John Von Neumann And Self Replicating Machines
Scientists and engineers since the 1940s have been toying with the idea of building self-replicating machines, or von Neumann machines, named for John von Neumann.
With recent advances in 3D printing (including in zero gravity) and machine learning AI, it seems like self-replicating machines are much more feasible today. In the 21st century, a tantalising possibility for this technology has emerged: sending a space probe out to a different star system, having it mine resources to make a copy of itself, and then launching that one to yet another star system, and on and on and on.
If we could send a von Neumann probe to another star system—likely Alpha Centauri, the closest to us at about 4.4 light years away—then that autonomous spaceship could land on a rocky planet, asteroid, or moon and start building a factory.
That factory of autonomous machines could then construct solar panels, strip mine the world for resources, extract fuels from planetary atmospheres, build smaller probes to explore the system, and eventually build a copy of the entire von Neumann spacecraft to send off to a new star system and repeat the process. It has even been suggested that such self-replicating machines could build a Dyson sphere to harness energy from a star or terraform a planet for the eventual arrival of humans.1
A look at the concept of Self-Replicating Machines, Universal Assemblers, Von Neumann Probes, Grey Goo, and Berserkers. While Isaac will discuss the basic concept and some on-Earth applications like Medical Nanotechnology the focus will be on space exploration and colonisation aspects.
Who Was John Von Neumann?
In 1945, mathematician John von Neumann undertook a study of computation that demonstrated that a computer could have a simple, fixed structure, yet be able to execute any kind of computation given properly programmed control without the need for hardware modification.
Von Neumann contributed a new understanding of how practical fast computers should be organised and built; these ideas, often referred to as the stored-program technique, became fundamental for future generations of high-speed digital computers and were universally adopted.
The primary advance was the provision of a special type of machine instruction called conditional control transfer–which permitted the program sequence to be interrupted and reinitiated at any point, similar to the system suggested by Babbage for his analytical engine–and by storing all instruction programs together with data in the same memory unit, so that, when desired, instructions could be arithmetically modified in the same way as data. Thus, data was the same as program.
The von Neumann architecture is a design model for a stored-program digital computer that uses a processing unit and a single separate storage structure to hold both instructions and data. It is named after the mathematician and early computer scientist John von Neumann. Such computers implement a universal Turing machine and have a sequential architecture. The terms “von Neumann architecture” and “stored-program computer” are generally used interchangeably.2
What is a Von Neumann Probe?
Simply put, a Von Neumann probe is a self-replicating device that could, one day, be used to explore every facet of the Milky Way in a relatively small window of time.
The general idea is to build a device out of materials that are readily available and easily accessible out in space, like on rocky planets or small moons. Once it finds a suitable destination, it lands and mines the material it needs to build even more devices, which, in turn, land on other planets and moons and build even more.
The system is very effective, and by some estimates, it would take around half a million years to dispatch millions of probes across our galaxy, assuming each one travels at approximately 1/10th the speed of light, or 18,640 miles (30,000 km) per second (though the real number could be closer to ten million years, which is still no time at all in the grand scheme of things).3
Can We Build Von Neumann Machines?
In order to work, a von Neumann spacecraft would have to tap into advanced nanotechnology and artificial intelligence — technologies that advanced extraterrestrial civilisations are likely to develop. In fact, the device itself would be a molecular assembler, capable of reconstituting matter into copies of itself, which is why SRPs are also referred to as kinematic self-replicating machines.
And indeed, these probes would be remarkably efficient. A recent study published in the International Journal of Astronomy pointed out that extraterrestrial intelligences (ETIs) could use the slingshot effect to propel SRPs from star to star. And yes, that’s the same method used to propel the Voyager spacecrafts through our solar system from planet to planet. For it to work on a galactic scale, however, Self Replicating Probes would use slingshot maneuvers around stars, gaining a boost in velocity by extracting energy from each star’s motion around the galactic centre.
The slingshot effect would carry little-to-no extra cost and result in a 100-fold increase in efficiency; models show that this technique could be used to send probes to every solar system in the galaxy in as little as 10 million years! Adding to the efficiency is the realisation that SRPs could replicate on the fly, building duplicates of themselves while they’re traveling. The probes would collect matter, like dust and gas, from the interstellar medium as they traverse vast distances. 4
Nano Bots, Nanotechnology and Grey Goo
It seems like most science fiction stories have one of two aims: Thrill us with the possibility of an amazing future or frighten the pants off of us with a doomsday scenario. The gray goo nightmare falls squarely into the second category. But is it just science fiction?
The term refers to a disaster scenario in nanotechnology applications. Nanotechnology is the science of manipulating matter on a molecular scale. The discipline includes the goal of building devices on this scale, possibly capable of manipulating individual molecules or even atoms.
An engineer and futurist by the name of Kim Eric Drexler proposed an intriguing possibility for nanotechnology in his book “Engines of Creation.” Drexler envisioned a future in which tiny machines called assemblers could build materials molecule-by-molecule. Using billions of these assemblers, you could manufacture practically any material you could imagine. The assemblers would put the molecules together in just the right way to produce what you needed.
How do you get so many assemblers? First you build a few in the lab. Then you set the assemblers to build other assemblers. These new assemblers will begin building more machines in turn. The manufacturing rate becomes exponential, doubling with each generation.
But what happens if the production gets out of control? That would lead to the gray goo scenario. Assemblers would begin to convert all organic matter into more assemblers, consuming everything in the process. The Earth would be reduced to a lifeless mass teeming with nanomachines. 5
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