Wednesday, 2 August 2017

Halos from deep space

Now don't get too excited, it's not the news of first exoplanet halo observation. Instead, a space craft has observed halos on Earth - from deep space, 1,5 million kilometers from Earth.
NOAA’s Deep Space Climate Observatory, (DSCOVR) is located at first Lagrangian point. It's 1,5 million km from Earth, between Earth and the Sun. It takes hourly (or every two hours, depending on time of year) a picture of sunlit Earth with its Earth Polychromatic Imaging Camera (EPIC). Some of these pictures show a bright glint, which was initially thought to be solar reflection from still ocean surface but soon discovered appearing on land areas too. Size of the glint was too big to be caused by lakes. An idea of horizontally oriented ice crystals in upper atmosphere as a reflecting surface was introduced and challenged with series of tests. It proved to be a winning theory. One of the tests was to study whether the angle between the Sun and Earth is the same as the angle between the spacecraft and Earth on the location of the glint. And it was a match for every glint recorded. So, the reflection from ice crystals can be regarded as a halo, namely a subsun. With a very maximum Sun elevation.

One might think that 1,5 million kilometers is a record breaking distance to observe halo's, but while investigating the glints NASA scientists found out that similar glints were noticed in pictures taken by Galileo spacecraft back in 1993, when it was on its way to study Jupiter and its moons. Galileo took the pictures at 2,08 million km distance from Earth. Originally glints recorded by Galileo were reported to be seen only over oceans, not over land, but that was a mistake. When inspected again, Galileo footage clearly shows glints also over land areas.

Not only being a curiosity for halo enthusiasts, detecting similar glints could be used to study exoplanets. If exo can produce halos it could be a sign of water in its atmosphere and that can give a hint about planets habitability. Hubble Space telescope successor, James Webb Space Telescope (JWST) is planned to be launched in October 2018. It will be stationed at second Lagrangian point, so observing subsun on Earth is impossible for JWST, but maybe it is capable of spotting extra Terrestrial halos? Or maybe we need to wait for the next generation telescope for that. But perhaps, some day this articles header can be re-used, having a slightly more exciting meaning.

The original article from American Geophysical Union (AGU): Ice particles in Earth’s atmosphere create bright flashes seen from space 

Friday, 21 July 2017

Halo simulation using a single ice crystal population

Halo simulation aims at finding those ice crystal shape and orientation parameters that best reproduce observed characteristics in a given display. Publicly available simulation software provide a great deal of flexibility by allowing users to include several separate crystal populations and by giving them free hands to set population-specific crystal shape and orientation parameters as they see fit. For example, simulating the 22nd September 2012 display (shown above) would require including at least five crystal populations. These are necessary as the observed halos associate with all five principal types of crystal orientation (random, plate, column, Parry, and Lowitz orientations), and each population accommodates only one orientation type. As each population needs its own shape and orientation parameters, the total number of input parameters is almost impractical.

I have recently entertained myself with the idea of introducing a mutual dependence between the orientation and shape parameters. This could reduce some of the complexity currently associated with the simulation. In such framework, even complicated-looking displays can be reasonably well simulated using only a handful of user-specified input parameters. Furthermore, the idea of only one crystal population in one halo-making cloud is conceptually appealing.

To illustrate the approach I've been thinking of, the figure above shows a possible orientation-shape dependency. Let's consider, for now, the aspect ratio as the only measure of crystal shape. The y-axis representing the angle of crystal's axis with local vertical, perfect plate and column orientations correspond to values 0° and 90°, respectively. We assume a Gaussian distribution such that 95% of crystals (at each aspect ratio) go within the shaded region. In the regime of equidimensional crystals in the middle, the orientation angle takes all values between 0° and 90°. Otherwise, it is constrained around either 0° or 90°, depending on whether the shape is more like a plate or rather like a column. The constraint is particularly strict in the extremes at far left and far right, indicating that perfect orientations are most probable to occur with the thinnest plates and longest columns.

I have produced the all-sky simulations below by running a home-made simulation program and assuming the orientation-shape dependency exactly as laid out above. Each simulation uses only one crystal population, and the six simulations differ in only two input parameters that control the distribution of crystal aspect ratio. At the top, the distribution is set narrow such that the crystals are either (a) all plates, (b) all equidimensionals, or (c) all columns. In panels (d)-(f), the distribution is made gradually wider around the equidimensional mean. Clearly, changing just two input parameters is enough to allow reproducing a variety of displays.

