Category Archives: weather

The Sun Ain’t Gonna Shine (Anymore) – Maybe. Polar Exploration and the Mysterious Novaya Zemlya Effect

Sun's image distorted and elongated by atmospheric refraction ©Tim Jones
Sun’s image distorted and elongated by atmospheric refraction ©Tim Jones

A Polar Phenomenon

In May 1915, as Ernest Shackleton and the crew of Endurance entered their fourth month trapped in ice on the Antarctic’s Weddell Sea, the ship’s navigator added to the gloom by declaring the Sun would be absent from the sky for the next seventy days.   You expect this at above 75° South; but then on the 8th of May something strange happened.  The Sun reappeared – several times:

The sun, which had made “positively his last appearance” seven days earlier, surprised us by lifting more than half its disk above the horizon on May 8.  A glow on the northern horizon resolved itself into the sun at 11 a.m. that day.  A quarter of an hour later the unseasonable visitor disappeared again, only to rise again at 11.40 a.m., set at 1 p.m., rise at 1.10 p.m.. and set lingeringly at 1.20 p.m.

Ernest Shackleton, 19151


Shackleton understood the effects of atmospheric refraction, that temperature and density differences can bend light – especially near the horizon.   At sunrise and sunset the disk of the Sun can appear distorted: lengthened or flattened, or displaced from its true position in the sky – where Newton put it.

Endurance in Weddell Sea
Ernest Shackleton made his observations from the Endurance while frozen in the Weddell Sea (the bay top left)

Mariners knew about the phenomenon, and referenced standard refraction tables to correct sextant readings in navigation; but the system broke down below about 6 degrees, where refraction increased rapidly and non-linearly.

How atmospheric refraction can make the Sun visible when it's still below the horizon ©Tim Jones
How atmospheric refraction can make the Sun visible when it’s still below the horizon ©Tim Jones

In this case, as Shackleton recorded in his journal, the Sun was 2 degrees and 37 minutes (2°37′) from its true position, 2 degrees more than any refraction table prediction.  Plotting position from this observation would place the Endurance 120 miles from its actual location.

What Shackleton experienced was an extreme case of atmospheric refraction known as the Novaya Zemlya effect, first reported in 1597 by Gerrit De Veer2 , one of the crew on Willem Barent’s third voyage to discover a north-east passage.  Obliged to hunker down for the polar winter in a safety hut or ‘Het Behouden Huijs‘ built on the Novaya Zemlya island chain north of Russia, De Veer reported the return of the post-winter Sun a whole two weeks before it should have been visible; it was in fact 5°26’ below the horizon.  The same thing happened two days later, the Sun still, by the book,  4° below the horizon.

Novaya Zemlya
Map depicting Willem Barents three voyages to discover a North East Passage, showing the Novaya Zemlya islands (Wikipedia)

novaya1The Novaya Zemlya effect occurs in Arctic regions where tracts of cold air remain uniquely stable over hundreds of kilometers, creating a special instance of a  meteorological temperature inversion.  The distortion, powerful enough to bend light through four or five degrees, can make celestial bodies like the Sun or Moon appear wholly above the horizon when they are physically below it.  (If you imagine looking at the horizon, five degrees is the same as ten Suns or Moons in a row.)

For hundreds of years, Gerrit De Veer’s solar observations, and equally his report of a curiously displaced conjunction of the Moon and Jupiter, were not believed.  They said he must have counted the days wrong, or used the wrong sort of calendar.  It took the corroborating reports of polar explorers like Shackleton and, as recently as 2003, ray-tracing simulations3 using contemporary atmospheric data, to vindicate De Veer fully.

Modern almanacs still include refraction tables. (HM Nautical ALmanac Office)
Modern almanacs still include refraction tables. (HM Nautical ALmanac Office)


Time Travel with Starry Night

I’ve set up my own simulations of the celestial events reported by Shackleton and De Veer using the planetarium software Starry Night.  The program can’t reproduce the ray traced refraction effects modeled by van der Werf et al3 – whose validity I’m not equipped to comment on by the way, but it’s still satisfying to check the published numbers and get a feel for what the events looked like all those years ago.





