Many ancient legends talk of the Sun chasing the Moon. In modern times, many amateur scientists and even some professional ones dismiss this ancient view.

But ironically, there is also a sense in which these modern purists are more than a century out of date. 

Every day, moonrise is about fifty minutes later than it was the previous day.  [1] Sunrise, on the other hand, is at about the same time. Sunrise varies a few minutes with the seasons, back and forth, but never so drastically as moonrise does on a daily basis. 

This led to the ancients concluding that the Sun was chasing the Moon through the sky. And if you believe as they did that the Earth is the centre of the Universe, that makes perfect sense.

The Sun catches and overtakes the Moon every New Moon. And that is the other notable thing about the Moon of course. It has phases.

When the Sun and Moon are close together in the sky, very little of the Moon can be seen. This is called a new moon as it will gradually build up to a full moon.

As the Sun leaves the Moon behind, a crescent moon becomes visible, with the larger radius curve towards the Sun, a bit like a stylised arrowhead. Some days later half of the Moon, called the first quarter, is visible, with the rounded side facing the Sun. This growing moon is called a waxing moon.

Slowly it builds to a full moon. A full moon rises at about sunset and sets at about dawn. And it then becomes a waning moon, getting smaller until it is a half moon again (called the third quarter) pointing the opposite way in the sky but again towards the Sun as the Sun catches it again. The third quarter moon rises at about midnight and sets about midday.

And over again. The ancients watched this relatively predictable cycle in the heavens and decided that there was a perfection in the heavens that the weather on Earth did not possess {often to their discomfort as to ours!) and that the Heavens were the place of the Gods where things were under better control. Astronomy became one of the earliest sciences.

We now know that this cycle is the result of two cycles. The Earth rotates on its axis, causing the sunrise and sunset. And the moon revolves around the Earth, but far more slowly, causing the time of moonrise and moonset to continually shift, and the phases of the Moon.

That's the modern view. Or most of it. It's called the Heliocentric Universe. And for many purposes it's more accurate than the Geocentric one in which everything is centred on the Earth.

But there is a newer and far better and more generally accurate picture of the Universe. It's called Relativity and the idea is probably not as new as you think. You use whatever frame of reference makes the sums easiest. And for some purposes, thinking of the Sun as chasing the Moon is the easiest way by far to understand what is going on and to get it right.

So the ancients are in this sense vindicated. And as is normally the case, the purists are quite wrong.

And this will probably be an unpopular essay as a result.