A self-replicating machine is a type of
autonomous robot that is capable of
reproducing itself autonomously using
raw materials found in the environment,
thus exhibiting self-replication in a
way analogous to that found in nature.
The concept of self-replicating machines
has been advanced and examined by Homer
Jacobsen, Edward F. Moore, Freeman
Dyson, John von Neumann and in more
recent times by K. Eric Drexler in his
book on nanotechnology, Engines of
Creation and by Robert Freitas and Ralph
Merkle in their review Kinematic
Self-Replicating Machines which provided
the first comprehensive analysis of the
entire replicator design space. The
future development of such technology is
an integral part of several plans
involving the mining of moons and
asteroid belts for ore and other
materials, the creation of lunar
factories, and even the construction of
solar power satellites in space. The
possibly misnamed von Neumann probe is
one theoretical example of such a
machine. Von Neumann also worked on what
he called the universal constructor, a
self-replicating machine that would
operate in a cellular automata
environment.
A self-replicating machine is an
artificial self-replicating system that
relies on conventional large-scale
technology and automation. Certain
idiosyncratic terms are occasionally
found in the literature. For example,
the term "clanking replicator" was once
used by Drexler to distinguish
macroscale replicating systems from the
microscopic nanorobots or "assemblers"
that nanotechnology may make possible,
but the term is informal and is rarely
used by others in popular or technical
discussions. Replicators have also been
called "von Neumann machines" after John
von Neumann, who first rigorously
studied the idea. However, the term "von
Neumann machine" is less specific and
also refers to a completely unrelated
computer architecture that von Neumann
proposed and so its use is discouraged
where accuracy is important. Von Neumann
himself used the term universal
constructor to describe such
self-replicating machines.
Historians of machine tools, even before
the numerical control era, sometimes
figuratively said that machine tools
were a unique class of machines because
they have the ability to "reproduce
themselves" by copying all of their
parts. Implicit in these discussions is
that a human would direct the cutting
processes, and would then be assembling
the parts. The same is true for RepRaps,
which are another class of machines
sometimes mentioned in reference to such
non-autonomous "self-replication". In
contrast, machines that are truly
autonomously self-replicating are the
main subject discussed here.
History
The general concept of artificial
machines capable of producing copies of
themselves dates back at least several
hundred years. An early reference is an
anecdote regarding the philosopher René
Descartes, who suggested to Queen
Christina of Sweden that the human body
could be regarded as a machine; she
responded by pointing to a clock and
ordering "see to it that it reproduces
offspring." Several other variations on
this anecdotal response also exist.
Samuel Butler proposed in his 1872 novel
Erewhon that machines were already
capable of reproducing themselves but it
was man who made them do so, and added
that "machines which reproduce machinery
do not reproduce machines after their
own kind".
In 1802 William Paley formulated the
first known teleological argument
depicting machines producing other
machines, suggesting that the question
of who originally made a watch was
rendered moot if it were demonstrated
that the watch was able to manufacture a
copy of itself. Scientific study of
self-reproducing machines was
anticipated by John Bernal as early as
1929 and by mathematicians such as
Stephen Kleene who began developing
recursion theory in the 1930s. Much of
this latter work was motivated by
interest in information processing and
algorithms rather than physical
implementation of such a system,
however.
= von Neumann's kinematic model=
A detailed conceptual proposal for a
physical non-biological self-replicating
system was first put forward by
mathematician John von Neumann in
lectures delivered in 1948 and 1949,
when he proposed a kinematic
self-reproducing automaton model as a
thought experiment. Von Neumann's
concept of a physical self-replicating
machine was dealt with only abstractly,
with the hypothetical machine using a
"sea" or stockroom of spare parts as its
source of raw materials. The machine had
a program stored on a memory tape that
directed it to retrieve parts from this
"sea" using a manipulator, assemble them
into a duplicate of itself, and then
copy the contents of its memory tape
into the empty duplicate's. The machine
was envisioned as consisting of as few
as eight different types of components;
four logic elements that send and
receive stimuli and four mechanical
elements used to provide a structural
skeleton and mobility. While
qualitatively sound, von Neumann was
evidently dissatisfied with this model
of a self-replicating machine due to the
difficulty of analyzing it with
mathematical rigor. He went on to
instead develop an even more abstract
model self-replicator based on cellular
automata. His original kinematic concept
remained obscure until it was
popularized in a 1955 issue of
Scientific American.
