Winter (or Summer) Solstice

Winter (or Summer) Solstice

Happy Winter (or Summer) Solstice

Our Winter Solstice – Shortest Day of the Year – Monday, 21 June 2021 at 1:32 pm AEST or 03:32 UTC. It also marks the shortest day of the year here in the southern hemisphere, when we receive the least energy from the Sun.

It is commonly incorrectly thought that the seasons are determined by a change in distance between us and the Sun. It is, however, actually the tilt of the Earth that has the biggest effect on the distribution of energy around the globe.

The solstices describe the points during the Earth’s orbit where the tilt is pointing towards or away from the Sun.

Our winter solstice occurs when the southern hemisphere is pointed most away from the Sun. This then coincides with when the northern hemisphere is most pointed towards the Sun, making it the northern hemisphere’s summer solstice.

The tilt of the Earth dictates both how long the Sun is visiting bow tonight us in the sky and hence how much the Sun’s energy spreads across the planet.

As the southern hemisphere is tilted further from the Sun, the angle at which sunlight hits the Earth is shallower, meaning the light and energy spreads across a larger area.

Since, therefore the energy is more spread out, it means that the heat from the Sun is not as intense and so not as effective and this is why it is colder in winter.

Position of Earth in relation to the Sun during the June solstice (not to scale).

A solstice happens when the sun’s zenith is at its furthest point from the equator. On the June solstice, it reaches its northernmost point and the Earth’s North Pole tilts directly towards the sun, at about 23.4 degrees.

It’s also known as the northern solstice because it occurs when the sun is directly over the Tropic of Cancer in the Northern Hemisphere.

Solstice comes from the Latin words sol, meaning Sun and sistere, meaning to come to a stop or stand still. On the day of the June solstice, the Sun reaches its northernmost position, as seen from the Earth. At that moment, its zenith does not move north or south as during most other days of the year, but it stands still at the Tropic of Cancer. It then reverses its direction and starts moving south again.

Astronomy has been important to people for thousands of years.

The ancient construction known as Stonehenge in England may have been designed, among other purposes, to pay special honor to the solstices and equinoxes.

These are the times and locations during Earth’s journey around the Sun that we humans have long used to mark our seasons.

This is an artist impression as to what Stonehenge might have looked about 2400 BC. At dawn on the Northern hemisphere Summer Solstice, the rays of the Sun would have shone straight through what is called the “slaughter stones” to exactly strike the “altar stone” in the centre.

Australian Indigenous People also measured the Solstices.

They have discovered that waist-high boulders at the tip of the egg-shaped point along the ring to the position on the horizon where the sun sets at the summer and winter solstice – the longest and shortest day of the year.

The axis from top to bottom points towards the equinox – when the length of day equals night.

An egg-shaped ring of standing stones in Australia could prove to be even older than Britain’s Stonehenge – and it may show that ancient Aboriginal cultures had a deep understanding of the movements of the stars.

Fifty metres wide and containing more than 100 basalt boulders, the site of Wurdi Youang in Victoria was noted by European settlers two centuries ago, and charted by archaeologists in 1977, but only now is its purpose being rediscovered.

It is thought the site was built by the Wadda Wurrung people – the traditional inhabitants of the area. All understanding of the rocks’ significance was lost, however, when traditional language and practices were banned at the beginning of the 20th Century.

At Stonehenge, the sun aligns instead with gaps in the stones on these key dates in the solar calendar.

The probability that the layout of Wurdi Youang is a coincidence is minuscule.

Donna the Astronomer

I am a keen astronomer lucky enough to live and work in Coonabarabran the Astronomy Capital of Australia! I am a ‘Drover’s Brat’ and discoverer of a couple of comets and asteroids. I operate Milroy Observatory and can show you how to best integrate dark sky experiences into your tourism, farm stay or AirBnB business.

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