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Summer Solstice - Longest Day of Year, for Northerners

Summer solstice is an event that occurs once an year on each hemisphere of the earth. In Northern Hemisphere, it is tomorrow on 21st June fo...

Summer solstice is an event that occurs once an year on each hemisphere of the earth. In Northern Hemisphere, it is tomorrow on 21st June for the year 2023, and for Southern Hemisphere it will be on 21st December 2023. Yes, the weather pattern is completely opposite on each of the hemisphere, all because of a phenomenon called 'axial tilt' in the rotational axis of our green planet.

Summer Solstice explained in this infographic showing the axial tilt, imaginary lines such as Tropic of Cancer, Capricorn, Equator, etc.

What is Axial Tilt?

Planet Earth as we all know and live in has seasons, and the reason behind this is because of the fact that earth has a tilt (called as 'Axial Tilt', which is at an angle around 23.5°) in its rotational axis (which is around 24 hours, forming a day) and is directly co-related with the revolution around the Sun in its orbit (which is around 365 days, to make an year).

Today, the Earth's axis is tilted 23.5 degrees from the plane of its orbit around the sun. But this tilt changes. During a cycle that averages about 40,000 years, the tilt of the axis varies between 22.1 and 24.5 degrees. Source: NASA

Reasons for Seasons

While revolving around the Sun in its orbit, Earth experiences different degree of sunlight exposure throughout the year, at any given point on its surface all due to axial tilt. As the exposure of sunlight creates difference in temperature throughout the day, it also varies around the year thereby the energy difference creates movement of air as wind, and evaporated water as cloud. Seasons such as summer, winter, autumn/rainy and spring/fall are a result of this one factor of axial tilt, without which there would be no seasons and hence a negative environment for basis of life.

Did you know?

  • 24 hours is the exact length of a day.
  • 365 days is not exactly a length of an year.
  • Axial tilt changes every year on a micro degree.
  • North and South poles flip its orientation over a period of time.
  • Orbital path & plane of the earth around the Sun is not constant and circular.
You might ask why know or bother with all these factors?! Well, climate change. It is not only because of man-made disasters (which cannot be ruled out on its larger and immediate influence), however they change with respect to above known and unknown factors. This is the basis of human knowledge, education and ingenuity to adapt to the changing conditions, weather patterns, etc., of our Solar system in the infinitely vast cosmos it been housed at.

Seasons as Basis for Life

The causes different seasons that makes the planet active, lively and hence life-forming characteristics. This also the very reason life exists on earth, as the planet encounters different seasons favouring different lifeforms that interact differently with various conditions it experiences from differing seasons.

Longest Day for Northern Hemisphere / Tropic of Cancer

The Summer Solstice is the day with the most daylight in the Northern Hemisphere. It occurs when the region of land lying in the imaginary line of Tropic of Cancer is perpendicular to the sunlight received. As there is more time for the sunlight to lit up on this region, it becomes the longest day of the year. In 2023, the Summer Solstice is/was on June 21 (usually around 20-22 of June). There are many parameters that determine the longest lit day, such as year, geo-location, axial tilt, etc., so we assume it as June 21st for ease of understanding for everyone.

Shortest Day for Southern Hemisphere / Tropic of Capricorn

While the majority of the population on the planet enjoys summer and longer daylight in Northern Hemisphere, the Southern Hemisphere region encounters the shortest day and hence winter in regions such as Australia & South America.

The Seasonal Flip

Exactly six months later, on December (21-23), we have Winter Solstice, which is the shortest day as the position of the earth will be on the other side of the orbit around the sun making (Tropic of Capricorn the longest lit, meaning Southern Hemisphere enjoys the most sunlight hence summer there) Tropic of Cancer short exposed making Northern Hemisphere being less lit and the season would be cold/Winter.


While we have one each of the longest & shortest days of the year, we have a double equal day/night days that occurs right in between the Solstices. So basically every three months, we have an event of the sun that is interacting with a certain significance to the daylight and season on our 'living planet' earth.

How & why season occur? Learn quickly here.

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