MODERN RESULTS

Evening Star, Issue 22455, 28 September 1936, Page 12

MODERN RESULTS

STRATOSPHERE QUEST THE GROWTH OF KNOWLEDGE WORK ON COSMIC RAYS Mountain and balloon ascents show that the air gets colder with increasing height, writes the scientific correspondent of the ‘ Manchester Guardian.’ It was long thought that the upward decrease of temperature continued to the top of the atmosphere, but in the early years of the present century this was found to bo untrue. T. de Bert, a French scientist, discovered that tho decrease usually ceases rather suddenly, at a height which over England or France is about seven miles; the height varies by a mile or two, being lower over a cyclonic and higher over an anti-cyclonic area. De Bert called the part of the atmosphere below this level the troposphere, and to the upper part he gave the name stratosphere. Over the Equator the boundary between the two (at 10 miles) is higher than over the Poles (at three or four miles); since_ the .upward decrease of temperature is nearly the same in either case, the temperature of the stratosphere over the Poles, despite the low surface temperature, much exceeds that over the Equator. Indeed, the place of greatest natural cold on the earth is at 10 miles’ height above the Equator, where temperatures of minus 120 deg F. are recorded. DISCOVERED BALLOONS. These facts were discovered by means of very light registering instruments carried to great heights by small balloons. In this country Dines was a leading pioneer in designing such instruments, and during a few days in 1909 and 1910 the University of Manchester, through Schuster and Petavel, sent up no less than 145 of _ Dines’s instruments. At a certain height the balloons burst and the instruments fall to the ground; those finding them receive a reward on returning them to the owner. Since Britain is an island, meteorologists here, as compared with their brothers on the Continent, have unfortunately a distinctly smaller chance of recovering their instruments, which often fall into tho sea. Apart from the loss of instruments, this method of measuring the pressure and temperature of the stratosphere has the drawback that the results are not available for at least a few days after the ascent, so that use cannot be made of them for weather forecasting. In recent years this defect has been overcome by incorporating small radio transmitters with the instruments, which are thus able to transmit their readings almost instantaneously to the ground. Moltohanoff, of Leningrad, was one of the pioneers in the design and use of such radio-meteorographs, and remains an active worker in this field; but perhaps the best instruments of this kind now made are those of V. Vaisala, of Finland, which are a marvel of lightness and ingenuity. The cost—several pounds—is, of course, not negligible, and the, recovery of the instruments is very desirable, but these radio-meteorographs make it possible to observe the conditions in the stratosphere immediately and_ with certainty in polar or desert regions, where an ordinary meteorographj with its precious record, might he unfound for months or years. In recent years it has become possible for man himself, and not merely his instruments, to enter the stratosphere. Piccard’s pioneer stratosphere flight of 1931 has been followed by others from Belgium, Russia, and America. Valuable experience and results have been gained froni such flights, but the great expense involved could almost _ certainly be better laid out otherwise, "so far as concerns the immediate attainment of purely scientific results; the cost of one manned balloon ascent into the stratosphere would pay for a large number of light balloons and registering instruments, with or without radio transmitters. This is illustrated by the success that has attended the researches of Regener, of Stuttgart, who has designed admirable apparatus of moderate cost for the study of both cosmic rays and ozone in the stratosphere. COSMIC RAYS. For several years intense interest has been taken in the cosmic rays, those particles that enter our atmosphere from outside space, with energy far transcending that el any other particles known to us. They are deflected near the earth by the earth’s magnetic field, and are partly absorbed in the atmosphere; they are studied for their own sake, not because of any special importance attaching to their effect on che atmosphere; both in deep lakes and mines, and as far up in the atmosphere as our instruments can reach, scientists desire to observe them, and Regener has achieved conspicuous success in such work, using light balloons. At present Russian scientists are developing cosmic ray records with radio transmitting devices; in Leningrad recently I was privileged to witness one of the first stratosphere flights of such apparatus, under the direction of Vernotf. Tho difficulties and cost of such attempts are as yet considerable, but important results are likely in time to be achieved in this way. In 1934 Regener made brilliantly successful observations of the ozone in the atmosphere by means of a light balloon that ascended to 19 miles.. It carried, besides a barograph and thermograph, a small spectroscopic camera pointing downwards towards a reflecting plate hung below the balloon; the spectrum of the reflected sunlight was recorded photographically at intervals during the ascent and descent (with parachute). It was found that with increasing height the spectrum of sunlight extended further and further into the ultra-violet. LIMITATIONS. Since the spectrum is limited at this end by absorption by atmospheric ozone, it was possible to calculate how much ozone was above the balloon at each stage. It was found that at the top of its flight the balloon had traversed 70 per cent, of the ozone in the atmosphere; moreover, the height distribution of the ozone in the lowest 19 miles agreed well with that found shortly before by a good but complicated method of observation of sunlight

at ground level by certain Swiss and English workers, Gotz, Meet-ham, and D °Another stratosphere problem which is at present receiving much attention in England, as well as in Russia and the United States, is the composition of the air in the stratosphere. Dor over a century many chemists, including Dalton, have interested themselves in this question, but until recently with little success. The composition of the air at ground level, so far as concerns the permanent constituents (excluding water vapour, ozone, and radium emanation), is remarkably constant all over the earth, and the mixing of the air by winds maintains this constancy also throughout the troposphere. At some height in the stratosphere, however, the proportion of the lighter constituents of the air should increase upwards; hence efforts are being made to obtain air samples from as great heights as The amount that can be brought down in a container of moderate size is, of course, small, owing to the rarity of air in the stratosphere. Samples from manned stratosphere balloons have as yet shown no change of composition with height. Small unmanned balloons can go considerably higher, though so far the greatest height from which samples have been obtained with their aid does not exceed 14 miles. An automatic device has to be used to open and close an evacuated yessel at the top of the ascent. There is some evidence for a.slight increase in the helium content of the air at 14 miles height on certain occasions, hut there is need for many more samples, from still greater heights, before we can conclude definitely that in the stratosphere tho air is richer in the lighter gases than near the ground. Somewhat beyond the present range of unmanned balloon ascents_ there is a layer in the stratosphere which can reflect sound downwards, thus enabling big noises (of explosions or heavy gunfire) to be heard, beyond a zone of inaudibility, at distances of 100 miles or so. The reflection is at present generally ascribed to the air becoming hotter at heights of 25 or 30 miles, hotter even than at ground level. An alternative explanation _ recently proposed by a young Russian _ scientist, Efopkin, is that the reflecting layer is not hotter, but lighter, owing to most of the oxygen molecules there being broken up into atoms, of half the weight, by the sun’s ultraviolet light; there may well be at least"'partial truth in this suggestion _ If it is true, the presence of atomic oxygen will add to the difficulty of sending up balloons to those levels, because the oxygen woum actively attack rubber fabrics; but other suitable substances may be found that can withstand the atomic oxygen.