1. The earth
The Earth is one of the nine planets in the Solar System . In the olden days, some people thought that the Earth was flat but other people imagined it was square. Nowadays, we know that its shape is similar to an orange, that is, as a sphere with flattened poles. This form is called the geoid.
In the upper picture, we see that a vessel gets away from the coast with a man and a lighthouse. At the begining the man hides out and later the lighthouse is no longer seen. This shows that the earth's surface is circular.
2. Lines and circles of the globe
To locate a particular point on the Earth's surface, It has been found that on the globe exist a number of imaginary points, lines and circles. These are:
- The axis: it is the line where the Earth spins around. It runs from the North Pole to the South Pole and it is tilted with reference to the plane of the earth's orbit around the Sun.
- The Equator: it is the great circle perpendicular to the earth's axis. It divides the earth into two equal parts called hemispheres: the northern or boreal hemisphere and the southern or austral hemisphere.
- - The Meridians: they are semi-circles passing through the poles. They are vertical lines.
- The parallels: they are circles parallel to the Equator . They have different sizes : the biggest are close to the Equator and the smallest are close to the Poles . The most important parallels are four: the Tropic of Cancer and the Arctic Circle in the northern hemisphere and the Tropic of Capricorn and the Antarctic circle in the Southern Hemisphere.
3. Answer with one of the imaginary lines: axis, Equator, meridian or parallel: