Titanic: A Very Deceiving Night

by Tim Maltin

  “The second explanation, which was first advanced some years ago in an unpublished document, is that CALIFORNIAN did actually see TITANIC but at a very much greater range than her horizon because of abnormal (“super-“) refraction. A note on super-refraction is included in Annex 4 [Below]. In favour of this theory, the phenomenon is variable in its effect and this might explain the apparent movement of each ship as seen by the other when both were in fact stopped. In addition, the rockets seen by CALIFORNIAN were described as low-lying (quoted as rising to less than mast-head height) and this could be because they actually rose to a height above the refracting layer and were seen directly.”

  Annex 4: Extract from The Mariner’s Handbook © The Hydrographer of the Navy

  Part One

  Mirage

  Light does not travel in straight lines in the earth’s atmosphere. It bends according to the density of the air it is travelling through. Normally, the air near the earth is warmer than the air higher up, because air pressure is higher near the surface of the earth and air cools as it expands in the lower pressure of the atmosphere, higher up. This common situation results in standard refraction, where light is bent a normal amount. But when the air near the earth’s surface is unusually hot, such as in the desert or on a hot road, light bends more than normal towards the cooler air higher up. This has the effect of making the sky just above the horizon look like it is on the ground and our brains interpret this as water. Because distant objects appear lower than normal in these conditions, this is called an inferior mirage.

  Diagram of light rays in standard refraction: Diagram of light rays in an inferior mirage:

  These ray-bending diagrams are drawn by Dr. Andrew T. Young of San Diego State University. “Hobs” means “Height of Observer”.

  The most common example of this is the hot road mirage, where there appears to be water on the road ahead, on a hot, dry day:

  Hot road mirage © Physics Department, Warren Wilson College

  Another classic example of this is the desert mirage, which appears like a lake of water in a dry desert, as can be seen in the following photograph by mirage photographer Ed Darack:

  Most people are aware of this type of mirage, but what most people do not know is that the opposite occurs when the surface of the earth is unusually cold, such as over a very cold sea.

  In this situation the air near the surface is colder than the air higher up. Because this is the opposite of the normal thermal situation in the earth’s atmosphere, this is called a thermal inversion. In this situation temperature rises with height and light bends towards the cooler, denser air near the surface, bending it down, around the curvature of the earth.

  This is known as “looming”, which has the effect of making a distant object, such as the coast, appear higher – and therefore seem to be nearer – than it really is:

  Exaggerated diagram of a looming coastline, seen from a ship.

  But where the thermal inversion is so steep that the downward bending of light rays exceeds the curvature of the earth, light becomes trapped in what is known as a “duct”, where escaping light beams are continually bent back down, towards the earth, crossing and re-crossing each other as they go around the earth, trapped in the duct. This is known as a superior mirage, because here objects appear both higher than normal, but also distorted, with objects within the duct becoming inverted – and inverted again and again – each time the rays cross and re-cross each other:

  Dr. Andrew T. Young Superior Mirage Diagram. Note the rays crossing within the grey “duct”. ‘Hobs’ means Height of observer.

  The photograph below is a superior mirage of the coast around the small Swedish village of Höganäs, taken from a boat on the Danish coast, near Osterrenden Bridge. The land seen is therefore 100km away, but it has been lifted up above the horizon and distorted by the superior mirage:

  Swedish coast seen at 100km range due to superior mirage © Captain Peter

  Superior mirages are most often experienced in high latitudes and wherever the sea surface temperature is exceptionally low.

  Titanic’s officers were well aware of abnormal refraction and the phenomenon of looming, as her Second Officer Charles Lightoller explained at the British Inquiry into the sinking:

  “The man may, on a clear night, see the reflection of the light before it comes above the horizon. It may be the loom of the light and you see it sometimes sixty miles away.”

  The opposite of Looming is known as ‘sinking’, where objects which would normally be seen above the horizon are hidden below it. And because light rays bend downwards at different rates, the apparent height of objects seen will differ according to the degree of bending of the light. The vertical stretching of an objects is known as ‘Towering’ and the vertical compression of objects is known as ‘stooping’, as demonstrated in the following series of photographs of the same lighthouse under different thermal conditions, by Pekka Parviainen:

  Looming, Stooping and Miraging lighthouse © Pekka Parviainen

  And because these light rays are bending down and reflected at different rates and points in the duct, they cross over each other, causing very distortive effects, such as can also be seen in this trio of photographs of the same ship, taken by mirage photographer Pekka Parviainen:

  A distorting ship in a superior mirage. © Pekka Parviainen

  The Flying Dutchman

  When light rays cross in miraging conditions, inverted images of a ship can appear above that ship:

  Ship in a superior mirage © Pekka Parviainen

  These strange, distortive effects have been known to sailors for hundreds of years:

  A 19th Century drawing of miraging ships. This drawing is inaccurate as the mirrored images are in fact always the same size as the object being mirrored, in the horizontal direction, and mirages always appear lower in the sky – closer to the horizon – than is shown here.

