We hope you’ve made the most of the intense Summer weather, because it is quickly coming to an end. The September Equinox is around the corner, officially marking the start of autumn.
The Equinox marks the exact moment when the Sun passes directly above the Earth’s equator. In other words, this is when the day splits down the middle, giving 12 hours of light and 12 hours of dark.
After this, we slowly edge towards those darker evenings and gloomy morning starts. But it’s not all bad news, especially for those looking to embrace the cosier evenings and autumnal events.
So when exactly does the Equinox occur, and what does it actually mean for you? Read on to find out more.
When is the Autumn Equinox?
Mark your calendars, the Equinox will be occurring on September 23. To be even more exact, 12.06am GMT (1.06am BST).
Unlike most interesting events occurring off in space, there is nothing to see here. Once the date passes, we are simply now into autumn.
What is an Equinox?
The equinox occurs twice a year. The first in March (marking the start of spring) and the second coming up in September, marking autumn.
On these dates, the Sun is crossing over the equater, resulting in nearly equal days and nights. That is where the name ‘equinox’ comes from. In Latin, this means ‘equal night’.
Are the days and nights exactly equal?
If equinox translates to equal night, there should be exactly 12 hours of day and night, right? Well, not exactly. Due to a few factors, the UK actually contains slightly more day than night.
This is a tiny amount of difference but the reason is interesting. Your latitude on Earth will make a difference, making the split seem far more noticeable in one direction.
Equally, the Earth’s atmosphere acts a bit like a lens. Because of this, light is bent slightly towards the denser air near the ground. This means we can see the Sun even when its actual position is slightly below the geometric horizon.
In other words, you will see the Sunrise earlier than it is actually happening and the Sunset happening after it fully sets, extending the experience of day.
When does autumn officially start?
Why just have one clear way of marking the start of autumn when you could have three? The answer will depend on if you go by the astronomical, meteorological or phenological definition.
Astronomical
According to astronomy, there are four seasons that all centre around the equinoxes. For some, the autumn equinox will be the obvious mark for the start of the season, but that isn’t universally agreed.
Meteorological
Meteorologists follow a different believe, splitting the seasons into three periods based on average temperatures. Summer is the warmest period and Winter is the coldest. Using this methodology, autumn months are usually September, October and November.
Phenological
This is the more complicated measure of seasons. These cover a range of factors, including both ecological and biological signs. This includes everything from leaves falling off trees to migration of birds. This can be more confusing, especially with climate change altering these factors over time.
