The Sun and the Seasons

The seasons are governed by the tilt of the Earth’s axis in space as it journeys around the Sun in a year. When the South Pole of the Earth is tilted towards the Sun, this is our Summer. Six months later, when the South Pole is tilted away from the Sun, it's our Winter. In between these we have Autumn and Spring.

The sun and the seasons

Temperatures on our planet are not determined by the distance of the Earth from the Sun. Rather it is the angle of the Sun’s rays striking the Earth. In Summer, the Sun is high in the Sky and the rays hit the Earth at a steep angle. In winter, the Sun is low in the Sky and the rays strike the Earth at a shallow angle.

The seasons don’t begin on one day and finish on another. That's because our orbit around the Sun is continuous. It actually takes quite some time for the Earth to heat up or cool down, and that’s why the seasons change gradually.

So when do we actually start the seasons?

In some parts of the world, such as Australia, seasons begin on the first day of a particular calendar month - in March for Autumn, June for Winter, September for Spring and December for Summer. In other countries such as Britain, it’s accepted that the seasons begin on the dates that the Earth passes four special points in its orbit about the Sun.

Spring Equinox (AEST)

2008 September 23, 1:44am
2009 September 23, 7:18am
2010 September 23, 1:09pm

The Sun in spring

The Sun in spring
Artist: Frey Micklethwait. Source: Museum Victoria.

On the day of the Spring Equinox, the Earth’s poles are the same distance from the Sun. In Melbourne, the Sun rises due east, sets due west and gets to 52° above the horizon at noon. On this day there are roughly 12 hrs of day and 12 hrs of night.

Summer Solstice (AEDT)

2008 December 21, 11:04pm
2009 December 22, 4:47am
2010 December 22, 10:38am

The Sun in summer

The Sun in summer
Artist: Frey Micklethwait. Source: Museum Victoria.

On the day of Summer Solstice, the Earth’s south pole is tilted towards the Sun. The Sun rises south of east, sets south of west and reaches 751/2° above the horizon at noon. This is, usually, the longest day of the year.

Autumn Equinox (AEST)

2008 March 20, 3:48pm
2009 March 20, 9:44pm
2010 March 21, 3:32am

The Sun in autumn

The Sun in autumn
Artist: Frey Micklethwait. Source: Museum Victoria

On the day of the Autumn Equinox, the Earth’s poles are the same distance from the Sun. The Sun rises due east, sets due west and reaches 52° above the horizon at noon. There are roughly 12 hrs of day and 12 hrs of night.

Winter Solstice (AEST)

2008 June 21, 9:59am
2009 June 21, 3:45pm
2010 June 21, 9:28pm

The Sun in Winter

The Sun in Winter
Artist: Frey Micklethwait. Source: Museum Victoria.

On the day of Winter Solstice, Earth’s south pole is tilted away from the Sun. The Sun rises north of east, sets north of west and reaches 281/2° above the horizon at noon. This is, usually, the shortest day of the year.

Your comments

fnord k 21 Mar 2009 08:52 AM
thanks, this is super useful information
Mara Ripani 03 Apr 2009 11:33 AM
Exccelent I needed this info for my garden , right going out to my garden right now to plant garlic as your site has made it clear that the Autumn Equinox was on the 20th of march!! so better get those garlics in the ground immidiately, thankyouoooo!, mara
Scotty 16 Apr 2009 17:42 PM
Thanks. Excellent site. One of the few sites that actually understand what a solstice is.
Kristina 19 Apr 2009 00:38 AM
You've peak my interest when you say 'usually' the longest or shortest day. When is the the solstice not the longest or shortest day? Thanks.
Alex 21 Apr 2009 21:53 PM
thanks a lot, helped me understand what a solstice is
Discovery Centre 23 Apr 2009 15:55 PM
Museum Victoria
Kristina - information that will answer your query can be found in the March edition of Melbourne Planetarium's Skynotes.
Anna 03 Jun 2009 23:12 PM
Awesome! one of the few detailed sites about seasons in Australia.. going to bookmark this one. Thanks
Lizzy P 22 Jun 2009 13:50 PM
great explanation, thanks for making solstices, equinoxes and seasons so easy to understand....
Terry Lord 22 Jun 2009 15:01 PM
Thank you, brilliant,so easy to understand. I will bookmark this one too.I have my garden prepared now I'll know exactly when to plant.
marie 24 Jun 2009 07:38 AM
This site is brilliant, easy to understand, informative. In all of my years learning about our planet, no teacher could EVER explain the Equinox and the Solstice so clearly. Good on everyone who has worked hard to make it such a success. This site is now 'offically' bookmarked! Fantastic work.
Leigh 11 Jul 2009 18:22 PM
When is the shortest day in Victoria Australia thanks Leigh
Zahra 26 Jul 2009 13:38 PM
It was a significant information for me and reply ro my answer. so thank you very much.
Discovery Centre 30 Jul 2009 15:05 PM
Museum Victoria

Leigh: the shortest day in the year is the Winter Solstice whose dates are mentioned in this info-sheet. Further details about the sun's movements can be found over at this sheet, too.

