At the heart of many a good science-fiction tale you will find space ships that can travel across the Galaxy. Could this ever happen?
Any space adventure that goes beyond the Moon or Mars inevitably trips up when it comes to the practicalities of travel. Quite often the most satisfactory explanations are those which don’t really mean anything. For ‘Star Trek’, dilithium crystals just did the job and without further examination we were motoring along at warp factor 2.
Recently at Big Screen we looked at ‘High Life’ and ‘IO’, both of which required interstellar travel although, in fairness, neither was looking too far beyond our galactic neighbours. In practice, travel to the nearest star (other than the Sun), Alpha Centauri cluster, within a single lifetime might remain beyond us unless there is a dramatic breakthrough in technology.
Even with the invention of a drive light powerful enough to propel matter to a significant percentage of the speed of light, travel would come with a serious health warning because even comparatively benign photons would be blue-shifted (decreased wavelength, increase in energy and increase in frequency) to lethality. It is hard to imagine any material being strong enough to protect the occupants.
One distant possibility is to borrow a sleight of hand from science fiction and, instead of making things travel faster, move the space around the ship. Is such a warp drive feasible? It is as long as some parts of physics turn out to be more than mathematical tricks. Quantum physics, for example, admits the possibility of negative probability. The lack of an intuitive explanation of how such probabilities work is just one reason why physicists tend to fall in with the Copenhagen interpretation (that quantum stalwart of ‘superposition’) and ‘just do the maths’, rather than attempt to build a colloquial rationale for what happens in the quantum world.
Quantum physicist Paul Dirac wrote in 1942: “Negative energies and probabilities should not be considered as nonsense. They are well-defined concepts mathematically, like a negative of money.”
A quarter of a century ago, Miguel Alcubierre, a scientist working at the National Autonomous University of Mexico (UNAM), picked up on the idea and speculated that negative energy could play a significant role in faster-than-light travel. Much more recently, the US Defense Intelligence Agency (DIA) declassified a decade-old document authored by a pair of consultants who described various theoretical ways faster-than-light drives might operate with a stronger focus than Alcubierre’s proposal on quantum-level phenomena, such as the Casimir effect. That effect is one that demonstrates negative energy, albeit on a much smaller scale than any starship would need.
To get any appreciable effect, the curvature of spacetime has to be dramatic: on the scale of a black hole’s event horizon. And the backside of the bubble needs to bend space dramatically the other way complete with effects that reverse those of gravity. However, if we assume that negative energy and a few other prerequisites do exist, the power of a drive that warps space is that it neatly works around the problem of trying to achieve anything close to lightspeed. It reworks spacetime to reduce the distance to the destination while pushing the bubble rapidly away from the origin. In doing so, no laws of relativity are harmed let alone broken.
The warp bubble does have problems and does not entirely dispense with the radiation problem. The strange behaviour of spacetime around the boundaries of the bubble would probably protect its occupants. But any energy in front of the craft would be blue-shifted to an extreme degree because of the collapsing spacetime and possibly trapped until the bubble dissipates. That could be dangerous in its own way. As the warp field collapses at the destination, the trapped high-energy photons are finally released into surrounding space in a calamitious explosion.
Even without such exotic means of transport, which are so theoretical that estimations of such practicalities as fuel or design are impossible, the costs involved for interstellar travel using existing technology would be insurmountable according to André Füzfa, astrophysicist and professor at the department of mathematics at the University of Namur. His research into the costs and practicalities of space travel unearthed the headline fact that a manned 100-tonne space mission to the closest star to Earth would cost about 15 times the annual world energy production. “It is often (naively?!) hoped that moving to other star systems will be our only escape if one day this planet becomes inhospitable,” says Füzfa. “But actually, developing interstellar travel might well precipitate the exhaust of our planet resources.”
The human race has a pretty good track record in innovation and so it would be foolish to claim it is never going to happen. However, whether judging the space-bending requirements of sci-fi space craft or the engineering limitations of the those we have now, it looks like mankind will have to settle for planet Earth as its home for the foreseeable future.
Source : IET
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