Why are there seasons on our planet?

The ancient Greeks used to have their lore. Persephone, the daughter of Zeus and Demeter was abducted by Hades, the lord of the underworld. When Zeus consented to Persephone being married to Hades; Hades made a concession to allow her to visit her mother for 8 out of the 12 months in a year. This is why we have Spring, Summer and as the time for Persephone to leave comes closer, Summer gives way to autumn. During the 4 months when Persephone is away, Demeter becomes very sad. Demeter being the goddess of fertility robs the earth of its fertility and so the winters are cold.

This is an oversimplification of the story. I did not want to write 4 pages.

If any Greek had even visited Australia, the question of why is it summer in Australia when it is Winter in Greece might have come up. But that was not to be.

It is human to try to find a way to explain all the things that go on around us. This is part of the reason Economics is even an area of study. Truth be told, economics is about the psychological relationship between people and money. Whoever thought it might be possible to translate human psychology into a set of equations. But we NEED to explain.

If the Greeks had come across Australia, they would have probably created an exception to the rule. 

The earth is tilted on its axis and this axial tilt is what causes seasons. It also causes days to be longer in the summers closer to the poles and nights in winter. 

Every axiom, every rule, every law that you have ever been taught which has a corresponding exception is probably a poor explanation. It is there because we do not know the actual explanation. It is a placeholder in the interim so that it does not drive us crazy.

A good explanation does not require exceptions. It often ends up explaining other things that you were not even seeking to explain.