Earth’s tilt causes each hemisphere to receive different amounts of

Because the earth is situated on a slight tilt and both increases and decreases its distance from the sun, this alters the amount of light around the globe during certain times of the year. During the winter in the northern hemisphere, the northern hemisphere is facing more upwards creating less sunlight but when the earth reaches its revolution on the other side of the sun, it will be facing downwards which allows more sunlight and warmth during the summer for the northern hemisphere.

Explanation:

81 is a composite number.