Autumn Equinox Australia 2024 – First Day of Autumn in Southern Hemisphere

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March Equinox marks the arrival of the first day of autumn in southern hemisphere. That’s why in earth’s southern areas, March Equinox is known as autumn Equinox or Fall Equinox. In 2024, the first day of autumn in Australia (southern hemisphere) will occur on Tuesday, March 20 at sharp 02:07 PM Australian Eastern Daylight Time (AEDT).

On the other hand, for the people living in the northern hemisphere, this equinox marks the arrival of the first day of spring in the northern hemisphere. That’s why in the earth’s northern areas, the March equinox is known as the spring or vernal equinox.

In other words, the meaning of equinox changes depending on the fact that at which side of the hemisphere you live upon. Not to mention, regardless of the fact that at which side of the hemisphere you live upon, the length of day and night are almost exactly equal on the eve of Equinox.

Moving ahead, in this exclusive article, we will talk about the fact that why there is a mismatch between the south and north equinoxes. In other words, why the march equinox i.e the first day of autumn in the southern hemisphere is the first day of spring in the northern hemisphere?

Or, the march equinox i.e the first day of fall is actually the official first day of fall or not? Therefore. I would suggest you stick with me till the end. Let’s dive right in!!!

 

What is Equinox?

There are two ways to define the meaning of equinox. These are meteorological and astronomical definitions of Equinox. Right now, I am going to explain it on the basis of astronomy. But that doesn’t mean I won’t be explaining the meteorological definition of equinoxes. We will talk about it in a later section.

So, moving ahead, according to the astronomical definition of the equinox, this is a naturally occurring event during which the center of the sun appears to cross over the celestial equatorial line of the earth. In layman, one can say that an equinox occurs when the sun switches sides from one hemisphere of the earth to the other.

Not to mention, there are two types of equinoxes. Fall equinox, also known as the autumnal equinox marks the first day of autumn. And the Spring Equinox, also known as Vernal equinox marks the first day of spring.

Four Seasons

types-of-seasons-on-earth
Four types of seasons occurs on earth: (above) Winter, Spring, (below) Summer, Autumn/Fall

In case if you don’t know, there are generally four seasons that occur on earth. These are summer, winter, autumn, and spring. Just like the fall and spring equinox is responsible for the arrival of fall and spring seasons on earth.

In a similar way, the winter and summer solstice is responsible for the arrival of winter and summer seasons on earth. To summarise, each year earth experiences 2 solstices (summer and winter) and 2 equinoxes (spring and fall) that help us to understand the patterns related to the changing seasons.

Now, the question arises that why there is a mismatch between the south and north. To put it differently, why when there is a fall equinox in the southern hemisphere, there is a spring equinox in the northern hemisphere? Let’s find out!!!

 

Thanks to Earth’s Tilt, We See Equinoxes

earth's-tilt-reason-for-seasons
Earth’s axial tilt (obliquity) is currently about 23.4°/Credit: Wikimedia Commons

Well, there is a small correction here. Not only see equinoxes because of the earth’s tilt. We see solstices too. Moving ahead, just because the earth has an axial tilt of 23.4 degrees, there is a mismatch between the southern and northern hemispheres.

In fact, Kepler’s law also contributes to the formation of the different seasons across the globe. YES, YES, the same Kepler’s law that states that all the planets in the solar system revolve around the sun in an elliptical orbit.

However, Kepler’s law contribution can’t be compared to the role played by the earth’s tilt. I mean, if I say in terms of approximated ratios. Then it will be like 90:10.

Basis of ComparisionSouthern HemisphereNorthern Hemisphere
March EquinoxIt marks the first day of autumnIt marks the first day of spring.
June SolsticeIt marks the first day of winter.It marks the first day of summer.
September EquinoxIt marks the first day of spring.It marks the first day of fall.
December SolsticeIt marks the first day of summer.It marks the first day of winter.
From the above comparison chart, it is clear that the equinox that occurs in March in the southern hemisphere is the Autumn Equinox. On the other hand, due to the earth’s tilt, the equinox that occurs in March in the northern hemisphere is the Spring Equinox.