= Moore's artificial living plants=
In 1956 mathematician Edward F. Moore
proposed the first known suggestion for
a practical real-world self-replicating
machine, also published in Scientific
American. Moore's "artificial living
plants" were proposed as machines able
to use air, water and soil as sources of
raw materials and to draw its energy
from sunlight via a solar battery or a
steam engine. He chose the seashore as
an initial habitat for such machines,
giving them easy access to the chemicals
in seawater, and suggested that later
generations of the machine could be
designed to float freely on the ocean's
surface as self-replicating factory
barges or to be placed in barren desert
terrain that was otherwise useless for
industrial purposes. The
self-replicators would be "harvested"
for their component parts, to be used by
humanity in other non-replicating
machines.
= Dyson's replicating systems=
The next major development of the
concept of self-replicating machines was
a series of thought experiments proposed
by physicist Freeman Dyson in his 1970
Vanuxem Lecture. He proposed three
large-scale applications of machine
replicators. First was to send a
self-replicating system to Saturn's moon
Enceladus, which in addition to
producing copies of itself would also be
programmed to manufacture and launch
solar sail-propelled cargo spacecraft.
These spacecraft would carry blocks of
Enceladean ice to Mars, where they would
be used to terraform the planet. His
second proposal was a solar-powered
factory system designed for a
terrestrial desert environment, and his
third was an "industrial development
kit" based on this replicator that could
be sold to developing countries to
provide them with as much industrial
capacity as desired. When Dyson revised
and reprinted his lecture in 1979 he
added proposals for a modified version
of Moore's seagoing artificial living
plants that was designed to distill and
store fresh water for human use and the
"Astrochicken."
= Advanced Automation for Space
Missions=
In 1980, inspired by a 1979 "New
Directions Workshop" held at Wood's
Hole, NASA conducted a joint summer
study with ASEE entitled Advanced
Automation for Space Missions to produce
a detailed proposal for self-replicating
factories to develop lunar resources
without requiring additional launches or
human workers on-site. The study was
conducted at Santa Clara University and
ran from June 23 to August 29, with the
final report published in 1982. The
proposed system would have been capable
of exponentially increasing productive
capacity and the design could be
modified to build self-replicating
probes to explore the galaxy.
The reference design included small
computer-controlled electric carts
running on rails inside the factory,
mobile "paving machines" that used large
parabolic mirrors to focus sunlight on
lunar regolith to melt and sinter it
into a hard surface suitable for
building on, and robotic front-end
loaders for strip mining. Raw lunar
regolith would be refined by a variety
of techniques, primarily hydrofluoric
acid leaching. Large transports with a
variety of manipulator arms and tools
were proposed as the constructors that
would put together new factories from
parts and assemblies produced by its
parent.
Power would be provided by a "canopy" of
solar cells supported on pillars. The
other machinery would be placed under
the canopy.
A "casting robot" would use sculpting
tools and templates to make plaster
molds. Plaster was selected because the
molds are easy to make, can make precise
parts with good surface finishes, and
the plaster can be easily recycled
afterward using an oven to bake the
water back out. The robot would then
cast most of the parts either from
nonconductive molten rock or purified
metals. A carbon dioxide laser cutting
and welding system was also included.
A more speculative, more complex
microchip fabricator was specified to
produce the computer and electronic
systems, but the designers also said
that it might prove practical to ship
the chips from Earth as if they were
"vitamins."
A 2004 study supported by NASA's
Institute for Advanced Concepts took
this idea further. Some experts are
beginning to consider self-replicating
machines for asteroid mining.
Much of the design study was concerned
with a simple, flexible chemical system
for processing the ores, and the
differences between the ratio of
elements needed by the replicator, and
the ratios available in lunar regolith.
The element that most limited the growth
rate was chlorine, needed to process
regolith for aluminium. Chlorine is very
rare in lunar regolith.