To simulate occurrences of Parry and Lowitz arcs, we need to introduce another dependency to constrain crystal's rotation about its axis. In my trials, I have assumed that the rotation averages to that required in the Parry orientation, but the spread around the mean rotation depends on crystal base shape (see the figure below for illustration). Only crystals with a considerable tendency towards either triangular or tabular habit are assigned with spread small enough to allow Parry arcs to form. For conventional hexagons and other possible base shapes, we set the spread large to make the distribution of rotation angles essentially uniform.

Now, using the two dependences as laid out above and running my home-made program, panels (a)-(c) below illustrate the effect of varying the distribution of column crystal base shapes alone. Four input parameters are used to control these variations. In panel (a), all crystals are nearly regular hexagons in their bases. Halos attributed to the column orientation are well reproduced, and no signs of Parry arcs are seen. In panel (c), crystals are constrained to the tabular base shape. This scenario produces only halos associated with the Parry orientation. Panel (b) is for the case where the base shape varies considerably, such that halos associated with both column and Parry orientations are represented.

To get not just Parry but also Lowitz arcs, one needs to take benefit from the two types of dependence at once. This is attempted in panels (d)-(f) for three different solar elevations. Although the all-sky projection makes direct comparison slightly complicated, I'd say the similarity of panels (d) and (e) with the appearance of the 22nd September display is remarkable.

While assuming the same dependencies to hold for the behaviour of orientation and rotation angles as a function of crystal shape, all variations in the simulations shown here were produced by changing just seven input parameters. One goes for the solar elevation, and the remaining six were used to characterize crystal shapes.

Tuesday, 4 July 2017

Cross and Crescent from 1664

From The Graphic Collection of the Hungarian National Museum. MTKcs.9613.T. and MTKcs.9612.T. Reproduced with permission.

On 3 August 1664, a curious phenomenon made the inhabitants of Pápa, Hungary wonder. Between 11 and 12 pm a shining white cross appeared in the sky together with the crescent Moon. They seemed to be fighting for about an hour, either the one or the other overcoming, but by midnight the Moon had deferred to the cross, which – according to the contemporary description – might be a good omen.
Two anonymous engravings eternalised the apparition, both from the late 17th century. They are part of The Graphic Collection of the Hungarian National Museum, a collection which also contains a few etchings depicting historical halo observations. These have earlier been dealt with in a Hungarian language article [Farkas A., Kiricsi Á., Klemm L. (2011) „(R)égi csodajelek, 17-18. századi halójelenségek a Magyar Nemzeti Múzeumból”. Fizikai Szemle 61 (12): 407-413.], and are going to serve as the basis for the next historical mini-series of The Halo Vault.

Of course, we cannot say with certainty what the 17th century inhabitants of Pápa saw exactly, but presumably it was a halo phenomenon. The description might indicate a lunar pillar with a stretch of a cloud, or even a pillar with upper tangent-arc. The time given in the contemporary accounts is rather problematic, however. The Moon was almost full and already 21° high in the sky at 11 pm, so the implied lunar pillar can certainly be ruled out. But if we continue theorizing, and suppose that the date given is still according to the Julian Calendar, the idea of a pillar is much more likely, as the Moon in the given time-slot was between -3,5° and 6° (though not in such a thin crescent shape as in the images). In Hungary the Georgian Calendar had been in use for almost 80 years in 1664; but we know that at least one of the two engravings is by a German master, and in the Protestant areas of Germany the adoption of the calendar reform was much slower. In some parts the reform was only enacted in the 18th century. But again, this is only a hypothesis, we cannot fully decipher the two images and their descriptions.

The heavenly cross appearing in the sky was considered a mysterious sign, and as usual with such unaccountable phenomena, reports tried to authenticate it in various ways. As we learn from the text below one of the engravings, the cross was not only visible in Pápa, but also some 120 kms away, near Vienna, the seat of the Habsburg monarchy. The other document mentions that even soldiers witnessed it, thus giving the account more credit.

The cross subjugating the Moon could easily be considered a good sign in 17th century Hungary. Most of the country at that time was under Ottoman Rule, and the Christian cross overcoming the traditional Muslim symbol of the crescent must have been thought by many as a symbol of divine providence against the Turks.

