Why Does the Sun Seem to Go Up and Down in The Sky?

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Like everyone else, you have seen the Sun move in the sky during the day following an arc. In reality it is an illusion because the Sun does not move! It is the Earth that turns on itself in 24 hours, precisely in 23h59m4s and that gives the impression that the Sun moves from East to West. To verify it, it would be enough to take a rocket and stay a minute above a landmark to find that the Earth actually moves in its orbit around the Sun and turns very quickly on itself.

It is said that the sun rises in the morning and goes to bed at night. Once again, the reality is different: the Sun is a star and therefore shines constantly, 24 hours a day, and when it’s dark at home in far away countries, on the other side of the Earth, in Japan or in Australia it is day! This phenomenon represents the cycle of the day and the night and depends on the rotation of the Earth on itself with respect to the Sun.

The Earth also rotates around the Sun in an orbit that almost looks like a circle, called an ellipse. The Earth (escorted by the Moon) advances at about 30 km / s or 108000 km / h, and despite this very fast speed, it takes 365 days 5 hours 48 minutes and 46 seconds, or a year to go around and return to the same apparent place, what is called a revolution around the Sun.

In summary, the illusion that the Sun moves higher or lower and descending into the sky is the result of the combined effect of several phenomena: the rotation of the Earth on its axis gives the impression that the Sun moves in relation to the ground, the inclination of the axis of rotation of the Earth on the plane of the ecliptic and the latitude of the place give the impression that the Sun rises higher or lower in the sky according to the seasons . As seen above on the left, at 45 ° North latitude, in summer on June 21 the day lasts 16h10m while in winter, December 22 the day lasts only 8h15m.


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