Gizmo

The gizmo showed us how the seasons are caused.  They're caused by the Earth's tilt.  The way that works is that the Earth's axis is a 23.5  degree angle.  That means that as the Earth revolves around the sun, the Northern and Southern hemispheres get get different amounts of sunlight.  The hemisphere that gets the most direct sunlight is in the summer, but the hemisphere that gets the least amount of sun  light is in winter.  That's the way the seasons work.