Difference Between Solstice and Equinox: Have you ever wondered why days are longer in summer and shorter in winter? This happens because of two special astronomical events, the Solstice and the Equinox. Let’s understand the difference between the two and help students learn about the Earth’s movements that affect seasons and daylight.
What is a Solstice?
A solstice is a time when the sun reaches its highest or lowest point in the sky at midday, marked by the longest and shortest days. This occurs twice a year: around June 21 and December 21.
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On June 21, we experience the longest day and shortest night of the year. The term goes by the Summer Solstice.
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On December 21, we experience the shortest day and longest night. It is often called as Winter Solstice.
Fun Fact: During the solstice, either the North Pole or the South Pole is tilted most towards the Sun.
What is an Equinox?
An equinox also happens twice a year, around March 21 and September 23. It is the time when the sun is directly above the equator.
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On March 21 and September 23, the day and night are almost equal in length.
Fun Fact: The word "Equinox" comes from Latin and means “equal night.”
Solstice vs Equinox: What are the Key Differences?
Students can check the key difference to learn the terms easily:
| Feature | Solstice | Equinox |
| Number per year | 2 (June & December) | 2 (March & September) |
| Sun’s position | Farthest from the equator | Directly above the equator |
| Day-Night length | Unequal (longest/shortest day) | Nearly equal day and night |
| Season indicator | Start of summer/winter | Start of spring/autumn |
| Earth's tilt | Maximum tilt towards/away from the Sun | The Sun is aligned with the Earth’s equator |
Why Do Solstices and Equinoxes Happen?
These events occur due to the following reasons:
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Earth is tilted at an angle of 23.5 degrees on its axis, and it revolves around the sun in one year.
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This tilt and orbit lead to different parts of the Earth receiving varying amounts of sunlight.
These celestial markers are believed to have changed the long centuries of culture and folklore. When the winter solstice occurs, it is honoured by festivals worldwide, including Yule in Germanic cultures and Inti Raymi among the Inca. While equinoxes have inspired the celebrations of balance and renewal, the Iranian New Year and Ostara symbolise rebirth. Solstices mark when the Sun’s rays “stand still” before reversing. It comes from the Latin word solstitium. While equinoxes—derived from aequus (“equal”) and nox (“night”), signal days when daylight and nighttime are nearly identical worldwide.
The changing seasons are due to the Solstices and the Equinoxes. These terms are the reasons that affect the length of days and nights. For students, these terms can help them to know about the world of science in a better way.
Other Related Links
Difference Between Northern and Southern Hemispheres
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