 

March Equinox – First Day of Autumn in Southern Hemisphere

first-day-of-autumn-in-australia
An image of the first day of fall i.e autumn in Australia. Image Credit: Australian Broadcasting Corporation

As you already know that an equinox occurs when the center of the sun appears to cross over the celestial equatorial line of the earth. Moreover, you also know that there are two types of Equinox. These are the march equinox and September equinox.

So, how to define March Equinox or even September Equinox? OKAY, let me rephrase my question for you!!! What’s the difference between the March and September Equinox? Any Guess???

Well, the only difference between the march and September equinox is that during the march equinox, the sun switches sides from the southern hemisphere to the northern hemisphere of the earth. That’s why the march equinox is also known as the Northward equinox.

On the other hand, during the September equinox, the sun switches sides from the northern hemisphere to the southern hemisphere of the earth. That’s why the September equinox is also known as the Southward Equinox.

March Equinox – Northward Equinox

earth's-illumination-during-different-season-in-different-hemisphere
Image Credit: Wikimedia Commons

As the sun crosses over the imaginary celestial line from the south to the north direction. The earth’s southern areas start to cool down rapidly. Refer to the above image for a proper understanding.

Hence, marking the end of the summers and the start of autumn in the southern hemisphere. That’s why the march equinox aka northward equinox is officially known as the autumn equinox in the southern hemisphere.

Similarly, as the sun crosses over the imaginary celestial line from the south to the north direction. The earth’s northern areas start to warm up rapidly.

Hence, marking the end of the winter and the arrival of the first day of spring in the northern hemisphere. That’s why the march equinox is officially known as the spring equinox in the northern parts of the earth.

Equal Day and Night

equal-day-and-night-during-first-day-of-fall-or-spring
Illumination of Earth by the Sun on the day of the equinox (fall or spring). Image Credit: Wikimedia Commons

Yup, you heard me right. We have equal day and night during the march equinox (also during the September equinox). WHY? Because when the sun crosses over the imaginary celestial line, the earth’s tilt becomes perpendicular to the sunshine. Or, you can say that on the eve of an equinox, the earth’s axis is neither tilted toward nor away from the sun.

Hence, daylight and nighttime hours are equal. In other words, we will have equal day and night i.e 12 hours. Don’t think that the earth’s axial tilt will become Zero during the equinoxes. In fact, it just happens because of the sun’s passing over the Equatorial line.

Moving ahead, in the light of equal day and night phenomena, I just want to clarify that it’s not exactly equal. It’s nearly equal to 12 hours. Therefore, just for approximation, we simply say that during the Spring and Autumn Equinox, the length of day and night becomes equal.

Shorter Days Longer Nights

winter-after-first-day-of-autumn
Winter picks up pace after the arrival of fall in the southern hemisphere. Image Credit: Adobe Stock

There are two ways to practically observe the arrival of Autumn in the southern hemisphere. First, you can see the sudden change in the color of the leaves around you. I mean, the way your surroundings will become vibrant, can’t go unnoticed. Second, You can notice that the days are getting shorter and the nights are getting longer.

In other words, after the Fall equinox of 2024, as the sun will start to move northward, days will become shorter and shorter with each passing day. For the people of the southern hemisphere, this process of shorter days and longer nights will go on until the arrival of the June solstice.

Autumn Equinox – First Day of Autumn or Mid-Autumn?

Now is the time we should talk about the meteorological definition of the autumn equinox. Well, technically speaking, if we go by the meteorological definition, it marks the end of half of the fall or autumn season i.e mid-autumn.

However, on the other hand, if we go by the astronomical definition, it marks the arrival of the first day of the fall. Therefore, the question arises that why we have two different definitions for a single event. More importantly, which one of these is the correct one? Let’s find out.

Let’s Go Back in Time

Before the arrival of the scientific revolution, humans didn’t know how to calculate the change in the season in terms of astronomical calculations. WHY? Because they didn’t have the telescope to do such nasty observations.

