It's the winter solstice today, so when will mornings get lighter?

Today is the shortest day of the year, but not the earliest sunset or the latest sunrise. (Reuters: Mark Baker)

This year, the winter solstice and the shortest day of the year in the southern hemisphere falls today — June 21.

From tomorrow, we get more minutes of sunlight each day until after the next solstice in December.

But even though the Sun is setting later, the mornings will continue to be dark for a while.

Depending on where you are in Australia, the Sun will continue to rise even later for a couple more weeks and we're likely to see colder weather for several more months.

So what's going on, and when can we expect our mornings to get brighter and warmer?

Our seasons and solstices are caused by the tilt of Earth's axis.

As Earth moves around the Sun each year, the North and South Poles point more towards, or away from, the Sun.

At the moment, the South Pole is pointed away from the Sun. This means locations in the southern hemisphere spend less time each day in sunlight, causing colder and more wintry weather.

The seasons are a function of the Earth's tilt. (ABC: Julie Ramsden)

The northern hemisphere, meanwhile, is pointed towards the Sun, and is heating up in response.

This year, the Sun reaches its most northerly point in the sky on June 21, appearing lower on the horizon in the southern hemisphere.

The closer you are towards the poles, the less sunlight you'll see during the winter solstice.

If Earth's orbit was a perfect circle, we would see our latest sunrises and earliest sunsets on the day of the winter solstice, says Jonti Horner, an astrophysicist at the University of Southern Queensland.

"But there's an extra thing going on," Professor Horner says.

A diagram illustrating the Earth's tilt. (Bureau of Meteorology)

That extra thing is the slightly squished shape of the Earth's orbit. This doesn't decide our seasons — that's a common misconception — but it does have a small influence on sunrise and sunset times.

While Earth rotates at a very constant rate, it travels a slightly different distance and speed in its orbit around the Sun throughout the year.

"The speed we go around the Sun is changing because the Earth's orbit is not perfectly circular, it's actually a little bit elongated," Professor Horner says.

It's a coincidence that Earth reaches its closest and furthest points from the Sun shortly after the solstice. (Wikimedia: Gothika (adapted))

The Earth is furthest from the Sun in early July each year, and closest in early January.

"The further we are from the Sun, the slower we move," Professor Horner says.

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