Inhabitants of the Southern Hemisphere will have their longest day of the year this week, with the summer solstice coming around again.
But while on Friday Australians will receive the most daylight from sunrise to sunset of any 24-hour period this year, the summer solstice isn’t the day with the earliest sunrise or latest sunset.
Here’s more on the science behind the solstice, and when you can expect the earliest and latest sunrise and sunset to occur this summer.
It’s when our side of the world — the Southern Hemisphere — is at its furthest tilt towards the Sun.
As Weatherzone explains, the orientation of Earth relative to the Sun makes the date of the summer solstice the longest day of the year in Australia.
By that, we mean the day with the longest amount of time between sunrise and sunset.
At the same time, Earth’s Northern Hemisphere will be experiencing the winter solstice, due to the North Pole being at its furthest tilt away from the Sun.
These phenomena, along with our general changing of the seasons, occur due to Earth’s 23-degree tilt, which provides different parts of the planet with more sunlight than others as it orbits the Sun.
Put simply, when the summer solstice occurs in the Southern Hemisphere, our side of the Earth is at its closest point to the Sun, while the other side of the Earth will be furthest away.
The summer solstice falls between December 21 and 23 in the Southern Hemisphere each year.
This year, it’s Friday, December 22.
But while we usually think of solstice as referring to a whole day, there’s actually a specific moment when the Southern Hemisphere is at its closest tilt towards the Sun.
This year, that exact moment will be 4:50pm AEST.
People in Sydney are expected to experience about 14 hours and 24 minutes of daylight on Friday, according to timeanddate.com, with the Sun expected to rise at 5:40am and set at 8:05pm on the day of the solstice.
In terms of daylight, this day will be 4 hours and 31 minutes longer in Sydney than the winter solstice.
As Weatherzone notes, our days will start to get shorter than our nights across Australia from this date onwards.
Despite the summer solstice marking the longest stretch of daylight over a 24-hour period, it is not the day when the Sun rises the earliest or sets the latest.
The earliest sunrise and the latest sunset fall about a month apart from each other depending on your location, with the solstice in the middle.
This is due to both the Earth’s tilt and the planet’s elliptical orbit impacting how quickly the planet moves through its orbit when it is closest to the Sun.
While the solstice falls at the same point in time across Australia, the dates of when the earliest sunrise and latest sunset fall vary by location, but more specifically by latitude.
Latitude determines the angle along the horizon at which the Sun travels. This changes faster at higher latitudes closer to the poles.
(ABC)
