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Black Holes in the Lab

Scientists are keen on finding new ways to study those unfathomable objects - black holes. These could include artificial, laboratory-made black holes.

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Still a secret - black holes in space

As black holes are light years away, research - not to mention sustained observation - on these obscure objects is generally a matter for specialised satellites and space telescopes.

Today, scientists are aiming to create models of black holes for closer and easier research, using sound, light, or computers.

Creating a black hole if not on the top of the laboratory desk, but with the assistance of the laboratory’s desktop has now been achieved by a research team at Nasa’s Jet Propulsion Laboratory in California. In a joint effort with a group of scientists from Japan, the Californians "have modeled the general relativistic magnethydrodynamic behaviour of plasma flowing into a rapidly rotating black hole in large-scale magnetic field with numerical simulations". In other words, the team examined the streams of energy in and around black holes – for the first time on a computer-simulated black hole.

A centre of attraction

Black holes have been a centre of attraction to science ever since they were first predicted over half a century ago.

Physicists believe that black holes form when large stars collapse, producing points with a gravitational attraction so strong that nothing, not even light can escape their pull.

They are strange and fascinating objects, but as of yet, they are still considered theoretical – one of the reasons why astronomers and astrophysicists of all disciplines have turned their attentions towards the search for actual black holes in the vastness of space and further research on these obscure objects.

The search is a difficult one, because black holes cannot actually be seen, and must be detected indirectly. However, the discovery of actual black holes are essential to provide further proof of Einstein's General Theory of Relativity, which first predicted their existence over fifty years ago.

According to the theory of relativity, light slows and time comes to a standstill at the boundary of a black hole, the so-called event horizon. An event horizon is the theorized "one-way ticket" boundary around a black hole from which nothing, not even light, can escape. No object except for a black hole can have an event horizon, so evidence for its existence offers resounding proof of black holes in space.

However, scientists have also realised that black holes have, besides relativistic features, quantum-mechanical ones. This became clear when Stephan Hawking pointed out that black holes should not be black at all, but should glow.

Hawking’s theory has become vital in the attempt to bring the black hole to the laboratory.

Popping in and out

According to Heisenberg’s uncertainty principle in quantum mechanics, empty space is not entirely empty. Instead, pairs of particles and their antimatter equivalents are constantly popping in and out into existence. Black holes can tear these pairs apart by sucking in one of the two particles. Without its partner, the survivor cannot vanish into space again and, hanging around as it then does, becomes real, getting its energy from the black hole. According to Ulf Leonhardt from St. Andrews University in Scotland, this type of "Hawking radiation" is not restricted to outer space. It could be produced in a laboratory, too.

According to Leonhadt, light passing through super-cold materials called Bose-Einstein condensates ought to behave like black holes. Bose Einstein condensates are made of waves of particles which are cooled down to such an extent that they start to merge, forming a single object. With the help of lasers, scientists can make the transparency of the condensates so thick, that light has difficulties getting through, and can even be brought to a standstill.

As Bose Einstein condensates can be made in almost any well-equipped laboratory that has the apparatus necessary to cool things down to within a few zillionths of a degree of absolute zero, Leonhardt says that black holes could be brought to the laboratory table, too. In this week’s Nature, Leornhardt argues that the boundary where light eventually stops using the condensates is similar to the event horizon of a black hole, if the travelling light takes on a certain shape. And, if Hawking’s radiation theory is correct, pairs of particles of light should be generated on either side of the boundary, as they would at a black hole’s event horizon.

The difference to real black holes, however, is that those in outer space guzzle up practically everything, including light in all shapes and sizes.

Looking for proofs

Taking a closer look at new energy sources which derive from black hole spins was also the focus of a group of German and American astronomers based at Tübingen University in the past months. However, the group followed through with its research with the help of a satellite, in order to watch a galaxy 100 light years away. A black hole on the laboratory doorstep would have been a help.

If Leonhardt’s ideas were materialized in the near future, research on black holes would not be as unfathomable as they may seem. And it would be a vindication of Hawking’s theories of the universe, which have yet never been tested in outer space.