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) Link copiedShareShare articleThis 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. That means it doesn't always take exactly 24 hours for the Sun to appear directly above our heads at noon — a point known as solar noon — from one day to another. It can take a few seconds more or less depending on how much the Earth has travelled in its orbit that day. This causes a small difference between solar time and our 24-hour clocks so the times that we record sunrise and sunset change very slightly. "That movement is happening separate to the change in the length of the day," Professor Horner explains. "[But] it means the date of the earliest sunset and the date of the latest sunrise are offset," Professor Horner says. In winter, the earliest sunset happens before the solstice, and the latest sunrise happens afterwards. Around the December solstice, the opposite effect occurs, with the earliest sunrises before the solstice and the latest sunsets happening afterwards. The difference between sunset and sunrise times is more noticeable the further north you live. In Darwin, the earliest sunsets and latest sunrises are about three weeks before and after the solstice, while in Hobart, the earliest sunset and latest sunrise occur within a week of the winter solstice. This is because the length of the day changes much more dramatically in the south, which drowns out the small effect of Earth's orbit. "The nearer to the equator you are, the less the length of the day changes," Professor Horner explains. "Therefore, the distance the Sun is ahead or behind will have a bigger impact proportionally on the sunrise and sunset times." While the days get longer from here, we can still expect the temperatures to get colder for the next few months. That's because it takes time for land, and particularly oceans, to heat up and cool down. Professor Horner points out this happens on a daily scale as well, when the weather stays stable. "The hottest time of day is not 12 noon. It's usually about 2 or 3pm," he says. This lag effect is more pronounced closer to our coastlines, because water takes longer to heat up and cool down than land. Copy linkFacebookX (formerly Twitter)PromotionTop StoriesPools, parties, prostitution, prison: The Scott Miller storyTopic:Swimming

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

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