Earth and Sun

25 March 2014 ~ Question of the Day ~ Earth and The Sun

What relationship between earth and the sun causes the seasons?

The basic reason is that the earth’s spin axis is not aligned to the sun, so that as the earth goes around the sun first one hemisphere gets most of the sunlight and energy (summer), then they get equal amounts (equinoxes), then the other one gets the lions share (winter in the original hemisphere and summer in the other one.
Here is a graphic showing how it works:

This image shows what the various lines of latitude mean with respect to the Northern hemisphere summer:

And here is the >Wikipedia article on the subject.
If you have a spinning globe on a tilted axis, it can help to turn the lights out, and set up a flashlight on the other side of the room pointing at the globe to act as the sun, and spin the globe to simulate days passing, and turn the base to simulate the change of seasons as the spin axis rotates around the earth.

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Kathy’s video is great – and one of the best little explanations I have seen of the major influences on the earth’s orbit.

There are a few other factors – like changes in day length due to tidal effects from the moon, and changes due to extreme solar activity, but they are very small usually – small fractions of a second in any one year.
So certainly the angle of the Sun through the sky is changing, but very slowly, and only by a couple of degrees every few thousand years.
The unaided human eye might just be able to notice the change over a century, but it would take meticulous record keeping to be certain.

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Hi OM
My question then has to become – exactly what is the record keeping that is informing experience (FOS’s or anyone else’s).

Our memories are not that reliable.
We are all very suggestible.
The sun definitely changes its position in the sky every day, particularly so at this time of year – for us it is getting lower and lower in the sky, for you it will be getting higher and higher.

I have seen no evidence of any strange wobbles.
If there had been any strange wobbles, then all celestial navigation tables would need to be redone, and I have not heard of any such thing. I have a couple of friends who live on their yachts, and travel the world – so I think I would have heard.