Self-Replicating Robots Might Take Over the World

"Grey goo" is a hypothetical end-of-the-world scenario involving molecular nanotechnology in which out-of-control self-replicating robots consume all matter on Earth while building more of themselves. This scenario is known as "ecophagy" -- the literal consuming of an ecosystem. The term "grey goo" is usually used in a science fiction context. In the worst postulated scenarios, matter beyond Earth would also be turned into goo, a large mass of replicating nanomachines. The disaster is posited to result from a deliberate doomsday device, or from an accidental mutation in a self-replicating nanomachine used only for other purposes, but designed to operate in a natural environment.


A simple form of self-replicating machine (Credit: NASA)

Self-replicating machines were originally described by mathematician John von Neumann. They are artificial constructs capable of autonomously manufacturing copies of themselves using raw materials taken from their environment. The concept of self-replicating machines has been advanced and examined by Edward F. Moore, Homer Jacobsen, Freeman Dyson, and in more recent times by K. Eric Drexler. The future development of such technology has featured as 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. Von Neumann also worked on what he called the universal constructor, a self-replicating machine that would operate in a cellular automata environment.

Ecophagy is a term coined by Robert Freitas. He used the term to describe a scenario involving molecular nanotechnology gone awry. In this situation out-of-control self-replicating nanorobots consume entire ecosystems, resulting in global ecophagy. However, the word "ecophagy" is now applied more generally in reference to any event -- nuclear war, the spread of monoculture, massive species extinctions -- that might fundamentally alter the planet. These events might result in ecocide in that they would undermine the capacity of the earth's biological population to repair itself. Some scientists suggest that more mundane and less spectacular events -- the unrelenting growth of the human population, the steady transformation of the natural world by human beings -- will eventually result in a planet that is considerably less vibrant, and one that is, apart from humans, essentially lifeless.

In his original paper Freitas wrote:

Perhaps the earliest-recognized and best-known danger of molecular nanotechnology is the risk that self-replicating nanorobots capable of functioning autonomously in the natural environment could quickly convert that natural environment (e.g., "biomass") into replicas of themselves (e.g., "nanomass") on a global basis, a scenario usually referred to as the "grey goo problem" but perhaps more properly termed "global ecophagy".

As the use of industrial automation has advanced over time, some factories have begun to approach a semblance of self-sufficiency that is suggestive of self-replicating machines. 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 -- such as outer space. 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.

World's Most Expensive Engineering Projects

Here is a list of the world's most expensive engineering projects with estimated costs and short descriptions of each project (sources: iCivilEngineer, China Daily, Wikipedia). Some of the projects are already completed, some are under construction, so the cost estimates are not definitive. This list is also under construction: if you know big engineering projects which are not listed, please post your comments.


5. Gerald R. Ford Class Aircraft Carrier: 8.1 billion USD
Artist’s concept of CVN 21 one of a new class of aircraft carriers

The Gerald R. Ford-class aircraft carriers (CVN-78) will be the next generation supercarrier for the United States Navy. Construction began in the spring of 2007, and is planned to finish in 2015. With the addition of the most modern equipment and automation they will reduce the crew requirement and the total cost of future aircraft carriers.

Carriers of the Ford class will incorporate many new design features: new nuclear reactor design, stealthier features to reduce radar profile, electromagnetic catapults, advanced arresting gear, and reduced crewing requirements. It will be constructed at Northrop Grumman Shipbuilding in Virginia, the only shipyard in the U.S. capable of building nuclear powered aircraft carriers. It is estimated to cost at least $8.1 billion excluding the $5 billion spent on research and development. A total of three carriers has been authorized for construction, but eleven carriers could be constructed over the life of the program.

4. Big Dig, Boston: 14.6 billion USD
Interstate I-93 Tunnel in Boston, part of the Big Dig; photography by Rene Schwietzke

The Big Dig is a megaproject that rerouted the Central Artery, the chief highway through the heart of Boston, into a 3.5 mile tunnel under the city. When the project concluded on December 31, 2007, it was the most expensive highway project in the U.S. The project incurred criminal arrests, escalating costs, death, leaks, and charges of poor execution and use of substandard materials.