Shackleton’s Solar Observation

First up, the view from the Endurance in 1915:

View from Weddell Sea (Lat. 75 degree 23 mins S Long. 42 degree 14 mins W) 8th May, 1915, 1:20pm (UT) ©Tim Jones, Starry Night Software
View from Weddell Sea (Lat. 75 degree 23 mins S Long. 42 degree 14 mins W) 8th May, 1915, 1:20pm (UT) ©Tim Jones, Starry Night Software

The horizon terrain here is generic Starry Night; apart from being icy-white, the true horizon would run perpendicular to and cross the graduated white Meridian line at zero (0) degrees.  The green line is the Ecliptic.  Things are clearer for our purposes, if less romantic, if we turn off the daylight effect and fancy terrain and zoom in a bit.  It’s now clear the Sun was below the horizon when Shackleton reported seeing it: i.e. with reference to the Meridian on the left, the Sun looks about two and half degrees below the zero degree mark (Shackleton’s 2°37′):

View from Weddell Sea (Lat. 75 degree 23 mins S Long. 42 degree 14 mins W) 8th May, 1915, 1:20pm (UT). With generic landscape and daylight effect turned off ©Tim Jones, Starry Night Software


Gerrit De Veer’s Solar Observation

Willem Barent’s crew, marooned 300 years earlier at the opposite end of the planet, made their observations from the ‘Behouden Huijs‘ at coördinates 76° 15.4′ North 68°18.6’ East, Novaya Zemlya.  This view from the Huijs at 7 o’clock on the morning of 24th January 1597, shows the Sun was firmly below the horizon when Gerrit De Veer observed it – a whole 5°26′ below (horizon is perpendicular to the zero mark on the white Meridian line, green line is the Ecliptic):

Gerritt De Veer sunrise
View from the rescue hut on (Lat. 76 degree 15.4 mins N Long. 68 degree 18.6 mins W) 24th Jan, 1597, 7:00 am (UT). ©Tim Jones, Starry Night Software


Gerrit De Veer’s Moon-Jupiter Conjunction

The Moon-Jupiter conjunction reported by De Veer physically happened at 0:14 UT on 25th January 1597 (there is a small error in the 0:24 UT time given in the contemporary tables by Scala that De Veer used).   Like astronomers today, De Veer identified the moment of conjunction as the time when a line drawn along the shadow separating light from dark on the moon’s surface, the terminator, pointed directly at Jupiter, as in this photograph I took of the Moon-Jupiter conjunction of 21 January 2012:

Moon and Jupiter, 18:45, 21.01.2012, Los Angeles ©Tim Jones
Moon and Jupiter, 18:45, 21.01.2012, Los Angeles ©Tim Jones

 This is the Starry Night simulation of the De Veer conjunction:

De Veer's moon jupiter conjunction
Moon-Jupiter conjunction, 0:14 (UT) 25th Jan,1597. Location: the rescue hut on (Lat. 76 degree 15.4 mins N Long. 68 degree 18.6 mins W) ©Tim Jones, Starry Night Software

The Moon is barely above the horizon and Jupiter is below it (again, reference the zero on the white Meridian line).

Gerrit De Veer saw this view, but over an hour after it happened: i.e. at 01:27 UT not 00:14 UT.  As van der Werf’s analysis explains, De Veer reported the conjunction at 6 a.m. local time, which was 4:33 hours ahead of UT.  Such was the unbelievable power of the Novaya Zemlya effect to make this happen that few indeed believed it.   De Veer learned about the conjunction from his copy of the Ephemerides of Josephus Scala which gave times for Venice.  Here we pick up the story in De Veer’s own words and the spellings of his 1609 translator William Phillip:

Whereupon we sought to knowe when the same coniunction should be ouer or about the house where we then were; and at last we found, yt the 24 day January was the same day whereon the coniunction aforesaid happened in Venice, at one of the clocke in the night [= 1 in the morning of 25th Jan], and with vs in the morning when ye sun was in the east: for we saw manifestly that the two planets aforesaid approached neere vnto each other, vntill such time as the moone and Jupiter stood ouer the other, both in the sign of Taurus, and that was at six of the clocke in the morning;at which time the moone and Jupiter were found by our compas to be in coniunction, ouer our house..
Gerrit De Veer 1597

Yet ray tracing the scenario 400 years later, with Jupiter two degrees below the horizon and the Moon just above it at  conjunction, shows that atmospheric conditions raised Jupiter’s apparent position disproportionately to that of the Moon.  Moreover, the simulation reproduced what De Veer saw at the time he saw it: a conjunction visible to him at around 02:00 UT.  The ray tracing team made a further minor adjustment for the Equation of Time effect, which brought their estimate of when the conjunction was visible to De Veer as 06:20 local time, which is impressively close to his 06:00.)

