The Antikythera mechanism is often considered the oldest computer, and it was used for astronomical calculations. This mysterious object is dated to about the end of the 2nd century BC. The device predates the next known clockwork mechanism by almost a thousand years. The astrolabe, invented in the same time period, was a more primitive instrument, but was essentially a computing device for solving astronomical problems. Astronomical calculations for navigation was the driving force behind many of the early mechanical computers.
In 1642, Pascal designed the mechanical calculator known as the Pascaline. The machine could be used to add and subtract numbers. Leibniz’s stepped reckoner improved on this version, and added the functionality for multiplication and division directly, instead of repeatedly performing an operation. Charles Babbage made a number of advanced computers including the Difference Engine to calculate polynomials and the Analytical Engine, which was a general purpose computer. The Analytical Engine could be programmed through punch cards then used for looms, had a memory storage unit, and an arithmetic unit.
Some of the mechanical computers used in wartime were actually superior to electronic alternatives. They were more accurate, and the calculations were done in real time, instead of the clock cycles. The mechanical computers used to target moving ships, were actually more reliable than electronic versions. One of these, the Mark 1A, Fire Control Computer computed the angles at which the ships should fire their guns, the velocities of the projectiles, and their time of flight, factoring in wind, gravity and parallax. However, due to space constraints, the military eventually embraced electronic computers.
For most of human history, we have actually been using mechanical computers. Now mechanical computers can be both analog and digital. Modern computers are electronic digital computers. Think of the difference in this way, a mechanical analog clock has moving hands that can display the time, even if the numerals are not imprinted on the face. A mechanical digital clock would display the actual numbers on a cylinder moved by gears.
While electronic digital computers might have become ubiquitous now, mechanical computers are making a comeback. The approach combines nanotechnology and the design principles of the earliest mechanical computers, such as the Difference Engine. This is because on a nanoscale, mechanical motion is very rapid, and are a low cost option to existing microprocessors. These nanomechanical computers can be integrated with appliances and toys – things that need computation, but do not need to do it very quickly. These nanomechanical computers actually have several advantages over electronic computers – they are resilient to electric shocks, can operate at much higher temperatures, and are more energy efficient.
There are some extreme environments that are just hostile to semiconductor based computers. One of these environments is the surface of Venus. Venus has an atmospheric pressure of 90 atm, which is 90 times that of the Earth. The amount of pressure is enough to crush most submarines. The surface temperature 462°C, hot enough to melt lead alloys. This is where the reliable and old school mechanical computers come to the rescue. NASA is planning to send a clockwork rover to Venus. The rover would navigate using tank like treads, powered by turbines within the body of the rover. The rover can use morse code for communicating with a satellite in orbit. A rotating sheath over a bright radar target can repeatedly cover and uncover the target to send signals to the orbiting satellite. Engineers working on the rover are figuring out a way to integrate a drill as well.
Redstone dust is a kind of material in Minecraft that can be used to make virtual computers. Redstone can be laid out in lines to make wires. Players can also craft redstone clocks and rails. Typical computers built within Minecraft consist of redstone, redstone torches and redstone repeaters. The redstone torches have an on or off state, and the repeaters can amplify, delay or block signals. Redstone pistons are used for the on and off state of binary. Combined with a number of buttons and levers, elaborate computing devices can be made within the game. The amount of time spent into creating computers is staggering, and a includes ALU, CPU, memory, input and output devices.
Once the community figured out that redstone could be used to make computers, the creations got increasingly elaborate. Creations included a scientific calculator, a word processor, and even a working version of the Commodore 32. Users went on to create programmable computers, and a hard disk drive that could actually store 1KB of memory. Many of the more elaborate creations included MP3 players and had their own AI for games such as tic-tac-toe. Hans Lemurson made a 2D version of Minecraft, within Minecraft. Players can move around, and create or destroy blocks. A 2012 update introduced command blocks, that interacted with redstone, and allowed the computers to be significantly miniaturised. This enabled another player, Craftronics, to create a working version of the iPhone. It had a keyboard, a working weather app, and you actually had to enter a passcode to access the device. The build used 2572 command blocks, and over 200 hours to create. Computing is a terribly slow process within the virtual Minecraft computers, though there are plugins to accelerate how fast the game plays out.
Chapter 17, titled Newton, Von Neumann, the First Emperor, and Tri-Solar Syzygy in Cixin Liu’s award winning sci-fi book, The Three Body problem has a spectacular description of a computer. The basic units are soldiers who perform simple operations, raising black or white flags to form AND, XOR, NOR, XNAND and XNOR gates. The hardware consists of thirty million soldiers, arranged in an area of six square kilometers. The NOT gate is simply a soldier who raises the opposite coloured flag, when another soldier raises a particular flag. There is a CPU, registers, memory, a hard drive and even an expandable bus system. The software is an operating system on a scroll. There is even a display unit with a progress bar made up of a series of green flags. Although the computer does not work exactly as expected, it is a brilliant demonstration of how complex machines can be built out of very simple components – where people are the “simple” components.
Researchers at Japan’s Kobe university used crabs to build a computer. They used soldier crabs from Australia, which behave very predictably in swarms. The gates, or the most basic components of the computer, were mazes through which the crabs were made to navigate. Depending on how many swarms were introduced into the legs, the crab swarms would move consistently through the maze. An inverted Y shaped maze was used as an OR gate, and an X shaped maze with an extra arm on one side was used as an AND gate. The remaining gates could be made by combining these two gates together. No crabs were harmed during the experiment, and the researchers went to the extent of using cork for building the maze so that it was “comfortable for crab’s friction”.
German and British researchers have created logic components from slime mould. The species, known as Physarum polycephalum, forms networks of tubes to absorb and transport nutrients. The mould aggregates around food particles, but avoids salt. By combining the salt and oat flakes, structures similar to circuits seen in computers could be formed. Using dyes made up of magnetic nanoparticles, XOR and NOR gates were constructed. A series of these gates can potentially be chained up to build complex computers. The same species has also demonstrated its capabilities to form efficient distribution networks, at par with human engineers. British and Japanese researchers placed oat flakes in a map that corresponded to Tokyo and the surrounding cities. The mould grew outwards from the center, and formed a network that was similar to the actual Tokyo train network, in terms of reliability, cost and efficiency. A practical application is that the mould can help humans build more robust computer and mobile communication networks.