http://www.danheller.com/star-trails.htm鈥?/a>
This link shows long exposure time photos of the stars which demonstrate the rotational movement on the North-South axis.
The Star at the centre of the circles is Polaris which is almost directly above the North Pole.
That is the movement over the hours of darkness during the 24 hour cycle.
For the Yearly cycle it's easiect to describe using the constellations of the planetary elipse, also known as the Zodiac.
Each month the Sun appears to occupy one of these constellations, you can't see this constellation at the time because it's on the day side and hidden by the glare of the Sun, the opposite constellation is visible at night between the Tropics.
http://en.wikipedia.org/wiki/Zodiac
http://homepage.mac.com/kvmagruder/bcp/z鈥?/a>Why if the earth is really spinning and revolving round the sun do we see the same stars every clear night?
For navigation, sailors used Polaris, this gave them North.
You find it by locating Ursa Minor.
Once you know where North is you also know where East, West and South are.
http://en.wikipedia.org/wiki/C鈥?/a>
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These are special case stars.
Take your latitude value and subtract it from 90 degrees.
Get a star chart and look for any stars that have a greater declination, (celestial latitude), than the value of your answer.
these stars are called ';circumpolar'; for your latitude.
these stars will never be below your horizon, although they will be at different altitudes at different times of the year.
all the other stars on the chart will pass below your horizon at one time or another.
Using the same calculation, and applying it to the opposite hemisphere, will give you the stars that will never rise above your horizon.
For instance, in Chicago, you can see the ';Big Dipper'; all year long but you can never see the ';Southern Cross';.
Also, because of orbital position, the night time stars of the winter, such as those in Orion, are visible during the winter months, and those in ';The Scorpion'; are visible at night in summer.
The earth turns on its own axis continuely, but one revolution takes 24 hours. Each night you are looking at the same part of the sky just moved over about 1/365th of the earth's trip around the sun from the last night.
Only the stars overhead are visible all year round. The lower stars, near the horizon, can only be seen some of the year. If you looked straight up at a street light, you could rotate around and still see it. But if you looked at a mailbox 10 feet away and rotated, it would pass out of view.
th strs al cme frm sam plac trvlin a th sam spee
YOu will see the same one's at the same time of the year every year. But the sky changes as we revolve around the sun, just a little bit every night. Except for the planets. They change all the time some are fast and some are slow, depending whether they are inner planets or outer planets.
Take for an example, you are sitting on a Fair ground ride, a merry go round, as you spin around the centre of the merry-go-round (the sun) and you look out across the fair ground you see different things as you go around. But you will see the same things in the same place next time you go round. Except for the people (the planets) who are moving around fast.
Hope that helps.
The stars are moving it is just that they are so far away that they only vary in the sky at most 1 sec of arc. (Too small to be noticed.) Over the course of centuries some movement can be noted that is because everything is moving in space. The event you described is called parallax.
http://tech.groups.yahoo.com/group/NeatA鈥?/a>
If you walk around the playground you do not see different buildings depending where you are.
Now think the same thing but bigger.
The Earth spins on it's axis once every 24 hours. Therefore, when it is nightime at your location, you are looking into that 'same' part of the sky which is facing away from the sun.
Now imagine, you are standing at the same spot at the same time each night looking in the same spot in the sky. As the Earth orbits the sun, its path moves it that little further along this orbit in an anti clockwise direction. Therefore, your view of that particular part of the sky will move in an anticlockwise direction too allowing you to see 'new' stars as your viewing angle moves in unison with the orbiting Earth.
The stars you are seeing in January will not be visible in 6 months time because they would have 'moved' in a clockwise direction and would be directly behind your line of sight in July.
You actually don't see the same stars every night. They change as the year goes by
1. The earth takes a really really really long time to spin around the sun.
2. The universe is gigantic. And you need to realize the angle at which we are viewing the stars.
the stars we see also travel in a ciircular motion and they are 23.5 million yards wide
Watch Orion over winter. It is quite brilliant when directly overhead in December, then it passes over and fades away towards Summer
Depends on the time of year... I cant see the same stars like 6 months apart!
the earth revolves in a 24 hr period while it takes 365 days to circle the sun. if you look closer, the stars are in a different place each night.
The Earth really is rotating on its axis and it really is orbiting the sun. The stars you see at night only appear to be the same over the course of a few weeks at a time. You will see a very different starry night in December than you will in July for axample due to the fact that the Earth has moved along its orbital path by quite a considerable distance and you are therefore looking at a different section of the night sky. Take the constellation Leo for example, quite clearly visible in on a winters night and nowhere to be seen on a summers night. The only time you will see the same stars in the same positions in the night sky is on the same night the following year and even then this is not technically accurate due to the relative/apparent motion of the distant stars year upon year. Hope you're a little less confused now !!!!.
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