Here is your weekly reminder of Psalm 19 — the planet Mercury.

Mercury is the smallest planet, as well as the planet closest to the Sun. It has a remarkably long day — a Mercury day lasts 88 Earth days — and a relatively short year (116 Earth days). Because of the peculiar ratio of its orbital period to its rotational period, a hypothetical observer on Mercury would experience only one day for every two years.

Mercury has no atmosphere, so the range of surface temperatures is extreme — -280 F during the night (the part of Mercury that faces away from the Sun) and up to 800 F during the day (the part of Mercury that faces toward the Sun).

Mercury has the most eccentric orbit in the Solar System, which means that out of all the planets, its orbit is the most like an ellipse. The part of its orbit closest to the Sun (the perihelion) precesses, which means Mercury’s orbit spirals around the Sun like a spirograph. Newton’s version of gravity could account for some of this precession, but not all of it. The reason for the discrepancy remained a mystery for centuries, until Einstein formulated his General Theory of Relativity, which explained the precession in terms of the way the Sun warps space around Mercury.

Image credit: NASA.