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Gleb Tyunikov

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how can it be that we always see the same night sky any time of the year?

earth is moving around the sun and changes its place in space so how can it be that the night sky and the star patters that we see today is the same as we saw few months ago though we moved in space and should see other stars??

Topics: space
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  • Apr 28 2013: Ummmm - it isn't the same. Each day about there is about a 1 degree shift (360 degrees and 365 days) that alters the orientation of the sky.
    The earth orbits the sun (suprisingly 50% of people in the USA get this part wrong) and that means that part of the time the earth is looking one direction at midnight and 6 months later looking the opposite (say you are looking down at the earths orbit from above the north pole of the sun)
    Now if you are in the northern hemisphere you can always see the northern stars although they will seem to revolve around the earth if you look at the same time every night, but also constellations near the ecliptic will come into view during winter that are not there during summer. For example, I can only see Orion the hunter in winter.
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      May 15 2013: Gosh, it has been so long since I went to the Burke-Baker Planetarium! Polaris is fixed as the North Star, but the other 6 stars in the Little Dipper (Ursa Minor), the Big Dipper (Ursa Major), Cassiopeia, Draco, Cepheus, Camelopardalis, and everything else in the sky of the Northern Hemisphere revolves around Polaris. The six constellations I named are called circum-polar constellations. They never set. The make a complete circle every night around the North Star, Polaris.

      The axis of the Earth is pointed at Polaris. So Polaris looks like it never moves. Most of the other constellations rise and set every night. They follow like the Sun & Moon moving east to west across the sky. Because the Earth is tilted, we have seasons. That tilt changes how high the sun is at noon.

      The Summer Solstice in late June and the Winter Solstice in late December are on opposite ends of the Earth's orbit around the Sun. In the Northern Hemisphere the Sun is Highest in the sky in June; lowest in December. The sky looks very different on those two days. The stars move in the sky very much like the sun. They move across the sky at night and will rise and set at various times. The stars that are closest to the Sun's path in the sky are highest in late June and Lowest in late December. And some drop completely below the horizon and are only visible during certain times of year.

      Many constellations visible in the USA or Europe/Asia in Winter are below the horizon in Summer. And although you can still find the circum-polar constellations that never set, some stars you can't see depending upon the time of night and the time of year. Things are reversed in the Southern Hemisphere. In most parts of the Southern Hemisphere you never see Polaris at all. This is hard w/only 2000 characters

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