By Ágnes Kiricsi

Sunday, 18 June 2017

Pyramids returned and came with multiple plate arcs

The halos I got earlier today ended at midday but while up mowing the ATV and foot trails I saw halos reappearing! I immediately saw a nice bright lower 9d plate arc my second one since 2002 and both lower 24d plate arcs my best to date! As the clouds moved in closer the halos got better the 18d plate arcs got bright and rather colorful and actually showed a slight curve. At 7:00PM when the sun got low enough for it to happen I got upper 9 and 24d plate arcs and those were two new halo forms for me.

Saturday, 17 June 2017

Reign of the Pyramids

Well seems like most of the rare halos I have been getting are pyramidal this year and I like pyramidal stuff. This morning I got up and later on 18 and 23d halos formed along with a nice upper 23d plate arc and 18d plate arcs. Later on faint 9d halo and when looking at the convex mirror faint 35d halo and it shows up in Photoshop.

Tuesday, 13 June 2017

Plates 1 and 2 for the Bravais book

The internet copy of the Auguste Bravais book "Memoire sur Les Halos..." has incompletely scanned figures. So I went to the Kuopio repository library to have them copied from the original. Earlier, before this only Finnish copy of the Bravais was moved to repository library, I had already copied plates 3 and 4. Given below are now full reproductions also of plates 1 and 2, that a worker at the library kindly scanned.

There is a re-print for sale of the Bravais book, but I have heard it too has incomplete figure plates. Possibly it is made from the same scan that is available online.

Monday, 5 June 2017

Odd radius plate display in Czechia

On June 4th a cold front was advancing towards Czechia with thick Ci/Cs cloud cover ahead of the front.
Zbyněk Černoch was keeping an eye for any potential halos that might show up. As soon as the cloud cover started to sublimate (it was nicely visible on satellite imagery), bright pyramidal plate arcs showed up. The 23° parhelion is very easily distinguishable with its characteristic shape.

A few moments later, the 23° parhelion lost its initial shape, but became a little more coloured.

The same photos, with B-R processing:

Thursday, 1 June 2017

The all-sky display of 30th May 2017 at Pskov Oblast, Russia

The first part of this display occurred between 6-50 and 8-30 hours. During this period only the 22 halo (which accompanied by other common halos in stacks) were seen in this part of the sky. However, at the end of this period a wonderful cloud crossed the sun. This cloud gave a complex of rare halos from Parry and Lowitz orientations - on the stack I found the sharp and bright upper suncave Parry arc together with the upper Lowitz arc. I saw a part of the middle Lowitz arc, which was below the right parhelion, with the naked eye (1).

Thereafter, cirrus clouds cleared, and in satellite images no high-level clouds were visible, so I went to a bicycle training although the meteogram would predict the arrival of a new portion of cirrus in the coming hours. If I had looked at during my training, I could have seen that the air ahead of a low-pressure system after passing the Baltic sea, created fresh cirrus clouds above Estonia!

At 15-40 I found that far cirrus clouds which were visible for the last hour at the horizon, now reached the sun. At this moment I saw a colourful lower tangent arc. It was only 5 km to my house , so I accelerated in order to be in time to photograph it. However, a few minutes later I saw a large scale complex in the sky - above the sun there also appeared an upper tangent arc, both parhelia, and a full parhelic circle! The last few kilometers I rode as fast as I could. Luckily, I not too late!

16-17. All three Lowitz arcs are in one image. The B-R version is available here
Visually, it seemed to me that the bright parhelic circle contained a red fringe, which also surrounded a diffuse 120 parhelion. Blue minus red versions of some stacks clearly show this diffraction effect (2).  The cirrus clouds were beautiful, they contained not only a smooth veil, but also sharp textures like virga. What they are fresh was seen with the naked eye.

After half an hour, the bright parhelic circle disappeared, when clouds which produced it, drifted to the south-east direction. The upper tangent arc then started to get brighter. At this time I also saw visually both the infralateral arc and the 46 halo above the sun from the 11-00 to 01-00 positions. The complex became less bright after one hour, but at the same time, fragments of a distant parhelic circle was still visible.

Thereafter, I could see only a split upper tangent arc. With the naked eye I could not understand what it is - a Parry arc or a 23 plate arc. The stack taken during this period showed an excellent odd-radius plate complex!

