Equinox
“Equinox” means “equal night” in Latin. But even if the name suggests it and it’s widely accepted, it isn’t entirely true that day and night are exactly the same on the equinox all over the world – only nearly.
In late March and late September both hemispheres are the same distance from the Sun and the Sun is said to be at an equinox. The Northern Hemisphere’s vernal equinox usually occurs on March 20 or 21 and marks the beginning of spring. The Northern Hemisphere’s autumnal equinox usually occurs on September 22 or 23 and marks the beginning of autumn.
In the Southern Hemisphere, the vernal equinox occurs in September and the autumnal equinox occurs in March. At the equinoxes, the Sun appears to be directly over Earth’s equator. The lengths of day and night are then equal over almost all Earth, except at the poles. At the North Pole and South Pole, Earth’s atmosphere bends the Sun’s rays enough to make the Sun visible throughout the day and night, even during the 12 hours the Sun is below the horizon.
The changes in temperature and in the length of daylight that accompany the seasons differ greatly at different latitudes. At the poles, summer is three months of daylight and winter is three months of darkness. Near the equator, however, days and nights remain about 12 hours long throughout the year. The Arctic and Antarctic circles, at latitude 66°30’ north and 66°30’ south respectively, mark the farthest points from the poles at which there can be 24 hours of daylight or 24 hours of darkness. Midway between the poles and the equator, the length of daylight varies from about 8 hours in winter to about 16 hours in summer.
The Length of day and Temperature
The changes in temperature and in the length of daylight that accompany the seasons differ greatly at different latitudes. At the poles, summer is three months of daylight and winter is three months of darkness. Near the equator, however, days and nights remain about 12 hours long throughout the year. The Arctic and Antarctic circles, at latitude 66°30’ north and 66°30’ south respectively, mark the farthest points from the poles at which there can be 24 hours of daylight or 24 hours of darkness. Midway between the poles and the equator, the length of daylight varies from about 8 hours in winter to about 16 hours in summer.
Difference between Rotation of Earth and Revolution of Earth
Rotation | Revolution |
Rotation means “to spin.” This is the cause of day and night. Earth rotates on its axis (an imaginary line running through the center of the Earth from the North Pole to the South Pole) | Revolution means “to go around something.” This is the cause of four seasons. A synonym for revolution is orbit. (revolution = orbit) |
The Earth rotates counterclockwise | The Earth revolves (goes around) the sun counterclockwise. |
Earth completes 1 rotation (spin) every 24 hours.. | It takes Earth 365 days (or 1 year) to make one complete revolution around the sun. |
Day and night are caused by Earth’s rotation (spin) on its axis. When ½ of the Earth is facing the sun it is DAY. When ½ of the Earth is facing away from the sun it is NIGHT. | Earth’s seasons are caused by 1) Earth’s titled axis and 2) Earth’s revolution (orbit) around the sun. When the Northern Hemisphere is tilted toward the sun we have summer. When the Northern Hemisphere is titled away from the sun we have winter. |
In brief: The basic difference between the two movements is the nature of the movement. The rotation means to circle around one’s own axis while the revolution means to circle around any other object. The second difference is the velocity of the objects. The velocity of the object which rotates can be different from the object that revolves. The revolution and rotation co-exist in space while they can also be seen differently. Their co-existence is the reason why we see our earth as stationary object. The rotation is the movement that covers lower distance than revolution. For example, earth completes its rotation in almost 30 days, while the same earth completes its revolution in 365 days.
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