Expert: Jayendra Upadhye - 11/2/2005

Question
I am sorry to bother you and I appreciate you taking the time to answer my question...why is it that as the earth rotates the constelations change positions in the sky and move along with the earth, however the north star always stays in the same place...how can this be?

Thank you again for your time.

Answer
Hi Stephanie,
Why! the answer is very simple!
In your own room, stand below a particular area under the cieling, such as a lamp or fan or fixture.
mow mark your visual surroundings carefully.

Turn 90 to your left.
now what was to your left, actually faces you.
And what was to your right, is avtually behind you.

if you turn 3 times more in 90 degree steps ..always to your left, you will be facing the original view you had before you right at the start of this excercies.

Now substitute that spot on the ceiling with the pole star. (imagine it so that is..).
The constellations are nothing then but areas in your visual field that are on top of your head, meaning in front if you, "below your feet" ..meaning on the other side, the day side of earth, "to your left/right" ..meaning on one of the east/west horizons.

Your head would be alligned to the pole star and your legs pointing to the southern pole.

Got it?
The earth is turning, but the pole points "always" to polaris, the pole star. No matter how you turn, the pole star always remains "fixed".

depending on your latitude, the pole star appears (latitude in degrees north) degrees above the horizon.

At the equator, it is on the north horizon.
at the poles it is 90 degrees or directly overhead.

Just measuring altitude of polaris above the northern horizon will tell you your latitude, always!

Though you appear too young, let me tell you this..the pole star will never remain as such for too long!

every few thousand years (gradually for us to feel it), the earth tilts and points to another star in the northern regions, until after many thousand years it points to polaris again!
they call it "precession of the equinoxes"..but let that remain a mystery for you until you are old enough to know!

A sort of harry potter mystery for you!
Jayen