On January 2, 2018 – we reached Earth’s
closest point to the sun for this entire year at 11:35 p.m. CST (central U.S.).
It occurred the morning January 3 for Europe and Africa … later in the day for
us at 3.30pm down under.
Whilst the longer days are relevant to the closer proximity
of the earth to the sun our longest days are two weeks earlier in December. Hence although the Earth is closest to the Sun presently
(said to be its Perihelion) we have a December Solstice. When the
Sun is furthest away (called the Aphelion) that event is 2 weeks after the June
Solstice.
The reason for this is principally the
moon and planets interact with both the
Earth and the Sun at the same time, being drawn by the additional gravitational
effect of the Sun.
Interestingly enough from the 1970’s US Astronauts and probes have
also revealed the moons recessionary rate = 3.8 centimetres per year as it gradually
moves further way from the earth. In the far far off future our days might conceivably
stretch out to be a thousand hours.
But for the present a warm welcome to 2018 from Melbourne where it is foceast to be 42 today with a gusty northerly. Prior to today it has been it has been remarkably cool. During December we continued to enjoy early morning showers and bouts of heavy downpours. Amazingly
we have just had one of our wettest Decembers with a third of annual rainfall falling
just in December. The green landscape this year contrasts with the words of Wheelers
Christmas Carol where we sing “The north wind tosses the leaves as the grass in
the paddock is brown”.
4 comments:
I have always wondered at the amazing coincidence of a moon that has the appearance of the same diameter as our star. I suppose in the future it shall gradually appear smaller to us. I wonder though, are we moving slightly farther from the sun at the same time?
Hi Halle,
You are in good company because that is what successive generations have been trying to figure out for thousands of years. But as you no doubt are aware with spacecraft and vastly superior tracking facilities we can now get a very accurate starting point of distance of the sun from the earth- at 149,597,870,696 kilometers. Having established such a precise yardstick New Scientist reported Russian dynamists calculated a 15 cm per year gradual movement apart.
So your hunch is right. But the unresolved question is what is causing this?
One idea put forward vie the New Scientist is the Sun is continually losing mass so its gravitational pull is decreasing which is causing the earth to move away. The reason could be depletion from fusion, the erosion caused by solar winds or that mysteries dark matter or even a combination thereof.
But your hunch about why, may also turn out to be right, and in any event will be just as good as any. If you like, let us now your further thoughts on the matter as it’s always fascinating to discuss such things with others.
Best wishes
It's interesting too that the sun appears to stop in the sky for three days at solstice time and then moves one degree north or south (as the case may be) before seeming to speed up for the equinoxes when it sails across the equator. It's all quite marvelous, isn't it?
We're very lucky to have such a very large moon as our world's axial tilt would wobble wildly - even sometimes aiming straight at the sun for months at a time. Instead, the axis's obliquity is essentially stable at plus/minus a degree or so of 23 degrees. The torque it exerts because it doesn't revolve around Earth's equator (the only moon in our solar system to do so) means the moon regulates our climate keeping it gentle and relatively consistent over eons. Once again, quite marvelous.
May you have a bright and miraculous New Year, Lindsay.
Hi Susan,
Thanks for adding some interesting points to the discussion and I agree it’ all quite marvellous. Amazing to think our entire solar system orbits around the Milky Way in such a interdependent way with the Sun taking 230 million years to complete just one orbit even though its velocity is about 828,000 KM/hr.
But of course by far the biggest influence, due its massive size in our solar system, is our sun. The sun does appear at different points in the sky, due principally to what you said about the earth orbital tilt at around 23 degrees but also due to other factors. It is the combination of the tilt and the elliptical orbit with the pull from other planets that gives the weird figure 8 of the Sun in the sky over a period of time.
May you also have a bright and miraculous New Year, Susan.
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