Why North Pole always points to the North Star throughout the year?

[kingwinner]

Why earth's Geographic North Pole always points to the North Star throughout the year? The earth is revoluting around the sun so the Geogrpahic North Pole should point at different locations at times of summer and winter...it just can't be the some location...

For example, when you hold a pencil vertically and revoluting in big circles, each moment your pencil is pointing a differnt location...

Can someone briefly explain why? Thank you!

[Turtle]

___The diameter of Earth's orbit around the Sun is very tiny compared to our distance from Polaris & so makes the position of Polaris relative to us appear stationary. Interestingly enough Polaris hasn't always marked the Geographic North Polar axis & in some tens of thousands of years a different star takes over as the marker.

[nkt]

Polaris is just a coincidence.

For the south pole, there is no such star, so the calculation has to be done using a constellation called the "Southern Cross". Once you find it, you draw a line between them as a cross, and the intersection of the two lines gives you the south pole.

However, don't rely on either these for extreme accuracy. It is only roughly right. Also, don't forget that true north and magnetic north are not the same, and you need to use a small offset depending on where you are in the world. Some small places miss the true north by up to 15 degrees from your compass reading!

[Qfwfq]

The reason is called angular momentum. Earth is like a huge gyroscope, although not a very good one since it is near spherical. Earth rotates and has a motion called precession with a period of 26 thousand years, that's how long it will be before the axis will come round to the current direction. Right now Polaris isn't exactly on this direction, the difference being a couple of degrees. The stars also move over the millenia.

Over the years the changes are small but the equinoxes and solstices have been slowly getting earlier, century after century, this is called precession of the equinoxes. You might ind this helpful:

http://en.wikipedia.org/wiki/Gyroscope

[kingwinner]

Thank you everyone!

I like this sentence and this explains clearly to my question:
"The diameter of Earth's orbit around the Sun is very tiny compared to our distance from Polaris & so makes the position of Polaris relative to us appear stationary"

[kingwinner]

All stars, including Polaris and our Sun, are stationary, right? Then why would "red shift" occur, meaning that almost all galaxies (a system of stars) are MOVING away from the earth? Why are stars moving, which contradicts the first sentence?

[C1ay]

Originally Posted by kingwinner

All stars, including Polaris and our Sun, are stationary, right?

No

[kingwinner]

Originally Posted by C1ay

No

How come? So the Sun is moving? I was told that the Sun is stationary and the planets orbit around the Sun...

[C1ay]

Originally Posted by kingwinner

I was told that the Sun is stationary and the planets orbit around the Sun...

Stationary relative to what? So far, the standard interpretation of the vast amount of redshift we see is that the universe as we know it is expanding. Our sun is but a lone star in a galaxy with billions of other stars that are moving. It's just that the scale of the universe is so large and we are so small that the stars appear stationary.

[HighSpeed]

Originally Posted by kingwinner

How come? So the Sun is moving? I was told that the Sun is stationary and the planets orbit around the Sun...

Earth and the other planets are revolving around the sun, the sun is revolving around our galaxy, our galaxy along with other galaxies are revolving around in the universe. Now its also possible that, the universe is revolving around, with other universes. Its a cycle really.

In a few thousand years, there will be a shift amongst the stars. The current north star will no longer be the north star, instead it will be Vega.