Apparent position of Jupiter and the Moon after allowing for atmospheric refraction. Diagram reproduced from analysis by van der Werf et al, 2003 (reference 2)
Apparent position of Jupiter and the Moon after allowing for atmospheric refraction. Moon is double actual size for clarity. Diagram reproduced from analysis by van der Werf et al, 2003 (reference 3)

One More Thing

Although Gerrit De Veer’s vindication now seems complete, there was one little alarm bell went off during my research, and that concerns De Veer’s reference to both the Moon and Jupiter being in the constellation of Taurus at the time of conjunction.  Zooming in to see the 1597 conjunction against modern constellation boundaries puts it well into Aries.  So what gives?

Modern constellation boundaries. Moon-Jupiter conjunction, 0:14 (UT) 25th Jan,1597. Location: the rescue hut on (Lat. 76 degree 15.4 mins N Long. 68 degree 18.6 mins W) ©Tim Jones, Starry Night Software

Maybe the constellation boundaries have changed; let’s have a look at Albrecht Dürer’s beautiful star chart from 1515.  The belly of the bull tucks a little further under the ram than in modern charts, but the conjunction is still firmly in Aries. 

Star chart of the northern skies, Albrecht Dürer, 1515, Nuremberg.
Star chart of the northern skies, Albrecht Dürer, 1515, Nuremberg.

Maybe the Moon made the stars in Aries harder to see that night, so instead De Veer focused on the sparkling Pleiades and Hyades clusters in Taurus; I’d probably do that if I were standing in a freezing Arctic wasteland staring at the sky at six in the morning.  I later discovered Charles Beke4 in a 19th century analysis of the William Phillip translation also noticed the discrepancy.  He points out a retrogression of the equinoctial points – the places where the celestial equator intersects the ecliptic – has since De Veer’s day shifted the positions of the constellations in terms of longitude and latitude relative to those references; but that rather suggests in his write-up De Verre placed the conjunction in whatever constellation the numbers dictated, rather than where he saw it?  Still a bit of a mystery to solve then – at least in my mind.  


  1. E. Shackleton, South: The Story of Shackleton’s Last Expedition 1914–1917, MacMillan, New York, 1920
  2. Gerrit De Veer, The Three Voyages of William Barents to the Arctic Regions (1594, 1595 and 1596). London, 1876 (translation of 1609 original).
  3. Gerrit de Veer’s True and Perfect Description of the Novaya Zemlya Effect, 24-27 January 1597, Siebren Y. van der Werf, Günther P. Können, Waldemar H. Lehn, Frits Steenhuisen, and Wayne P. S. Davidson; Applied Optics, Vol. 42, Issue 3, pp. 379-389 (2003)
  4. Charles T. Beke, The Three Voyages of Willem Barents to the Arctic Regions 1594, 1595 and 1596 by Gerrit de Veer, 2nd ed.William Phillip, trans., Hakluyt Society, London, 1876 (Page 147)


Sun Dogs

A Sun Dog in Surrey (Photo:Tim Jones)
A Sun Dog in Surrey. Sun is on the left, the sun dog is the patch of light to the right (Photo:Tim Jones)

Despite keeping an eye out for strange atmospheric phenomena, my track record is not good, and I count myself lucky to catch the occasional rainbow. Lots of sailing, flying, and mountain walking over the years, with nice low, clear, horizons, and I’ve yet to see the almost mythical ‘Green Flash’.

But yesterday I saw a special type of mini-rainbow: a Sun Dog.

The concentrated patches or spots of light can be very bright, always at the same level of the sun, and always at a 22 degree angle from the sun.

They’re caused by light passing through clouds of ice crystals in the upper atmosphere, typically above 10 km.  Ice crystals are all hexagonal in cross-section, and vary in size and length; but under the conditions that generate a sun dog, the crystals have become aligned in the air flow (because they’ll have a minimum air resistance in a shared direction) so that light passing through them leaves in the same direction: hence the 22 degrees.

I’ve seen photos of sun dogs, and may have seen fainter patches of rainbow that were actually unconvincing sun dogs.  But this one was really bright, like a little sun hanging where it shouldn’t be. You’ll know it if you see one.

And if that’s piqued your interest for atmospheric phenomena, here’s an excellent lecture from Professor of Astronomy at Gresham College, Carolin Crawford, who explains better than I can Sun Dogs (from around 44 mins) and a whole bunch of other effects that I never knew existed.

