What fact can you tell your friend that completely contradicts this view of how the seasons are caused?

You are talking to a friend who insists that the seasons are caused by a varying Earth-Sun distance over the course of a year. What fact can you tell your friend that completely contradicts this view of how the seasons are caused? How would you explain the cause of the seasons to your friend? Why might they have had the initial idea that distance to the sun was the main contribution?