Track sun’s shift between now and solstice - Beyond The World
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Track sun’s shift between now and solstice

Equinox fun: Track the sunset point

The movement of the sun along your horizon from day to day – at the sunrise or sunset point – is especially evident around the equinoxes. Many streets in the United States and other regions of the world are also oriented north-south or east-west. So, in the weeks and months following the March equinox, you might be able to track the sun’s movement from south to north just by staring out your front door.

The sun rises directly in the east and sets directly in the west on the equinox. Each day after that, you can see it migrate further north. You don’t have a street grid to guide you? Track the sun’s movement along the horizon by taping pieces of tape to an east or west-facing window in your home. Alternatively, pick a clear area – one where you can see the horizon – and stand in the same place every time you view the dawn or sunset. You’ll notice how the sun moves in relation to the trees and other items in the foreground.

Just make sure you observe from the same spot every day. It’s enough to take note of the dawn and sunset times every week or ten days. Between now and the June solstice, the sun will move northward.

What happens at the solstice?  There is a two- to three-week period in mid-northern latitudes when you won’t be able to see any movement of the sun down the horizon. That is where the term solstice originates. Solstice = sun still.

How much does it move?

A reader sent us with a question about the migration of the sunset or dawn along the horizon when the Earth changes seasons. He wrote:

Hello, I’m curious to know how far the sun moves north or south along the horizon each day? Like half its width? A quarter of its width?

The answer is that the degree of movement of the sun over the horizon is determined by two factors:

1) The time of the year.

2) Your latitude.

As previously stated, the movement of the sun over your horizon – whether at sunrise or sunset – is most perceptible around the equinoxes and least perceptible around the solstices. Furthermore, the sun’s daily movement along the horizon is larger the farther north or south you are from the equator.

For example, on the day of the March 20 equinox, the sun rises due east and sets due west at roughly 40 degrees north latitude (Denver, Colorado; Sardinia, Italy; and Beijing, China). On April 4, two weeks later, the sun rises about 7 degrees north of due east and sets about 7 degrees north of due west. Because the diameter of the sun equals 1/2 degree, the sun has been traveling its own diameter (14 days x 1/2 degree = 7 degrees) northward on a daily basis.

On the day of the equinox, the sun rises and sets close to straight east and due west in 65 degrees north latitude (Fairbanks, Alaska; Siberia; Iceland). However, the sun rises and sets around 14 degrees north of due east and west two weeks later, on April 4. So, during the two-week period from the spring equinox to April 4, the sun moves about one degree (2 sun-diameters) along the horizon at this far-northern latitude.

Diagram: Person standing with the setting sun in distance at 3 locations left to right.
This Chicago Tribune image, which is related to an article about Chicagohenge, depicts a person looking toward sunrise. Many people now mark their personal solstices and equinoxes with dawn or sunset sightings in familiar surroundings, as seen in this shot from Ben Orlove from the December solstice in 2016.

Bottom line: The amount of movement of the sun along your horizon – at sunrise or sunset – varies depending on the time of year and your latitude. It is most perceptible during the equinoxes and least perceptible around the solstices.

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