Not until we have taken a look into the future shall we be strong and bold enough to investigate our past honestly and impartially.
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Chapter Two - When Our Space-Ship Landed On Earth ...
Jules Verne, the grandfather of all science-fiction novelists, has become an accepted writer. His fantasies are no longer science-fiction and the astronauts of our day travel round the world in 86 minutes, not 80 days. We are now going to describe what might happen on an imaginary journey by space-ship, yet this imaginary journey will become possible in fewer decades than the time it took to contract Jules Verne's crazy notion of a journey round the world in 80 days to a lightning journey of 86 minutes. But let us not think in terms of such short periods of time! Let us assume that our space-ship will leave the earth for an unknown distant sun in 150 years' time.
The space-ship would be as big as a present-day ocean liner and would therefore have a launching weight of about 100,000 tons with a fuel load of 99,800 tons, i.e. an effective pay load of less than 200 tons.
Impossible?
Already we could assemble a space-ship piece by piece while in orbit round a planet. Yet even this assembly work will become unnecessary in less than two decades, because it will be possible to prepare the giant space-ship for launching on the moon. Besides, the basic research for the rocket propulsion of tomorrow is in full swing. Future rocket motors will mainly be powered by nuclear fusion and travel at nearly the speed of light. A bold new method, the feasibility of which has already been shown by physical experiments on individual elementary particles, will be the photon rocket. The fuel carried on board the photon rocket enables the rocket's velocity to approach so close to the speed of light that the effects of relativity, especially the time dilation between launching site and space-ship, can operate to the full. The fuel supplies will be transformed into electro-magnetic radiation and ejected as a clustered propulsive jet with the speed of light. Theoretically a spaceship equipped with photon propulsion can reach 99 per cent of the speed of light. At this speed the boundaries of our solar system would be blasted open!
An idea that really makes the mind reel. But we who are on the threshold of a new age should remember that the giant strides in technology which our grandfathers experienced were just as staggering in their day: the railways, electricity, telegraphy, the first car, the first aeroplane. We ourselves heard music in the air for the first time; we see colour TV; we saw the first launching of space-ships and we get news and pictures from satellites that revolve around the earth. Our children's children will go on interstellar journeys and carry out cosmic research at technical faculties in the universities.
Let us follow the journey of our imaginary space-ship, whose goal is a distant fixed star. It would certainly be amusing to try to imagine what the crew of the space-ship did to kill time on their journey. Because however vast the distances they covered and however slowly time might crawl along for those left behind on earth, Einstein's theory of relativity still holds good. It may sound incredible, but time on board the space-ship travelling barely below the speed of light actually passes more slowly than on the earth.
If the space-ship travels at 99 per cent of the speed of light, only 14-1 years pass for our crew on their flight in the universe, whereas 100 years go by for those who stay at home. The difference in time between the space travellers and the people on earth can be calculated by the following formula, given by the Lorentz transformations:
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[Insert pic p023]
(t = spacet-travellers' time, T=time on earth, v= speed of flight, c= speed of light).
The speed of the space-ship's flight can be calculated by the bask rocket equation worked out by Professor Ackeret:
[Insert pic p023a]
(v — velocity, w = speed of jet, c = speed of light, t = fuel load at launching).
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At the moment when our space-ship is approaching the star which is its target, the crew will undoubtedly examine planets, fix their position, undertake spectral analyses, measure forces of gravity and calculate orbits. Lastly they will choose as landing-place the planet whose conditions come closest to those of our earth. If our space-ship consists solely of its pay load after a journey of shall we say eighty light years, because all the energy supplies have been used up, the crew will have to replenish the tanks of their space-craft with fissionable material at their goal.
Let us assume, then, that the planet chosen to land on is similar to the earth. I have already said that this assumption is by no means impossible. Let us also venture the supposition that the civilisation of the planet visited is in about the same state of development as the earth was 8,000 years ago. Of course, this would all have been confirmed by the instruments on board the space-ship long before the landing.
Naturally our space travellers have also picked on a landing site that lies close to a supply of fissionable matter. Their instruments show quickly and reliably in which mountain ranges uranium can be found.
The landing is carried out according to plan.
Our space travellers see beings making stone tools; they see them hunting and killing game with throwing spears; flocks of sheep and goats are grazing on the steppe; primitive potters are making simple household utensils. A strange sight to greet our astronauts!
But what do the primitive beings on this planet think about the monstrosity that has just landed there and the figures that climbed out of it? Let us not forget that we too were semi-savages 8,000 years ago. So it is not surprising when the semi-savages who experience this event bury their faces in the ground and dare not raise their eyes. Until this day they have worshipped the sun and the moon. And now something earthshaking has happened: the gods have come down from heaven!
From a safe hiding-place the inhabitants of the planet watch our space travellers, who wear strange hats with rods on their heads (helmets with antennae); they are amazed when the night is made bright as day (searchlights); they are terrified when the strangers rise effortlessly into the air (rocket-belts); they bury their
