The Appearance of Multiple Suns

Sometimes other circles appear in the clouds, different from those I have mentioned.

They are always entirely white. Instead of having a star at their center, they usually intersect the center of the sun or the moon and seem parallel or almost parallel to the horizon.

I must explain both phenomena together because:

• they only appear in those large round clouds mentioned above
• several suns or moons can sometimes be seen in the same clouds

For example, let:

• A be noon, where the sun is accompanied by a warm wind blowing towards B
• C be the north, from where a cold wind also blows towards B.

These 2 winds gather a cloud composed of snow particles, extending so far in depth and width that they cannot pass over, under, or between each other as they usually do elsewhere, but are forced to circulate all around it.

As so, they round it out and the warm wind from the south partially melts the surrounding snow.

This snow is immediately refrozen by:

• the cold northern wind
• the proximity of the still unmelted inner snow.

It can form a large, continuous, and transparent ice ring. Its surface will be smooth due to the uniform winds that shape it.

This ice will be thicker on the side DEF, which is exposed to the warm wind and the sun, than on the other side GHI, where the snow could not melt as easily.

In this air, constitution and without a storm, there cannot be enough warmth around the cloud B to form such ice without there also being enough heat in the earth below to create vapors that support it by lifting and pushing the entire body of the cloud it encompasses towards the sky.

As a result, the sunlight, which is high towards noon, strikes all around the ice DEFGHI. It reflects off of the whiteness of the nearby snow, making this snow appear to those below as a large, entirely white circle.

Moreover, it suffices for this effect that the cloud be round and slightly more compressed around its circumference than in the middle, without the ice ring needing to be formed.

But when it is formed, one can see, from below towards point K, up to six suns, which seem embedded in the white circle like so many diamonds in a ring. Namely, the first towards E, by the rays coming directly from the sun, which I suppose to be towards A; the next two towards D and F, by the refraction of the rays that pass through the ice at these points, where its thickness decreases, bending inward on either side, as they do when passing through the crystal prism mentioned earlier.

For this reason, these two suns have their edges painted red on the side towards E, where the ice is thickest, and blue on the other side, where it is thinner.

The fourth sun appears by reflection at point H, and the last two also by reflection towards G and I, where I suppose one can draw a circle with its center at point K and passing through B, the cloud’s center, so that angles KGB and KBG or BGA are equal, and likewise KIB and KBI or BIA. For you know that reflection always occurs at equal angles and that ice, being a polished body, must represent the sun in all places from which its rays can reflect towards the eye.

However, because rays that come straight are always brighter than those refracted, and these brighter than those reflected, the sun should appear brighter towards E than towards D or F, and here still brighter than towards G, H, or I.

These three, G, H, and I, should have no colors around their edges like the two D and F, but only be white. If the viewers are not at K but somewhat more advanced towards B, so that the circle whose center is their eyes and passes through B does not cut the circumference of the cloud, they will not see the two suns G and I, but only the other four. Conversely, if they are far back towards H or beyond towards C, they will see only the five D, E, F, G, and I. And if they are far enough beyond, they will see only the three D, E, F, which will no longer be in a white circle but crossed by a white bar. Likewise, when the sun is so low on the horizon that it cannot illuminate the part of the cloud GHI, or if it is not yet formed, it is evident that only the three suns D, E, F should be seen.

Furthermore, I have only made you consider the plane of this cloud so far, and there are still various things to note that will be better seen in its profile. First of all, although the sun is not in the straight line that goes from E to the eye K, but higher or lower, it should still appear in that direction. Especially if the ice does not extend too much in height or depth.

For then, the surface of this ice will be so curved that wherever the sun is, it will almost always be able to reflect its rays towards K. As if it has in its thickness the shape enclosed between lines 123 and 456, it is evident that not only when the sun is in the straight line A2, its rays passing through will be able to go towards the eye K; but also when it is much lower, as in line SI, or much higher, as in line T3; and thus always make it appear as if it were towards E.

For assuming the ice ring is not very wide, the difference between lines 4K, 5K, and 6K is not significant. And note that this can make the sun appear even after it has set, and it can also delay or advance the shadow of sundials, making them indicate a time different from the actual one.

However, if the sun is much lower than it appears towards E, so that its rays also pass in a straight line below the ice, towards the eye K, like S7K, which I assume is parallel to SI, then besides the previous six suns, a seventh one will be seen below them, and having the most light, it will erase the shadow they could cast on the sundials. Similarly, if it is so high that its rays can pass in a straight line towards K above the ice, like T8K which is parallel to T3, and the interposed cloud is not so opaque as to block them, a seventh sun can be seen above the other six.

If the ice 123, 456 extends higher and lower to points 8 and 7, the sun being towards A, three can be seen one above the other, towards E, at points 8, 5, and 7.

Then three can also be seen one above the other towards D, and three towards F, making up to twelve suns appear embedded in the white circle DEFGHI.

If the sun is a little lower than towards S, or higher than towards T, three can again appear towards E, namely two in the white circle and another below or above.

Two can also appear towards D, and two towards F.

But I do not know of any instance where so many have been observed at once; nor even that when three have been seen one above the other, as has happened several times, any others have been noted beside them. Or that when three have been seen side by side, as has also happened several times, any others have been noted above or below.

This is because the width of the ice, marked between points 7 and 8, usually has no proportion to the size of the whole cloud’s circumference.

So the eye must be very close to point E for this width to appear large enough to distinguish three suns one above the other; and conversely, very far away, so that the rays bending towards D and F, where the ice thickness diminishes the most, can reach the eye.

It rarely happens that the cloud is so complete that more than three suns are seen at the same time. However, it is said that in the year 1625, the King of Poland saw as many as six. Only three years ago, the mathematician from Tübingen observed the four suns designated here by the letters D, E, F, H.

