Will We Hear The Atom Bomb Explode?

New Zealand Listener, Volume 14, Issue 347, 15 February 1946, Page 16

Will We Hear The Atom Bomb Explode?

OME time between May and July of this year, according to the cables, an atomic bomb will be. dropped on a fleet of captured and obsolete warships in the atoll of Bikini, in the Marshall Islands. The object of the experiment is to determine the effect of the new weapon upon sea-power, but that it will have other and more immediate effects is, of course, obvious. Already arrangements are being made to remove the inhabitants of neighbouring islands to places of safety, and elaborate precautions will even be necessary to safeguard the cameras and instruments strategically placed to record the phenomenal disturbance. But how far-reaching will be the purely physical effects of such an explosion? If the type of bomb used materially exceeds in power those used’ in New Mexico, Hiroshima, and Nagasaki, there is only one event in recorded history of comparable physical significance, namely, the explosion of the volcanic island of Krakatoa, in Sunda Strait, on the morning of August 27, 1883. Many still living rémember that titanic eruption, but to many others the name Krakatoa means nothing at all. Here, in brief, is what happened. Krakatoa, which was a small island, lay in the strait which separates Sumatra from Java." Some time before recorded history it was part of a large volcanic cone, but the top of the mountain was apparently blown away in some early cataclysm, leaving an irregular ring of small islands. The most important of these (Krakatoa or Krakatau) was 2,600 feet high and had a long recorded history of activity About 1877, however, earthquakes began to be frequent in the Sunda Strait area and in 1883 Krakaé@a broke out in violent eruption. This activity began in May, great quantities of pumice and dust being discharged, with all the usual accompaniment of explosions and earthquakes. On August 26 began even more intense paroxysms, which lasted until the morning of Atigust 28. The four most violent took place on the morning of the 27th; when the whole northern and lower portion of the island was blown away. By August 28, instead of the previous volcanic island — which seems to have had an area of 18 square miles-there was left only the hollow stump of a mountain, and with its bottom more than 1,000 feet below sealevel. So much for the effect of the eruption in the immediate vicinity. New Islands Appeared Surrounding islands had ‘their forests buried — and their area materially increased by the masses of material ejected from the volcano, and new islands. appeared in the sea. But the explosion 1tself produced disturbances far exceeding in extent any in the memory of man. A gigantic air-wave, or atmospheric oscillation, emanating from Krakatoa passed over the surface of the globe, as the ripples circle outwards when a stone is thrown into a still pool. But

once the air-wave had become a Great Circle, at 180 degrees from its point of origin, it progressively diminished towards the antipodes of Krakatoa, in the vicinity of Venezuela. From that point the disturbance reflected, or reproduced itself, and then returned to Krakatoa, This repetition was observed no fewer than seven times at many observatories and weather stations throughout the*world. The initial wave was recorded at Dunedin at 9.0 am. (New Zealand time) on August 27, and others were recorded on the barograph there up to September 3.*Wellington recorded the first wave at noon on the 27th and the last wave one hour after Dunedin did. It was observed in its various phases at scores of other points, including South Georgia, Mauritius, Shanghai, Tiflis, St. Petersburg, Berlin, Kew, Milan, New York, and Mexico. Sounds Like Gunfire More amazing even than the atmospheric disturbances was the distances at which the actual sounds of eruption were heard. They were heard distinctly all over Sumatra and Java, to the north as far as Southern Burma, eastward to Dutch New Guinea and half across Australia to Alice Springs. But cartied south-west of Krakatoa into the area of the Trade Winds, the thunder of the eruption rolled 3,000 miles to Rodriguez, three-quarters of the way across the Indian Ocean. In countless harbours, the sounds"like heavy gunfire’-were interpreted as signals of distress. From Singapore two steamers were sent out to search for stricken ships and other vessels put out from ports in areas as far apart as Timor, the Andaman Islands, and Macassar. The submarine telephone cable linking Singapore with the mainland was so affected during the course of the disturbances that it could not be used, as every time a receiver was lifted "a roar as of a waterfall" drowned any possibility of conversation. Gigantic Waves Far more serious were the effects of the explosions on the waters of the ocean. A succession of great waves was generated, some long, others shorter and higher, occasionally merging one with the other. Thirty-three miles away, at Meerak, at the head of a funnel-shaped strait, the height of the wave which swept round the coasts of Java and Sumatra on August 27 was variously estimated at 100-125 feet. There, how-. ever, the waters were constricted; and the greatest height reached by a combination of waves in open water was estimated -at about 50 feet. That was sufficiently high, however, to cause enormous destruction round the neighbouring coasts, where more than 36,000 people perished. Vast distances were covered by the long waves moving outward from Sunda Strait. Three thousand miles away at Rodriguez the sea-level was reported to have risen 5ft. 1lin. with a 10-knot current setting strongly westward. Driving southward through the Indian Ocean, then east around the south coast of (continued on next page)

