After Auntie Dawn hinted to look up Galileo after my Think Piece on The Moon, I began to understand something else I had been considering, namely why the night is the same length as the day twice a year. Coincidentally, my piece last week about The Moon was at the autumn version of this “Equinox” as it is called. I am going to cheat a bit and, by the magic of blogging, set this post to be published at the Spring Equinox.
Having established in my other piece that the Earth is a ball, I was pleased to see that Galileo agreed with me, and also supported the view of another ancient philospher, Copernicus, that the Earth goes round the Sun and not vice versa. My observations of the stars and other moving objects called planets support this concept.
Now why do you think the days are longer in the summer and shorter in the winter. And about now they are equal? Imagine the Earth going round the Sun with a line drawn around its middle which we call the Equator. That’s the line that would cut the ball of the Earth in two halves (just like Mummy cuts the melon in half). If the Earth was upright, and went round the Sun like that, the days would always be the same length. Now if you tilt the Earth a bit, the Sun shines more on the lower half in the winter and more on the upper half in the summer. If you are at the Equator you would actually see the Sun’s path going up and down in the sky, being north of you in summer and south of you in winter.
Where we live the Sun is always in the south at noon, but in winter it is much further south than east at sunrise, and in the summer it is much further north of east at sunrise. I can tell this from the shadows on my wall. This would be correct if the Earth is tilted to the path (which Copernicus and Galileo call its orbit) that it uses around the sun. And because we can see it further north in summer, it rises earlier. And in the winter it is further south and it rises later because it has more of the ball of the Earth to hide behind.
You really need a ball and some pencils to draw lines of sight on.
But at the Equinox the sun rises in the east and sets in the west. Not north or south of it. And so the day and night are equal lengths.
And in the spring that means warmer weather is coming, the grass is growing, and soon we’ll be able to go outside and eat grass all day long. So I like the Spring Equinox the best.