The solstices and equinoxes are determined by the position of the Earth in its orbit around the Sun. They occur because the Earth’s spin axis is at a 23.5 degree angle to the plane on which it orbits around the Sun. This is the reason which causes seasons on our planet, Earth. Across the year, at some time, days are longer and nights are shorter or vice versa. Similarly, at some time, there is more heat and light from sun than other days, all these effects are a gift from the tilt of the earth, to which we further named as equinox and solstice. In this article, we will learn about the difference between equinox and solstice.
What is solstice?
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 23.5 degrees relative to Earth’s orbit around the sun. Solstice refers to a day that is either the longest or the shortest. The two solstices in a year are on December 22 (Winter Solstice) and June 21 (summer solstice).
Why length of day and night varies in the world?
Because the earth orbits the sun in an elliptical path, sunlight reaches the earth’s surface at various angles due to its tilted axis. This is why the lengths of days and nights differ and are not the same everywhere in the world. As the Earth rotates, half of the globe receives sunlight while the other is shrouded in darkness. However, because the Earth’s axis is tilted 23.5 degrees from vertical, one hemisphere receives more light than the other and thus has a longer day. Twice a year, when the tilt is most extreme in relation to the sun, one hemisphere has the longest day of the year, while the other has the longest night, which is known as the solstice.
What is 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.
Around the summer solstice in the Northern Hemisphere, parts of the Arctic Circle at the top of the Northern Hemisphere receive 24 hours of sunlight, whereas areas in the Antarctic, at the tip of the Southern Hemisphere, receive no sunlight at all. During the Northern Hemisphere’s winter solstice, the opposite is true.
What is 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.
What is equinox?
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. The term equinox refers to a day with equal lengths of day and night. In a year, there are two equinoxes on March 20 (vernal equinox) and September 22 (autumnal equinox). Twice a year, the lengths of day and night are roughly equal in both the Southern and Northern Hemispheres. This phenomenon is known as an equinox, which is derived from the Latin words “aequus” (meaning equal) and “nox” (meaning night). The Earth orbits the sun with a tilt of approximately 23.5 degrees. This means that depending on our planet’s position in its orbit, different parts of our planet receive more or less of the sun’s radiation at different times of the year.
However, our planet’s tilt aligns with its orbit around the sun twice a year — in March and September — and Earth does not appear to tilt with respect to the sun, according to the National Oceanic and Atmospheric Association. The sun is directly above the equator at this time of year, and both hemispheres have the same number of hours of daylight and night. At these times, the terminator bisects the Earth and runs through the north and south poles. According to EarthSky, day and night are not exactly equal during an equinox, though they are very close.
During an equinox, Earth receives a few minutes more of light than darkness. This is due to the fact that sunrise occurs when the tip of the sun edges over the horizon, whereas sunset occurs when the other edge of the sun disappears beneath the skyline. Because the sun is a disk rather than a point source of light, Earth experiences only a few minutes of additional light (rather than darkness) during an equinox. Furthermore, the atmosphere refracts the sun’s light, causing it to travel to “nighttime” Earth for a brief period of time after the sun has set below the horizon.
Equinox vs solstice
Although both solstice and equinox occur twice in a year, there are a few distinctions between them, given below:
- The equinox occurs when daylight and nighttime are roughly the same length, while the solstice occurs on the longest and shortest days.
- Equinox occurs in spring and autumn while summer and winter seasons are marked by the solstice.
- During equinox, the plane of the Earth’s equator intersects the center of the sun’s disc. While during solstice, the sun reaches its highest or lowest point at noon, which makes the longest and shortest days of the year.
- Equinox is a period of year when sun is nearest to equatorial plate, giving equal days and night. While during solstice, sun is farthest from the equatorial plate, causing varying length of days and nights.
There were a few distinctions between solstice and equinox. While the solstices change the length of the day and night, the equinoxes do not. The summer and winter solstices produce the longest and shortest days of the year, respectively, whereas the equinoxes produce an equal amount of daylight and darkness all over the world.