= Lackner-Wendt Auxon replicators=
In 1995, inspired by Dyson's 1970
suggestion of seeding uninhabited
deserts on Earth with self-replicating
machines for industrial development,
Klaus Lackner and Christopher Wendt
developed a more detailed outline for
such a system. They proposed a colony of
cooperating mobile robots 10–30 cm in
size running on a grid of electrified
ceramic tracks around stationary
manufacturing equipment and fields of
solar cells. Their proposal didn't
include a complete analysis of the
system's material requirements, but
described a novel method for extracting
the ten most common chemical elements
found in raw desert topsoil using a
high-temperature carbothermic process.
This proposal was popularized in
Discover Magazine, featuring
solar-powered desalination equipment
used to irrigate the desert in which the
system was based. They named their
machines "Auxons", from the Greek word
auxein which means "to grow."
Recent work
= Self-replicating rapid prototypers=
Early experimentation with rapid
prototyping in 1997-2000 was not
expressly oriented toward reproducing
rapid prototyping systems themselves,
but rather extended simulated
"evolutionary robotics" techniques into
the physical world. Later developments
in rapid prototyping have given the
process the ability to produce a wide
variety of electronic and mechanical
components, making this a rapidly
developing frontier in self-replicating
system research.
In 1998 Chris Phoenix informally
outlined a design for a hydraulically
powered replicator a few cubic feet in
volume that used ultraviolet light to
cure soft plastic feedstock and a
fluidic logic control system, but didn't
address most of the details of assembly
procedures, error rates, or machining
tolerances.
In 2005, Adrian Bowyer of the University
of Bath started the RepRap Project to
develop a rapid prototyping machine
which would be able to manufacture some
or most of its own components, making
such machines cheap enough for people to
buy and use in their homes. The project
is releasing its designs and control
programs under the GNU GPL. The RepRap
approach uses fused deposition modeling
to manufacture plastic components,
possibly incorporating conductive
pathways for circuitry. Other
components, such as steel rods, nuts and
bolts, motors and separate electronic
components, would be supplied
externally. In 2006 the project produced
a basic functional prototype and in May
2008 the machine succeeded in producing
all of the plastic parts required to
make a 'child' machine.
Some researchers have proposed a
microfactory of specialized machines
that support recursion—nearly all of the
parts of all of the machines in the
factory can be manufactured by the
factory.
= NIAC studies on self-replicating
systems=
In the spirit of the 1980 "Advanced
Automation for Space Missions" study,
the NASA Institute for Advanced Concepts
began several studies of
self-replicating system design in 2002
and 2003. Four phase I grants were
awarded:
Hod Lipson, "Autonomous Self-Extending
Machines for Accelerating Space
Exploration"
Gregory Chirikjian, "Architecture for
Unmanned Self-Replicating Lunar
Factories"
Paul Todd, "Robotic Lunar Ecopoiesis"
Tihamer Toth-Fejel, "Modeling Kinematic
Cellular Automata: An Approach to
Self-Replication" The study concluded
that complexity of the development was
equal to that of a Pentium 4, and
promoted a design based on cellular
automata.
= Cornell University's self-assembler=
In 2005, a team of researchers at
Cornell University, including Hod
Lipson, implemented a self-assembling
machine. The machine is composed of a
tower of four articulated cubes, known
as molecubes, which can revolve about a
triagonal. This enables the tower to
function as a robotic arm, collecting
nearby molecubes and assembling them
into a copy of itself. The arm is
directed by a computer program, which is
contained within each molecube,
analogous to how each animal cell
contains an entire copy of its DNA.
However, the machine cannot manufacture
individual molecubes, nor do they occur
naturally, so its status as a
self-replicator is debatable.
= New York University artificial DNA
tile motifs=
In 2011 a team of scientists at New York
University created a structure called
'BTX' based around three double helix
molecules, each made from a short strand
of DNA. Treating each group of three
double-helices as a code letter, they
can build up self-replicating structures
that encode large quantities of
information.
= Self-replication of magnetic polymers=
In 2001 Jarle Breivik at University of
Oslo created a system of magnetic
building blocks, which in response to
temperature fluctuations, spontaneously
form self-replicating polymers.
