Earth

Earth

There are certain facts about the Earth that you need to remember.

It is a sphere. Its actually a bit squashed so that its diameter is bigger at the equator than it is at the poles. Its average diameter is 13,000km.

How do we know it is a sphere? Here are two early pieces of evidence

When you watch a ship sail away the lower half of the ship seems to disappear below the horizon before the top half. This is due to the curvature of the Earth.

When you travel north Polaris and the constellations around it appear higher in the sky. Seeing this it is easy to imagine a spherical rotating Earth. Of course now that we…