How to build an analem?

How to build an analem?

This word means a number of sequential positions of the Sun in the sky at the same time during the year. As you know, the sun rises every day, and goes at different times, and its path along the sky is changing all the time. These nuances of the annual path of our star can be seen in the same photo, if during the year the same frame, at the same time to shoot several dozen positions of the sun.

The Earth, as we know, rotates not only around its axis, but also around the Sun, and both of these axes are not parallel. That is why spring replaces winter, and autumn – summer. There may be a view that our planet simply turns to the sun by one or the other with its pole. In fact, by virtue of the law of preservation of the moment of impulse, the Earth simply retains its rotational orientation, circling around the sun. Therefore, the sun has no choice but to alternately highly cover the northern or southern hemisphere.

Again, due to the fact that the earth’s axis is not perpendicular to the plane of the earth’s orbit, the duration of the day and night and the average daily temperature are changing during the year. Analem just shows a change in the position of the Sun in the sky during the year, and its eight -shaped elongated species is due to the joint effect of the ellipticity of the earth’s orbit and the inclination of the earth’s axis to the plane of the ecliptic. The image of analem was often applied to ancient globes and sunshine, and there it depicted the function of the “Time equation”, allowing you to determine the amendment to the testimony of the sundial, which could reach a quarter of an hour.

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