A team of physicists in the UK are planning experiments to create artificial ‘black holes’ in a laboratory environment that will be able to suck in light or sound waves. The researchers hope that the black holes will provide important information about the fundamental behaviour of matter and energy.
Professor Ulf Leonhardt and his team at the University of St Andrews in Scotland are developing the foundations for the experiments.
Black holes are formed when stars collapse in on themselves. They consequently have an extremely high gravitational pull due to their hugely concentrated mass. To escape from a black hole, matter or energy would need to travel faster than light – something that is not possible. ‘This makes a black hole a perfect trap,’ said Professor Leonhardt.
‘We believe we may be able to create an experimental system using moving fluids in which it is possible to suck in either light waves or sound waves, similar to a black hole,’ said Professor Leonhardt. If sound or light waves are introduced into the a fluid that is moving faster than the waves, then it may be possible to trap the waves, creating in effect a small black hole.
‘A useful analogy is of fish swimming in a stream that is approaching a waterfall,’ explained Professor Leonhardt. ‘The flow of the stream increases the closer it gets to the waterfall. A point is reached where the flow of the stream is faster that the speed at which the fish can swim. The fish become trapped in the flow and can move only in one direction – they have no chance of escape’
The ideal scenario is to reduce the speed of the waves. ‘If you take a vapour of certain types of atom at very low temperatures and pass laser light into it, the vapour’s properties can become altered. If a second laser light is then shone into the vapour, this light propagates extremely slowly – a matter of only tens of centimetres a second.’
This phenomenon, called electromagnetically induced transparency, has been studied closely at St Andrews. ‘If the vapour can then be made to flow at a rate faster than the velocity of the light waves travelling within it, you then have a situation similar to the fish in the stream,’ said Professor Leonhardt. ‘The light could effectively become trapped.’
Another possible method could involve a small cloud of atoms being held in a doughnut configuration by a laser beam with a hollow cylindrical section.
It is possible to accelerate the atoms at one point in the ring of vapour, and at ultra-low temperatures sound waves can be passed into the system. The speed of sound in these conditions is said to be very low, less than that of the moving vapour. This could be a way of creating a ‘sonic black hole’.
‘The aim of these experiments would be to study the quantum properties of light or sound in these artificial black holes,’ said Professor Leonhardt. ‘The observations from such experiments could help to resolve some of the conflict between general relativity and quantum theory.’