Therefore, what they used to do is to calculate the change in season as humanly as possible. With time, early humans understood that the sun seems to cross over the horizon after a fixed interval of time. Additionally, they also understood the pattern of the annual temperature cycle.

In other words, what early humans used to do is to calculate the relative things, like what they felt and observed with the naked eye, which is in fact in the modern notation known as the meteorological definition of autumn equinox or simply meteorological autumn.

On the other hand, what our astronomers and scientists calculate with their super-sophisticated technology is defined as the astronomical definition of fall equinox or simply astronomical fall.

Therefore, to conclude, I would say that both definitions are correct in their own sense. Hence, as a result, some people define the fall equinox in the southern hemisphere as the first day of the fall.

On the contrary, some people define it as the end of the half of the fall or autumn season, hence mid-fall. Not to mention, the meteorological seasons always arrive approx 20 days before the arrival of astronomical seasons. To understand it more clearly, refer to the below table.

 

Meteorological vs Astronomical Seasons

SeasonsMeteorological Season DatesAstronimocal Season Dates
Autumn EquinoxFriday, 1 March 2024Tuesday, 20 March 2024
Winter SolsticeSaturday, 1 June 2024Friday, 21 June 2024
Spring EquinoxSunday, 1 September 2024Sunday, 22 September 2024
Summer SolsticeSunday, 1 December 2024Saturday, 21 December 2024
All the seasons (meteorological and astronomical) dates are strictly in accordance with the southern hemisphere of the earth.

 

When is the First Day of Autumn 2024 in Southern Hemisphere?

In 2024, Autumn Equinox in Australia (southern hemisphere) will occur on Tue, March 20, at sharp 02:07 PM AEDT (Australian Eastern Daylight Time). Not to mention, this astronomical event will occur at the same moment for all of us.

I mean, whether you are living in New Zealand or in Australia, or even in Europe (i.e in the northern hemisphere), it would be a moment of joy for all of us at the same instant.

Well, yeah, for European people, it will be the spring equinox. I hope you know the exact reason behind it.

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I am a mechanical engineer by profession. Just because of my love for fundamental physics, I switched my career, and therefore I did my postgraduate degree in physics. Right now I am a loner (as ever) and a Physics blogger too. My sole future goal is to do a Ph.D. in theoretical physics, especially in the field of cosmology. Because in my view, every aspect of physics comes within the range of cosmology. And I love traveling, especially the Sole one.

10 thoughts on “Autumn Equinox Australia 2024 – First Day of Autumn in Southern Hemisphere”

    • Hey John,
      Well, in my view, both are the same. However, as you have mentioned, I would definitely love to do some tweaks and changes as per your wish. Keep visiting us!

      Reply
  1. Just a Fyi, Australia does not mark there season changes at equinox’s, as we tend to have an ocean moderated climate, we change seasons at the start of the month, ie, the first day of Autumn is the 1st of March, not the 21st

    Reply
  2. Cool description. I’m in Australia. I arrived at this page because I have a “resonance” with Autumn that I cannot explain in any other way so I am turning to Physics for clues. As I wait for the Liquidambar trees to turn their leaves red, orange, and yellow – the colours of the first 3 energy centres/chakras.

    Reply
    • Yeah, that’s because Aussies follow the meteorological definition for the start of autumn or any other season, not the astronomical definition, for instance, as per the meteorological definition, autumn in Australia starts from the 1st of March, not from the 22nd of March.

      Reply
      • Most Aussies don’t have a clue about equinoxes, in case you haven’t noticed. Australia doesn’t observe, acknowledge, celebrate or hold rituals for this event. Try talking to the average Aussie about the seasons, it’s enough to make you wish you were never born.

        Reply
  3. Fantastic article Atul! Very insightful. I’m a fan of physics and astronomy too! Autumn is the best time of year for me here in Australia, as it finally starts to cool down and the nights get longer. Thank you for this article. 🙂

    Reply

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