  The myth of The Flying Dutchman has its basis in miraging and there were many reported sightings in the 19th and 20th centuries. During his late adolescence, in 1880, Prince George of Wales, the future King George V, was on a three-year voyage with his elder brother, Prince Albert Victor of Wales, and their tutor, Dalton. Transferred to HMS Inconstant due to a damaged rudder in their original ship, the 4,000-tonne corvette Bacchante, and whilst off the coast of Australia, between Melbourne and Sydney, Dalton records:

  At 4 a.m. the Flying Dutchman crossed our bows. A strange red light as of a phantom ship all aglow, in the midst of which light the masts, spars, and sails of a brig 200 yards distant stood out in strong relief as she came up on the port bow, where also the officer of the watch from the bridge clearly saw her, as did the quarterdeck midshipman, who was sent forward at once to the forecastle; but on arriving there was no vestige nor any sign whatever of any material ship was to be seen either near or right away to the horizon, the night being clear and the sea calm. Thirteen persons altogether saw her … At 10.45 a.m. the ordinary seaman who had this morning reported the Flying Dutchman fell from the foretopmast crosstrees on to the topgallant forecastle and was smashed to atoms.

  The Flying Dutchman imagined as a pirate ship © Mary Evans Picture Library

  That this phenomenon was in fact a mirage is well-explained in this 19th Century text:

  The news soon spread through the vessel that a phantom-ship with a ghostly crew was sailing in the air over a phantom-ocean, and that it was a bad omen, and meant that not one of them should ever see land again. The captain was told the wonderful tale, and coming on deck, he explained to the sailors that this strange appearance was caused by the reflection of some ship that was sailing on the water below this image, but at such a distance they could not see it. There were certain conditions of the atmosphere, he said, when the sun's rays could form a perfect picture in the air of objects on the earth, like the images one sees in glass or water, but they were not generally upright, as in the case of this ship, but reversed—turned bottom upwards. This appearance in the
air is called a mirage. He told a sailor to go up to the foretop and look beyond the phantom-ship. The man obeyed, and reported that he could see on the water, below the ship in the air, one precisely like it. Just then another ship was seen in the air, only this one was a steamship, and was bottom-upwards, as the captain had said these mirages generally appeared. Soon after, the steamship itself came in sight. The sailors were now convinced, and never afterwards believed in phantom-ships.

  In this photograph by Mila Zinkova, it’s easy to see how even a small sailing boat, mirrored and inverted in a superior mirage, can look like The Flying Dutchman of legend.

  Sea hedges

  Sometimes mirages are easy to spot as they appear like a wall around the sea:

  Superior mirage of islands, photograph by Pekka Parviainen

  But sometimes they appear just like a bank of fog or mist on the horizon:

  Superior mirage of the sea horizon at sunset in San Francisco, photograph by Mila Zinkova

  As Dr. Andrew T. Young, one of the world’s leading atmospheric refraction experts explains:

  “The superior mirage is often associated with an appearance of "fog" at the horizon, because one sees much farther than usual in the mirage strip below the "false horizon””.

  Because air is not completely clear, the more of it you are looking through – i.e. the further you are seeing – the more scattered light you get between you and the object viewed and this is what appears as a haze. This is evident whenever one can see a long way, for example, when viewing a mountain range at thirty miles.

  In fact, as Dr Young goes on to explain:

  “Even perfectly clean air still scatters some light. The molecules themselves, though much smaller than the wavelengths of light, can still scatter a little. But, because the molecules are smaller than the wavelength, they scatter short wavelengths (which are more nearly comparable to the size of the molecules) better than long wavelengths.

  This scattering by particles much smaller than the wavelength was first studied by Lord Rayleigh in 1871. Because he worked out the details of this process, it's generally called “Rayleigh scattering.”

  Rayleigh scattering is the cause of the blue sky: the shortest wavelengths of sunlight (blue and violet) are scattered better than the longer ones, and the average color of the scattered light is the blue of the sky. This color is much more intense than the pale blue of aerosol scattering.

  Because the short wavelengths are selectively scattered, the remaining direct sunlight contains mostly the longest wavelengths: red and orange. That's why the setting Sun looks reddish. This removal of light by scattering is the main component of atmospheric extinction.”

  Because you can see a long way in a mirage and therefore there is a greater depth of air to scatter light, for centuries sailors have confused miraging on the horizon with a bank of fog or haze and the following photographs show very clearly how superior mirages can appear like fog, mist or a haze on the horizon:

  A mirage appears off the shore of Penglai City in eastern China's Shandong Province on Sunday, May 7, 2005. Photo: China Photo Press

  As reported in the Chinese press at the time: “Mists rising on the shore created an image of a city, with modern high-rise buildings, broad city streets and bustling cars as well as crowds of people all clearly visible. Thousands of tourists and local residents witnessed a mirage of high clarity lasting for four hours off the shore of Penglai City in east China's Shandong Province on Sunday”:

  A close-up of a part of the mirage “mist” off the shore of Penglai City in east China's Shandong Province. In fact, though the jumbled mirage image looks like city blocks it is in fact merely the miraging of an ordinary shoreline. It is only our brains which convert this confusing image into an ordered cityscape.

