Earth has seasons because?

Because the earth is tilted on a axis and tilts differently to get the 4 different seasons

Different parts of Earth get the Sun’s direct rays as we travel through the year. Different Continents don't have the same seasons as us because the sun is not shining its direct rays on us during different times of the year. 
Hope this helps:)

Ascenario that doesnt  include any modern objects like electricity

Ansradar; im guessing here; good luck : )