Imagine a circle (I know it's more elliptical), but, for ease, imagine a circle......
Now imagine the top half of the circle tilted away from the sun, thus, the bottom half is tilted towards the sun. This allows for one half to be warmer because:
- the bottom of the Earth's surface area getting more rays of sunlight as compared to the top half of the Earth's surface area.
And....this happens because, of the angles (due to tilt in axis). Imagine a vector drawn vertically down the side of the earth (while its tilted as outlined above). This would mean that any perpendicular lines (aka, sun's ray) intercepting that vector, would, strike the bottom half (tilted towards sun) in such a way that the angle between the vertical line and the vector line is closer to a 90 degrees angle, than the flip side**, allowing for more of the Earth's surface to be receptive to the sunlight. I.e., more energy, I.e., season like summer.
** the flip side (the top half) then would be a more acute angle.
|_ versus < allows for the difference, i.e., surface area, not distance travelled by the sunlight. Cuz as MacGuffin mentioned, the earth is actually closest to the sun during the Northern Winter. Meaning, the distance from the sun is actually greater during the summer months, than in the winter months.
So,how is that about distance?