Chris Lockyer 01 Aug 2009 19:24 PM
Thanks for your Equinox explanations . This solved a disagreement I had with a friend about when true spring started.
Edward Buinowicz 20 Sep 2009 23:08 PM
A Very Excellent page that describes in a easy-to-understand manner. I have searched many other sites for this info and this is "tops".
Wizardo 24 Sep 2009 03:35 AM
Thank you for making something so complex, seem so simple. Being aware of the dates now give reason to, the slow start to summer and the long winter!
susie-jane 24 Sep 2009 10:28 AM
Hi I have a friend in USA who is a pagan priestess and is coming to australia in December for solstice conference do you have a contact or know of an expert in the solstice field in Australia? thanks for your help
Discovery Centre 25 Sep 2009 10:26 AM
Museum Victoria

The Discovery Centre can answer questions that relate to Museum Victoria's Collection and Research areas, including Science. If you have specific questions relating to astronomy and meteorology, such as the solstice, you can ask one of our experts on staff by contacting the Discovery Centre directly.

stephen Robards 20 Dec 2009 13:05 PM
What is the time difference between Melbourne and Wollongong for the Summer Solstice. You note that it is 4.47am is this same time for both locations?
Discovery Centre 22 Dec 2009 13:42 PM
Museum Victoria

An edited version of our Planetarium staff's response to Stephen's question is as follows:

The Summer Solstice is today the 22nd Dec at 04:47 Australian Easter Summer Time, or if you look at international sites you will see it listed as being on the 21st Dec. at Universal Time 17:47. 

 

The actual time difference between Wollongong and Melbourne is immaterial.  It is based on the precise time that the angle of the Earth’s tilt is most inclined toward or away from the Sun.

 

Marilyn 01 Jan 2010 14:00 PM
Excellent site. Easy to understand and great diagrams to help explain.
barry 13 Mar 2010 12:13 PM
the equinox controls many of the life style habbits of wild animals such as the mating season for wild red deer which is the start of the deer hunting season
Annette 21 Mar 2010 15:28 PM
So glad to have stumbled upon this excellent site!!!
Felicity 25 Mar 2010 09:42 AM
Excellent Website. I will visit again :-) It answered my questions on Equinox :-)
Darlyn Watts 27 Mar 2010 17:13 PM
We had a solar system installed, and I was trying to explain to my husband about how the sun is lower in winter... Thanks for the very helpful website, you explained it beautifully.
Chris 26 Apr 2010 23:28 PM
Hi, I like to know if there's anyway I can take a compass reading of a building's facing direction using the reference of the sun (to detect a true south direction)? I have problem taking accurate compass reading due to interference of magnetic field from man-made magnetic field (like underground wiring and light pole etc). Hope you can help. Thanks.
Discovery Centre 29 Apr 2010 11:12 AM

Compasses indicate magnetic north or south as they react to the Earth’s magnetic field but that’s offset with respect to our planet’s rotational axis (what most call geographic or true north/south). The direction of magnetic north or south is therefore slightly different. It's possible to find south using the position of the Sun in the sky but it's hard to be really accurate. A reasonable result can be got by observing the motion of the Sun across the sky. Wait for local noon by using a clock on standard time (simpler than having to allow an hour for daylight savings). At that time the Sun will be at its highest point above the horizon, so face the Sun and south will be behind you if you are in the Southern Hemisphere (or north will be behind you if in the Northern Hemisphere). Better still, use a sundial or a tall pole that will throw a shadow towards south at local noon (or towards north if in the Northern Hemisphere). You can then compare compass readings at the building and some well away from it with your noon observing of the Sun. Overall you should get a pretty good facing direction. These websites will give more information:

