Science at home

Feeling like you’re headed for the dark side lately? That could be because 21 June is the Winter Solstice!

The Winter Solstice is the day of the year with the fewest daylight hours (and therefore the longest night).  It usually falls between 20 and 23 June in the southern hemisphere.

Each year Earth completes an orbit around the sun. The Earth’s axis is tilted about 23 degrees, so there are times each year when each hemisphere is tilted closer to or further from the sun.  This is why we have seasons, and it’s also why the sun always appears in the northern half of the sky for us.

Our Winter Solstice is when the southern hemisphere is furthest from the sun. It’s also when the sun appears to us to be travelling its lowest across the sky. At noon, you might want to take a look at shadows being cast by the sun.  They’re pretty long compared to shadows we see in midsummer!  It looks almost like it’s late afternoon.

During the Winter Solstice, if you were standing on the Antarctic Circle (latitude 66.56 degrees south), you would see the sun sitting just on the horizon during midday – but anywhere further south, and you wouldn’t see the sun peak above the horizon at all. This is referred to as polar night – no need for your sunnies!

Sailors have been using the sun to navigate for thousands of years.  If you know the date, and you observe the highest point in the sky the Sun gets to, you can figure out how far north or south you are from the equator.  Matthew Flinders, the explorer our university is named after, used this method to circumnavigate Australia.

After the solstice, the southern hemisphere will start to tilt closer to the sun, and our days will start becoming longer and our nights shorter. But the sun won’t start rising earlier just yet. The extra day length will be added to the afternoon, not the morning, so the sun will set later than at the solstice.  You can still sleep in for another few weeks!