Answer:
- The earth is round, meaning the part of it that is closer to the sun, will get more solar energy than the other parts which will get less. (Don't believe me? Just try placing a circle on a flat line, and see if you can get it to evenly touch.)
- The earth is constantly rotating on it's axis, and since its axis is slightly tilted, the two poles will get different amounts of solar energy at different times. While one pole will be closer the other will be farther away, until the earth rotates of course.
- The earth doesn't revolve around the Sun evenly, meaning instead of a perfectly even circle with equal space around the sun, it's more of an elliptical shape, or basically an oval. So this would mean the earth would be slightly further away from the sun as it completes its orbit.
I'm not an expert, nor am I absolutely sure if this is right, but I hope my answer helps.
P.S. Sorry if it's wrong
