-down axis, running from the bottom of the image to the top. This adds a nice foursided-triangle vibe to the whole.