The Science of Discworld Revised Edition

Falcon to stop them.
    Our urge to explore the universe may be just another case of monkey curiosity, but there seems to be a deep impulse that urges us to find new lands to map and new worlds to conquer. Maybe there’s an inbuilt urge to spread out – one leopard can’t eat
all
of you if you spread out.
    It is an urge that has driven us into every corner and crevice of our own planet, from the ice-floes of the Arctic to the deserts of Namibia, from the depths of the Mariana Trench to the peak of Everest. Most of us incline to Rincewind’s view of a comfortable lifestyle and much prefer to stay at home, but a few are too restless to be happy anywhere for very long. The combination is a powerful one, and it has shaped our species into something very unusual, with collective capabilities beyond the understanding of any individual. We may not always use that combination
wisely
, but without it we would be greatly diminished. And it’s offering a real opportunity.
    Even a dream can work miracles. When Columbus (re-)discovered America, and Europe found out that it existed, he was looking for a new route to the Indies. He had convinced himself – on grounds that most scholars at the time found totally spurious – that the Earth was considerably smaller than was generally thought. He calculated that a relatively short voyage westward, from Africa, would lead to Japan and India. The scholars were right, Columbus was wrong – but it is Columbus that we remember, because he made the world smaller. He had the courage to set sail into an empty sea, sustained only by the belief that there was something important on the other side.
    At least we can
see
where we ought to go. Columbus had to back a hunch.
    A dirty great Saturn-V rocket with a tiny Apollo capsule on top was the first practical method for getting out of the Earth’s gravity well altogether. By this we don’t mean that the Earth’s gravitational pull becomes zero if you go far enough away, which is a common misconception: we mean that if you go fast enough, then the Earth’s gravity can never pull you back down. Celestial mechanics operates in the phase space of distance
and
velocity, its ‘landscape’ involves speeds as well as lengths. Only when we understood enough about gravity and dynamics to appreciate this point did we stand any chance of making technology like Apollo work.
    You can see this clearly from earlier suggestions, which were imaginative – in an earthbound sort of way – but fantastic and impractical, at least on Roundworld. In 1648 Bishop John Wilkins listed four possible ways to leave the ground: enlist the aid of spirits or angels, get a lift from birds, fasten wings to your body, or build a flying chariot. If we wanted to be charitable, we could interpret the last two as aircraft and rockets, but Wilkins was clearly unaware that the Earth’s atmosphere doesn’t extend all the way to the Moon. A sixteenth-century engraving by Hans Schaüffelein depicts Alexander the Great carried into space by two griffins – no noticeable improvement. Bernard Zamagna conceived of an aerial boat, and others suggested the use of balloons.
    Every age fantasized about technology that already existed. In Jules Verne’s
From the Earth to the Moon
of 1865 the journey was accomplished by firing a space capsule from a huge gun in Florida; its 1870 sequel
Around the Moon
involved a series of such capsules, forming a space train. Verne got Florida right – he knew that the Earth’s spin produces centrifugal force, which helps the capsule to leave the planet more easily, and he knew that this force was greatest at the equator. Since the protagonists in his book were American, Florida was the best bet. When NASA started launching rockets, it came to the same conclusion, and the space facility at Cape Canaveral was born.
    Big guns have deficiencies, such as a tendency to laminate passengers to the floor because of rapid acceleration, but modern technology does make it possible to avoid this by applying the acceleration gradually. Rockets are currently more practical from the engineering point of view, though that could change. In 1926 Robert Goddard invented the liquid fuel rocket. The first one rose to the dizzy height of 40 feet (12.5 m). Rockets have come a long way since then, taking men to the Moon and instruments to the edge of the solar system. And they are much better rockets. Even so, there ’s something …
inelegant
about heading off the planet