Monday, 29 May 2017

Large scale odd radius halo complex on Memorial Holiday 5-29-17

About an hour before midday a layer of cirrus stratus clouds began moving toward the sun and I looked up and saw a colorful 22d halo and I noticed it looked doubled all the way around and looking close to the sun I saw weak 9d halo. I grabbed my camera and then it got spectacular. The 24d halo not only was bright it was sharp and complete and was my best yet to date. While taking picture after picture I saw a segment of a larger halo appear and it turned out the be 35d halo. As the clouds moved thru it peaked with a total of 5 rings the 9,20,22,24, and 35d halos and the 35d halo I got today was my best to date. This could be my best pyramidal display to date but who knows I could get better some day.

Wednesday, 17 May 2017

Recent displays from Northwestern Russia

In this post I want to share some of my observations from last month, which I made in St Petersburg (from 15th April to 5th May) and in Pskov Oblast (from 7th May to present time). In total there were eleven displays, six of them comprising pyramidal halo forms. Many of these pyramidal displays were minor, so I will not present them.

20th April

The photo on left shows a purely odd-radius plate complex. There are only the upper 23 plate arc with its 23 halo and a couple of 18 plate arcs. On the photo on right you can see fragments of weak odd radius circular halos. Together with the broad 22 halo at the 02-00 position there is the 20 halo and also the diffuse 35 halo.

28th April

Together with classic halo forms in stacks pyramidal halos appeared with odd-radius plate arcs. On photos above you can see lower 24 plate arcs with the 24 halo and the 9 halo (with possible the lower 9 plate arc). The weak and diffuse upper 23 plate arc is also available.

30th April

In the morning there was a short display which lasted less than one hour. The display was not predicted by the meteogram, so maybe I missed most of the display, which was earlier that morning. In any case I saw bright parhelia with the colourful circumzenithal arc, and got in the stack the strong parhelic circle and the upper suncave Parry arc together with the nice upper tangent arc. I think it is the Parry arc, and not an upper 23 plate arc, because the display does not contain no other pyramidal halo forms, and the arc looks pretty sharp.

1st May

In the morning I observed the large and bright upper tangent arc for around one hour. Infralateral arcs were easily seen with naked eye. Together with bright parhelia I saw fragments of a parhelic circle. In stacks the rare Wegener arc was found.

5th May

On that day there was a protracted display, that lasted between six and sixteen hours. But my camera had recorded interesting halos only at the start, on the sunrise. It was an odd-radius circular complex which contained pyramid halos with radii 9, 18, 24 and 35 degrees. It seems the 24 halo included rudimentary upper and lower 24 plate arcs.

10th May

No rare halos on that morning but I saw the supralateral arc visually very well, that happens not often. A curious circumzenithal arc appeared a little later. The CZA was diffuse, that is not typical for this halo. 

Sunday, 7 May 2017

Update On The Earliest Known Halo Photograph

Following recent comments by one of our readers, Aysun Ülger, on the post regarding the earliest known photograph of a halo, I thought it would be useful to post an update in order to make a permanent record of the images he has been kind enough to share with us. 

First, from the book "Manual of Meteorology" by Sir Napier Shaw dated 1926, we have two images of halos. The one on the left taken in Aberdeen, Scotland by G. A. Clarke and is dated 30th September 1910, and the one on the right taken in Potsdam, Germany by A. Sprung is dated 13th March 1902. This is now the earliest photograph of a halo we have.
Second, whilst not an actual photograph of a halo, I also thought it would be useful to reproduce an illustration which was included in the book "The Voyage of the 'Discovery'" by Captain Robert F. Scott dated 1905 giving an account of his Antarctic expedition between 1901 and 1904. 
To my mind, this illustration has a very modern look to it, as if it could have been drawn from a photograph taken with a modern all sky lens. If only they had such equipment back then! I also like the way the artist has differentiated the coloured and white halos. What is of great interest is that it has one of the earliest depictions of the Kern arc that we know about. It is interesting to read Scott's own account of the display and it is worth quoting in full,

"November 29 - Shortly after four o'clock to-day we observed the most striking atmospheric phenomenon we have yet seen in these regions. We were enveloped in a light, thin stratus cloud of small ice-crystals; it could not have extended to any height, as the sun was only lightly veiled. From these drifting crystals above, the sun's rays were reflected in such an extraordinary manner that the whole arch of the heavens was traced with circles and lines of brilliant prismatic or white light. The coloured circles of a bright double halo were touched or intersected by one which ran about us parallel to the horizon; above this, again, a gorgeous prismatic ring encircled the zenith; away from the sun was a white fogbow, with two bright mock suns where it intersected the horizon circle. The whole effect was almost bewildering, and its beauty is far beyond the descriptive powers of my sledging pencil. We have often seen double halos, fog-bows, mock suns, and even indications of other circles, but we have never been privileged to witness a display that approaches in splendour that of to-day. We stopped, whilst Wilson took notes of the artistic composition, and I altitudes and bearings of the various light effects. If it is robbed of some of the beauties of a milder climate, our region has certainly pictures of its own to display.

