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Physics, Astronomy & Cosmology / Re: After the Winter Solstice, why does the time of sunrise not get earlier?
« on: 18/01/2020 21:03:42 »
The date of the winter solstice is 22 December (in the Northern hemisphere; initially Google told me the winter solstice was 22nd June!). After this, the days start getting longer. This is determined by the axial tilt of the Earth.
The date of perihelion (the point where Earth approaches the Sun most closely) is on 4th January, for both Northern & Southern observers. After this, the Sun will start to rise earlier. This is determined by the elliptical shape of the Earth's orbit.
As the earth approaches perihelion, it moves more rapidly through space, and this means that sunrise continues to get later for 2 weeks after the solstice.
These two effects are combined on the analemma often displayed next to a sundial.
The date of perihelion (the point where Earth approaches the Sun most closely) is on 4th January, for both Northern & Southern observers. After this, the Sun will start to rise earlier. This is determined by the elliptical shape of the Earth's orbit.
As the earth approaches perihelion, it moves more rapidly through space, and this means that sunrise continues to get later for 2 weeks after the solstice.
These two effects are combined on the analemma often displayed next to a sundial.
Quote from: Wikipedia
The analemma is plotted with its width highly exaggerated, revealing a slight asymmetry (due to the two-week misalignment between the apsides of the Earth's orbit and its solstices).See: https://en.wikipedia.org/wiki/Analemma#As_seen_from_Earth
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