11/17/2023 0 Comments Solstice and equinox animationNotice also that the altitude of the Sun at 65°N at noon is 90°– 65° = 25° at the equinoxes ( Figure 3). The range in Rome is thus only about 60°. For comparison, the approximated sunset in Rome at 42°N at winter solstice is at 241° on the horizon, and at summer-solstice it is at 300°. The range of the sunset in Iceland during half a year is therefore about 140° out of the 180° possible range. At winter solstice the sunset in Iceland at 65°N is at 200° on the horizon, while at summer solstice the sunset is at 340° ( see Figures 4 and 5). We notice in all three models that the track of the Sun is flatter at northern latitudes than it is closer to the equator. The 0°–360° scale on the horizontal axis denotes the placement of the Sun on the 360° horizon (the azimuth) during 24 hours, while the scale on the vertical axis denotes the altitude in degrees.įigure 3: Simulation of the Sun track seen from Iceland at 65°N and from Rome at 42°N at equinoxes in March and September points A and B show location of sunsets for each location.įigures 4 and 5 show simulations of the Sun track at the two solstices.įigure 4: Simulated tracks of the Sun, seen from Iceland at 65°N and Rome at 42°N, at winter solstice when the declination, –23.44°, is subtracted from formulas for altitude of the Sun at equinoxes.įigure 5: Simulated tracks of the Sun, seen from 65°N and from Rome at 42°N, at summer solstice when the declination, +23.44°, is added to formulas for altitude of the Sun at equinoxes. In Figure 3, the altitudes of the Sun at 65°N and 42°N through 24 hours at equinoxes in March and September are approximated by the functions: The Mediterranean area was considered the middle of the Earth in medieval times, and Rome was the center of the Christian Church that decided upon the official calendar of the Western World. We will now model the observed Sun track at 65° North, the latitude of the farm of Thorsteinn Surtur, and for comparison at 42° North, the latitude of Rome. ( Note: Animation requires the Flash plug-in, included for instance in the Google Chrome browser.) (from the Astronomy Education at the University of Nebraska-Lincoln website). In contrast, the visible path of the Sun at the December solstice is shorter when viewed in Iceland than it is when viewed in Rome.Ĭlick here for a simulation showing how the declination of the Sun varies over the course of a year At the June solstice, the Sun’s path as viewed in Iceland begins and ends further north, and the visible path of the Sun is therefore longer than it is when viewed in Rome on this same date. The further north the location is situated, the greater is the inclination of the Sun’s path with respect to the horizon. The horizontal circle denotes the horizon. At equinoxes in September and March, the axial tilt does not have an effect on the observed Sun track.Īs viewed from Iceland (65° N.) As viewed from Rome (42° N.)įigure 2: Sun’s path in the sky, with points of sunrise and sunset, at June solstice (red), equinox (black), and December solstice (blue)įigure 2 shows the paths of the Sun in the sky at the solstices and equinoxes as viewed from Iceland (65° N.) and Rome (42° N.). In the northern hemisphere, the maximum tilting towards the Sun is at summer solstice in June and the minimum at winter solstice in December. Whichever hemisphere is currently tilted toward the Sun experiences more hours of sunlight each day. The axis remains tilted in the same direction throughout the year however, as the Earth orbits the Sun, the hemisphere tilted away from the Sun will gradually become tilted towards the Sun, and vice versa. The axial tilt is currently about 23.44°. The axial tilt of the Earth is the angle between the Earth’s rotational axis and the normal vector to the orbital plane around the sun.
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