Wednesday, October 28, 2015

On colonising the observable universe quite quickly!

Stuart Armstrong and Anders Sandberg

Future of Humanity Institute, Philosophy Department, Oxford University, Suite 8, Littlegate House 16/17 St. Ebbe’s Street, Oxford, OX1 1PT UK.


"The Fermi paradox is the discrepancy between the strong likelihood of alien intelligent life emerging (under a wide variety of assumptions), and the absence of any visible evidence for such emergence. In this paper, we extend the Fermi paradox to not only life in this galaxy, but to other galaxies as well.

"We do this by demonstrating that traveling between galaxies – indeed even launching a colonisation project for the entire reachable universe – is a relatively simple task for a star-spanning civilization, requiring modest amounts of energy and resources.

"We start by demonstrating that humanity itself could likely accomplish such a colonisation project in the foreseeable future, should we want to, and then demonstrate that there are millions of galaxies that could have reached us by now, using similar methods. This results in a considerable sharpening of the Fermi paradox."
The authors have in mind the launching of replicators both to other stars in our own galaxy and to other galaxies. They note that once the interstellar/intergalactic probe is up to relativistic speed it basically turns off and cruises. In cosmological time it's rather irrelevant as to whether the cruise time is hundreds, thousands or millions of years (the universe operate on a timescale of billions of years).
"However, the main difference between interstellar and intergalactic travel is merely a longer time until the destination is reached. If the contents of the colonizing probe are inert over long timescales (as they would need to be for many forms of interstellar travel) it is likely that they can be made inert over the longer flights to other galaxies." (Page 3)
We could send lots of probes without too much effort assuming a technology a few hundred years in the future.
"... we will first delineate a potential replicator probe design, and tackle how such probes could decelerate upon arrival. We will see what speeds these probes could move at, and how many duplicates need to be sent out to avoid collisions with intergalactic dust particles.

"Then we will consider the launch system – due to the great inefficiency of the rocket equation, it would be much more effective to use fixed launch systems than to count on the probes to power themselves. We will analyse these launch systems, and delve into some details as to how they could be powered (four different scenarios will be considered, from speculative antimatter drives to reasonable fission engines).

"It will turn out that only about six hours of the sun’s energy is needed to commence the colonisation of the entire universe! And this is the kind of energy that a future human civilisation could quite easily aspire to, as we shall demonstrate." (page 4).
They propose we disassemble Mercury (they describe how to do it with mass drivers, and on page 16 calculate it will take 31 years and 85 days!) and use the material to create a Dyson Swarm of solar mirrors powering propulsion devices (lasers, particle beams, coilguns ...).

The probes will be accelerated by these power-plants to relativistic speeds at which point they will coast to their targets. Thousands, millions or billions of years later they will arrive, slow down and find asteroids or planets to start terraforming. The seeds they carry will germinate .. and our descendants will walk under the light of other stars .. in other galaxies.

They're careful to stay within the envelope of feasible, or exploratory engineering,

so why didn't aliens on some of the other relatively nearby galaxies get to us first? They show that there's plenty of candidate colonisers (of the order of a million galaxies) and plenty of time for it to have happened (page 25).

The Fermi Paradox just got sharper.

All in all, a very stimulating big-concept read. Here's a links to Anders Sandberg's blog.