After watching this lecture again, I think there’s also a bit of Coronae interference scattering visible in my photo: that pink/purple glow near the sun.

Cool Pots

Pots (Photo:Tim Jones)
Historic olla water cooling pots made by Native Americans in San Diego County. Possibly Kumeyaay or Diegueno origin. (Photo:Tim Jones)

Maybe it was the furnace heat of California last month, or the topicality of NASA’s Curiosity landing, but here I am having my first – and almost certainly last – von Däniken moment. 




How else though, aside from some ancient Martian visitation, could Native Americans of centuries past, without the benefit of telescopes or interplanetary probes, design water pots so closely matching the Red Planet?

Well, on reflection, I guess a mixture of clay and cactus juice might just bake out that way in the sun.

Which brings us to the real science behind these earthenware pots.  Because although they may well be over two hundred years old, discovered in 1926 by my wife’s geologist great-grandfather in the desert of San Diego County, these water carrying olla represent nothing less than the world’s first refrigerator.

The larger olla in-situ, San Diego County, 1926, complete with geological hammer for scale. Ollas were not truly ‘fired’, but hardened by baking in the sun (Scan of original photo belonging to Tim Jones)

The water inside the olla reaches a temperature substantially below that of the surroundings thanks to the principle of evaporative cooling – something you can demonstrate to yourself just by licking a finger and waving it around.  The skin feels cooler because the heat needed to turn liquid water molecules in your spit into vapourised water molecules leaving your hand is taken from your skin.  The amount of heat, or energy, needed to change from a liquid to a gas is called the latent heat of evaporation, which for water is 2257 kJoules per kilogram.

Kumeyaay (Wikipedia)

The sun-baked porous clay of the olla acts like a wick, delivering a constant flow of evaporating water to the surface where it quickly evaporates, cooling first the surface and in turn the water inside the pot.

Wondering how effective ollas really are, but with live tests on our delicate pots off the agenda, I turned to theoretical musings and some (not entirely successful) experimentation.


The Theory

The temperature on the pot’s surface, or wet-bulb temperature, is easy enough to calculate if we know the ambient air temperature, relative humidity (how much water is already in it), and local air pressure – as that affects the dew-point temperature at which water changes from liquid to gas.  I got all that info from my local weather station online, and plugged it into one of the many online calculators – like this one at the National Oceanic and Atmospheric Administration (NOAA) – to find the wet bulb temperature. (The exact calculation is complex and explained on the NOAA website, but essentially the drier the air, the lower the wet-bulb temperature; water molecules already in the air decrease the net evaporation rate.)

The day I looked at this, the values were: temperature 34 C, relative humidity 20%, and air pressure 1014.9 millibars, for which the NOAA calculator returned a wet-bulb temperature of about 19 C.  That’s a whole 15 degrees below ambient temperature; modern electric fridges don’t do much better than that (okay – granted they can get to lower absolute temperatures).

Wet-bulb thermometer (Photo:Tim Jones)

The wet-bulb temperature I verified experimentally using a cooking thermometer modified with wet paper-towel stuffed in around the sensor tip (a mercury thermometer would have a bulb of mercury at the end – hence wet-bulb; but this was all I had and works well enough).  Swinging the thing fast round my head on the end of a shoelace simulated wind and, lo and behold, I recorded a wet-bulb temperature of 21C.  Not quite the predicted 19C, but in the right area.

Good ventilation of the olla is necessary as it influences the evaporation rate, and the area for evaporation should be large (the olla’s spherical design is fantastic in this regard as it maximises the area).  The area of non-wetted contact should be small to minimise absorption of heat by conduction from the surroundings – here again, the point contact of the spherical olla is perfect.  Ollas also work better in the shade, to minimise heating by solar radiation.

Calculating how long the contents take to cool is more tricky, requiring an estimate of the evaporation rate from a porous surface.  But we can get some handle on it using an assumed rate of 7kg/ (based on some data I found for swimming pool evaporation rates in Australia of all things), latent heat of evaporation of water 2257 kJ/kg, and heat capacity of water 4.18 kJ/kg.K.  From which I reckon the 0.3m diameter olla, holding 14 litres (=14 kg) of water, needs to lose 878 kJ of heat to fall in temperature by 15 degrees, equal to evaporating 0.4 litres (0.4kg or 3% of the contents) from the 0.28 m2 surface over a 5 hour period.

The numbers aren’t perfect, but suggest in its heyday our olla was up and usefully cooling in a couple of hours.

