All of you must be familiar with the term “seasons” that is defined as the times that have particular weather patterns and hours of daylight. Our planet earth has four seasons that are spring, summer, fall and winter. Basically these seasons occur due to the changing positions of earth, as it moves around the sun. Moreover, in December and January, earth is closer to sun but in July and august, earth is farther away. So let’s understand that what physics is going on behind all this and what is solstice?
Earth travels around the sun in an orbit, due to the gravitational pull of the sun. Interestingly, earth makes an angle of 23.5 degrees with its own axis according to the orbital plane. So this fact clearly indicates that north and south poles of earth are not straight as earth revolves around sun. These poles are always at an angle with orbital plane.
Moreover, earth spins about its own axis and takes 24 hrs in one full spin. This is the reason behind day and night. Our 1 year is decided by the rotation of earth around sun that is completed in 365.25 days. In summer earth tilts toward the sun (more temperature) but in winter earth tilts away (cold weather).
The concept of four seasons is only for the people that live above or below the Earth’s equator. People that live at the equator do not experience four seasons. This is due to the middle of Earth does not tilt much as Earth rotates on its axis. Definitely, without tilt the angle of Sun is always the same, so the equator receives the same amount of warmth and light year round. The farther you get from the equator, the bigger the difference there is in seasons and sunlight. For example, in Barrow, Alaska, the northernmost city in the United States, they experience 4 months of complete sunlight from May to August and complete darkness from November to January.
Related to seasons, year, day and night there is also an interesting termed that is solstice. It can be either summer solstice or winter solstice. Solstices occur because Earth’s axis of rotation is tilted about 23.4 degrees relative to Earth’s orbit around the sun. Let’s understand interesting facts about these days and the reason that how these events occur, to which we celebrate.
Summer solstice: On 21 June, earth tilts towards the sun on its axis, in North America, to which we name as summer solstice. This is the day when the northern hemisphere of earth has most daylight as compared to all days of year. One this day sun has maximum angle with earth and seems to highest in the sky. As much the sun will be higher, there will be more sunlight and heat that will be received by the planet earth. This is the time, when days are longer and nights are shorter. Based on the tilt of earth, the seasons in northern hemisphere are opposite to that in southern hemisphere. For example if there is winter in northern areas then summer will start in southern portion.
Renewal, development, fertility, the opportunity for a successful harvest, inner and outer abundance, ascension, and the total return of sunlight to the summer solstice have historically been celebrated by humans. Today, with outdoor feasts, music, dancing, and bonfires, people around the world still celebrate the start of summer.
A day of remembrance created to remember and reflect on the conflict in Northern Ireland is the Day of Private Reflection. Healing By Remembering, a cross-community group committed to coping with the legacy of the war, has suggested it. While focusing on the brutality of the past, the occasion tried to look toward a peaceful future. Since 2007, the summer solstice has been held annually on 21 June; it was chosen for this date as the solstice was considered an opportunity to look both forward and back.
Tirgan, is an ancient Iranian festival held annually on Tir 13 in the middle of summer (July 2, 3, or 4). Sprinkling water, dancing, reciting poetry, and serving traditional foods such as spinach soup and shoreward are celebrated. A way for children to celebrate is also the tradition of tying rainbow-colored wrist bands, which are worn for ten days and then thrown into a stream.
Winter solstice: The northern hemisphere tilts farthest away from the sun, around 21 December, to which we term as winter solstice. It happens twice yearly, once in each hemisphere (Northern and Southern). These are the days when least daylight reaches the earth from sun, as compared to the whole year. In these days, sun appears to be lowest in the sky as it has least angle with earth, so we receive less amount of sunlight and heat in these days. This is the time in year when nights are longer and days are shorter.
The solstice may have an exceptional moment of the annual cycle for some cultures even during neolithic times. Astronomical events are often used to guide activities, such as the mating of animals, the sowing of crops and the monitoring of winter reserves of food. Many cultural mythologies and traditions are derived from this.
Iranian people celebrate the night of Northern Hemisphere’s winter solstice as, “Yalda night”, which is known to be the “longest and darkest night of the year”. Yalda night celebration or “Shabe Chelleh”, is one the oldest Iranian traditions that has been present in Persian culture from the ancient years. In this night all the family gather together, usually at the house of the eldest, and celebrate it by eating, drinking and reciting poetry. Nuts, pomegranates and watermelons are particularly served during this festival.
Germanic people of the northern Europe also celebrate the winter holiday called Yule (also called Jul, Julblot, jólablót).
Equinoxes: 21 march, 21 September and the around time of these dates is the time when earth is angled at 90 degrees. In this time in a year, spring and fall occur. This is the time when both northern and southern hemispheres are exactly at the same angle from sun, so the same heat and light is taken by the whole earth planet.
Over the millenia, ancient cultures have recorded the equinoxes in various ways. Civilizations marked the passage of the sun and the seasons with great precision, from built temples, like pyramids, to stone engravings that served as calendars, to churches that incorporated the sun into their architecture.
Some cultures, including the Lakota Tribe of the U.S., continue to observe the equinox today. By making tobacco from the red willow tree, which matches the Dried Willow constellation, where the sun rises on the spring equinox, the Lakota link the world with the sky. In a celebration marking the return of longer days, they smoke this sacred tobacco. And at the equinox ceremonies in England at Stonehenge, druids, pagans, and anyone else who would like to join in gather to witness the sunrise over the ancient stones.