Summary
Highlights
The video opens by contrasting the four seasons in countries like the US, Korea, and Japan, with the two seasons (wet and dry) in the Philippines. It poses the question of why different places have different seasons and introduces the Earth's rotation and revolution as the answer.
The Earth moves at a constant speed in a counterclockwise direction in two ways: rotation and revolution. Rotation is the movement of the Earth on its axis, spinning from west to east. While the sun appears to move, it's actually the Earth's rotation that causes the apparent sunrise and sunset, leading to day and night. One complete rotation takes 23 hours, 56 minutes, and 4.2 seconds.
Revolution is the movement of the Earth around the sun in a counterclockwise direction. It takes approximately 365 and one-quarter days for one complete revolution. To account for the extra quarter day, a leap year with 366 days (adding February 29th) occurs every four years. The Earth's orbit is an ellipse, not a perfect circle, resulting in points closest (perihelion) and farthest (aphelion) from the sun.
The Earth's revolution around the sun and its fixed axial tilt of 23 degrees are the primary reasons for the four seasons. This tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year.
During June, July, and August, the Northern Hemisphere faces the sun, experiencing summer (longest daylight), while the Southern Hemisphere experiences winter (shortest daylight). The summer solstice occurs around June 21st or 22nd. Conversely, during December, January, and February, the Northern Hemisphere tilts away from the sun, leading to winter (shortest daylight), and the Southern Hemisphere experiences summer (longest daylight), with the winter solstice around December 21st or 22nd.
In September, October, and November, both hemispheres receive moderate sunlight as the axis is positioned sideways, leading to autumn in the Northern Hemisphere. The autumnal equinox around September 23rd marks equal day and night length. Similarly, from March to May, both hemispheres receive equal solar energy, resulting in spring in the Northern Hemisphere, with the spring equinox around March 21st also signifying equal day and night.
Countries near the equator, such as the Philippines, do not experience the four seasons. Instead, they have two distinct seasons: wet and dry, due to their geographical location.