How to Build a Time Machine by Paul Davies

Author:Paul Davies
Language: eng
Format: epub, mobi
ISBN: 9780141930428
Publisher: Penguin Books Ltd
Published: 2008-11-19T16:00:00+00:00

The imploder

Although by human standards a quark-gluon plasma is highly energized, it is a long way from our present requirements. The enormous temperature of 10 trillion degrees inside the bubble is still about 19 powers of ten too low to affect the spacetime foam. To boost the temperature up to Planck values we need to compress the bubble by a factor of a billion billion. Surprisingly, the total energy involved to achieve this is very modest - about 10 billion joules, equivalent to the total output of a typical power station for only a few seconds. So energy is not a limiting factor at this step. The challenge is to concentrate that much energy into such a small object.

It's not clear how this might be done, but explosive magnetic pinching could offer a way. Magnetic fields are used to confine conventional low-energy plasmas, such as ionized gases. If the field is intensified, the plasma gets squeezed. Scientists began experimenting with this technique, known as the Z-pinch, in the early 1950s, as part of the programme to develop controlled nuclear fusion. An intense electric current is passed through deuterium gas in a chamber, rapidly ionizing it. The magnetic field of the current then violently pinches the resulting plasma and heats it to millions of degrees. The most refined Z-pinch system in current use is at the Sandia National Laboratories in New Mexico, where electrical pulses of 50 trillion watts from a bank of charged capacitors are concentrated onto ultra-thin tungsten wires.

The sort of compression needed to reach Planck temperatures demands far more punch than the Sandia system. A collection of thermonuclear bombs arranged in a spherical pattern centred on the target might be able to concentrate a magnetic field enough to implode the quark-gluon bubble. To repeat, the total energy required is not great; it merely needs to be directed at the target bubble rather than spewing into the surroundings. Assuming the concentration problem can be solved, the net effect will be to create a tiny ball with a density of about 10 trillion trillion trillion trillion trillion trillion trillion trillion kilograms per cubic metre, or some 80 powers of ten greater than the density of nuclear matter. This is enough to rival the vast energy fluctuations permitted at the Planck length: a billion-trillion-trillionth of a centimetre – the distance light will travel in a Planck time. Hopefully, the result would be to form either a minute black hole or a wormhole that would become the seed for growing the time machine.

To implement the compression, some serious problems of basic physics need to be addressed alongside the engineering challenges. Quantum field theory suggests that if a magnetic field gets too strong it may start to create subatomic particles and thereby dissipate itself. Also, magnetic pinching is notoriously unstable. These difficulties could possibly be circumvented by using another type of field altogether, such as the so-called Higgs field that is being sought eagerly by particle physicists.

Alternatively, an accelerator might be employed in place of an imploder.

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