Supercomputers are astonishing feats of engineering, boasting mind-blowing processing power and the ability to calculate the answer to life, the universe and everything. But to some they are supervillains rather than superheroes. For decades governments around the world funded supercomputers with military applications in mind, and some of the most powerful machines ever made were put to work modelling missile trajectories and simulating nuclear war.
Today's supercomputers still do some of that, but they're increasingly being used with the very best intentions: to model the effects of climate change, to find better ways of using energy, to investigate new materials, design new kinds of vehicles and to predict natural disasters.
Here we introduce you to the world's ten most powerful computers...
Tianhe-2 (Milky Way 2)
Reckon your quad-core PC is pretty powerful? The National Super Computer Center in Guangzhou, China, has a machine with a staggering 3,120,000 cores delivering 33.86 petaFLOPs. The machine was developed by China's National University of Defense Technology (NUDT) and as you might expect the defence side of things is shrouded in secrecy, but Chinese media reports say it'll also be used to predict earthquakes, for climate modelling and to help China's car industry. That latter claim has baffled many observers: automobile engineering professor Bian Mingyaun of Tsinghua University told the South China Morning Post that using a supercomputer to design cars was "like running after a chicken with an axe… quite unnecessary."
K Computer
Fujitsu's K Computer is another former number one: in 2011 it was the first computer to top 10 petaFLOPs. It's installed at the RIKEN Advanced Institute for Computational Science in Kobe, Japan, where it runs a variety of applications for tasks including disaster prevention, medical science and climate modelling. That requires a lot of power: at full pelt the K Computer uses the same amount of energy of nearly 10,000 suburban homes.
Titan
The former number one was built by Cray at the US Oak Ridge National Laboratory, and it boasts some 18,688 CPUs and the same number of GPUs. That gives it a theoretical peak of 27 petaFLOPs. Titan has been used to model combustion to make engines more efficient, to find ways of reducing nuclear waste, to model climate change and to improve materials science in semiconductors and plastics.
Mira
How's this for power: according to its creator IBM, if "every man, woman and child in the United States performed one calculation each second, it would take them almost a year to do as many calculations as Mira will do in one second." It's used by seismologists, chemists, materials scientists and climatologists.
Piz Daint
Named after a Swiss Alp , the Swiss National Computing Centre's Piz Daint supercomputer was upgraded in late 2013 to deliver 20 times more power than its predecessor while only using two and a half times as much energy. It's Europe's most powerful supercomputer, and scientists of all disciplines can gain access to it: there's an application scheme every six months, with an independent committee of specialists deciding which applications have the most merit.
Stampede
The Texas Advanced Computing Center (TACC) in Austin provides high performance computing to thousands of scientists and engineers every year. The 500,000lb Stampede supercomputer has been used to improve brain tumour imaging, to predict Californian earthquakes, to analyse language and music for patterns and to better understand the flow of ice from Antarctica.
JUQUEEN
IBM makes yet another appearance in the top ten with JUQUEEN, which is installed at the Forschungszentrum Jülich research institute in Germany. It has been designed to handle compute-intensive tasks for scientific areas including neuroscience, computational biology, climate research and quantum physics. One of its users, the Human Brain Project, hopes to simulate the entire human brain.
Vulcan
It's another mention for IBM: its Vulcan supercomputer, which is installed at the Lawrence Livermore National Laboratory in California. Vulcan is operated on behalf of the US National Nuclear Security Administration. Since 2013 it has also been available to scientists, engineers and academics in a wide range of sectors including energy, bioscience, atmospheric science and high performance computing technology.
Sequoia
IBM Sequoia became the world's fastest supercomputer in 2012, although it has since been pipped to the post - but it's still astonishingly powerful. While Sequoia has been used for scientific applications including astronomy, climate modelling and studying the human genome its main purpose is military: it was designed primarily for nuclear weapons simulation.
SuperMUC
SuperMUC may not be the fastest supercomputer in the world but at launch it was the fastest Intel-compatible system in the world. It's also one of the more energy efficient supercomputers: its unusual, IBM-developed "warm water cooling" reduces the number of cooling components necessary to stop it from getting hotter than the sun, saving millions of Euros in cooling costs.
SuperMUC is based in Garching, near Munich (MUC is Munich's airport code) and it's available "to all European researchers to expand the frontiers of science and engineering." So far it has been used for applications including computational fluid dynamics, genome analysis, earthquake simulation, computational chemistry and life sciences.