October 30 1964 - The Earth seen from space

In October 1964 the Soviet vehicle Voskhod went into orbit round the Earth. Its captain was Colonel Vladimir Komarov, who later lost his life when his space-craft came down out of control, so that there is bound to be a certain sadness when reading of his earlier, successful flight.

It was in late 1964 that the space programmes seemed to be gathering momentum, and there was speculation as to what the Earth would look like if it could be seen from a great distance. I discussed this with K. H. Fea, of the Space Research Group at University College, London, and we showed some of the current photographs. Since then, of course, the Earth has been photographed by the U.S. Orbiter vehicle, which was then in the region of the Moon ; and the results are very much as had been anticipated.

The first manned space-flight took place on 12 April 1961, when Yuri Gagarin made a single circuit of the Earth in the original ' Vostok' craft, landing after a flight lasting for less than two hours. Since then other men and one woman have been into space.

The flight of the Soviet vehicle 'Voskhod' (Sunrise) was made on 12-13 October 1964. In many ways it represented a distinct ad­vance, even though it was of comparatively short duration. The ship carried a crew of three men, of whom only one (Vladimir Komarov) was a true 'astronaut'; of the others, Konstantin Feoktistov was a scientist, while Boris Yegorov was a doctor. In view of the potential hazard due to radiations in space, there was every reason to send up a medical man, and Yegorov's findings will be of particular interest and importance when they are made known in full.*

The 'Voskhod' made sixteen orbits and landed safely, ap­parently in the position intended. It made a 'soft' descent; on this occasion the crew members were not separated in ejector- seats, so that the procedure seems to have been similar to that which will have to be adopted for a landing on the Moon. It has been stated that the ship could well be used for a further trip, and that it is totally undamaged. There have been suggestions that the flight was terminated prematurely, and that the astronauts received a heavier "dose of radiation than had been expected; however, the Russians say that this is not the case, and that the 'Voskhod' was not intended to stay aloft for more than the actual period of twenty-four hours seventeen minutes.

It is worth noting, too, that on this occasion the astronauts wore normal clothes instead of space-suits. Food included roast beef, which was sliced and vacuum-packed in polymer film; slices of filleted Caspian roach, and even caviar sandwiches. Communications with the space-craft were excellent throughout, and the Russians claim, no doubt justifiably, that the whole flight was an unqualified success.

The altitude of the 'Voskhod' ranged between 110 and 255 miles, which meant that the crew members could see over large portions of the Earth. During the first orbit they have related how they saw the forests of Siberia; when passing over darkened Australia they looked at the lights of the great cities, while Antarctica was distinguished by its white ice-cap. Of particular interest was their description of what may be called 'cosmic dawn'. Since the revolution period of the space-ship was only just over ninety minutes, a total of fifteen 'dawns' was observed during the trip, and Yegorov's own description is worth repeating:

The atmosphere brightens. It grows yellow, then darkens again, after which appears the blue halo. Then an orange strip appears, which becomes brighter and brighter. At last the edge of the Sun comes into sight, and suddenly it is clear, like a brilliant red oval. Its brightness increases quickly, since sunrise in outer space lasts for only a few seconds . . . The Moon looks the same as it does from the Earth, the only difference being that the sky around is absolutely black.

A display of aurora australis was also observed.

All this is in agreement with the descriptions given by earlier Soviet and United States astronauts. Even before Gagarin's pioneer flight, photographs of the Earth had been obtained from unmanned rockets, and were clearly of great importance to geophysicists, geologists, and meteorologists, as well as to those engaged in pure space research. No photograph of the Earth as a complete globe has yet been obtained, since this would mean travelling out a distance much greater than a couple of hundred miles; but at least the curvature of the Earth's surface has been clearly shown on many pictures, together with the completely dark sky.

Cloud coverage is, of course, variable - but over wide areas it often obscures the surface detail completely. The absence of cloud over the Tibet region during the flight of Gordon Cooper, on 15-17 May 1963, led to some really spectacular pictures, taken with a hand-held camera through the transparent window of the space-craft, the fourth manned Mercury capsule. When the photographs were taken Cooper was moving at an altitude of over 100 miles above the Tibetan plateau.

Lakes show up with particular clarity, as dark patches - apart from the shallower ones, which were partly covered with ice. Some of the hills were also capped with ice and snow, and identi­fication presents no difficulty. Other photographs taken by Cooper showed the glaciers and snow-masses of the Himalayas, and have been of considerable value to map-makers and geologists. Ice floes drifting near the coast of north Russia have been recorded on photographs taken from the various Soviet space-craft, pre­sumably also with hand-held cameras; and it has been suggested that useful duties could be performed in ice patrolling. In any case, there can be no doubt about the value of the pictures sent back by the unmanned meteorological satellites of the American Tiros series, most of which are taken from 500 miles or so. On one of them, obtained from 400 miles, Great Britain is well shown; England and Wales are covered by 'fair-weather' cumu­lus clouds, and appear bright, since clouds are more reflective than clear ground. On this particular photograph Ireland seems to be covered with high cirrus cloud; a low-pressure system is approaching from the Atlantic, indicating the probability of bad weather in the near future.

