Humans have begun to transform the Earth. We have built cities, transport networks and power stations, and sprinkled the skies with satellites. If we extrapolate this ability to engineer our own environment – for living space, travel, energy and communications – where does it lead us? Could we transform space too?
Predicting the far future is a fool’s game. So let’s take the usual dodge and say: unless something is forbidden by known physics, it will be done. Eventually.
Before we start, let’s invent two things: self-repairing AI supervisors that can direct projects lasting many millennia; and vehicles that can reach close to the speed of light, maybe riding on laser beams or driven by miniature black holes – which according to recent calculations by physicists at Kansas State University .
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Thus tooled up, we could hop from solar system to solar system, sweeping across the galaxy in 10 million years or so, and then out into our local supercluster of galaxies. So the potential building site is quite spacious.
Such a civilisation would consume lots of energy, and that is where our engineering may be most conspicuous. One option will be to plug in to local power sources, such as harnessing starlight with orbiting solar power stations. As demand for power grows, lots of these could be arranged to obscure a star completely, forming a closed “Dyson sphere“, named after physicist Freeman Dyson, who pointed out that technological civilisations tend to use ever-escalating quantities of energy.
If we built one we would darken the sun and leave a vast archaeological ruin in the event of our demise. Today, Earthly astronomers are looking for the darkness cast by alien engineering on this scale.
With this level of technology we could even move stars around, albeit slowly. The simplest way would be to place a mirror on one side of the star to reflect some of its light into a beam, producing thrust in the opposite direction. Or the energy from a Dyson sphere could power ion engines to move the star a bit faster. We might use such a stellar engine to coast away from a predicted supernova, or to take two small dim stars and smash them together to make a brighter power plant.
If wrangling mere stars seems humdrum, how about harnessing the power of a supermassive black hole? We could catch the radiation from its accretion disk, or suck energy out of its spin. A spinning hole drags space-time around it in a region known as the ergosphere, which we could exploit in at least two ways. Roger Penrose of the University of Oxford has suggested using it to accelerate a stream of matter to high speeds, whereas University of Cambridge physicists Roger Blandford and Roman Znajek have devised a way to turn it into an electromagnetic dynamo. These could be the basis of a power plant a billion times as powerful as a Dyson sphere. It would have to be the size of our solar system, at least.
Even that might not be the limit of our ambition. Our quest to understand the cosmos (see “Can we understand everything?“) may lead us to build the ultimate particle accelerator, capable of reaching the immense energy where all forces are unified and the fundamental nature of space-time is finally revealed.
Brian Lacki at the Institute for Advanced Study in Princeton, New Jersey, has worked out some of the properties of this machine. One of them is immense size: to be able to boost particles to the required energies it would have to stretch at least a hundred times the distance from the sun to Pluto.
This is just a lower limit, but making it even bigger should be possible. Such a long, thin object can be extended indefinitely without producing overwhelming gravitational stress, so we might be able to build a tower out to Orion and beyond.
At the limits of imaginable technology, we might even end up tinkering with the fate of the cosmos. If our hunger for power isn’t satisfied by stars and supermassive black holes, then we might learn to create microscopic black holes and feed them with dust. This could unlock the mass-energy of inert matter, turning it into hot Hawking radiation that could be used to drive our interstellar industry.
According to calculations by S. Jay Olson of the University of Queensland in Australia, this could change the future of everything. With civilisation spreading through space at close to the speed of light, it would fill the cosmos with waste heat and so change its physical properties. The conversion of matter to radiation would even a little, which puts our petty meddling with Earth into perspective.
Read more: “The human universe: Exploring our place in space”
This article appeared in print under the headline “Can we engineer the universe?”
