An analemma is a curve that represents the position of the sun in the sky at the same time each day over the course of a year, when plotted against time. If you take a photograph of the sun’s position at the same time each day, you would see a figure-eight shape—this is the analemma.
How does it relate to timekeeping?
The analemma is connected to timekeeping because it helps explain the equation of time, which is the difference between solar time (what we get from a sundial) and clock time (the time shown by our mechanical clocks). The shape of the analemma arises because:
- The Earth’s orbit around the sun is elliptical, not perfectly circular, so the speed of Earth’s motion around the sun varies.
- The Earth’s axis is tilted, which also causes variation in the length of the day throughout the year.
Because of these factors, solar time doesn’t exactly match the time kept by a clock, and the analemma visually shows this discrepancy throughout the year.
- When the sun is higher or lower on the analemma, the solar time is ahead or behind the clock time.
- The figure-eight shape of the analemma reflects the combination of these two factors: Earth’s changing speed in its orbit and its axial tilt.
In modern timekeeping, we rely on standard time and clocks, but the analemma is a reminder of the natural, astronomical processes that govern how we track time on Earth.