On our return to the ship I could find no account, in such reference books as we had, of anything to equal this scene, nor have I since heard of its having been witnessed elsewhere. The accompanying drawing shows more clearly than I can describe what we actually saw; our artist has shown it diagrammatically, and the observer is supposed to be looking straight upwards towards the zenith." (The Voyage of the 'Discovery', Captain Robert F. Scott, pp 35-36).

So then, the bar is now set at 13th March 1902. This is a mere 76 years after the birth of photography. With a little more effort I am sure we can push this date back into the nineteenth century and even further. As Aysun commented, "Let's keep going"!

Tuesday, 2 May 2017

Late diamond dust display in Finland

Cold spring has kept diamond dust popping up late. On 28 April a display with sharp Moilanen arc was seen in Järvenpää of southern Finland and could be the latest one on our records. For certain, nothing nearly this good has been seen this far into the spring. Two people sent photos to Taivaanvahti site. The image above was taken by Jarkko Lakso at 6:14 local time and another image was snapped at 6:55 by Emmi Mäkinen.

The cold air mass seems to be in no hurry going anywhere and is forecasted to even tighten its grip at the end of the week. So who knows we are in for more diamond dust surprises at the summer's door.

Wednesday, 19 April 2017

Odd radius plate arcs in diamond dust display

The lamp in the photo is a couple of degrees below the horizon and there are 18, 20, 24 and 35° plate arcs. Plus a bit of a helic arc that in this kind of display could be of the odd radius type or at least contributed by it. This stage lasted only a few minutes after which lesser halos were visible for the rest of night. Under the outdoor light shining in the photo an upper 23° continued its presence longer. The display appeared on the night of 5/6 January 2017. Temperature was -27° C.

The photo below shows the location. The camera-lamp configuration is not the same as for the photo above, where the lamp and the camera were more level.

Friday, 14 April 2017

Recent displays from St Petersburg, Russia

In this post, I'm including the most interesting displays observed during the last month.

14th March 2017

On that day, halos appeared in the morning in separate cirrus clouds. Their arrival was not predicted by the meteogram. When I looked out from the window, I saw a bright CZA, but when I came down, it had disappeared. Nevertheless, I could see the weak supralateral arc. Half an hour later, I also saw a nice infralateral arc, when the cirrus cloud reached the horizon.

29th March 2017

In the evening bright parhelion was detected, and then a little while later also the wide circumzenithal arc. The halos were produced by the anvil of a convection cell.

1st April 2017

In the morning, at 10-00, the sky was clear. But in the south-west direction, low over the horizon a lot of cirrus clouds were visible. Their arrival was extended for an hour and a half. When a border of a front of cirrus clouds started to arrive, I noticed that it was weak and almost transparent. When these weak clouds reached the sun, at first I did not notice any halos. But soon, some markers of sub-visual odd radius display appeared.

It was broad and undefined halo in 22° area, with pretty obvious upper 23° plate arc in some moments. In the reflection of my sunglasses these things were visible a lot better. These weak odd radius halos were visible for around a half of hour, or even more while the area of weak cirrus crossed the sun.

Then, on the right-hand side pretty bright 22° halo started to appear. It was the arrival of main part of cirrus. In that area clouds were common and solid. After few minutes both bright tangent arcs appeared. Lower tangent arc was brighter than upper. I also noticed big infralateral arc on the right-hand side. It was pretty weak, but well coloured. I could see the arc better when I used peripheral vision.

This peak of the display was rather lengthy, and during its course I also watched both 120° parhelia, parhelic circle (it was easily seen within 22° ring), and the top part of 46° halo (likely it was the combination of supralateral arc and 46 halo. Although both were weak, together they became visually visible).
The peak was interrupted when middle-level cloud started to arrive. Then I saw a couple times only bright 22° halo

7th April 2017

The display looked quite ordinary, so I was glad I detected pyramidal halos such as upper 23° plate arc and 9° column arc.

9th April 2017

On that day, there was only a weak 22° halo. But the stack discovered also 18° halo/18° plate arc

10th April 2017

It was the weak display, which lasted most of the day. There was no suspicion that there may be pyramidal halos. But still I got upper 23° plate, 18° plate arc and 9° halo in the stacks.