The Practise

Now for the not-totally-successful experimentation part of the post.

Plant pot evaporative cooler (Photo:Tim Jones)

You can see what I’m trying to do here: my very own plant pot olla.  The physical conditions (temp.,humidity,pressure) were the same as the theoretical calculation; and I’d confirmed a wet-bulb temperature of 22C as described above.  The pot was kind of working too; that dark band in the middle and top is water seeping through the porous terracotta – and it was pretty consistent throughout the experiment.

Plantpot water cooler

Stirring the contents and taking regular measurements indicated a one degree fall over the first two hours.  But then the temperature started to climb again, which suggests the pot was just not porous enough over sufficient area to counter heating by conduction through the non-wetted areas.  A lack of wind won’t have helped – maybe use a fan next time.  At least no one can accuse me of selectively publishing only positive results.

Other Coolers

The Arab Zeer works in a similar fashion to the olla, but consists of two pots separated by wet sand.  Fruit and other perishables can be kept fresh in the central pot.

Pot-in-pot, Zeer type evaporative coolers (Wikipedia)

A modern invention is this Terracooler: an evaporatively cooled terracotta bell-jar placed over food to keep it fresh.

Evaporative cooling in water features is enhanced by an electric pump (Photo:Tim Jones)
Evaporative cooling in water features is enhanced by an electric pump (Photo:Tim Jones)

And keep an eye out for artificial waterfalls used to create a cool atmosphere in public spaces, or the same principle operating in simple garden water features: the water in this one I measured at 24C on a 32C day.

I’m back in the UK now, where typical humidity levels close to 100% (=rain) preclude the extensive program of further evaporative cooling tests this discussion clearly signposts.  If you have more luck with your own ollas though, do let me know.

Huxley and Tyndall, Ill-Prepared Alpinists ?

It’s many years since that winter weekend I met up with friends in the UK’s Lake District National Park, intent on hiking the slopes of Helvellyn.


Helvellyn (Photo: Simon Ledingham, WikiCommons)

We’d arrived in groups from various locations, and it was during the traditional kitting-up ritual, managed out the back of our respective vehicles, that the full realisation of my ill-preparedness struck home.

Confidence in my sturdy boots and fleece failed to counter the sinking dread I felt as my friends systematically bedecked themselves, NASA pre-flight-ops style, with all the latest snow gear.  The thing was, I simply didn’t own, or had neglected to bring, the mittens, over-trousers, goggles, and miscellaneous species of crampons and ice-axe recommended by the now darkening sky.

Just as well I was in the safe invincibility of my early twenties.

Much better...

So off up the hill went we.  Almost immediately it started snowing – gently at first, with a serious deterioration setting in at 2000 feet; a full-blown blizzard now: horizontal snow, near zero-visibility, heavy reliance on compass etc.

I stood clown-like, my gaiterless cotton trousers stiff as boards, the ice caking and cracking as I lifted my legs through the thick snow.  My fingers and face went numb.  Resplendent in Gortex, my fellow hikers peered out from their hermetic cocoons, reflectorised goggles glinting from deep within wind-cheating hoods.  Proffered spare socks were gratefully accepted and fashioned into makeshift gloves.

Then as the storm blew into near total white-out, we made the only possible decision, irrespective of equipment, and turned around.

Had we pushed on, things could have got nasty.  As it was, we’d still managed something of a walk, and I guess I got what I deserved by way of a sound freezing and lesson learned.  You’ve got the picture.

In Good Company

John Tyndall

This mildy embarrassing tale comes to mind because of research I’ve been doing into the history of botany (and science stuff in general) in Wales.

And as it turns out, I’m not the first to show up for a mountain ascent without the proper kit.  What’s surprising perhaps is that, among scientists of the Victorian age, that honour goes to none other than seasoned Alpinist John Tyndall and ‘Darwin’s Bulldog’ Thomas Huxley for their 1860 ascent of – not Helvellyn this time – but Mount Snowdon in North Wales.

Thomas Huxley

Snowdonia was a major stomping ground for botanists in the 18th and 19th centuries, and by the 19th century, professional guiding had become quite a local industry.

