Empirical Earth · The Sky — Sun, Moon & Stars

The analemma

The claim

“The Sun just circles overhead on a flat plane.”

What is true

The Sun does appear to move in a simple arc across the sky, and from one spot on one day it looks like nothing more complicated than that.

What is measured

Photograph the Sun at the same clock time all year and it traces a figure-eight, the analemma, written by Earth’s 23.4° tilt and elliptical orbit.

What would show this is wrong

the Sun, photographed at a fixed clock time across the year, tracing no figure-eight.

Sources

  1. NASA NSSDCA — Sun Fact Sheet. NASA Goddard Space Flight Center. nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html link
  2. The analemma & the equation of time. The Sun's annual figure-8 from axial tilt (23.4°) and orbital eccentricity; equation-of-time ≈ ±16 min. analemma · NOAA solar calculator . link
  3. The equation of time — its two causes. The Sun’s up-to-±16-minute lead/lag over clock time is the sum of an obliquity term (~±9.9 min, half-yearly) and an eccentricity term (~±7.7 min, yearl link
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