What Is the Spring Equinox? Meaning, Science, and Traditions

What Is the Spring Equinox?

The spring equinox, also known as the vernal equinox, marks one of the two moments each year when the Earth’s axis is tilted neither toward nor away from the sun. This astronomical event signals the official beginning of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. On this day, the sun shines directly over the equator, resulting in nearly equal amounts of daylight and darkness across the globe.
Both nature lovers and astronomy enthusiasts look forward to this day, which is steeped in scientific wonder and global cultural traditions.

When Is the Spring Equinox in 2025?

In 2025, the spring equinox occurs on Thursday, March 20th. At exactly 9:01 UTC (which is 5:01 a.m. EDT), the sun crosses the celestial equator, marking this astronomical milestone. The precise timing can vary slightly from year to year, but it always happens around March 19–21 for the Northern Hemisphere.

What Does ‘Equinox’ Mean?

The word equinox comes from the Latin words aequus (meaning “equal”) and nox (meaning “night”). Traditionally, it was believed that on the equinox, everyone on Earth experienced roughly equal hours of daylight and darkness.
While this is nearly true, due to atmospheric refraction and the definition of sunrise and sunset, the periods aren’t exactly equal. Nevertheless, the spring equinox is still the day of the year that most closely matches this balance.

The Science Behind the Spring Equinox

• Earth’s Tilt and Orbit: The Earth is tilted at about 23.5 degrees on its axis. As our planet travels around the sun, this tilt causes varying amounts of sunlight to reach different regions, giving rise to the seasons.
• Sun’s Path: During the equinox, the sun is positioned directly above the equator—the only two days a year where this happens. As a result, the sun rises precisely due east and sets due west for most locations.
• Start of Astronomical Spring: The spring equinox is considered the astronomical start of spring. Meteorological spring, meanwhile, begins on March 1st, based on temperature cycles rather than the sun’s position.

This interplay of tilt and orbit means that after the spring equinox, the days in the Northern Hemisphere grow longer and warmer, while those in the Southern Hemisphere experience shorter days as they move toward winter.

What Happens On the Equinox?

• Equal Day and Night: Both hemispheres receive nearly equal amounts of sunlight, creating a striking balance of day and night.
• Changing Sunlight: After the equinox, the Northern Hemisphere begins to tilt more toward the sun, lengthening days and ushering in warmer weather. The Southern Hemisphere, conversely, receives less direct sunlight, heading into fall.
• Celestial Markers: Astronomers use the vernal equinox as a reference point for celestial coordinates, marking the sun’s apparent journey along the ecliptic.

While many imagine an instant switch, the transition is gradual. The warmth of spring often lags behind the equinox itself, as land and water take time to absorb the sun’s growing energy.

Why Isn’t Day and Night Exactly Equal?

While the term ‘equinox’ suggests perfect equality between day and night, a few factors cause a slight imbalance:

• Atmospheric Refraction: Earth’s atmosphere bends sunlight, allowing us to see the sun before it actually rises and after it sets. This extends daylight by a few extra minutes.
• Sun as a Disk: We define sunrise as the moment the sun’s upper edge appears over the horizon, not its center—also adding extra daylight minutes.

Therefore, on the equinox, most places actually experience a few more minutes of daylight than darkness. The true “equal day and night” event is known as the equilux, which usually happens a few days before the equinox in spring and a few days after in autumn.

The Equinox and the Seasons: Why Do We Have Seasons?

• Earth’s Axis Tilt: The Earth’s 23.5-degree tilt is the main reason we have seasons. As the Earth orbits the sun, the angle at which sunlight strikes different parts of the planet changes.
• Seasonal Shifts: When the Northern Hemisphere tilts toward the sun, we experience spring and summer; when it tilts away, we have autumn and winter.
• Global Perspective: As the Northern Hemisphere welcomes spring, the Southern Hemisphere enters autumn, and vice versa in September.

These regular changes are crucial for life on Earth, affecting everything from plant growth and animal behavior to human traditions and agriculture.

How Is the Spring Equinox Celebrated Around the World?

Across cultures, the arrival of the spring equinox is a time for joyful celebrations and ancient rituals. The transition from winter to spring symbolizes renewal, fertility, and hope. Here are a few ways the equinox is honored globally:

• Nowruz: The Persian New Year, Nowruz, has been celebrated on the spring equinox for over 3,000 years in Iran and much of Central Asia. Families gather for feasts, music, and symbolic cleaning and renewal tasks.
• Easter: Christianity’s Easter holiday is set in relation to the equinox, falling on the first Sunday after the first full moon following the vernal equinox.
• Holi: In India, the Hindu festival of Holi celebrates the arrival of spring with vibrant colors, songs, and water fights.
• Egg Balancing: A popular myth claims you can balance an egg upright on the equinox thanks to special gravitational forces. While fun, this phenomenon can actually be done any day of the year!
• Stonehenge Gatherings: In England, people flock to Stonehenge to watch the sunrise on the equinox, a tradition rooted in ancient astronomy.

Interesting Facts and Myths About the Spring Equinox

• The Equinox Does Not Always Fall on the Same Date: While March 20th or 21st is most common, the exact date can shift due to leap years and subtle irregularities in the Earth’s orbit.
• Spring Starts at Different Times in Different Cultures: Meteorological spring starts March 1st, while the astronomical spring (marked by the equinox) is in late March.
• Ancient Monuments Aligned to the Equinox: Many ancient structures, such as Mexico’s El Castillo at Chichen Itza, are oriented to highlight the sun or cast specific shadows on the equinox.

Spring Equinox vs. Autumn Equinox

How to Celebrate the Spring Equinox

• Enjoy Nature: Go for a walk, observe budding trees and blooming flowers, or listen for returning birds.
• Start a Garden: The equinox is a traditional time to plant seeds, both literally and symbolically.
• Spring Cleaning: Many cultures associate the equinox with a thorough cleaning, making space for new growth.
• Personal Rituals: Write down your goals for the season, make art inspired by new beginnings, or simply spend time with family.

Frequently Asked Questions (FAQs)

Q: Are day and night exactly equal on the equinox?

A: Not quite. Because of atmospheric refraction and how we define sunrise and sunset, most places experience a few extra minutes of daylight. True equality, called the equilux, happens a few days before or after the equinox.

Q: Does the spring equinox always fall on the same date?

A: No. While it traditionally falls on March 20th or 21st, the exact date can vary slightly from year to year because of leap years and quirks in our calendar system.

Q: Can you really balance an egg on its end during the equinox?

A: While this is a fun myth, you can actually balance an egg on its end any day of the year with patience and a steady hand—the equinox does not create special gravitational forces.

Q: What’s the difference between the astronomical and meteorological start of spring?

A: The astronomical start of spring is marked by the equinox (around March 20th), while meteorological spring is based on temperature patterns and starts on March 1st.

Q: Is the equinox celebrated globally?

A: Absolutely! Many cultures have special traditions, holidays, or rituals tied to the spring equinox, including Nowruz, Holi, and even gathering at ancient monuments.

Conclusion

The spring equinox is more than an astronomical event—it’s a global celebration of new beginnings and the promise of warmer, brighter days ahead. Whether you’re marveling at the science or participating in cultural festivities, the equinox reminds us each year of Earth’s remarkable journey around the sun and our connection to nature’s cycles.

Author

Shinta

 

Shinta is a biotechnologist turned writer. She holds a master's degree in Biotechnology from Karunya Institute of Technology and Sciences and a PG Diploma in cellular and molecular diagnostics from Manipal University. Shinta realised her love for content while working as an editor for a scientific journal.

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