Partial construction
Partial construction is the concept that
the constructor creates a partially
constructed offspring, which is then
left to complete its own construction.
The von Neumann model of
self-replication envisages that the
mother automaton should construct all
portions of daughter automatons, without
exception and prior to the initiation of
such daughters. Partial construction
alters the construction relationship
between mother and daughter automatons,
such that the mother constructs but a
portion of the daughter, and upon
initiating this portion of the daughter,
thereafter retracts from imparting
further influence upon the daughter.
Instead, the daughter automaton is left
to complete its own development. This is
to say, means exist by which automatons
may develop via the mechanism of a
zygote.
Self-replicating spacecraft
The idea of an automated spacecraft
capable of constructing copies of itself
was first proposed in scientific
literature in 1974 by Michael A. Arbib,
but the concept had appeared earlier in
science fiction such as the 1967 novel
Berserker by Fred Saberhagen or the 1950
novellette trilogy The Voyage of the
Space Beagle by A. E. van Vogt. The
first quantitative engineering analysis
of a self-replicating spacecraft was
published in 1980 by Robert Freitas, in
which the non-replicating Project
Daedalus design was modified to include
all subsystems necessary for
self-replication. The design's strategy
was to use the probe to deliver a "seed"
factory with a mass of about 443 tons to
a distant site, have the seed factory
replicate many copies of itself there to
increase its total manufacturing
capacity, and then use the resulting
automated industrial complex to
construct more probes with a single seed
factory on board each.
Other references
A number of patents have been granted
for self-replicating machine concepts.
The most directly relevant include U.S.
Patent 4,734,856 "Autogeneric system"
Inventor: Davis; Dannie E., U.S. Patent
5,659,477 "Self reproducing fundamental
fabricating machines" Inventor: Collins;
Charles M., U.S. Patent 5,764,518 " Self
reproducing fundamental fabricating
machine system" Inventor: Collins;
Charles M.(June 1998); Collins' PCT: and
U.S. Patent 6,510,359 "Method and system
for self-replicating manufacturing
stations" Inventors: Merkle; Ralph C.,
Parker; Eric G., Skidmore; George D..
Macroscopic replicators are mentioned
briefly in the fourth chapter of K. Eric
Drexler's 1986 book Engines of Creation.
In 1995, Nick Szabo proposed a challenge
to build a macroscale replicator from
Lego robot kits and similar basic parts.
Szabo wrote that this approach was
easier than previous proposals for
macroscale replicators, but successfully
predicted that even this method would
not lead to a macroscale replicator
within ten years.
In 2004, Robert Freitas and Ralph Merkle
published the first comprehensive review
of the field of self-replication, in
their book Kinematic Self-Replicating
Machines, which includes 3000+
literature references. This book
included a new molecular assembler
design, a primer on the mathematics of
replication, and the first comprehensive
analysis of the entire replicator design
space.
Fictional self-replicating machines in
literature
Many types of self-replicating machines
have been featured in literature, and
particularly in science fiction.
= Other Notable Works Containing
Replicators=
Science fiction is full of engaging
stories containing replicators:
2010: Odyssey Two by Arthur C. Clarke
The Adolescence of P-1 by Thomas J. Ryan
is another early fictional accounts of a
computer virus or worm.
The Berserkers from the Berserker series
of sci-fi novels and short stories by
Fred Saberhagen
Cold as Ice and The Ganymede Club by
Charles Sheffield
The Diamond Age by Neal Stephenson,
which depicts a near-future Earth
society wherein nanotechnology,
including self-replicators, both exist
and influence daily life greatly.
Evolution by Stephen Baxter
The Festival, a civilisation of uploaded
minds with strange designs on Humanity,
from Singularity Sky by Charles Stross
The Killers, a civilization of of
self-replicating machines designed to
destroy any potential threat to their
creators, from The Forge of God by Greg
Bear
"The Necessary Thing" by Robert
Sheckley, in which the Universal
Replicator is unwittingly tricked into
replicating itself
Recursion by Tony Ballantyne ISBN
0-330-42699-0
The Shockwave Rider by John Brunner is
an early example of a fictional account
of a computer virus or worm.