He particularly notes in his writings that the two suns, D and F, were red on the side facing the middle one, E, which he called the true sun, and blue on the other side, and that the fourth sun, H, was very pale and barely visible. This strongly confirms what I have said.

But the most beautiful and remarkable observation I have seen on this subject is that of the five suns that appeared in Rome in the year 1629, on March 20th, around 2 or 3 in the afternoon. And so that you may see if it agrees with my discourse, I will describe it here in the same terms in which it was then reported:

A: A Roman observer. B: Zenith above the observer. C: The true sun observed.

AB is the vertical plane in which both the observer’s eye and the observed sun exist, and in which the zenith point B lies, therefore everything is represented along the vertical line AB, as the entire vertical plane leans into it.

Around the sun C, two incomplete and concentric rainbows appeared, differing in color. The smaller, or inner one, DEF, was fuller and more complete but short, open from D to F, and always attempting to close, sometimes succeeding but soon opening again. The other, weaker and barely visible, was GHI, the outer and secondary one, also varied in color but very unstable.

A third, single-colored, very large rainbow was KLMN, entirely white, like those often seen around the moon during paraselenae. This was a complete eccentric arc from the beginning of the sun through the middle, but weak and torn towards the end from M to N, almost nonexistent.

In the common intersections of this circle with the outer rainbow GHI, two not very perfect parhelia emerged, N and K; the latter weaker, the former stronger and more brilliant. Both had a central brightness rivaling the sun, but their edges were tinged with rainbow colors; neither round and precise, but their contours uneven and gap-filled. N was a restless spectrum, emitting a thick subignous tail, NOP, with continuous reciprocation.

L and M were above the Zenith B, less vivid than the previous ones, but rounder and white, resembling their attached circle, expressing milk or pure silver, although M had almost disappeared in the middle, leaving only faint traces from time to time, as that part of the circle had faded.

Sun N disappeared before sun K, and as it faded, K became stronger, disappearing last of all, etc.

CKLMN was a white circle in which five suns were visible, and one must imagine that the observer, being at A, saw this circle hanging in the air above him, such that point B corresponded to the top of his head, and the two suns L and M were behind his shoulders when he was facing the other three, K, C, N.

The two suns K and N had colored edges and were neither as round nor as bright as the one at C, indicating that they were caused by refraction; whereas the two suns L and M were quite round, less bright, and all white, without any other color at their edges, indicating that they were caused by reflection.

Several factors could have prevented a sixth sun from appearing at V, the most plausible being that the eye was so close to it, due to the height of the cloud, that all the rays hitting the ice there reflected further away than point A.

Although point B is not represented here as close to suns L and M as to the center of the cloud, this does not prevent the rule I mentioned earlier, concerning the place where they should appear, from being observed.

Since the observer was closer to the arc LVM than to other parts of the circle, he must have perceived it as larger in comparison to the others than it actually was. Besides, these clouds are undoubtedly never perfectly round, although they may appear so to the eye.

But there are two more remarkable things to note here.

1. The sun N, which was towards the west, had a changing and uncertain shape and emitted a thick tail of fire, NOP, which sometimes appeared longer and sometimes shorter.

This was undoubtedly due to the fact that the image of the sun was distorted and irregular around N, as it is often seen when it floats on slightly trembling water or when viewed through a pane of glass with uneven surfaces.

The ice was likely somewhat agitated at that spot, and its surfaces were not as regular because it was beginning to melt there, as evidenced by the fact that the white circle was broken and almost non-existent between M and N, and that the sun N disappeared before the sun K, which seemed to strengthen as the other dissipated.

2. The second notable thing is that there were two halos around the sun C, painted in the same colors as a rainbow, with the inner one, DEF, being much more vivid and apparent than the outer one, GHI.

I have no doubt that they were caused, as I mentioned earlier, by refraction occurring not in the continuous ice where suns K and N were visible, but in another ice, divided into several small particles found above and below.

It is very likely that the same cause that formed an entire circle of ice from some of the outer parts of the cloud had arranged the neighboring parts to make these halos appear.

Therefore, if such halos are not always observed when multiple suns are seen, it is because the thickness of the cloud does not always extend beyond the circle of ice surrounding it, or it is so opaque and dark that they cannot be seen through it.

As for the location where these halos are seen, it is always around the true sun, and they have no connection with the suns that only appear to be there. Although the two, K and N, intersect the outer halo and the white circle here, this happened by chance, and I am sure that the same was not seen in places a little away from Rome, where this same phenomenon was observed.

However, I do not think their center is always on the exact straight line drawn from the eye to the sun as is the case with a rainbow; the difference is that water droplets, being round, always cause the same refraction regardless of their orientation, whereas ice particles, being flat, cause greater refraction the more obliquely they are viewed.

Since when they are formed by the swirling of wind around the circumference of a cloud, they must be oriented differently than when they are formed above or below, it can happen that two halos are seen together, one inside the other, approximately the same size but not exactly sharing the same center.

Moreover, it can happen that in addition to the winds surrounding this cloud, another wind passes over or under it, forming yet another surface of ice, causing further variations in this phenomenon. The surrounding clouds or rain, if it falls, can also contribute.

The rays reflecting from the ice in one of these clouds toward the raindrops will create parts of rainbows, with very diverse orientations.

Similarly, spectators not directly under such a cloud, but on the side between several clouds, can see other circles and other suns.

I do not believe it is necessary to elaborate further on this matter because I hope that those who have understood everything said in this treatise will not see anything in the clouds in the future whose cause they cannot easily comprehend, nor anything that will give them cause for wonder.