What are the causes of variation in the lengths of day and night?

The variation in the lengths of day and night is caused by two factors: the tilt of the Earth’s axis and its orbit around the Sun.

1. The tilt of the Earth’s axis: The Earth’s axis is tilted at an angle of approximately 23.5 degrees. This tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year, resulting in variations in the lengths of day and night. During the summer solstice, the Northern Hemisphere is tilted towards the Sun, resulting in longer days and shorter nights. Conversely, during the winter solstice, the Northern Hemisphere has tilted away from the Sun, resulting in shorter days and longer nights.
2. The orbit of the Earth around the Sun: The Earth’s orbit around the Sun is not a perfect circle, but rather an ellipse. This means that the distance between the Earth and the Sun varies throughout the year. When the Earth is closest to the Sun (perihelion), it travels faster, causing the day to be slightly shorter than when it is farthest away (aphelion).