http://www-istp.gsfc.nasa.gov/stargaze/Snavigat.htm

http://www.wilderness-survival-skills.com/learn-celestial-navigation.html

http://hiker.com/navigation-by-the-stars-and-sun/  

Ted 03 May 2010 18:35 PM
Bring on 21 june as I dislike winter and the short days it brings with it
Gary Rowan Higgins 18 May 2010 12:40 PM
A wonderfully educational site. But let's hurry up and get 21st June out of the way. Bushwalking in Tassie is no fun when it's dark at 4pm!
C Hollingworth 27 May 2010 16:40 PM
Thankyou for providing such detailed and informative information!
Pam Sewell 14 Jun 2010 13:15 PM
Great website now I understand more about Solstice and Equinox can't wait for June 21 and longer days.
Danny Woods 21 Jun 2010 08:44 AM
Great site easy to use and understand
Louis Milkovits 21 Jun 2010 14:07 PM
Good site. Easy to understand. Thanks
Geoff Stewart 21 Jun 2010 15:18 PM
Great site, good clear explanations and diagrams. Thank you Museum Victoria !
John Larson 21 Jun 2010 16:12 PM
This is rather a stupid and uninformed question but I will ask it anyway - "In plain language without the scientific stuff please, what is the difference between the terms "solstice" and"equinox" - obviously, they don't mean the same thing so what essentially is the main difference.
Rob 22 Jun 2010 09:22 AM
Excellent description. Why do the times/dates for soltices and equinoxes vary a bit from year to year?
Discovery Centre 22 Jun 2010 11:55 AM
Museum Victoria

Hi John - The equinoxes occur when the Sun is right across the celestial equator, and so day and night are of the same length for all observers on Earth. The equinoxes happen in March and September. In June and December are the solstices, when the Sun reaches its northernmost (in June), or southernmost (in December) point in the sky, and appears to stop (in its north-south movement) before reversing and heading back in the other direction.

Vanessa 23 Jun 2010 07:41 AM
Thank you very much for nice concise information. I came to find the date of the winter solstices but was enlightened by the explanation of the difference between that and the equinox. I probably should have already know that but now I do and it’s thanks to this site
Discovery Centre 23 Jun 2010 11:52 AM
Museum Victoria

The date and time of the equinoxes and solstices change slightly because the Earth's orbit around the Sun is not precisely 1 year. The equinoxes and solstices happen when the Earth reaches a precise point in its orbit around the Sun. 

 

However the beginning of the year does not happen at the exact same point every year. We count years as being either 365 or 366 days long, but the orbit actually takes about 365.242 days to go from one March equinox to the next.

 

Thus in a non-leap year, the equinox will be about 0.242 days (approximately 5 hours 50 minutes) later than the previous equinox, while in a leap-year it will be 0.758 days (18 hours 10 minutes) earlier. Note that these figures aren't exact, and the combined effects of gravity from the Moon, the Sun and the other planets also cause a few minutes variation from year to year.

Portia 24 Jun 2010 12:33 PM
Excellent site, good explanation.Thanks for the information.
Richard Heagney 24 Jun 2010 16:30 PM
So if there was no tilt in the earth's poles, there would be no seasons?
Nice to be right for a change!! 25 Jun 2010 22:13 PM
Thank you for saving my marriage and answering when the shortest day of the year is. I knew l was right he knew he was.... and as it happens l was.
Discovery Centre 27 Jun 2010 11:45 AM
Museum Victoria

Hi Richard,

That's correct - if the Earth's axis was not tilted, we would not experience the seasons as we understand them, since the Sun's rays would not be striking the surface of the Earth at such steep angles. If the Earth was not tilted, the Sun's rays would strike the Earth at a uniform angle.

Paul Weaver (Fremantle) 06 Jul 2010 09:04 AM
Yesterday I was reading my original 1829 bound edition of 'The Mirror.' On page 368 was the following assurance: “The tip of the cat’s nose is always cold, except on the day of the (northern) sumer solstice, when it becomes lukewarm.” I’ve put an automated reminder on my computer to check our two moggies’ proboscises at mid-morning next 22 December.
Linda Schenckel 09 Jul 2010 09:39 AM
Thanks for the info. I say boo to June 21, we've hardly had a cold day here yet, I've only got to wear my new boots once!! Great site thanks for all the useful information. I will check my cats nose on December 22 as well, although living in mid Qld its likley to be hot anyway near Christmas.
felicity 23 Jul 2010 21:10 PM
Can you tell me what people who live north of the tropic of capricorn but south of the equator experience. I have been told they experience 2 equinoxes and 2 solstices each time not one. Is this correct or fallacious?
Discovery Centre 28 Jul 2010 13:43 PM
Museum Victoria

Hi Felicity - It is not true that there are two summer solstices at these locations. The summer solstice happens at a specific point in the Earth’s orbit. What is true is that the Sun will appear directly overhead twice a year in these locations. However this is not on the day of the summer solstice. On this day  the day length is longest, and the Sun appears the most southerly, and this will only happen once each year no matter where you are.

Linda 21 Aug 2010 13:43 PM
Great information thanks. I have one question though, I was told that the equinox also relates to wind, and that typically Victoria is at it's windiest in August & September. can you please advise if this is true, and, if so, why.
dorje jankos 30 Aug 2010 10:34 AM
very interresting study

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