This project was developed in response to traffic congestion on Boston's streets, which were laid out before the advent of the automobile. The project faced several environmental and engineering obstacles. The area through which the tunnels were to be dug was largely landfill, and included existing subway lines, pipes and utility lines, many unexpected geological barriers, glacial debris, foundations of buried houses, sunken ships, etc. Unusual engineering challenges required unusual solutions and methods to address them. Engineers figured out the safest way to build the tunnel without endangering the existing highway above.

By the January 13, 2006, Big Dig was completed. It remains the largest and most complex highway and tunnel project in the nation's history.

3. Three Gorges Dam, China: 24 billion USD
Three Gorges Dam in construction 2002; photography by Frank Matthes

The Three Gorges Dam is a hydroelectric river dam that spans the Yangtze River in Sandouping, China. This is the largest hydroelectric power station in the world. The original plan of the project was completed in 2008. Six additional generators in the underground power plant will be installed until around 2011, when total electric generating capacity of the dam will reach 22,500 MW.

Some interesting facts: the concrete dam wall is 2,309 meters long, 101 meters high, 115 meters thick on the bottom and 40 meters thick on top. The project used 27,200,000 cubic meters of concrete, 463,000 tonnes of steel (enough to build 63 Eiffel Towers), and moved about 102,600,000 cubic meters of earth. When the water level is maximum at 91 meters above river level, the reservoir created by the Three Gorges Dam is about 660 kilometers in length and 1.12 kilometers in width on average. The total surface area of the reservoir is 1045 km2. The reservoir will flood a total area of 632 km2 of land.

The dam provides a vast amount of clean electricity, controls flooding, and enhances navigation. However, it has also flooded cultural and archaeological sites, displaced more than million people, and is causing dramatic ecological changes. The decision to build the dam has been deeply controversial.

2. Yucca Mountain Nuclear Waste Repository Project: 57 billion USD
Looking west atop Yucca Mountain towards Beatty and Death Valley

The U.S. Department of Energy have been studying Yucca Mountain, Nevada, since 1978 to determine whether it would be suitable for a long-term geologic repository for high-level radioactive waste, a result of nuclear power generation and national defense programs. Yucca Mountain is located in a remote desert within the secure boundaries of the Nevada Test Site in Nye County, 90 miles northwest of Las Vegas.

Yucca Mountain was created by several large eruptions from a caldera volcano and is composed of layers of tuff. Tuff has special physical and chemical characteristics that make it a suitable material to entomb radioactive waste for the hundreds of thousands of years required for the waste to become safe through radioactive decay. After 20 years of research and carefully planned scientific field work, the Department of Energy has found that the repository brings together the location and natural barriers most likely to protect the safety of the public, including those Americans living in the immediate vicinity.

The Obama Administration rejected the use of the site in the 2009 United States Federal Budget proposal, which would eliminate all funding except that needed to answer inquiries from the Nuclear Regulatory Commission, while the Administration devises a new strategy toward nuclear waste disposal. On March 5, 2009, Energy Secretary told a Senate hearing that the Yucca Mountain site no longer was viewed as an option for storing reactor waste.

1. International Space Station: 80 billion USD
International Space Station as seen from the departing Space Shuttle Atlantis; source: NASA

The International Space Station (ISS) is a joint project among the space agencies of the United States (NASA), Japan (JAXA), Russia (RKA), Canada (CSA) and the European Space Agency. The space station is in a low Earth orbit, at an altitude of 350 km, and you can see it from Earth's surface even with the naked eye.

The International Space Station is the largest research laboratory ever launched into orbit. Long-term expedition crews conduct science across a variety of fields: life sciences, human research, Earth observation, physical sciences, education and technology demonstrations. Scientific findings are being published every month. ISS provides educational opportunities for students back home on Earth, including educational demonstrations, student-developed experiments, student participation in ISS experiments, ISS engineering activities, and NASA investigator experiments.

As a multinational project, the financial and legal aspects of the ISS are complex. Giving a precise cost estimate is not straightforward, because it is not easy to determine which costs should actually be attributed to the programme. Cost estimates range from 35 billion to 100 billion USD. The ESA estimates €100 billion for the entire station over a period of 30 years.