In ‘The Botanists and Guides of Snowdonia’, Dewi Jones describes how mountain guide Robin Hughes first met up with Tyndall and Huxley:

Robin Hughes was 61 when he guided John Tyndall, the famous alpine mountaineer and scientist, up Snowdon from Gorffwysfa (now Pen y Pass) in 1860.  Tyndall, despite his Alpine experience, had arrived in the area on a snowy December day rather ill prepared for a winter assault on Snowdon, but they managed to gain the summit despite having to wade through drifts of soft snow.  Tyndall, with his friend Huxley, had brought no ice axes or gaiters with them.  They bought two rake handles at  a shop in Bethesda, while on their way from Bangor to Capel Curig, and had the local blacksmith fit them with rings and iron spikes.  During the ascent Tyndall complained of numbness in the feet as the result of his boots becoming filled with snow due to the absence of gaiters.

So, with all due credit for the last minute improvisations, one still wonders what they were thinking – especially Tyndall.  With Tyndall aged 40 and Huxley 35 in 1860, it’s not like either man could claim the inexperience of  youth.

View down Llanberis Pass from Llanberis (Photo: Tim Jones)
View down Llanberis Pass from Llanberis (Photo: Tim Jones)

A bit more digging suggests Huxley at least was distracted. The Snowdon trip had been arranged by his wife Nettie, with the help of Tyndall, to relieve the depression he suffered at the recent death of their son, Noel.  That Nettie had soon after given birth to another son only added to Huxley’s confusion (Desmond):

[Hal hardly knew whether] ‘it was pleasure or pain.  The ground has gone from under my feet once & I hardly know how to rest on anything again’

Desmond continues:

Nettie…..conspired with Tyndall to get Hal away.  That meant one thing.  In unprecedented Boxing Day frosts, when the thermometer plummeted to -17 degrees, Busk and Tyndall marched him off to the rareified air of the Welsh mountains, reaching Snowdon on 28th December.  The grandeur of it matched ‘most things Alpine. (Busk is George Busk (TJ)).

On 19th December, Huxley had written to his friend Joseph Hooker that he was:

“…going to do one sensible thing, however, viz. to rush down to Llanberis with Busk between Christmas Day and New Year’s Day and get my lungs full of hill-air for the coming session.(The Huxley Letters.)

Llanberis is the village at the base of Snowdon, and Pen y Pass the highest point in the nearby pass.  There’s a pub there now, and in 1860 an inn, where, according to Tyndall, Hughes fueled up with whisky before the trip, [and Huxley doubtless topped off his brandy flask] (Tyndall).

Snowdon Summit - in better weather (Photo:Tim Jones)
Crib Goch, Snowdon (Photo:Tim Jones)
Crib Goch, Snowdon (Photo:Tim Jones)
Snowdon Summit
Snowdon summit. No train or cafe in Tyndall's day

Fifteen years later, writing his book Hours of Exercise in the Alps, Tyndall’s torment on Snowdon was fresh in his mind:

“I had no gaiters, and my boots were incessantly filled with snow.  My own heat sufficed for a time to melt the snow; but this clearly could not go on for ever.  My left heel first became numbed and painful; and this increased till both feet were in great distress.  I sought relief by quitting the track and trying to get along the impending shingle to the right.  The high ridges afforded me some relief, but they were separated by couloirs in which the snow had accumulated, and through which I sometimes floundered waist-deep.  The pain at length became unbearable; I sat down, took off my boots and emptied them; put them on again; tied Huxley’s pocket handkerchief round one ankle; and my own round the other, and went forward once more.  It was a great improvement – the pain vanished and did not return.”

And that’s pretty much the story.  Maybe it’s because I know the territory so well, or just that I’m a big fan of both these guys; but I love the imagery of Huxley and Tyndall spilling out of Pen y Pass with their half-cut guide, then trogging up Snowdon with their frozen feet and rake handles.

Anyway, all this staring at a computer screen is unhealthy; I’m off out.

Now where did I put  those gloves……


Jones, Dewi.  The Botanists and Guides of Snowdonia. Pub. Gwasg Carreg Gwalch (Jun 1996), ISBN-10: 0863813836, ISBN-13: 978-0863813832

Tyndall, J. Hours of Exercise in the Alps. Pub. Appleton and Company 1875 (Tyndall originally described his exploits in the Saturday Review 6 Jan 1861 as ‘The Ascent of Snowdon in Winter‘, but clearly felt the tale was worth re-telling in his Alpine book)

Desmond, Adrian. Huxley The Devil’s Disciple. Pub. MIchael Joseph 1994. pp 289-290.

