From the start, the sky lies. Two bright planets can hang almost edge to edge, a slim gleam between them, and the eye quietly reports intimacy. On a clear night that gap looks like the distance across a thumbnail. In geometric terms, though, it is only an angular separation, measured in degrees and arcminutes on the dome of the sky.
What feels like a narrow slit is often tens of millions of kilometers of vacuum, set by orbital mechanics and Keplerian motion rather than any human sense of scale. Light rays from each world arrive along nearly parallel paths, so the retina builds a single flat projection and strips away depth. The brain, trained by terrestrial distances and binocular vision, accepts that flat projection as proximity, even when those points sit on wildly different orbits around the Sun.
This is not a charming quirk; it is a warning about how easily perception compresses danger into something that seems almost friendly. Between those planets sits hard radiation, micrometeoroids, and a near-perfect vacuum, described by pressure values far below any laboratory cleanroom. Yet from a backyard, it all collapses into a pretty pair of lights, close enough, it seems, to reach with a fingertip.
