The vernal equinox (about March 21) marks the beginning of spring by making day and night equal in length. Summer solstice (June 20 or 21): the longest day of the year, signaling the beginning of summer. Autumnal equinox (about September 23): a day and night of equal duration that marks the beginning of fall. Winter solstice (December 22): the shortest day of the year, marking the end of winter and the start of spring.
These three astronomical events are called the solstices because they occur at the time of the sun's highest point in the sky during each season.
The four seasons are divided into two groups, dry and wet, depending on the amount of precipitation they receive. Spring is the season of rebirth and new life; it is when plants grow and flowers bloom. Summer is the season of growth and harvest; it is when crops are harvested before winter arrives. Autumn is the season of change; trees lose their leaves and fruits become ripe for harvesting before winter strikes. Winter is the season of death and renewal; it is when the earth rests after a long summer and animals hibernate before starting over again in the next spring.
Solstices are part of a larger pattern called the annual cycle, which includes seasons, months, days, and hours. The annual cycle is repeated every year, whether we notice it or not. It does this because Earth orbits around the sun.
Winter solstice (December 21 or 22): the year's shortest day, signaling the beginning of winter. Spring equinox (about March 19): a day and night of equal duration that marks the beginning of spring.
The equinoxes are points in time when the earth is standing still with respect to the sun. At both the equinoxes, the plane of Earth's orbit around the sun is perpendicular to the axis of Earth's rotation. For our planet to receive direct sunlight for an entire day, it must be at least as far from the sun as it was at its closest approach, called perihelion. Because of gravitational forces, all objects within Earth's atmosphere will experience weightlessness during these times, and will appear to be hovering above the ground or ocean.
Equinoxes occur when most locations on Earth are experiencing daylight hours and nighttime hours of equal length. The exact times of each equinox vary depending on where you are located on Earth. Locations near the Equator experience approximately six months of daylight and six months of nighttime, while those closer to the poles experience nine months of daylight and three months of darkness.
On the day of an equinox, day and night are about equal in length all throughout the world. The March equinox is known as the vernal or spring equinox in the Northern Hemisphere, whereas the September equinox is known as the autumnal or fall equinox. The term equinox refers to the fact that during this time the angle between Earth's axis and its orbit around the Sun (the ecliptic) is exactly 90 degrees. As a result, at the equinoxes, the sun rises due east and sets due west.
Equinoxes occur when the Earth is at the center of the Universe for astronomers. They can only be visible from certain locations because where you are on Earth affects which parts of the sky are visible. At the equinoxes, both the north pole and south pole are facing up towards the sun so there are no areas of the earth permanently dark nor light at these times.
At other times of the year, the position of the Earth with respect to the sun is not right for us to have equinoxes. In fact, there are two more equinoxes and three more solstices but they don't fit into our calendar system.
The March equinox is when the Northern Hemisphere is in darkness after the winter solstice and before the summer solstice.
The vernal equinox heralds the arrival of spring. The term Equinox is derived from the Latin words aequi (equal) and nox (night). The vernal equinox is regarded as the first day of spring; finally, the lengths of day and night are equal. This event occurs around March 20 or 21 depending on where you are located in the world. Day becomes longer than night, which means that spring has sprung.
Equinoxes can also be called "spring equinoxes" or "fall equinoxes." They occur when the path of the sun is equidistant between the Earth and the moon. Thus, at least one part of our planet is illuminated by sunlight all day long. The other part remains in darkness.
These astronomical events take place approximately every 18 months. The next vernal equinox will happen in 2012. After that, we will have to wait until 2016 to see another one again.
The word "equinox" comes from the Latin aequi meaning "equal" and nox meaning "night." So, the vernal equinox marks the beginning of spring and nighttime lasts about as long as during the fall equinox in September.
According to Roman mythology, Equestria was built by Jupiter who took the form of a horse to build it.