Spin by Robert Charles Wilson
When HARLIE Was One a novel by David
Gerrold and in a short story that was
published in Galaxy in 1969, a computer
learns to randomly dial phone numbers
until it hits a telephone modem that is
answered by another computer. It then
programs the answering computer to begin
dialing random numbers in search of yet
another computer. The "infection,"
postulated long before existence of the
internet, is assumed to spread
exponentially through susceptible
computers, like a biological infection.
This was the first account of a
self-replicating computer program - a
virus or worm.
The World at the End of Time by Frederik
Pohl
The Xymos Nanoswarms from Prey by
Michael Crichton
Fictional self-replicating machines in
movies
Many types of self-replicating machines
have been featured in the movies.
= Screamers=
The movie Screamers, based on Dick's
short story Second Variety, features a
group of robot weapons created by
mankind to act as Von Neumann devices /
berserkers. The original robots are
subterranean buzzsaws that make a
screaming sound as they approach a
potential victim beneath the soil. These
machines are self-replicating and, as is
found out through the course of the
movie, they are quite intelligent and
have managed to "evolve" into newer,
more dangerous forms, most notably human
forms which the real humans in the movie
cannot tell apart from other real humans
except by trial and error.
= The Terminator=
The Terminator is a 1984 science
fiction/action film directed and
co-written by James Cameron which
describes a war between mankind and self
replicating machines led by a central
artificial intelligence known as Skynet.
Machine civilizations are a recurring
theme in fiction.
Fictional Self-replicating Machines on
Television
The concept is also widely utilised in
science fiction television.
= Lexx=
The TV series Lexx featured an army of
self replicating robots known as Mantrid
drones.
= Stargate SG-1=
Additionally, the Replicators are a
horde of self-replicating machines that
appear frequently in Stargate SG-1.
During the course of the series, the
replicators assume a human form and pose
a huge threat to the galaxy. A more
sophisticated version of the human form
Replicators, who call themselves Asurans
also appear in the spin-off series
Stargate Atlantis.
= Star Trek=
Star Trek's Borg.
= Nanites=
"Nanites" could also be considered
self-replicating machines.
Prospects for implementation
As the use of industrial automation has
expanded over time, some factories have
begun to approach a semblance of
self-sufficiency that is suggestive of
self-replicating machines. However, such
factories are unlikely to achieve "full
closure" until the cost and flexibility
of automated machinery comes close to
that of human labour and the manufacture
of spare parts and other components
locally becomes more economical than
transporting them from elsewhere. As
Samuel Butler has pointed out in
Erewhon, replication of partially closed
universal machine tool factories is
already possible. Since safety is a
primary goal of all legislative
consideration of regulation of such
development, future development efforts
may be limited to systems which lack
either control, matter, or energy
closure. Fully capable machine
replicators are most useful for
developing resources in dangerous
environments which are not easily
reached by existing transportation
systems.
An artificial replicator can be
considered to be a form of artificial
life. Depending on its design, it might
be subject to evolution over an extended
period of time. However, with robust
error correction, and the possibility of
external intervention, the common
science fiction scenario of robotic life
run amok will remain extremely unlikely
for the foreseeable future.
See also
AI takeover
3D Printing
Computer virus
Conway's Game of Life
Ecophagy
Existential risk from advanced
artificial intelligence
Grey goo
Lights out
Nanorobotics
Spiegelman Monster
References
Bibliography
Colvin, Fred H., Sixty Years with Men
and Machines, New York and London:
McGraw-Hill, LCCN 47003762 . Available
as a reprint from Lindsay Publications.
Foreword by Ralph Flanders.
External links
Video of Adrian Bowyer talking about
RepRap at the Pop!Tech 2007 Conference.
The Clanking Replicator Project:
Bootstrap your own self-replicating,
rapid prototyping machine
Cornell's Self-replicating machine
The RepRap Project: Creating wealth
without money...
Terraforming Mars and Venus using
machine self-replicating systems
Green Goo - Life In The Era Of Humane
Genocide by Nick Szabo
