Question

How does pole star and horizon help in fending the
shape of the earth?​

Answer 1

Answer:

If you observe the pole star from different locations on earth, you find that the altitude of the pole star differs from place to place. This can happen due to two reasons:

We live on a flat earth and the pole star is quite close to the earth, so that the angle of the pole star above the horizon will change. We can even calculate the way the altitude changes as we move a fixed distance northwards or southwards: this is a trigonometrical function of the distance moved.

We live on a spherical earth. Again, we can predict how the angle changes with distance moved northwards or southwards, it should be the same no matter where on earth you start with.

Observations tell you that the second is correct. BTW, there is one more prediction of a spherical earth, i.e., the altitude does not change if you move eastwards or westwards. This shows that the earth curves in both N-S and E-W direction.

BTW, if we live on a flat earth and the pole star is extremely far away, then the altitude will be the same for all points on the earth.

In principle, you can do the same observations with any other star, but the advantage with the pole star is that its altitude is fixed as a function of time (other stars move in circles around the north celestial pole, so both their altitude and azimuth change with time.)

Answer 2

The North Star or Pole Star , also known as Polaris, is famous for remaining nearly stationary in our sky while the entire northern sky revolves around it. This is due to its proximity to the north celestial pole, the point around which the entire northern sky revolves. Polaris, contrary to popular belief, is not the brightest star in the night sky. It ranks about 50th in terms of brightness. But you can find it easily, and once you do, you'll be able to see it every night from Northern Hemisphere locations.

The Pole Star can be seen at an angle of 90° at the North Pole because it lies directly on the earth's axis, and its angle decreases towards the Equator, where it is 0°. It can only be done in a quarter arc of a circle. It establishes the earth's shape as a sphere with a circular surface.

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