Hurricanes and cyclones have also been photographed from the Tiros satellites, and the circulations of these systems - clock­wise in the southern hemisphere, anti-clockwise in the northern - have been evident. Violent storms of this sort have often been photographed in their early stages, so that people living in the danger zones have been given ample warning. There seems little doubt that a full-scale 'storm patrol' by means of satellites will be in operation within the next decade.

However, all the Earth photographs so far obtained have been taken from comparatively close range, and it is interesting to speculate about what our world would look like when seen from much greater distances. Seen from the Moon, the Earth would be magnificent indeed. Its light would be much more brilliant than full moonlight at home, partly because the Earth would appear considerably larger in the lunar sky and partly because it is a better reflector of sunlight. Its albedo, or reflecting power, has been estimated as almost 40 per cent, which compares very favourably with the 7 per cent of the Moon. Indeed, the Moon has an albedo lower than that of any other sizable body in the Solar System, with the possible exception of the remote planet Pluto.

Of course the Earth would show phases to a lunar observer. It would be full at midnight, and for protracted periods it would be a glorious object; the Moon rotates much more slowly than the Earth, so that a lunar night (that is to say, the time during which the Sun would be below the horizon) amounts to almost two of our weeks. At lunar noon the Earth would be new, and its dark side would be turned moonward. In point of fact, the Moon's rotation period is equal to its period of revolution around the Earth. This means that the Moon keeps virtually the same face turned towards the Earth, and the averted side remained unknown until a large part of it was photographed by the Russian rocket 'Lunik III' in October 1959. It also means that the Earth would seem to stay almost still in the lunar sky; it would not rise or set, and would always appear in virtually the same position, though it would admittedly oscillate slightly. From the averted hemisphere of the Moon, the Earth would never be seen at all, and the nights would be consequently much darker.

The Moon is only about a quarter of a million miles away, and the Earth would therefore appear as a relatively large object in the sky, but things would be very different for Mars, which never comes much within 35,000,000 miles of us. To a Martian observer, the Earth would show up as nothing more than a very brilliant 'star', probably bluish in hue. It would appear as an inferior planet, best seen in the west near sunset or in the east near sun­rise. This is how Venus actually appears to us, but there would be one important difference. Venus has no satellite; from Mars, our Moon would be a conspicuous object when seen with the naked eye. Telescopically, our hypothetical Martian would be able to see considerable detail on the Earth. The outlines of con­tinents and oceans would be obvious, and the variable cloud cover would be followed. Maps of Earth could be drawn up, though small details would naturally be lost.

Venus may approach us to within 25,000,000 miles, so that it comes considerably closer than Mars, but so far as we can tell the planet's cloudy atmosphere would preclude any visual obser­vations; even the Sun would not be seen, though its position would be indicated by the brightening of the sky. But for this, the Earth seen from Venus would be extremely brilliant, particularly as it would be a superior planet and would be visible against a really dark background.

From greater distances the Earth would fade rapidly into inconspicuousness. From Jupiter it would be hard to see at all, partly because of its smallness but mainly because it would keep very close to the Sun in the sky. And from Pluto, the outermost member of the Sun's family of planets, the Earth would be hope-lessly lost. Pluto moves at a mean distance of over 3,600,000,000 miles from the Sun, and would be a very poor site for carrying out observations of the other planets; only Neptune would be at all conspicuous. A hypothetical Plutonian astronomer would never be able to detect the Earth, and could have no knowledge of its existence. If this is so, then it would clearly be impossible to observe the Earth from the distance of even the nearest star, which lies at roughly 25 million million miles - over four light- years. No telescope of the sort that we ourselves could construct would be powerful enough, as a moment's consideration will show.

The Sun is a star, but by no means a particularly luminous one. It is average in size and luminosity, and only to its nearest stellar neighbours would it be at all conspicuous. Even Sirius, the brilliant star which is so prominent in our winter skies, is officially ranked as a dwarf even though it has twenty-six times the Sun's luminosity. It lies at a distance of eight and a half light-years, or roughly 50 million million miles; to a Sirian observer, the Sun would be invisible with the naked eye, and to detect the Earth, which is not only very small but is also inherently non-luminous, would be an obvious impossibility.

There is every reason to suppose that planetary systems are common in space, and there are a few cases of relatively nearby stars which seem to be attended by planetary bodies. The most interesting example is that of Barnard's Star, which is a red dwarf much less massive than the Sun. Here the companion seems to have only two and a half times the mass of Jupiter: this is much too low for a star, and so the body is presumably a planet, though we have no definite proof. Yet it is invisible, and it has been tracked down only because it produces minute irregularities in the motion of Barnard's Star itself. Were its mass as low as that of the Earth, it would cause no observable effects, and so it would remain unknown. In fact, we can never hope to detect Earth-like planets of other stars unless we can develop instruments very much more sensitive than those available to us at present.

Space research has made amazing progress during the last few years, and further spectacular developments may be expected in the near future, but we must always keep our sense of propor­tion. So far as rocketry is concerned, our range is limited; our Solar System is a very small part of the universe, and it would be misleading to suppose that it is of any real importance. To astro­nomers living in other planetary systems - if they exist, as surely they must - even the Sun will be obscure, and from a distance of only a few light-years the Earth will fade into total insignificance.