Jones, G.Lindsay. The Capel Curig Footpaths up Snowdon, A Brief History (link to pdf at

The Huxley File (Charles Blinderman) at Clark University

Clark, R.W. The Huxleys. Pub. Heinemann, 1968. P64

Related posts on Zoonomian

Happy Birthday Thomas Henry Huxley

Fine Words

A Cautious Perspective on the Mystery Missile

You may be aware of the mini-controversy  around what was initially thought to be a ‘mystery missile’ launch earlier this week off the California coast.  This clip sums it up:

The official line now seems to be that it wasn’t  a missile at all, but the vapour contrail from a passenger jet, the sunset and viewing angle making the event look like something it wasn’t. Last time I looked, NASA were reported to be supporting that view based on satellite imagery, and a specific aircraft has been correlated with the event.

The incident reminded me that things are indeed not always as they seem, especially  in the sky around sunrise and sunset.  And to illustrate, I’ve dug out a few pictures – all taken in the last three months.

One thing that really struck me in the mystery missile film was the ‘solidity’ and volume of the plume.  Aircraft contrails are more wispy aren’t they?   But then I looked at this picture I took just before sunrise, which includes a contrail every bit as bushy as the one in the film:

Contrails over Surry, UK (Photo: Tim Jones)
Contrails over Surry, UK (Photo: Tim Jones)

Perspective too is a funny thing.  Take a look at this picture I took of a passenger jet near Heathrow Airport in London just as the sun was setting.

Passenger Jet (Photo: Tim Jones)
Passenger Jet (Photo: Tim Jones)

It’s not immediately obvious, to me at least, whether this plane is coming at me or flying away.  There’s a Gestalt Switch moment when the eyes confuse the rear of the fuselage for the nose end.  Things don’t get much clearer when we zoom in:

Passenger Jet (Photo: Tim Jones)
Passenger Jet (Photo: Tim Jones)

A few seconds later and the setting sun catches the plane’s tail, making the direction of flight more obvious.  At a distance, could such a bright reflection isolated to one part of an aircraft be confused with a rocket nozzle – especially if you’d already got the idea in mind?

Sun reflecting off aircraft tail-fin (Photo: Tim Jones)
Sun reflecting off aircraft tail-fin (Photo: Tim Jones)

It’s easy to be fooled by bright objects catching the sun.  Helium filled toy balloons are favourite UFO candidates.  I’ve more than once rushed into the house for camera and binoculars when something fast and bright has appeared in the sky.  The motion of a rising balloon is very smooth, and viewed from the right angle the mystery object can appear to travel horizontally across the sky faster than it really is.  The last one I saw reminded me of an International Space Station (ISS) pass, only in daylight.  Again, one of the issues I have with the mystery missile film is that I can’t tell how fast the missile / aircraft is moving – vertically or horizontally.

Shiny balloons make for great UFOs (Photo: Tim Jones)
Shiny balloons make for great UFOs (Photo: Tim Jones)

Here’s another example of skyward things not being all they at first seem.  To the naked eye, we see a typical multi-engine passenger jet flying at high altitude.

Aircraft contrail illusion (Photo: Tim Jones)
Aircraft contrail illusion (Photo: Tim Jones)

But with the benefit of a telephoto lens, it turns out to be three (presumably military) jets flying in formation:

Three jets in formation, showing contrails (Photo: Tim Jones)
Three jets in formation, showing contrails (Photo: Tim Jones)

Something else that isn’t clear from the mystery missile footage is the absolute and relative position of the helicopter that took the pictures.  Again, perspective can be confusing.  Take a look at this shot I took looking down on a plane in the clouds.  Obviously I took this from the air, right?

Jet plane against clouds (Photo: Tim Jones)
Jet plane against clouds (Photo: Tim Jones)

Wrong.  I was standing in the local park (and it’s not a hilly region) when I took this.  A bird flying into the frame puts some limits on the likely altitude, but it’s still ambiguous if you don’t see the full context:

Jet plane against clouds (Photo: Tim Jones)
Jet plane against clouds (Photo: Tim Jones)

To finish off, here’s a picture I took only a couple of weeks ago from mountains over-looking Los Angeles and the bay area.  It was twilight, and that lump above LA Downtown is Catalina Island.  Perfect missile-spotting conditions.  Maybe I’ll catch the next one.

View over Los Angeles and out to sea (Photo: Tim Jones)
View over Los Angeles and out to sea (Photo: Tim Jones)

UPDATE 13/11/2010

Comprehensive analysis of this event and discussion of previous missile/aircraft contrail confusions here at

Mountains and Moonbows

What do aurora, noctilucent clouds, sun-dogs, and green flash have in common ?  Answer: they’re all examples of rare and interesting visual atmospheric phenomena I’ve totally failed to observe this summer.