(continued trom previous page) Australia, the giant ripple lapped the shores of South America and passed northward through the Atlantic, before fading to nothingness. New Zealand seems to have missed this phenomenon. It is true that at Thames on August 30 of that strange year an ebbing tide turned suddenly to flood and flowed past the lighthouse like a mill-race for half-an-hour, and strange marine disturbances were reported elsewhere in New Zealand, but the verdict of science was that these happenings had local causes. The long waves, however, were recorded beyond any doubt at San Francisco (10,440 miles from the. origin), Cape Horn (7,818), Colon, on the Atlantic side of the Panama Isthmus (11,470), Devonport, in the south of England (11,040), Honolulu (8,390) and South Georgia, where a German scientific expedition was stationed (6,676). Green Suns and Blue Moons The least harmful and the most persistent of the phenomena which followed the eruption were the brilliant afterglows and sunsets which lasted long after the volcanic activity had subsided. Great quantities of dust and pumice ash thrown into the air by the volcano blotted out the sky at Batavia, 100 miles away, while the eruption was in progress, but within six weeks the finer dust particles, thrown 17 miles up into the stratosphere, had been dissipated over almost the entire globe, being carried westward at more than 70 m.p.h. The Report of the Krakatoa Committee of the Royal Society, published in London in 1888, included coloured lithographs showing the various types of sunset and afterglow observed at the time, and these vary from delicate pale-~ yellow effects to deep angry crimsons. In fact, the superstitious in all lands must have had an innings such as they

had not enjoyed since the heavens blazed with portents of Caesar’s doom. In. the tropics the sun turned green in colour at some stages, at other times it appeared circled by a halo of red. Blue moons were as common for a time as green cheeses. % % * All that happened more than 60- years ago. If, as United States publicity suggests, the waves which follow the explosion of the atom bomb at Bikini reach a height of 100 feet at the point of origin they will be just twice as high as those recorded in 1883. Provided that the bomb lands inside the shelter of the atoll barrier, however, it is probable that the disturbance of the sea itseif will be restricted to the experimental area. The waves from Krakatoa moved far because they had their genesis in an area where the sea was open-and deep. In all probability, the anchorage selected for the experiment is shallow’ enough to avoid the dangers which might follow the displacement of a large body of water by the downward thrust of the explosion. It is possible that the bomb will generate an atmospheric wave strong enough to be recorded on meteorological instruments as far away as ours are, but hardly likely that we -will experience a gale from the north. And though we are as close to the Marshalls as Rodriguez was to Krakatoa, we have no Trades to carry the reverberations to our ears. Not that we won’t all hear it in our hearts, for the concussion may well shake men in every land beneath the sun. But there may be a consolation prize for us. It is encouraging to dwell on the possibility that when the Nagato and the Prince Eugen and the rest have been vaporised to the satisfaction of the select company of observers, their dust may penetrate the stratosphere and bring to more common mortals the delight of green and red suns, blue moons, and-perhaps-a refulgent afterglow.

J.

M.