Winter solstice June 21

June 21 marks the Winter solstice for the Southern hemisphere.

I love the Winter solstice, as it means that the days will now get longer for six months. It’s interesting to observe how the days get longer – if you plot the day length versus date, you get something like a nice sinusoidal curve unless you’re in the land of the midnight sun/moon.

The wikipedia entry on the Winter solstice is here: http://en.wikipedia.org/wiki/Winter_solstice

According to that article, the exact time of the Winter solstice is 12:26 Universal Time on June 21, so in Sydney it happens at 22:26. The article states that astronomically, a solstice occurs when a hemisphere has the greatest incline away from the Sun.

Aphelion, the point of farthest distance of the Earth from the Sun, occurs at 23:00 Universal Time on July 3 (thus 09:00 July 4 Sydney time).

Of course, as the Earth’s axis of rotation precesses (see http://en.wikipedia.org/wiki/Precession_of_the_equinoxes) and its orbit about the Sun gradually changes (in a cycle from elliptical to near-circular and back again), and the degree to which the tilt of the Earth’s axis changes, the solstices, equinoxes and aphelion and perihelion will all change.

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6 Responses to Winter solstice June 21

  1. Steve says:

    I really hate this time of year. Its not the cold as even later in July/August when its usually colder at least I feel I am getting some daylight. Not sure how I would go living at a higher lattitude. So I do always hang out for the solstice for this reason.

  2. Bronte the Cat says:

    This is a great day! From tonight, day by day for a while, there will be more sunny spots around the house for me to recline in. “Bussie boo loves the sunshine! Bussie gets down in the sunshine!”

  3. Sacha says:

    Actually, I doubt that the tilt of the axis of rotation changing will change the aphelion, perihelion, equinoxes or solstices…

    Growing up in Brisbane, I’m not used to long days in summer and short days in winter, and I doubt I’d really like enormous variations!

  4. Sacha says:

    And now it’s happened…

    I’ve been working on my large paper tonight – finished a substantial section of it, it shouldn’t take too much more work.

  5. Sacha says:

    This is very cool. Of course it would be completely disasterous for a large body to impact the Earth! Would any life survive? Possibly extremophiles – and evolution would have a near-clean slate.

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