Few people have heard of Joshua Childrey. He was born in Rochester in England in 1623 and had to live quietly in Cromwel lian times because of his family's association with the royalist cause.
Things improved, however, with the Restoration, and Childrey could indulge his interest in the natural sciences.
His writings, the most important of which was Britannia Baconia , 1660, contain numerous references to the weather and the tides, and indeed that particular book is significant for containing the first known reference to the beautiful phenomenon of zodiacal light: :
"There is another thing, which I recommend to the observation of mathematical men: which is that in February, and for a little before and a little after that month (as I have observed several years together) about six in the evening when the twilight hath almost deserted the horizon, you shall see a plainly discernible way of the twilight striking up towards the Pleiades, and seeming almost to touch them. But what the cause of it should be I cannot yet imagine, but leave it to future enquiry."
As Childrey says, zodiacal light is a faint illumination sometimes seen in the western sky a little after sunset, just after the fading of the pinky glow of twilight.
In shape it resembles an elongated pyramid, rounded at the top and rising obliquely from the horizon. In texture it seems like a kind of luminous mist reminiscent of the Milky Way, but somewhat "milkier"; it is brightest and broadest at the base, and becomes fainter and narrower as you view it higher in the sky.
The orientation of the zodiacal light relative to the horizon is dictated by the plane of the Earth's orbit around the sun.
At these latitudes, the pyramid makes only a small angle with the horizon for much of the year and is very difficult to see, but for several weeks coming up to the vernal equinox, the axis of the pyramid is not too far from vertical.
This interesting phenomenon was once thought to be sunlight shining on the very high atmosphere of the Earth. However, we now know that it is caused by sunlight reflected from debris left over after the formation of the planets, most of which lies close to the plane of the Earth's rotation around the sun.
The colour of zodiacal light is similar to that of sunlight, which tells us that the debris is not composed of gaseous atoms or molecules - which would produce a bluish colour like the sky in daylight - but ranges in the size of its constituents from microscopic dust to mini-asteroids that may be several feet across.