In August, physicist Jia Liu at New York University outlined his design for a spacecraft powered by dark matter. Soon afterwards, mathematicians Louis Crane and Shawn Westmoreland at Kansas State University in Manhattan proposed plans for a craft powered by an artificial black hole.
- Take Liu's dark matter starship. Most astronomers are convinced of the existence of dark matter because of the way its gravity tugs on the stars and galaxies we see with our telescopes. Such observations suggest that dark matter outweighs the universe's visible matter by a factor of about six - so a dark matter starship could have a plentiful supply of fuel. Because dark matter is so abundant throughout the universe, Liu envisages a rocket that need not carry its own fuel. This immediately overcomes one of the drawbacks of many other proposed starships, whose huge fuel supply greatly adds to their weight and hampers their ability to accelerate. "A dark matter rocket would pick up its fuel en route," says Liu.
- His plan is to drive the rocket using the energy released when dark matter particles annihilate each other. Here's where Liu's idea depends on more speculative physics. No one knows what dark matter is actually made of, though there are numerous theories of the subatomic world that contain potential dark matter candidates. One of the frontrunners posits that dark matter is made of neutralinos, particles which have no electric charge. Neutralinos are curious in that they are their own antiparticles: two neutralinos colliding under the right circumstances will annihilate each other.
