The author discusses this issue in order to explain... . the distance between the Earth and the Sun
the way in which the Earth goes around the Sun
why the weather is different in different parts of the Earth
why sun-rays are parallel when they reach the Earth It can be inferred from the passage that... . summer is when the Earth is closest to the Sun
when it is summer in the northern hemisphere it is winter in the southern hemisphere
temperate regions are cooler than equatorial regions as sun-rays travel through more atmosphere to reach them
sun-rays lose heat in passing through space According to the passage the angle at which the sun’s rays strike the surface of the Earth is determined by ... .