  Photo: China Photo Press

  In his essay, “On the temperature, fogs and mirages of the river St. Lawrence,” published in Transactions of the Literary and Historical Society of Quebec 3, 1–45 (1832), W. Kelly states:

  "There was generally with the mirage an appearance of a fog bank on the horizon …. The air within the horizon was at the same time perfectly clear."

  An early account and drawing of a superior mirage published in Gentleman's Magazine 63, 601–602 (1793) by the Chaplain of the Dunkirk Man of War, the Rev. Samuel Dickenson L.L.B, is called “A Description of a Phenomenon caused by Haze seen at Sea Aug. 10, 1759” and in the account he points out:

  "The term haze, prefixed to the foregoing account, is adopted from the phrase then used by the sailors, perhaps improperly; for, there was not the least appearance of mist or fog, or thickness of atmosphere; on the contrary, the air seemed uncommonly clear."

  As K. D. Billinghurst observed in his 1955 essay “Abnormal refraction, South African waters,” in the Marine Observer 25, 100–101:

  "… what at first appeared to be a fog bank proved to be a mirage. With the coastline on the starboard side, distant 15 miles, a dark-blue mass, having every appearance of land with undulations as of hills, was seen on the port bow from about 4 points to 1 point off the bow where it faded into a white band above the horizon"… the smoke from these whalers and from our own ship did not rise above mast height, but flattened out and hung in the atmosphere in a great band about 100 ft above sea level."

  Similarly, P. Day, P. C. Dyer, and R. P. Swinney, in their 1982 essay “Abnormal refraction, Tasman Sea”, published in the Marine Obs. 52, 26–27, stated:

  "Initially an apparent line of haze or mist was observed, extending from the horizon to an altitude of 0° 10' - 0° 13' and presenting a false horizon. The ship's funnel smoke was then observed trapped on a level with this, indicating an inversion …“

  And in his essay “Abnormal refraction, Western North Atlantic,” published by J.J. Gomez in Marine Observer 35, 122 (1964), he says:

  "… a layer of haze, dark grey in colour and with a clearly defined upper surface, was seen all round the horizon. One ship appeared to be completely inverted and an iceberg which was not visible to the naked eye, seemed to be hanging upside down from the top of the layer."

  In the remarkable thirteenth-century manuscript known as the ‘King’s Mirror’, which contains accounts of Iceland and Greenland that are rational and accurate to a degree not usually found in writings of the time, there is evidence that the Vikings called these apparent fog banks ‘hafgerdingar’ or ‘sea hedges’:

  13th Century Manuscript of ‘The King’s Mirror’. The manuscript belongs to The Arnamagnæan Collection. ©The Arnamagnæan Institute

  “Now there is still another marvel in the seas of Greenland, the facts of which I do not know precisely. It is called ‘sea hedges’ [hafgerdingar], and it has the appearance as if all the waves and tempests of the ocean have been collected into three great heaps, out of which three billows are formed. These hedge in the entire sea, so that no opening can be seen anywhere; they are higher than lofty mountains and resemble steep, overhanging cliffs.”

  In his book about his whaling voyage to the Greenland Sea in 1822, William Scoresby Jr (1823: 163) provided fascinating descriptions of many mirages. On 16 July, when he calculated his position to be 72°33 N, 19°9 W, his ship was in the Greenland Sea about 100 km (62 miles) off the Greenland coast. In his account of ‘the optical phenomena of unequal refraction,’ he described a striking mirage that he observed that day:

  ‘At one period (about 10 PM of the 16th) the phenomenon was so universal, that the space in which the ship navigated seemed to be one vast circular area, bounded by a mural precipice, of great elevation, of basaltic ice.’ On page 169 of his book, he summarised several of his observations: ‘…it [the sea ice] presents the appearance of a vast amphitheatre, which is so disposed, that every observer, whatever may be his position, imagines himself to be in the centre of it.’

  William Scoresby

  Although Scoresby appears to have had no knowledge about the King’s Mirror, his description immediately brings to mind the hafgerdingar.

&n
bsp; As J. Pilling and D. L. Smith observed in their essay “Abnormal refraction, South Australian waters”, published in the Marine Observer 34, 18–19 (1964):

  "… the horizon appeared to become raised above the sea and separated from it by an indistinct misty band… the appearance was that of a bank of fog."

  Here’s another example of a mirage appearing like a slight haze on the water:

  In this photograph a superior mirage appears like a haze on the horizon © Wim van Bochoven 2002, the Netherlands.

  This photograph was taken in Norway in the Spring, the same season and similarly high latitude in which Titanic sank and when superior mirages are most common: the water still has the chill of winter, but the air is warming up; Wim noted when he took this picture that it had been warm during the day and Titanic’s survivors noted that the weather had been sunny on the day of the collision. The air was also calm, as it was the night the Titanic sank: no wind to mix the cold air next to the ocean with the warm air overlying it.