The Science of Discworld Revised Edition

in the ocean at the equator would make more sense. Current construction methods could, in principle, build a 12-mile (20-km) tower.
    The final design problem is how to transport capsules up and down the cable. Whatever method is used, it has to be low on maintenance and high on speed. Magnetic levitation looks good.
    After that, it’s mostly a question of protecting the cable against meteor-strikes and incoming high-energy particles. A piece of cake.
    Having built your space elevator, you’re now in a position to colonize other worlds. The obvious first destination is Mars. You get there in a cloud of small, mass-produced ships, and once you’ve got there one of the first things you do is drop down a cable and build a Martian space elevator. You’re up in orbit anyway, so why not take advantage of the fact? Again, this is the metaphorical aspect of the space elevator: as soon as just one exists, it opens up a vast range of new possibilities. However, you’ll probably need to land a team by some other method in order to construct the complex at the bottom to which the cable will be tethered.
    Mars isn’t a great place to live, so the next step is to terraform it – to make it more earthlike. There are reasonably plausible methods for doing that, detailed at length in Kim Stanley Robinson’s series
Red Mars, Green Mars, Blue Mars
. Mars is no improvement when it comes to meteor-strikes, but at least the colony on Mars is unlikely to get wiped out at the same time as the main population on Earth. Because life is reproductive, if one of them
does
get wiped out, it can quickly be re-colonized from the other. After a few centuries, you’d hardly notice any difference. Still, it may be better to be more ambitious and go to the stars. By the time we’re ready for that, we’ll have interferometer telescopes good enough to spot which stars have suitable planets. The only problem, then, will be to get there.
    There are plenty of suggestions, and we won’t add to them. Think of mid-Victorians predicting life in the 1990s. The dynamic of extelligence is emergent or, to put it another way, we haven’t the faintest idea what we’ll think of next but it’ll probably surprise us.
    One way, if all else fails, is the Generation Ship – a huge vessel that can hold an entire city of people, who live, breed, educate, and die throughout the centuries-long journey. Make it big and interesting enough, and they may even lose interest in the destination. The Discworld almost counts as one of these; it’s on a journey, the inhabitants don’t know where they’re going, the designers have given it a small controllable sun (thus doing away with all those nasty fluctuations) and no less than five bio-engineered creatures positively
delight
in clearing local space of intrusive debris …
    Back on our world, you could take a
really
long-term view and seed the galaxy with genetically engineered bacteria, carefully tailored so that whenever they find a suitable planet they eventually evolve into humanoid life (or life, at least). We would die out, but maybe our fleet of cheap, slow ships might seed a few new Earths somewhere.
    There’s no shortage of ideas. Some might even be practical. The galaxy beckons. We might die trying – but since we’re going to die anyway, why not try?
    And what will we find out there? Will we find a radically different kind of ‘space elevator’, for instance? Well, if there are aliens that live on neutron stars, as Robert L. Forward describes in
Dragon’s Egg
, then they might escape by tilting their world’s magnetic axis, turning it into a pulsar, and surfing its plasma jet. Perhaps all those pulsars were formed in this way. Like any ‘space elevator’, if you can manage the trick once, the rest is easy. The inhabitants of one neutron star managed it, and colonized all the others, founding the Pulsar Empire …
    And since we can envisage new kinds of physical space elevator, there must surely also be new kinds of metaphorical space elevator. Not just aliens a bit like us, but radically different new kinds of life.
    What else could live on a neutron star?
    They’re waiting.

FORTY-SEVEN
YOU NEED CHELONIUM

    ‘ THAT,’ SAID THE Dean, ‘was a very unpleasant business. Good thing we weren’t really there.’
    Rincewind was sitting at the end of the long table, his chin on his hand.
    ‘Really?’ he said. ‘You thought that was bad? Try having a comet land on you. That really makes your