38. A Place of Silent Storms
(Extract from Professor Martin Sessui's address, on receiving the Nobel Prize for Physics, Stockholm, 16 December 2154.)
Between Heaven and Earth lies an invisible region of which the old philosophers never dreamed. Not until the dawn of the twentieth century – to be precise, on 12 December 1901 – did it make its first impact upon human affairs.
On that day, Guglielmo Marconi radioed the three dots of the Morse letter “S” across the Atlantic. Many experts had declared this to be impossible, as electromagnetic waves could travel only in straight lines, and would be unable to bend round the curve of the globe. Marconi's feat not only heralded the age of world-wide communications, but also proved that, high up in the atmosphere, there exists an electrified mirror, capable of reflecting radio waves back to earth.
The Kennelly-Heaviside Layer, as it was originally named, was soon found to be a region of great complexity, containing at least three main layers, all subject to major variations in height and intensity. At their upper limit they merge into the Van Allen Radiation Belts, whose discovery was the first triumph of the early space age.
This vast region, beginning at a height of approximately fifty kilometres and extending outwards for several radii of the Earth, is now known as the ionosphere; its exploration by rockets, satellites and radio waves has been a continuing process for more than two centuries. I should like to pay a tribute to my precursors in this enterprise – the Americans Tuve and Breit, the Englishman Appleton, the Norwegian Størmer – and, especially, the man who, in 1970, won the very award I am now so honoured to accept, your countryman Hannes Alfvén…
The ionosphere is the wayward child of the sun; even now, its behaviour is not always predictable. In the days when long-range radio depended upon its idiosyncrasies it saved many lives – but more men than we shall ever know were doomed when it swallowed their despairing signals without trace.
For less than one century, before the communications satellites took over, it was our invaluable but erratic servant – a previously unsuspected natural phenomenon, worth countless billions of dollars to the three generations who exploited it.
Only for a brief moment in history was it of direct concern to mankind. And yet – if it had never existed, we should not be here! In one sense, therefore, it was of vital importance even to pre-technological humanity, right back to the first ape-man – indeed, right back to the first living creatures on this planet. For the ionosphere is part of the shield that protects us from the sun's deadly X-ray and ultra-violet radiations. If they had penetrated to sea level, perhaps some kind of life might still have arisen on earth; but it would never have evolved into anything remotely resembling us…
Because the ionosphere, like the atmosphere below it, is ultimately controlled by the sun, it too has its weather. During times of solar disturbance it is blasted by planet-wide gales of charged particles, and twisted into loops and whirls by the earth's magnetic field. On such occasions it is no longer invisible, for it reveals itself in the glowing curtains of the aurora – one of Nature's most awesome spectacles, illuminating the cold polar nights with its eerie radiance.
Even now, we do not understand all the processes occurring in the ionosphere. One reason why it has proved difficult to study is because all our rocket and satellite-borne instruments race through it at thousands of kilometres an hour; we have never been able to stand still to make observations! Now, for the very first time, the construction of the proposed Orbital Tower gives us a chance of establishing fixed observatories in the ionosphere. It is also possible that the Tower may itself modify the characteristics of the ionosphere – though it will certainly not, as Dr. Bickerstaff has suggested, short-circuit it!
Why should we study this region, now that it is no longer important to the communications engineer? Well, apart from its beauty, its strangeness and its scientific interest, its behaviour is closely linked with that of the sun – the master of our destiny. We know now that the sun is not the steady, well-behaved star that our ancestors believed; it undergoes both long and short-period fluctuations. At the present time it is still emerging from the so-called “Maunder Minimum” of 1645 to 1715; as a result, the climate now is milder than at any time since the Early Middle Ages. But how long will this upswing last? Even more important, when will the inevitable downturn begin, and what effect will this have upon climate, weather and every aspect of human civilization – not only on this planet, but on the others as well? For they are all children of the sun…
Some very speculative theories suggest that the sun is now entering a period of instability which may produce a new Ice Age, more universal than any in the past. If this is true, we need every scrap of information we can get to prepare for it. Even a century's warning might not be long enough.
The ionosphere helped to create us; it launched the communications revolution; it may yet determine much of our future. That is why we must continue the study of this vast, turbulent arena of solar and electric forces – this mysterious place of silent storms.