Lunar corona and Lenticular Clouds, Jungfrau Massive (Photo: Tim Jones,

Conditions have often been right, even optimal.  I’ve made repeated observations with sophisticated equipment: my eyes and a camera, but no joy.  The only solace for standing in a field staring at the twilight horizon for nights on end has been the proximity of the local hostelry.  On reflection not such a bad deal.

I’ve had better luck in the past, but more so with the moon than the sun.  Take the example above of a lunar corona in the Swiss mountains.  Snapped between avalanches from an improvised snow-hole during my ascent of the Eiger from the window of the Beau Rivage Hotel in Interlaken.

Lunar coronae are in no way attached to the moon, but are an earthbound visual effect caused by moonlight passing through clouds of small particles.  As it’s a diffraction effect rather than a refraction effect, it works even with particles that don’t transmit light, like pollen grains for instance.   In this case the effect is most likely caused by water droplets in clouds.  The same thing happens with the sun sometimes, the visual ‘corona’ in that case not to be confused with the physical corona that is attached to the sun – so to speak.

Talking of confusion, lunar coronae, or moonbows, are not the same thing as Moon Rings.  I made that mistake when I started writing this piece and subsequently had to change the title.   A Moon Ring is just a name, but it’s a name specifically reserved for a ring of light caused by the refraction of moonlight through high altitude ice crystals.  Because ice crystals are hexagonal in shape, they all refract light at the same angle, which from an observer’s viewpoint produces a ring concentric with the moon at a fixed radius of 22 degrees (for fuller explanation see here).  Measured across the sky, that looks like 44 moons put next to each other (the moon takes up roughly half a degree of the 180 degrees of the sky we can see at any time).  The ring in my picture is at most ten moon diameters from the moon’s disc, or five degrees.  So it ain’t a Moon Ring.

A lunar corona can be more spectacular though, and if the conditions are right, a whole rainbow of colours can spread out from the inner ring, going from red to blue.

On a different tack now….

Apart from the moonbow, this scene includes an almost text-book perfect example of a mountain weather phenomenon known as Mountain Waves and Lenticular Cloud formation.

Lenticular clouds over the Jungfrau Massive by moonlight
Blow-up of the scene above showing moonlit lenticular clouds forming over the Jungfrau Massive (Photo:Tim Jones)

When air is forced to rise by flowing up the side of a mountain, it can cool down sufficiently, to the dewpoint temperature, where water vapour  condenses to form clouds. (That is adiabatic cooling and cloud formation as first explained by Erasmus Darwin. Just sayin’.)  When the air descends on the other side of the mountain, it warms up to above the dewpoint and the cloud disappears, the water drops vapourising again.   The isolated cap left on top of the mountain is a lenticular cloud.

That said, what I think we’re seeing in the photo here is a special circumstance for lenticular cloud formation that I first came across as a trainee private pilot.  In this case, air flowing over the mountains is trapped under a higher layer of stable air, causing standing waves to be set up, with lenticular clouds peeling off the cusps.

Reminiscent of a Katsushika Hokusai painting

The same conditions generate a series of turbulent rotating eddies lower down on the lee side of the mountain which can cause so-called ‘rotor clouds’ or ‘roll clouds’ to form.   It’s best not to fly anywhere near areas of rotating turbulence, so these clouds are good visual warnings for pilots to take special care (although as the mountain wave effect can extend 30 or forty miles downwind of a large range, you’re just as likely to feel the warning).

For a close-up view of a lenticular cloud, here is a lenticular altocumulus I snapped this summer floating off the leeward side of the San Gabriel Mountains in California.  The bulges are caused by rotating air under the cloud.

lenticular cloud formation off San Gabriel mountains in S.California
Lenticular cloud formation (Photo: Tim Jones)

That then about wraps it up for mountains and moonbows.  Just to leave you in the true spirit of transparent open-book research and a view of the laboratory where the Swiss studies were made, complete with proof of location.  And flowers.

Armchair atmospheric physics (Photo: Tim Jones)

Update November 2011 – Here’s another lunar corona; this time with Jupiter and taken from Kingston upon Thames:

Moon with lunar corona and Jupiter
Moon with lunar corona and Jupiter

Of related interest on external sites:

Rare Green Flashes Captured from the Moon (Universe Today)