Tuesday, 11 April 2017

Halo Phenomena in Olaus Magnus’s Historia de Gentibus Septentrionalibus (Part 3)

Halo phenomena in Historia de Gentibus Septentrionalibus, Bk. 1, Ch, 16. Image from

“And no wonder: since we are so constituted, that everyday things, even if they deserve our amazement, pass us by; on the other hand the slightest things if they spring up in an unfamiliar way, become a pleasant spectacle. (…) when anything varies from normality, everyone’s face is turned to the sky.” (Ch. 15.) No one who is interested in halos would say that Olaus Magnus, the 16th century Swedish theologian was not right when he wrote this. Even nowadays, most people rarely look up, and they take the sky for granted. If however, there is a comet, eclipse or halo phenomenon which becomes hyped by the media, people’s head immediately turn up for at least a day or two. But why not longer? I’m always surprised.

We have arrived at the final post of our three-part series introducing Olaus Magnus’s description of halos in Historia de Gentibus Septentrionalibus (part 1, part 2). This 16th century work dedicates several chapters to halo phenomena and illustrates the descriptions with fine woodcuts. According to Olaus, halos tend to appear mostly on spring mornings, especially when the surface of the earth is covered by deep snow and they usually don’t last more than one and a half or two hours. As he states in Chapter 15, this is due to the fact that clouds tend to change very quickly: they either thin or thicken too much for these phenomena to be observed.

This latter statement is indeed a realistic one, but scientific accuracy is not a characteristic feature of Olaus’s work. Historia de Gentibus Septentrionalibus was printed just around the advent of the scientific revolution, in 1555, when interest in natural phenomena was growing. Olaus is a Renaissance author, who lays much emphasis on collecting and recovering the scientific knowledge of ancient writers. However – although he tries to explain the formation of halos – he does not venture into looking further than the sources of the Antiquity and contemporary superstitions. This becomes evident when he continues his argumentation about clouds: (…) since they are caused by the reflection of the black clouds and the whiteness of the very thick snow which wholly covers the face of the earth, [halos] are chiefly seen in February and March, because of the distant, slanting position of the sun”

As for contemporary beliefs, in Chapter 15 he treats halos together with comets and talks about them as bad omen, signalling “change of existing order” and meaning “grievous prognostications”. He, however, does not elaborate on halos affecting social order; in these two chapters he mostly mentions them as signals of unfavourable weather. “The blacker clouds in the lower circle foretell that savager tempests are on their way” (Ch. 16).
Halo phenomena in Historia de Gentibus Septentrionalibus, Bk. 1, Ch, 15. Image from
From the strange description that Olaus gives, and also from the woodcuts, it becomes evident that personally he never witnessed the appearance of such phenomena. (…) one circle, spacious and entirely white forms in the clouds over the horizon, but with another on its inner edge, which is black from being more compressed in size. On their surface these very large circles have four lines, or round openings distinguished by their saffron colour; between these towards the south among white clouds that are filled with snow, appear two circles set opposite each other, one of which is black on its outer rim, and on the inner, white. The other, lower circle, in the centre of which the disk of the sun is seen (this is intersected by the upper circle, which has a different centre) is white on the outer rim and dark on the inner, though the nearer the sun it lies, the whiter it is. Moreover, opposite the sun, round about the centre of the very large circle which spreads, as I said, over the horizon, there appears a bow lying diagonally, with colours like those of a rainbow, amid thick clouds, reddish on the outside, purple or saffron-yellow in the middle, and green below.” (Ch. 15)

Olaus’s Historia was written several decades before the three famous historical displays that marked a milestone in halo-science. It was the Rome displays of 1629 and 1630 which aroused the interest of Descartes so much that he decided to turn to halos. His publication of Les Météores in 1637 meant the first step towards a modern explanation of halo formation. Mathematical and physical approach to halos only started with his work and (after the 1661 Danzig display) it was further elaborated by the Dutch Christiaan Huygens. When reading Olaus Magnus’s Historia, we should not forget that at the time of its publication, the real scientific revolution was yet to come.

By Ágnes Kiricsi

English translation by Peter Fisher and Humphrey Higgens from: Olaus Magnus, A Description of the Northern Peoples, 1555, Vol. 1. Ed.: Peter Foote, Hakluyt Society, 1996.